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M Tibayrenc

Publications and source records attributed to M Tibayrenc.

At least 55 records · Page 3Linked to original sources
PubMed1999

Plasmodium falciparum: population genetic analysis by multilocus enzyme electrophoresis and other molecular markers.

Abderrazak, S. B., Oury, B, Lal, A. A., Bosseno, M.-F., Force-Barge, P., Dujardin, J.-P., Fandeur, T., Molez, J.-F., Kjellberg, F., Ayala, F. J., and Tibayrenc, M. 1999. Plasmodium falciparum: Population genetic analysis by multilocus enzyme electrophoresis and other molecular markers. Experimental Parasitology 92, 232-238. The population structure of Plasmodium falciparum, the agent of malignant malaria, is uncertain. We have analyzed multilocus enzyme electrophoresis (MLEE) polymorphisms at 7-12 gene loci in each of four populations (two populations in Burkina Faso, one in Sudan, one in Congo), plus one "cosmopolitan" sample consisting of parasite cultures from 15 distant localities in four different continents. We have also performed random amplified polymorphic DNA analysis (RAPD) and restriction fragment length polymorphism (RFLP) and characterized gene varia tion at four antigen genes in the Congo population. All genetic assays show abundant genetic variability in all populations analyzed. With the isoenzyme assays, strong linkage disequilibrium is apparent in at least two local populations, the Congo population and one population from Burkina Faso, as well as in the cosmopolitan sample, and less definitely in the other Burkina Faso population. However, no linkage disequilibrium is detected in the Congo population with the molecular assays. We failed to detect any nonrandom association between the different kinds of genetic markers; that is, MLEE with RAPD or RFLP, RAPD with RFLP, and so on. Although isoenzyme data show statistical departures from panmictic expectations, these results suggest that in the areas under survey, P. falciparum populations do not undergo predominant clonal evolution and show no clear-cut subdivisions, un like Trypanosoma cruzi, Leishmania sp., and other major parasitic species. We discuss the epidemiological and taxonomical significance of these results.

Animals↗
PubMed1999

Molecular epidemiology and evolutionary genetics of Leischmania parasites.

In order to illustrate the relevance of the concepts and methods of evolutionary genetics in the understanding of the epidemiology of pathogenic agents, we develop in this paper the case of the Leishmania, a genus of parasitic protozoa. An extensive study of various natural populations of Leishmania in different countries (Old and New World) was carried out by using Multilocus Enzyme Electrophoresis (MLEE) and Random Amplified Polymorphic DNA fingerprinting (RAPD) as genetic markers. The data have been interpreted in evolutionary genetic terms. The main benefit of this approach has been to better define the concept of species in the genus Leishmnania, on rigorous phylogenetic bases. As a matter of fact, a sound taxonomical background is a prerequisite for any epidemiological approach. Since the biological concept of species is difficult or impossible to apply for most pathogenic microorganisms, we recommend relying on criteria of both phylogenetic discreteness and of epidemiological/medical relevance to describe new species of Leishmania. Through this approach, for example, we have shown that the species status of L. ( V.) perzzl.ianza can be supported. On the contrary, we have been unable to clearly distinguish L. (V.) panamensis from L. (V.) guyanensis with genetic tools. Additionally, we have shown that the epidemiological inferences based on a limited set of genetic markers can be misleading. As a matter of fact, we have demonstrated that a collection of L. (L.) infantum stocks identified as zymodeme 'MON 1' by other authors present additional genetic heterogeneity and do not correspond to a distinct 'Discrete Typing Unit' DTU, and are actually polyphyletic. Lastly, in the samples that were conveniently designed, we have confirmed that Leishmania parasites have a basically clonal population structure. As the clonal model specifies it, occasional bouts of genetic exchange remain nevertheless possible. Telling comparisons are drawn with the evolutionary genetics of other pathogens Trypanosoma cruzi and Trypanosoma congolense.

Animals↗
PubMed1999

Evolutionary genetics of Trypanosoma and Leishmania.

We review recent advances in the study of population structure and phylogenetic diversity of parasites belonging to the genera Trypanosoma and Leishmania. In all species properly analyzed, these parasites exhibit a basically clonal population structure, with occasional bouts of genetic exchange or hybridization, and a strong structuration of their populations into discrete evolutionary lineages. On an evolutionary scale, the impact of sex appears to be greater in African than in American trypanosomes. The taxonomic status of some Leishmania 'species' is questionable.

Animals↗
PubMed1999

Toward an integrated genetic epidemiology of parasitic protozoa and other pathogens.

