Experimental hepatitis A virus infection in guinea pigs.

Although many of the properties of hepatitis A virus (HAV) are known, several aspects of HAV pathogenesis are still not understood, such as the mechanism underlying the hepatotropism or HAV replication in extrahepatic sites. Detailed studies of these aspects were hampered mostly by the lack of accessible animal models, since only nonhuman primates are susceptible to experimental infections. An alternative animal model would also be of interest to assess the primary replication site and for the evaluation of the safety and efficacy of vaccines. A study was undertaken to determine whether HAV can infect guinea pigs and whether they are useful as a model for studying aspects of HAV pathogenesis and for the evaluation of vaccines. HAV variants adapted to primate or guinea pig tissue culture were used to inoculate guinea pigs intraperitoneally and by the oral route. The animals were observed for clinical disease, shedding of HAV in stools, viremia, seroconversion, evidence for liver damage by biochemical liver function tests, virus presence in the liver, development of hepatic histopathological changes, and occurrence of HAV in extrahepatic organs. The animals developed an active, clinically inapparent infection with specific histopathological changes in the liver. Although virus replication occurred, as shown by RT-PCR and isolation of infectious virus from feces and serum, it seems unlikely that guinea pigs are suitable for studying the clinical features of hepatitis A, because the clinical and laboratory parameters remained normal. However, guinea pigs appear useful for studying some aspects of HAV pathogenesis and for testing the safety of vaccines.