Use of a novel hepatitis C virus (HCV) major-epitope chimeric polypeptide for diagnosis of HCV infection

The genome of hepatitis C virus (HCV) consists of seven functional regions: the core, E1, E2/NS1, NS2, NS3, NS4, and NS5 regions. The U. S. Food and Drug Administration-licensed 2.0G immunoassay for the detection of anti-HCV uses proteins from the core, NS3, and NS4 regions (McHutchinson et al., Hepatology 15:19-25, 1992). The 3.0G enzyme-linked immunosorbent assay includes the protein from the NS5 region (Uyttendaele et al., Vox Sang. 66:122-129, 1994). The necessity of detecting antibodies to viral envelope proteins (E1 and E2) and to different genotype samples has been demonstrated previously (Chien et al., Lancet 342:933, 1993; Lok et al., Hepatology 18:497-502, 1993). In this study we have attempted to improve the sensitivity of the anti-HCV assay by developing a single multiple-epitope fusion antigen (MEFA; MEFA-6) which incorporates all of the major immunodominant epitopes from the seven functional regions of the HCV genome. A nucleic acid sequence consisting of proteins from the viral core, E1, E2, NS3, NS4, and NS5 regions and different subtype-specific regions of the NS4 region was constructed, cloned, and expressed in yeast. The epitopes present on this antigen can be detected by epitope-specific monoclonal and polyclonal antibodies. In a competition assay, the MEFA-6 protein competed with 83 to 96% of genotype-specific antibodies from HCV genotype-specific peptides. This recombinant antigen was subsequently used to design an anti-HCV chemiluminescent immunoassay. We designed our assay using a monoclonal anti-human immunoglobulin G antibody bound to the solid phase. Because MEFA-6 is fused with human superoxide dismutase (h-SOD), we used an anti-human superoxide dismutase, dimethyl acridinium ester-labeled monoclonal antibody for detection. Our results indicate that MEFA-6 exposes all of the major immunogenic epitopes. Its excellent sensitivity and specificity for the detection of clinical seroconversion are demonstrated by this assay.     

A correlation between the heterogeneity of hypervariable region 1 of E2 glycoprotein of Hepatitis C virus (HCV) and HCV antibody profile: a case study

A correlation between the heterogeneity of hypervariable region 1 (HVR1) of E2 glycoprotein (gp) and Hepatitis C virus (HCV) antibody profile was investigated. Of 6 patients studied two were in acute phase, two in chronic phase and two showed signs of long-time HCV infection, i.e. liver cirrhosis. All the patients exhibited a vigorous antibody response to viral proteins C, NS3, NS4 and NS5. An antibody response to HVR1 of E2 was found in one patient in acute phase and in one or two patients in chronic phase. Such a response was not found in the two patients with liver cirrhosis. Single-stranded conformation polymorphism (SSCP) and sequence analyses of HVR1 of E2 showed the lowest HVR1 heterogeneity in patients in acute phase and the highest one in those in chronic phase, while the long-time carriers of the virus showed an intermediate heterogeneity. This may reflect a specific interplay between the virus and immune system. The HVR1 heterogeneity may rise in the course of infection as a means of evading the immune pressure. Then, when an organism is unable to clear the virus, because the responses to HVR1 epitopes are weakened or exhausted, a population of less heterogeneous HVR1 variants may be established.     

丙型肝炎病毒全长cDNA模板的构建及鉴定

目的 构建具有功能的丙型肝炎病毒(HCV)全长cDNA克隆。方法 应用长模板RTPCR法扩增1份上海地区HCV感染者血清的RNA(基因型为1b)，分段扩增、融合拼接成9．2kb的基因片段，克隆人含有HCV基因两端非编码区序列的载体作为模板。为检测此过程是否发生对特定变异株的选择，分析4个独立克隆的HVRl序列。对原核细胞中表达的HCV核心蛋白、NS3蛋白酶及解旋酶，以蛋白印迹实验确证其免疫反应性。并构建NS3／4A-SEAP表达系统检验NS3的蛋白酶活性。结果 获得丙型肝炎病毒全长cDNA模板。不同克隆间HVR1序列存在较大差异，提示长模板RT-PCR所制备HCVcDNA具有HCV基因准种(quasispecies)的特性。该模板编码基因在原核细胞内得到高效表达，并具有良好的免疫反应性。在NS3／4A-SEAP表达系统内，NS3可切割、释放其下游的SEAP，具有蛋白酶活性。结论 本工作为构建全长功能性HCV cDNA模板及感染性克隆奠定了基础。     