Due to the increase of human migrations, the appearance of emerging and reemerging endemies, growing antibiotic resistance, and climatic changes, infectious diseases most probably constitute the major challenge for medicine in the next century. The advent of molecular methods of pathogen characterization has considerably improved our knowledge of the epidemiology of these diseases. However, the use of concepts of evolutionary genetics for interpreting "molecular epidemiology" data remains limited, although the application of such methods would broaden considerably the scope of this field of research, and allow epidemiologic and taxonomic approaches to be ascertained on a much firmer basis. In turn, pathogens, hosts, and vectors provide fascinating models for basic research. The artificial character of the border between "basic" and "applied" research is especially apparent with regard to the "integrated genetic epidemiology of infectious diseases" concept. The goal of this chapter is to evaluate the respective impact, on the transmission and pathogenicity of infectious diseases, of the host's, the pathogen's, and the vector's (for vector-borne diseases) genetic diversity, and the interactions between these three parameters (coevolution phenomena).

Animals↗
PubMed1999

Clinical analysis and parasite genetic diversity in human immunodeficiency virus/Chagas' disease coinfections in Brazil.

To evaluate the possible role of parasitemia on Chagas' disease reactivation in Chagas' disease/human immunodeficiency virus (HIV) coinfection cases and the impact of HIV coinfection on Trypanosoma cruzi genetic diversity, 71 patients with Chagas' disease (34 HIV+ and 37 HIV-) were surveyed. Moreover, 92 T. cruzi stocks from 47 chronic chagasic patients (29 HIV+ and 18 HIV-) were isolated and analyzed by multilocus enzyme electrophoresis and a random amplified polymorphic DNA procedure. High parasitemia appeared to play a major role in cases of Chagas' disease reactivation. In HIV+ patients, the genetic diversity and population structure (clonality) of T. cruzi was similar to that previously observed in HIV- patients, which indicates that immunodepression does not modify drastically genotype repartition of the parasite. There was no apparent association between given T. cruzi genotypes and specific clinical forms of Chagas' disease/HIV associations.

Adult↗
PubMed1999

Genetic analysis of leishmania parasites in Ecuador: are Leishmania (Viannia) panamensis and Leishmania (V.) Guyanensis distinct taxa?

In the course of an epidemiologic survey in Ecuador, the following collection of Leishmania stocks was isolated: 28 from patients with clinical signs of leishmaniasis, 2 from sloths, 1 from a dog, and 4 from sand flies. For genetic characterization of these stocks, multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) were used. Twenty six of the 35 stocks were identified as either Leishmania (V.) panamensis or L. (V.) guyanensis, 2 stocks were identified as L. (V.) braziliensis, the 2 stocks from sloths showed specific genotypes, and 5 stocks were characterized as hybrids between L. (V.) braziliensis and L. (V.) guyanensis. These data show that genetic diversity of Leishmania in Ecuador is high and that L. (V.) panamensis/guyanensis is the dominant group in this country. The genetic analysis questioned the distinctness between the two species L.(V.) panamensis and L. (V.) guyanensis, since MLEE and RAPD data did not indicate that L. (V.) panamensis and L. (V.) guyanensis correspond to distinct monophyletic lines. Population genetic analysis performed on the L. (V.) panamensis/guyanensis group favors the hypothesis of a basically clonal population structure.

Animals↗
PubMed1999

A phylogenetic analysis by multilocus enzyme electrophoresis and multiprimer random amplified polymorphic DNA fingerprinting of the Leishmania genome project Friedlin reference strain.

We have assessed the phylogenetic status of the Leishmania genome project Friedlin reference strain by MLEE and multiprimer RAPD including a set of 9 stocks representative of the main Leishmania species and of the whole genetic diversity of the Leishmania genus. To our knowledge, the detailed genetic characterization of the Friedlin strain has never been published before. As previously recorded (Tibayrenc et al. 1993), MLEE and RAPD data gave congruent phylogenetic results. The Friedlin reference strain was definitely attributed to Leishmania (Leishmania) major Yakimoff et Schokhor, 1914. Five specific RAPD patterns made it possible to distinguish between the Friedlin strain and the 2 other L. (L.) major stocks included in the study. Various specific MLEE and RAPD characters permitted to distinguish between the Leishmania species included in the study. All these characters are usable to detect accidental laboratory mix-ups involving the Friedlin reference strain. In confirmation with previous studies involving a more limited set of genetic markers, the general genetic diversity of the Leishmania genus proved to be considerable. It must be made clear that only one strain cannot be considered as representative of the whole genetic variability of the genus Leishmania. In the future, it is therefore advisable to complement the results obtained in the framework of the Leishmania genome project with data from other strains that should be selected on a criterion of important genetic differences with the Friedlin strain.

