Defining Breadth of Hepatitis C Virus Neutralization

Abstract

Extraordinary genetic diversity is a hallmark of hepatitis C virus (HCV). Therefore, accurate measurement of the breadth of antibody neutralizing activity across diverse HCV isolates is key to defining correlates of immune protection against the virus, and essential to guide vaccine development. Panels of HCV pseudoparticle (HCVpp) or replication-competent cell culture viruses (HCVcc) can be used to measure neutralizing breadth of antibodies. These in vitro assays have been used to define neutralizing breadth of antibodies in serum, to characterize broadly neutralizing monoclonal antibodies, and to identify mechanisms of HCV resistance to antibody neutralization. Recently, larger and more diverse panels of both HCVpp and HCVcc have been described that better represent the diversity of circulating HCV strains, but further work is needed to expand and standardize these neutralization panels.

Keywords: Flaviviridae; antibodies; hepatitis C virus; neutralizing breadth; viral diversity.

Figure 1

Genetic diversity of hepatitis C virus (HCV) E1E2 across subtypes and within a single subtype. Phylogenetic trees of E1E2 amino acid sequences. E1E2 amino acid sequences from multiple subtypes (A) or a single subtype (B) were downloaded from the LANL HCV sequence database. Not all known subtypes are shown. (C) E1E2 amino acid sequences of 10 individuals from the Irish anti-D cohort, who were all infected from the same inoculum (asterisk) between 1977 and 1978 (9). Sequences of virus from each individual are indicated with a different color. Trees were inferred using the Neighbor-joining method, with branch lengths drawn to scale. Subtypes are labeled. All three trees are on the same scale. Distances were computed using the JTT method. Analyses were performed in MEGA7 (10).

Figure 2

Neutralizing breadth of seven monoclonal antibodies measured using HCV cell culture (HCVcc) and HCV pseudoparticle (HCVpp) panels. Values shown are the percentage of 16 genotype 1–3 HCVcc isolates from the Copenhagen Hepatitis C Program (CO-HEP) neutralized with an IC₅₀ less than 10 µg/mL (74), or the percentage of 19 genotype 1 HCVpp isolates from Johns Hopkins University neutralized more than 50% by 10 µg/mL of mAb (72).