Anti-Hepatitis C Virus T-Cell Immunity in the Context of Multiple Exposures to the Virus
Katja PfafferottPooja DeshpandeE. McKinnonShahzma MeraniAndrew LucasDavid HeckermanS. MallalMina JohnSilvana GaudieriMichaela Lucas
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Abstract:
Characterisation of Hepatitis C virus (HCV)-specific CD8+ T-cell responses in the context of multiple HCV exposures is critical to identify broadly protective immune responses necessary for an effective HCV vaccine against the different HCV genotypes. However, host and viral genetic diversity complicates vaccine development. To compensate for the observed variation in circulating autologous viruses and host molecules that restrict antigen presentation (human leucocyte antigens; HLA), this study used a reverse genomics approach that identified sites of viral adaptation to HLA-restricted T-cell immune pressure to predict genotype-specific HCV CD8+ T-cell targets. Peptides representing these putative HCV CD8+ T-cell targets, and their adapted form, were used in individualised IFN-γ ELISpot assays to screen for HCV-specific T-cell responses in 133 HCV-seropositive subjects with high-risk of multiple HCV exposures. The data obtained from this study i) confirmed that genetic studies of viral evolution is an effective approach to detect novel in vivo HCV T-cell targets, ii) showed that HCV-specific T-cell epitopes can be recognised in their adapted form and would not have been detected using wild-type peptides and iii) showed that HCV-specific T-cell (but not antibody) responses against alternate genotypes in chronic HCV-infected subjects are readily found, implying clearance of previous alternate genotype infection. In summary, HCV adaptation to HLA Class I-restricted T-cell responses plays a central role in anti-HCV immunity and multiple HCV genotype exposure is highly prevalent in at-risk exposure populations, which are important considerations for future vaccine design.Keywords:
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Monoclonal antibody 2F5 recognizing the ELDKWA epitope on HIV-1 gp41 has a significant neutralization potency against 90% of the investigated viruses of African, Asian, American, and European strains, but the antibody responses to the epitope 2F5 in HIV-1-infected individuals were very low. We attempted to induce high levels of epitope-specific antibodies to ELDKWA and its three mutated epitopes by candidate epitope vaccines. The four candidate epitope vaccines all induced strong antibody responses at dilutions from about 1:6,400 to 1:25,600. We tested the cross-reactions between these antisera and four epitope peptides. The ELDKWA-specific antisera showed strong cross-reactivity with three neutralizing-resistant mutated epitopes which contain changes in the D or K positions of the epitope sequence. Virus variants containing these changes could escape neutralization by monoclonal antibody 2F5. In immunoblotting analysis, the ELDKWA, ELDEWA, and ELEKWA epitope specific antibodies all recognized rsgp41 which confirms that the antibodies against both mutated epitopes, ELDEWA and ELEKWA, could cross-react with the native epitope on rsgp41. Although it is not clear whether the polyclonal antibodies induced by the ELDKWA epitope vaccine could neutralize the mutated viruses containing these mutated epitopes, it is conceivable that epitope vaccines based on mutated epitopes could induce strong antibody responses with predefined epitope specificity to neutralize mutated viruse containing the mutated epitope. An epitope vaccine, using different epitopes including mutated epitopes, could provide a new concept for developing a new vaccine against HIV-1.