Animals↗
PubMed1998

A phylogenetic analysis of the Trypanosoma cruzi genome project CL Brener reference strain by multilocus enzyme electrophoresis and multiprimer random amplified polymorphic DNA fingerprinting.

We have assessed the phylogenetic status of the Trypanosoma cruzi Genome Project CL Brener reference strain by multilocus enzyme electrophoresis (MLEE) and multiprimer random amplified polymorphic DNA (RAPD) including a set of cloned stocks representative of the whole genetic diversity of T. cruzi. MLEE and RAPD data gave congruent phylogenetic results. The CL Brener reference strain fell into the second major phylogenetic subdivision of T. cruzi, and was genetically very close to the Tulahuen reference strain. No reliable RAPD character and only one MLEE character permitted us to distinguish between the CL Brener and Tulahuen reference strains. In contrast, many RAPD and MLEE characters were able to distinguish between the CL Brener reference strain and the other T. cruzi genotypes analyzed here, in particular the formerly described principal zymodemes I, II and III. It is suspected that both CL Brener and Tulahuen are hybrid genotypes, a fact that should be taken into account when interpreting sequence data. Moreover, our study confirms that the species T. cruzi is genetically very heterogeneous. We recommend future comparison of sequencing data from the CL Brener reference strain with those of at least one radically distinct T. cruzi genotype, belonging to the other major phylogenetic subdivision of this species.

Animals↗
PubMed1998

Predicted and observed alleles of Plasmodium falciparum merozoite surface protein-1 (MSP-1), a potential malaria vaccine antigen.

The 19-kDa antigenic domain of Plasmodium falciparum merozoite surface protein (MSP)-1 is a potential malaria vaccine candidate. Based on the amino acid substitution, four known alleles, E-TSR (PNG-MAD20 type), E-KNG (Uganda-PA type), Q-KNG (Wellcome type), and Q-TSR (Indo type) of this domain have been identified. Using single or double crossover recombinational events, we predicted the existence of additional alleles of this antigen. The presence of the predicted alleles was determined in parasite isolates from western Kenya, by undertaking a cross-sectional and a longitudinal study. Of the ten predicted alleles, we have revealed the presence of three new alleles: E-KSG-L (Kenya-1 type); E-KSR-L (Kenya-2 type); and E-KNG-F (Kenya-3 type). The results of this study suggest that it may be possible to predict the complexity of the genetic makeup of natural parasite populations.

Alleles↗
PubMed1998

Trypanosoma cruzi: impact of clonal evolution of the parasite on its biological and medical properties.

Trypanosoma cruzi populations are subdivided into natural clones that can exhibit considerable genetic differences. It has been proposed that T. cruzi clonal structure has a major impact on this parasite's biological properties. The present work aims at testing this hypothesis. Twenty-one stocks isolated from various ecological cycles, places, and hosts were characterized by multilocus enzyme electrophoresis (MLEE) with 22 genetic loci and random amplification of polymorphic DNA (RAPD) with 10 primers on the one hand and by 14 different biological parameters on the other hand. These parameters were related to: (i) growth kinetics of epimastigotes and amastigotes; (ii) infection of culture cells by amastigotes; (iii) viability of extracellular trypomastigotes; or (iv) sensitivity of epimastigotes, trypomastigotes, and amastigotes to Benznidazole and Nifurtimox. MLEE and RAPD results exhibited parity to each other, as previously noted (M. Tibayrenc, K. Neubauer, C. Barnabé, F. Guerrini, D. Skarecky, and F. J. Ayala, 1993, Proceedings of the National Academy of Sciences of the USA 90, 1335-1339), and showed that the 21 stocks were distributed into three main genetic groups, 19/20, 32, and 39, corresponding to the major clones 19, 20, 32, and 39 previously described on the basis of 15 isozyme loci. Most biological parameters showed a strong correlation to the genetic distances evaluated from either MLEE or RAPD, which favors the working hypothesis. The only exception came from drug sensitivity estimated on trypomastigote forms. The overall results made it possible to firmly reject the null hypothesis that there is no relationships between evolutionary distances and biological differences in T. cruzi natural clones.

