Journal articles: 'HIV gag protein p17'

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Wong, S. B. Justin, and Robert F. Siliciano. "Contribution of Virus-Like Particles to the Immunogenicity of Human Immunodeficiency Virus Type 1 Gag-Derived Vaccines in Mice." Journal of Virology 79, no. 3 (February 1, 2005): 1701–12. http://dx.doi.org/10.1128/jvi.79.3.1701-1712.2005.

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ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Gag protein is a major target antigen for cytotoxic-T-lymphocyte-based vaccine strategies because of its high level of conservation. The murine model has been used extensively to evaluate potential HIV-1 vaccines. However, the biology of HIV-1 Gag is somewhat different in human and murine tissues. The ability of HIV-1 Gag to form virus-like particles (VLPs) in human cells is severely curtailed in murine cells. Hence, it is not known whether immunizing mice with expression vectors encoding HIV-1 Gag provides an accurate assessment of the immunogenicity of these candidate vaccines in primates. In this report, we made use of a chimeric Moloney murine leukemia virus (MMLV)-HIV-1 Gag in which the p17 matrix domain of HIV-1 was replaced with the p15 matrix and p12 domains from MMLV. Murine cells expressing this construct released significant amounts of VLPs. The construct preserved H-2 d -restricted antigenic determinants in the remaining portion of HIV-1 Gag, allowing immunogenicity studies to be performed with mice. We demonstrated that immunizing mice with plasmid DNA or adenoviral vectors encoding this chimeric Gag did not significantly increase the HIV-1 Gag-specific cellular or humoral immune response when compared to immunization with a myristoylation-incompetent version of the construct. Thus, the release of VLPs formed in vivo may not play a major role in the immunogenicity of vectors expressing HIV-1 Gag constructs.

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Koup, R. A., C. A. Pikora, K. Luzuriaga, D. B. Brettler, E. S. Day, G. P. Mazzara, and J. L. Sullivan. "Limiting dilution analysis of cytotoxic T lymphocytes to human immunodeficiency virus gag antigens in infected persons: in vitro quantitation of effector cell populations with p17 and p24 specificities." Journal of Experimental Medicine 174, no. 6 (December 1, 1991): 1593–600. http://dx.doi.org/10.1084/jem.174.6.1593.

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The presence of cytotoxic T lymphocytes (CTL) to the gag antigens of human immunodeficiency virus (HIV) has been described in infected populations. We found that the majority of this immune response as measured in bulk CTL assays of unstimulated peripheral blood mononuclear cells (PBMC) is directed against the p24 component of the p55 gag precursor protein. Using limiting dilution analysis of this effector cell population we confirm that the majority of activated gag-specific CTL circulating in the PBMC of infected hemophilic patients are directed at p24 determinants and are present at frequencies of 1/36,000 to 1/86,000 lymphocytes. By performing in vitro stimulation after limiting dilution, the precursor population of gag-specific CTL are characterized and quantitated. HIV gag-specific CTL precursors are identified at frequencies of 1/1700 to 1/17,000 lymphocytes and are made up of cells with both p17 and p24 specificities. No HIV gag-specific CTL precursor cells are identified in the PBMC of HIV-uninfected individuals. These studies demonstrate that CTL directed at both p17 and p24 determinants make up the cellular immune repertoire in HIV-infected individuals but that only the p24-specific CTL are routinely found in an activated state in the circulation.

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Eugen-Olsen, J. "Effect of HIV gag p17 protein on normal T cells." Immunology Letters 56, no. 1-3 (May 1997): 135. http://dx.doi.org/10.1016/s0165-2478(97)87377-4.

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Hofmann, B., P. Nishanian, J. Fan, T. Nguyen, and J. L. Fahey. "HIV Gag p17 protein impairs proliferation of normal lymphocytes in vitro." AIDS 8, no. 7 (July 1994): 1016. http://dx.doi.org/10.1097/00002030-199407000-00025.

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Carroll, Virginia A., Mark K. Lafferty, Luigi Marchionni, Joseph L. Bryant, Robert C. Gallo, and Alfredo Garzino-Demo. "Expression of HIV-1 matrix protein p17 and association with B-cell lymphoma in HIV-1 transgenic mice." Proceedings of the National Academy of Sciences 113, no. 46 (October 31, 2016): 13168–73. http://dx.doi.org/10.1073/pnas.1615258113.

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HIV-1 infection is associated with increased risk for B-cell lymphomas. How HIV infection promotes the development of lymphoma is unclear, but it may involve chronic B-cell activation, inflammation, and/or impaired immunity, possibly leading to a loss of control of oncogenic viruses and reduced tumor immunosurveillance. We hypothesized that HIV structural proteins may contribute to lymphomagenesis directly, because they can persist long term in lymph nodes in the absence of viral replication. The HIV-1 transgenic mouse Tg26 carries a noninfectious HIV-1 provirus lacking part of the gag-pol region, thus constituting a model for studying the effects of viral products in pathogenesis. Approximately 15% of Tg26 mice spontaneously develop leukemia/lymphoma. We investigated which viral proteins are associated with the development of leukemia/lymphoma in the Tg26 mouse model, and performed microarray analysis on RNA from spleen and lymph nodes to identify potential mechanisms of lymphomagenesis. Of the viral proteins examined, only expression of HIV-1 matrix protein p17 was associated with leukemia/lymphoma development and was highly expressed in bone marrow before disease. The tumor cells resembled pro-B cells, and were CD19+IgM−IgD−CD93+CD43+CD21−CD23−VpreB+CXCR4+. Consistent with the pro-B-cell stage of B-cell development, microarray analysis revealed enrichment of transcripts, including Rag1, Rag2, CD93, Vpreb1, Vpreb3, and Igll1. We confirmed RAG1 expression in Tg26 tumors, and hypothesized that HIV-1 matrix protein p17 may directly induce RAG1 in B cells. Stimulation of human activated B cells with p17 enhanced RAG1 expression in three of seven donors, suggesting that intracellular signaling by p17 may lead to genomic instability and transformation.

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Binley, James M., Xia Jin, Yaoxing Huang, Linqi Zhang, Yunzhen Cao, David D. Ho, and John P. Moore. "Persistent Antibody Responses but Declining Cytotoxic T-Lymphocyte Responses to Multiple Human Immunodeficiency Virus Type 1 Antigens in a Long-Term Nonprogressing Individual with a Defective p17 Proviral Sequence and No Detectable Viral RNA Expression." Journal of Virology 72, no. 4 (April 1, 1998): 3472–74. http://dx.doi.org/10.1128/jvi.72.4.3472-3474.1998.

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ABSTRACT Long-term nonprogressor AD-18 has been infected with human immunodeficiency virus type 1 (HIV-1) for at least 16 years. During the past 5 years, he has had undetectable levels of plasma viremia, and HIV-1 cannot be isolated from him. Sequencing of proviral DNA indicates that the only HIV-1 sequences that can be identified in AD-18 have gross defects in the p17-encoding regions of the gag gene (Y. Huang, L. Zhang, and D. D. Ho, Virology 240:36–49, 1998). However, AD-18 has strong, sustained antibody responses to several HIV-1 antigens, including p17. Cytotoxic T-lymphocyte responses to Env and Gag antigens have gradually diminished over the past 4 years, at a time when the titers of antibodies to the same proteins have remained stable. We discuss what these observations might mean for the generation and maintenance of immunological memory.

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Hantson, Anke, Valery Fikkert, Barbara Van Remoortel, Chistophe Pannecouque, Peter Cherepanov, Barry Matthews, George Holan, et al. "Mutations in Both env and gag genes are required for HIV-1 resistance to the polysulfonic dendrimer SPL2923, as corroborated by chimeric virus technology." Antiviral Chemistry and Chemotherapy 16, no. 4 (August 2005): 253–66. http://dx.doi.org/10.1177/095632020501600405.

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A drug-resistant NL4.3.SPL2923 strain has previously been generated by in vitro selection of HIV-1(NL4.3) in the presence of the polysulfonic dendrimer SPL2923 and mutations were reported in its gp120 gene (Witvrouw et al., 2000). Here, we further analysed the (cross) resistance profile of NL4.3/SPL2923. NL4.3.SPL2923 was found to contain additional mutations in gp41 and showed reduced susceptibility to SPL2923, dextran sulfate (DS) and enfuvirtide. To delineate to what extent the mutations in each env gene were accountable for the phenotypic (cross) resistance of NL4.3.SPL2923, the gp120-, gp41- and gp160-sequences derived from this strain were placed into a wild-type background using env chimeric virus technology (CVT). The cross resistance of NL4.3.SPL2923 towards DS was fully reproduced following gp160recombination, while it was only partially reproduced following gp120- or gp41-recombination. The mutations in gp41 of NL4.3/SPL2923 were sufficient to reproduce the cross resistance to enfuvirtide. Unexpectedly, the reduced sensitivity towards SPL2923 was not fully reproduced after gp160-recombination. The search for mutations in NL4.3.SPL2923 in viral genes other than env revealed several mutations in the gene encoding the HIV p17 matrix protein (MA) and one mutation in the gene encoding the p24 capsid protein (CA). In order to analyse the impact of the gag mutations alone and in combination with the mutations in env on the phenotypic resistance towards SPL2923, we developed a novel p17- and p17.gp160-CVT. Phenotypic analysis of the NL4.3.SPL2923 p17- and p17.gp160-recombined strains indicated that the mutations in both env and gag have to be present to fully reproduce the resistance of NL4.3.SPL2923 towards SPL2923.

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Eugen-Olsen, Jesper, Uffe Koppelhus, Lars Andresen, Jens O. Nielsen, and Bo Hofmann. "A recombinant HIV gag P17 protein suppresses the function of normal T cells." Biochemical Society Transactions 25, no. 2 (May 1, 1997): 220S. http://dx.doi.org/10.1042/bst025220s.

