A cytopathogenic variant of hepatitis A virus (HAVcyt/HB1.1) was isolated from persistently infected BS-C-1 cells by serial passages in FRhK-4 cells. This virus shows a rapid replication pattern and high final titers are obtained, which are main characteristics of cytopathogenic HAVs. Sequencing of the nontranslated regions and the coding regions for 2ABC and 3AB revealed that mutations are distributed all over these regions and that certain mutated sites correspond to those in other cytopathogenic HAV variants. Investigating the mechanisms causing the cytopathic effect in FRhK-4 cells infected with this variant, we found that an apoptotic reaction takes place.

The consequences of a hepatitis A virus (HAV) infection on cell-based antiviral responses and the interactions between virus and host cells resulting in persistent infections are poorly understood. In this report, we show that HAV does inhibit double-stranded (dsRNA)-induced beta interferon (IFN-␤) gene expression by influencing the IFN-␤ enhanceosome, as well as dsRNA-induced apoptosis, which suggests that both effects may be connected by shared viral and/or cellular factors. This ability of HAV, which preserves the sites of virus production for a longer time, may allow the virus to establish an infection and may be the presupposition for setting up persistent infections. Our results suggest that the inhibitory effect of HAV on the cellular defense mechanisms might not be sufficient to completely prevent the antiviral reactions, which may be induced by accumulating viral dsRNA, at a later stage of infection. However, HAV seems to counteract this situation by downregulation of viral replication and in the following production of viral dsRNA. This ability of noncytopathogenic HAV acts dominantly on cytopathogenic HAV in trans. The downregulation might ensure the moderate replication which seems necessary for inhibition of the antiviral mechanisms by HAV and therefore for the persistent state of the HAV infection.

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