Ectopic expression of methionine aminopeptidase-2 causes cell transformation and stimulates proliferation.

Methionine aminopeptidase-2 (MetAP2) processes N-terminal methionine from nascent cellular proteins. Inhibition of MetAP2 has been shown to block angiogenesis and suppress tumor growth in preclinical tumor models. However, the biological role of MetAP2 in cancer is not well understood. We examined the effect of three distinct chemical classes of MetAP2 inhibitors on the growth of a panel of human cancer cells in vitro. All MetAP2 inhibitors caused inhibition of tumor cell growth in both anchorage-dependent and, particularly, in anchorage-independent manner. These data prompted us to examine the possible roles of MetAP2 in cancers. Ectopic expression of MetAP2 in NIH-3T3 cells caused transformation, evidenced by the formation of foci in monolayer culture and growth of large colonies in soft agar. Overexpression of MetAP2 in an immortalized bronchial epithelial cell line NL20 accelerated growth. These phenotypes induced by the overexpression of MetAP2 were reversed by the treatment with MetAP2 inhibitors, indicating that the catalytic function of MetAP2 was essential. Accordingly, overexpression of a catalytically inactive MetAP2 resulted in growth retardation of HT1080 tumor cells, suggesting a dominant-negative role of the inactive MetAP2 mutant. Finally, we analysed the expression of MetAP2 in patient cancer samples by immunohistochemistry. Moderate-to-high staining was identified in the majority of breast, colon, lung, ovarian and prostate carcinomas examined. These data suggest that MetAP2 plays an important role in tumor cell growth and may contribute to tumorigenesis.

Hepatitis C virus core and E2 protein expression in transgenic mice.

Transgenic mice have been produced that express the hepatitis C virus (HCV) core protein in the liver under the transcriptional control of the mouse major urinary protein promoter. These animals express the full length core protein in cytoplasm of their hepatocytes at levels comparable to those detected in naturally infected patients, without histological or biochemical evidence of liver disease or hepatocellular carcinoma. This contrasts with recent reports that HCV core protein can transform NIH 3T3 cells and cooperates with H-ras to transform primary rat fibroblasts in vitro. Coexpression of HCV core protein in double transgenic mice that replicate the hepatitis B virus (HBV) does not inhibit hepatocellular HBV gene expression or replication, contrary to reports that it inhibits HBV replication in HuH-7 cells after transient transfection in vitro. We have also produced transgenic mice in which a C-terminally truncated (aa384-715) glycosylated HCV E2 protein is expressed in the liver under the transcriptional control of the mouse albumin promoter. Despite the high level expression of HCV E2 protein, no evidence of liver disease was detected in these animals. These results suggest that the HCV core and E2 proteins are not cytopathic for the hepatocyte in vivo, and they represent an initial step in the development of a small animal model of HCV immunopathology.

Significance of anti-E2 in the diagnosis of HCV infection in patients on maintenance hemodialysis: anti-E2 is frequently detected among anti-HCV antibody-negative patients.

A routine screening test used in the diagnosis of hepatitis C virus (HCV) infection is the anti-HCV antibody (anti-HCV) test containing core, NS3, NS4, and NS5 antigens of HCV. When HCV infection occurs in immunocompromised hosts, antibody formation against core, NS3, or NS4 antigens may be weak in the presence of HCV viremia and cannot be detected by routine anti-HCV tests. This study proposed that in immunocompromised hosts such as patients with chronic renal failure (whose capacity to form antibodies is diminished), antibody formation against the E2 region would be preserved, because the E2/NS1 region of HCV is strongly immunogenic. The aim of this study is to evaluate the significance of anti-E2 in the diagnosis of HCV infection among patients on maintenance hemodialysis who are anti-HCV-negative, using a conventional third-generation enzyme immunoassay (EIA) kit. The E2/NS1 gene of HCV encoding the amino acid sequence 388-664 was molecularly cloned into a vector containing an SV 40 promotor and was expressed in Chinese Hamster ovary cells. Using this E2 protein, the anti-E2 test was performed by EIA on 100 patients on maintenance hemodialysis, and on 50 patients with chronic hepatitis C who were anti-HCV-positive, to evaluate the antigenecity of the E2 protein. Of the 100 hemodialysis patients, 15 (15.0%) tested anti-HCV-positive using a third generation anti-HCV ELISA kit. Of the 85 patients who tested negative for anti-HCV, nine (10.6%) were anti-E2-positive and six (66.7%) of these anti-E2 positive patients showed HCV RNA viremia by HCV reverse transcription-polymerase chain reaction. Fourty-two (84.0%) of 50 patients with chronic hepatitis C were anti-E2-positive. As a control group, we tested for anti-E2 among 30 blood donors who were anti-HCV-negative, and also among 85 patients with hepatocellular carcinoma who were anti-HCV-negative, but in both groups, none (0%) was anti-E2-positive. In conclusion, these data suggest that the E2 protein of HCV should be included in a diagnostic anti-HCV kit for the detection of HCV infection in immunocompromised patients.