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Tamiya, Sadahiro, Sek Mardy, Mark F. Kavlick, Kazuhisa Yoshimura, and Hiroaki Mistuya. "Amino Acid Insertions near Gag Cleavage Sites Restore the Otherwise Compromised Replication of Human Immunodeficiency Virus Type 1 Variants Resistant to Protease Inhibitors." Journal of Virology 78, no. 21 (November 1, 2004): 12030–40. http://dx.doi.org/10.1128/jvi.78.21.12030-12040.2004.

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ABSTRACT A variety of amino acid substitutions in the protease and Gag proteins have been reported to contribute to the development of human immunodeficiency virus type 1 (HIV-1) resistance to protease inhibitors. In the present study, full-length molecular infectious HIV-1 clones were generated by using HIV-1 variants isolated from heavily drug-experienced and therapy-failed AIDS patients. Of six full-length infectious clones generated, four were found to have unique insertions (TGNS, SQVN, AQQA, SRPE, APP, and/or PTAPPA) near the p17/p24 and p1/p6 Gag cleavage sites, in addition to the known resistance-related multiple amino acid substitutions within the protease. The addition of such Gag inserts mostly compromised the replication of wild-type HIV-1, whereas the primary multidrug-resistant HIV infectious clones containing inserts replicated significantly better than those modified to lack the inserts. Western blot analyses revealed that the processing of Gag proteins by wild-type protease was impaired by the presence of the inserts, whereas that by mutant protease was substantially improved. The present study represents the first report clearly demonstrating that the inserts seen in the proximity of the Gag cleavage sites in highly multi-PI resistant HIV-1 variants restore the otherwise compromised enzymatic activity of mutant protease, enabling the multi-PI-resistant HIV-1 variants to remain replication competent.

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Mwau, Matilu, Inese Cebere, Julian Sutton, Priscilla Chikoti, Nicola Winstone, Edmund G. T. Wee, Tara Beattie, et al. "A human immunodeficiency virus 1 (HIV-1) clade A vaccine in clinical trials: stimulation of HIV-specific T-cell responses by DNA and recombinant modified vaccinia virus Ankara (MVA) vaccines in humans." Journal of General Virology 85, no. 4 (April 1, 2004): 911–19. http://dx.doi.org/10.1099/vir.0.19701-0.

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The immunogenicities of candidate DNA- and modified vaccinia virus Ankara (MVA)-vectored human immunodeficiency virus (HIV) vaccines were evaluated on their own and in a prime–boost regimen in phase I clinical trials in healthy uninfected individuals in the United Kingdom. Given the current lack of approaches capable of inducing broad HIV-neutralizing antibodies, the pTHr.HIVA DNA and MVA.HIVA vaccines focus solely on the induction of cell-mediated immunity. The vaccines expressed a common immunogen, HIVA, which consists of consensus HIV-1 clade A Gag p24/p17 proteins fused to a string of clade A-derived epitopes recognized by cytotoxic T lymphocytes (CTLs). Volunteers' fresh peripheral blood mononuclear cells were tested for HIV-specific responses in a validated gamma interferon enzyme-linked immunospot (ELISPOT) assay using four overlapping peptide pools across the Gag domain and three pools of known CTL epitopes present in all of the HIVA protein. Both the DNA and the MVA vaccines alone and in a DNA prime–MVA boost combination were safe and induced HIV-specific responses in 14 out of 18, seven out of eight and eight out of nine volunteers, respectively. These results are very encouraging and justify further vaccine development.

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Yusim, Karina, Can Kesmir, Brian Gaschen, Marylyn M. Addo, Marcus Altfeld, Søren Brunak, Alexandre Chigaev, Vincent Detours, and Bette T. Korber. "Clustering Patterns of Cytotoxic T-Lymphocyte Epitopes in Human Immunodeficiency Virus Type 1 (HIV-1) Proteins Reveal Imprints of Immune Evasion on HIV-1 Global Variation." Journal of Virology 76, no. 17 (September 1, 2002): 8757–68. http://dx.doi.org/10.1128/jvi.76.17.8757-8768.2002.

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ABSTRACT The human cytotoxic T-lymphocyte (CTL) response to human immunodeficiency virus type 1 (HIV-1) has been intensely studied, and hundreds of CTL epitopes have been experimentally defined, published, and compiled in the HIV Molecular Immunology Database. Maps of CTL epitopes on HIV-1 protein sequences reveal that defined epitopes tend to cluster. Here we integrate the global sequence and immunology databases to systematically explore the relationship between HIV-1 amino acid sequences and CTL epitope distributions. CTL responses to five HIV-1 proteins, Gag p17, Gag p24, reverse transcriptase (RT), Env, and Nef, have been particularly well characterized in the literature to date. Through comparing CTL epitope distributions in these five proteins to global protein sequence alignments, we identified distinct characteristics of HIV amino acid sequences that correlate with CTL epitope localization. First, experimentally defined HIV CTL epitopes are concentrated in relatively conserved regions. Second, the highly variable regions that lack epitopes bear cumulative evidence of past immune escape that may make them relatively refractive to CTLs: a paucity of predicted proteasome processing sites and an enrichment for amino acids that do not serve as C-terminal anchor residues. Finally, CTL epitopes are more highly concentrated in alpha-helical regions of proteins. Based on amino acid sequence characteristics, in a blinded fashion, we predicted regions in HIV regulatory and accessory proteins that would be likely to contain CTL epitopes; these predictions were then validated by comparison to new sets of experimentally defined epitopes in HIV-1 Rev, Tat, Vif, and Vpr.

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Nguyen, Dzung H., and James E. K. Hildreth. "Evidence for Budding of Human Immunodeficiency Virus Type 1 Selectively from Glycolipid-Enriched Membrane Lipid Rafts." Journal of Virology 74, no. 7 (April 1, 2000): 3264–72. http://dx.doi.org/10.1128/jvi.74.7.3264-3272.2000.

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ABSTRACT A number of recent studies have demonstrated the significance of detergent-insoluble, glycolipid-enriched membrane domains or lipid rafts, especially in regard to activation and signaling in T lymphocytes. These domains can be viewed as floating rafts composed of sphingolipids and cholesterol which sequester glycosylphosphatidylinositol (GPI)-linked proteins, such as Thy-1 and CD59. CD45, a 200-kDa transmembrane phosphatase protein, is excluded from these domains. We have found that human immunodeficiency virus type 1 (HIV-1) particles produced by infected T-cell lines acquire the GPI-linked proteins Thy-1 and CD59, as well as the ganglioside GM1, which is known to partition preferentially into lipid rafts. In contrast, despite its high expression on the cell surface, CD45 was poorly incorporated into virus particles. Confocal fluorescence microscopy revealed that HIV-1 proteins colocalized with Thy-1, CD59, GM1, and a lipid raft-specific fluorescent lipid, DiIC16(3), in uropods of infected Jurkat cells. CD45 did not colocalize with HIV-1 proteins and was excluded from uropods. Dot immunoassay of Triton X-100-extracted membrane fractions revealed that HIV-1 p17 matrix protein and gp41 were present in the detergent-resistant fractions and that [3H]myristic acid-labeled HIV Gag showed a nine-to-one enrichment in lipid rafts. We propose a model for the budding of HIV virions through lipid rafts whereby host cell cholesterol, sphingolipids, and GPI-linked proteins within these domains are incorporated into the viral envelope, perhaps as a result of preferential sorting of HIV Gag to lipid rafts.

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Hamano, Takaichi, Kazuhiro Matsuo, Yurina Hibi, Ann Florence B. Victoriano, Naoko Takahashi, Yosio Mabuchi, Tsuyoshi Soji, et al. "A Single-Nucleotide Synonymous Mutation in the gag Gene Controlling Human Immunodeficiency Virus Type 1 Virion Production." Journal of Virology 81, no. 3 (November 22, 2006): 1528–33. http://dx.doi.org/10.1128/jvi.01596-06.

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ABSTRACT Viral factors as well as host ones play major roles in the disease progression of human immunodeficiency virus type 1 (HIV-1) infection. We have examined cytotoxic T-lymphocyte activity and HIV-1 DNA PCR results of 312 high-risk seronegative drug users in northern Thailand and identified four seronegative cases positive for both assays. Furthermore, we have identified a synonymous mutation in nucleotide position 75 of the gag p17 gene (A426G) of HIV-1 that belongs to the CRF01_AE virus circulating in Thailand. The replication-competent HIV-1 clone containing the A426G mutation demonstrated a dramatic reduction of virion production and perturbation of viral morphogenesis without affecting viral protein synthesis in cells.

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Wright, Jaclyn K., Zabrina L. Brumme, Jonathan M. Carlson, David Heckerman, Carl M. Kadie, Chanson J. Brumme, Bingxia Wang, et al. "Gag-Protease-Mediated Replication Capacity in HIV-1 Subtype C Chronic Infection: Associations with HLA Type and Clinical Parameters." Journal of Virology 84, no. 20 (August 11, 2010): 10820–31. http://dx.doi.org/10.1128/jvi.01084-10.

