Recent increase of genetic diversity in Plasmodium vivax population in the Republic of Korea

<p>Abstract</p> <p>Background</p> <p>The reemergence of <it>Plasmodium vivax </it>in South Korea since 1993 represents a serious public health concern. Despite the importance in understanding genetic diversity for control strategies, however, studies remain inconclusive with the general premise that due to low rate of malaria transmission, there is generally low genetic diversity with very few strains involved. In this study, the genetic diversity and population structure of <it>P. vivax </it>in South Korea were explored by analysing microsatellite polymorphism.</p> <p>Methods</p> <p>Sequences for 13 microsatellite loci distributed across the twelve chromosomes of <it>P. vivax </it>were obtained from 58 South Korean isolates collected during two sampling periods, namely 1997-2000 and 2007. The sequences were used for the analysis of expected heterozygosity and multilocus genotype diversity. Population structure was evaluated using STRUCTURE version 2.3.2. Linkage disequilibrium was also analysed to investigate the extent of outbreeding in the <it>P. vivax </it>population.</p> <p>Results</p> <p>Mean expected heterozygosity significantly increased from 0.382 in 1997-2000 to 0.545 in 2007 (<it>P </it>< 0.05). The number of multilocus genotypes was 7 and 27; and genotype diversity was statistically significant (<it>P </it>< 0.01) at 0.661 and 0.995 in 1997-2000 and 2007, respectively. Analysis by STRUCTURE showed a more complex population structure in 2007 than in 1997-2000. Linkage disequilibrium between 13 microsatellites, although significant in both time points, was notably lower in 2007.</p> <p>Conclusions</p> <p>The present microsatellite analysis clearly showed recent increase of genetic diversity and recent relaxation of the strong population structure observed in 1997-2000. These results suggest that multiple genotypes not present previously recently migrated into South Korea, accompanied by substantial outbreeding between different genotypes.</p

Coexistence of GP195 Alleles of Plasmodium Falciparum in a Small Endemic Area

Dimorphic variations in the genotype of the precursor to Plasmodium falciparum major merozoite surface antigens or gp195, among wild isolates in a small malaria parasite population were examined using Southern blot hybridization techniques. Hybridization, with DNA fragment probes and oligonucleotide probes derived from variable blocks of known gp195 alleles against 18 wild isolates from Mae Sod district in Thailand, revealed the existence of seven gp195 alleles, two of which were newly identified in this study. In four out of 17 patients, two different alleles coexisted in the circulation. It was furthermore noted that the seven alleles did not occur at the same frequency, but rather several alleles predominated in the population of P. falciparum in this small malaria field

Effect of olmesartan on the levels of circulating endothelial progenitor cell after drug-eluting stent implantation in patients receiving statin therapy

AbstractBackgroundThe endothelial progenitor cell (EPC) plays an important role in repairing vascular injury. Statins and angiotensin II receptor blockers increase the level of circulating EPCs. However, it is unknown whether the angiotensin II receptor blocker olmesartan synergistically acts with statins to increase the levels of circulating EPCs. Moreover, the association between the levels of circulating EPCs and endothelial dysfunction after implantation of drug-eluting stents (DESs) has not been evaluated.MethodsNine patients with stable coronary artery disease underwent percutaneous coronary intervention (PCI) and received DES implantation. All patients received olmesartan in addition to statin therapy after PCI. The dose of olmesartan was based on the physician's discretion as per the patients’ blood pressure. The levels of circulating EPCs were analyzed at baseline, post-PCI, and 1, 2, 3, and 8 months after PCI. Coronary angiography and the acetylcholine provocation test were performed on all patients at 8 months.ResultsAlthough the angiotensin II level significantly changed, the levels of circulating EPCs did not change during 8 months of olmesartan treatment (3.1±0.6cells/ml, 2.5±0.8cells/ml, 2.0±0.6cells/ml, 2.9±0.9cells/ml, 3.0±0.4cells/ml, 3.4±0.8cells/ml, p=0.64). The patients were subsequently divided into two groups based on whether the level of circulating EPCs was less or greater than 4cells/ml at 8 months. There were no significant differences in the mean vessel diameter of each segment (proximal, proximal edge, distal edge, and distal) after the acetylcholine provocation test between the two groups.ConclusionsLow-to-moderate doses of olmesartan might not increase the level of circulating EPCs in patients receiving statin therapy. There might be no association between the levels of circulating EPCs and the degree of coronary vasospasm in the acetylcholine provocation test 8 months after DES implantation

Allelic Variation in the Circumsporozoite Protein of Plasmodium falciparum from Thai Field Isolates

Allelic variation in the Plasmodium falciparum circumsporozoite (CS) protein gene has been examined by sequencing the entire gene in 15 isolates from an endemic area of Thailand. The isolates contain a total of six new allelic forms of the tetrapeptide repeats and eight variants of the T cell epitope (TCE) region of the CS gene. All nucleotide substitutions in the TCE are nonsynonymous. There is no apparent association between the sequence patterns in the repeats and in the TCE. Comparison of the TCE with published sequences has shown that most variants of our isolates are not identical to those found in different geographic areas, suggesting geographic variation in genetic diversity of the CS protein. In a phylogenetic tree, the new Thai alleles did not cluster together, suggesting a considerable heterogeneity within some geographic areas. Furthermore, analyses of tetrapeptide repeats from a number of isolates and strains showed evidence of three genetic mechanisms for the generation of variation in the repeats of the CS gene: point mutation, duplication of one or more repeat units, and intragenic recombination

Genetic diversity and population structure of Plasmodium falciparum in the Philippines

<p>Abstract</p> <p>Background</p> <p>In the Philippines, malaria morbidity and mortality have decreased since the 1990s by effective malaria control. Several epidemiological surveys have been performed in the country, but the characteristics of the <it>Plasmodium falciparum </it>populations are not yet fully understood. In this study, the genetic structure of <it>P. falciparum </it>populations in the Philippines was examined.</p> <p>Methods</p> <p>Population genetic analyses based on polymorphisms of 10 microsatellite loci of the parasite were conducted on 92 isolates from three provinces (Kalinga, Palawan, and Davao del Norte) with different malaria endemicity.</p> <p>Results</p> <p>The levels of genetic diversity and the effective population sizes of <it>P. falciparum </it>in the Philippines were similar to those reported in the mainland of Southeast Asia or South America. In the low malaria transmission area (Kalinga), there was a low level of genetic diversity and a strong linkage disequilibrium (LD) when the single-clone haplotype (SCH) was used in the multilocus LD analysis, while in the high malaria transmission areas (Palawan and Davao del Norte), there was a high level of genetic diversity and a weak LD when SCH was used in the multilocus LD analysis. On the other hand, when the unique haplotypes were used in the multilocus LD analysis, no significant LD was observed in the Kalinga and the Palawan populations. The Kalinga and the Palawan populations were, therefore, estimated to have an epidemic population structure. The three populations were moderately differentiated from each other.</p> <p>Conclusion</p> <p>In each area, the level of genetic diversity correlates with the local malaria endemicity. These findings confirm that population genetic analyses using microsatellite loci are a useful tool for evaluating malaria endemicity.</p