Relation between viral fitness and immune escape within the hepatitis C virus protease

BACKGROUND: The hepatitis C virus (HCV) mutates within human leucocyte antigen (HLA) class I restricted immunodominant epitopes of the non-structural (NS) 3/4A protease to escape cytotoxic T lymphocyte (CTL) recognition and promote viral persistence. However, variability is not unlimited, and sometimes almost absent, and factors that restrict viral variability have not been defined experimentally. AIMS: We wished to explore whether the variability of the immunodominant CTL epitope at residues 1073-1081 of the NS3 protease was limited by viral fitness. PATIENTS: Venous blood was obtained from six patients (four HLA-A2+) with chronic HCV infection and from one HLA-A2+ patient with acute HCV infection. METHODS: NS3/4A genes were amplified from serum, cloned in a eukaryotic expression plasmid, sequenced, and expressed. CTL recognition of naturally occurring and artificially introduced escape mutations in HLA-A2-restricted NS3 epitopes were determined using CTLs from human blood and genetically immunised HLA-A2-transgenic mice. HCV replicons were used to test the effect of escape mutations on HCV protease activity and RNA replication. RESULTS: Sequence analysis of NS3/4A confirmed low genetic variability. The major viral species had functional proteases with 1073-1081 epitopes that were generally recognised by cross reactive human and murine HLA-A2 restricted CTLs. Introduction of mutations at five positions of the 1073-1081 epitope prevented CTL recognition but three of these reduced protease activity and RNA replication. CONCLUSIONS: Viral fitness can indeed limit the variability of HCV within immunological epitopes. This helps to explain why certain immunological escape variants never appear as a major viral species in infected humans.     

Epitope discovery in West Nile virus infection: Identification and immune recognition of viral epitopes

Cytotoxic T lymphocytes (CTL) play an important role in the control and elimination of infection by West Nile virus (WNV), yet the class I human leukocyte antigen (HLA)-presented peptide epitopes that enable CTL recognition of WNV-infected cells remain uncharacterized. The goals of this work were first to discover the peptide epitopes that distinguish the class I HLA of WNV-infected cells and then to test the T cell reactivity of newly discovered WNV epitopes. To discover WNV-immune epitopes, class I HLA was harvested from WNV (NY99 strain)-infected and uninfected HeLa cells. Then peptide epitopes were eluted from affinity-purified HLA, and peptide epitopes from infected and uninfected cells were comparatively mapped by mass spectroscopy. Six virus-derived peptides from five different viral proteins (E, NS2b, NS3, NS4b, and NS5) were discovered as unique to HLA-A*0201 of infected cells, demonstrating that the peptides sampled by class I HLA are distributed widely throughout the WNV proteome. When tested with CTL from infected individuals, one dominant WNV target was apparent, two epitopes were subdominant, and three demonstrated little CTL reactivity. Finally, a sequence comparison of these epitopes with the hundreds of viral isolates shows that HLA-A*0201 presents epitopes derived from conserved regions of the virus. Detection and recovery from WNV infection are therefore functions of the ability of class I HLA molecules to reveal conserved WNV epitopes to an intact cellular immune system that subsequently recognizes infected cells.     

Sequence evolution of putative cytotoxic T cell epitopes in NS3 region of hepatitis C virus

AIM: Quasispecies of hepatitis C virus (HCV) are the foundation for rapid sequence evolution of HCV to evade immune surveillance of hosts. The consensus sequence evolution of a segment of HCV NS3 region, which encompasses putative cytotoxic T cell epitopes, was evaluated. METHODS: Three male patients, infected with HCV through multiple transfusions, were identified from clinical symptoms and monitored by aminotransferase for 60 months. Blood samples taken at months 0, 32, and 60 were used for viral RNA extraction. A segment of HCV NS3 region was amplified from the RNA extraction by RT-PCR and subjected to subcloning and sequencing. HLA types of these three patients were determined using complement-dependent microlymphocytotoxic assay. CTL epitopes were predicted using MHC binding motifs. RESULTS: No patient had clinical symptoms or elevation of aspartate/alanine aminotransferase. Two patients showed positive HCV PCR results at all 3 time points. The other one showed a positive HCV PCR result only at month 0. A reported HLA-A2-restricted CTL epitope had no alteration in the HLA-A2-negative carrier over 60 months. In the HLA-A2-positive individuals, all the sequences from 0 month 0 showed an amber mutation on the initial codon of the epitope. Most changes of consensus sequences in the same patient occurred on predicted cytotoxic T cell epitopes. CONCLUSION: Amber mutation and changes of consensus sequence in HCV NS3 region may be related to viral immune escape.     

