Differential effects of cyclophosphamide on Coxiella burnetii infection in mice.

Treatment of mice with a single dose (200 mg/kg body weight) of cyclophosphamide (CPA) 3 days before intraperitoneal (i. p.) administration of Coxiella burnetii did not substantially affect either the yield of C. burnetii from mouse spleen or the splenomegaly induced by the infection. Administration of the same CPA dose 2 days after i. p. infection resulted in an increased yield of C. burnetii from the spleen and in a reduction of the spleen size as compared to CPA-untreated and CPA-pretreated infected mice. The yields of C. burnetii from the blood and peritoneum were similarly affected. The reduction of splenomegaly was accompanied by a marked decrease in the number of spleen lymphocytes especially in white pulp. Agglutinating antibody response to C. burnetii antigens was inhibited regardless whether CPA was given before of after infection. Whereas delayed hypersensitivity reaction to phase I soluble C. burnetii antigen was not influenced significantly by CPA pretreatment, it was markedly inhibited in mice treated with CPA after C. burnetii administration. The results stress the importance of cell-mediated immunity in C. burnetii infection.