/pdf/the-revised-trypanosoma-cruzi-subspecific-nomenclature-1agw21s1za.pdf

The revised Trypanosoma cruzi subspecific nomenclature: rationale, epidemiological relevance and research applications.

Identification of six Trypanosoma cruzi phylogenetic lineages by random amplified polymorphic DNA and multilocus enzyme electrophoresis.

Genetic variation in Trypanosoma cruzi is likely a key determinant in transmission and pathogenesis of Chagas disease. We have examined nine loci as markers for the extant T. cruzi strains. Four distinct alleles were found for each locus, corresponding to the sequence classes present in the homozygous discrete typing units (DTUs) I, IIa, IIb, and IIc. The alleles in DTUs IIa and IIc showed a spectrum of polymorphism ranging from DTU I-like to DTU IIb-like, in addition to DTU-specific sequence variation. DTUs IId and IIe were indistinguishable, showing DTU homozygosity at one locus and heterozygosity with DTU IIb and IIc allelic sequences at eight loci. Recombination between the DTU IIb and IIc alleles is evidenced from mosaic polymorphisms. These data imply that two discrete hybridization events resulted in the formation of the current DTUs. We propose a model in which a fusion between ancestral DTU I and IIb strains gave rise to a heterozygous hybrid that homogenized its genome to become the homozygous progenitor of DTUs IIa and IIc. The second hybridization between DTU IIb and IIc strains that generated DTUs IId and IIe resulted in extensive heterozygosity with subsequent recombination of parental genotypes.

https://www.genetics.org/content/genetics/171/2/527.full.pdf

Two hybridization events define the population structure of Trypanosoma cruzi.

Characterisation of large and small subunit rRNA and mini-exon genes further supports the distinction of six Trypanosoma cruzi lineages.

Summary Infections frequently contain multiple strains (genotypes) of the same pathogen, yet they are still usually treated as uniform entities. In this Review, we discuss problems with inconsistent definition of the term "strain" and review the prevalence and implications of multiple-strain infections. Up to now, multiple-strain infections have been shown unambiguously in 51 human pathogens (and 21 non-human ones) and are likely to arise in most pathogen species. In human pathogens, multiple-strain infections usually reach considerable frequencies (median 11·3%, mean 21·7% of infections), which are certainly underestimated in many cases because of technical limitations of detection. For many diseases, the importance of multiple-strain infections is still unclear, but theoretical work and experimental results from animal models suggest a broad range of clinically relevant effects. Multiple-strain infections can affect host immune responses and our ability to prevent and treat infection efficiently. Competition and mutualism between strains change pathogen and disease dynamics and promote pathogen evolution. Co-infection enables gene transfer among strains. Taking multiple-strain infections into account will improve our understanding of host-pathogen interactions and disease dynamics, and will provide a basis for novel control approaches.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(11)70241-9.pdf

Prevalence and implications of multiple-strain infections

Different behavior of two Trypanosoma cruzi major clones: transmission and circulation in young Bolivian patients.

A cross section of a human population (501 individuals) selected at random, and living in a Bolivian community, highly endemic for Chagas disease, was investigated combining together clinical, parasitological and molecular approaches. Conventional serology and polymerase chain reaction (PCR) indicated an active transmission of the infection, a high seroprevalence (43.3%) ranging from around 12% in 45 years, and a high sensitivity (83.8%) and specificity of PCR. Abnormal ECG tracing was predominant in chagasic patients and was already present among individuals younger than 13 years. SAPA (shed acute phase antigen) recombinant protein and the synthetic peptide R-13 were used as antigens in ELISA tests. The reactivity of SAPA was strongly associated to Trypanosoma cruzi infection and independent of the age of the patients but was not suitable neither for universal serodiagnosis nor for discrimination of specific phases of Chagas infection. Anti-R-13 response was observed in 27.5% only in chagasic patients. Moreover, anti-R13 reactivity was associated with early infection and not to cardiac pathology. This result questioned previous studies, which considered the anti-R-13 response as a marker of chronic Chagas heart disease. The major clonets 20 and 39 (belonging to Trypanosoma cruzi I and T. cruzi II respectively) which circulate in equal proportions in vectors of the studied area, were identified in patients' blood by PCR. Clonet 39 was selected over clonet 20 in the circulation whatever the age of the patient. The only factor related to strain detected in patients' blood, was the anti-R-13 reactivity: 37% of the patients infected by clonet 39 (94 cases) had anti-R13 antibodies contrasting with only 6% of the patients without clonet 39 (16 cases).

/pdf/integrate-study-of-a-bolivian-population-infected-by-jt6ctr1udb.pdf

Integrate study of a Bolivian population infected by Trypanosoma cruzi, the agent of Chagas disease

Previous studies showed that two groups of Trypanosoma cruzi clonal genotypes named clonet 20 and clonet 39 were predominant in Triatoma infestans, the unique vector of Chagas disease in Bolivia. These groups of clones correspond to distinct genetic clusters. These clonets were detected in T. infestans and Rhodnius pictipes fecal samples before isolation and after culture by kDNA PCR (polymerase chain rreaction) and hybridization of the amplified products with clonet specific kDNA probes named 20 and 39 as previously reported. Forty eight T. infestans and three R. pictipes infected insects captured at random in different Bolivian departments were proceeded. As previously reported the direct identification of the two major clonets in fecal samples allowed the detection of abundant mixed infections: 41% in the original sample, however after culture, only 6% of mixed infections were detected. Among the 21 parasite stocks isolated from digestive tracts where mixed infections were initially detected (clonet 20 + 39) clonet 20 alone was detected in 81% of them. This result clearly showed that the culture step selected clonet 20 parasites over those belonging to clonet 39. The taxonomic status of the isolated stocks was also confirmed by isoenzyme typing, and correlation was observed between clustering topology and hybridization patterns with the probes 20 and 39.

/pdf/selection-of-trypanosoma-cruzi-clonal-genotypes-clonet-20-13p2j92plj.pdf

Nina Yacsik

Papers

Different behavior of two Trypanosoma cruzi major clones: transmission and circulation in young Bolivian patients.

Integrate study of a Bolivian population infected by Trypanosoma cruzi, the agent of Chagas disease

Selection of Trypanosoma cruzi clonal genotypes (clonet 20 and 39) isolated from Bolivian triatomines following subculture in liquid medium

Pesquisa de anemia y su relación con el rendimiento escolar