A structural protein encoded by the 5' region of the hepatitis C virus genome efficiently detects viral infection

Sites of vulnerability in HCV E1E2 identified by comprehensive functional screening

The E1 and E2 envelope proteins of hepatitis C virus (HCV) form a heterodimer that drives virus-host membrane fusion. Here, we analyze the role of each amino acid in E1E2 function, expressing 545 individual alanine mutants of E1E2 in human cells, incorporating them into infectious viral pseudoparticles, and testing them against 37 different monoclonal antibodies (MAbs) to ascertain full-length translation, folding, heterodimer assembly, CD81 binding, viral pseudoparticle incorporation, and infectivity. We propose a model describing the role of each critical residue in E1E2 functionality and use it to examine how MAbs neutralize infection by exploiting functionally critical sites of vulnerability on E1E2. Our results suggest that E1E2 is a surprisingly fragile protein complex where even a single alanine mutation at 92% of positions disrupts its function. The amino-acid-level targets identified are highly conserved and functionally critical and can be exploited for improved therapies and vaccines.

Taxonomy of genus Hepacivirus. Application of palindromic nucleotide substitutions for the determination of genotypes of human hepatitis C virus species

The palindromic nucleotide substitutions (PNS) in the 5'-untranslated region (UTR) of Pestivirus RNA have been described as a new, simple and practical method for genotyping. Given the genetic relatedness between Pestivirus and hepatitis C virus species, the application of the method was investigated preliminarily on 180 isolates, including reference strains. The keys for hepatitis C virus identification have been determined at the genus, species, genotype and subtype levels. Secondary structure nucleotide substitutions were characteristics to the genus included in a complex stem-loop structure composed of 112-115 nucleotides. Due to the worldwide importance of hepatitis C virus, and the difficulties encountered in the control of the disease, it is, therefore, important to understand the genetic aspects of the virus. The application of the PNS method might represent an additional useful tool for determining the genetic variations among hepatitis C virus strains. The identification of viral types or subtypes based on genetic changes should improve our understanding of hepatitis C virus and might provide markers for biological differences, such as virulence, and improve understanding of the evolution of the virus.

Humoral immune response to hypervariable region 1 of the putative envelope glycoprotein (gp70) of hepatitis C virus

We recently found that alterations of amino acids in hypervariable region 1 (HVR1) of the putative envelope glycoprotein (gp70) of hepatitis C virus (HCV) occurred sequentially in the chronic phase of hepatitis at intervals of several months. This finding suggests that mutations in HVR1 are involved in the mechanism of persistent chronic HCV infection involving escape from the immunosurveillance system. To explore this possibility, we examined the humoral immune response to HVR1 with our assay system, in which immunoprecipitation was carried out with sera from patients by using an HVR1 (27-amino-acid) dihydrofolate reductase fusion protein synthesized by in vitro transcription and translation. Results showed that HVR1 contains a sequence-specific immunological epitope that induces the production of antibodies restricted to the specific viral isolate. Furthermore, analysis of the kinetics of the appearance of antibodies in two patients with chronic hepatitis, with whom successive alterations of amino acids of HVR1 have been observed, showed that the titers of anti-HVR1 antibodies usually reached maximal levels several months after the isolation of HCV having the specific sequence of HVR1. This observation suggests that anti-HVR1 antibodies are involved in the genetic drift of HVR1 (minor antigenic variation) by immunoselection. However, the coexistence of HVR1 as an antigen and its specific antibody was sometimes observed. The possibility that HVR1 acts as a neutralizing epitope is discussed.

Clinical significance of antibodies to nonstructural and core proteins of hepatitis C virus in posttransfusion hepatitis patients during long-term follow-up

To clarify the long-term clinical significance, antibody to hepatitis C virus (HCV) was examined using core (p22) and nonstructural (C100-3) protein assays in sera of 18 patients with non-A,non-B posttransfusion hepatitis (PTH-NANB) who were selected retrospectively. Each patient had been followed for more than 5 years after the development of the disease. They were divided into three groups according to clinical outcome: acute hepatitis that resolved within 1 year, group 1 (n = 3); chronic hepatitis that resolved within 1-4 years, group 2 (n = 4); and chronic hepatitis that persisted for 5 years or longer, group 3 (n = 11). Sixteen of the 18 were positive for anti-C100-3 and anti-p22, one was positive for anti-p22 alone, and one was negative for both. In ten of the 16 (62.5%), anti-p22 appeared before anti-C100-3. The anti-C100-3 titer peaked about 12 months after disease onset in all cases and thereafter declined gradually, finally becoming negative in groups 1 and 2, while the titer fluctuated in group 3. The mean titer in group 3 at 12 months (69.2 units) significantly exceeded that of groups 1 (4 units) and 2 (8.2 units). Group 1 was seronegative for HCV antibodies and HCV RNA at the last examination, suggesting the cessation of HCV replication. Group 3 remained positive for those markers, indicating the continued replication of HCV.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of hepatitis C virus markers in patients with NANB hepatitis

10 different HCV-specific assays and RT-PCR of the 5' untranslated region of HCV RNA were used to analyze sixty-four patients with chronic NANB liver disease. Po, CP-9 and C22 antigens are located in the putative core; C33c in the putative NS3; C100-3 in the putative NS3/4; KCL in the putative NS4/5 and C825 is located in the putative NS5. GOR protein is not part of the HCV genome, but antibodies to it appear to be present in response to a hepatitis C infection. Positive rates were 91% for Po, 89% for CP-9, 94% for C22, 97% for C33c, 88% for C100-3 (Ortho, EIA), 86% for C100-3 (Abbott, EIA), 84% for C100-3 (Ohtsuka, RIA), 88% for KCL, 59% for C825, 58% for GOR, and 83% for RT-PCR. There were 8 cases which were negative by all anti-C100 tests. 7 of these cases were positive by other anti-HCV markers and/or PCR suggesting the need for improved blood screening assays. There is a variation in the relative reactivity for different markers with different samples. Of the tests employed, anti C33c shows the highest positivity rate.