Resistance to Babesia spp. and Plasmodium sp. in mice pretreated with an extract of Coxiella burnetii.

Mice injected intravenously with a commercially available extract of Coxiella burnetii prepared for use as the antigen in the complement fixation diagnostic test for Q fever were subsequently resistant to infection with Babesia microti, Babesia rodhaini, and Plasmodium vinckei petteri. The parasites appeared to die inside circulating erythrocytes. Protection was unaffected by exposing the pretreated mice to 900 rads on the day before they were infected. To explain these findings, it is postulated that pretreatment with Coxiella extract protects by potentiating the interferon-inducing capacity of the challenge dose of protozoa, which perhaps leads to enhanced of natural killer cells. Tumor necrosis factor also warrants investigation.