Antigenic comparison of Yuli and Vnukovo-32 virus strains in monkeys: specific protection by commercial antirabies preparations.

A combined vaccination schedule using commercial antirabies immunoglobulin G and experimental vaccine from strains Vnukovo-32 or Yuli beginning 2 hr before intracerebral (i.c.) challenge with a high dose of Yuli virus conferred no protection to Cercopithecus aethiops monkeys. In monkeys inoculated into lip with a middle dose of Yuli virus, administration of large amounts of antirabic IgG (up to 5000 national units, NU/kg) had a clearcut effect. The disease in Yuli virus-infected monkeys showed typical signs of acute encephalitis with lethal outcome, although one animal which developed typical encephalitis recovered as evidenced by increased virus-neutralizing antibodies in its serum. Inflammatory and degenerative lesions developed in the CNS of animals with signs of acute encephalomyelitis; their intensity was less prominent in those monkeys which underwent the combined treatment. In the cytoplasm of brain neurons of monkeys infected with Yuli virus relatively small Babes-Negri bodies with more or less apparent internal structure were detected.