Persistent hepatitis C virus infection after liver transplantation: clinical and virological features.

We report a prospective clinical and virological study of 18 patients undergoing orthotopic liver transplantation, selected because of hepatitis C virus (HCV) RNA positivity before transplantation. Nine of the 18 patients (50%) developed chronic active hepatitis (CAH) in liver allografts during the first year posttransplantation; hepatitis was first observed between 6 and 25 weeks posttransplantation. HCV viremia was measured for all patients before transplantation and on posttransplantation days 3, 7, and 14, and months 1, 6, 12, and 24 to 41, by quantitative competitive RNA polymerase chain reaction (QC-PCR). HCV RNA levels on posttransplantation days 3, 7, and 14 were significantly higher among patients who subsequently developed CAH versus those who did not (P < .02 by t-test and Mann-Whitney test on all three dates). However, HCV RNA levels in sera obtained at 1, 6, and 12 months posttransplantation did not correlate with CAH at 1 year or with HCV genotype determined in posttransplantation sera. At least two serial liver biopsy specimens from each patient were stained for HCV nonstructural 4 (NS4) antigen by immunohistochemistry. The intensity of cytoplasmic staining of NS4 antigen was significantly higher for specimens with CAH versus those without CAH (P = .028 by chi 2). Three patients developed bridging fibrosis in liver allografts during the first year after transplantation; all three patients had intense (3+) immunostaining for NS4 antigen, and the infecting genotypes were 1a, 1b, and 1a plus 1b, respectively. In summary, the 18 patients all developed high-titer viremia by 1 month after liver transplantation, whereas CAH developed in 50% of allografts during the first year after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatitis C--associated glomerular disease in liver transplant recipients.

Hepatitis C virus (HCV) infection may be associated with extrahepatic illness including renal disease. We investigated the clinical and virological characteristics of three patients who developed a mesangial proliferative and sclerosing glomerulopathy alone or in association with membranoproliferative glomerulonephritis after liver transplantation for end-stage liver disease secondary to HCV infection. Using polymerase chain reaction technology and the IgM RIBA assay, viral load, genotype and IgM antibody response to HCV in the setting of glomerulonephritis was evaluated. Within 1 year of transplantation, the patients showed decreased renal function, proteinuria and recurrent hepatitis C liver disease. Likewise, HCV viral load increased following transplantation, whereas the viral genotypes remained unchanged. Although the first patient presented with classic type II cryoglobulinemia in association with glomerulonephritis, the second patient developed an IgM directed specifically against the hepatitis C core antigen. The third patient developed a low-titered IgM directed against the hepatitis C core antigen with rheumatoid factor activity but without cryoglobulinemia. All of the patients show IgM in glomerular capillary walls by biopsy. One patient has shown a clinical response to interferon (IFN) alfa-2b therapy without evidence of hepatic allograft rejection. The second and third patients have not responded to IFN or developed hepatic rejection. This study suggests that HCV-associated glomerulonephritis may complicate liver transplantation in conjunction with the production of increased amounts of IgM of variable specificity. The posttransplant setting may provide a unique situation in which to investigate the specific requirements for the onset of renal disease.

Antibody to hepatitis C virus second envelope (HCV-E2) glycoprotein: a new marker of HCV infection closely associated with viremia.

