Comparison of chromosome and isoenzyme polymorphism in geographical populations of Leishmania (Viannia) peruviana

Five chromosomes and 17 isoenzyme loci were analysed in 4 allopatric populations of Leishmania (Viannia) peruviana, and molecular distances calculated with 2 estimators, Chromosomal Size Difference Index and Jaccard Distance. Chromosome and isoenzyme data were in overall concordance: 13/30 isolates clustered similarly on the dendrograms constructed from the different estimators, and a significant correlation (P < 0.001) was observed between the molecular distances calculated from the two sets of characters. This indicates an evolutionary association between chromosomal size polymorphism and isoenzymes. Chromosomes have a faster molecular clock than isoenzymes; twice as many genotypes were identified by chromosome analysis and significant size differences (for a total of up to 500 kb for 5 chromosomes together) were observed within a given zymodeme. Chromosomes most likely represent better indicators of genetic drift than isoenzymes, as suggested by the higher correlation between both estimators of chromosomal size-polymorphism and eco-geography. Some chromosomes might present an adaptive response to environmental variation.

The gp63 gene locus, a target for genetic characterization of Leishmania belonging to subgenus Viannia

In the present study the gp63 gene locus was used as a target for genetic characterization of Leishmania parasites by 2 methods: (i) RFLP analysis with several restriction enzymes (gp63-RFLP), and (ii) intra-genic PCR amplification coupled with restriction analysis (PCR-RFLP). Both methods were applied to a large number of natural isolates belonging to 4 species of the subgenus Viannia, namely L. (V.) braziliensis, L. (V.) peruviana, L. (V.) guyanensis and L. (V.) lainsoni; reference stocks of subgenus Leishmania were included as outgroups. Multilocus isoenzyme typing (MLEE) was used as a reference. On the one hand gp63-RFLP evidenced an extensive polymorphism and revealed specific markers for subgenus, species and geographical populations: congruence with MLEE was demonstrated statistically. The particular interest of gp63-RFLP was illustrated by infra-specific polymorphism, because of the possible relationship with phenotype diversity. On the other hand intra-genic amplification was less resolutive than gp63-RFLP, but also allowed discrimination of the 2 subgenera (PCR alone) and all the species tested in the subgenus Viannia (PCR-RFLP). PCR-RFLP presents an important operational advantage as it allows genetic characterization of minute amounts of parasites, using Leishmania specific primers. The polymorphism revealed by gp63-RFLP and PCR-RFLP illustrates the very high genomic and genetic plasticity of gp63 genes.

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.

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.

Population structure of Trypanosoma brucei S. L. in Cote d'Ivoire assayed by multilocus enzyme electrophoresis: epidemiological and taxonomical considerations

Fifty-two Trypanosoma brucei stocks isolated in Côte d'Ivoire from sympatric locations were analyzed by cellulose acetate electrophoresis of isoenzymes. Of 13 genetic loci surveyed, 5 appeared as variable, which made it possible to delimit 12 different zymodemes. The most abundant zymodeme involved stocks isolated from both humans and pigs, which is consistent with the hypothesis that pig is a reservoir of human African trypanosomiasis in Côte d'Ivoire, as already proposed by other authors. Population genetic analysis of the isozyme data indicated a strong linkage disequilibrium, which suggests that genetic recombination is severely restricted in this sample and favors the hypothesis that the trypanosome populations surveyed are basically clonal. Nevertheless, additional studies are required to better estimate the long-term stability of these clones and the possible interference of gene exchange at an evolutionary scale. The results corroborate the hypothesis that a majority of human T. brucei stocks from West Africa correspond to a fairly homogeneous cluster of genotypes (T. brucei gambiense 'Group I', Gibson, 1986).

From population to genome: ecogenetics of Leishmania (Viannia) braziliensis and L. (V.) peruviana

The size polymorphism of nine chromosomes, recognized by specific probes, was analysed in populations of Leishmania (Viannia) braziliensis and L. (V.) peruviana from various Peruvian biogeographical units. Interpretation of the polymorphism, by statistical and phenetic methods, led to the identification of five consensus (alpha- and beta-tubulin) and four variable chromosomes. The dynamics of the variable chromosomes were studied. The promoter role of the environment on their polymorphism was indicated by: (1) the discrimination of L. braziliensis (forest) and L. peruviana (Andes) by the size of the chromosome containing the gp63 genes; and (2) the fact that, within L. peruviana, the polymorphism of the variable chromosomes revealed a strong eco-geographical structuring of parasite populations, accompanied by increasing chromosomal dissimilarity along a cline from north to south. The adaptative significance of the polymorphism of the variable chromosomes was suggested by: (1) a correlation between chromosomal polymorphism and phenotype variability (lesion type in patients and virulence in vitro); and (2) the association between the decrease in size of the gp63-containing chromosome from L. braziliensis to L. peruviana, and a rearrangement of the gp63 genes, probably accompanied by a decrease in their copy number. As chromosomal variation was shown to be more dependant on eco-geographical differences than isoenzymatic variation, chromosome variation and enzyme variation probably differ in adaptative significance.

Putative Leishmania hybrids in the Eastern Andean valley of Huanuco, Peru

During an outbreak of tegumentary leishmaniasis that developed in the 1990s in the Eastern Andean valley of Huanuco, Peru, the coexistence of Andean (uta) and sylvatic leishmaniases was suspected for ecological and geographical reasons, and sympatric sampling was carried out. Seven human isolates of Leishmania were characterized by multilocus enzyme electrophoresis, random amplification of polymorphic DNA and molecular karyotyping. The three methods identified 3 isolates as L. braziliensis, and 4 isolates as putative hybrids with characters of L. braziliensis and L. peruviana. Data from Huanuco are compared to previous results from other areas endemic for uta. Biological and epidemiological implications are discussed.