ABSTRACT
There is limited information on the direct role of the neutralizing antibody responses against hepatitis C virus (HCV) infection or methodologies to study them. Previously we have demonstrated that interleukin-10 (IL-10) administered to chronic hepatitis patients led to a decrease in disease activity, but an increase in HCV viral burden. The mechanism behind this is unknown. The objective of this study was to examine the antibody response in IL-10-treated patients. To establish a neutralization antibody assay, HCV-positive and HCV-negative sera were collected and incubated with HCV strain JFH-1 particles before culture with Huh 7.5 cells. Viral replication was measured a week later by either indirect immunofluorescence assay (iIFA) or real-time reverse transcriptase polymerase chain reaction (RT-PCR). After validation of the methodology, the sera from 30 previously-described subjects of a group previously treated with IL-10 were tested for the neutralization capacity of their antibodies. The amount of total anti-HCV antibody in the sera was also measured by direct staining of HCV full-length replicon cells. With this validated neutralization assay for anti-HCV antibodies we found that HCV-neutralizing antibodies are universally present, but with significantly different titers. In patients who were treated with IL-10, the total anti-HCV antibody titers appear to be constant, but with significantly decreased antibody neutralization activity. Our study validates an assay to quantitatively determine the presence and strength of HCV-specific neutralizing antibodies. We have found that IL-10-treated patients have significantly lower HCV antibodies, but maintain the total anti-HCV antibody titer, suggesting a novel mechanism by which IL-10 treatment increases viral load in patients.
