Relevant bibliographies by topics / Neutralization antibodies

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  2. Dissertations / Theses
  3. Books
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  5. Conference papers

Academic literature on the topic 'Neutralization antibodies'

Author: Grafiati
Published: 4 June 2021
Last updated: 11 February 2022

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Journal articles on the topic "Neutralization antibodies"

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Ando, Shuji, Ikuo Takashima, and Nobuo Hashimoto. "Neutralization ofChlamydia psittaciwith Monoclonal Antibodies." Microbiology and Immunology 37, no. 10 (October 1993): 753–58. http://dx.doi.org/10.1111/j.1348-0421.1993.tb01701.x.

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Yang, Xinzhen, Svetla Kurteva, Sandra Lee, and Joseph Sodroski. "Stoichiometry of Antibody Neutralization of Human Immunodeficiency Virus Type 1." Journal of Virology 79, no. 6 (March 15, 2005): 3500–3508. http://dx.doi.org/10.1128/jvi.79.6.3500-3508.2005.

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ABSTRACT The human immunodeficiency virus envelope glycoproteins function as trimers on the viral surface, where they are targeted by neutralizing antibodies. Different monoclonal antibodies neutralize human immunodeficiency virus type 1 (HIV-1) infectivity by binding to structurally and functionally distinct moieties on the envelope glycoprotein trimer. By measuring antibody neutralization of viruses with mixtures of neutralization-sensitive and neutralization-resistant envelope glycoproteins, we demonstrate that the HIV-1 envelope glycoprotein trimer is inactivated by the binding of a single antibody molecule. Virus neutralization requires essentially all of the functional trimers to be occupied by at least one antibody. This model applies to antibodies differing in neutralizing potency and to virus isolates with various neutralization sensitivities. Understanding these requirements for HIV-1 neutralization by antibodies will assist in establishing goals for an effective AIDS vaccine.
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Gray, Elin S., Natasha Taylor, Diane Wycuff, Penny L. Moore, Georgia D. Tomaras, Constantinos Kurt Wibmer, Adrian Puren, et al. "Antibody Specificities Associated with Neutralization Breadth in Plasma from Human Immunodeficiency Virus Type 1 Subtype C-Infected Blood Donors." Journal of Virology 83, no. 17 (June 24, 2009): 8925–37. http://dx.doi.org/10.1128/jvi.00758-09.

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ABSTRACT Defining the specificities of the anti-human immunodeficiency virus type 1 (HIV-1) envelope antibodies able to mediate broad heterologous neutralization will assist in identifying targets for an HIV-1 vaccine. We screened 70 plasmas from chronically HIV-1-infected individuals for neutralization breadth. Of these, 16 (23%) were found to neutralize 80% or more of the viruses tested. Anti-CD4 binding site (CD4bs) antibodies were found in almost all plasmas independent of their neutralization breadth, but they mainly mediated neutralization of the laboratory strain HxB2 with little effect on the primary virus, Du151. Adsorption with Du151 monomeric gp120 reduced neutralizing activity to some extent in most plasma samples when tested against the matched virus, although these antibodies did not always confer cross-neutralization. For one plasma, this activity was mapped to a site overlapping the CD4-induced (CD4i) epitope and CD4bs. Anti-membrane-proximal external region (MPER) (r = 0.69; P < 0.001) and anti-CD4i (r = 0.49; P < 0.001) antibody titers were found to be correlated with the neutralization breadth. These anti-MPER antibodies were not 4E10- or 2F5-like but spanned the 4E10 epitope. Furthermore, we found that anti-cardiolipin antibodies were correlated with the neutralization breadth (r = 0.67; P < 0.001) and anti-MPER antibodies (r = 0.6; P < 0.001). Our study suggests that more than one epitope on the envelope glycoprotein is involved in the cross-reactive neutralization elicited during natural HIV-1 infection, many of which are yet to be determined, and that polyreactive antibodies are possibly involved in this phenomenon.
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Wilson, Ian. "Broad Neutralization of Viral Pathogens." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C245. http://dx.doi.org/10.1107/s205327331409754x.

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Influenza, Hepatitis C, and HIV-1 continue to constitute significant threats to global health. We have structurally and functionally characterized several potent, broadly neutralizing antibodies (bnAbs) against HIV-1, influenza and hepatitis C viruses. The surface antigens of these viruses are the main target of neutralizing antibodies. However, most antibodies are strain-specific and protect only against highly related strains within the same subtype. Recently, a number of antibodies have been identified that are much broader and neutralize across multiple subtypes and types of these viruses through binding to functionally conserved sites, such as the receptor binding site or the fusion domain. For example, co-crystal structures of bnAbs with influenza hemagglutinin (HA) identified highly conserved sites in the fusion domain (stem) and in the receptor binding site (head) as target for broad neutralization[1]. HCV is also genetically diverse, but some antibodies have potent neutralizing activity across most genotypes of the virus. One family of these antibodies targets a conserved antigenic site on the HCV E2 envelope glycoprotein that overlaps with the CD81 receptor-binding site[2]. For HIV-1, structural and functional characterization of different families of bnAbs have led to identification of novel epitopes on HIV-1 Env, many of which involve glycans. These glycan-dependent Abs have unique features that enable them to penetrate the glycan shield and bind complex epitopes that consist of sugars and underlying protein segments on gp120 on HIV-1 Env. Recent x-ray[3] and EM structures of a soluble form of HIV-1 Env have revealed that the epitopes are more extensive and complex than previously appreciated. This structural information is now being used to aid in structure-assisted vaccine design for HIV-1, HCV and for a more universal flu vaccine. IAW is supported by NIH grants AI100663, AI082362, AI84817, AI099275 and GM094586 and the Crucell Vaccine Institute.
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Spenlehauer, Catherine, Sentob Saragosti, Hervé J. A. Fleury, André Kirn, Anne-Marie Aubertin, and Christiane Moog. "Study of the V3 Loop as a Target Epitope for Antibodies Involved in the Neutralization of Primary Isolates versus T-Cell-Line-Adapted Strains of Human Immunodeficiency Virus Type 1." Journal of Virology 72, no. 12 (December 1, 1998): 9855–64. http://dx.doi.org/10.1128/jvi.72.12.9855-9864.1998.

