A novel cytotoxic T-cell epitope presented by HLA-A24 molecule in hepatitis C virus infection

Therapeutic vaccines against hepatitis C virus

Hepatitis C virus (HCV) is a blood-borne pathogen which has chronically infected about 130-210 million people worldwide. Current standard-of-care (SoC) therapy is an inadequate and expensive treatment with more side effects. Two direct-acting antiviral agents (DAAs) (telaprevir and boceprevir) in combination with SoC therapy have been used in patients infected with HCV genotype 1. Although these drugs result in a shortening of therapy, they also have additional side effects and are expensive. In their stead, several second-generation DAAs are being investigated. What important is that all-oral, interferon (IFN)- and ribavirin-free regimens for the treatment of HCV-infected patients are now being investigated, and will be applied in the next year. Preventive measures against HCV, including vaccine development, are also now in progress. However, no therapeutic vaccine against HCV has been produced to date. An effective vaccine should induce robust and broadly cross-reactive CD4(+), CD8(+)T-cell and neutralising antibody (NAb) responses. Current data indicate that vaccines can usually not completely prevent HCV infection but rather prevent the progression of HCV infection to chronic and persistent infection, which may be a realistic goal. This review discusses the important roles of NAbs and CD8(+)T-cells in the development of therapeutic vaccines, and summarizes some important epitopes of HCV recognized by CD8(+)T-cells and some prospective therapeutic vaccine approaches.

Antibody Reactive to a Hepatitis C Virus (HCV)-Derived Peptide Capable of Inducing HLA-A2 Restricted Cytotoxic T Lymphocytes Is Detectable in a Majority of HCV-Infected Individuals without HLA-A2 Restriction

Hepatitis C virus (HCV) is a single-strand RNA virus. Approximately 170 million people around the world are persistently infected and are at risk of liver cirrhosis or cancer. There is an urgent need to develop both therapeutic and diagnostic modalities of HCV. One approach to achieve these goals would be to determine highly immunodominant HCV peptides which are recognized by both cellular and humoral immunities. This study reports one such peptide, HCV-core protein at positions 35-44, having HLA-A2 binding motifs. IgG specific to this CTL-epitope peptide is consistently detectable in a majority of the patients with HCV infection regardless of the different HLA types, different disease conditions, and different HCV-genotypes tested. The sequence LPRR at positions 37-40 is considered to be the fine epitope recognized by the IgG. These results may provide new insights for the development of both therapeutic and diagnostic modalities of HCV at lower costs.

Comparative analysis of various tumor-associated antigen-specific t-cell responses in patients with hepatocellular carcinoma

Many tumor-associated antigens (TAAs) recognized by cytotoxic T cells (CTLs) have been identified during the last two decades and some of them have been used in clinical trials. However, there are very few in the field of immunotherapy for hepatocellular carcinoma (HCC) because there have not been comparative data regarding CTL responses to various TAAs. In the present study, using 27 peptides derived from 14 different TAAs, we performed comparative analysis of various TAA-specific T-cell responses in 31 HCC patients to select useful antigens for immunotherapy and examined the factors that affect the immune responses to determine a strategy for more effective therapy. Twenty-four of 31 (77.4%) HCC patients showed positive responses to at least one TAA-derived peptide in enzyme-linked immunospot assay. The TAAs consisting of cyclophilin B, squamous cell carcinoma antigen recognized by T cells (SART) 2, SART3, p53, multidrug resistance-associated protein (MRP) 3, alpha-fetoprotein (AFP) and human telomerase reverse transcriptase (hTERT) were frequently recognized by T cells and these TAA-derived peptides were capable of generating peptide-specific CTLs in HCC patients, which suggested that these TAAs are immunogenic. HCC treatments enhanced TAA-specific immune responses with an increased number of memory T cells and induced de novo T-cell responses to lymphocyte-specific protein tyrosine kinase, human epidermal growth factor receptor type 2, p53, and hTERT. Blocking cytotoxic T-lymphocyte antigen-4 (CTLA-4) resulted in unmasking of TAA-specific immune responses by changing cytokine and chemokine profiles of peripheral blood mononuclear cells stimulated by TAA-derived peptides.

