Viruses and Plasmids. Hepatitis A virus strains HM175/clone 1 and 18f, and coxsackievirus (CV) serotypes B1, A3 and A5 strains used in this study were obtained from ATCC (Manassas, VA) and further grown in FRhK4 cells [18] . The plasmid pHAV/7 contains a full length cDNA copy of wild type HAV strain HM175 cloned into the vector pGEM-1 [19] that was grown and purified as previously described [20] . HM175 clone1 and 18f are culture-adapted strains derived from continuous culture passage of the wildtype strain HAV HM175 [21] .