Presentation of the hydrophilic domains of hepatitis C Viral E2 envelope glycoprotein on hepatitis B surface antigen particles

Subviral particles of hepatitis B virus have been used to present foreign epitopes. We attempted to present the hydrophilic domains of E2 envelope protein of hepatitis C virus (HCV) as a fusion protein with hepatitis B virus surface antigen (HBsAg). The five hydrophilic domains of HCV E2 antigen were inserted into HBsAg such that the inserted hydrophilic domains were presented on the outer surface of HBV subviral particles. In addition, a fusion encoding the hypervariable region (HVR) of E2 antigen was also made. Cell lysate and culture medium were analyzed for the synthesis and secretion of the fusion proteins by immunoprecipitation with polyclonal anti-HBsAg antibody using recombinant vaccinia virus system. The results showed that the fusion proteins containing these six E2 domains were made in the cell, but only two out of six fusion proteins were secreted into culture medium. Further, cesium chloride density gradient analysis and electron microscopy revealed that these fusions were secreted into culture media as particles. It will be of interest to test immunogenicity of the HBsAg fusion particles containing the HCV E2 domains in animal model. © 1996 Wiley-Liss, Inc.     

Humoral immunity to immunodominant epitopes of Hepatitis C virus in individuals infected with genotypes 1a or 1b

Cellular immunity against multiple Hepatitis C virus (HCV) proteins is observed in patients acutely infected with HCV most of whom later resolve infection. We wished to assess humoral immunity in patients infected with HCV 1a or 1b genotypes in relation to viral load using plasma samples from HCV-infected individuals and a panel of peptides representing immunodominant epitopes of HCV structural and nonstructural proteins. Plasma from HCV 1a- and 1b-infected patients, respectively, were divided into two groups: patients with low viral load (<==100,000 RNA copies/ml) and patients with high viral load (>/=10,000,000 RNA copies/ml). The antigens were peptides representing epitopes from immunodominant regions of HCV core, E2, NS3, and NS4 proteins, as well as the hypervariable (HVR) epitopes in E2 from genotypes 1a and 1b. Individuals infected with HCV 1a evoked a stronger immune response to many immunodominant epitopes of HCV relative to individuals infected with HCV 1b. Moreover, among individuals infected with HCV 1a, those with low viral loads mounted significantly greater responses against these epitopes than did individuals with high viral loads. Our observations demonstrate that quantitatively different antibody responses are elicited against HCV depending on the genotype of infecting virus, and suggest that humoral immunity directed against multiple immunodominant epitopes in HCV 1a-infected individuals may help lower viral load in vivo.     

Characterization of a panel of monoclonal antibodies to hepatitis C NS3 recombinant protein

Recombinant protein rNS3 imitating helicase region (1356-1459 amino acid residues) of hepatitis C virus (HCV) was expressed in E. coli cells and used for BALB/c mice immunization. Seven hybrydoma clones producing monoclonal antibodies (MAbs) to rHS3 were obtained. All MAbs reacted in ELISA with NS3 protein from Murex anti-HCV Version III and in immunoblotting from RIBA 3. These MAbs detect 5 individual epitopes, 4 of which were conformational and 1 discontinuous. All MAbs could compete for rNS3 binding with serum antibodies from patients with chronic hepatitis C, which suggests that these MAbs can recognize the natural HCV NS3 protein.     

