Potentiation by levamisole, methisoprinol, and adenine or adenosine of the inhibitory activity of human interferon against encephalomyocarditis virus

The antiviral action of different human interferons against encephalomyocarditis virus in HeLa cell cultures was analyzed. Cell treatment with levamisole (200 micrograms/ml), methisoprinol (1 mg/ml), or adenine or adenosine (33 or 100 micrograms/ml, respectively) potentiated the anti-encephalomyocarditis virus activity of human interferon by 8- to 32-fold. A higher level of potentiation (256-fold) was achieved either by combined treatments with levamisole plus methisoprinol or by treatment with one of these compounds plus adenine or adenosine.