The second envelope protein (E2) of the hepatitis C virus (HCV) was cloned and expressed in Chinese hamster ovary (CHO) cells. This E2 glycoprotein was purified using ion exchange and lectin chromatography and used to construct an enzyme immunoassay for HCV E2 antibodies. The assay was shown to have good specificity, and detection of E2 antibodies was positively correlated (97.3%) to the presence of HCV RNA in serum and plasma. A high concordance between HCV 2.0 and E2 EIA reactivities was also observed. E2 antibody was the first serological marker to appear in 3/5 HCV seroconversion panels. This work demonstrated that 42.4% of core and 15.4% of NS3 indeterminate specimens also contained antibodies to E2, suggesting that HCV infection had occurred in these individuals. The E2 antibody assay was used to evaluate HCV 2.0 EIA-positive, HCV 3.0 EIA-negative plasma donors with indeterminate reactivity on RIBA HCV 2.0 or MATRIX HCV 1.0. Several HCV 3.0-negative specimens were shown to contain E2 antibodies in addition to an original indeterminate serological marker, primarily core. It is concluded that anti-E2 is a useful marker for determining HCV infection, and that the presence of antibodies to two nonoverlapping viral gene products suggests true HCV exposure. New HCV 3.0 blood screening tests should detect HCV 2.0-positive donors who present with an indeterminate pattern by RIBA or MATRIX and who also carry E2 antibodies.

Expression of HCV envelope proteins and the serological utility of the anti-E2 immune response.

The 5' end of the hepatitis C virus (HCV) genome encodes structural proteins of the virion. The first gene encodes a highly basic core protein. Immediately downstream of the core gene are regions which encode the envelope proteins (E1 and E2) of the virus. Artificial expression and secretion of immunologically active envelope proteins have proven to be a substantial challenge due to the high degree of glycosylation and the existence of certain hydrophobic domains contained within these sequences. Bacterial cell expression of recombinant HCV envelope proteins results in products that are not glycosylated and are poorly immunogenic. Emphasis has shifted to the use of mammalian cell lines (human embryonic kidney [HEK] and Chinese hamster ovary [CHO] cells) for the expression of glycosylated, immunologically active envelope proteins. Using HEK cells, E1 is expressed intracellularly but is not secreted from the cells. When E1 is cloned in fusion with a C-terminal truncated E2 protein, both proteins are detected intracellularly; however, only E2 is secreted. When the E1/E2 processing site is interrupted by constructing deletion mutants, the unprocessed E1/E2 fusion protein can be secreted from the cells. Quantifiable expression and secretion of a truncated E2 protein is now possible using CHO cells and SV40-based vectors. The HCV E2 glycoprotein expressed from CHO cells is highly antigenic; a strong humoral response to this antigen develops in persons infected with HCV. Antibodies to E2 are found in 95% of patients with detectable HCV RNA in their sera. The presence of antibodies to E2 is not indicative of viral clearance and therefore the role these antibodies play in protective immunity, if any, is unclear.

E2 and NS5: new antigens for detection of hepatitis C virus antibodies.

The value of two new hepatitis C virus (HCV) antigens for detection of HCV antibodies was studied. These two recombinant antigens were derived from the nonstructural-5 (NS5) and envelope-2 (E2) region of the HCV genome. In a panel of 33 HCV-RNA positive samples with indeterminate Riba-2 confirmatory test results, 29 samples (88%) showed additional antibody reactivity against E2 and 12 samples (36%) showed additional reactivity against NS5. Among 39 HCV-RNA negative, Riba-2 indeterminate donor samples, no additional E2 or NS5 reactivity was found in 34 samples (87%); while 5 samples (13%) showed additional reactivity against NS5 and/or E2. E2 reactivity thus resolved the majority of hitherto indeterminate samples. In serial samples from nine posttransfusion hepatitis C patients, NS5 and E2 antibodies did not appear earlier than classical HCV antibodies. However, E2 antibodies eventually appeared in all nine patients. The recombinant E2 might be a candidate antigen for future HCV antibody assays.

Detection and distribution of hepatitis C-specific antigens in naturally infected liver.

Hepatitis C virus antigen expression was examined using peptide antibodies in liver tissue taken at biopsy from four chronic carriers of hepatitis C virus. Hepatitis C virus antigens E2/NS1, NS3, NS4 and NS5 were widespread in unfixed frozen liver sections and were present as distinct granules or foci within the cytoplasm of hepatocytes and in infiltrating lymphocytes in portal tracts. Fixation of frozen sections with 1% formalin improved the histological appearance of the tissue section without reducing the sensitivity of antigen detection. However, in tissue sections fixed in acetone, chloroform, carbon tetrachloride or methyl carnoys, detection of all hepatocyte-specific hepatitis C virus antigens was significantly reduced. Dual immunostaining of liver sections for lymphocyte cluster of differentiation markers and hepatitis C virus antigens determined that a high proportion of cluster of differentiation 20-positive B cells and cluster of differentiation 4-and cluster of differentiation 8-positive T cells, predominant in lymphoid aggregates, were positive for hepatitis C virus antigens.

