Microsatellite loci-based distribution of Trypanosoma cruzi genotypes from Chilean chronic Chagas disease patients and Triatoma infestans is concordant with a specific host-parasite association hypothesis

Abstract

The objective of this study was to investigate if there is specific host-parasite association in Chilean populations of Trypanosoma cruzi. For this purpose, two groups of parasites were analyzed, one from chronic chagasic patients, and the other from Triatoma infestans triatomines in three regions of the country. The first group consisted of four types of samples: parasites from peripheral blood of non-cardiopathic T. cruzi infected patients (NB); parasites from their corresponding xenodiagnosis (NX); parasites from peripheral blood of T. cruzi infected cardiopathic patients (CB) and parasites from their xenodiagnostics (CX). The T. infestans sample in turn was from three regions: III, V and M (Metropolitan). The genetic differentiation by the Fisher exact method, the lineage distribution of the samples, the molecular phylogeny and the frequency of multiclonality were analysed. The results show that not only are the groups of T. cruzi clones from Chagas disease patients and vectors genetically differentiated, but also all the sub-groups (NB, NX, CB and CX) from the III, V and M regions. The analysis of lineage distribution was concordant with the above results, because significant differences among the percentages of TcI, TcIII and hybrids (TcV or TcVI) were observed. The phylogenetic reconstruction with these Chilean T. cruzi samples was coherent with the above results because the four chagasic samples clustered together in a node with high bootstrap support, whereas the three triatomine samples (III, V and M) were located apart from that node. The topology of the tree including published T. cruzi clones and isolates was concordant with the known topology, which confirmed that the results presented here are correct and are not biased by experimental error. Taken together the results presented here are concordant with a specific host-parasite association between some Chilean T. cruzi populations.

Geographical, landscape and host associations of Trypanosoma cruzi DTUs and lineages

“…Previous studies provide evidence that hosts do not circulate all parasite populations all the time, in addition to segregation of infra-populations in different tissues and blood [16, 25, 27]. These studies clearly demonstrate that in vitro or in vivo passage of parasite populations further selects for haplotypes, which bias interpretation of genetic diversity [61, 62].…”

“…An additional and more pressing problem for analyzing T.cruzi ’s genetic diversity, variation, or structuring from a landscape perspective is the fact that, in general, most data are generated from culture or laboratory animal selected populations (parasite isolates). These difficulties to analyze parasite populations in all hosts have created voids in knowledge of intra-host and metapopulation dynamics, in addition to limitations from study designs and sampling methods, including ex-host selection (in vitro or in vivo) documented previously [25–27]. …”

Between a bug and a hard place:Trypanosoma cruzigenetic diversity and the clinical outcomes of Chagas disease

“…In the first publication, using kDNA Southern blots, more than 75% of the results in both groups were described as ‘TcI + TcII + hybrid’ [197] , perhaps reflecting cross-reactivity between minicircle hybridization probes [200] . Subsequent papers presenting nuclear microsatellite genotyping from patients from the same clinical trial, with unspecified degrees of overlap, demonstrated a predominance of TcI (79% of 33 IND and 57% of 28 CCM in [198] ; 86% of 28 IND and 71% of 24 CCM in [199] ).…”