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ABSTRACT Previous studies characterized the third variable (V3) loop of the envelope gp120 as the principal neutralizing determinant for laboratory T-cell-line-adapted (TCLA) strains of human immunodeficiency virus type 1 (HIV-1). However, primary viruses isolated from infected individuals are more refractory to neutralization than TCLA strains, suggesting that qualitatively different neutralizing antibodies may be involved. In this study, we investigated whether the V3 loop constitutes a linear target epitope for antibodies neutralizing primary isolates. By using peptides representative of the V3 regions of various primary isolates, an early, relatively specific and persistent antibody response was detected in sera from HIV-infected patients. To assess the relationship between these antibodies and neutralization, the same peptides were used in competition and depletion experiments. Addition of homologous V3 peptides led to a competitive inhibition in the neutralization of the TCLA strain HIVMN/MT-4 but had no effect on the neutralization of the autologous primary isolate. Similarly, the removal of antibodies that bind to linear V3 epitopes resulted in a loss of HIVMN/MT-4 neutralization, whereas no decrease in the autologous neutralization was measured. The different roles of V3-specific antibodies according to the virus considered were thereby brought to light. This confirmed the involvement of V3 antibodies in the neutralization of a TCLA strain but emphasized a more pronounced contribution of either conformational epitopes or epitopes outside the V3 loop as targets for antibodies neutralizing primary HIV-1 isolates. This result underlines the need to focus on new vaccinal immunogens with epitopes able to induce broadly reactive and efficient antibodies that neutralize a wide range of primary HIV-1 isolates.
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Danse, Jean-Marc, Jean-Luc Toussaint, and Jules Kempf. "Neutralization of α-bungarotoxin by monoclonal antibodies." Toxicon 24, no. 2 (January 1986): 141–51. http://dx.doi.org/10.1016/0041-0101(86)90116-9.

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Parren, Paul W. H. I., Isabelle Mondor, Denise Naniche, Henrik J. Ditzel, P. J. Klasse, Dennis R. Burton, and Quentin J. Sattentau. "Neutralization of Human Immunodeficiency Virus Type 1 by Antibody to gp120 Is Determined Primarily by Occupancy of Sites on the Virion Irrespective of Epitope Specificity." Journal of Virology 72, no. 5 (May 1, 1998): 3512–19. http://dx.doi.org/10.1128/jvi.72.5.3512-3519.1998.

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ABSTRACT We investigated the relative importance of binding site occupancy and epitope specificity in antibody neutralization of human immunodeficiency virus (HIV) type 1 (HIV-1). The neutralization of a T-cell-line-adapted HIV-1 isolate (MN) was analyzed with a number of monovalent recombinant Fab fragments (Fabs) and monoclonal antibodies with a range of specificities covering all confirmed gp120-specific neutralization epitopes. Binding of Fabs to recombinant monomeric gp120 was determined by surface plasmon resonance, and binding of Fabs and whole antibodies to functional oligomeric gp120 was determined by indirect immunofluorescence and flow cytometry on HIV-infected cells. An excellent correlation between neutralization and oligomeric gp120 binding was observed, and a lack of correlation with monomeric gp120 binding was confirmed. A similar degree of correlation was observed between oligomeric gp120 binding and neutralization with a T-cell-line-adapted HIV-1 molecular clone (Hx10). The ratios of oligomer binding/neutralization titer fell, in general, within a relatively narrow range for antibodies to different neutralization epitopes. These results suggest that the occupancy of binding sites on HIV-1 virions is the major factor in determining neutralization, irrespective of epitope specificity. Models to account for these observations are proposed.
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Harbison, Carole E., Wendy S. Weichert, Brittney L. Gurda, John A. Chiorini, Mavis Agbandje-McKenna, and Colin R. Parrish. "Examining the cross-reactivity and neutralization mechanisms of a panel of mAbs against adeno-associated virus serotypes 1 and 5." Journal of General Virology 93, no. 2 (February 1, 2012): 347–55. http://dx.doi.org/10.1099/vir.0.035113-0.

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Neutralizing antibodies play a central role in the prevention and clearance of viral infections, but can be detrimental to the use of viral capsids for gene delivery. Antibodies present a major hurdle for ongoing clinical trials using adeno-associated viruses (AAVs); however, relatively little is known about the antigenic epitopes of most AAV serotypes or the mechanism(s) of antibody-mediated neutralization. We developed panels of AAV mAbs by repeatedly immunizing mice with AAV serotype 1 (AAV1) capsids, or by sequentially immunizing with AAV1 followed by AAV5 capsids, in order to examine the efficiency and mechanisms of antibody-mediated neutralization. The antibodies were not cross-reactive between heterologous AAV serotypes except for a low level of recognition of AAV1 capsids by the AAV5 antibodies, probably due to the initial immunization with AAV1. The neutralization efficiency of different IgGs varied and Fab fragments derived from these antibodies were generally poorly neutralizing. The antibodies appeared to display various alternative mechanisms of neutralization, which included inhibition of receptor-binding and interference with a post-attachment step.
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Howe, Laryssa, Jodi K. Craigo, Charles J. Issel, and Ronald C. Montelaro. "Specificity of serum neutralizing antibodies induced by transient immune suppression of inapparent carrier ponies infected with a neutralization-resistant equine infectious anemia virus envelope strain." Journal of General Virology 86, no. 1 (January 1, 2005): 139–49. http://dx.doi.org/10.1099/vir.0.80374-0.

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It has been previously reported that transient corticosteroid immune suppression of ponies experimentally infected with a highly neutralization resistant envelope variant of equine infectious anemia virus (EIAV), designated EIAVΔPND, resulted in the appearance of type-specific serum antibodies to the infecting EIAVΔPND virus. The current study was designed to determine if this induction of serum neutralizing antibodies was associated with changes in the specificity of envelope determinants targeted by serum antibodies or caused by changes in the nature of the antibodies targeted to previously defined surface envelope gp90 V3 and V4 neutralization determinants. To address this question, the envelope determinants of neutralization by post-immune suppression serum were mapped. The results demonstrated that the neutralization sensitivity to post-immune suppression serum antibodies mapped specifically to the surface envelope gp90 V3 and V4 domains, individually or in combination. Thus, these data indicate that the development of serum neutralizing antibodies to the resistant EIAVΔPND was due to an enhancement of host antibody responses caused by transient immune suppression and the associated increase in virus replication.
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Klasse, P. J., and Q. J. Sattentau. "Occupancy and mechanism in antibody-mediated neutralization of animal viruses." Journal of General Virology 83, no. 9 (September 1, 2002): 2091–108. http://dx.doi.org/10.1099/0022-1317-83-9-2091.