丙型肝炎病毒多CTL表位树突状细胞疫苗的构建及体外刺激T细胞应答

目的构建丙型肝炎病毒（HCV）多细胞毒性T淋巴细胞（CTL）表位树突状细胞（DC）疫苗,观察其体外刺激的T细胞反应,为下一步做体内免疫实验提供一定的资料。方法构建和制备出含绿色荧光蛋白（GFP）标签的HCV两个CTL表位的重组腺病毒,感染DC,直接在荧光显微镜下或用流式细胞仪检测其感染率;RT-PCR和Western Blot方法检测HCV多CTL表位的表达。流式细胞术分析感染前后DC的CD80、CD83、CD86和人类白细胞抗原（HLA）-DR的表达,CCK-8法观察感染重组腺病毒的DC促进T细胞的增殖效应。ELISA检测重组腺病毒刺激后的DC培养上清液内白细胞介素（IL）-12及DC和T细胞混合培养上清液内干扰素（IFN）-γ的含量。用乳酸脱氢酶（LDH）释放法检测特异性CTL的杀伤活性。结果成功构建含GFP标签的HCV多CTL表位的重组腺病毒,并在DC中表达。重组腺病毒能促进DC成熟,DC的CD80、CD83、CD86和HLA-DR的表达分别为（71.19±3.29）%、（81.21±5.07）%、（91.23±4.24）%、（97.95±5.31）%。感染DC后促进同源T细胞增殖,DC：T为1：10时增殖指数为6.806±0.247。分泌的IL-12和IFN-γ也明显增多,分别达到（193.83±6.25）pg/ml和（111.14±2.09）pg/ml。感染DC刺激的CTL能特异性杀伤转染FL-J6/JFH的Huh-7.5细胞,当效靶比为100：1时,AD1-DC-L的杀伤率为35.99%。结论重组多CTL表位腺病毒在体外能有效感染DC,促进了T细胞反应,为下一步抗HCV的DC疫苗研制打下基础。     

人白细胞抗原-A*0201限制性丙型肝炎病毒细胞毒性T淋巴细胞表位的鉴定

目的 鉴定人白细胞抗原(HLA)-A*0201限制性HCV-CTL表位.方法 基于RANKpep和SYFPEITHI细胞表位预测软件预测结果,选择合成6条候选CTL表位.研究候选CTL表位肽与T2细胞表达的HLA-A*0201分子的亲和力,进一步采用酶联免疫斑点实验(ELISPOT)和细胞内细胞因子染色(ICS)实验研究HLA-A*0201高亲和力肽在HLA-A*0201阳性HCV感染者的外周血单个核细胞(PBMC)中刺激CTL反应情况.结果 在6条候选CTL表位肽中,肽C_181(LLSCLTTPV)和NS2_172(VLQAGLIRV)与HLA-A*0201分子有高亲和力,其亲和力随肽浓度增加而升高.在10例HLA-A*0201阳性HCV-1b感染者每1×105PBMC中,肽C_181和NS2_172刺激后,特异性分泌IFN-γ细胞的斑点形成细胞数(SFC)分别为0～19和0～20.肽C_181和NS2_172特异性IFN-γ+CD8+T淋巴细胞占CD8+T淋巴细胞的比例分别为0.006%～0.065%和0.005%～0.080%.结论 肽C_181(LLSCLTTPV)和NS2_172(VLQAGLIRV)为HLA-A*0201 限制性HCV-CTL表位.     

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.     

Different hepatitis C virus nonstructural protein 3 (Ns3)-DNA-expressing vaccines induce in HLA-A2.1 transgenic mice stable cytotoxic T lymphocytes that target one major epitope.

