ACUTE AND CHRONIC EXPERIMENTAL TRYPANOSOMA-CRUZI INFECTION IN THE RAT- RESPONSE TO SYSTEMIC TREATMENT WITH RECOMBINANT RAT INTERFERON-GAMMA

We examined the effects of recombinant rat inteferon-gamma (IFN-gamma) injections on the parasitologic, serologic, immunologic and histopath ologic features of acute and chronic experimental Try-panosoma cruzi ( T. cruzi) infections in ''I'' rats. Upon infection at weaning, two rat groups were allocated to receive a 20-day cycle of IFN-gamma injectio ns, 20,000 IU/rat each, which started at 1, and 7 days postinfection ( pi). Treatment with IFN-gamma, initiated at either 1 or 7 days pi, res ulted in comparatively lower peak parasitemias (P < 0.02) but in simil ar levels of anti-T. cruzi circulating antibodies and serum IFN-gamma activities. The latter appeared significantly increased during acute i nfection whereas biologically active tumor necrosis factor was virtual ly undetectable in serum from infected rats regardless of whether they had been given IFN-gamma or not. The prevalence of chronic focal myoc arditis in IFN-gamma-treated infected rats showed no differences with respect to the one recorded in control-infected counterparts. The inve rse CD4/CD8 ratio of spleen and lymph node T cells that usually accomp anies chronic infection was reversed by IFN-gamma. Mononuclear cells c arrying class II I-A and I-E molecules, that were found to have increa sed at both compartments, appeared also modified upon IFN-gamma, treat ment with an overincrease of I-A-positive cells, and a normalization o f I-E-bearing cells.