Trypanosoma cruzi discrete typing units in Chagas disease patients with HIV co-infection

Abstract

Background. Natural populations of T. cruzi have\nbeen classified into six phylogenetic lineages or\ndiscrete typing units, T. cruzi I, IIa, IIb, IIc, IId, and\nIIe, believed to play a role in tissue tropism and\ndisease pathogenesis. The impact of HIV infection\nin the T. cruzi genetic diversity in coinfected patients\nis a scarcely explored field of parasitology.\nObjective. To characterize parasitic lineages in\nclinical samples from patients co-infected with T.\ncruzi and HIV\nMaterials and Methods. We analyzed blood\nand lesions samples from 25 patients residing\nin Argentina, namely 8 infants born to 7 HIV\n- T. cruzi co-infected mothers, 3 indeterminate\nadult chagasic patients with HIV co-infection\nand 7 presenting cerebral Chagas due to AIDS.\nMolecular diagnosis and monitoring of etiological\ntreatment was carried out by PCR targeted to\nkinetoplastid (kDNA) and/or satellite sequences.\nT. cruzi lineages were identified by means of PCR\ntargeted to the intergenic spacer of miniexon gene\nand 24s ribosomal ARN genes. To characterize the\ninfra-lineage diversity, restriction fragment length\npolymorphism (RFLP) of KDNA amplicons was\ncarried out.\nResults. Out of the 7 co-infected mothers, two\ntransmitted both HIV and T. cruzi to their siblings,\nfour transmitted only T. cruzi. The remaining case\nwas a pregnant woman with cerebral Chagas disease\nwho entered into a coma being treated with\nbenznidazole; she did not transmit congenital\nChagas disease nor HIV to her newborn.\nMost bloodstream populations belonged to T.\ncruzi IId, with unique minicircle signatures for\neach patient´s strain, but identical signatures between\nstrains from mothers and their congenitally\ninfected infants. Mixtures of lineages T. cruzi I\nand T. cruzi IId were also detected. Differential\ntissue tropism of T. cruzi IIb and T. cruzi I was\nfound in patients with cerebral chagas. Minicircle\nsignatures showed complex patterns suggestive of\npolyclonal populations.\nConclusions. The higher proportion of PCR\npositive samples suggests higher parasite loads\nthat in chagasic population without HIV. The\nhigher prevalence of T. cruzi IId in bloodstream\nis in agreement with previous findings in this\nregion. The association of rare lineages at sites\nof encephalytis suggests differential tropism.\nThe direct characterization of parasite lineages in clinical samples allowed identification of a higher\nprevalence of mixed infections, than previously\nassumed, from studies based on culture isolates.