Murine encephalitozoonosis model for studying the host-parasite relationship of a chronic infection.

Encephalitozoon cuniculi caused chronic nonlethal infections in euthymic BALB/cAnN mice, whereas athymic BALB/cAnN-nu mice died from infection. Specific, anamnestic, transferable, and acquired responses against E. cuniculi were expressed by infected euthymic mice. Resistance to lethal disease appears to be T-cell dependent. Immune serum failed to protect infected athymic mice, whereas the transfer of T-enriched spleen cells from E. cuniculi-sensitized euthymic donors prevented lethal E. cuniculi infections in athymic mice. These findings indicate that murine encephalitozoonosis may be an excellent system for studies of a chronic infection in an immunologically well-characterized host.