Evidence for multiple hybrid groups in Trypanosoma cruzi

A role for parasite genetic variability in the spectrum of Chagas disease is emerging but not yet evident in part due to an incomplete understanding of the Population structure of Trypanosoma cruzi. To investigate further the observed genotypic variation at the sequence and chromosomal levels in strains of standard and field-isolated T cruzi we have undertaken a comparative analysis of 10 regions of the genome from two isolates representing T cruzi I (Dm28c and Silvio X10) and two from T cruzi 11 (CL Brener and Esmeraldo). Amplified regions contained intergenic (non-coding) sequences from tandemly repeated genes. Multiple nucleotide polymorphisms correlated with the T cruzi I/T cruzi II classification. Two intergenic regions had useful polymorphisms for the design of classification probe to test on genomic DNA from other known isolates. Two adjacent nucleotide polymorphisms in HSP 60 cot-related with the T cruzi I and T. cruzi 11 distinction. IFS nucleotide polymorphisms revealed multiple subdivisions of T cruzi 11: Subgroups IIa and IIc displayed the T cruzi I patterns subgroups IId and IIe possessed both the I and 11 patterns. Furthermore isolates from subgroups IId and IIe contained the 1F8 polymorphic markers on different chromosome bands supporting a genetic exchange cent that resulted in chromosomes V and IX of T cruzi strain CL Brener, Based on these analyses, T cruzi I and subgroup IIb appear to be pure lines while subgroups IIa/IIc and IId/IIe are hybrid lines. These data demonstrate for the first time that IIa/IIc are hybrid, consistent with the hypothesis that genetic recombination has occurred more than once within the T cruzi lines. (C) 2003 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.