[Show abstract][Hide abstract] ABSTRACT: Cytoadhesion of Plasmodium falciparum-infected erythrocytes to endothelial cells in microvessels is a remarkable characteristic of severe malaria. The endothelial protein C receptor (EPCR), encoded by the endothelial protein C receptor gene (PROCR), has recently been identified as an endothelial receptor for specific P. falciparum erythrocyte membrane protein 1 (PfEMP1) subtypes containing domain cassettes (DCs) 8 and 13. The PROCR rs867186-G allele (serine-to-glycine substitution at position 219 of EPCR; 219Gly) has been shown to be associated with higher levels of plasma soluble EPCR (sEPCR). In this study, the association of PROCR rs867186 with severe malaria is examined in Thai population.
A total of 707 Thai patients with P. falciparum malaria (341 with severe malaria and 336 with mild malaria) were genotyped for rs867186. To assess the association of PROCR rs867186 with severe malaria, three models (dominant, recessive and allelic) were evaluated. The rates of non-synonymous and synonymous substitutions were estimated for the coding sequence of the PROCR gene.
The rs867186-GG genotype was significantly associated with protection from severe malaria (P-value = 0.026; odds ratio = 0.33; 95% confidence interval = 0.12-0.90). Evolutionary analysis provided no evidence of strong positive selection acting on the PROCR gene.
The rs867186-GG genotype showed significant association with protection from severe malaria. The present results suggest that PfEMP1-EPCR interaction, which can mediate cytoadhesion and/or reduce cytoprotective and anti-inflammatory effects, is crucial to the pathogenesis of severe malaria.
[Show abstract][Hide abstract] ABSTRACT: Sporozoites of Plasmodium falciparum are transmitted to human hosts by Anopheles mosquitoes. Thrombospondin-related adhesive protein (TRAP) is expressed in sporozoites and plays a crucial role in sporozoite gliding and invasion of human hepatocytes. A previous study showed that the TRAP gene has been subjected to balancing selection in the Gambian P. falciparum population. To further study the molecular evolution of the TRAP gene in Plasmodium falciparum, we investigated TRAP polymorphisms in P. falciparum isolates from Suan Phueng District in Ratchaburi Province, Thailand. The analysis of the entire TRAP coding sequences in 32 isolates identified a total of 39 single nucleotide polymorphisms (SNPs), which comprised 37 nonsynonymous and two synonymous SNPs. McDonald-Kreitman test showed that the ratio of the number of nonsynonymous to synonymous polymorphic sites within P. falciparum was significantly higher than that of the number of nonsynonymous to synonymous fixed sites between P. falciparum and P. reichenowi. Furthermore, the rate of nonsynonymous substitution was significantly higher than that of synonymous substitution within Thai P. falciparum. These results indicate that the TRAP gene has been subject to diversifying selection in the Thai P. falciparum population as well as the Gambian P. falciparum population. Comparison of our P. falciparum isolates with those from another region of Thailand (Tak province, Thailand) revealed that TRAP was highly differentiated between geographically close regions. This rapid diversification seems to reflect strong recent positive selection on TRAP. Our results suggest that the TRAP molecule is a major target of the human immune response to pre-erythrocytic stages of P. falciparum.
PLoS ONE 01/2014; 9(2):e90522. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cerebral malaria is a major, life-threatening complication of Plasmodium falciparum malaria, and has very high mortality rate. In murine malaria models, natural killer (NK) cell responses have been shown to play a crucial role in the pathogenesis of cerebral malaria. To investigate the role of NK cells in the developmental process of human cerebral malaria, we conducted a case-control study examining genotypes for killer immunoglobulin-like receptors (KIR) and their human leukocyte antigen (HLA) class I ligands in 477 malaria patients. We found that the combination of KIR2DL3 and its cognate HLA-C1 ligand was significantly associated with the development of cerebral malaria when compared with non-cerebral malaria (odds ratio 3.14, 95% confidence interval 1.52-6.48, P = 0.00079, corrected P = 0.02). In contrast, no other KIR-HLA pairs showed a significant association with cerebral malaria, suggesting that the NK cell repertoire shaped by the KIR2DL3-HLA-C1 interaction shows certain functional responses that facilitate development of cerebral malaria. Furthermore, the frequency of the KIR2DL3-HLA-C1 combination was found to be significantly lower in malaria high-endemic populations. These results suggest that natural selection has reduced the frequency of the KIR2DL3-HLA-C1 combination in malaria high-endemic populations because of the propensity of interaction between KIR2DL3 and C1 to favor development of cerebral malaria. Our findings provide one possible explanation for KIR-HLA co-evolution driven by a microbial pathogen, and its effect on the global distribution of malaria, KIR and HLA.