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ABSTRACT The mechanisms underlying HIV-1 control by protective HLA class I alleles are not fully understood and could involve selection of escape mutations in functionally important Gag epitopes resulting in fitness costs. This study was undertaken to investigate, at the population level, the impact of HLA-mediated immune pressure in Gag on viral fitness and its influence on HIV-1 pathogenesis. Replication capacities of 406 recombinant viruses encoding plasma-derived Gag-protease from patients chronically infected with HIV-1 subtype C were assayed in an HIV-1-inducible green fluorescent protein reporter cell line. Viral replication capacities varied significantly with respect to the specific HLA-B alleles expressed by the patient, and protective HLA-B alleles, most notably HLA-B*81, were associated with lower replication capacities. HLA-associated mutations at low-entropy sites, especially the HLA-B*81-associated 186S mutation in the TL9 epitope, were associated with lower replication capacities. Most mutations linked to alterations in replication capacity in the conserved p24 region decreased replication capacity, while most in the highly variable p17 region increased replication capacity. Replication capacity also correlated positively with baseline viral load and negatively with baseline CD4 count but did not correlate with the subsequent rate of CD4 decline. In conclusion, there is evidence that protective HLA alleles, in particular HLA-B*81, significantly influence Gag-protease function by driving sequence changes in Gag and that conserved regions of Gag should be included in a vaccine aiming to drive HIV-1 toward a less fit state. However, the long-term clinical benefit of immune-driven fitness costs is uncertain given the lack of correlation with longitudinal markers of disease progression.

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Sakalian, Michael, Stephanie S. Dittmer, A. Dustin Gandy, Nathan D. Rapp, Aleš Zábranský, and Eric Hunter. "The Mason-Pfizer Monkey Virus Internal Scaffold Domain Enables In Vitro Assembly of Human Immunodeficiency Virus Type 1 Gag." Journal of Virology 76, no. 21 (November 1, 2002): 10811–20. http://dx.doi.org/10.1128/jvi.76.21.10811-10820.2002.

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ABSTRACT The Mason-Pfizer monkey virus (M-PMV) Gag protein possesses the ability to assemble into an immature capsid when synthesized in a reticulocyte lysate translation system. In contrast, the human immunodeficiency virus (HIV) Gag protein is incapable of assembly in parallel assays. To enable the assembly of HIV Gag, we have combined or inserted regions of M-PMV Gag into HIV Gag. By both biochemical and morphological criteria, several of these chimeric Gag molecules are capable of assembly into immature capsid-like structures in this in vitro system. Chimeric species containing large regions of M-PMV Gag fused to HIV Gag sequences failed to assemble, while species consisting of only the M-PMV p12 region, and its internal scaffold domain (ISD), fused to HIV Gag were capable of assembly, albeit at reduced kinetics compared to M-PMV Gag. The ability of the ISD to induce assembly of HIV Gag, which normally assembles at the plasma membrane, suggests a common requirement for a concentrating factor in retrovirus assembly. Despite the dramatic effect of the ISD on chimera assembly, the function of HIV Gag domains in that process was found to remain essential, since an assembly-defective mutant of HIV CA, M185A, abolished assembly when introduced into the chimera. This continued requirement for HIV Gag domain function in the assembly of chimeric molecules will allow this in vitro system to be used for the analysis of potential inhibitors of HIV immature particle assembly.

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Pollet, D. E., E. L. Saman, D. C. Peeters, H. M. Warmenbol, L. M. Heyndrickx, C. J. Wouters, G. Beelaert, G. van der Groen, and H. Van Heuverswyn. "Confirmation and differentiation of antibodies to human immunodeficiency virus 1 and 2 with a strip-based assay including recombinant antigens and synthetic peptides." Clinical Chemistry 37, no. 10 (October 1, 1991): 1700–1707. http://dx.doi.org/10.1093/clinchem/37.10.1700.

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Abstract We evaluated the use of the INNO-LIA HIV-1/HIV-2 Ab test (LIA HIV; Innogenetics) for the confirmation of antibodies to human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2). The test includes three recombinant HIV-1 proteins: p24 (gag), p17 (gag), and endonuclease (p31; pol), in combination with two synthetic peptides derived from the env gene of HIV-1 and one synthetic peptide selected from the env gene of HIV-2. Analysis of 450 sera from blood donors, 220 sera from patients with non-HIV pathology, and 28 Western blot (WB) p24-only reactive sera revealed no false-positive results, and the rate of indeterminate results was substantially lower than that with WB. Testing of 334 WB-confirmed HIV antibody-positive sera (309 HIV-1; 25 HIV-2) revealed no false-negative results. In two of seven seroconversion panels tested, LIA HIV detected the presence of HIV antibodies before WB did. In the other five panels, LIA HIV and WB confirmed the presence of HIV antibodies in the same sample. The LIA HIV assay therefore appears well suited for routine confirmation of the presence of HIV-1 and HIV-2 antibodies.

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Durali, Deniz, Jacques Morvan, Franck Letourneur, Doris Schmitt, Nelly Guegan, Marc Dalod, Sentob Saragosti, Didier Sicard, Jean-Paul Levy, and Elisabeth Gomard. "Cross-Reactions between the Cytotoxic T-Lymphocyte Responses of Human Immunodeficiency Virus-Infected African and European Patients." Journal of Virology 72, no. 5 (May 1, 1998): 3547–53. http://dx.doi.org/10.1128/jvi.72.5.3547-3553.1998.

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ABSTRACT The great variability of protein sequences from human immunodeficiency virus (HIV) type 1 (HIV-1) isolates represents a major obstacle to the development of an effective vaccine against this virus. The surface protein (Env), which is the predominant target of neutralizing antibodies, is particularly variable. Here we examine the impact of variability among different HIV-1 subtypes (clades) on cytotoxic T-lymphocyte (CTL) activities, the other major component of the antiviral immune response. CTLs are produced not only against Env but also against other structural proteins, as well as some regulatory proteins. The genetic subtypes of HIV-1 were determined for Env and Gag from several patients infected either in France or in Africa. The cross-reactivities of the CTLs were tested with target cells expressing selected proteins from HIV-1 isolates of clade A or B or from HIV type 2 isolates. All African patients were infected with viruses belonging to clade A for Env and for Gag, except for one patient who was infected with a clade A Env-clade G Gag recombinant virus. All patients infected in France were infected with clade B viruses. The CTL responses obtained from all the African and all the French individuals tested showed frequent cross-reactions with proteins of the heterologous clade. Epitopes conserved between the viruses of clades A and B appeared especially frequent in Gag p24, Gag p18, integrase, and the central region of Nef. Cross-reactivity also existed among Gag epitopes of clades A, B, and G, as shown by the results for the patient infected with the clade A Env-clade G Gag recombinant virus. These results show that CTLs raised against viral antigens from different clades are able to cross-react, emphasizing the possibility of obtaining cross-immunizations for this part of the immune response in vaccinated individuals.

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KIRKLEY, J. E., A. L. GOLDSTEIN, and P. H. NAYLOR. "Adjuvant Properties of Montanide CSA 720 with a Recombinant HIV P17 gag Protein and Synthetic Peptide Antigens." Scandinavian Journal of Immunology 43, no. 4 (April 1996): 431–38. http://dx.doi.org/10.1046/j.1365-3083.1996.d01-60.x.

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Saito, Atsushi, Motoko Morimoto, Takeshi Ohara, Akihisa Takamizawa, Atsuo Nakata, and Hideo Shinagawa. "Overproduction, Purification, and Diagnostic Use of the Recombinant HIV-1 Gag Proteins, the Precursor Protein p55 and the Processed Products p17, p24, and p15." Microbiology and Immunology 39, no. 7 (July 1995): 473–83. http://dx.doi.org/10.1111/j.1348-0421.1995.tb02231.x.

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Schur, Florian K. M., Robert A. Dick, Wim J. H. Hagen, Volker M. Vogt, and John A. G. Briggs. "The Structure of Immature Virus-Like Rous Sarcoma Virus Gag Particles Reveals a Structural Role for the p10 Domain in Assembly." Journal of Virology 89, no. 20 (July 29, 2015): 10294–302. http://dx.doi.org/10.1128/jvi.01502-15.

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ABSTRACTThe polyprotein Gag is the primary structural component of retroviruses. Gag consists of independently folded domains connected by flexible linkers. Interactions between the conserved capsid (CA) domains of Gag mediate formation of hexameric protein lattices that drive assembly of immature virus particles. Proteolytic cleavage of Gag by the viral protease (PR) is required for maturation of retroviruses from an immature form into an infectious form. Within the assembled Gag lattices of HIV-1 and Mason-Pfizer monkey virus (M-PMV), the C-terminal domain of CA adopts similar quaternary arrangements, while the N-terminal domain of CA is packed in very different manners. Here, we have used cryo-electron tomography and subtomogram averaging to studyin vitro-assembled, immature virus-like Rous sarcoma virus (RSV) Gag particles and have determined the structure of CA and the surrounding regions to a resolution of ∼8 Å. We found that the C-terminal domain of RSV CA is arranged similarly to HIV-1 and M-PMV, whereas the N-terminal domain of CA adopts a novel arrangement in which the upstream p10 domain folds back into the CA lattice. In this position the cleavage site between CA and p10 appears to be inaccessible to PR. Below CA, an extended density is consistent with the presence of a six-helix bundle formed by the spacer-peptide region. We have also assessed the affect of lattice assembly on proteolytic processing by exogenous PR. The cleavage between p10 and CA is indeed inhibited in the assembled lattice, a finding consistent with structural regulation of proteolytic maturation.IMPORTANCERetroviruses first assemble into immature virus particles, requiring interactions between Gag proteins that form a protein layer under the viral membrane. Subsequently, Gag is cleaved by the viral protease enzyme into separate domains, leading to rearrangement of the virus into its infectious form. It is important to understand how Gag is arranged within immature retroviruses, in order to understand how virus assembly occurs, and how maturation takes place. We used the techniques cryo-electron tomography and subtomogram averaging to obtain a detailed structural picture of the CA domains in immature assembled Rous sarcoma virus Gag particles. We found that part of Gag next to CA, called p10, folds back and interacts with CA when Gag assembles. This arrangement is different from that seen in HIV-1 and Mason-Pfizer monkey virus, illustrating further structural diversity of retroviral structures. The structure provides new information on how the virus assembles and undergoes maturation.

