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M Tibayrenc

Publications and source records attributed to M Tibayrenc.

142 records · Page 8Linked to original sources
PubMed1983

[Taxonomic and medical status of isoenzyme strains of Trypanosoma cruzi. Considerations of the systematic and immunologic values of various isoenzymes].

The genetic distance calculations for 45 Bolivian stocks of Trypanosoma cruzi show the lack of continuum among them and allow to distinguish two main groups, which origin is perhaps a passed speciation. The presence of some heterogeneity within each group leads us to propose a temporary terminology: each isozymic variant is called "zymostrain" without prejudging its medical or taxonomic importance. The relationships between biochemical Taxonomy and medical data are discussed. The taxonomic value of the different isoenzymes is examined. The possible immunogenic properties of some of them (particularly Glutamate deshydrogenase) is discussed.

Alleles↗
PubMedDate not supplied

An isoenzyme study of naturally occurring clones of Trypanosoma cruzi isolated from both sides of the West Andes highland.

Seventy-two stocks of Trypanosoma cruzi isolated from both sides of the West Andes highland (Bolivia, Chile and Peru) were analysed by isoenzyme electrophoresis at 12 loci. The data, which were interpreted in terms of population and evolutionary genetics, corroborated the hypothesis of T. cruzi clonal population structure previously proposed, and indicated extensive genetic variability within the taxon T. cruzi. Fifteen different clones (or zymodemes) were identified, which could be grouped into 3 different clusters. Several clones from 2 of these clusters were isolated both in Chile and Bolivia, suggesting a significant circulation of invertebrate and/or vertebrate hosts of T. cruzi between these 2 countries. Low clonal variability in Peru suggested the occurrence of a 'founder effect' in this country. The potential usefulness of a cladistic approach in epidemiology is discussed.

Animals↗
PubMedDate not supplied

Trypanosoma cruzi isoenzyme variability in Ecuador: first observation of zymodeme III genotypes in chronic chagasic patients.

We have analysed by multilocus enzyme electrophoresis (MLEE) at 21 genetic loci 10 Trypanosoma cruzi stocks isolated from chronic chagasic patients and 3 stocks isolated from Triatoma dimidiata collected in human habitats from the coastal part of Ecuador (all stocks isolated in August-December 1998). Isoenzyme profiles were compared to those of 4 laboratory-cloned stocks representing the major phylogenetic subdivisions of T. cruzi. This parasite's genetic variability in Ecuador proved to be considerable, even in this limited sample, since all main isoenzyme genotypes were recorded. Four stocks from patients were identical at all loci to the reference stock MNcl2 ('major clonet #39'; T. cruzi II) isolated in Chile. The 3 stocks isolated from T. dimidiata were closely related to the formerly described zymodeme I (T. cruzi I). Finally, 3 stocks from chronic chagasic patients (one with an asymptomatic form, 2 with a cardiac-digestive form) were closely related to the formerly described zymodeme III (presently not classified in either T. cruzi I or T. cruzi II). This is the first observation of this category of T. cruzi genotypes in chronic chagasic patients. In the past it was recorded only in acute patients, wild mammals and wild triatomine bugs. The epidemiological implications of these results are discussed.

Adult↗
PubMedDate not supplied

Evidence for hybridization by multilocus enzyme electrophoresis and random amplified polymorphic DNA between Leishmania braziliensis and Leishmania panamensis/guyanensis in Ecuador.

The taxonomic attribution of four Leishmania stocks isolated from humans in Ecuador has been explored by both multilocus enzyme electrophoresis and random amplified polymorphic DNA. For three loci, MLEE results showed patterns suggesting a heterozygous state for a diploid organism, while the corresponding homozygous states are characteristic of the Leishmania panamensis/guyanensis complex and Leishmania braziliensis, respectively. Other enzyme loci showed characters attributable to either the L. panamensis/ guyanensis complex or L. braziliensis. RAPD profiles exhibited for several primers a combination of the Leishmania panamensis/ guyanensis complex and L. braziliensis characters. These data hence suggest that the four stocks are the result of hybridization between L. panamensis/guyanensis and L. braziliensis. MLEE data show that the results cannot be attributed to either mixture of stocks, or an F1 in the framework of a simple Mendelian inheritance.