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Neutralization of virus infectivity by antibodies is an important component of immunity to several virus infections. Here, the immunochemical basis for the action of neutralizing antibodies, and what role their induction of conformational changes in the antigen might play, is reviewed. Theories of the mechanisms by which antibodies neutralize virus infectivity in vitro are also presented. The theoretical and empirical foundation of the hypothesis that viruses are neutralized by a single antibody per virion is critically reviewed. The relationship between antibody occupancy on virions and the mechanism of neutralization is explored. Examples of neutralization mediated through antibody interference with virus attachment and entry are discussed and test implications of refined theories of neutralization by antibody coating of virions are formulated.
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Dissertations / Theses on the topic "Neutralization antibodies"

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García, Mark Megan Olga. "Production and validation of anti-HCV antibodies for viral neutralization." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278578.

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Hepatitis-C Virus (HCV) remains the leading cause of liver transplant in the US and the UK, and the World Health Organization (WHO) estimates that 71 million people are infected worldwide. A vaccine would drastically impact the healthcare-associated burdens that HCV causes globally. The objective of this master’s thesis project is to produce human antibody (IgG) against HCV. This project will focus on the monoclonal antibodies (mAbs) HEPC3, AR3C, HEPC74, and HCV1. These four antibodies have been isolated from patients who have successfully cleared the infection, and their sequences and structures are available in the public domain. These four antibodies have also shown to bind to E2, a glycoprotein on the surface HCV that is crucial for viral binding and entry. This interaction of the mABs with E2 has been implicated in viral neutralization, making them promising choices for this study. Overall, 3 out of 4 mAbs were successfully cloned and produced. The unsuccessful antibody, HEPC74, was discovered to have failed due to an error in the plasmid sequence. Just as the western blot to confirm secretion was ready to be run, the laboratory closed due the Covid-19 outbreak. Therefore, the data can officially declare a ¾ mAb production success, however it is safe to assume that the alternative clone for HEPC74 was also a success due to a perfect sequence match. Since the primary objective of this project was to successfully clone and produce these four antibodies, then this study is considered an overall success. Lastly, this study examined how the same protocol  could be applied the SARS-CoV-2 outbreak, by the cloning and production of anti-RBD IgG and testing them for viral neutralization.
Hepatit-C (HCV) är fortsatt den enskilt största orsaken till levertransplantationer med uppskattningsvis 71 miljoner infekterade globalt sett, enligt världshälsoorganisationen (WHO).Ett vaccin mot HCV skulle drastiskt minska trycket på global hälso- och sjukvård. Syftet med detta projekt är att producera antikroppar (igG) mot HCV. Projektet fokuserar på HEPC3, AR3C, HEPC74 och HCV1 som är monoklonala antikroppar (mAbs). Dessa antikroppsvarianter har isolerats från patienter som tillfrisknat från infektion. Både DNA-sekvenser och strukturer av antikropparna finns offentligt tillgängliga. Dessa fyra antikroppar har också visats kunna binda till E2 som är ett membranbundet glykoprotein hos HCV som är centralt för viral adhesion och fusion. Interaktionen mellan dessa mAbs och E2 har visat sig neutralisera virulens, vilket gör dem till lovande kandidater för denna studie. Tre av fyra mAbs kunde klonas och produceras framgångsrikt. Försöket med HEPC74 misslyckades på grund av ett fel i plasmidsekvensen och just som western blot skulle genomföras för att bekräfta sekretion av en alternativ klon avslutades the praktiska arbetet med anledning av Covid-19 utbrottet. Resultaten visar entydigt att tre av fyra mAb producerades framgångsrikt. Det går dock att anta att det andra försöket med HEPC74 sannolikt också lyckades pga perfekt sekventiell matchning. Då det huvudsakliga syftet med projektet var att framgångsrikt klona och producera dessa fyra antikroppar så kan studien anses vara framgångsrik. Slutligen så undersöktes huruvida samma förfarande kunde appliceras mot SARS-CoV-2 genom kloning och produktion av anti-RBD IgG och tester av viral neutralisering.
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Chou, Chia-Wei Thomas. "HIV neutralization through use of antibodies and pharmacokinetics of topical applications." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12073.

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Thesis (M.A.)--Boston University
The Human Immunodeficiency Virus Type 1 (HIV-1), a sexually transmitted retrovirus that causes the Acquired Immunodeficiency Syndrome (AIDS), infects over two million people a year. Several methods introduced to prevent HIV-1 transmission, such as condoms, circumcision and antiretroviral drugs, have proven to be partially effective, but more effective approaches are being sought. Topical microbicides are being developed to provide a women-controlled method to prevent the transmission of HIV-1. Unfortunately, most of the candidate microbicide compounds tested to date have either elicited undesirable mucosal inflammation and epithelial lesions leading to increased seroconversions, or have been ineffective. One novel approach currently being explored is the use of monoclonal antibodies as components of topical microbicides. Monoclonal antibodies can be produced inexpensively by transfection into Nicotiana plants. We hypothesize that anti-HIV monoclonal antibodies produced in Nicotiana (MAb-N) will be effective in neutralizing HIV- 1 when used as topical microbicides at mucosal sites, and set out to test whether they retain their efficacy under physiological conditions. We tested the pharmacodynamics of anti-HIV MAb-N efficacy in Cynomolgus macaques following application of the antibodies in the vaginal compartment. We further studied the ability of MAb-N to cross through the vaginal epithelium using an EpiVaginal tissue model. To determine the pharmacodynamics of HIV neutralizing activity after the application of anti-HIV MAb-Ns to the vaginal mucosa, we used a neutralization assay based on HIV-expression in the TZM-bl cell line to test the efficacy of various doses of MAbs in a time course after they had been administered intravaginally in gel form to Cynomolgus macaques. To determine the pharmacokinetics of Mab-N transport across the vaginal epithelium, monoclonal antibodies were added to the apical surface, and a human-IgG ELISA was used to detect Mab-N that had crossed the epithelium into the basal supernatant. Immunohistology was used to confirm and validate ELISA data for evidence of transfer of Mabs across the epithelial layer. Our results show that anti-HIV MAb-Ns were effective in neutralizing cell-free HIV in TZM-bl neutralization assays. We found that MAb-Ns retained their anti-viral efficacy in monkeys after 4-hours. However, neutralizing activity was decreased after 24- hours and 72-hours, with wide variability in effectiveness between individual macaques. Mab-ns tested in the EpiVaginal tissue model showed minimal transfer of antibodies across the epithelium, ranging from 0.005% to 0.09%. Immunohistological data showed that antibodies applied apically to tissue models concentrated only in the superficial layers of the stratum corneum and did not penetrate the epithelium. Our data indicate that anti-HIV MAb-Ns are effective in neutralizing HIV-1 following vaginal application for at least 4 hours, and that they do not pass through the vaginal epithelium in significant amounts. Our data support their further development as vaginal microbicides.
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Martin, Nicole C. Couillard Nicole. "Differential dengue tropism & neutralization : potential mechanisms of pathogenesis /." Download the dissertation in PDF, 2006. http://www.lrc.usuhs.mil/dissertations/pdf/Martin2006.pdf.