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Haglund, Karl, Ingrid Leiner, Kristen Kerksiek, Linda Buonocore, Eric Pamer, and John K. Rose. "Robust Recall and Long-Term Memory T-Cell Responses Induced by Prime-Boost Regimens with Heterologous Live Viral Vectors Expressing Human Immunodeficiency Virus Type 1 Gag and Env Proteins." Journal of Virology 76, no. 15 (August 1, 2002): 7506–17. http://dx.doi.org/10.1128/jvi.76.15.7506-7517.2002.

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ABSTRACT We investigated long-term memory and recall cellular immune responses to human immunodeficiency virus type 1 (HIV-1) Env and Gag proteins elicited by recombinant vesicular stomatitis viruses (VSVs) expressing Env and Gag. More than 7 months after a single vaccination with VSV-Env, ∼6% of CD8+ splenocytes stained with major histocompatibility complex class I tetramers containing the Env p18-I10 immunodominant peptide and showed a memory phenotype (CD44Hi). The level of tetramer-positive cells in memory was about 14% of the peak primary response. Recall responses elicited in these mice 5 days after boosting with a heterologous recombinant vaccinia virus expressing HIV-1 Env showed that 40 to 45% of CD8+ splenocytes were tetramer positive and activated (CD62LLo), and these cells produced gamma interferon after stimulation with Env peptide, indicating that they were functional. Five months after the boost, the long-term memory cell population (tetramer positive, CD44Hi) constituted 30% of the CD8+ splenocytes. Recall responses to HIV-1 Gag were examined in mice primed with VSV recombinants expressing HIV-1 Gag protein and boosted with a vaccinia virus recombinant expressing Gag. Using this protocol, we found that ∼40% of CD8+ splenocytes were activated (CD62LLo) and specific for a Gag immunodominant peptide (tetramer positive). The high-level Gag recall response elicited by the vaccinia virus-Gag was greater than that obtained by boosting with a VSV-Gag vector with a different VSV glycoprotein. The corresponding levels of CD44Hi memory cells were also higher long after boosting with vaccinia virus-Gag than after boosting with a glycoprotein exchange VSV-Gag. Our results show that VSV vectors elicit high-level memory CTL responses and that these can be amplified as much as six- to sevenfold using a heterologous boosting vector.

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Kiernan, Rosemary E., and Eric O. Freed. "Cleavage of the Murine Leukemia Virus Transmembrane Env Protein by Human Immunodeficiency Virus Type 1 Protease: Transdominant Inhibition by Matrix Mutations." Journal of Virology 72, no. 12 (December 1, 1998): 9621–27. http://dx.doi.org/10.1128/jvi.72.12.9621-9627.1998.

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ABSTRACT We have identified mutations in the human immunodeficiency virus type 1 (HIV-1) matrix protein (MA) which block infectivity of virions pseudotyped with murine leukemia virus (MuLV) envelope (Env) glycoproteins without affecting infectivity conferred by HIV-1 Env or vesicular stomatitis virus G glycoproteins. This inhibition is very potent and displays a strong transdominant effect; infectivity is reduced more than 100-fold when wild-type and mutant molecular clones are cotransfected at a 1:1 ratio. This phenomenon is observed with both ecotropic and amphotropic MuLV Env. The MA mutations do not affect the incorporation of MuLV Env into virions. We demonstrate that in HIV-1 virions pseudotyped with MuLV Env, the HIV-1 protease (PR) efficiently catalyzes the cleavage of the p15(E) transmembrane (TM) protein to p12(E). Immunoprecipitation analysis of pseudotyped virions reveals that the mutant MA blocks this HIV-1 PR-mediated cleavage of MuLV TM. Furthermore, the transdominant inhibition exerted by the mutant MA on wild-type infectivity correlates with the relative level of p15(E) cleavage. Consistent with the hypothesis that abrogation of infectivity imposed by the mutant MA is due to inhibition of p15(E) cleavage, mutant virions are significantly more infectious when pseudotyped with a truncated p12(E) form of MuLV Env. These results indicate that HIV-1 Gag sequences can influence the viral PR-mediated processing of the MuLV TM Env protein p15(E). These findings have implications for the development of HIV-1-based retroviral vectors pseudotyped with MuLV Env, since p15(E) cleavage is essential for activating membrane fusion and virus infectivity.

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Saha, Agniva, Jessica A. Mitchell, Yuri Nishida, Jonathan E. Hildreth, Joshua A. Ariberre, Wendy V. Gilbert, and David J. Garfinkel. "Atrans-Dominant Form of Gag Restricts Ty1 Retrotransposition and Mediates Copy Number Control." Journal of Virology 89, no. 7 (January 21, 2015): 3922–38. http://dx.doi.org/10.1128/jvi.03060-14.

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ABSTRACTSaccharomyces cerevisiaeandSaccharomyces paradoxuslack the conserved RNA interference pathway and utilize a novel form of copy number control (CNC) to inhibit Ty1 retrotransposition. Although noncoding transcripts have been implicated in CNC, here we present evidence that a truncated form of the Gag capsid protein (p22) or its processed form (p18) is necessary and sufficient for CNC and likely encoded by Ty1 internal transcripts. Coexpression of p22/p18 and Ty1 decreases mobility more than 30,000-fold. p22/p18 cofractionates with Ty1 virus-like particles (VLPs) and affects VLP yield, protein composition, and morphology. Although p22/p18 and Gag colocalize in the cytoplasm, p22/p18 disrupts sites used for VLP assembly. GlutathioneS-transferase (GST) affinity pulldowns also suggest that p18 and Gag interact. Therefore, this intrinsic Gag-like restriction factor confers CNC by interfering with VLP assembly and function and expands the strategies used to limit retroelement propagation.IMPORTANCERetrotransposons dominate the chromosomal landscape in many eukaryotes, can cause mutations by insertion or genome rearrangement, and are evolutionarily related to retroviruses such as HIV. Thus, understanding factors that limit transposition and retroviral replication is fundamentally important. The present work describes a retrotransposon-encoded restriction protein derived from the capsid gene of the yeast Ty1 element that disrupts virus-like particle assembly in a dose-dependent manner. This form of copy number control acts as a molecular rheostat, allowing high levels of retrotransposition when few Ty1 elements are present and inhibiting transposition as copy number increases. Thus, yeast and Ty1 have coevolved a form of copy number control that is beneficial to both “host and parasite.” To our knowledge, this is the first Gag-like retrotransposon restriction factor described in the literature and expands the ways in which restriction proteins modulate retroelement replication.

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Martínez, Prudencio Martínez, Antonio Rodríguez Torres, Raul Ortiz de Lejarazu, Ana Montoya, José Francisco Martín, and José María Eiros. "Human Immunodeficiency Virus Antibody Testing by Enzyme-Linked Fluorescent and Western Blot Assays Using Serum, Gingival-Crevicular Transudate, and Urine Samples." Journal of Clinical Microbiology 37, no. 4 (1999): 1100–1106. http://dx.doi.org/10.1128/jcm.37.4.1100-1106.1999.

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The aim of the present study was to evaluate the possible utilization of saliva and urine as alternative samples to serum for the diagnosis of human immunodeficiency virus (HIV) infection. A total of 302 individuals participated in the study: 187 HIV-infected individuals (106 had Centers for Disease Control and Prevention [CDC] stage II infection, 19 had CDC stage III infection, and 62 had CDC stage IV infection) and 115 noninfected persons (46 of the noninfected persons were blood donors and 69 belonged to a group at high risk of HIV infection). Paired saliva and urine samples were taken from each of the participants in the study. The presence of HIV-specific antibodies was detected by an enzyme-linked fluorescent assay (ELFA), and the result was confirmed by Western blot analysis (WB). The ELFA with saliva gave maximum sensitivity and specificity values, while ELFA had lower sensitivity (95.2%) and specificity (97.4%) values for detection of HIV antibody in urine samples. WB with all saliva samples fulfilled the World Health Organization criterion for positivity, while only 96.8% of the urine samples were confirmed to be positive by WB. Among the four reactivity patterns found by WB of these alternative samples, the most frequent included bands against three groups of HIV structural proteins (was ENV, POL, and GAG). The reactivity bands most frequently observed were those for the proteins gp160 and gp120. The least common reactivity band was the band for protein p17. The detection of HIV antibodies in saliva samples by means of ELFA with the possibility of later confirmation by WB makes saliva an alternative to serum for possible use in the diagnosis of infection. In contrast, HIV antibody detection in urine samples by the same methodology (ELFA) could be taken into consideration for use in epidemiological studies.

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Yuan, Bing, Stephen Campbell, Eran Bacharach, Alan Rein, and Stephen P. Goff. "Infectivity of Moloney Murine Leukemia Virus Defective in Late Assembly Events Is Restored by Late Assembly Domains of Other Retroviruses." Journal of Virology 74, no. 16 (August 15, 2000): 7250–60. http://dx.doi.org/10.1128/jvi.74.16.7250-7260.2000.

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ABSTRACT The p12 region of the Moloney murine leukemia virus (M-MuLV) Gag protein contains a PPPY motif important for efficient virion assembly and release. To probe the function of the PPPY motif, a series of insertions of homologous and heterologous motifs from other retroviruses were introduced at various positions in a mutantgag gene lacking the PPPY motif. The assembly defects of the PPPY deletion mutant could be rescued by insertion of a wild-type PPPY motif and flanking sequences at several ectopic positions in the Gag protein. The late assembly domain (L-domain) of Rous sarcoma virus (RSV) or human immunodeficiency virus type 1 (HIV-1) could also fully or partially restore M-MuLV assembly when introduced into matrix, p12, or nucleocapsid domains of the mutant M-MuLV Gag protein lacking the PPPY motif. Strikingly, mutant viruses carrying the RSV or the HIV-1 L-domain at the original location of the deleted PPPY motif were replication competent in rodent cells. These data suggest that the PPPY motif of M-MuLV acts in a partially position-independent manner and is functionally interchangeable with L-domains of other retroviruses. Electron microscopy studies revealed that deletion of the entire p12 region resulted in the formation of tube-like rather than spherical particles. Remarkably, the PPPY deletion mutant formed chain structures composed of multiple viral particles linked on the cell surface. Many of the mutants with heterologous L-domains released virions with wild-type morphology.