The immunogenicity of the Hepatitis C virus (HCV) nonstructural protein 3 (NS3) was investigated using different DNA-based strategies and a preclinical mouse model transgenic for the HLA-A2.1 molecule. Plasmids expressing NS3 either as a wild-type protein, as a fusion with murine lysosome-associated-membrane protein-1 specific sequences, or under the control of the Semliki Forest virus replicase were evaluated in vitro and in vivo. All plasmids were shown to express the expected size protein. These 3 NS3-expressing vaccines induced overall comparable levels of CTLs when measured at different times postvaccination although mice injected with the NS3-LAMP expressing plasmid showed a particularly homogeneous and overall vigorous response (specific lysis ranged from 60% to 90 % for an E:T ratio of 33.3:1 with a mean CTL precursor frequency of 1:2.10(5) cells). Out of the four HLA-A2.1-restricted NS3 epitopes previously described in HCV infected patients (aa 1073-1081, aa 1406-1415; aa 1169-1177 and aa 1287-1296), the NS3-DNA generated CTLs were predominantly targeted at the aa 1073-1081 epitope. Peptide-based immunization showed that the mouse repertoire was intact for all epitopes tested except one (aa 1287-1296). In conclusion, the 3 NS3-DNA vaccines although based on different mode of action, shared a comparable efficacy at inducing CTL. Surprisingly, the breadth of such response was restricted to a single, major epitope.     

Identification of the epitopes on HCV core protein recognized by HLA-A2 restricted cytotoxic T lymphocytes

AIM: To identify hepatitis C virus(HCV) core protein epitopes recognized by HLA-A2 restricted cytotoxic T lymphocyte (CTL). METHODS: Utilizing the method of computer prediction followed by a 4h(51)Cr release assay confirmation. RESULTS: The results showed that peripheral blood mononuclear cells (PBMC) obtained from two HLA-A2 positive donors who were infected with HCV could lyse autologous target cells labeled with peptide "ALAHGVRAL (core 150-158)". The rates of specific lysis of the cells from the two donors were 37.5% and 15.8%, respectively. Blocking of the CTL response with anti-CD4 mAb caused no significant decrease of the specific lysis. But blocking of CTL response with anti-CD8 mAb could abolish the lysis. CONCLUSION: The peptide (core 150-158) is the candidate epitope recognized by HLAA2 restricted CTL.     

CD8+ cell responses to hepatitis C virus (HCV) in the liver of persons with HCV-HIV coinfection versus HCV monoinfection

OBJECTIVE: Cellular immune responses are difficult to detect in the peripheral blood of persons with chronic hepatitis C virus (HCV) infection. We sought to determine whether T cell responses were present in the liver of patients with human immunodeficiency virus (HIV) and HCV coinfection. METHODS: T cells were expanded from liver-biopsy samples from 10 patients coinfected with HIV and HCV (median CD4(+) cell count, 456 cells/mm(3)) and 8 patients infected with HCV alone. CD8(+) cell responses were detected by use of a modified enzyme-linked immunospot (ELISpot) assay with recombinant vaccinia virus, and CD4(+) cell responses were detected by use of ELISpot with recombinant HCV proteins core, nonstructural (NS) 3, and NS5. RESULTS: Intrahepatic CD8(+) cell responses to HCV were detected in 7 of 10 patients coinfected with HCV and HIV (median frequency, 638 spot-forming cells [sfc]/1 x 10(6) cells) and were similar to those observed in patients singly infected with HCV (7/8; median, 647 sfc/1 x 10(6) cells). Intrahepatic HCV-specific CD4(+) cell responses were also comparable in both groups and correlated with the intrahepatic CD8(+) cell responses (r=0.59; P=.03). CONCLUSION: HCV-specific CD8(+) cell responses are present in the liver of persons with chronic HCV infection even when they are coinfected with HIV; these correlate with intrahepatic HCV-specific CD4(+) cell responses.     

Characterization of humoral and cell-mediated immune responses directed against hepatitis C virus F protein in subjects co-infected with hepatitis C virus and HIV-1

BACKGROUND: Hepatitis C virus (HCV) F protein is encoded in an alternate reading frame overlapping the core protein region. Its precise sequence, biological function and mode of expression are currently unclear. This study was conducted to examine the prevalence and characteristics of host humoral and cell-mediated immune responses directed against F protein in patients co-infected with HCV and HIV-1. METHODS: Mutations were introduced to allow the expression of HCV-1a F protein in the absence of core. This recombinant and a truncated form lacking the first 11 amino acid residues shared with core were expressed in Escherichia coli, and their amino acid sequences were verified by mass spectrometry. Vaccinia-F protein recombinants were used to test F protein-specific cytotoxic T lymphocyte (CTL) activity. The binding of F protein-derived peptides to HLA-A*0201 was studied to identify putative CTL epitopes. RESULTS: Sera from 23 of 39 patients infected with various HCV genotypes recognized the truncated form, including 13 of 25 subjects co-infected with HIV-1, indicative of antigenic crossreactivity and consistent with the conservation of F protein coding sequences between HCV genotypes. Crossreactive F protein-specific CTL precursors were detected in nine of 11 HCV-infected subjects, including seven of nine patients co-infected with HCV and HIV-1. Finally, three novel putative HLA-A*0201-restricted CTL epitopes were identified. CONCLUSION: These results indicate that patients co-infected with HCV and HIV-1 can mount immunoglobulin and CTL responses directed against HCV F protein that are fully comparable in scope and magnitude with those observed in individuals infected with HCV alone.     