丙型肝炎病毒包膜糖蛋白高变区1多抗原肽设计及？…

目的 应用多抗原肽（ＭＡＰ）研究丙型肝炎病毒包膜糖蛋白高变区１（ＨＶＲ１）的抗原性。方法 根据已经获得的ＨＣＶ－ＢＪ株Ｅ２／ＮＳ１区氨基酸序列,参照国内外得所报道的ＨＶ ＨＶＲ１序列及抗原性参数,设计并合成含ＨＣＶ ＨＶＲ１３９０－４１１ａａ序列２２个氨基酸的线性表位多肽（以ＬＰ表示）及ＭＡＰ（对称８分枝）,分别以ＬＰ和ＭＡＰ免疫Ｂａｌｂ／Ｃ小鼠及家兔,比较其免疫原性。结果 ＭＡＰ免疫原性明显强于     

Structural and functional organization of hepatitis C virus genome

The review gives recent data on the structure of hepatitis C virus genome. Linear RNA comprises one translated and two nontranslated regions: 5'UTR and 3'UTR. Translation of viral RNA gives rise to a single polyprotein precursor that contains structural and nonstructural regions. The structural region comprises one nucleocapsid core-protein and two envelope proteins known as E1 and E2. E2 protein includes two hypervariable regions: HVR1 and HVR2. The nonstructural region consists of 7 proteins: p7 (NS1), NS (metalloproteinase), NS (serine protease/ helicase), NS4A (co-factor protease, co-factor RNA-dependent RNA polymerase), and NS4B, NS5A, NS5B (RNA-dependent RNA polymerase). NS5A includes ISDR (interferon-sensitivity-determining region).     

Multiepitope Fusion Antigen Induces Broadly Protective Antibodies That Prevent Adherence of Escherichia coli Strains Expressing Colonization Factor Antigen I (CFA/I), CFA/II,and CFA/IV

Diarrhea is the second leading cause of death in children younger than 5 years and continues to be a major threat to global health. Enterotoxigenic Escherichia coli (ETEC) strains are the most common bacteria causing diarrhea in developing countries. ETEC strains are able to attach to host small intestinal epithelial cells by using bacterial colonization factor antigen (CFA) adhesins. This attachment helps to initiate the diarrheal disease. Vaccines that induce antiadhesin immunity to block adherence of ETEC strains that express immunologically heterogeneous CFA adhesins are expected to protect against ETEC diarrhea. In this study, we created a CFA multiepitope fusion antigen (MEFA) carrying representative epitopes of CFA/I, CFA/II (CS1, CS2, and CS3), and CFA/IV (CS4, CS5, and CS6), examined its immunogenicity in mice, and assessed the potential of this MEFA as an antiadhesin vaccine against ETEC. Mice intraperitoneally immunized with this CFA MEFA exhibited no adverse effects and developed immune responses to CFA/I, CFA/II, and CFA/IV adhesins. Moreover, after incubation with serum of the immunized mice, ETEC or E. coli strains expressing CFA/I, CFA/II, or CFA/IV adhesins were significantly inhibited in adherence to Caco-2 cells. Our results indicated this CFA MEFA elicited antibodies that not only cross-reacted to CFA/I, CFA/II and CFA/IV adhesins but also broadly inhibited adherence of E. coli strains expressing these seven adhesins and suggested that this CFA MEFA could be a candidate to induce broad-spectrum antiadhesin protection against ETEC diarrhea. Additionally, this antigen construction approach (creating an MEFA) may be generally used in vaccine development against heterogenic pathogens.     

HCV NS5A-B片段的表达及在酶活性研究中的应用

目的：利用原核表达载体pBVIL1，表达丙型肝炎病毒非结构蛋白（NS3）丝氨酸蛋白酶催化底物NS5A—B小分子，为进一步研究蛋白酶活性提供方法学。方法：将PCR合成的NS5A—B（2412—2427aa）基因直接插入高效原核表达载体pBVIL1，融合表达NS5A—B片段．包涵体形式的表达产物用8mol／L脲溶解后，采用离子交换和凝胶过滤两步纯化。利用SDS—PAGE、Western blot和ELISA方法，于37℃酶催化条件下，分析NS5A—B底物的降解活性。结果：（1）构建了pBVIL1／NS5A—B重组质粒，鉴定证明NS5A—B基因片段正确地插入表达载体上：融合蛋白在转化质粒的HB101菌中得到高效表达。分离纯化重组蛋白后浓度可达0．73g／L。（2）在NS3蛋白酶作用不同时间后，用SDS—PAGE和Western blot证实，底物带可被明显降解，ELISA分析也证明，NS5A—B具有酶底物活性。结论：含有酶切位点的NS5A—B融合蛋白可被NS3丝氦酸蛋白酶有效地降解，可用作为NS3蛋白酶的底物，可替代全长NS5A—B和化学合成肽用于酶活性和酶阻断剂的研究     

Artificial NS4 mosaic antigen of hepatitis C virus.