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Gias, Edna Lyn Michael. "Mechanism of human respiratory syncytial virus (hRSV) resistance to neutralization by anti-fusion glycoprotein antibodies." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435566.

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Yari, Fayezeh. "Expression of recombinant neutralizing anti-HIV-1 antibodies in bacteria and eukaryotic cells /." Stockholm : Karolisnska institutet, 2007. http://diss.kib.ki.se/2007/978-91-7357-079-4/.

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Johnson, Jacklyn. "Properties of HIV-1 env and human seminal fluid that determine virus inhibition by antibodies and microbicides." Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/6966.

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Human immunodeficiency virus type 1 (HIV-1) establishes a persistent infection that leads to acquired immunodeficiency syndrome (AIDS). Approximately 36 million people worldwide are living with HIV-1, which is commonly acquired through sexual contact. Antiviral therapies control disease progression, but do not eliminate this virus from the host. Thus, global efforts are focused on developing vaccines that prevent HIV-1 transmission. Such vaccines are based on eliciting the production of protective antibodies that target the envelope glycoproteins (Envs) of this virus. Unfortunately, HIV-1 immunization trials have shown limited efficacy. A better understanding of the antibody-mediated inactivation process is needed to improve vaccine strategies. In this work we describe two novel factors that contribute to HIV-1 inactivation. First, we show that structural stability of the Env protein determines its sensitivity to vaccine-elicited antibodies. Different interactions within Env contribute to its stability. Perturbation of the Env-stabilizing interactions by physical and chemical treatments enhances sensitivity of HIV-1 to antibodies. Second, we found that the chemical composition of the transmission medium affects Env inhibition by antibodies and other inhibitory agents. Semen is the most common vehicle for HIV-1 transmission. This medium contains high concentrations of the sugar fructose. We found that semen fructose competitively blocks binding of antiviral agents that target sugar residues on Env. Together, this work advances our understanding of the mechanism that underlies HIV-1 inactivation by vaccine-elicited antibodies and provides novel strategies to enhance their potency.
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Ubillus, Borja Elizabeth Noelia. "Titulación de anticuerpos al virus Chikungunya mediante la técnica de neutralización por reducción de placas." Bachelor's thesis, Universidad Ricardo Palma, 2016. http://cybertesis.urp.edu.pe/handle/urp/845.

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El presente trabajo de tesis tuvo como objetivo titular anticuerpos neutralizantes contra una cepa endémica del virus Chikungunya que circula en la costa norte peruana. Para desarrollar esta investigación, se empleó la prueba de neutralización por reducción en placas (PRNT), la cual se realizó en el Instituto Nacional de Salud (INS)– Laboratorio de Aislamiento y Cultivo Celular perteneciente al área de Metaxénicas Virales. La justificación de la investigación se basa en la necesidad de comprobar que los anticuerpos detectados por la prueba de ELISA son neutralizantes y logran inhibir la dispersión del CHIKV en el cuerpo humano. Además, la prueba es necesaria para evaluar drogas antivirales y futuras vacunas que lleguen al Perú. El diseño metodológico utilizado fue analítico y experimental. La cepa y las muestras fueron proporcionadas por el INS y provinieron del departamento de Tumbes. Las muestras positivas fueron previamente diagnosticadas con ELISA utilizando IgM e IgG y las muestras negativas fueron de individuos sanos sin contacto previo con arbovirus. La prueba de PRNT se realizó en 24 horas usando la línea celular VERO CCL-81 en monocapa. La valoración de la prueba se realizó al 50% de neutralización. Se obtuvo como resultado títulos de anticuerpos en el rango de 1/8 y 1/16. Ésta variación responde a una relación inversa con el inicio de los días de síntomas. Por lo tanto, se concluye que la población de la costa norte del Perú sí está desarrollando anticuerpos neutralizantes para contrarrestar el virus Chikungunya endémico en la región.The present thesis aims to titrate neutralizing antibodies against an endemic strain of the Chikungunya virus that circulates in the northern coast of Peru. In order to develop this research, the plaque reduction neutralization test (PRNT) has been used, which has been carried out at the National Institutes of Health (INS) - Isolation and Cell Culture Laboratory belonging to the Viral Metaxenics area. The justification of the investigation is based on the need to verify that the antibodies detected by the ELISA test are neutralizing and manage to inhibit the dispersion of CHIKV in the human body. In addition, the test is necessary to evaluate antiviral drugs and future vaccines that arrive in Peru. The methodological design used was analytical and experimental. The strain and samples were provided by the INS. The strain is endemic to the department of Tumbes. The positive samples were previously diagnosed with ELISA using IgM and IgG and the negative samples were from individuals that had not had contact with any arbovirus. The PRNT test was performed in 24 hours using the VERO CCL-81 cell line in monolayer. The titration of the test was performed at 50% neutralization. Antibody titres were obtained in the range of 1/8 and 1/16. This variation responds to an inverse relationship with the onset of symptom days. Therefore, it is concluded that the population of the northern coast of Peru is developing neutralizing antibodies to counteract the endemic Chikungunya virus in the region.
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SANTOS, e. SILVA ED C. "Uso de venenos de serpentes australianas como potencial alternativa para a produção de soro anti-elapídico." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/25666.