丙型肝炎病毒包膜基因对核心基因DNA疫苗免疫应答强度的影响

目的 研究丙型肝炎病毒(HCV)包膜基因E1E2对核心基因C DNA疫苗诱生的免疫应答作用。方法 将包含HCV C或CE1E2基因片段插入真核表达载体pcDNA3中,构建重组质粒pHCV-C或pHCV-CE1E2,分别免疫Balb/c小鼠,每间隔2wk加强免疫1次,同时剪尾取血。ELISA法检测免疫小鼠血清中HCV C特异性抗体的水平。以pHCV-C转染并表达HCcAg的BLAB/c小鼠骨髓瘤Sp4/0细胞为靶细胞,采用~(51)Cr释放试验检测特异性CTL的杀伤作用。结果 两个实验组20只小鼠均产生抗HCV C特异性抗体,当效/靶细胞比例为100:1时,CTL的杀伤率均明显高于对照组(p<0.01);而pHCV-CE1E2与pHCV-C组之间,无论是抗HCV C抗体的滴度还是CTL的杀伤率均无显著性差异(p>0.05)。结论 E1E2基因的加入,并没有增加HCV C基因DNA疫苗诱导的抗HCcAg特异性抗体的滴度和CTL的杀伤作用。     

Identification of a hepatitis C virus-reactive T cell receptor that does not require CD8 for target cell recognition

Hepatitis C virus (HCV) has been reported to elicit B and T cell immunity in infected patients. Despite the presence of antiviral immunity, many patients develop chronic infections leading to cirrhosis, hepatocellular carcinoma, and liver failure that can require transplantation. We have previously described the presence of HLA-A2-restricted, HCV NS3-reactive cytotoxic T lymphocytes (CTL) in the blood of HLA-A2- liver transplantation patients that received an HLA-A2+ liver allograft. These T cells are analogous to the "allospecific" T cells that have been described in hematopoietic stem cell transplantation patients. It has been speculated that allospecific T cells express high-affinity T cell receptors (TCRs). To determine if our HCV-reactive T cells expressed TCRs with relatively high affinity for antigen, we identified and cloned a TCR from an allospecific HLA-A2-restricted, HCV:NS3:1406-1415-reactive CD8+ T cell clone and expressed this HCV TCR in Jurkat cells. Tetramer binding to HCV TCR-transduced Jurkat cells required CD8 expression, whereas antigen recognition did not. In conclusion, based on the reactivity of the TCR-transduced Jurkat cells, we have identified a TCR that transfers anti-HCV reactivity to alternate effectors. These data suggest this high affinity HCV-specific TCR might have potential new immunotherapic implications.     

Selection of high-avidity CD8 T cells correlates with control of hepatitis C virus infection

Both strong antigenic avidity and acquisition of proper effector functions contribute to the efficacy of antiviral T cell responses. To correlate these parameters with the outcome of hepatitis C virus (HCV) infection, we characterized HCV-specific CD8 T cell lines isolated after immunomagnetic sorting of peripheral blood mononuclear cells from human leukocyte antigen A*02 (HLA-A*02) individuals with various HCV serological statuses, using recombinant HLA-A*0201 multimers loaded with three immunodominant HCV genotype 1-derived epitopes. CD8 T cells specific for these three epitopes were derived from most HLA-A*0201 individuals, regardless of their HCV serology or clinical outcome. Donors recovered from genotype 1 HCV infection were enriched for high-avidity T cells with enhanced interferon gamma (IFN-gamma), tumor necrosis factor alpha, and cytotoxic T lymphocyte responses, when compared with seronegative donors and seropositive patients infected with irrelevant HCV genotypes. Patients chronically infected with genotype 1 strain yielded almost exclusively low-avidity T cells, whose hyporesponsiveness was primarily attributable to low T cell receptor (TCR) avidity rather than intrinsic functional defects. CONCLUSION: This study suggests that strong IFN-gamma responses associated with efficient viral clearance primarily result from Ag-driven selection/survival of HCV-specific T cells expressing high-avidity TCR. It also suggests a link between the quality of the initial HCV-specific T cell repertoire and susceptibility to chronic infection.     

