Abstract
Cortisone is a highly potent inhibitor of influenza virus synthesis in the chick embryo, inducing manifest inhibition in doses of 0.1 to 1.0 microg/egg. Inhibition of viral synthesis is only temporarily manifest. As infection continues, the negation by cortisone of the self-limiting effects of viral autointerference obscures the coincident cortisone effect on synthesis. The inhibitory effect of cortisone may be induced late in the course of viral multiplication, after conclusion of the latent period. It is proposed that inhibition of viral synthesis with cortisone is a corollary of the steroid's inhibitory effects on growth and protein synthesis of the infected host. The role of adrenal corticoids in the regulation of infection with obligate intracellular parasites deserves continued investigation.