Level of Human Antibodies Targeting HCV E1/E2 Peptides and Spontaneous Clearance of HCV in Blood Donors.

BACKGROUND: Hepatitis C virus (HCV) is a major health problem worldwide particularly in Egypt. The humoral immune response has an important function in the control of HCV infection. The aim of this study was to investigate the role of neutralizing antibodies in Hepatitis C Virus (HCV) clearance in infected individuals. METHODS: This study was carried out on apparently healthy blood donors (n = 200). Detectable HCV antibodies were assessed by commercial ELISA and specific human immunoglobulins targeting peptides derived from HCV E1/E2 glycoproteins were measured in donors' blood using an in house optimized ELISA. Human IgG purification was carried out from positive HCV RNA and negative HCV RNA samples in order to evaluate its neutralizing activity in vitro using Huh 7 cells. RESULTS: The studied cohort included 96/200 subjects who tested positive for HCV antibodies, among which 56/96 (58%) samples were positive for HCV RNA (Group 1) and 40/96 (42%) samples had undetectable HCV RNA (Group 2). ELISA results showed that Human HCV immunoglobulin (HHI) targeting HCV E1 synthetic peptide (a.a. 315 - 323) was detectable in 63/96 (66%) and HHI targeting HCV E2 (a.a. 412 - 419) tested positive in 14/96 (15%) while 19/96 (20%) were positive for HCV E2 (a.a. 517 - 531). HHI higher than the cutoff level against peptide HCV E1 (a.a. 315 - 323) was detected in 22/63 (35%) in Group 2 and positive in 41/63 (65%) in Group 1. HHI against peptide HCV E2 (a.a. 412 - 419) was positive in 7 (50%) blood donors in Group 2 and also positive in 7 (50%) of Group 1. While HHI targeting HCV E2 (a.a. 517 - 531) was positive in 11 (60%) in Group 2 compared with 8 cases (40%) in Group 1. Purified human antibodies from cases positive for HCV antibodies and negative for HCV RNA showed in vitro neutralization at concentrations 30 and 10 µg/mL while the same concentration of purified human IgG from cases positive for HCV RNA showed no viral neutralization. CONCLUSIONS: The tested epitope(s) derived from HCV envelope E1 and E2 are important for viral clearance and hence can be used for HCV vaccine development.

Establishment of hybrid cell lines producing monoclonal antibodies to a synthetic peptide from the E1 region of the hepatitis C virus.

We aimed at establishing hybridoma cells secreting monoclonal antibodies (mAbs) against E1 synthetic peptide of HCV. BALB/c mice were immunized with HCV E1-synthetic peptide (GHRMAWDMM) and its spleenocytes were fused with the P3NS1 myeloma cell line. Two highly reactive and specific mAbs (10C7 IgG2b mAb, and 10B2 IgG1 mAb) were generated. The target HCV E1 antigen was identified at approximately 38 kDa in serum of infected individuals. A newly developed ELISA detected the target antigen in 90% of sera from HCV RNA infected individuals with a specificity of 84%. So, the generated mAbs may provide promising probes for serodiagnosis of HCV infection.

Circulating viral core and E1 antigen levels as supplemental markers for HCV chronic hepatitis.

The performance of polyclonal monospecific rabbit anti-sera raised against synthetic peptides derived from conserved HCV sequences of genotype 4 was evaluated for efficient detection of viral core and E1 antigens in circulating immune complexes (ICs) precipitated from 65 serum samples of HCV patients. The infection was established in those patients by the presence of HCV RNA in their sera. A novel enzyme-linked immunosorbent assay (ELISA) was developed for the detection of HCV core and E1 antigen in serum samples. Western blot analyses were used to demonstrate the presence of the core and E1 target antigen in serum samples. The mean OD readings of both core and E1 antigens were significantly higher (P < 0.05) among the viremic patients when compared to controls. Also a significant positive correlation (P < 0.05, r = 0.98) between the values of both core and E1 was recorded. Western blot analysis based on monospecific antibodies against core and E1 recognized the 38-kDa and 88 -kDa bands respectively in the sera of all infected patients. No specific reaction was observed with the sera from uninfected individuals. Interestingly the results of core and E1 antigen levels displayed no positive correlation with the HCV copy number as measured by bDNA. Liver enzymes (ALT and AST) showed a moderate positive correlation (r = 0.44 and 0.47 respectively) with the viral core antigens level. The same trend holds true for E1 (r = 0.43 and 0.64 for ALT and AST respectively). HCV load in infected patients revealed extremely poor correlation with serum ALT and AST levels (r = 0.022 and 0.002 respectively). In conclusion we present a new combination of serological tools correlating with liver enzyme levels that could be utilized as supplemental tests to viral load testing. Also, a sensitive and specific immunoassay was developed for the detection of HCV core and E1 in human serum. This test can be applied for laboratory diagnosis of HCV infection.