Assessment of hepatitis C virus permissiveness in iteratively genetically humanized mice

Hepatitis C virus (HCV) is an enveloped, positive-sense single-stranded
RNA virus causing chronic infections in over 50 million people who are at
risk of developing severe liver disease. Greater understanding of HCV
pathogenesis and vaccine development has been hampered by the lack of a
fully immunocompetent small-animal model permissive to infection. Rodents
are resistant to HCV infection due to a variety of factors at the levels
of viral entry and replication, many of which have been discovered within
the past decade. We hypothesized that a host environment can be
genetically engineered that would be more conducive to HCV infection.
Here, we present the generation and characterization of a series of mouse
lines bearing humanized alleles for CD81, occludin (OCLN), tripartite
motif containing 26 (TRIM26) and cyclophilin A (CypA), the murine
orthologs for which do not support HCV uptake and replication.
Additionally, we knocked out C-type lectin domain family 13 member A
(CD302) and complement C3b/C4b receptor 1 like (CR1L), which restrict HCV
infection in mouse hepatocytes. Intravenously, inoculation of mice
combining some or all of these mutant alleles did not increase viremia. To
ascertain that mouse adaptive immune responses do not rapidly clear any
putative low-level viremia, we engrafted hepatocytes from these
genetically complex mouse lines into immunodeficient liver-injury strains.
No cohort of mice presented with sustained HC viremia, although we
detected low-level viremia in a subset of transplant-recipient mice.
Collectively, albeit unsuccessful at supporting robust, sustained viremia,
these mouse mutant lines represent the most genetically advanced attempt
to-date to generate a mouse model of HCV infection, and will provide an
important platform for future genetic host adaptations and/or
complementary viral adaptation approaches.