Trypanosoma cruzi strains: behavior after passage into authoctonous or foreign species of traitomine (biological and biochemical patterns)

New insights into Trypanosoma cruzi genetic diversity, and its influence on parasite biology and clinical outcomes

Chagas disease, caused by Trypanosoma cruzi, remains a serious public health problem worldwide. The parasite was subdivided into six distinct genetic groups, called "discrete typing units" (DTUs), from TcI to TcVI. Several studies have indicated that the heterogeneity of T. cruzi species directly affects the diversity of clinical manifestations of Chagas disease, control, diagnosis performance, and susceptibility to treatment. Thus, this review aims to describe how T. cruzi genetic diversity influences the biology of the parasite and/or clinical parameters in humans. Regarding the geographic dispersion of T. cruzi, evident differences were observed in the distribution of DTUs in distinct areas. For example, TcII is the main DTU detected in Brazilian patients from the central and southeastern regions, where there are also registers of TcVI as a secondary T. cruzi DTU. An important aspect observed in previous studies is that the genetic variability of T. cruzi can impact parasite infectivity, reproduction, and differentiation in the vectors. It has been proposed that T. cruzi DTU influences the host immune response and affects disease progression. Genetic aspects of the parasite play an important role in determining which host tissues will be infected, thus heavily influencing Chagas disease's pathogenesis. Several teams have investigated the correlation between T. cruzi DTU and the reactivation of Chagas disease. In agreement with these data, it is reasonable to suppose that the immunological condition of the patient, whether or not associated with the reactivation of the T. cruzi infection and the parasite strain, may have an important role in the pathogenesis of Chagas disease. In this context, understanding the genetics of T. cruzi and its biological and clinical implications will provide new knowledge that may contribute to additional strategies in the diagnosis and clinical outcome follow-up of patients with Chagas disease, in addition to the reactivation of immunocompromised patients infected with T. cruzi.

Trypanosoma cruzi: A review of biological and methodological factors in Mexican strains

Trypanosoma cruzi, responsible for Chagas disease, is a serious public health problem in Latin America with eight million people infected in the world. Clinical manifestations observed in humans due to T. cruzi infection are largely associated with the wide biological and genetic heterogeneity of the parasite. This review presents an overview of the parasitological aspects of various strains of T. cruzi isolated mainly in Mexico, as well as an analysis of the methodological processes used to determine their virulence that could be influencing their biological characterization. We emphasize the importance of using uniform protocols to study T. cruzi virulence, taking into account factors related to: strain (i.e. developmental stage, lineage, biological origin, genetic variability), animal model used (i.e. role of hormones, host immune response, age) and methodology (i.e. inoculum size, inoculation route, and laboratory conditions used during strain maintenance). These uniform protocols will then allow proposing elements for understanding clinical evolution and management of the disease, for providing adequate treatment, and for developing tools for future vaccines against Chagas disease.

What makes an effective Chagas disease vector? Factors underlying Trypanosoma cruzi-triatomine interactions

The Chagas disease is caused by the parasite Trypanosoma cruzi, which infect blood-feeding triatomine bugs to finally reach mammal hosts. Chagas disease is endemic in Latin America, and is ranked among the 13 neglected tropical diseases worldwide. Currently, an estimate of 7 million people is infected by T. cruzi, leading to about 22 000 deaths per year throughout the Americas. As occurs with other vectors, a major question towards control programs is what makes a susceptible bug. In this review, we focus on findings linked to insect gut structure and microbiota, immunity, genetics, blood sources, abiotic factors (with special reference to ambient temperature and altitude) to understand the interactions occurring between T. cruzi and triatomine bugs, under a co-evolutionary scenario. These factors lead to varying fitness benefits and costs for bugs, explaining why infection in the insect takes place and how it varies in time and space. Our analysis highlights that major factors are gut components and microbiota, blood sources and temperature. Although their close interaction has never been clarified, knowledge reviewed here may help to boost the success of triatomine control programs, reducing the use of insecticides.

Influence of Triatoma dimidiata in Modulating the Virulence of Trypanosoma cruzi Mexican Strains

The epidemiology of Chagas disease is complex. There are different vectors and reservoirs and different clinical manifestations. In order to assess whether the biological behavior of three strains isolated in southeastern Mexico (H4 isolated from human, Z17 isolated from Didelphis sp., and V isolated from T. dimidiata) could be modified during passage through the vector T. dimidiata, the parasitemia curve, the amount of amastigote nests, and mortality of BALB/c infected with blood trypomastigotes of T. cruzi were evaluated. Strains were maintained in continuous passage from mouse to mouse and in animals infected with metacyclic trypomastigotes. The parasitemia curves were significantly different (P < 0.05) between mice to mice and triatoma to mice groups in strains H4 and Z17, and was also observed fewer amastigote nests in cardiac tissue (P < 0.05 strain H4 with higher number versus all groups and Z17 between mice to mice and triatoma to mice) 45 days after inoculation. It is concluded that T. dimidiata influences in modulating the virulence of strains of T. cruzi in the region. Further studies of the intestinal tract of the insect in search for some protein molecules involved in regulating may clarify the virulence of the parasite.