An artificial antigen composed of 17 small antigenic regions derived from the NS4-protein of hepatitis C virus (HCV) genotypes 1 through 5 was designed and constructed. Eleven antigenic regions were derived from the 5-1-1 region, and 6 others were derived from the C-terminus of the NS4-protein of different genotypes. The gene encoding for this artificial antigen was assembled from synthetic oligonucleotides by a new approach designated as restriction enzyme-assisted ligation (REAL). The full-length synthetic gene was expressed in Escherichia coli as a fusion protein with glutathione S-transferase. By the use of site-specific antibodies raised against synthetic peptides, it was shown that all regions for which sequence-specific antibodies were obtained were accessible to antibody binding. The diagnostic relevance of the NS4 artificial antigen was demonstrated by testing this antigen with 4 HCV seroconversion panels and a panel of previously tested and stored serum specimens. The artificial antigen was found to specifically detect anti-NS4 antibodies in a number of specimens that were previously found to be anti-NS4 negative. Furthermore, this antigen detected anti-NS4 activity earlier in 2 of 4 seroconversion panels than did the antigen used in a commercially available supplemental assay. Equally important is the observation that the artificial NS4 antigen demonstrated equivalent anti-NS4 immunoreactivity with serum specimens obtained from patients infected with different HCV genotypes, whereas the NS4 recombinant protein derived from genotype 1, used in the commercial supplemental test, was less immunoreactive with serum specimens containing HCV genotypes 2, 3, and 4. Collectively, these data support the significant diagnostic potential of the NS4 mosaic antigen. The strategy employed in this study may be applied to the design and construction of other artificial antigens with improved diagnostically pertinent properties. J. Med. Virol. 59:437-450 1999.     

PCR-Based In Vitro Synthesis of Hepatitis C Virus NS3 Protease for Rapid Phenotypic Resistance Testing of Protease Inhibitors

Protease inhibitors (PIs) targeting the hepatitis C virus (HCV) NS3 protease, such as telaprevir, have significantly improved the sustained virologic response (SVR) rates of HCV genotype 1 antiviral therapy. Given the expanding antiviral therapy regimen, fast HCV PI resistance assays are urgently needed. In this view, we have developed a novel phenotypic resistance test for HCV PIs based on in vitro synthesis of patient-derived HCV NS3 protease and subsequent enzymatic testing in a fluorescent readout. The enzymatically active HCV NS3 proteases were synthesized from PCR-derived templates by an Escherichia coli S30 extract system. Tests of the protease genes with known mutations for telaprevir resistance showed that the phenotypic resistance test was fast, with a total turnaround time of <10 h, and was fully in agreement with the previous resistance results. The initial tests with 38 treatment-naive serum samples showed that the method was significantly less laborious and faster than currently available phenotypic resistance assays of HCV NS3 PIs.     

Analysis of a non-structural gene reveals evidence of possible hepatitis C virus (HCV) compartmentalization

Viral diversity is a hallmark of hepatitis C virus (HCV) infection; however, only limited data are available regarding HCV variability in extrahepatic sites, and none have systematically compared diversity in non‐structural and structural genomic regions. Therefore, HCV diversity in the NS5B and envelope 1 (E1) hypervariable region 1 (HVR1) genes was evaluated in matched sera and peripheral blood mononuclear cells (PBMCs) obtained from 13 HCV‐infected women. Multiple clonal sequences were compared to evaluate quasispecies diversity and viral compartmentalization in PBMCs. Genetic distances were higher for E1/HVR1 compared to NS5B in both the sera and PBMCs (P = 0.0511 and 0.0284). Genetic distances were higher in serum NS5B compared to PBMC NS5B (P = 0.0003); however, they were not different when comparing E1/HVR1 in sera to PBMCs. By phylogenetic analysis of NS5B, evidence of possible PBMC compartmentalization was observed for one woman, while statistical methods were consistent with PBMC compartmentalization for six women. Evidence of compartmentalization within a non‐structural genomic region may suggest that viral adaptation to a unique extracellular microenvironment(s) may be required for efficient replication and could contribute to HCV persistence. J. Med. Virol. 84:242–252, 2012. © 2011 Wiley Periodicals, Inc.     

