Antibody responses to hepatitis C virus hypervariable region 1: Evidence for cross-reactivity and immune-mediated sequence variation

Abstract

Sequence heterogeneity of hepatitis C virus (HCV) is unevenly distributed along the genome, and maximal variation is confined to a short sequence of the HCV second envelope glycoprotein (E2), designated hypervariable region 1 (HVR1), whose biological function is still undefined. We prospectively studied serological responses to synthetic oligopeptides derived from HVR1 sequences of patients with acute and chronic HCV infection obtained at baseline and after a defined follow-up period. Extensive serological cross-reactivity for unrelated HVR1 peptides was observed in the majority of the patients. Antibody response was restricted to the IgG1 isotype and was focused on the carboxyterminal end of the HVR1 region. Cross-reactive antibodies could be readily elicited following immunization of mice with multiple antigenic peptides carrying HVR1 sequences derived from our patients. The vigor and heterogeneity of cross-reactive antibody responses were significantly higher in patients with chronic hepatitis compared with those with acute hepatitis and in patients infected with HCV type 2 compared with patients infected with other viral genotypes (predominantly type 1), which suggest that higher time-related HVR1 sequence diversification previously described for type 2 may result from immune selection. The finding of a statistically significant correlation between HVR1 sequence variation, and intensity, and crossreactivity of humoral immune responses provided stronger evidence in support of the contention that HCV variant selection is driven by the host's immune pressure. (HEPATOL-OGY 1999;30:537-545.)Hepatitis C virus (HCV) causes chronic infection in more than 60% of exposed individuals through pathogenetic mechanisms that are still poorly understood. 1 Similarly to human immunodeficiency virus (HIV), HCV is able to persist for a virtually indefinite period of time in the host, despite the coexistence of virus-specific immune responses. 2 How HCV induces chronic infection in the face of detectable cellular and humoral immune responses is currently unknown, but the ability of the virus to undergo rapid and substantial sequence modifications is thought to be a major factor in this process. [2][3][4][5][6][7][8][9][10][11] Sequence variation is unevenly distributed along the HCV genome with maximal nucleotide and aminoacid replacements being localized in a stretch of 31 residues at the N-terminus of the second envelope glycoprotein (E2) region named hypervariable region 1 (HVR1). 12 Sequential studies of sequence changes in acute and chronic HCV infection have shown that viral variants are continuously being selected in this region 13,14 and, therefore, HVR1 variation may be a mechanism by which HCV evades neutralizing responses, leading to persistent infection.Most studies point to HVR1 as the major immunogenic domain of E2, although the presence of additional B-cell sites outside HVR1 has been documented, 15 and a conserved B-cell epitope, only partially overlapping with HVR1, has been recently described that competes for ...

Monoclonal Antibodies with Broad Specificity for Hepatitis C Virus Hypervariable Region 1 Variants Can Recognize Viral Particles

“…To examine binding to naturally occurring HVR1 isolates, two panels of previously validated biotinylated peptides of 16-and 27-aa residues (9,15) were used on streptavidin-coated ELISA plates. Similarly, to determine the fine specificity of murine hybridomas, 14 overlapping biotinylated 14-mers scaled by one residue and covering the entire HVR1 region (amino acids 384 -410) were synthesized based on the sequence of the HVR1 consensus profile reported previously (15).…”

“…Specifically, MAPs were coated onto 96-well microplates at a concentration of 10 g/ml in 50 mM bicarbonate buffer (pH 9.6) and incubated overnight at 4°C. To detect binding to peptides derived from natural HVR1 isolates or to determine the fine specificity of mAb binding, biotinylated 27-, 16-, and 14-mers were added to streptavidin-coated ELISA plates exactly as previously described (9). Coating of ELISA plates with Galantus nivalis lectin (GNA; Sigma, St. Louis, MO) was required for adsorption of E2 chimeric glycoproteins.…”

“…Streptavidin-coated ELISA plates were incubated with a number of biotinylated 16-mers derived from naturally occurring HVR1 sequences as previously described (9). Human sera (n ϭ 4) from patients with chronic HCV infection were diluted 1/10 in PBS containing 0.05% Tween 20 and added to the wells for 5 min at 37°C as previously described (22).…”

“…Several lines of experimental evidence argue in favor of a dominant role of positive selection for amino acid changes in driving the pattern of HVR1 genetic diversification (1,2). Prospective studies of serological responses to synthetic oligopeptides derived from HVR1 sequences of patients with acute and chronic HCV infection showed apparently extensive serological cross-reactivity for unrelated HVR1 peptides in the majority of the patients (3)(4)(5)(6)(7)(8)(9). A significant correlation was found between HVR1 sequence variation and the intensity and cross-reactivity of humoral immune responses, strongly supporting the contention that HCV variant selection is driven by the host immune response (9).…”

“…Prospective studies of serological responses to synthetic oligopeptides derived from HVR1 sequences of patients with acute and chronic HCV infection showed apparently extensive serological cross-reactivity for unrelated HVR1 peptides in the majority of the patients (3)(4)(5)(6)(7)(8)(9). A significant correlation was found between HVR1 sequence variation and the intensity and cross-reactivity of humoral immune responses, strongly supporting the contention that HCV variant selection is driven by the host immune response (9). Additional data in support of Ab-mediated HVR1 variant selection derive from studies reporting that persistent viremia was associated with higher intersample antonymous vs synonymous substitutions, suggesting that HVR1 can function as an immunological decoy, stimulating a strong immune response that would be responsible for variant selection but would be ineffective to clear HCV (10).…”