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Objective: To investigate the effect of enzyme-linked immunospot (ELISPOT) on accelerated co-cultured dendritic cells (acDCs) and direct detection of islet full-length antigen-specific T cell response in peripheral blood of patients with type 1 diabetes mellitus (T1DM). Methods: Sixteen patients with T1DM[9 males, 7 females, mean age(28.5±9.4)years] and 12 age-and sex-matched healthy controls were selected in the Department of Metabolism and Endocrinology, the Second Xiangya Hospital between March 2012 and August 2014. The numbers of IFN-γ secreting CD4(+)T cells responding to glutamic acid decarboxylase 65 (GAD(65)), C-peptide (CP) and insulin (INS) were detected by ELISPOT-acDCs and ELISPOT-direct assays, respectively. The positive rate of islet autoantigen and associated antigen reactive T cells under different detection assays were compared. Results: The positive rate for GAD(65), INS, and CP antigen reactive T cells detected by ELISPOT-acDCs was 1/16, 6/16 and 4/16, respectively, and T cells positive for INS in T1DM patients were higher than that in the controls (0/12) (P=0.024). Combining GAD(65), CP and INS-ELISPOT-acDCs detection, the positive rate for CD4(+) T cells in T1DM patients was higher than that in the controls (9/16 vs 1/12, P=0.016). The positive rate for GAD(65), INS, and CP antigen reactive T cells detected by ELISPOT-direct detection was 2/16, 1/16 and 7/16, respectively, and T cells positive for CP was higher than that in the controls (1/12), but the difference was not statistically significant (P=0.088). Likewise, the positive rate for CD4(+) T cells was higher in T1DM patients than that in the controls by combined GAD(65), CP and INS-ELISPOT-direct detection (8/16 vs 1/12, P=0.039). Compared with the ELISPOT-direct assay, the positive rate of INS antigen specific T cell response detected by ELISPOT-acDCs was higher (P=0.041). No statistical differences of other antigens were found between the two groups (all P>0.05). Conclusions: Both multiple islet antigens-combined CD4(+)-ELISPOT-acDCs and direct assays could provide diagnostic value of cellular immunology for T1DM patients. The ELISPOT-acDCs assay is superior to the ELISPOT-direct assay in the detection of INS antigen-specific T cell response.目的： 探讨酶联免疫斑点（ELISPOT）加速树突状细胞成熟的预孵育法（acDCs）和直接检测法检测1型糖尿病（T1DM）患者外周血中胰岛全长抗原特异性T细胞反应的优劣。 方法： 选取2012年3月至2014年8月中南大学湘雅二医院代谢内分泌科就诊的T1DM患者16例（男9例，女7例），年龄（28.5±9.4）岁，病程6.0（2.8~8.3）个月；另纳入年龄、性别匹配的健康对照12名；ELISPOT-acDCs法和直接检测法检测3种胰岛抗原谷氨酸脱羧酶65（GAD(65)）、C肽、胰岛素（INS）特异性干扰素-γ（IFN-γ）分泌性CD4(+) T细胞反应的斑点数，比较不同检测方法下各种胰岛抗原及联合3种抗原特异性T细胞反应的阳性比例。 结果： ELISPOT-acDCs法检测T1DM患者GAD(65)特异性IFN-γ分泌性CD4(+) T细胞反应的阳性比例为1/16，INS反应阳性比例为6/16，C肽反应阳性比例为4/16，其中INS反应阳性比例高于健康对照组的0/12（P=0.024）；联合3种抗原的T细胞阳性比例为9/16，明显高于健康对照组的1/12（P=0.016）。ELISPOT直接法检测GAD(65)特异性T细胞反应阳性比例为2/16，INS反应阳性比例为1/16，C肽反应阳性比例7/16，其中C肽反应阳性比例高于健康对照组的1/12，但差异无统计学意义（P=0.088）。联合3种抗原检测T细胞反应阳性比例8/16，高于健康对照组的1/12（P=0.039）；与直接法比较，仅acDCs法检测下的INS特异性T细胞反应阳性比例较高（P=0.041）；两种方法在余各抗原间比较差异均无统计学意义（均P>0.05）。 结论： 多种全长胰岛抗原ELISPOT-acDCs法及直接法检测胰岛抗原特异性T细胞反应均可为T1DM患者提供细胞免疫学分型诊断价值；ELISPOT-acDCs法检测INS特异性T细胞反应的灵敏度优于ELISPOT直接检测法。.