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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-02-03T11:52:39Z No. of bitstreams: 0
Made available in DSpace on 2016-02-03T11:52:39Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Gagneux-Brunon, Amandine. "Rôle du réservoir viral et de l'immunité humorale du sperme dans la transmission sexuelle de HIV." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES050/document.

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HIV est principalement transmis par voie sexuelle. Bien que les stratégies de prévention basées sur les antirétroviraux (TasP et PrEP) soient efficaces, d'autres approches (en particulier vaccinales) restent d' actualité.Dans la première partie de ce travail, nous avons caractérisé le réservoir séminal de HIV chez des patients chroniquement infectés et sous trithérapie antirétrovirale (TARV). Dans le sperme, HIV est présent sous forme libre et/ou associée aux NSMC. Ces deux formes peuvent être transmises. Le TARV réduit la quantité de virus libre dans le sperme, sans éliminer le virus associé aux NSMC. A heure du TasP, comme meilleur outil de prévention de la transmission sexuelle, mieux caractériser l'état de ce virus résiduel (latent, réplicatif, défectif ?) est nécessaire. Dans notre travail, le virus associé aux NSMC n'a pas été réactivé, laissant supposer que le virus résiduel dans les NSMC de patients sous TARV au long cours, peut être défectif. Ces données restent à confirmer dans de plus grandes cohortes.Dans la deuxième partie du travail, nous avons caractérisé sur le plan isotypique et fonctionnel, les anticorps dirigés contre HIV du sperme. L'objectif est de mettre en évidence des anticorps « large spectre » neutralisant HIV, et/ou inhibant la transcytose, et/ou capables d'ADCC et ciblant les souches virales potentiellement transmissibles par voie sexuelle. Nous avons identifié dans le plasma séminal de certains patients des anticorps neutralisant des souches X4 tropiques, alors que les souches majoritairement transmises par voie sexuelle sont R5 tropiques. Nous avons observé la capacité d' anticorps dirigés contre HIV du plasma séminal à traverser un épithélium monocouche. Le rôle protecteur ou facilitateur est à préciser. Des anticorps protecteurs pourraient être utilisés dans des formulations de type microbicides ou en immunothérapie et contribuer également à un développement de vaccin après identification des épitopes cibles
HIV new infections are mostly related to sexual transmission. Semen contains HIV free particles and cell-associated HIV. Both forms are sexually transmitted. Although PrEP and TasP are efficient to prevent HIV sexual transmission, other strategies like a Vaccine remain needed.In a first part, we studies HIV reservoir in HIV-infected patients receiving combined antiretroviral treatment (cART) in semen. cART reduced HIV viral load in semen, but had a no activity against cell-associated HIV. We tried to reactivate HIV cell reservoir in semen to better characterize its role. We did not observe any reactivation; HIV reservoir in semen might be mostly latent, or defective. This observation should be confirmed in larger cohort of patients.In a second part, we aimed to study the prevalence of anti-HIV antibodies in semen and their role in sexual transmission. Semen of HIV-infected men contains anti-HIV immunoglobulins (Igs), mostly IgG. We observed that unspecific Igs (IgG, IgAl, IgA2) and anti-HIV IgG and IgA were able to transmigrate across an epithelium monolayer mimicking endocervix. This transmigration property may facilitate HIV transcytosis. We also observed a neutralizing activity by Igs purified from semen of 2 chronically infected patients against a X4-tropic viral strain. Seminal anti-HIV may exhibit a dual role (facilitating or limiting) HIV sexual transmission. Protective antibodies purified from semen might be used in preventive strategies like microbicides or serotherapy, and may help to develop vaccine after identification of their epitopes
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Prachanronarong, Kristina L. "Understanding Drug Resistance and Antibody Neutralization Escape in Antivirals: A Dissertation." eScholarship@UMMS, 2016. https://escholarship.umassmed.edu/gsbs_diss/840.

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Antiviral drug resistance is a major problem in the treatment of viral infections, including influenza and hepatitis C virus (HCV). Influenza neuraminidase (NA) is a viral sialidase on the surface of the influenza virion and a primary antiviral target in influenza. Two subtypes of NA predominate in humans, N1 and N2, but different patterns of drug resistance have emerged in each subtype. To provide a framework for understanding the structural basis of subtype specific drug resistance mutations in NA, we used molecular dynamics simulations to define dynamic substrate envelopes for NA to determine how different patterns of drug resistance have emerged in N1 and N2 NA. Furthermore, we used the substrate envelope to analyze HCV NS3/4A protease inhibitors in clinical development. In addition, influenza hemagglutinin (HA) is a primary target of neutralizing antibodies against influenza. Novel broadly neutralizing antibodies (BnAbs) against the stem region of HA have been described and inhibit several influenza viral subtypes, but antibody neutralization escape mutations have emerged. We identified potential escape mutations in broadly neutralizing antibody F10 that may impact protein dynamics in HA that are critical for function. We also solved crystal structures of antibody fragments that are important for understanding the structural basis of antibody binding for influenza BnAbs. These studies can inform the design of improved therapeutic strategies against viruses by incorporating an understanding of structural elements that are critical for function, such as substrate processing and protein dynamics, into the development of novel therapeutics that are robust against resistance.
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Books on the topic "Neutralization antibodies"

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DIMMOCK, NIGEL. Neutralization Of Animal Viruses (Current Topics in Microbiology & Immunology). Springer, 1993.

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Vaheri, Antti, James N. Mills, Christina F. Spiropoulou, and Brian Hjelle. Hantaviruses. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0035.

