Academic literature on the topic 'Antigenic determinants'

The principal surface protein antigen of Chlamydia trachomatis is the major outer membrane protein (MOMP). The MOMP is antigenically complex. Among the 15 serovars of C. trachomatis, mAbs define serovar-, subspecies-, and species-specific determinants on MOMP. The molecular basis of the antigenic diversity of these proteins is reflected in amino acid variable sequence domains. We have mapped the dominant topographic antigenic determinants of MOMP that are defined by mAbs. Using recombinant DNA approaches we have identified the linear distribution of two antigenic domains. One domain contains a serovar-specific determinant and the other contains subspecies- and species-specific determinants. These antigenic domains correspond to two amino acid sequence variable domains. Synthetic peptides were immunogenic and these resolved the serovar-specific determinant within a 14-amino acid peptide. The subspecies- and species-specific determinants were overlapping within a 16-amino acid peptide.

Abstract Synthetic peptides, made by the method of simultaneous multiple peptide synthesis, were coupled to the protein carrier keyhole limpet hemocyanin and used to raise mAb. Omission and substitution analogs of the original peptides were tested by ELISA to characterize their reactivity with the respective mAb. Linear antigenic determinants were located for 18 different peptides by using omission analogs. The length of the antigenic determinants ranged from 2 to 8 residues, with an average of 6 residues. The three aromatic amino acids, phenylalanine, tryptophan, and tyrosine, the charged hydrophilic amino acids, aspartic acid and lysine, and the neutral amino acid alanine were found to occur most often in the determinant region of the peptides tested, whereas asparagine, cysteine, and histidine occurred the least often. Alanine substitution analogs provided more information than omission analogs by enabling the determination of which side chain groups of the antigenic determinant residues were not critical for binding to the mAb. Detailed, "fingerprint" information about the interaction of the peptide, GASPYPNLSNQQT, and its mAb was obtained by synthesizing a complete series of analogs with individual substitutions for each position of the antigenic determinant, PYPNLS, with the 19 other amino acids. These results suggest that, at the amino acid level, all antigenic determinants of synthetic peptides defined by mAb can be considered discontinuous linear determinants.

This paper describes an attempt to analyze, with the aid of bioinformatics resources (programs and databases), the probable cause of the cross-interaction of antibodies against HPV16 L1 with antigenic protein HPV6 L1, which has been revealed in the investigation of the candidate vaccine obtained on the base of a plant expression system (tomato plants). In our opinion, the most likely reason for the cross-interaction of antibodies with antigens of different pathogenic HPV types is the similarity of their antigenic determinants. In this work, the amino acid sequences of HPV16 L1 and HPV6 L1 used for the development of a binary vaccine against cervical cancer and anogenital papillomatosis have been analyzed. For the analysis of antigenic determinants, the programs BepiPred-2.0: Sequential B-Cell Epitope Predictor, DiscoTope 2.0 Server and SYFPEITHI have been used. As a result of the analysis of probable B-cell linear determinants (epitopes), it has been found that in both types of HPV the proteins have approximately the same location and size of linear antigenic determinants; the difference is observed only in the form of small shifts in the size of several amino acid residues. However, there are some differences in the amino acid composition of epitopes; therefore, the possibility for cross-interaction of the antibodies with the antigens due to the similarity of linear antigenic determinants for B-cells is very small. The analysis of potential threedimensional epitopes for B-cells has shown that due to little difference between them the HPV16 L1 and HPV6 L1 proteins have no prerequisites for cross-interaction of the antibodies with the antigens belonging to the two different pathogenic HPV types. The analysis of probable linear epitopes for T-cells has revealed a common antigenic determinant in the two protein sequences. According to the rank made with the SYFPEITHI program, the amino acid sequence AQL(I)FNKPYWL is the second most likely antigenic determinant for T-cells. Meanwhile, the amino acid sequences of this determinant in HPV16 L1 and HPV6 L1 are virtually identical. There is a difference in only one position, but it is not critical due to the similarity of the physicochemical properties of amino acids, for which there is a replacement in the amino acid sequence of antigenic determinants. Consequently, some moderate cross-interaction of the antibodies to HPV16 L1 with the antigens of HPV6 L1 may be expected.

