Diagnóstico molecular de infecção por Trypanosoma cruzi, determinação de Discrete Typing Unit e sua associação com o perfil imunológico em amostras de pacientes chagásicos agudos

Abstract

According to the World Health Organization, there are about 7 million people infected with Trypanosoma cruzi worldwide (WHO, 2014). Chagas disease has long been considered an endemic disease in rural areas and Latin countries. However, its spread to non-endemic areas mainly by blood transfusion, and organ transplantation has been observed. Moreover, the emergence of outbreaks, mainly due to oral infection is becoming a global concern. A major challenge with regards to thedisease is the identification of prognostic biomarkers of differential clinical outcome in chronically infected individuals, as well as the understanding as to how the immunological events in the acute phase can drive disease progression in chronic phase. T. cruzi is currently classified in six discrete type units DTUs (Tc I - VI) according to Zingales (2009). Many authors believe that the genetic diversity of the parasite can influence the course of infection, and that strains belonging to different DTU induce different responses in infected individuals, polarizing clinical forms. Our study aimed to (1) diagnose, by polymerase chain reaction, T. cruzi infection in acute patients, (2) determine parasite DTU using sequential tests PCR, based on 3 markers: the COII gene, the intergenic spacer miniéxon gene and gene rDNA 24S, and (3) analyze the immune profile of the acute patients, correlating the DTU to the immune and clinical profile presented by these individuals. In our analysis, it waspossible to identify three distinct DTU in samples from 13 of the 31 patients from Pará (TcI, TcIII and TcIV) using the methodology proposed by Avila (2009). Among these, two cases of co-infection TcIII and TcIV, not yet reported in the literature, were observed. Importantly, TcIII is rarely found infecting human, being our record the first to identify TcIII in humans in the state of Pará. The individuals who presented lowparasitemia showed higher frequencies of CD8+ T cells expressing activated granzyme A, IFN- and IL-17, suggesting that individuals with low parasitemia have a more effector response profile, favouring parasite control. There were no significant differences between the frequency of CD4+ and CD8+ T cells and production of IFN- and IL-17 from the T. cruzi -infected individuals belonging to the TcI, TcIII and TcIV.However, a higher frequency IL-10 expression by CD8+ T cells was observed inpatients infected with TcIII and TcIV. Thus, our data brings new contributions to the understanding of the acute phase of the disease and the influence of presence / levels of parasitemia and parasite genetic diversity in immunological events during the course of T. cruzi infection.