ITS–RFLP- and RAPD-based genetic variability of Trypanosoma cruzi I, human and vector strains in Santander (Colombia)

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

Background

The evolutionary history and ecological associations of Trypanosoma cruzi, the need to identify genetic markers that can distinguish parasite subpopulations, and understanding the parasite’s evolutionary and selective processes have been the subject of a significant number of publications since 1998, the year when the first DNA sequence analysis for the species was published.

Methods

The current analysis systematizes and re-analyzes this original research, focusing on critical methodological and analytical variables and results that have given rise to interpretations of putative patterns of genetic diversity and diversification of T. cruzi lineages, discrete typing units (DTUs), and populations, and their associations with hosts, vectors, and geographical distribution that have been interpreted as evidence for parasite subpopulation specificities.

Results

Few studies use hypothesis-driven or quantitative analysis for T. cruzi phylogeny (16/58 studies) or phylogeography (10/13). Among these, only one phylogenetic and five phylogeographic studies analyzed molecular markers directly from tissues (i.e. not from isolates). Analysis of T. cruzi DTU or lineage niche and its geographical projection demonstrate extensive sympatry among all clades across the continent and no significant niche differences among DTUs. DTU beta-diversity was high, indicating diverse host assemblages across regions, while host dissimilarity was principally due to host species turnover and to a much lesser degree to nestedness. DTU-host order specificities appear related to trophic or microenvironmental interactions.

Conclusions

More rigorous study designs and analyses will be required to discern evolutionary processes and the impact of landscape modification on population dynamics and risk for T. cruzi transmission to humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1918-2) contains supplementary material, which is available to authorized users.

In vitro antileishmanial, trypanocidal, and Mammalian cell activities of diverse n,n' -dihetaryl substituted diamines and related compounds

The leishmaniasis and Chagas diseases constitute a serious public health problem worldwide with few and ineffective treatment options. The search for new antiparasitic candidates at the initial steps of drug discovery and development is still necessary. The synthesis of 22 de novo synthetized N,N′-dihetaryl-alkyldiamine derivatives and in vitro antiparasitic activity were evaluated for the first time against intracellular and extracellular forms of Leishmania (Leishmania) infantum, L. (Viannia) panamensis, L. (Leishmania) amazonensis, and Trypanosoma cruzi. Additionally, the toxicity on mammalian cells was determined. Some of these substituted N,N′-diamines (25–35 % of the tested compounds) showed interesting results against free-living forms of parasites with activities at the inhibitory concentration (IC₅₀) level of 1.96 to 28.83 μM for L. (L.) infantum promastigotes and IC₅₀ of 0.02 to 5.31 μM for T. cruzi epimastigotes. No activity at the IC₅₀ level on intracellular amastigotes of T. cruzi was observed. However, N¹,N²-dibenzylethane-1,2-diamine 5a revealed an important activity against the intracellular amastigotes of L. infantum (IC₅₀ 25.42 μM ±0.33) and L. panamensis (IC₅₀ 58.20 μM ±3.23), while their analogue N¹,N⁴-dibenzylbutane-1,4-diamine 5c resulted in activity only against L. panamensis (IC₅₀ 11.19 μM ±0.20) without toxicity on Vero and THP-1 mammalian cells. The active compounds against intracellular parasites with low toxicity in mammalian cells may be considered for future studies in experimental models.

Multilocus PCR-RFLP profiling in Trypanosoma cruzi I highlights an intraspecific genetic variation pattern

Chagas disease represents a serious problem in public health. This zoonotic pathology is caused by the kinetoplastid Trypanosoma cruzi which displays a high genetic diversity falling into six Discrete Typing Units (TcI-TcVI). In Colombia, the prevalent DTU is TcI with findings of TcII, TcIII and TcIV in low proportions. The aim of this work was to observe the genetic variability within TcI using a multilocus PCR-RFLP strategy. We analyzed 70 single-celled clones from triatomines, reservoirs and humans that were amplified and restricted via ten PCR-RFLPs targets across TcI genome, the restriction fragments were used to construct phylograms according to calculated genetic distances. We obtained five polymorphic targets (1f8, HSP60, HSP70, SAPA and H1) and the consensus tree constructed according to these regions allowed us to observe two well-defined groups with close association to the transmission cycles (domestic/peridomestic and sylvatic) of Chagas disease in Colombia. Our findings allowed us to corroborate the previous reported genotypes based on the intergenic region of mini-exon gene. More studies examining the genetic diversity among T. cruzi I populations must be conducted in order to obtain a better understanding in regions where this DTU is endemic.

Molecular characterization of Trypanosoma cruzi and infection rate of the vector Triatoma dimidiata in Costa Rica

According to the genetic characterization by the analysis of the miniexon gene, strains of Trypanosoma cruzi can be classified into six discrete typing units (DTUs), and the DTU 1 into four distinct genotypes associated with different life cycles. While Chagas disease is endemic in Costa Rica, T. cruzi isolates from this region have never been genetically characterized. An analysis of 16 isolates from Costa Rica, based on miniexon gene analysis, showed the existence of two different haplotypes in the country, closely related to the Colombian haplotype group TcIa and to sequences from several Mexican isolates, with eight variable positions in the alignment and a variability of 2.6% between the compared sequences. No relationship between the habitat, vector or host, and the haplotypes was found, suggesting an active flow of T. cruzi in the country. The present study also reports a very high infection rate (47.3%, 26 out of 55 specimens) in a Costa Rican population of Triatoma dimidiata, the main vector of Chagas disease in this country. The distribution and abundance of the parasite and its main vector suggest a high risk of Chagas disease emergence in Costa Rica.