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Hantaviruses (genus Hantavirus, family Bunyaviridae) are rodent- and insectivore-borne zoonotic viruses. Several hantaviruses are human pathogens, some with 10-35% mortality, and cause two diseases: hemorrhagic fever with renal syndrome (HFRS) in Eurasia, and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. Hantaviruses are enveloped and have a three-segmented, single-stranded, negative-sense RNA genome. The L gene encodes an RNA-dependent RNA polymerase, the M gene encodes two glycoproteins (Gn and Gc), and the S gene encodes a nucleocapsid protein. In addition, the S genes of some hantaviruses have an NSs open reading frame that can act as an interferon antagonist. Similarities between phylogenies have suggested ancient codivergence of the viruses and their hosts to many authors, but increasing evidence for frequent, recent host switching and local adaptation has led to questioning of this model. Infected rodents establish persistent infections with little or no effect on the host. Humans are infected from aerosols of rodent excreta, direct contact of broken skin or mucous membranes with infectious virus, or rodent bite. One hantavirus, Andes virus, is unique in that it is known to be transmitted from person-to-person. HFRS and HCPS, although primarily affecting kidneys and lungs, respectively, share a number of clinical features, such as capillary leakage, TNF-, and thrombocytopenia; notably, hemorrhages and alterations in renal function also occur in HCPS and cardiac and pulmonary involvement are not rare in HFRS. Of the four structural proteins, both in humoral and cellular immunity, the nucleocapsid protein appears to be the principal immunogen. Cytotoxic T-lymphocyte responses are seen in both HFRS and HCPS and may be important for both protective immunity and pathogenesis. Diagnosis is mainly based on detection of IgM antibodies although viral RNA (vRNA) may be readily, although not invariably, detected in blood, urine and saliva. For sero/genotyping neutralization tests/RNA sequencing are required. Formalin-inactivated vaccines have been widely used in China and Korea but not outside Asia. Hantaviruses are prime examples of emerging and re-emerging infections and, given the limited number of rodents and insectivores thus far studied, it is likely that many new hantaviruses will be detected in the near future.
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Book chapters on the topic "Neutralization antibodies"

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Prado, Ilia, Timothy R. Fouts, and Antony S. Dimitrov. "Neutralization of HIV by Antibodies." In Therapeutic Antibodies, 517–31. Totowa, NJ: Humana Press, 2008. http://dx.doi.org/10.1007/978-1-59745-554-1_28.

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Koren, E., F. Milotic, F. A. Neethling, and D. K. C. Cooper. "Neutralization of the Cytotoxic Effect of Anti-αGal Antibodies with Monoclonal Anti-idiotypic Antibodies." In Xenotransplantation, 377–86. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-60572-7_27.

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Woods, Roger D., Ronald D. Wesley, and Paul A. Kapke. "Complement-Dependent Neutralization of Transmissible Gastroenteritis Virus by Monoclonal Antibodies." In Coronaviruses, 493–500. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-1280-2_64.

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Sagawa, T., Y. Abe, S. Kimura, Y. Hitsumoto, and S. Utsumi. "Mechanisms of Neutralization of Endotoxin by Monoclonal IgG Antibodies to Lipopolysaccharide." In Immune Consequences of Trauma, Shock, and Sepsis, 495–500. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-73468-7_61.

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Mazanec, Mary B., Charlotte S. Kaetzel, Michael E. Lamm, David Fletcher, Janet Peterra, and John G. Nedrud. "Intracellular Neutralization of Sendai and Influenza Viruses by IgA Monoclonal Antibodies." In Advances in Experimental Medicine and Biology, 651–54. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1941-6_137.

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Dimitrova, Kristina, Emelissa J. Mendoza, Nicole Mueller, and Heidi Wood. "A Plaque Reduction Neutralization Test for the Detection of ZIKV-Specific Antibodies." In Methods in Molecular Biology, 59–71. New York, NY: Springer US, 2020. http://dx.doi.org/10.1007/978-1-0716-0581-3_5.

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Smith, Jessica L., and Alec J. Hirsch. "Analysis of Serum Anti-Zika Virus Antibodies by Focus Reduction Neutralization Test." In Methods in Molecular Biology, 73–80. New York, NY: Springer US, 2020. http://dx.doi.org/10.1007/978-1-0716-0581-3_6.

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Matthews, Th J., A. J. Langlois, W. G. Robey, N. T. Chang, R. C. Gallo, P. J. Fischinger, and D. P. Bolognesi. "Restricted Neutralization of Divergent HTLV-III/LAV Isolates by Antibodies to the Major Envelope Glycoprotein." In Haematology and Blood Transfusion / Hämatologie und Bluttransfusion, 414–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72624-8_89.

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Oggero, M., R. Frank, R. Kratje, and M. Etcheverrigaray. "Neutralization of the Biological Activity of Glycosylated and Non-Glycosylated hGM-CSF by Monoclonal Antibodies." In Animal Cell Technology: From Target to Market, 23–25. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0369-8_7.

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Sagawa, T., Y. Hitsumoto, M. Kanoh, S. Utsumi, and S. Kimura. "Mechanisms of Neutralization of Endotoxin by Monoclonal Antibodies to O and R Determinants of Lipopolysaccharide." In Endotoxin, 341–44. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4757-5140-6_29.

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Conference papers on the topic "Neutralization antibodies"

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Younes, Salma, Hadeel Al-Jighefee, Farah Shurrab, Duaa Al-Sadeq, Hadi Yassine, Asmaa Althani, Reham Marei, Hashim Alhussain, and Gheyath Nasrallah. "Validation of Selected Commercial Serological Assays for Diagnosis of COVID-19." In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0306.

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As researchers around the globe rush to put the available antibody tests to use, concerns have been raised about their precision. This study aimed to evaluate and compare the performance of selected commercial & automated serological assays that are widely used in different clinical settings in Qatar. We validated the performance of five commercial IgG and IgM ELISA kits, three fully automated immunoassays, and two commercial rapid tests. The sensitivity of all assays was compared to RT-PCR and a surrogate virus neutralization test (sVNT). In addition, cross-reactivity was investigated. Among the evaluated kits, Lionex IgG assay demonstrated the best performance (~88% sensitivity and ~99 specificity). All automated assays showed an excellent correlation with the neutralization test with an overall agreement of 93.6-98.5%. The rapid assays demonstrated a very good performance in detecting IgG antibodies (86.0-88.0% sensitivity and 98.0-100% specificity).
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Brien, W., G. Denome, and B. O’Keefe. "THE PREVELANCE OF ANTIPHOSPHOLIPID ANTIBODIES, BY ELISA TECHNIQUE, IN PATIENTS WITH THE LUPUS ANTICOAGULANT." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644234.