CONCLUSION

Cyclophilin B, SART2, SART3, p53, MRP3, AFP, and hTERT were immunogenic targets for HCC immunotherapy. TAA-specific immunotherapy combined with HCC treatments and anti-CTLA-4 antibody has the possibility to produce stronger tumor-specific immune responses.

Human leukocyte antigen alleles and the response to pegylated interferon/ribavirin therapy in chronic hepatitis C patients

Human leukocyte antigens (HLAs) may play a role in the clinical evolution of hepatitis C virus (HCV) infection. The present study was aimed at elucidating the association between the HLA loci and responses to combination therapy with pegylated interferon-alpha 2a (PEG-IFN) and ribavirin in Taiwanese. We enrolled a total of 208 treatment-naïve Taiwanese chronic hepatitis C (CHC) patients treated with combination therapy. Patients with sustained virological response (SVR) had a significantly higher frequency of genotype non-1b infection, lower pretreatment HCV RNA levels and a higher frequency of mild hepatic fibrosis (fibrosis score: F: 0-2). The HLA A24 and B40 alleles were significantly associated with SVR after adjusted for the other three confounding factors including HCV genotype, hepatic fibrosis and pretreatment serum HCV RNA levels. Haplotypes (B40-DRB1*3, B46- DRB1*9, Cw1- DQB1*3, and Cw1- DRB1*9) were significantly associated with SVR to combination therapy. For 167 patients with genotype 1b infection and viral load < or =5.6 logIU/ml or genotype non-1b infection, the B46 was significantly associated with sustained response with OR (odds ratio) [95% CI (confidence interval) of 0.047 (0.168-0.988)]. Haplotypes B40-DRB1*3, B46- DRB1*9, Cw1- DQB1*3, Cw1- DRB1*9 and DQB1*3- DRB1*9 were found to be associated with SVR to PEG-IFN/ribavirin therapy with OR (95% CI) of 0.179 (0.032-0.989), 0.313 (0.107-0.918), 0.350 (0.145-0.845), 0.282 (0.105-0.759) and 0.412 (0.174-0.978), respectively. We concluded that the virological and the host immunogenetic factors may possibly predict the response to combination therapy in CHC patients.

A new epitope peptide derived from hepatitis C virus 1b possessing the capacity to induce cytotoxic T-lymphocytes in HCV1b-infected patients with HLA-A11, -A31, and -A33

BACKGROUND

Hepatitis C virus (HCV) frequently causes chronic hepatitis, cirrhosis, and hepatocellular carcinoma after long-term persistent infection. Among various genotypes of HCV, HCV1b is resistant to standard interferon therapy, and thus the development of new treatment modality is needed.

RESULTS

To provide a scientific basis for specific immunotherapy for HCV1b, we investigated HCV1b-derived epitope peptides recognized by human leukocyte antigen (HLA)-A11, -A31, or -A33-restricted cytotoxic T-lymphocytes (CTLs), and report here three novel vaccine candidate peptides selected by both antibody screening and CTL-inducing capacity from among 46 peptides of conserved regions of HCV1b sequences with binding motifs to HLA-A11, -A31, and -A33. Significant levels of IgG reactive to each of the three peptides were detected in the plasma of more than 50% of the HCV1b(+) patients. One peptide at positions 30-39 of the core protein induced peptide-specific CTLs from peripheral blood mononuclear cells (PBMCs) of HLA-A11(+), -A31(+), and -A33(+) patients. The other two peptides at positions 35-43 of the core protein and at positions 918-926 of the non-structural protein 2 also induced peptide-specific CTLs from the PBMCs of HLA-A11(+) and -A33(+) patients.

CONCLUSION

Therefore, the peptide at positions 30-39 of the core protein could be an appropriate target molecule of specific immunotherapy for all HLA-A11(+), -A31(+), and -A33(+) patients with HCV1b-related diseases.