Pathogenesis of chronic hepatitis C: immunological features of hepatic injury and viral persistence.

The immune response to viral antigens is thought to be responsible for viral clearance and disease pathogenesis during hepatitis C virus (HCV) infection. In chronically infected patients, the T-cell response to the HCV is polyclonal and multispecific, although it is not as strong as the response in acutely infected patients who display a more vigorous T-cell response. Importantly, viral clearance in acutely infected patients is associated with a strong CD4(+) helper T-cell response. Thus, the dominant cause of viral persistence during HCV infection may be the development of a weak antiviral immune response to the viral antigens, with corresponding inability to eradicate infected cells. Alternatively, if clearance of HCV from the liver results from the antiviral effect of T-cell-derived cytokines, as has been demonstrated recently for the hepatitis B virus, chronic HCV infection could occur if HCV is not sensitive to such cytokines or if insufficient quantities of cytokines are produced. Liver cell damage may extend from virally infected to uninfected cells via soluble cytotoxic mediators and recruitment and activation of inflammatory cells forming the necroinflammatory response. Additional factors that could contribute to viral persistence are viral inhibition of antigen processing or presentation, modulation of the response to cytotoxic mediators, immunological tolerance to HCV antigens, mutational inactivation of cytotoxic T lymphocyte (CTL) epitopes, mutational conversion of CTL epitopes into CTL antagonists, and infection of immunologically privileged tissues. Analysis of the basis for viral persistence is hampered because the necessary cell culture system and animal model to study this question do not yet exist.     

Characterization of an immunologically conserved epitope from hepatitis C virus E2 glycoprotein recognized by HLA-A2 restricted cytotoxic T lymphocytes

BACKGROUND/AIMS: Identification of epitopes recognized by cytotoxic T lymphocytes (CTL) in hepatitis C virus (HCV) proteins is of importance because they can be used for vaccination, treatment of infection or monitoring of immune responses. Our purpose was to characterize new CTL epitopes in HCV structural proteins. METHODS: Peptides were synthesized and tested in HLA-A2 binding assays. Binder peptides were used to stimulate peripheral blood mononuclear cells from HCV+ patients and controls, and activity measured in chromium release and ELISPOT assays. RESULTS: Twenty binder peptides were found, and stimulation of HCV+ patient cells with nine peptides showing high binding ability led to the growth of CD8+ CTL recognizing peptide E2(614-622) in association with HLA-A2. Peptide E2(614-622) was recognized by 30% of HLA-A2+ patients with chronic HCV infection, but no responses were observed in control groups. Five peptides derived from region E2(614-622) from 26 different viral isolates bound to HLA-A2 molecules, and all of them but one, containing Phe at position 622, were recognized by E2(614-622) specific CTL. CONCLUSIONS: These results show that peptide E2(614-622) belongs to a highly conserved region of HCV E2, and might be a good candidate to induce anti-HCV CTL responses in HLA-A2+ subjects.     

HepG2细胞中HCV NS5A蛋白对HCV IRES启动蛋白翻译的影响

目的探讨HepG2细胞中HCV非结构蛋白5A（NS5A）对HCV IRES启动蛋白翻译的影响，以了解HCV的复制调控机制。方法将构建的表达双荧光素酶的双顺反子载体pCMV-Rluc-IRES-Fluc和含HCV NS5A基因的表达质粒pcDNA-NS5A共转染HepG2细胞，用双荧光素酶检测系统检测虫荧光素酶的表达水平，细胞免疫荧光技术检测HCV-NS5A蛋白的表达，RT-PCR检测虫荧光素酶基因mRNA水平，并与相应对照做比较，以观察HCV NS5A对HCV IRES介导虫荧光素酶翻译水平的影响。结果转染pcDNA-NS5A的HepG2细胞中虫荧光素酶活性明显高于转染pCDNA3．I-3flag的对照组，并存在剂量依赖关系；而RT-PCR虫荧光素酶基因mRNA水平在两组间差异无统计学意义。转染pcDNA-NS5A的HepG2细胞质中可见HCV NS5A蛋白的表达。结论HCV NS5A蛋白对HCV IRES介导虫荧光素酶的翻译有正调节作用，并存在剂量依赖关系．     

