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.