An acidic lectin (WBA II) was isolated to homogeneity from the crude seed extract of the winged bean (Psophocarpus tetragonolobus) by affinity chromatography on lactosylaminoethyl-Bio-Gel. Binding of WBA II to human erythrocytes of type-A, -B and -O blood groups showed the presence of 10(5) receptors/cell, with high association constants (10(6)-10(8) M-1). Competitive binding studies with blood-group-specific lectins reveal that WBA II binds to H- and T-antigenic determinants on human erythrocytes. Affinity-chromatographic studies using A-, B-, H- and T-antigenic determinants coupled to an insoluble matrix confirm the specificity of WBA II towards H- and T-antigenic determinants. Inhibition of the binding of WBA II by various sugars show that N-acetylgalactosamine and T-antigenic disaccharide (Thomsen-Friedenreich antigen, Gal beta 1-3GalNAc) are the most potent mono- and di-saccharide inhibitors respectively. In addition, inhibition of the binding of WBA II to erythrocytes by dog intestine H-fucolipid prove that the lectin binds to H-antigenic determinant.

A panel of 11 rat monoclonal antibodies (mAbs) has been raised to ovine placental lactogen (PL). By competitive enzyme-linked immunoabsorbent assay (ELISA), confirmed by two-site ELISA, the antibodies were shown to recognize six antigenic determinants on the ovine PL molecule, two of which overlap. One antigenic determinant (designated 1) was shared by other members of the prolactin/growth hormone (GH)/PL family in ruminants, humans and rodents. The binding of (125)I-labelled ovine PL to crude receptor preparations from sheep liver (somatotrophic) or rabbit mammary gland (lactogenic) was inhibited by mAbs recognizing antigenic determinants 2-6. Both types of receptor preparation were affected similarly. In the local in vivo pigeon crop sac assay, mAbs directed against determinants 3 and 6 enhanced the biological activity of ovine PL.

Abstract The poor clinical response of 11q23-positive [also known as mixed lineage leukemia (MLL)] acute leukemia (AL) to chemotherapy-containing regimens has stimulated interest in developing alternative therapeutic strategies. Among them is immunotherapy. Since no leukemia-specific antigen has been identified in 11q23-positive AL, we are developing an antibody-based immunotherapeutic strategy which targets the HMW-MAA. This antigen, which is a membrane bound proteoglycan, represents an attractive target because of its high expression on the surface of 11q23-positive AL blasts and its restricted distribution in normal tissues. Taking advantage of a unique panel of monoclonal antibodies (mAb) recognizing 7 distinct and spatially distant antigenic determinants, we have analyzed the antigenic profile of HMW-MAA by flow cytometry in samples from 15 adult and 14 pediatric patients with 11q23-positive AL. Our results demonstrate a differential expression of the HMW-MAA antigenic determinants and that their expression pattern correlates with cytogenetic subgroups. Specifically, all the determinants were expressed on 6 adult samples [3 t(11;19)(q23;p13), 2 t(4;11)(q21;q23), and 1 t(10;11)(p12;q23)]. In contrast only 3 determinants were detected on 8 adult samples [3 t(9;11)(p22;q23), and 1 each with t(6;11)(q27;q23), t(11;12)(q23;q13), t(11;14)(q23;p11.2), inv(11)(q21q23.2) and add(11)(q23)]. No antigenic determinant was detected on leukemic cells from the adult patient with t(2;11)(p21;q23). Interestingly, the antigenic profile of HMW-MAA expressed on leukemic cells from pediatric patients was different, since all the determinants were expressed on leukemic cells from 6 t(4;11), 1 t(9;11), 1 t(11;1)(1;13;9)(q23;q25p34;q14.3;p13), 2 t(11;19) and 1 del(11)(q14q23). On the other hand no determinant was detectable on the leukemic cells from 3 children [1 with both t(1;11)(p32;q23) and t(4;11), 1 inv(11)(p15q23) and 1 add(11)(q23)]. Whether the difference in the antigenic profile of HMW-MAA expressed by adult and pediatric 11q23-positive AL cells reflects the different pathogenesis of AL in adults and children remains to be determined. Our data show that the differential expression of antigenic determinants of HMW-MAA on 11q23-positive AL cells does not reflect structural differences in the HMW-MAA expressed by various types of 11q23-positive AL as indicated by the results of Western blotting analysis. Further, the differential expression does not correlate with MLL gene rearrangement, since fluorescent in-situ hybridization (FISH) performed on 15 adult samples detected MLL gene rearrangement in 4 of the 6 samples that express all the determinants and in 6 of the 8 samples that express only 3 determinants. In addition, the pediatric sample with inv(11) that does not express any determinant, has MLL gene rearrangement by FISH. Finally, the differential expression does not correlate with the presence of MLL partial tandem duplication, since it was detected in 1 sample that expresses all the antigenic determinants and in 2 samples that express only 3 determinants. These findings emphasize the need to use more than one HMW-MAA-specific mAb to phenotype 11q23-positive AL and to select patients to be treated with HMW-MAA-specific antibody-based immunotherapy.

