Occurrence of coxsackievirus hepatitis in baby rabbits and protection by a formalin-inactivated polyvalent vaccine.

Abstract

It was observed that 23-day-old New Zealand white rabbits came down with acute hepatitis demonstrable 3 days after intraperitoneal injection with 12 coxsackievirus group B strains. The model was used to evaluate a polyvalent, formalin-inactivated virus vaccine prepared with prototype strains of coxsackievirus groups B1-6. Seven-day-old animals received one intraperitoneal and two subcutaneous injections containing the vaccine or placebo. The regimen was repeated at 15 days of age. At 23 days of age, groups of rabbits were challenged with 1 x 10(5) plaque-forming units of a clinical strain of group B coxsackievirus and sacrificed 3 days later. The mean neutralizing antibody titer for the 12 strains tested (log2) was 4.5 +/- 1.0 eight days after the second dose of vaccine. In vaccinated animals, elevated liver function tests in the serum, and titer of virus and histopathologic abnormalities in the liver were significantly reduced for each strain tested compared with infected, unvaccinated controls. Cultures of the heart, skeletal muscle, pancreas, blood, and spleen were all negative. Thus, clinical strains of coxsackie group B viruses produced isolated hepatitis in baby rabbits. Prophylaxis with a polyvalent, inactivated-virus vaccine significantly reduced the severity of liver involvement for all 12 clinical strains tested.