Immunoglobulin M and A antibodies to hepatitis C core antigen in chronic hepatitis C virus infection.

To determine the prevalence and clinical significance of IgM and IgA antibody to hepatitis C virus (HCV) core antigen in chronic HCV infection, sera from 47 patients were tested for immunoglobulin class M (IgM) and immunoglobulin A (IgA) antibody to HCV core antigen by solid-phase enzyme-linked immunoassay using a recombinant core protein (aa1-150). Results were correlated with the clinical, biochemical and histological parameters, serum HCV RNA levels (determined by branched DNA signal amplification assay), and subsequent clinical response to interferon-alpha therapy. IgM anti-HCV core was detected in 11 patients (23.4 percent). There was no correlation between the presence of IgM anti-HCV core and the clinical features (sex, age, mode of acquisition), biochemical parameters (serum ALT, AST, alkaline phosphatase, and albumin level), autoimmune markers [serum globulin levels, anti-nuclear antibody (+ at < 1:80 in 7/47 patients)], serum HCV RNA levels, subsequent response to interferon-alpha therapy, and the histological features. Immunoglobulin A anti-HCV core was not detected in any of the patients. The presence of IgM ant-HCV core in a proportion of patients with chronic HCV infection indicates that the presence of serum IgM anti-HCV core may not be unique to acute HCV infection.

Optimization for the detection of hepatitis C virus antigens in the liver.

To optimize the detection of hepatitis C viral antigens in liver tissue, cryostat and formalin-fixed, paraffin-embedded liver sections from 21 patients with chronic hepatic C viral infection were studied. For cryostat sections, six different fixatives were compared. Sixteen primary antibodies were tested: nine different mouse monoclonal anti-hepatitis C virus-core antibodies, a human monoclonal anti-hepatitis C virus-non-structural 4, and six rabbit polyclonals directed against synthetic peptides of the hepatitis C virus core, envelope, and non-structural 3, non-structural 4, non-structural 5. Three detection systems, 3- and 5-step peroxidase-antiperoxidase and avidin-biotin complex, were examined. In cryostat sections, acetone/chloroform formation consistently produced the best signal-to-background ratio. Five anti-hepatitis C virus-core monoclonals which recognize amino acid sequence 26-45 of the hepatitis C virus-core region consistently detected the viral antigen, but not the monoclonals directed against 39-74 of the hepatitis C virus-core region. The human anti-hepatitis C virus-non-structural 4, which reacts to amino acid sequence 1700-1705, also regularly detected viral antigen. The rabbit polyclonals produced either negative or nonspecific staining. The 5-step peroxidase-antiperoxidase provided the strongest signal and the avidin-biotin system produced high background consistently. Overall, hepatitis C virus core and non-structural 4 antigens were detected in 71% and 57% of the patients studied. Of the 16 patients seropositive for hepatitis C virus RNA, 75% and 69% had detectable hepatitis C virus core and non-structural 4, in contrast to 60% and 20% of the five hepatitis C virus RNA seronegative patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical detection of the NS4 antigen of hepatitis C virus and its relation to histopathology.

The immunohistochemical localization of the hepatitis C virus (HCV) nonstructural antigen 4 (NS4) was investigated in formalin-fixed human liver biopsy samples taken from 10 patients who were anti-HCV positive. NS4 was detected within the cytoplasm of hepatocytes in all HCV-positive patients studied, but not in the mononuclear cell infiltrates, bile duct epithelium, or endothelial cells. A high proportion of hepatocytes appeared positive, but the staining intensity was variable. After a coded histological evaluation of the liver tissue, the pattern of liver injury was shown to have no significant correlation with antigen-positive hepatocytes, and no direct relationship was observed between the distribution of antigen-positive hepatocytes and areas of hepatocyte necrosis. The staining pattern was considered to be specific because liver samples from patients chronically infected with hepatitis B virus or from uninfected individuals were negative. Furthermore, no staining was noted when either preimmune rabbit serum or anti-NS4 adsorbed against the specific synthetic peptide was substituted for the primary antibody.

Hypervariable 5'-terminus of hepatitis C virus E2/NS1 encodes antigenically distinct variants.

