PROTECTIVE IMMUNE-RESPONSE OF ISOSPORA FELIS-INFECTED MICE AGAINST BABESIA-MICROTI INFECTION

Protective response against Babesia microti was studied in Isospora fe lis-infected mice. Isospora felis-infected mice which were exposed to B. microti on the 28th day post-infection showed absolute resistance a gainst Babesia microti. Interestingly, these mice showed no anti-B. mi croti antibodies. Mice that received spleen cells from I. felis-infect ed donors that were subsequently exposed to B. microti showed lower pe ak parasitemia (10.3% +/- 2.6) compared to those mice that received no rmal spleen cells (60.9% +/-15.0), and no spleen cells at all (47.3% /- 8.5). Treatment of I. felis-infected mice with monoclonal antibodie s against L3T4+ cells resulted to a depression of their resistance to B. microti, as clearly manifested by high levels of parasitemia. Findi ngs of the present study demonstrate the role of cell mediated immunit y, specifically by L3T4+ T-cells induced by I. felis infection, in pro viding mice protection against B. microti.