RESUMO
The merozoite surface protein-1 gene of Plasmodium vivax is highly polymorphic and so, currently used in epidemiological studies of P. vivax malaria. We sequenced the variable block 5 of the gene from 39 Venezuelan isolates, 18 of which were co-infected with Plasmodium falciparum. We observed a limited variability with 34 isolates belonging to the type Salvador I, none Belem type and only five recombinants. Among the recombinants, only two types of sequences were observed with, respectively, 18 and 21 poly-Q residues. Nucleotide substitutions explained the major differences of the 11 patterns observed. We could evidence neither specific MSP-1 genotype associated with co-infected samples, nor peculiar MSP-1 genotype distribution inside the investigated areas. In comparison with other low endemic regions in the world, our sampling has a lower genetic diversity, which could be mainly explained by the lack of Belem type. In fact, the variable repeats of poly-Q residues involved in the polymorphism of Belem type and recombinant isolates are responsible for a great part of variability observed in MSP-1 block 5.
Assuntos
Variação Genética , Malária Vivax/parasitologia , Proteína 1 de Superfície de Merozoito/genética , Plasmodium vivax/classificação , Adulto , Sequência de Aminoácidos , Animais , DNA de Protozoário/análise , Feminino , Ouro , Humanos , Masculino , Proteína 1 de Superfície de Merozoito/química , Mineração , Dados de Sequência Molecular , Plasmodium vivax/genética , Plasmodium vivax/isolamento & purificação , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , VenezuelaRESUMO
BACKGROUND: Plasmodium vivax, although causing a less serious disease than Plasmodium falciparum, is the most widespread of the four human malarial species. Further to the recent recrudescence of P. vivax cases in the Newly Independent States (NIS) of central Asia, a survey on the genetic diversity and dissemination in Azerbaijan was undertaken. Azerbaijan is at the crossroads of Asia and, as such, could see a rise in the number of cases, although an effective malaria control programme has been established in the country. METHODS: Thirty-six P. vivax isolates from Central Azerbaijan were characterized by analysing the genetic polymorphism of the circumsporozoite protein (CSP) and the merozoite surface protein 1 (MSP-1) genes, using PCR amplifications and amplicons sequencing. RESULTS: Analysis of CSP sequences showed that all the processed isolates belong to the VK 210 type, with variations in the alternation of alanine residue (A) or aspartic acid residue (D) in the repeat motif GDRA(A/D)GQPA along the sequence. As far as MSP-1 genotyping is concerned, it was found that the majority of isolates analysed belong to Belem and Sal I types. Five recombinant isolates were also identified. Combined analysis with the two genetic markers allowed the identification of 19 plasmodial sub-types. CONCLUSION: The results obtained in the present study indicate that there are several P. vivax clones circulating in Azerbaijan and, consequently, a careful malaria surveillance could be of paramount importance to identify, at early stage, the occurrence of possible P. vivax malaria outbreaks.
Assuntos
Variação Genética , Malária Vivax/parasitologia , Plasmodium vivax/genética , Adolescente , Adulto , Idoso , Sequência de Aminoácidos , Animais , Azerbaijão/epidemiologia , Sequência de Bases , Criança , DNA de Protozoário/sangue , DNA de Protozoário/química , Marcadores Genéticos , Genótipo , Humanos , Malária Vivax/epidemiologia , Proteína 1 de Superfície de Merozoito/química , Proteína 1 de Superfície de Merozoito/genética , Pessoa de Meia-Idade , Dados de Sequência Molecular , Filogenia , Plasmodium vivax/classificação , Reação em Cadeia da Polimerase , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Alinhamento de SequênciaRESUMO
We investigated the genetic diversity and the population structure of 32 Plasmodium falciparum blood sample isolates (25 from Dakar city and suburbs and seven from other localities in Senegal) with two different types of molecular markers, 19 microsatellite and four antigenic determinant loci. Under the same technical procedure, microsatellite loci showed a mean number of alleles greater than that of antigenic loci. Both markers revealed that 15.6% of blood samples were multi-infected. Mean expected heterozygosity calculated from microsatellites and antigens was similar, 0.74 and 0.70, respectively. Significant linkage disequilibrium was observed from microsatellite loci and antigenic determinant loci. This suggests a non-panmictic structure for this sample that could be explained by two non-exclusive hypotheses: (i) a particular mating system (i.e. clonality), and/or (ii) a population structure in P. falciparum (i.e. Wahlund effect). Urban samples could have been drawn from a heterogeneous set of foci with different level of parasitic transmission. Moreover, no relationship was found between multilocus genotypes and different parameters (i.e. age, sex and blood group of parasitized patients; number of trophozoites per microliter of blood). The results are discussed taking into account recently published studies on malaria population biology.