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Gupta, Sanjay, Kajal Arora, Amita Gupta, and Vijay K. Chaudhary. "Gag-Derived Proteins of HIV-1 Isolates from Indian Patients: Cloning, Expression, and Purification of p17 of B- and C-Subtypes." Protein Expression and Purification 21, no. 3 (April 2001): 378–85. http://dx.doi.org/10.1006/prep.2001.1389.

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Goonetilleke, Nilu, Stephen Moore, Len Dally, Nicola Winstone, Inese Cebere, Abdul Mahmoud, Susana Pinheiro, et al. "Induction of Multifunctional Human Immunodeficiency Virus Type 1 (HIV-1)-Specific T Cells Capable of Proliferation in Healthy Subjects by Using a Prime-Boost Regimen of DNA- and Modified Vaccinia Virus Ankara-Vectored Vaccines Expressing HIV-1 Gag Coupled to CD8+ T-Cell Epitopes." Journal of Virology 80, no. 10 (May 15, 2006): 4717–28. http://dx.doi.org/10.1128/jvi.80.10.4717-4728.2006.

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ABSTRACT A double-blind randomized phase I trial was conducted in human immunodeficiency virus type 1 (HIV-1)-negative subjects receiving vaccines vectored by plasmid DNA and modified vaccinia virus Ankara (MVA) expressing HIV-1 p24/p17 gag linked to a string of CD8+ T-cell epitopes. The trial had two groups. One group received either two doses of MVA.HIVA (2× MVA.HIVA) (n = 8) or two doses of placebo (2× placebo) (n = 4). The second group received 2× pTHr.HIVA followed by one dose of MVA.HIVA (n = 8) or 3× placebo (n = 4). In the pTHr.HIVA-MVA.HIVA group, HIV-1-specific T-cell responses peaked 1 week after MVA.HIVA vaccination in both ex vivo gamma interferon (IFN-γ) ELISPOT (group mean, 210 spot-forming cells/106 cells) and proliferation (group mean stimulation index, 37), with assays detecting positive responses in four out of eight and five out of eight subjects, respectively. No HIV-1-specific T-cell responses were detected in either assay in the 2× MVA.HIVA group or subjects receiving placebo. Using a highly sensitive and reproducible cultured IFN-γ ELISPOT assay, positive responses mainly mediated by CD4+ T cells were detected in eight out of eight vaccinees in the pTHr.HIVA-MVA.HIVA group and four out of eight vaccinees in the 2× MVA.HIVA group. Importantly, no false-positive responses were detected in the eight subjects receiving placebo. Of the 12 responders, 11 developed responses to previously identified immunodominant CD4+ T-cell epitopes, with 6 volunteers having responses to more than one epitope. Five out of 12 responders also developed CD8+ T-cell responses to the epitope string. Induced T cells produced a variety of anti-viral cytokines, including tumor necrosis factor alpha and macrophage inflammatory protein 1β. These data demonstrate that prime-boost vaccination with recombinant DNA and MVA vectors can induce multifunctional HIV-1-specific T cells in the majority of vaccinees.

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Mueller, Steffen, and Eckard Wimmer. "Expression of Foreign Proteins by Poliovirus Polyprotein Fusion: Analysis of Genetic Stability Reveals Rapid Deletions and Formation of Cardioviruslike Open Reading Frames." Journal of Virology 72, no. 1 (January 1, 1998): 20–31. http://dx.doi.org/10.1128/jvi.72.1.20-31.1998.

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ABSTRACT Using a strategy developed by R. Andino, D. Silvera, S. D. Suggett, P. I. Achacoso, C. J. Miller, D. Baltimore, and M. B. Feinberg (Science 265:1448–1451, 1994), we constructed recombinant polioviruses by fusing the open reading frame (ORF) of the green fluorescent protein gene (gfp) of Aequorea victoria or the gag gene (encoding p17-p24) of human immunodeficiency virus type 1 (HIV-1) to the N terminus of the poliovirus polyprotein. All poliovirus expression vectors constructed by us and those obtained from Andino et al. were found to be severely impaired in viral replication and genetically unstable. Upon replication, inserted sequences were rapidly deleted as early as the first growth cycle in HeLa cells. However, the vector viruses did not readily revert to the wild-type sequence but rather retained some of the insert plus the artificial 3Cpro/3CDprocleavage site, engineered between the heterologous sequence and the poliovirus polyprotein, to give rise to genotypes reminiscent of cardioviruses. These virus variants that carry a small leader polypeptide were now relatively stable, and they grew better than their progenitor strains. Reverse transcription followed by PCR and sequence analysis of the genomic RNAs reproducibly revealed a few preferred genotypes among the isolated deletion variants. The remaining truncated inserts were retained through subsequent passages. In the immediate vicinity of the deletion borders, we observed short direct sequence repeats that we propose are involved in aligning RNA strands for illegitimate (nonhomologous) RNA recombination during minus-strand synthesis. On the basis of our results, which are at variance with published data, the utility of poliovirus vectors to express proteins >10 kDa in size through fusion with the polyprotein needs to be reevaluated.

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Poiesz, Michael J., David Choi, James Hengst, Garth Ehrlich, Syamalima Dube, and Bernard J. Poiesz. "Rational Development of Serologic Assays for Anti-HTLV Antibodies." Blood 106, no. 11 (November 16, 2005): 4187. http://dx.doi.org/10.1182/blood.v106.11.4187.4187.

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Abstract Both HIV and HTLV virions are comprised mainly of gag proteins (p24 and p19 for HTLV) (Table 1); while both virions lack their primary RNA transcriptional regulatory proteins (Tax and Tat for HTLV and HIV, respectively), HIV virions contain considerably more surface and transmembrane envelope proteins than do HTLV virions. When subjected to high speed centrifugation almost all detectable viral RNA in HTLV or HIV conditioned, media is contained within a dense, precipatable particle (Table 2). HIV particle associated RNA can be gently immunoprecipitated with beads bound with either anti-gp120 env or anti-gp41 env antibodies indicating the presence of both proteins on the viral envelope. Only minimal immunoprecipitation of HTLV-I RNA was observed with beads bound with either anti-gp46 env or gp21 env antibodies indicating a relative paucity of these two proteins on the viral envelope. 1237 (0.08%) of the VBD samples were positive for HTLV antibodies when analyzed by EIA. Of these, 105 (0.007%) were confirmed as true positives by WB and PCR (50 HTLV; 55 HTLV-II), while the remainder were deemed false positive. When examined by WB and RIPA, 170 (15%) of the false positives gave completely negative signals. 712 (63%) scored positive against p19gag only; 203 (7.9%) against p24 only; 18 (1.6%) both p19 gag and p24 gag; 22 (1.9%) against gp21 env only; 3 (0.3%) both p19 gag and gp21 env. Of the people at risk for HTLV infection, 350 (14%) were positive for HTLV antibodies when analyzed by EIA. Of these, 348 were confirmed as true positives (150 HTLV-I; 198 HTLV-II). Of these, 345 (99.1%) were DNA PCR positive and all were WB positive. However, an additional 11 HTLV-I and 73 HTLV-II EIA negative, PCR positive persons were identified. In the EIA negative PCR positive individuals, approximately one half made antibodies to either HTLV Tax, gp46env and/or gp21 env proteins. Epitope mapping of seroreactivities to HTLV linear and recombinant peptides using 20 each of select EIA true seronegative, true seropositive, falso seronegative, and false seropositive samples indicated that an optimal HTLV antigen prep would omit HTLV p19 gag, and include whole p24 gag and Tax, and recombinant gp46 and gp21 env peptides encoded by nucleic acids 5290–5829 and 6169–6390, respectively.

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Learn, Gerald H., David Muthui, Scott J. Brodie, Tuofu Zhu, Kurt Diem, James I. Mullins, and Lawrence Corey. "Virus Population Homogenization following Acute Human Immunodeficiency Virus Type 1 Infection." Journal of Virology 76, no. 23 (December 1, 2002): 11953–59. http://dx.doi.org/10.1128/jvi.76.23.11953-11959.2002.

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ABSTRACT Understanding the properties of human immunodeficiency virus type 1 (HIV-1) variants capable of establishing infection is critical to the development of a vaccine against AIDS. Previous studies of men have shown that the HIV-1 env gene is homogeneous early in infection, leading to the suggestion that infection is established by a single transmitted variant. However, we report here that all of eight homosexual men evaluated beginning 3.7 to 9 weeks following onset of symptoms of acute infection harbored diverse virus populations in their blood, with median genetic distances averaging 1.08% in the env C2V5 region and 0.81% in the gag p17 gene. Within another 4.7 to 11 weeks, the variant lineage in env became more homogeneous, while gag sequences continued to diversify. Thus, the homogenization that has been reported to characterize acute infection is actually preceded by the replication of multiple virus variants. This early selective process focuses on viral properties within Env but not Gag p17. Hence, the viral homogeneity observed early in HIV-1 infection results from a selective process that occurs during the establishment of infection.

