Early antibody response against hypervariable region 1 is associated with acute self-limiting infections of hepatitis C virus

Antibodies directed to hypervariable region 1 (HVR1) of hepatitis C virus (HCV) have recently been shown to neutralize the corresponding HCV isolate in vitro. We analyzed the appearance of antibodies directed to HVR1 during the course of infection in a large group of patients who have been infected by the same isolate of a HCV contaminated anti-D immunoglobulin (HCV-AD78). An enzyme-linked immunosorbent assay (ELISA) was established using a synthetic peptide to detect antibodies against the main HVR1 variant of HCV-AD78. 207 sera obtained at different time points post infection (p.i.) of 51 patients having either acute self- limiting (n = 28) or chronic infection (n = 23) were studied. Antibodies directed to HVR1 were found at least at one time point during the infection course in 15 of 28 patients (53%) having acute self-limiting infections and in 17 of 23 patients (74%) with chronic disease. The time of appearance of anti-HVR1 was significantly different between these two patient groups (P < .025) although appearance and titers of other HCV-specific antibodies were found to be similar at early time points p.i. In acute self-limiting infections 9 of 21 sera (43%) of respective patients with sera available within the first 6 months p.i. were anti-HVR1 positive. The highest prevalence of anti-HVR1 in this group of patients was within month 6 to 12 p.i. (64%). None of the sera available after 24 months p.i. had such antibodies. In contrast, only 2 of 15 sera (13%) of chronically infected patients with respective time points of sera were anti-HVR1 positive within the first 6 months p.i. and only 5 of 18 sera (28%) were positive within month 7 to 12 p.i. Seven patients with chronic HCV infections showed at least two consecutive anti-HVR1 negative early time points up to month 18 p.i. Prevalence of anti-HVR1 after 24 months p.i. was high (84%) in this group of patients and most of the patients maintained high levels of anti-HVR1 for up to 17 years p.i. Our findings suggest clearance of virus by respective neutralizing antibodies resulting in a self-limiting infection and may have implications for prognosis of the disease and also for any future vaccine development.