Influência do parasito e do hospedeiro no potencial patogênico de populações de Trypanosoma cruzi I na fase aguda da infecção experimental em camundongos

Abstract

The populations of Trypanosoma cruzi (Tc) show high biological and genetic variability and are classified into six groups TcI - TcVI. Currently, data concerning the pathogenicity of the TcI are conflicting and may be due to host genetic component and spread to humans in populations of T. cruzi restricted to a wild environment. However, the insertion of new vectors in the domestic environment enables contact T. cruzi wild with new hosts, increasing the genotypic variability by modifying their pathogenic potential. The study of biological behavior was conducted using groups of 15 Swiss, Balb/c and C57BL/6 male mice that were infected intraperitoneally with 1 x 104 trypomastigotes to evaluate the infectivity, virulence, blood and tissue parasitism, pathogenicity, tissue tropism and genetic variability of the LSSP-PCR (Low Stringency Single Specific Primer - PCR). We used four samples of T. cruzi isolates from triatomines in different Brazilian regions properly cryopreserved in culture and subsequently reactivated; isolates ALVANI, AQ1-7 and MUTUM classified as TcI and PV isolated as TcIV. In relation to the biological study, the TcI isolates showed parasitemia subpatent, and a variation in the infectivity and pathogenic potential followed by a low virulence in the acute phase by a 100% survival of animals. The isolates ALVANI and AQ1-7 were considered pathogenic, but with low infectivity, whereas, MUTUM and PV (TcIV) showed the high infectivity and low pathogenicity. The tissue tropism presenting by isolates of TcI was smooth and striated muscle, however, the isolated PV showed tropism for the heart. The results related to the genetic component demonstrated the existence of a large genetic variability among populations of blood and tissue, while the populations of the inoculum, and blood culture showed a significant intra-specific homogeneity related to the four isolates of T. cruzi, showing no differences between strains of mice. Most of the tissues analyzed inter-specific manner was grouped according to isolate analyzed showing the maintenance of characteristics within each population. TcI strains differences could be attributed to the polar populations associated with and without the capacity to produce lesions. These facts may explain the clinical controversies found in TcI human infections in different endemic regions.