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Goto, Toshiyuki, Chizuko Morita, Taisuke Ashina, Kazuyoshi Ikuta, Shiro Kato, and Masuyo Nakal. "Localization of constituent proteins of HIV Type 1 (HIV-1)." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 3 (August 12, 1990): 340–41. http://dx.doi.org/10.1017/s0424820100159242.

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The localization of the constituent proteins of HIV-1 in the virions and HIV-1-infected cells was examined by indirect immuno-gold labeling with monoclonal antibodies (MoAb) to gag proteins (p18 and p24/p53), to elucidate viral formation of HIV.Persistently HIV-1 (HTLV—IIIB,LAV-1)-infected MT-4 and MOLT-4 cell lines and their cloned cell lines were used as infected cells. Mouse MoAb against HIV-1 gag p18 (V17) and p24/p53 (V107) were used. The cells were fixed with 0.5-1% glutar-aldehyde in phosphate-buffered saline (pH 7.2), dehydrated in ethanol and embedded in epoxy (at 45° Cor 60°C) or Lowicryl K4M resin (at −30°C). The sections were incubated in MoAb at room temperature for 1 h and then incubated in anti-mouse goat IgG conjugated with gold (IgG-gold, 5 or 15 nm; Janssen) for 40 min. After being washed, the sections were stained with uranyl acetate and lead citrate, and were observed in an electron microscope with a tilting apparatus.The spećific reactions with V17 and V107 were detected on HIV-1 particles and in the infected cells. No reactivity was noted between uninfected control cells and the MoAb, or between the infected cells and normal mouse serum. More than 97% of the HIV-1 particles embedded in epoxy resinat 60°C were labeled with gold after exclusion of the HIV particles that were attached to supporting film or completely embedded in the section (Fig. 1). Increased labeling was observed with Lowicryl (Fig. 2)and epoxy resin embedding at 45°C.

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Harcourt, Gillian C., Sarah Garrard, Miles P. Davenport, Anne Edwards, and Rodney E. Phillips. "HIV-1 Variation Diminishes CD4 T Lymphocyte Recognition." Journal of Experimental Medicine 188, no. 10 (November 16, 1998): 1785–93. http://dx.doi.org/10.1084/jem.188.10.1785.

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Effective long-term antiviral immunity requires specific cytotoxic T lymphocytes and CD4+ T lymphocyte help. Failure of these helper responses can be a principle cause of viral persistence. We sought evidence that variation in HIV-1 CD4+ T helper epitopes might contribute to this phenomenon. To determine this, we assayed fresh peripheral blood mononuclear cells from 43 asymptomatic HIV-1+ patients for proliferative responses to HIV-1 antigens. 12 (28%) showed a positive response, and we went on to map dominant epitopes in two individuals, to p24 Gag restricted by human histocompatibility leukocyte antigen (HLA)-DR1 and to p17 Gag restricted by HLA-DRB52c. Nine naturally occurring variants of the p24 Gag epitope were found in the proviral DNA of the individual in whom this response was detected. All variants bound to HLA-DR1, but three of these peptides failed to stimulate a CD4+ T lymphocyte line which recognized the index sequence. Antigenic variation was also detected in the p17 Gag epitope; a dominant viral variant present in the patient was well recognized by a specific CD4+ T lymphocyte line, whereas several natural mutants were not. Importantly, variants detected at both epitopes also failed to stimulate fresh uncultured cells while index peptide stimulated successfully. These results demonstrate that variant antigens arise in HIV-1+ patients which fail to stimulate the T cell antigen receptor of HLA class II–restricted lymphocytes, although the peptide epitopes are capable of being presented on the cell surface. In HIV-1 infection, naturally occurring HLA class II–restricted altered peptide ligands that fail to stimulate the circulating T lymphocyte repertoire may curtail helper responses at sites where variant viruses predominate.

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Brander, Christian, Otto O. Yang, Norman G. Jones, Yun Lee, Philip Goulder, R. Paul Johnson, Alicja Trocha, et al. "Efficient Processing of the Immunodominant, HLA-A*0201-Restricted Human Immunodeficiency Virus Type 1 Cytotoxic T-Lymphocyte Epitope despite Multiple Variations in the Epitope Flanking Sequences." Journal of Virology 73, no. 12 (December 1, 1999): 10191–98. http://dx.doi.org/10.1128/jvi.73.12.10191-10198.1999.

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ABSTRACT Immune escape from cytotoxic T-lymphocyte (CTL) responses has been shown to occur not only by changes within the targeted epitope but also by changes in the flanking sequences which interfere with the processing of the immunogenic peptide. However, the frequency of such an escape mechanism has not been determined. To investigate whether naturally occurring variations in the flanking sequences of an immunodominant human immunodeficiency virus type 1 (HIV-1) Gag CTL epitope prevent antigen processing, cells infected with HIV-1 or vaccinia virus constructs encoding different patient-derived Gag sequences were tested for recognition by HLA-A*0201-restricted, p17-specific CTL. We found that the immunodominant p17 epitope (SL9) and its variants were efficiently processed from minigene expressing vectors and from six HIV-1 Gag variants expressed by recombinant vaccinia virus constructs. Furthermore, SL9-specific CTL clones derived from multiple donors efficiently inhibited virus replication when added to HLA-A*0201-bearing cells infected with primary or laboratory-adapted strains of virus, despite the variability in the SL9 flanking sequences. These data suggest that escape from this immunodominant CTL response is not frequently accomplished by changes in the epitope flanking sequences.

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Cohen, W. M., A. Bianco, F. Connan, L. Camoin, M. Dalod, G. Lauvau, E. Ferriès, et al. "Study of Antigen-Processing Steps Reveals Preferences Explaining Differential Biological Outcomes of Two HLA-A2-Restricted Immunodominant Epitopes from Human Immunodeficiency Virus Type 1." Journal of Virology 76, no. 20 (October 15, 2002): 10219–25. http://dx.doi.org/10.1128/jvi.76.20.10219-10225.2002.

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ABSTRACT Cytotoxic T-lymphocyte (CTL) responses directed to different human immunodeficiency virus (HIV) epitopes vary in their protective efficacy. In particular, HIV-infected cells are much more sensitive to lysis by anti-Gag/p17(77-85)/HLA-A2 than to that by anti-polymerase/RT(476-484)/HLA-A2 CTL, because of a higher density of p17(77-85) complexes. This report describes multiple processing steps favoring the generation of p17(77-85) complexes: (i) the exact COOH-terminal cleavage of epitopes by cellular proteases occurred faster and more frequently for p17(77-85) than for RT(476-484), and (ii) the binding efficiency of the transporter associated with antigen processing was greater for p17(77-85) precursors than for the RT(476-484) epitope. Surprisingly, these peptides, which differed markedly in their antigenicity, displayed qualitatively and quantitatively similar immunogenicity, suggesting differences in the mechanisms governing these phenomena. Here, we discuss the mechanisms responsible for such differences.

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Wei, Qing, and Patricia N. Fultz. "Extensive Diversification of Human Immunodeficiency Virus Type 1 Subtype B Strains during Dual Infection of a Chimpanzee That Progressed to AIDS." Journal of Virology 72, no. 4 (April 1, 1998): 3005–17. http://dx.doi.org/10.1128/jvi.72.4.3005-3017.1998.

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ABSTRACT A chimpanzee (C-499) infected for more than 9 years with two subtype B isolates of human immunodeficiency virus type 1 (HIV-1), one (HIV-1SF2) that replicates poorly and one (HIV-1LAV-1b) that replicates efficiently in chimpanzees, died of AIDS 11 years after initial infection (F. J. Novembre et al., J. Virol. 71:4086–4091, 1997). Nucleotide sequence and phylogenetic analyses of the C2 to V5 region of env(C2-V5 env ) in proviral DNA from peripheral blood lymphocytes obtained 22 months before death revealed two distinct virus populations. One of these populations appeared to be a recombinant in env, having the V3 loop from HIV-1SF2 and the V4-V5 region from HIV-1LAV-1b; the other population had evolved from HIV-1LAV-1b. In addition to C2-V5 env , the entire p17 gag and nef genes were sequenced; however, based on nucleotide sequences and phlyogeny, whether the progenitor of the p17 gag andnef genes was SF2 or LAV-1b could not be determined. Compared to the two original viruses, the divergence of all clones of C2-V5 env ranged from 9.37 to 20.2%, that of p17 gag ranged from 3.11 to 9.29%, and that ofnef ranged from 4.02 to 7.9%. In contrast, compared to the maximum variation of 20.2% in C2-V5 env for C-499, the maximum diversities in C2-V5 env in proviruses from two chimpanzees infected with HIV-1LAV-1bfor 9 and 10 years were 9.65 and 2.48%, respectively. These results demonstrate that (i) two distinct HIV-1 populations can coexist and undergo extensive diversification in chimpanzees with progressive HIV-1-induced disease and (ii) recombination between two subtype B strains occurred even though the second strain was inoculated 15 months after the first one. Furthermore, evaluation of env genes from three chimpanzees infected with the same strain suggests that the magnitude of HIV-1 diversification could be related to higher viral burdens, manifestations of disease, and/or dual infection.

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Goulder, P. J. R., A. K. Sewell, D. G. Lalloo, D. A. Price, J. A. Whelan, J. Evans, G. P. Taylor, et al. "Patterns of Immunodominance in HIV-1–specific Cytotoxic T Lymphocyte Responses in Two Human Histocompatibility Leukocyte Antigens (HLA)-identical Siblings with HLA-A*0201 Are Influenced by Epitope Mutation." Journal of Experimental Medicine 185, no. 8 (April 21, 1997): 1423–33. http://dx.doi.org/10.1084/jem.185.8.1423.

