The complexity of the sylvatic cycle of Trypanosoma cruzi in Rio de Janeiro state (Brazil) revealed by the non-transcribed spacer of the mini-exon gene

Abstract

American trypanosamiasis occurs in nature as a sylvatic cycle, where Trypanosoma cruzi interacts with wild triatomines and mammalian reservoirs, such as marsupials, rodents, armadillos and other animals. Due to difficulties in trying to isolate T. cruzi stocks from the sylvatic cycle, very few studies have been performed in order to understand the parasite infection in natural environments. Traditionally T. cruzi has been considered to be composed of a highly heterogeneous population of parasites. In contrast, the mini-exon and the 24S alpha rRNA gene loci have shown that T. cruzi stocks can be clustered in 2 major phylogenetic groups: lineage 1 and lineage 2. In this report, 68 recently isolated T. cruzi samples from the sylvatic cycle belonging to different geographical areas in Rio de Janeiro, Brazil, have been typed based on a variable spot in the non-transcribed spacer of the mini-exon gene. Eight isolates were from triatomines, 26 stocks were from golden-lion tamarins, 31 from opossums, 2 from rodents and 1 from a three-toed sloth. Thirty (44%-30/68) isolates were typed as lineage 1, while 36 (53%-36/68) isolates were typed as lineage 2. Two opossums presented mixed infection. Therefore, 3% (2/68) of the isolates were typed as lineage 1 + lineage 2. Using these geographical regions as models of sylvatic environments, it was observed that 96% of the Didelphis marsupialis were infected by lineage 2 isolates, while all 26 golden-lion tamarins were infected by lineage 1. The results show preferential association of the 2 lineages of T. cruzi with different hosts, composing the complexity of the sylvatic cycle.

Genetic diversity of Colombian sylvatic Trypanosoma cruzi isolates revealed by the ribosomal DNA

“…Despite the aforementioned diversity, PCR amplification of sequences from the 24Sα ribosomal RNA gene and from the mini-exon gene non-transcribed spacer, demonstrated a dimorphism among T. cruzi isolates (Souto et al 1996, Fernandes et al 1998a that correlates with Z1 (T. cruzi I) and Z2 (T. cruzi II) (Fernandes et al 1998a(Fernandes et al , 1999. Further analysis of the mini-exon gene of Z3 isolates defined this group as a discrete cluster but related to T. cruzi I (Fernandes et al 1998b).…”

“…Oligonulceotides were used to amplify the region corresponding to the 5.8S rDNA plus the two flanking ITS as described elsewhere (Cupolillo et al 1995, Fernandes et al 1999. The PCR products were further submitted to RFLP analysis with six endonucleases (Rsa I, Hae III, Eco RI, Taq I, Bst UI and Sau 3AI).…”

Caracterización biológica y genética de dos clones pertenecientes a los grupos I y II de Trypanosoma cruzi de Colombia

“…En T. cruzi se han utilizado diferentes marcadores bioquímicos y moleculares para tratar de correlacionar la diversidad genética del parásito con sus características biológicas. El uso del espaciador intergénico de los genes mini-exón genera dos claras divisiones filogenéticas conocidas como T. cruzi I y T. cruzi II (12), las cuales permiten establecer algunas asociaciones importantes entre la taxonomía y la biología del parásito, el desarrollo de la enfermedad y diferentes parámetros epidemiológicos, entre otros (13,14).…”

“…Por otra parte, se ha visto que áreas con gran morbilidad presentan la circulación del grupo T. cruzi II, mientras que en donde circula el grupo T. cruzi I es poco frecuente la enfermedad (7). Sin embargo, estudios recientes muestran que los dos grupos están circulando en ambos ambientes (13)(14)(15)(16); en Venezuela, por ejemplo, un estudio realizado durante el año 2004 reveló un mayor número de pacientes infectados con el grupo T. cruzi I que presentaban la fase aguda de la enfermedad con manifestaciones clínicas similares a las observadas en pacientes infectados con el grupo T. cruzi II (16). Así mismo, en infecciones experimentales se ha encontrado que el grupo al que pertenecen los parásitos determina el tropismo a tejidos, la parasitemia y la patogénesis de la enfermedad (1,7,17).…”

Análisis por LSSP-PCR de la variabilidad genética de Trypanosoma cruzi en sangre y órganos de ratones.

“…Algunos autores han sugerido la circulación de los dos grupos de T. cruzi en iguales proporciones en la naturaleza y su asociación a diferentes hospederos, con un porcentaje muy bajo de infecciones mixtas (35). Sin embargo, nuestros resultados con el espaciador intergénico de los genes miniexón, aunque mostraron sólo el grupo T. cruzi I para las cepas, revelaron la presencia de los dos grupos en sangre.…”