Investigation of the mechanism of changes of RS character of neurovaccine in passages in the presence of bromodeoxyuridine.

Neurovaccinia virus propagated in the presence of bromodeoxyuridine loses the capacity to produce necrosis in the skin of rabbits. Mechanisms underlying this loss were studied. The population under study consisted predominantly of virus particles capable of producing necrosis (RS +) and a small portion of particles which had lost this capacity (RS-). An RSclone isolated from the population induced an inhibitor of interferon type in rabbit skin, which markedly inhibited reproduction of RS + virus strains and consequently the capacity of these strains to produce necrosis.