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Primary human immunodeficiency virus (HIV) infection is controlled principally by HIV-specific cytotoxic T lymphocytes (CTL) to a steady-state level of virus load, which strongly influences the ultimate rate of progression to disease. Epitope selection by CTL may be an important determinant of the degree of immune control over the virus. This report describes the CTL responses of two HLA-identical hemophiliac brothers who were exposed to identical batches of Factor VIII and became seropositive within 10 wk of one another. Both have HLA-A*0201. The CTL responses of the two siblings were very dissimilar, one donor making strong responses to two epitopes within p17 Gag (HLA-A*0201–restricted SLYNTVATL and HLA-A3–restricted RLRPGGKKK). The sibling responded to neither epitope, but made strong responses to two epitopes presented by HLA-B7. This was not the result of differences in presentation of the epitopes. However, mutations in both immunodominant epitopes of the p17 Gag responder were seen in proviral sequences of the nonresponder. We then documented the CTL responses to two HLA-A*0201–restricted epitopes, in Gag (SLYNTVATL) and Pol (ILKEPVHGV) in 22 other HIV-infected donors with HLA-A*0201. The majority (71%) generated responses to the Gag epitope. In the 29% of donors failing to respond to the Gag epitope in standard assays, there was evidence of low frequency memory CTL responses using peptide stimulation of PBMC, and most of these donors also showed mutations in or around the Gag epitope. We concluded that HLA class I genotype determines epitope selection initially but that mutation in immunodominant epitopes can profoundly alter the pattern of CTL response.

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Reid, Scott W., Steve McAdam, Kathrine J. Smith, Paul Klenerman, Chris A. O'Callaghan, Karl Harlos, Bent K. Jakobsen, et al. "Antagonist HIV-1 Gag Peptides Induce Structural Changes in HLA B8." Journal of Experimental Medicine 184, no. 6 (December 1, 1996): 2279–86. http://dx.doi.org/10.1084/jem.184.6.2279.

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In the cellular immune response, recognition by CTL-TCRs of viral antigens presented as peptides by HLA class I molecules, triggers destruction of the virally infected cell (Townsend, A.R.M., J. Rothbard, F.M. Gotch, G. Bahadur, D. Wraith, and A.J. McMichael. 1986. Cell. 44:959–968). Altered peptide ligands (APLs) which antagonise CTL recognition of infected cells have been reported (Jameson, S.C., F.R. Carbone, and M.J. Bevan. 1993. J. Exp. Med. 177:1541–1550). In one example, lysis of antigen presenting cells by CTLs in response to recognition of an HLA B8–restricted HIV-1 P17 (aa 24–31) epitope can be inhibited by naturally occurring variants of this peptide, which act as TCR antagonists (Klenerman, P., S. Rowland Jones, S. McAdam, J. Edwards, S. Daenke, D. Lalloo, B. Koppe, W. Rosenberg, D. Boyd, A. Edwards, P. Giangrande, R.E. Phillips, and A. McMichael. 1994. Nature (Lond.). 369:403– 407). We have characterised two CTL clones and a CTL line whose interactions with these variants of P17 (aa 24–31) exhibit a variety of responses. We have examined the high resolution crystal structures of four of these APLs in complex with HLA B8 to determine alterations in the shape, chemistry, and local flexibility of the TCR binding surface. The variant peptides cause changes in the recognition surface by three mechanisms: changes contributed directly by the peptide, effects transmitted to the exposed peptide surface, and induced effects on the exposed framework of the peptide binding groove. While the first two mechanisms frequently lead to antagonism, the third has more profound effects on TCR recognition.

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Haglund, Karl, Ingrid Leiner, Kristen Kerksiek, Linda Buonocore, Eric Pamer, and John K. Rose. "High-Level Primary CD8+ T-Cell Response to Human Immunodeficiency Virus Type 1 Gag and Env Generated by Vaccination with Recombinant Vesicular Stomatitis Viruses." Journal of Virology 76, no. 6 (March 15, 2002): 2730–38. http://dx.doi.org/10.1128/jvi.76.6.2730-2738.2002.

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ABSTRACT We investigated the primary cellular immune responses to human immunodeficiency virus type 1 (HIV-1) Env and Gag proteins elicited by recombinant vesicular stomatitis viruses (rVSVs). The primary response to Env peaked 5 to 7 days after intraperitoneal vaccination, at which time 40% of CD8+ cells were Env tetramer positive and activated (CD62LLo). These freshly isolated cells actively lysed target cells pulsed with the p18-I10 peptide and secreted gamma interferon and tumor necrosis factor alpha after stimulation with the Env p18-I10 peptide. The primary response to Env elicited by rVSVs was sixfold higher than that elicited by recombinant vaccinia viruses (rVVs) at 5 days postvaccination. An intranasal route of vaccination with VSV-Env also elicited a strong primary response to Env. The primary immune response to Gag elicited by rVSV peaked 7 days after vaccination, at which time 3% of CD8+ cells were Gag tetramer positive and CD62LLo and functional by intracellular cytokine staining. This response was eightfold higher than that elicited by rVV expressing Gag. VSV-GagEnv, which expresses both Gag and Env from a single recombinant, also induced strong cytotoxic T-lymphocyte (CTL) responses to both Env and Gag. Our quantitative analyses illustrate the potency of the VSV vector system in CTL induction.

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Morris, A., M. Marsden, K. Halcrow, E. S. Hughes, R. P. Brettle, J. E. Bell, and P. Simmonds. "Mosaic Structure of the Human Immunodeficiency Virus Type 1 Genome Infecting Lymphoid Cells and the Brain: Evidence for Frequent In Vivo Recombination Events in the Evolution of Regional Populations." Journal of Virology 73, no. 10 (October 1, 1999): 8720–31. http://dx.doi.org/10.1128/jvi.73.10.8720-8731.1999.

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ABSTRACT In addition to immunodeficiency, human immunodeficiency virus type 1 (HIV-1) can cause cognitive impairment and dementia through direct infection of the brain. To investigate the adaptive process and timing of HIV-1 entry into the central nervous system, we carried out an extensive genetic characterization of variants amplified from different regions of the brain and determined their relatedness to those in lymphoid tissue. HIV-1 genomes infecting different regions of the brain of one study subject with HIV encephalitis (HIVE) had a mosaic structure, being assembled from different combinations of evolutionarily distinct lineages in p17 gag ,pol, individual hypervariable regions of gp120 (V1/V2, V3, V4, and V5), and gp41/nef. Similar discordant phylogenetic relationships were observed between p17 gag and V3 sequences of brain and lymphoid tissue from three other individuals with HIVE. The observation that different parts of the genome of HIV infecting a particular tissue can have different evolutionary histories necessarily limits the conclusions that can be drawn from previous studies of the compartmentalization of distinct HIV populations in different tissues, as these have been generally restricted to sequence comparisons of single subgenomic regions. The complexity of viral populations in the brain produced by recombination could provide a powerful adaptive mechanism for the spread of virus with new phenotypes, such as antiviral resistance or escape from cytotoxic T-cell recognition into existing tissue-adapted virus populations.

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Caccuri, Francesca, Stefania Marsico, Simona Fiorentini, Arnaldo Caruso, and Cinzia Giagulli. "HIV-1 Matrix Protein p17 and its Receptors." Current Drug Targets 17, no. 1 (December 17, 2015): 23–32. http://dx.doi.org/10.2174/1389450116666150825110840.

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Vorkunova, G. K., S. I. Lupandin, and A. G. Bukrinskaya. "HIV-1 assembly initiated by p17 matrix protein." Molecular Biology 45, no. 5 (October 2011): 811–15. http://dx.doi.org/10.1134/s0026893311050141.

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Hahn, Tobias, Erik Matala, Colombe Chappey, and Nafees Ahmad. "Characterization of Mother-Infant HIV Type 1 gag p17 Sequences Associated with Perinatal Transmission." AIDS Research and Human Retroviruses 15, no. 10 (July 1999): 875–88. http://dx.doi.org/10.1089/088922299310584.

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Columba Cabezas, Sandra, and Maurizio Federico. "Sequences within RNA coding for HIV-1 Gag p17 are efficiently targeted to exosomes." Cellular Microbiology 15, no. 3 (November 7, 2012): 412–29. http://dx.doi.org/10.1111/cmi.12046.

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Sengupta, S., D. Khetawat, S. Jana, K. Sarkar, S. K. Bhattacharya, and S. Chakrabarti. "Polymorphism of HIV-1 gag (p17) gene from female sex workers in Calcutta, India." Archives of Virology 150, no. 10 (June 15, 2005): 2117–24. http://dx.doi.org/10.1007/s00705-005-0562-5.

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Tang, Yao, Ulrike Winkler, Eric O. Freed, Ted A. Torrey, Wankee Kim, Henry Li, Stephen P. Goff, and Herbert C. Morse. "Cellular Motor Protein KIF-4 Associates with Retroviral Gag." Journal of Virology 73, no. 12 (December 1, 1999): 10508–13. http://dx.doi.org/10.1128/jvi.73.12.10508-10513.1999.

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ABSTRACT Previously we demonstrated that murine retroviral Gag proteins associate with a cellular motor protein, KIF-4. Using the yeast two-hybrid assay, we also found an association of KIF-4 with Gag proteins of Mason-Pfizer monkey virus (MPMV), simian immunodeficiency virus (SIV), and human immunodeficiency virus type 1 (HIV-1). Studies performed with mammalian cell systems confirmed that the HIV-1 Gag protein associates with KIF-4. Soluble cytoplasmic proteins from cells infected with recombinant vaccinia virus expressing the entire Gag-Pol precursor protein of HIV-1 or transfected with HIV-1 molecular clone pNL4-3 were fractionated by sucrose gradient centrifugation and further separated by size-exclusion and anion-exchange chromatographies. KIF-4 and HIV-1 Gag cofractionated in both chromatographic separations. Immunoprecipitation assays have also verified the KIF-4–Gag association. KIF-4 binds mainly to the Gag precursor (Pr55 Gag) and a matrix-capsid processing intermediate (Pr42) but not to other processed Gag products. The binding of Gag is mediated by a domain of KIF-4 proximal to the C terminus. These results, and our previous studies, raise the possibility that KIF-4 may play an important role in retrovirus Gag protein transport.