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In conclusion, this case provided a unique illustration of de novo production of DSA following transplant from an HLA-A, -B, and -DR matched donor (eliminating the masking effect of these potential mismatches). The antibody generated could be tracked down not only to the allele level of the mismatched HLA antigen but also to the exact epitope that was conceived immunogenic by the recipient. Identifying this epitope also explained the presence of the additional non-donor-specific antibodies (NDSAs) that are actually the same antibody recognizing a shared epitope by multiple HLA-DP alleles. Finally, this information provided valuable information for selecting the most suitable donor for this patient. The concept of shared epitopes was first described by Parham et al. in 1980, and it was revisited recently by Piazza et al. This concept was further developed into a proposal for epitope matching rather than the conventional antigen matching. A simplified algorithm has been developed and implemented by Duquesnoy. The case presented in this manuscript provides a "poster child" example for the role of epitope matching. It is time that the community re-evaluates our nomenclature and scientific reasoning. Current nomenclature stems from historic events that led to the discovery of the HLA system. However, once molecular sequences and 3D structures of the HLA molecules have been elucidated and interactions between the HLA molecules and T-cell receptors have been deciphered, reclassification of the HLA system based on immunogenic epitopes is warranted.
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Epitope-vaccine is a newly developing vaccine which has many advantages comparied with to the traditional vaccine.The key step for designing epitope-vaccine is to screen epitopes.The epitope-screening methods include protein degration,peptide-probing scanning,epitope prediction by computer,et al.Usually,the epitope-vaccine needs combine some carriers to display immunologic activity,for example,lipid carriers,protein carriers,and adjuvant.In addition,researchers also use tandem repeat epitopes,conformational multiple antigen peptide(MAP) and epitope modifying to strengthen the immunological efficacity.The epitope-vaccine mainly contains viral epitope-vaccine,bacterial epitope-vaccine and epitope-vaccine for parasites.Although the researches on epitope-vaccine develop fast,some problems and challenges need to resolve impendingly.
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The interferon (IFN)-gamma enzyme-linked immunospot (ELISPOT) assay has become a useful tool for immunologists seeking to quantify immune responses on a per-cell basis. The assay is sensitive and allows for the enumeration of low-frequency T-cells. Many have applied this assay to clinical trials as a way to measure biological activity in a patient cohort. It is critical that each laboratory attempting to use the assay in their facility perform rigorous development and qualification work to establish an assay that suits their particular needs. This chapter serves as a demonstration of two practical and slightly different approaches to using the ELISPOT assay to monitor immune activity in the human periphery: (1) assays using whole samples of peripheral blood mononuclear cells with and without the use of additional antigen presenting cells and (2) assays using enriched T-cell populations. Detailed protocols and procedures will be covered, as well as a demonstration of results obtained from three separate applications.
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OBJECTIVE—To investigate the prevalence of β-cell autoantigen-reactive peripheral T-cells in type 1 diabetes, we developed an immunoglobulin-free enzyme-linked immunospot (ELISPOT) assay and assessed its usefulness for diagnosing this disease. RESEARCH DESIGN AND METHODS—Cellular immune responses to β -cell autoantigens were studied both by immunoglobulin-free proliferation assays and ELISPOT assays in 33 patients with type 1 diabetes and 15 patients with type 2 diabetes, compared with 23 healthy control subjects. Autoantibodies against GAD65 and IA-2 were measured by radioimmunoassay. RESULTS—Significant proliferative responses to GAD65 were observed in 10 of 31 (32.3%) type 1 diabetic patients (P < 0.05), whereas GAD65-reactive γ-interferon (IFN-γ)-secreting cells were detected in 22 of 33 patients (66.7%) by ELISPOT assay (P < 0.001). Of patients negative for both GAD65 and IA-2, five of six (83.3%) showed IFN-γ positivity in ELISPOT and two of five (40.0%) showed significant proliferation against GAD65. CONCLUSIONS—Using a newly developed ELISPOT assay, GAD-reactive T-helper 1 cells in PBMC of type 1 diabetic patients could be identified at a higher frequency than by the proliferation assay. Therefore, the immunoglobulin-free ELISPOT assay is an excellent tool for detecting T-cell reactivity to autoantigens with greater specificity and, in combination with β-cell autoantibody determination, will improve the diagnosis of type 1 diabetes.
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Bovine herpesvirus 1
Epitope mapping
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