Reovirus type 3 synthesizes proteins in interferon-treated HeLa cells without reversing the antiviral state

Treatment of HeLa cells with human lymphoblastoid interferon (IFN-alpha) does not inhibit reovirus type 3 protein synthesis during virus infection. In contrast, reovirus translation is blocked by treatment of L cells with mouse IFN-alpha. The (2'-5')A synthetase activity is induced in HeLa cells by IFN-alpha treatment and is activated after reovirus infection, since cell lysates from these cells synthesize in vitro (2'-5')A oligonucleotides. The IFN-induced protein kinase activity is also triggered in those lysates upon dsRNA addition. Thus, contrary to DNA-containing viruses, such as vaccinia virus or adenovirus, reovirus infection does not destroy or reverse the IFN-induced antiviral state. In support of this conclusion, superinfection with poliovirus or vesicular stomatitis virus of reovirus-infected HeLa cells treated with IFN leads only to a blockade of translation of the former viruses. These results provide a remarkable example where in the same cells doubly infected with two different viruses, the antiviral state induced by IFN-alpha is manifested by selectively inhibiting translation of one kind of virus (poliovirus or vesicular stomatitis virus) without affecting the translation of reovirus type 3. In addition, these results indicate that the resistance of reovirus translation to inhibition by IFN is different from the mechanism of resistance induced by DNA-containing viruses.