鼠抗丙型肝炎病毒（HCV）NS3区单克隆抗体的研制及特性分析

用淋巴细胞杂交瘤技术，制备出５株抗ＨＣＶ－ＮＳ３区单克隆抗体（ＭｃＡｂ）分别命名为Ｃ７－１，３，６，８，９。单抗特性测定结果显示５株单抗均为ＨＣＶ－ＮＳ３区特异性，与ＨＣＶ其它区域的抗原及宿主菌成份均无交叉反应，此５株单抗识别ＮＳ３区上两个不完全相关的抗原位点，其中Ｃ７－１，３，６株识别同一抗原决定簇，Ｓ７－９的识别位点与此３株有一定的相关，Ｃ７－８则识别与此４株不完全相关的位点。ＨＣＶ－ＮＳ３抗     

Identification of B cell epitopes of hepatitis C virus RNA dependent RNA polymerase

The aim of this study was to identify the B cell epitopes of hepatitis C virus (HCV) NS5B RNA dependent RNA polymerase (RdRp). The truncated HCV NS5B protein NS5B-dc21 was expressed in Escherichia coli and its antigenicity was confirmed by Enzyme-Linked Immunosorbent Assay (ELISA) using 130 HCV-positive human sera and 15 negative sera. Antibodies specific to NS5B-dc21 protein were purified by affinity chromatography using sepharose-4B coupled with the recombinant protein. A 12-mer phage displayed random peptide library was screened four rounds with the purified antibodies. Three epitopes were identified from the phage library, which correspond to amino acids 2444-2452, 2521-2528, and 2915-2925 of HCV RdRp. These epitopes were then expressed in E. coli as fusion proteins with phage M13 pIII protein. ELISA demonstrated that two of these epitopes (P4 and P34, corresponding to amino acids 2443-2452 and amino acids 2512-2528, respectively) have good reactivity and sensitivity. Mutagenesis study of P4 peptide showed that this epitope, which is derived from a phage displayed library, exhibited higher affinity with HCV serum than the corresponding original HCV sequences.     

B-cell epitopes in hypervariable region 1 of hepatitis C virus obtained from patients with chronic persistent hepatitis

The hypervariable domain (HVR1) within the N-terminus of the E2 protein of hepatitis C virus (HCV) is known to be variable antigenically during the course of persistent infection. The aim of the study was to detect B-cell epitopes in HVR1 responsible for neutralizing HCV. The B-cell epitopes were analyzed using two series of synthetic peptides: 25 heptapeptides from the most common amino acids within 73 HVR1 sequences, and 216 heptapeptides, the sequences of which cover more than 65% of the 73 HVR1 sequences. Sera from three patients with chronic hepatitis C were tested for reactivity to the synthetic peptide sequences by enzyme-linked immunosorbent assay (ELISA). The post-interferon (IFN) serum of one patient who had a long-term response to treatment reacted specifically with 13 heptapeptides of 216 variable sequences of HVR1. Some of the amino acid sequences (amino acids 398, 399, 400, 404) of the heptapeptides were also found in those deduced from the nucleotide sequences of HCV genomes in the pre-IFN serum. The sera of the other two patients who did not respond to treatment did not react with the 13 heptapeptides. It is concluded that the B-cell epitopes in HVR1 may be relevant for eliminating viremia in the case of the patient who had a good response to treatment. These results suggest that the analysis of the B-cell epitopes recognized in HVR1 may be important in understanding the mechanism of persistent infection and progression of hepatitis. © 1996 Wiley-Liss, Inc.     