Synthetic peptides representing sequences encoded at the 5'-terminus of E2/NS1 in hepatitis C virus (HCV) were constructed. Peptides synthesized based on the sequences of four distinct HCV isolates were used to develop enzyme immunoassays (EIAs) for detection of antibodies in chronic HCV patients and in HCV-infected plasma donors. HCV sequence-specific antibodies were detected among patients with chronic HCV from the United States and Italy at frequencies of 22.2% and 55.8%, respectively. Similarly, sequence-specific antibodies were detected in 54.6% of U.S. and 55.6% of Japanese commercial plasma donors who had previous evidence of HCV exposure. Our data support earlier findings of geographic variability among HCV variants. The region encoded by amino acids (aa) 380-436 was shown to contain at least one variant-specific and one conserved epitope. The data further indicate that a majority of patients chronically infected with HCV (58.1% U.S., 68.8% Italy) have antibodies directed to the 5'-terminus of the E2/NS1 gene product. We conclude that genotypic variability within the E2/NS1 gene of HCV results in antigenically distinct variants.

Localisation of hepatitis C virus proteins in infected liver tissue by immunofluorescence.

Hepatitis C virus (HCV) antigen expression was examined by immunohistochemical staining in liver tissue taken at biopsy from 8 anti-HCV positive patients. Frozen liver sections were stained by indirect immunofluorescence for capsid, E2/NS1, NS3, NS4 and NS5 using polyclonal antibodies raised to synthetic peptides from these regions. The antigens E2 and NS3 were localised in scattered hepatocytes and also in cells within and around areas of inflammation. A weaker signal was observed for NS4 and NS5 and no signal was seen for capsid antigen. No staining was seen in liver tissue from 9 individuals, including 3 hepatitis B virus-positive and 2 hepatitis delta virus/positive patients, who were negative for serological markers of HCV. The specificity of the staining reaction was also confirmed by the lack of staining in HCV-positive liver samples, after the antisera was pre-adsorbed against the specific peptide. Collectively, the data suggests that HCV may not only be hepatotropic but also lymphotropic, and this may be an important factor in the pathogenesis of HCV infection.

Risk of liver disease in HCV-seropositive kidney transplant recipients.

OBJECTIVE: This study determined whether renal allograft recipients with antibodies to hepatitis C virus (HCV) at the time of transplantation experienced increased morbidity or mortality from hepatitis, liver disease, or hepatocellular carcinoma compared with patients without anti-HCV. SUMMARY BACKGROUND DATA: Chronic liver disease is a cause of significant morbidity and mortality after kidney transplantation and the contribution of HCV to this problem has not been determined. The recent characterization of the HCV genome has resulted in the development of screening tests for antibody to HCV, allowing the identification of end-stage renal disease patients with anti-HCV who are candidates for transplantation. The risk to these patients for the development of hepatic complications after subsequent transplantation is unknown. METHODS: Archived sera obtained from 163 kidney transplant recipients at the time of transplantation were tested for anti-HCV using the Abbott HCV 2.0 second-generation test system. Sera containing anti-HCV were further analyzed for reactivity against specific HCV recombinant proteins, including core, NS3 (c33c), and NS4 (c100-3), to determine whether a pattern could be identified in patients with hepatic complications. The follow-up of all patients was current (mean length of follow-up was 33 months) to identify patients with hepatic complications. All patients had previously been tested for HBSAg. RESULTS: Twenty-nine patients (18%) had anti-HCV and three (1.8%) had HBSAg. Forty-five patients (28% of total) had transient elevations of AST or ALT without subsequent evidence of liver disease. Three patients had a syndrome of acute hepatitis. Chronic liver disease developed in only six patients (3.6%) after transplantation. Four had anti-HCV only, one had HBSAg only, and one was positive for both. However, of the 29 patients with anti-HCV, chronic liver disease developed in 5 (17%), including 1 patient who was positive for HBSAg. No patient had hepatocellular carcinoma. CONCLUSIONS: Perturbations of liver function were common in the kidney transplant recipients studied, most were self-limited, and few were associated with evidence of viral hepatitis. The risk of developing

Lack of protective immunity against reinfection with hepatitis C virus.

Some individuals infected with hepatitis C virus (HCV) experience multiple episodes of acute hepatitis. It is unclear whether these episodes are due to reinfection with HCV or to reactivation of the original virus infection. Markers of viral replication and host immunity were studied in five chimpanzees sequentially inoculated over a period of 3 years with different HCV strains of proven infectivity. Each rechallenge of a convalescent chimpanzee with the same or a different HCV strain resulted in the reappearance of viremia, which was due to infection with the subsequent challenge virus. The evidence indicates that HCV infection does not elicit protective immunity against reinfection with homologous or heterologous strains, which raises concerns for the development of effective vaccines against HCV.

