Immunomodulatory effects of Triatoma dimidiata feces on Trypanosoma cruzi infection in a murine model.

Trypanosoma cruzi infection involves transmission of metacyclic trypomastigotes through injured skin or mucosa via contaminated feces from insect vectors like Triatoma dimidiata (Latreille, 1811). Currently, there is insufficient information describing the immune response to feces naturally contaminated with metacyclic trypomastigotes. Mice subcutaneously inoculated with tissue-culture derived trypomastigotes (TCT) or T. dimidiata feces containing metacyclic trypomastigotes (MT) or previously multi-exposed (ME) with feces without metacyclic trypomastigotes and then infected with feces containing metacyclic parasites or only T. dimidiata feces (F) was studied from 15 min to three months post-infection. PCR detection of parasite DNA at the inoculation site demonstrated persistence of T. cruzi DNA up to 20 days in MT and TCT but disappeared earlier in the ME test group. A rapid spread of T. cruzi DNA to regional lymph nodes was observed in all experimental groups. A lower amount of amastigote nests in the heart with concomitant intense inflammation was noticed in ME mice in comparison to the MT group. CD4 + T cell subtypes at popliteal lymph nodes shows early Th1 and Th17 responses at seven days in ME mice, whereas Th1, Th17 and Treg predominate in MT mice after three weeks, and feces induces Th1, Th17 and Treg at a later stage. Our study shows that previous exposure to feces prior to infection with T. cruzi helps control parasitism at the inoculation site and in heart tissue, and an early induction of Th1 and Th17 T cell subtypes.