Use of Tc-rCRP as a target for lytic antibody titration after experimental Trypanosoma cruzi infection.

Experimental Chagas disease has been used as a model to identify several host/parasite interaction factors involved in immune responses to Trypanosoma cruzi infection. One of the factors inherent to this parasite is the complement regulatory protein (Tc-CRP), a major epitope that induces production of lytic antibodies during T. cruzi infections. Previous studies have evaluated the function of Tc-CRP as an antigenic marker via ELISAs, which demonstrated high sensitivity and specificity when compared to other methods. Therefore, this study aimed to assess and compare the levels of lytic antibodies induced by this protein following experimental infection using different T. cruzi strains. Our results demonstrated that infections induced by strains isolated from vectors resulted in subpatent parasitaemia and low reactivity, as assessed by Tc-rCRP ELISAs. On the other hand, mice inoculated with T. cruzi strains isolated from patients developed patent parasitaemia, and presented elevated lytic antibodies titres, as measured by Tc-rCRP ELISA. In addition, comparison between different mouse lineages demonstrated that Balb/c mice were more reactive than C57BL/6 mice in almost all types of infections, except those infected by the AQ-4 strain. Parasites from the Hel strain generated the greatest lytic antibody response in all evaluated models. Therefore, application of sensitive techniques for monitoring immune responses would enable us to establish growth curves for lytic antibodies during the course of the infection, and allow us to discriminate between T. cruzi strains that originate from different hosts.