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Patients with the Lupus Anticoagulant and/or anticardiolipin antibodies have been reported to be at increased risk of thrombosis and miscarriages. It has been proposed that the lupus anticoagulant is an antiphospholipid antibody.We evaluated 16 patients with the lupus anticoagulant for the presence of antiphospholipid antibodies. The lupus anticoagulant was documented by the presence of an abnormal APTT, abnormal mixing studies, positive tissue thromboplastin inhibition test and positive platelet neutralization test.Plasma from each patient was assessed for the presence of anticardiolipin, antiphosphatidylserine and antiphosphatidyl-glycerol antibodies by ELISAtechniques. As a control, a neutral phospholipid phosphatidylethanolamine was used. A positive result was established when a delta value of lipid minus control was greater than 3SD compared to a normal population (20 pt.).Using three different patient dilutions, positive results were obtained in 10/16 pt. for anticardiolipin, 11/16 pt. for antiphosphatidylserine and 5/16 pt. for antiphosphatidyl-glycerol antibodies. Three patients were negative for all lipids. If a neutral phospholipid was not used and a delta volume not obtained, 15/16 patients would have had positive results.Our results suggest 1) Not all patients with the Lupus Anticoagulant have antiphosphilipid antibodies by ELISA technique. In evaluating patients with thrombosis and/or miscarriages, both tests should be performed.2) Anticardiolipin antibodies are not present in all patients and with a panel of other negatively charged phospholipids more positive results are obtained. 3) A neutral lipid should be used as a control for non-specific binding of antibody and delta values obtained to see if the results obtained is truly against the negatively charged lipid.
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Masternak, Krzysztof, Valéry Moine, Lucile Broyer, Xavier Chauchet, Vanessa Buatois, Elie Dheilly, Stefano Majocchi, et al. "Abstract 1495: Neutralization of CD47 in cancer cells with bispecific antibodies harnesses the phagocytic potential of tumor-infiltrating macrophages." In Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA. American Association for Cancer Research, 2016. http://dx.doi.org/10.1158/1538-7445.am2016-1495.

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Simões, Marisol, Stephanie Silva, Sheila Lima, and Luiz Camacho. "Standardization and performance of the micro plaque reduction neutralization-Horseradish Peroxidase (μPRN-HRP) : a test for quantification of yellow fever antibodies." In International Symposium on Immunobiological. Instituto de Tecnologia em Imunobiológicos, 2021. http://dx.doi.org/10.35259/isi.2021_46607.

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Kunhipurayil, Hasna, Muna Ahmed, and Gheyath Nasrallah. "West Nile Virus Seroprevalence among Qatari and Immigrant Populations within Qatar." In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0197.

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Background: West Nile virus (WNV) is one of the most widely spread arboviruses worldwide and a highly significant pathogen in humans and animals. Despite frequent outbreaks and endemic transmission being reported in the Middle East and North Africa (MENA), seroprevalence studies of WNV in Qatar are highly lacking. Aim: This study aims to investigate the actual prevalence of WNV among local and expatriate communities in the Qatar using a large sample size of seemingly healthy donors. Method: A total of 1992 serum samples were collected from donors of age 18 or older and were tested for the presence of WNV antibodies. Serion enzyme-linked immunosorbent assay (ELISA) commercial microplate kits were used to detect the presence of the WNV IgM and IgG. The seropositivity was statistically analyzed using SPSS software with a confidence interval of 95%. Results: The seroprevalence of anti-WNV IgG and IgM in Qatar was 10.3% and 3.4%, respectively. The country-specific seroprevalence according to nationality for WNV IgG and IgM, respectively, were Sudan (37.0%, 10.0%), Egypt (31.6%, 4.4%), India (13.4%, 3.2%), Yemen(10.2%, 7.0%), Pakistan (8.6%, 2.7%), Iran (10.6%, 0.0%), Philippines (5.4%, 0.0%), Jordan(6.8%, 1.1%), Syria (2.6%, 9.6%), Palestine (2.6%, 0.6%), Qatar (1.6%, 1.7%), and Lebanon (0.9%, 0.0%). The prevalence of both IgM and IgG was significantly correlated with the nationality (p≤0.001). Conclusion: Among these tested nationalities, Qatar national has a relatively low burden of WNV disease. The highest prevalence of WNV was found in the Sub Saharan African nationalities like Sudan and Egypt. The seroprevalence of WNV is different from the previously reported arboviruses such as CHIKV and DENV, which was highest among Asian countries (India and Philippines). Further confirmatory tests such as viral neutralization assays are needed to confirm the IgM seropositivity in these samples since these samples could be a source of viral transmission through blood donation.
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Fair, D. S., H. A. Chapman, C. L. Allen, and R. Yee. "IN VITRO CHARACTERIZATION OF THE PROCQAGULANT ACTIVITY WITHIN THE BRONCHQALVEOLAR COMPARTMENT OF NORMAL HUMAN LUNG." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643846.

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The procoagulant activity (PCA) of the normal human broncho-alveolar (BA) lining layer was examined qualitatively and quantitatively. Unconcentrated, cell-free lavage freshly obtained from normal volunteers clotted whole plasma in 84 ± 20 sec. The PCA was initiated by factor VII (F VII) and tissue factor (TF) complexes as judged by differential activities in various plasmas genetically deficient in single clotting factors and by neutralization of the PCA with antibodies to either F VII or TF. The cell-free fluid contained about 8500 thromboplastin units/mg total protein. The fluid also contained F VII activity estimated by clotting activity to be 2 ng of plasma F VII/ml of lavage fluid or 22 ng/mg total protein compared to 7 ng/mg protein for normal human plasma. Amidolytic activity measurements suggested that the F VTI concentration was 0.57 ng/ml of lavage fluid. Because of the increased amounts of F VII expressed in the lung relative to plasma, we investigated the activation state of the F VII by the ratio of clotting to amidolytic (VIIc/VIIam) activities. The ratio of unfractionated alveolar fluid was about 19, suggesting the presence of the more active two-chain F Vila. However, imnunoblots of concentrated lavage protein revealed only single-chain F VII and 125I-F VII added to the fluid was not converted to 125I-F VIIa. Additional studies showed that the enhanced PCA of lavage fluid F VII over that of plasma was due to a factor (s) in the sedimentable fraction of the lining layer which directly increased the prothrcmbinase activity of exogenous, purified factor Xa and V/Va and phospholipid (PL). Although normal alveolar macrophages express TF and F VTI, we estimate that the cells contribute < 15% of the total PCA within the alveolar compartment. However, these cells are the only suitable PL surface for prothrcmbinase complex formation within the lavage material, suggesting that macrophages are a major site for thrombin formation within alveoli. Thus, it appears the enhanced rates of thrombin formation rather than an increase in the rate of factor Xa generation explain the accelerated clotting times and the high F VIIc/VIIam ratio, and that macrophages may play a significant role in the total PCA output observed in the lung.
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Day, H. J., R. Cherrey, D. O'Hara, and J. Carabello. "INCIDENCE OF PROCAINAMIDE-INDUCED LUPUS ANTICOAGULANT." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644241.