ABSTRACT The majority of group B streptococcus (GBS) isolates express one or more of a family of surface-anchored proteins that vary by strain and that form ladder-like patterns on Western blotting due to large repeat units. These proteins, which are important as GBS serotype markers and as inducers of protective antibodies, include the alpha C (Cα) and R4 proteins and the recently described alpha-like protein 2 (Alp2), encoded by alp2, and Alp3, encoded by alp3. In this study, we examined antigenic determinants possessed by Alp2 and Alp3 by testing of antibodies raised in rabbits, mainly by using enzyme-linked immunosorbent assays (ELISA) and an ELISA absorption test. The results showed that Alp2 and Alp3 shared an antigenic determinant, which may be a unique immunological marker of the Alp variants of GBS proteins. Alp2, in addition, possessed an antigenic determinant which showed specificity for Alp2 and a third determinant which showed serological cross-reactivity with Cα. Alp3, in addition to the determinant common to Alp2 and Alp3, harbored an antigenic site which also was present in the R4 protein, whereas no Alp3-specific antigenic site was detected. These ELISA-based results were confirmed by Western blotting and a fluorescent-antibody test. The results are consistent with highly complex antigenic structures of the alpha-like proteins in a fashion which is in agreement with the recently described structural mosaicism of the alp2 and alp3 genes. The results are expected to influence GBS serotyping, immunoprotection studies, and GBS vaccine developments.

Abstract Comparison of human and primate erythrocyte membrane sialoglycoproteins showed that common chimpanzee, dwarf chimpanzee, gorilla, orangutan, and gibbon have major periodic acid Schiff-positive proteins resembling human glycophorin A (GPA) monomer and dimer in electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels. Immunoperoxidase staining of Western blots with monoclonal antibodies to human GPA showed that these primate bands express some GPA antigenic determinants. A new sialoglycoprotein analogous to human glycophorin B (GPB) was detected in common chimpanzee. Although human MN blood group phenotype results from an amino acid polymorphism of GPA, Western blots showed that in chimpanzee sialoglycoprotein (GPAch) always expresses the M blood group, whereas chimpanzee sialoglycoprotein (GPBch) expresses either the N blood group or a null phenotype. This result explains the detection of M and MN, but not of N, blood group phenotypes in chimpanzee. GPBch has higher apparent m.w. than human GPB, is present in the erythrocyte membrane in greater quantity than human GPB, and contains trypsin cleavage site(s) and the 10F7 determinant (both found on human GPA but not GPB). Expression of human GPA antigenic determinants was consistent with the phylogeny of the hominoid primates; common and dwarf chimpanzee expressed most of the determinants tested, gorilla and orangutan an intermediate number, and gibbon and siamang the least. Of the GPA antigenic determinants examined, the MN blood group determinants were most consistently expressed during evolution of the hominoid primates. The results suggested that variability in expression of GPA antigenic determinants between species was due to both differences in amino acid sequence and glycosylation.

ABSTRACT Severe acute respiratory syndrome (SARS) is a life-threatening disease caused by a newly identified coronavirus (CoV), SARS-CoV. The spike (S) glycoprotein of CoV is the major structural protein responsible for induction of host immune response and virus neutralization by antibodies. Hence, knowledge of neutralization determinants on the S protein is helpful for designing protective vaccines. To analyze the antigenic structure of the SARS-CoV S2 domain, the carboxyl-terminal half of the S protein, we first used sera from convalescent SARS patients to test the antigenicity of 12 overlapping fragments spanning the entire S2 and identified two antigenic determinants (Leu 803 to Ala 828 and Pro 1061 to Ser 1093). To determine whether neutralizing antibodies can be elicited by these two determinants, we immunized animals and found that both of them could induce the S2-specific antisera. In some animals, however, only one determinant (Leu 803 to Ala 828) was able to induce the antisera with the binding ability to the native S protein and the neutralizing activity to the SARS-CoV pseudovirus. This determinant is highly conserved across different SARS-CoV isolates. Identification of a conserved antigenic determinant on the S2 domain of the SARS-CoV S protein, which has the potential for inducing neutralizing antibodies, has implications in the development of effective vaccines against SARS-CoV.