Characterization and application of multiple genetic markers forPlasmodium malariae

Abstract

SUMMARYPlasmodium malariae, a protozoan parasite that causes malaria in humans, has a global distribution in tropical and subtropical regions and is commonly found in sympatry with other Plasmodium species of humans. Little is known about the genetics or population structure of P. malariae. In the present study, we describe polymorphic genetic markers for P. malariae and present the first molecular epidemiological data for this parasite. Six microsatellite or minisatellite markers were validated using 76 P. malariae samples from a diverse geographical range. The repeat unit length varied from 2 to17 bp, and up to 10 different alleles per locus were detected. Multiple genotypes of P. malariae were detected in 33 of 70 samples from humans with naturally acquired infection. Heterozygosity was calculated to be between 0·236 and 0·811. Allelic diversity was reduced for samples from South America and, at some loci, in samples from Thailand compared with those from Malawi. The number of unique multilocus genotypes defined using the 6 markers was significantly greater in Malawi than in Thailand, even when data from single genotype infections were used. There was a significant reduction in the multiplicity of infection in symptomatic infections compared with asymptomatic ones, suggesting that clinical episodes are usually caused by the expansion of a single genotype.

Comparative population structure of Plasmodium malariae and Plasmodium falciparum under different transmission settings in Malawi

“…Multi-locus genotyping was carried out at six P. malariae loci [17] and at 11 P. falciparum loci [27]. Microsatellite results were obtained from at least one locus in 93% of P. malariae infections detected using diagnostic PCR.…”

Genotypic diversity and spatial–temporal distribution of Symbiodinium clones in an abundant reef coral

“…2006). Asymptomatic infections may become symptomatic and potentially dangerous to the host following the second infection of a competing parasite genotype ( P. malariae ; Bruce et al. 2007; however see Vardo‐Zalik & Schall 2008).…”

Detecting number of clones, and their relative abundance, of a malaria parasite (Plasmodium mexicanum) infecting its vertebrate host

“…One class of markers for measuring Plasmodium clonal diversity are microsatellites, the sort tandem nucleotide repeats that are common in the parasite's genome. These markers have proven useful for studies in population genetics, virulence, infection dynamics, and the force of selection (Anderson et al 2000;Nair et al 2003;Bruce et al 2007;Vardo-Zalik andSchall 2008, 2009). However, two major technical challenges may obstruct interpretation of data on microsatellite markers for Plasmodium.…”

“…Microsatellites (regions of the genome with tandem short repeats of nucleotides) are particularly helpful because they are common in the Plasmodium genome, assumed selectively neutral, and alleles differing in number of repeats are readily scored using genetic analyzer instruments (Bruce et al 2007). The microsatellite region is amplified by polymerase chain reaction (PCR) in which a florescent dye is annealed to one primer, the product is run through a microcapillary gel system, and the instrument matches the size of the fragment(s) to a concurrently running set of size standards (Selkoe and Tooner 2006).…”