Enhanced sensitivity of a second generation ELISA for antibody to hepatitis C virus.

A second generation ELISA for combined detection of antibodies to three hepatitis C virus (HCV) recombinant proteins, i.e. C100, C33c and core, was compared with a first generation anti-HCV ELISA in which only antibodies to C100 are detected. The results of the ELISAs were evaluated in 225 haemophilia patients (panel A) and 44 patients with non-A, non-B (NANB) hepatitis (panel B). HCV infection was established by cDNA-polymerase chain reaction (PCR) (in panel B only) and by studying the anti-HCV reaction patterns in 4 separate ELISAs for detection of antibodies to the recombinant proteins C100, C33c, core and a combination of two synthetic peptides sp67/65 derived from the C100 region. The sensitivity for the detection of HCV infection had increased from 0.92[95% confidence interval (CI): 0.87-0.95] to 1.00 (95% CI: 0.89-1.00) in haemophiliacs and from 0.84 (95% CI: 0.66-0.95) to 1.00 (95% CI: 0.89-1.00) in NANB hepatitis patients when the second generation ELISA was used instead of the first generation ELISA. Concurrently the chance of a false negative result was reduced in panel A and B from 0.37 to 0 and from 0.28 to 0, respectively. Analysis of anti-HCV reaction patterns revealed that 172 of 206 (83.5%) anti-HCV ELISA-reactive haemophilia patients had antibodies to all 4 antigens tested. In the NANB hepatitis patients 18 of 31 (58.1%) anti-HCV ELISA-reactive subjects reacted with 4 antigens. In the PCR tested panel of NANB hepatitis patients 2 subjects who showed antibody reactivity to only one antigen and 5 patients with reactivity to 2 antigens were PCR-positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of hepatitis C virus antigen(s) by immunohistochemistry on fixed-embedded liver tissue.

Using two sources of primary antibodies, we immunohistochemically stained hepatitis C virus-related antigen(s) on fixed-embedded liver specimens. These antigens were localized in the cytoplasm of hepatocytes. The results obtained serologically correlated well with immunohistochemistry.

Antibodies to recombinant and synthetic peptides derived from the hepatitis C virus genome in long-term-studied patients with posttransfusion hepatitis C.

Eight of 13 Swedish patients (62%), studied prospectively, who developed posttransfusion non-A, non-B hepatitis (PT-NANBH) had earlier been found to seroconvert for antibodies to hepatitis C virus (anti-HCV) c100-3 in the first-generation anti-HCV enzyme-linked immunosorbent assay 1-18 (mean, 8) weeks after onset of hepatitis. By using a second-generation test utilizing antigens encoded by the core NS3 and NS4 region of HCV, a further four patients non-reactive to c100-3 (NS4) were found to seroconvert. Thus 12 of 13 (92%) Swedish patients with PT-NANBH were shown to have HCV infection. In addition, the serologic reactivity for several individual synthetic peptides and/or recombinant HCV proteins was studied in seven anti-HCV c100-3 seroconverts studied long-term after onset of acute PT-HCV infection. No special patterns were found that could differentiate patients who recovered from those who developed chronic HCV infection. It was concluded that the addition of new recombinant antigens derived from the core and NS3 region to c100-3 (NS4) both improved the sensitivity of the anti-HCV test and shortened the window phase to seroconversion.

IgM-antibody response to hepatitis C virus antigens in acute and chronic post-transfusion non-A, non-B hepatitis.

A specific IgM solid-phase enzyme-linked immunoassay for the diagnosis of a recent infection by hepatitis C virus (HCV) was developed. The assay utilizes a structural antigen encoded by sequences at the 5' end of HCV (core region) and non-structural (NS) antigens encoded by the NS-3 (33c) and NS-4 (c100-3) regions of the HCV genome. Serial serum samples from several clinically diagnosed post-transfusion non-A, non-B hepatitis patients were analyzed for anti-HCV IgM. This antibody was frequently but transiently detected. Anti-HCV core IgM was more frequently detected than anti-c100-3 or anti-33c IgM. In individuals who resolved their HCV infection or progressed to chronicity, anti-HCV IgM was produced transiently at or near the onset of clinically diagnosed acute hepatitis.