Phase I clinical study of a personalized peptide vaccination for patients infected with hepatitis C virus (HCV) 1b who failed to respond to interferon-based therapy

To assess the safety and immune responses to a personalized peptide vaccination of hepatitis C virus (HCV) 1b-derived peptides, 12 HCV1b-positive patients, who were unresponsive to interferon-based therapy, were enrolled in this study. The reactivity of the pre-vaccination peripheral blood T cells and plasma IgG to four vaccine candidate peptides capable of inducing cytotoxic T lymphocytes (CTLs) in HLA-A24(+) patients was examined and only the reactive peptides were then administered bi-weekly at three different dose settings. The study was well tolerated with no severe toxicity. Augmentation of peptide-specific CTL activity and IgG in response to at least one of the vaccinated peptides was observed after the 7th vaccination. Decrease of serum alanine aminotransferase and HCV-RNA levels after the 14th vaccination was also observed in five and three patients, respectively.

Cancerogenic effect of different fragments of the hepatitis C virus core protein

The hepatitis C virus core protein plays an extremely important role in the hepatocarcinogenesis of hepatitis C virus. Little, however, is known about the oncogenic potency of fragments. Thus, the purpose of the present study is to investigate the cancerogenic effects of the different core protein fragments. Two series of recombinant plasmids containing hepatitis C virus core gene fragments encoding the different-length core protein were constructed using plasmid enhanced green fluorescent protein (pEGFP)-C1 and pcDNA3.1(+), respectively. Human hepatocyte L02 cells transiently transfected with pEGFP-C1-based plasmids were subjected to confocal laser scanning microscopy analysis to determine the localization of the different core protein fragments. The stably transfected L02 cells with the pcDNA3.1(+)-based core protein plasmids were used to investigate the ultrastructural effects of the core protein and the tumorigenicity of L02 cells expressing core protein fragments in athymic nude mice. The full-length core protein and Core130-191 were completely localized in the cytoplasm, while Core1-59 existed exclusively in the nucleus. On the other hand, Core50-140 and Core1-140 were observed in both the nucleus and the cytoplasm. Ultrastructural changes of L02 cells expressing the full-length core protein were comprehensive and included, for example, irregular nuclear, increased nuclear/cytoplasmic ratio and mitochondria swelling. The slight changes were observed in the cells expressing Core50-140 and Core130-191, whereas the ultrastructure of the cells expressing Core1-59 remained normal. All the L02 cells stably expressing different fragments of the core protein, with the exception of the C-terminal truncated fragment Core1-59, could induce the occurrence of tumor in the nude mice. The N-terminal fragment of the core protein, Core1-59, was not oncogenic, while the intermediate and posterior segments of the hepatitis C virus core protein had the cancerogenic potency. In view of the existence of many important immunogenic epitopes in it, the core protein anterior segment might be a safer candidate for the development of hepatitis C virus vaccine.

Identification of new immunogenic peptides in conserved regions of hepatitis C virus (HCV) 1b with the potentiality to generate cytotoxic T lymphocytes in HCV1b(+) HLA-A24(+) patients

AIM

Hepatitis C virus (HCV) 1b is resistant to standard interferon therapy and has a high risk of developing into hepatocellular carcinoma at the late stage of infection. Therefore, new therapeutic modalities for HCV1b infection must be developed. One approach would be active specific immunotherapy with highly immunogenic HCV1b peptides.

METHODS

HCV1b-derived 44 synthetic peptides were selected based on their binding scores to HLA-A24. Peptide-specific IgG were measured by ELISA. Peptide-specific cytotoxic T-lymphocytes (CTLs) were induced in vitro by repeated peptide-stimulation.

RESULTS

We identified three novel candidate peptides of HCV1b proteins containing HLA-A24 binding motifs. Each of them had the ability to induce HLA-A24-restricted and peptide-specific CTL activity, and IgGs specific to each of them were detected in the plasma of HCV1b patients. Among these three peptides, a peptide NS5A 2132-2142 was recognized by both cellular and humoral immunities in the majority of blood samples of patients tested. More importantly, the peptide-stimulated peripheral blood mononuclear cells (PBMCs) showed cytotoxicity against cells cotransfected with NS5A and HLA-A2402 genes in an HLA-restricted manner. This is an additional report to our previous study.