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Isolated cases of lupus anticoagulants (LA) in association with procainamide have been reported. This study was done to estimate the frequency of LA in patients taking procainamide. Two groups of patients were evaluated: Group A: 110 hospitalized patients (84 males, 26 females, ages 51-78, mean age 74.3) and Group B: 80 ambulatory patients (54 males, 26 females, ages 36-89, mean 67.5 years). The latter group of patients was on this drug for a period of two-five years, while the former group hadbeen on drug at least two full days. All patients were screened with baseline laboratory data including activated partial thromboplastin time (APTT) and prothrombin time (PT) which were performed using Auto APTT® and Simplastin® on a Coagulamate X2® (General Diagnostics/Organon Teknika). Patients taking drugs known to alter the APTT and PT were excluded. All patients were followed with daily (hospital patients) or weekly (ambulatory patients) APTT and PT. Prolongation of the APTT of 5 sec or PT of 3 sec over baseline was considered as a positive LA screening test. Patients with a positive screening test were further evaluated with tissue thromboplastin inhibitor assay (TTI), platelet neutralization procedure (PNP, anti-nuclear antibodies (ANA) and blood serology (RPR). In Group A. 11 out of 110 (1096) developed prolonged APTT while on procainamide . Of these, 9 developed abnormal TTI and 2 had positive PNP. The ANA was positive (titers of 1:320-1:2560) in 10 patients with the only positive RPR test, being in the patient with the highest ANA titer. In Group B, 12 out of 80 (1596) developed prolonged APTT, 11 had positive TTI. The ANA titer was elevated in all positive cases, although one patient's titer was 1:30. The PNP was positive in 1/12. All blood serologies were negative in this group. The difference in incidence between Groups A and B may reflect longer exposure to drug in the latter group. This difference is not statistically significant. This study indicates that the incidence of procainamide-induced lupus antocoagulant is between 10-1596 when the APTT (or PT) is used as a screening test. The TTI and ANA seem to have equal sensitivity in this syndrome when taking this drug. The failure of the PNP to be sensitive to LA may be due to the minimal prolongation of the APTT arbitrarily chosen as representing a positive screening test.
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de Four, N. J., R. M. Bertina, and F. Havgrkate. "STIMULATION OF FIBRINOLYSIS BY ACTIVATED PROTEIN C (APC)." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642961.

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In 1960 Mammen and Seegers reported the discovery of a new protein (autoprothrombin II-A, APC) with both anticoagulant and profibrinolytic activity. They found that APC accelerated clot lysis in vitro and proposed that this was due to a reduction of plasmin - inhibitory activity. Many years later Comp et al (J Clin Inv 68: 1221) reported that the infusion of APC into dogs resulted in an increase in circulating plasminogen activator activity. This observation stimulated more extensive studies of the profibrinolytic effects of APC.In our laboratories we have studied the effect of human APC on clot lysis both in whole blood (human) and in a system of purified human proteins. In these systems 125I-labelled fibrinogen was incorporated in a clot formed after the addition of Jombin (complete clot formation within 5 min) and the subsequent lysis of this clot was followed by measuring the release of I-labelled fibrin degradation products (FDP) into the supernatant. Human t-PA was added to the system to achieve complete lysis of the clot within a few hours.When APC was added to citrated whole blood before clot formation, it was found to accelerate clot lysis in a dose dependent way. This effeg| was specific for APC and dependent on an intact active site, on the presence of protein S (the protein cofactor of APC) and Ca . The presence of APC did not influence the composition of the FDP formed, as analysed by means of SDS-polyacry-1 amide gel electroforesis, and its effect was found to be independent of the presence or absence of a.-antiplasmin.Subsequently we developped a clot lysis system using the purified human proteins of the fibrinolytic system: fibrinogen, FXIII, t-PA, PAI-1 (from human endothelial cells), glu-plasminogen and a -antiplasmin. In this system clot lysis was dependent on the concentrations of plasminogen, -antiplasmin, t-PA and PAI-1, but independent on the thrombin concentration and the presence or absence of phospholipids (purified from human brain). In the absence of PAI-1, no effect of APC on clot lysis was observed. However, in the presence of PAI-1, APC accelerated clot lysis. This effect was independent of the presence or absence of phospholipids and/or protein S and could be explained by the observation that APC can form a complex with PAI-1 (~ 95 kd) and under certain conditions even can convert active PAI-1 (~ 46 kd) into an inactive degradation product (~ 42 kd). However, complex formation is relatively slow anti high PAI-1 concentrations are needed to observe the reaction. The addition of protein S or phospholipids in the presence of Ca did not stimulate complex formation. Therefore, it seems highly unlikely that neutralization of PAI-1 by APC is responsible for the profibrinolytic effect of APC in the whole blood clot lysis.A completely different explanation for the profibrinolytic effect of APC was suggested by the observation that the addition of blood-platelets to the system of purified fibrinolytic components introduced a dependence of the clot lysis rate on the thrombin concentration (decrease in clot lysis at increasing thrombin concentration). This finding opened the possibility that APC stimulated fibrinolysis by reducing the effective thrombin concentration. Subsequent experiments using the whole blood clot lysis system revealed that in the presence of anti-FX antibodies clot lysis was no longer accelerated by APC, while the actual rate of clot lysis depended on the concentration of thrombin added.We like to propose, that in a blood clot lysis system APC most likely accelerates fibrinolysis by reducing the effective thrombin concentration; if at all, neutralization of PAI-1 may play only a minor role.
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