[Show abstract][Hide abstract] ABSTRACT: Cerebral malaria is one of the most severe manifestations of Plasmodium falciparum malaria. The sequestration of parasitized red blood cells (PRBCs) to brain microvascular endothelium has been shown to contribute to the pathophysiology of cerebral malaria. Recent studies reported increased levels of von Willebrand factor (VWF) and reduced activity of VWF-cleaving protease, ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), in patients with cerebral malaria.
Association of six single nucleotide polymorphisms (SNPs) of the ADAMTS13 gene with cerebral malaria was examined in 708 Thai patients with P. falciparum malaria.
Among six SNPs, the derived allele of a SNP located in intron 28, rs4962153-A, was significantly associated with protection against cerebral malaria when 115 cerebral malaria patients were compared with 367 mild malaria patients (Fisher's exact P-value = 0.0057; OR = 0.27; 95% CI = 0.096-0.76). Significant association was also detected between 115 cerebral malaria and 593 non-cerebral malaria (226 non-cerebral severe malaria and 367 mild malaria) patients (Fisher's exact P-value = 0.012; OR = 0.30; 95% CI = 0.11-0.83).
Excessive adhesion of PRBCs to the platelet-decorated ultra-large VWF (ULVWF) appears to enhance the sequestration of PRBCs to cerebral microvascular endothelium. The genetic association observed in the present study implies that the regulation of platelet-decorated ULVWF strings by ADAMTS13 may play a role in the development of cerebral malaria.
[Show abstract][Hide abstract] ABSTRACT: The objective of this study is to determine and compare the heavy metal (Zn, Cu, Cd, Pb) and bacterial (E. coli, coliform and Salmonella spp.) contamination between swine farms utilizing biogas and non-biogas systems in the central part of Thailand. Results showed that average levels of E. coli, coliform, BOD, COD, Zn, Cu and Pb in sludge from the post-biogas pond were higher than the standard limits. Moreover, the levels of E. coli, coliform, Cd and Pb were also higher than the standard limits for dry manure. The levels of E. coli, coliform and BOD on biogas farms were lower than on non-biogas farms. Following isolation of Salmonella spp., it was found that Salmonella serovars Rissen was the most abundant at 18.46% (12/65), followed by Anatum 12.31% (8/65), and Kedougou 9.23% (6/65). The pathogenic strains of Salmonella serovars Paratyphi B var. java and Typhimurium were present in equal amounts at 4.62% (3/65) in samples from all swine farms. This study revealed that significant reduction in E. coli and coliform levels in sludge from covered lagoon biogas systems on swine farms. The presence of Salmonella as well as Cd and Pb, in significant amount in dry manure, suggests that there is a high probability of environmental contamination if it is used for agricultural purposes. Thus, careful waste and manure disposal from swine farms and the regular monitoring of wastewater is strongly recommended to ensure the safety of humans, other animals and the environment.
Journal of Environmental Sciences 01/2011; 23(6):991-7. · 1.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Interleukin-12 (IL-12), a heterodimeric cytokine composed of p35 and p40 subunits, has been thought to play an important role in the pathogenesis of malaria. The IL-12p40 subunit is encoded by the IL12B gene. An IL12B promoter allele, CTCTAA, at rs17860508 has been reported to be associated with susceptibility to cerebral malaria in African populations. However, this association has not so far been replicated in non-African populations.
To examine whether the CTCTAA allele is associated with susceptibility to cerebral malaria in Asian populations, 303 Thai patients with Plasmodium falciparum malaria (109 cerebral malaria and 194 mild malaria patients) were genotyped for rs17860508 by PCR-direct sequencing.