CONCLUSION

These findings may provide a new insight into the development of a peptide-based specific immunotherapy for HCV1b-infected patients.

CD8+ T lymphocytes infiltrate predominantly in the inflammatory foci of MPO-ANCA-positive thoracic hypertrophic pachymeningitis in a patient with HLA-A24

Hypertrophic pachymeningitis (HP) is extremely rare and an inflammatory process that thickens the dura mater. A 59-year-old Japanese woman developed backache, became paraplegic, and magnetic resonance imaging revealed diffuse thickening of the thoracic dura mater encompassing the spinal cord. Although a test for myeloperoxidase antineutrophil cytoplasmic autoantibody (MPO-ANCA) was shown to be positive, vasculitis was not found and CD8(+) T lymphocytes that predominated in the inflammatory foci. Both interleukin (IL)-2 and IL-6 were markedly elevated in not only sera but also cerebrospinal fluids, very much higher in the latter. Human leukocyte antigen (HLA) typing revealed A24 positivity, suggesting this molecule was interacting with CD8(+) T lymphocytes. It was suggested that immunological disharmony and autoimmunity would play a pivotal role in the development of HP under genetic background of HLA-A24, and HP would be one feature of multiple organ involvement in ANCA-associated diseases.

Identification of CTL epitopes in hepatitis C virus by a genome-wide computational scanning and a rational design of peptide vaccine

Developing a peptide-based vaccine for the highly variable hepatitis C virus (HCV) remains a challenging task. Variant viruses not only escape antigen presentation but also persist in a patient as quasi-species. Such variants are often antagonistic to the responding T cell repertoire. To overcome these problems, we herein propose a cocktail vaccine consisting of a few epitope peptides, which make it possible to outpace the emergence of variant viruses. To design such a vaccine, we developed a way to identify HLA-A*2402-binding peptides efficiently by means of the computational scanning of the whole genome of the pathogen. Most of the predicted peptides exhibited strong binding to the HLA-A*2402 molecule, while also inducing CD8 T cell responses from the patients' peripheral blood mononuclear cells (PBMCs). Peptide-induced T cells were capable of lysing HCV-expressing HepG2 cells which process antigens endogenously. The amount of HCV core antigen in the patients' livers suggested that the lytic activity of the peptide-induced T cells was clearly in a range suitable for therapeutic use. If T cells were activated under optimal conditions by high density peptides, then they tended to be relatively tolerant of single amino acid variations for cytolysis. Finally, an analysis of the viral population isolated in Japan suggested no obvious changes due to immune evasion in the viral genome even in a host population highly biased toward HLA-A*2402.

Identification of hepatitis C virus (HCV) 2a-derived epitope peptides having the capacity to induce cytotoxic T lymphocytes in human leukocyte antigen-A24+ and HCV2a-infected patients

Since virus-specific cytotoxic T lymphocytes (CTLs) play a critical role in preventing the spread of hepatitis C virus (HCV), vaccine-based HCV-specific CTL induction could be a promising strategy to treat HCV-infected patients. In this study, we tried to identify HCV2a-derived epitopes, which can induce human leukocyte antigen (HLA)-A24-restricted and peptide-specific CTLs. Peripheral blood mononuclear cells of HCV2a-infected patients or healthy donors were stimulated in vitro with HCV2a-derived peptides, which were prepared based on the HLA-A24 binding motif. As a result, three peptides (HCV2a 576-584, HCV2a 627-635, and HCV2a 1085-1094) efficiently induced peptide-specific CTLs from HLA-A24(+) HCV2a-infected patients as well as healthy donors. The cytotoxicity was exhibited by peptide-specific CD8(+) T cells in an HLA-A24-restricted manner. In addition, the HCV2a 627-635 peptide was frequently recognized by immunoglobulin G of HCV2a-infected patients. These results indicate that the identified three HCV2a peptides might be applicable to peptide-based immunotherapy for HLA-A24(+) HCV2a-infected patients.