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Bhattacharya, Jayanta, Alexander Repik, and Paul R. Clapham. "Gag Regulates Association of Human Immunodeficiency Virus Type 1 Envelope with Detergent-Resistant Membranes." Journal of Virology 80, no. 11 (June 1, 2006): 5292–300. http://dx.doi.org/10.1128/jvi.01469-05.

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ABSTRACT Assembly of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein on budding virus particles is important for efficient infection of target cells. In infected cells, lipid rafts have been proposed to form platforms for virus assembly and budding. Gag precursors partly associate with detergent-resistant membranes (DRMs) that are believed to represent lipid rafts. The cytoplasmic domain of the envelope gp41 usually carries palmitate groups that were also reported to confer DRM association. Gag precursors confer budding and carry envelope glycoproteins onto virions via specific Gag-envelope interactions. Thus, specific mutations in both the matrix domain of the Gag precursor and gp41 cytoplasmic domain abrogate envelope incorporation onto virions. Here, we show that HIV-1 envelope association with DRMs is directly influenced by its interaction with Gag. Thus, in the absence of Gag, envelope fails to associate with DRMs. A mutation in the p17 matrix (L30E) domain in Gag (Gag L30E) that abrogates envelope incorporation onto virions also eliminated envelope association with DRMs in 293T cells and in the T-cell line, MOLT 4. These observations are consistent with a requirement for an Env-Gag interaction for raft association and subsequent assembly onto virions. In addition to this observation, we found that mutations in the gp41 cytoplasmic domain that abrogated envelope incorporation onto virions and impaired infectivity of cell-free virus also eliminated envelope association with DRMs. On the basis of these observations, we propose that Gag-envelope interaction is essential for efficient envelope association with DRMs, which in turn is essential for envelope budding and assembly onto virus particles.

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Caccuri, Francesca, Pasqualina D’Ursi, Matteo Uggeri, Antonella Bugatti, Pietro Mazzuca, Alberto Zani, Federica Filippini, et al. "Evolution toward beta common chain receptor usage links the matrix proteins of HIV-1 and its ancestors to human erythropoietin." Proceedings of the National Academy of Sciences 118, no. 2 (December 28, 2020): e2021366118. http://dx.doi.org/10.1073/pnas.2021366118.

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The HIV-1 matrix protein p17 (p17) is a pleiotropic molecule impacting on different cell types. Its interaction with many cellular proteins underlines the importance of the viral protein as a major determinant of human specific adaptation. We previously showed the proangiogenic capability of p17. Here, by integrating functional analysis and receptor binding, we identify a functional epitope that displays molecular mimicry with human erythropoietin (EPO) and promotes angiogenesis through common beta chain receptor (βCR) activation. The functional EPO-like epitope was found to be present in the matrix protein of HIV-1 ancestors SIV originated in chimpanzees (SIVcpz) and gorillas (SIVgor) but not in that of HIV-2 and its ancestor SIVsmm from sooty mangabeys. According to biological data, evolution of the EPO-like epitope showed a clear differentiation between HIV-1/SIVcpz-gor and HIV-2/SIVsmm branches, thus highlighting this epitope on p17 as a divergent signature discriminating HIV-1 and HIV-2 ancestors. P17 is known to enhance HIV-1 replication. Similarly to other βCR ligands, p17 is capable of attracting and activating HIV-1 target cells and promoting a proinflammatory microenvironment. Thus, it is tempting to speculate that acquisition of an epitope on the matrix proteins of HIV-1 ancestors capable of triggering βCR may have represented a critical step to enhance viral aggressiveness and early human-to-human SIVcpz/gor dissemination. The hypothesis that the p17/βCR interaction and βCR abnormal stimulation may also play a role in sustaining chronic activation and inflammation, thus marking the difference between HIV-1 and HIV-2 in term of pathogenicity, needs further investigation.

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Efrida, Efrida, and Andani Eka Putra. "KLONING DAN OVEREKSPRESI PROTEIN P24-GAG HIV (Cloning and Overexpression P24-Gag of HIV)." INDONESIAN JOURNAL OF CLINICAL PATHOLOGY AND MEDICAL LABORATORY 22, no. 1 (April 14, 2018): 27. http://dx.doi.org/10.24293/ijcpml.v22i1.1218.

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HIV diagnosis is confirmed by viral culture, but this process takes a long time. Another method used to detect HIV-specific antigensor antibodies is by immunoassay. Generally, antigen-antibody based methods are used as a screening test. Based on the stability ofthe sequences found in the first (1) study year, the researchers designed this study for the production of p24 recombinant protein.These proteins will be developed as diagnostic markers based on sero-immunology technique. The aim of this study was to know theconstruction and over expression of protein p24gag from local isolates and analysis of the diagnostic potential of doing design specificprimers against p24gag protein, cloning and over expression of the gene, as well as to obtain a p24 protein that has been purified.This research results will be applied later to develop a method based on local isolates of HIV diagnosis. This research was a descriptivestudy, conducted over seven (7) months in the Biomedical Laboratory of the Faculty of Medicine, Andalas University and Departmentof Clinical Pathology, Dr. M. Djamil Hospital, Padang. This study was carried out by using samples of local isolates originating fromthe first year of research. Stages of the research were: 1) the design of primers for cloning, amplification and sequencing, 2) cloninginto pDEST and pENT, 3) transformation of the target gene, 4) detection of fragment insertions, 5) protein expression and proteinanalysis by SDS-PAGE, immunoblotting and 6) purification. The conclusions of this study were: the design of specific primers againstp24gag protein used fragments attb1, attb2, Shine Delgano and Kozac effective for protein expression. The results showed that thepresence of protein 24kDa expression was identical to HIV p24gag protein. Further research needs to be conducted to identify potentialimmunological target protein.

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Larrouy, Lucile, C. Chazallon, R. Landman, C. Capitant, G. Peytavin, G. Collin, C. Charpentier, et al. "Gag Mutations Can Impact Virological Response to Dual-Boosted Protease Inhibitor Combinations in Antiretroviral-Naïve HIV-Infected Patients." Antimicrobial Agents and Chemotherapy 54, no. 7 (May 3, 2010): 2910–19. http://dx.doi.org/10.1128/aac.00194-10.

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ABSTRACT ANRS 127 was a randomized pilot trial involving naïve patients receiving two dual-boosted protease inhibitor (PI) combinations. Virological response, defined as a plasma HIV RNA level of <50 copies/ml at week 16, occurred in only 41% patients. Low baseline plasma HIV RNA level was the only significant predictor of virological response. The purpose of this study was to investigate the impact on virological response of pretherapy mutations in cleavage sites of gag, gag-pol, and the gag-pol frameshift region. The whole gag gene and protease-coding region were amplified and sequenced at baseline and at week 16 for 48 patients still on the allocated regimen at week 16. No major PI resistance-associated mutations were detected either at baseline or in the 26 patients who did not achieve virological response at week 16. Baseline cleavage site substitutions in the product of the gag open reading frame at positions 128 (p17/p24) (P = 0.04) and 449 (p1/p6 gag ) (P = 0.01) were significantly more frequent in those patients not achieving virological response. Conversely, baseline cleavage site mutation at position 437 (TFP/p6 pol ) was associated with virological response (P = 0.04). In multivariate analysis adjusted for baseline viral load, these 3 substitutions remained independently associated with virological response. We demonstrated here, in vivo, an impact of baseline polymorphic gag mutations on virological response in naïve patients receiving a combination of two protease inhibitors. However, it was not possible to link the substitutions selected under PI selective pressure with virological failure.

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Kemler, Iris, Dyana Saenz, and Eric Poeschla. "Feline Immunodeficiency Virus Gag Is a Nuclear Shuttling Protein." Journal of Virology 86, no. 16 (May 23, 2012): 8402–11. http://dx.doi.org/10.1128/jvi.00692-12.

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Lentiviral genomic RNAs are encapsidated by the viral Gag protein during virion assembly. The intracellular location of the initial Gag-RNA interaction is unknown. We previously observed feline immunodeficiency virus (FIV) Gag accumulating at the nuclear envelope during live-cell imaging, which suggested that trafficking of human immunodeficiency virus type 1 (HIV-1) and FIV Gag may differ. Here we analyzed the nucleocytoplasmic transport properties of both Gag proteins. We discovered that inhibition of the CRM1 nuclear export pathway with leptomycin B causes FIV Gag but not HIV-1 Gag to accumulate in the nucleus. Virtually all FIV Gag rapidly became intranuclear when the CRM1 export pathway was blocked, implying that most if not all FIV Gag normally undergoes nuclear cycling. In FIV-infected feline cells, some intranuclear Gag was detected in the steady state without leptomycin B treatment. When expressed individually, the FIV matrix (MA), capsid (CA), and nucleocapsid-p2 (NC-p2) domains were not capable of mediating leptomycin B-sensitive nuclear export of a fluorescent protein. In contrast, CA-NC-p2 did mediate nuclear export, with MA being dispensable. We conclude that HIV-1 and FIV Gag differ strikingly in a key intracellular trafficking property. FIV Gag is a nuclear shuttling protein that utilizes the CRM1 nuclear export pathway, while HIV-1 Gag is excluded from the nucleus. These findings expand the spectrum of lentiviral Gag behaviors and raise the possibility that FIV genome encapsidation may initiate in the nucleus.

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Journal articles on the topic 'HIV gag protein p17'

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