Failure of killed Corynebacterium parvum in induction of protection in C57BL/6 mice against Babesia rodhaini challenge infection.

We examined the survival rate of C57BL/6 mice challenged with Babesia rodhaini 21 days post-killed Corynebacterium parvum (KCP) inoculation in comparison with ICR mice. All KCP-inoculated ICR mice survived the challenge infection, while all KCP-inoculated C57BL/6 mice died. To account in part for the difference in protective effects of KCP, stimulatory effects of KCP on splenic phagocyte chemiluminescence (CL) response were investigated in C57BL/6 and ICR mice. The KCP-inoculated ICR mice exhibited significantly higher CL values than ICR mice without KCP inoculation. No significant difference in CL value was observed between C57BL/6 mice with and without KCP inoculation. These results taken together, the lack of resistance of the KCP-inoculated C57BL/6 mice to B. rodhaini infection may be attributed in part to small stimulatory effect of KCP on splenic phagocytes.