Mechanisms of resistance against experimental Trypanosoma cruzi infection: the importance of antibodies and antibody-forming capacity in the Biozzi high and low responder mice.

The role of antibodies and the host's antibody-forming capacity in resistance to Trypanosoma cruzi infection has been investigated in the Biozzi high and low responder lines of mice. Ab/L animals with low antibody-forming capacity were found to be more susceptible to i.p. infection with trypomastigotes than high responders (Ab/H), whereas non-selected Swiss albino mice showed an intermediate level of susceptibility. The correlation between antibody-forming potentiality and susceptibility was consistently observed with both the Y and Tulahuén strains of the parasite, which differ in their preferential tissue tropism as well as virulence. A similar divergence in susceptibility was observed after subcutaneous infection with the Y strain which produced a more fulminating disease. Although Ab/L mice neither produced a significant antibody response to the parasite nor responded to prophylactic immunization with killed T. cruzi epimastigotes, they could be effectively protected by passive transfer of immune plasma.