Análise de polimorfismos em antígenos do Trypanosoma cruzi aplicados ao diagnóstico sorológico em humanos

Abstract

Chagas disease (CD), caused by the protozoan parasite Trypanosoma cruzi, persists as a serious global public health problem, and its control is hindered by the absence of a "gold standard" diagnostic test. The vast genetic diversity of the parasite, which is classified into six main Discrete Typing Units (DTUs), is one of the factors that affects the accuracy of serological tests. Many diagnostic antigens have been identified in reference strains that have been grown for logn periods in the laboratory, ignoring the diversity of field isolates. The main objective of this study was to evaluate the conservation and variability of 28 epitopes of T. cruzi, previously described as promising for serodiagnosis, among field isolates of the parasite belonging to the six DTUs, TcI to TcVI, associated with human infections. To this end, an approach based on the analysis of raw sequencing data from 46 read libraries from field isolates, representing these six DTUs, was used. Analyses of conservation, genetic diversity, and population divergence revealed that, among the 28 reference epitopes, 24 variants were recovered in at least one library from each DTU. A more robust subset of 6 epitopes exhibited conservation in 100% of the analyzed read libraries, presenting a high frequency of their encoding reads (≥61.12%) and very low levels of genetic variation among the DTUs. Conversely, epitopes derived from multigene families showed marked polymorphism, characterized by high nucleotide diversity and differentiation among DTUs. Twenty of the 24 identified conserved epitopes were distinct variants from the original reference sequences, indicating that the most immunoreactive epitope described in one strain may not be the most prevalent in natural parasite populations. The study identified seven epitopes as the most promising according to conservation criteria. These results provide an essential basis for the improvement of CD diagnosis by pinpointing conserved antigenic targets in across all examined T. cruzi field isolates.