A novel high throughput screening assay for HCV NS3 serine protease inhibitors

Hepatitis C virus (HCV) infection is a major worldwide health problem, causing chronic hepatitis, liver cirrhosis and primary liver cancer (Hepatocellular carcinoma). HCV encodes a precursor polyprotein that is enzymatically cleaved to release the individual viral proteins. The viral non-structural proteins are cleaved by the HCV NS3 serine protease. NS3 is regarded currently as a potential target for anti-viral drugs thus specific inhibitors of its enzymatic activity should be of importance. A prime requisite for detailed biochemical studies of the protease and its potential inhibitors is the availability of a rapid reliable in vitro assay of enzyme activity. A novel assay for measurement of HCV NS3 serine protease activity was developed for screening of HCV NS3 serine protease potential inhibitors. Recombinant NS3 serine protease was isolated and purified, and a fluorometric assay for NS3 proteolytic activity was developed. As an NS3 substrate we engineered a recombinant fusion protein where a green fluorescent protein is linked to a cellulose-binding domain via the NS5A/B site that is cleavable by NS3. Cleavage of this substrate by NS3 results in emission of fluorescent light that is easily detected and quantitated by fluorometry. Using our system we identified NS3 serine protease inhibitors from extracts obtained from natural Indian Siddha medicinal plants. Our unique fluorometric assay is very sensitive and has a high throughput capacity making it suitable for screening of potential NS3 serine protease inhibitors.     

Serological markers of posttransfusion hepatitis C viral infection.

Serological markers for hepatitis C virus (HCV) infection were measured in serial samples from 14 posttransfusion chronic non-A, non-B hepatitis patients by a semiquantitative dot blot immunoassay. The assay detected antibodies to HCV by use of recombinant proteins that represent putative HCV capsid (core), nonstructural protein 3 (NS3) (33c), and NS4 (c100) epitopes. Seroconversion to anti-HCV antibodies (anti-HCV) was detected in all patients. The average time to active antibody production detected by any of the recombinant proteins was 13.8 (range, 3.6 to 22.0) weeks posttransfusion or 4.6 (range, -4.5 to 13.4) weeks after the first biochemical marker of illness. Anti-HCV were detected earliest by the core antigen in most cases; however, the patterns of anti-HCV responses varied significantly among individuals. Overall, the addition of the core and NS3 antigens to the assay enabled the detection of the antibody response 4 to 5 weeks earlier than did the addition of the c100 antigen, the sole antigen used in current screening tests in the United States. Passively transferred antibodies were detected by at least one antigen in early posttransfusion samples from 12 patients and decayed below detectable levels for all antigens in only 2 patients. Antibodies to all three gene products were evident in the last sample from all five patients monitored for greater than 3 years from transfusion indicating the persistence of antibodies in patients with chronic illness. Our data show that the period following the onset of hepatitis during which anti-HCV are not detected by current screening assays can be greatly shortened by the detection of anti-HCV responses by a combination of core, NS3, and c100 antigens.     

Lack of optimal T-cell reactivity against the hepatitis C virus is associated with the development of fibrosis/cirrhosis during chronic hepatitis

Chronic hepatitis C virus (HCV) infection develops in 85% of exposed individuals and 20% develop cirrhosis. However, the pathogenesis of this process is not well-understood. The objective of this study was to determine whether HCV-reactive T cells play a role in the process of development of cirrhosis during chronic HCV infection. We analyzed 21 human leukocyte antigen (HLA)-A2 patients with chronic HCV infection (9 with histology of inflammation and 12 with histology of fibrosis/cirrhosis). The frequency of CD8(+) T cells reactive to 12 HCV-derived epitopes was determined by an interferon-gamma enzyme-linked immunospot (ELISPOT) assay. The frequency of CD4(+) Th1 and Th2 cells reactive to the HCV core antigen was determined by interferon-gamma and interleukin-5 ELISPOT assays, respectively. Patients with histology of inflammation showed a significantly higher CD8(+) T-cell response to five HCV-derived epitopes (YLLPRRGPRL [core], CINGVCWTV [NS3], LLCPAGHAV [NS3], ILAGYGAGV [NS4B], and GLQDCTMLV [NS5B]) as compared with patients with histology of fibrosis/cirrhosis. Also, patients with histology of inflammation showed a significantly higher CD4(+) Th1 response to the HCV core antigen as compared to patients with histology of fibrosis/cirrhosis. These results indicate that a lack of an optimal T-cell response to HCV is associated with the development of cirrhosis during chronic HCV infection.