Survival, immune responses and tissue cyst production in outbred (Swiss white) and inbred (CBA/Ca) strains of mice experimentally infected with Neospora caninum tachyzoites

The present work compared inbred (CBA/Ca) and outbred (Swiss white) strains of mice for their capacity to cope with a Neospora caninum infection and to consistently produce tissue cysts. In each experiment Swiss white and CBA/Ca mice were given three different doses of NC-1 tachyzoites. Lymphoproliferative and humoral responses as well as cytokine production were evaluated eight weeks after infection (PI) whereas tissue cyst production and histopathology were assessed 4, 6 and 10 weeks PI in immunosuppressed mice. Tissue cysts were observed 10 weeks after infection only in CBA/Ca mice receiving the two highest inoculum doses. Furthermore this strain showed the highest specific lymphoproliferative response. A mixed cytokine response with elevated IFN-γ and fairly low IL-4 and IL-10 secretion was recorded. In both strains, no lesions were observed in the tissues of infected mice. This study indicates that CBA/Ca female mice infected with 5 × 106 NC-1 tachyzoites represent a useful model for the study of specific maternal immune responses in pregnant animals. Neospora caninum / immune response / resistance / cyst / mice