Molecular characterization of Trypanosoma cruzi Mexican strains and their behavior in the mouse experimental model

INTRODUCTION: For a long time, the importance of Chagas disease in Mexico, where many regarded it as an exotic malady, was questioned. Considering the great genetic diversity among isolates of Trypanosoma cruzi, the importance of this biological characterization, and the paucity of information on the clinical and biological aspects of Chagas disease in Mexico, this study aimed to identify the molecular and biological characterization of Trypanosoma cruzi isolates from different endemic areas of this country, especially of the State of Jalisco. METHODS: Eight Mexican Trypanosoma cruzi strains were biologically and genetically characterized (PCR specific for Trypanosoma cruzi, multiplex-PCR, amplification of space no transcript of the genes of the mini-exon, amplification of polymorphic regions of the mini-exon, classification by amplification of intergenic regions of the spliced leader genes, RAPD - (random amplified polymorphic DNA). RESULTS: Two profiles of parasitaemia were observed, patent (peak parasitaemia of 4.6×10(6) to 10(7) parasites/mL) and subpatent. In addition, all isolates were able to infect 100% of the animals. The isolates mainly displayed tropism for striated (cardiac and skeletal) muscle. PCR amplification of the mini-exon gene classified the eight strains as TcI. The RAPD technique revealed intraspecies variation among isolates, distinguishing strains isolated from humans and triatomines and according to geographic origin. CONCLUSIONS: The Mexican T. cruzi strains are myotrophic and belong to group TcI.

Trypanosoma cruzi strains isolated from human, vector, and animal reservoir in the same endemic region in Mexico and typed as T. cruzi I, discrete typing unit 1 exhibit considerable biological diversity

In this study, three strains of Trypanosoma cruzi were isolated at the same time and in the same endemic region in Mexico from a human patient with chronic chagasic cardiomyopathy (RyC-H); vector (Triatoma barberi) (RyC-V); and rodent reservoir (Peromyscus peromyscus) (RyC-R). The three strains were characterized by multilocus enzyme electrophoresis, random amplified polymorphic DNA, and by pathological profiles in experimental animals (biodemes). Based on the analysis of genetic markers the three parasite strains were typed as belonging to T. cruzi I major group, discrete typing unit 1. The pathological profile of RyC-H and RyC-V strains indicated medium virulence and low mortality and, accordingly, the strains should be considered as belonging to biodeme Type III. On the other hand, the parasites from RyC-R strain induced more severe inflammatory processes and high mortality (> 40%) and were considered as belonging to biodeme Type II. The relationship between genotypes and biological characteristics in T. cruzi strains is still debated and not clearly understood. An expert committee recommended in 1999 that Biodeme Type III would correspond to T. cruzi I group, whereas Biodeme Type II, to T. cruzi II group. Our findings suggest that, at least for Mexican isolates, this correlation does not stand and that biological characteristics such as pathogenicity and virulence could be determined by factors different from those identified in the genotypic characterization.

Should Trypanosoma cruzi be called "cruzi" complex? a review of the parasite diversity and the potential of selecting population after in vitro culturing and mice infection

Morpho-biological diversity of Trypanosoma cruzi has been known since Chagas' first works in 1909. Several further studies confirmed the morphological differences among the parasite strains, which were isolated from different reservoirs and vectors, as well as from human beings. In the early sixties, antigenic differences were found in the parasite strains from various sources. These differences, coupled to the observation of regional variations of the disease, led to the proposal of the term cruzi complex to designate the taxon T. cruzi. Since then this protozoan has been typed in distinct biodemes, zymodemes and lineages which were consensually grouped into T. cruzi I, T. cruzi II and into non-grouped strains. T. cruzi genotypic characterization, initially carried out by schizodeme analysis and more recently by various other techniques, has shown a great diversity of the parasite strains. In fact, T. cruzi is formed by groups of heterogeneous sub-population, which present specific characteristics, including distinct histotropism. The interaction of the different infecting clones of the cruzi complex and the human host will determine the morbidity of the disease.