Reversal of nonstructural protein 3-specific CD4(+) T cell dysfunction in patients with persistent hepatitis C virus infection

Hepatitis C virus (HCV)-specific T cell responses are essential for HCV control, and chronic infection is characterized by functionally altered antigen-specific T cells. It has been proposed that the early inactivation of specific CD4(+) T cell responses may be involved in establishment of HCV persistence. We have investigated whether HCV-specific CD4(+) T cells dysfunction can be reversed in vitro. Nonstructural protein 3 (NS3) and core-specific CD4(+) T cells from eight chronically infected and eight spontaneously resolved HCV individuals were selected through transient CD154 (CD40 ligand) expression, and their functional profile (IFN-γ, IL-2, TNF-α, IL-10 and IL-4 production by enzyme-linked immunospot assay, cytometric bead array and intracellular cytokine staining, and proliferation by carboxy-fluorescein diacetate succinimidyl ester dilution assay) was determined both ex vivo and after in vitro expansion of sorted CD154-expressing cells in the absence of specific antigen in IL-7/IL-15-supplemented medium. Ex vivo bulk CD4(+) T cells from chronic patients expressed CD154 in most cases, albeit at lower frequencies than those of resolved patients (0.11%vs 0.41%; P = 0.01), when stimulated with NS3, but not core, although they had a markedly impaired capacity to produce IL-2 and IFN-γ. Antigen-free in vitro expansion of NS3-specific CD154(+) cells from chronic patients restored IFN-γ and IL-2 production and proliferation to levels similar to those of patients with spontaneously resolved infection. Hence, NS3-specific CD4(+) T cell response can be rescued in most chronic HCV patients by in vitro expansion in the absence of HCV-specific antigen. These results might provide a rationale for adoptive immunotherapy.     

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

BACKGROUND/AIMS: It has been suggested that cytotoxic T lymphocytes (CTL) have crucial roles for the hepatocellular damage in hepatitis C virus (HCV) infection. A series of CTL epitopes located in the HCV protein have been identified. However, no CTL epitopes restricted by HLA-A24, a common HLA allele in humans, has been identified. METHODS: Peripheral blood and liver infiltrating mononuclear cells from the patients with hepatitis C virus infection and healthy controls were stimulated with a series of peptides containing HLA-A24 binding motifs located in HCV protein. RESULTS: An immunodominant HLA-A24 restricted CTL epitope (A24-4; AYSQQTRGL, amino acids 1031-1039) presented by HLA-A24 molecule was identified using a series of synthetic peptides containing the HLA-A24 binding motifs. The CTL activity against this peptide was induced both in peripheral blood and liver infiltrating mononuclear cells from HLA-A24-positive chronic hepatitis C patients, not from HLA-A24-negative patients and HLA-A24-positive healthy controls. CTL activity was blocked by anti-HLA-A24 and anti-CD8 antibodies, not by anti-CD4 antibody. Furthermore, the A24-4-specific CTL recognized the HCV gene transfected target cells. CONCLUSIONS: Because this peptide is presented by a common HLA class I molecule, it might be useful for protection against hepatocellular damage and vaccine development in large population of the HCV-infected patients.     

丙型肝炎病毒HLA-A2限制性复合多表位基因重组腺病毒的包装、筛选及鉴定

目的构建丙型肝炎病毒（HCV）HLA-A2限制性复合多表位基因的重组转移质粒pAdtrack-CMV-Ub-Mep,转染HEK293细胞,包装重组腺病毒rAd-Ub-Mep。方法复合表位Ub-Mep基因克隆到pAdTrack-CMV穿梭质粒,得到重组的穿梭质粒pAdtrack-CMV-Ub-Mep,将穿梭质粒pAdtrack-CMV-Ub-Mep和腺病毒骨架质粒pAdEasy1共转染HEK293细胞,产生重组腺病毒rAd-Ub-Mep,通过检测绿色荧光蛋白（GFP）的表达和PCR扩增目的基因的方法鉴定重组腺病毒,并测定重组腺病毒滴度。结果经酶切鉴定、PCR鉴定和荧光分析,均证实得到重组的腺病毒。测定病毒滴度为1.2×1011cfu/L。结论成功包装出重组腺病毒rAd-Ub-Mep,构建了HCV HLA-A2限制性多表位基因的重组腺病毒疫苗,为进一步研究HLA-A2限制性复合多表位基因诱导的细胞免疫应答奠定了基础。