Trypanosoma cruzi: isolate dependence in the induction of lytic antibodies in the mouse and rabbit.

Lytic antibodies able to interact with the live trypomastigotes of Trypanosoma cruzi have been associated with both protection and active infection. There are T. cruzi isolates unable to induce lytic antibodies despite their capacity in eliciting agglutinins and precipitins for immunofluorescent labeling. The host's spontaneous cure was ruled out as being responsible for negative results. The test performed either at 4 C or in the presence of sodium azide proved that negative lytic assays could not be attributed to capping phenomena. The classification of the parasites as T. cruzi was confirmed by their behavior in tissue culture and in the vector, as well as by the cross-protection exhibited by chronically infected mice against other lethal T. cruzi isolates. Cross-resistance achieved by these mice also suggests that the host's protection during chronic infection is independent of the lytic antibody titer.