Efficacy of a polyvalent inactivated-virus vaccine in protecting mice from infection with clinical strains of group B coxsackieviruses.

A polyvalent vaccine developed from formalin-inactivated prototype strains of coxsackieviruses group B1-6 was tested for its ability to protect mice from acute infection with clinical strains. Adolescent male CD1 mice received an intraperitoneal injection, repeated once or twice at 8 day intervals, containing 0.3 ml placebo or vaccine. Eight days after the final dose of vaccine, groups of 4 mice were challenged with 1 x 10(4) plaque-forming units of a test strain of group B coxsackievirus, and killed 3 days later. The mean neutralizing antibody titers for the 29 strains tested (4 mice/strain, log2) were 2.2 +/- 0.6, 3.3 +/- 0.9 or 6.4 +/- 1.7 after 1, 2 or 3 doses of vaccine, respectively. In mice receiving 2 or 3 doses of vaccine, titers of virus were significantly lower in the pancreas and/or blood in 7/14 or 14/15 strains, respectively, compared to unvaccinated infected controls. Uninfected, vaccinated mice failed to develop islet cell autoantibodies, histopathological abnormalities in the pancreas, or evidence of viral RNA in the pancreas 12 weeks after 3 doses of vaccine. Thus, prophylaxis with a polyvalent, inactivated-virus vaccine reduced the severity of acute infection with clinical strains of coxsackie group B viruses. A schedule of 3 doses of vaccine was superior to 1 or 2 doses.