Animals↗
PubMed1998

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

Specificity of two widespread Trypanosoma cruzi clonal genotypes or "clonets" (20 and 39) was first analyzed by hybridization with a large set of T. cruzi stocks characterized by multigenic study relying on both MLEE and RAPD. Then, these clonets were detected in the blood of Chagasic children from a Bolivian endemic area by a combination of polymerase chain reaction and clonet-specific DNA hybridization. The distribution of these clonets in patients was significantly different from that observed in the vectors of the same area (Triatoma infestans). In vectors, clonets 20 and 39 are found with comparable frequencies (0.69 and 0.67, respectively) in contrast with patients, in whom clonet 20 and mixed infections exhibit low frequencies. The Chagasic population can be divided into acute infections and latent infections above the accepted criterion of parasitemia (direct microscopic examination). The results suggest a limited selection in the transmission of the two clonets and a further drastic control of clonet 20 parasitemia by the immune system of children patients.

Animals↗
PubMed1998

Trypanosoma cruzi: compared vectorial transmissibility of three major clonal genotypes by Triatoma infestans.

Twenty Trypanosoma cruzi stocks attributed to the 19/20, 32, and 39 major clones (Tibayrenc et al. 1986) were used to infect experimentally third instar larvae of Triatoma infestans. Three variables were considered: (i) percentage of infected insects; (ii) number of flagellates per insect (NFI); and (iii) percentage of metacyclic trypomastigotes per insect. Differences between the genotypes under study for all parameters considered were detected. These differences were statistically significant (P < 10(-3)), except between the 39 and 32 clonal genotypes for the NFI parameter. The correlation coefficient between the genetic distance and the biological parameters determined by the nonparametric Mantel's test was strongly significant (P < 10(-4)). Data obtained suggest clearly that populations of parasites belonging to the 19/20 genotype are more efficiently transmitted (high transmissibility genotype) by the vector than the 32 genotype (low transmissibility genotype), while the 39 genotype presents intermediary characteristic. Results confirm the working hypothesis that the subdivision of T. cruzi into discrete clonal lineages has an impact on the vectorial competence of T. infestans, the most important vector of the chagasic infection in South America, and that different clonal lineages do not exhibit the same vectorial transmissibility. This fact is relevant both for Chagas' disease epidemiology and for the use of xenodiagnosis.

Animals↗
PubMed1998

Compared vectorial transmissibility of pure and mixed clonal genotypes of Trypanosoma cruzi in Triatoma infestans.

A total of 15 mixtures involving 9 different stocks attributed to the 19/20, 32 and 39 major clonal genotypes of Trypanosoma cruzi were used to infect third-instar nymphs of Triatoma infestans via an artificial feeding device. Three biological parameters were considered: (1) the percentage of infected insects (%II), (2) the number of flagellates per insect (NFI), and (3) the percentage of trypomastigotes per insect (%DIF). Genetic characterization by both multilocus enzyme electrophoresis (MLEE) and random amplification of polymorphic DNA (RAPD) indicated that in almost all cases (87%), mixtures remained present after completion of the whole cycle in the insect vector. Two lines of comparison were performed: (1) pure clonal genotypes versus corresponding mixed clonal genotypes and (2) the actual behavior of mixed clonal genotypes versus the expected behavior of the theoretical mixture (i.e. the arithmetic mean of the results observed for each of the two clonal genotypes taken separately). Statistical analyses of the variables were made difficult because of the presence of large standard deviations. Nevertheless, in several cases, mixtures differed significantly from pure clonal genotypes, and in one case the actual mixture differed significantly from the theoretical mixture. In some cases, interaction (either potentialization or reciprocal inhibition) could be suspected.

Animals↗
PubMed1998

Genetic epidemiology of parasitic protozoa and other infectious agents: the need for an integrated approach.

This paper emphasises the relevance of the concepts and methods of evolutionary genetics for studying the epidemiology of parasitic protozoa and other pathogenic agents. Population genetics and phylogenetic analysis both contribute to identifying the relevant evolutionary and epidemiologically discrete units of research (Discrete typing units = DTUs), that can be equated to distinct phylogenetic lines. It is necessary (i) to establish that a given species represents a reliable DTU; (ii) to see whether a given species is further structured into lower DTUs that correspond to either clonal lineages or to cryptic species, and could exhibit distinct biomedical properties (virulence, resistance to drugs, etc). DTUs at the species and subspecies level can be conveniently identified by specific genetic markers or sets of genetic markers ("tags") for epidemiological follow-up. For any kind of pathogen (protozoa, fungi, bacteria, viruses), DTUs represent the relevant units of research, not only for epidemiology, but also, for other applied researches (clinical study, pathogenicity, vaccine and drug design, immunology, etc). The development of an "integrated genetic epidemiology of infectious diseases", that would explore the respective role of, and the interactions between, the genetic diversity (and its biological consequences) of the pathogen, the host and the vector (in the case of vector-borne diseases) is called for.

Animals↗