Animals↗
PubMedDate not supplied

Is Leishmania (Viannia) peruviana a distinct species? A MLEE/RAPD evolutionary genetics answer.

A set of 38 Leishmania stocks from the Andean valleys of Peru was characterized by both Multilocus Enzyme Electrophoresis (MLEE) and Random Amplified Polymorphic DNA (RAPD). Data were analyzed in terms of taxonomy and evolutionary genetics. Synapomorphic MLEE and RAPD characters, clear-cut clustering, and strong agreement between the phylogenies inferred from either MLEE or RAPD supported the view that Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis correspond to two closely related, but distinct monophyletic lines (clades) and can therefore be considered as "discrete typing units" (DTUs). The question whether the L. (V.) peruxviana DTU deserves species status is dependent upon the desirability of it, in terms of epidemiological and medical relevance. A previous Orthogonal Field Alternating Gel Electrophoresis (OFAGE) analysis of the same L. (V.) peruviana isolates was published by Dujardin et al. (1995b). The data from the different markers (i.e. MLEE, RAPD and OFAGE) were compared by population genetics analysis. RAPD and OFAGE provided divergent results, since RAPD showed a strong linkage disequilibrium whereas OFAGE revealed no apparent departure from panmictic expectation. MLEE showed no linkage disequilibrium. Nevertheless, contrary to OFAGE, this is most probably explainable by the limited variability revealed by this marker in L. (V.) peruviana (statistical type II error). RAPD data were consistent with the hypothesis that the present L. (V.) peruviana sample displays a basically clonal population structure with limited or no genetic exchange. Disagreement between RAPD and OFAGE can be explained either by accumulation of chromosomal rearrangements due to amplification/deletion of repeated sequences, or by pseudo-recombinational events.

Animals↗
PubMedDate not supplied

Integrated genetic epidemiology of infectious diseases: the Chagas model.

Genetic typing of pathogenic agents and of vectors has known impressive developments in the last 10 years, thanks to the progresses of molecular biology, and to the contribution of the concepts of evolutionary genetics. Moreover, we know more and more on the genetic susceptibility of man to infectious diseases. I propose here to settle a new, synthetic field of research, which I call 'integrated genetic epidemiology of infectious diseases' (IGEID). I aim at evaluating, by an evolutionary genetic approach, the respective impact, on the transmission and pathogenicity of infectious diseases, of the host's, the pathogen's and the vector's genetic diversity, and their possible interactions (co-evolution phenomena). Chagas' disease constitutes a fine model to develop the IGEID methodology, by both field and experimental studies.

Animals↗
PubMedDate not supplied

Restriction fragment length polymorphism of 195 bp repeated satellite DNA of Trypanosoma cruzi supports the existence of two phylogenetic groups.

The restriction fragment length polymorphism of the 195 bp repeated DNA sequence of Trypanosoma cruzi was analyzed among 23 T. cruzi stocks giving a reliable picture of the whole phylogenetic variability of the species. The profiles observed with the enzymes Hinf I and Hae III were linked together and supported the existence of two groups. Group 1 shows a 195 bp repeated unit (Hinf I) and high molecular weight DNA (Hae III), while group 2 presents a ladder profile for each enzyme, which is a characteristic of tandemly repeated DNA. The two groups, respectively, clustered stocks pertaining to the two principal lineages evidenced by isoenzyme and RAPD markers. The congruence among these three independent genomic markers corroborates the existence of two real phylogenetic lineages in T. cruzi. The specific monomorphic profiles for each major phylogenetic lineage suggest the existence of ancient sexuality and cryptic biological speciation.

Animals↗