Protection against Chronic Hepatitis C Virus Infection after Rechallenge with Homologous, but Not Heterologous, Genotypes in a Chimpanzee Model

An open question for hepatitis C virus (HCV) vaccine development is whether the various genotypes of this virus protect against the development of chronic infection after heterologous infection with different genotypes. We approached this question by challenging chimpanzees that had recovered from HCV genotype la or 1b infection with 6 heterologous genotypes as well as with a homologous genotype (for chimpanzees originally infected with genotype la). All 9 chimpanzees rechallenged with a homologous genotype developed self-limited infections. Of 11 chimpanzees challenged with 100 chimpanzee infectious doses of heterologous genotypes, 6 developed self-limited infections, with peak viral loads in acute-phase serum that were ∼5-fold lower than those seen during primary infections. One chimpanzee (which had recovered from genotype 1b infection and was rechallenged with genotype 6a) did not develop viremia but did show an anamnestic cell-mediated immune response after rechallenge. Four of the 11 chimpanzees rechallenged with heterologous genotypes developed chronic infections with the genotypes used for rechallenge. These findings suggest that a universally protective HCV vaccine may need to incorporate epitopes from multiple genotypes.