Identification of novel hepatitis C virus-specific cytotoxic T lymphocyte epitopes by ELISpot assay using peptides with human leukocyte antigen-A*2402-binding motifs

The human leukocyte antigen (HLA)-A*2402 is common in Asians. The authors attempted to identify epitopes for HLA-A*2402-restricted, hepatitis C virus (HCV)-specific CD8+ T cells by an enzyme-linked immunospot (ELISpot) assay using peripheral blood CD8+ T cells from HLA-A*2402-positive hepatitis C patients and synthetic HCV peptides based on HLA-A*2402-binding motifs and the amino acid sequence of type 1b HCV. Ten novel epitopes were identified in five of seven HLA-A*2402-positive patients with acute or short-term chronic HCV infection (<3 years), but in none of four with longer-term chronic infection (>10 years). Only one of the ten epitopes proved to be definitely HLA-A*2402-restricted. Another epitope was identified in one of two HLA-A*2402-negative acute hepatitis C patients. In two of the six patients with positive CD8+ T cell responses, the targeted epitopes were multiple. The same epitope was targeted in two patients. When patients with unresolved acute HCV infection were treated with alpha interferon, peripheral blood HCV-specific CD8+ T cells decreased with resolution of the hepatitis. In conclusion, CD8+ T cell responses to HCV infection are heterogeneous. One definite HLA-A*2402-restricted and ten probably non-HLA-A*2402-restricted epitopes were identified. Patients with short-term HCV infection are suitable for searching for novel HCV epitopes, but peripheral blood HCV-specific CD8+ T cells decrease markedly after loss of antigenic stimulation.

Comprehensive analysis of CD8(+)-T-cell responses against hepatitis C virus reveals multiple unpredicted specificities

The hepatitis C virus (HCV)-specific CD8(+)-T-cell response is thought to play a critical role in HCV infection. Studies of these responses have largely relied on the analysis of a small number of previously described or predicted HCV epitopes, mostly restricted by HLA A2. In order to determine the actual breadth and magnitude of CD8(+)-T-cell responses in the context of diverse HLA class I alleles, we performed a comprehensive analysis of responses to all expressed HCV proteins. By using a panel of 301 overlapping peptides, we analyzed peripheral blood mononuclear cells (PBMC) from a cohort of 14 anti-HCV-positive, HLA A2-positive individuals in an enzyme-linked immunospot assay. Only four subjects had detectable HLA A2-restricted responses in PBMC, and only 3 of 19 predicted A2 epitopes were targeted, all of which were confirmed by tetramer analysis. In contrast, 9 of 14 persons showed responses with more comprehensive analyses, with many responses directed against previously unreported epitopes. These results indicate that circulating HCV-specific CD8(+)-T-cell responses can be detected in PBMC in the majority of infected persons and that these responses are heterogeneous with no immunodominant epitopes consistently recognized. Since responses to epitopes restricted by single HLA alleles such as HLA A2 do not predict the overall response in an individual, more comprehensive approaches, as shown here, should facilitate definition of the role of the CD8(+)-T-cell response in HCV infection. Moreover, the low level or absence of responses to many predicted epitopes provides a rationale for immunotherapeutic interventions to broaden cytotoxic-T-lymphocyte recognition.

Cellular immune responses against hepatitis C virus: the evidence base 2002

Hepatitis C virus (HCV) is an RNA virus which is estimated to persistently infect about 170 million people worldwide. After acute infection, there is an initial period during which long-term outcome is decided. There is strong evidence that the cellular immune responses, involving both CD4+ and CD8+ T lymphocytes, are involved at this stage and it is their effectiveness which determines outcome. What is not understood is what determines their effectiveness. The most important component of this is likely to be some aspect of epitope selection, itself dictated by host MHC. Thus, to understand host immunity to HCV, we need to have a detailed understanding of the peptides involved in T lymphocyte responses. In this review, we discuss the peptide epitopes that have been identified so far, and their potential significance. We relate this to a scheme of host defence which may be useful for understanding natural and vaccine-induced immunity.