An Antigenically Diverse, Representative Panel of Envelope Glycoproteins for Hepatitis C Virus Vaccine Development

Background and Aims Development of a prophylactic hepatitis C virus (HCV) vaccine will require accurate and reproducible measurement of neutralizing breadth of vaccine-induced antibodies. Currently available HCV panels may not adequately represent the genetic and antigenic diversity of circulating HCV strains, and the lack of standardization of these panels makes it difficult to compare neutralization results obtained in different studies. Here, we describe the selection and validation of a genetically and antigenically diverse reference panel of 15 HCV pseudoparticles (HCVpp) for neutralization assays. Methods We chose 75 envelope (E1E2) clones to maximize representation of natural polymorphisms observed in circulating HCV isolates, and 65 of these clones generated functional HCVpp. Neutralization sensitivity of these HCVpp varied widely. HCVpp clustered into 15 distinct groups based on patterns of relative sensitivity to seven broadly neutralizing monoclonal antibodies (bNAbs). We used these data to select a final panel of 15 antigenically representative HCVpp. Results Both the 65 and 15 HCVpp panels span four tiers of neutralization sensitivity, and neutralizing breadth measurements for seven bNAbs were nearly equivalent using either panel. Differences in neutralization sensitivity between HCVpp were independent of genetic distances between E1E2 clones. Conclusions Neutralizing breadth of HCV antibodies should be defined using viruses spanning multiple tiers of neutralization sensitivity, rather than panels selected solely for genetic diversity. We propose that this multi-tier reference panel could be adopted as a standard for the measurement of neutralizing antibody potency and breadth, facilitating meaningful comparisons of neutralization results from vaccine studies in different laboratories.