The CTCTAA allele showed a significant association with susceptibility to cerebral malaria in the Thai population (allelic OR = 1.37; one sided P-value = 0.030).
The existence of a significant association between the CTCTAA allele and susceptibility to cerebral malaria was confirmed in Southeast Asian population, which was previously reported in African populations.
[Show abstract][Hide abstract] ABSTRACT: Interferon-gamma (IFN-gamma) has been suggested to play an important role in the pathogenesis of malaria. To examine possible association of the IFN-gamma receptor 1 (IFNGR1) polymorphisms with cerebral malaria, 312 adult patients with Plasmodium falciparum malaria (203 mild and 109 cerebral malaria patients) living in northwest Thailand were genotyped for six single nucleotide polymorphisms (SNPs) including -56T/C (rs2234711) and a microsatellite marker in IFNGR1. A case-control association analysis failed to detect significant association between the IFNGR1 polymorphisms and cerebral malaria, thus implying that the IFNGR1 polymorphism may not be a major genetic factor influencing the development of cerebral malaria in the Thai population. These data also provide useful information for future genetic studies of IFNG polymorphisms in Thai patients.
Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 09/2009; 9(6):1406-9. · 3.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It has been previously demonstrated that a single nucleotide polymorphism (SNP) in the IL13 promoter region, IL13 -1055T>C (rs1800925), was associated with susceptibility to severe malaria in Thais. In the present study, fine association mapping for a cytokine gene cluster including IL4, IL5, and IL13 on chromosome 5q31 was conducted using the same malaria subjects to refine the region containing a primary variant or a haplotype susceptible to severe malaria.
A total of 82 SNPs spanning 522 kb of the 5q31 region were analysed in 368 patients with Plasmodium falciparum malaria (203 mild malaria and 165 severe malaria patients).
Only rs1881457 located in the promoter region of IL13, which is in linkage disequilibrium with rs1800925 (r2 = 0.73), showed a significant association with severe malaria after adjusting for multiple testing (P = 0.046 by permutation test). This SNP was in a haplotype block spanning 97 kb (from rs2069812 to rs2240032). The detected haplotype block contained the RAD50 gene and the promoter of IL13, but not the other genes.
A haplotype block in which a primary polymorphism associated with severe malaria is likely to be encoded was identified in Thai malaria patients.
[Show abstract][Hide abstract] ABSTRACT: Although the level of erythrocyte complement receptor type 1 (E-CR1) expression in patients with malaria has been extensively studied, whether the level of expression of E-CR1 is associated with severe malaria remains controversial. The present study examined a possible association of polymorphisms in the CR1 gene with the severity of malaria, and it evaluated the influence of the associated polymorphism on expression of E-CR1.
Seventeen single-nucleotide polymorphisms in CR1 were genotyped in 477 Thai patients who had Plasmodium falciparum malaria (203 had mild malaria, 165 had noncerebral severe malaria, and 109 had cerebral malaria). The E-CR1 expression level was measured by flow cytometry in 24 healthy Thai subjects.
The T allele of the reference single-nucleotide polymorphism rs9429942 in the CR1 promoter region was strongly associated with protection against cerebral malaria (2.2% of patients with mild malaria vs. 7.8% of patients with cerebral malaria; P = .0009; Bonferroni-adjusted Pc = .0306. The E-CR1 expression level was significantly higher in individuals with the TT genotype of rs9429942 than in individuals with the TC genotype of rs9429942 (P = .0282).
We identified a CR1 promoter allele, associated with higher E-CR1 expression, that conferred protection against cerebral malaria. Previous studies have shown that the rate of clearance of immune complexes (ICs) from the circulation is related to the E-CR1 level. These results lead to the hypothesis that the clearance of ICs regulated by E-CR1 therefore plays a crucial role in the pathogenesis of cerebral malaria.
The Journal of Infectious Diseases 11/2008; 198(12):1880-91. · 5.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hemoglobin E (HbE; beta26Glu --> Lys) is the most common variant of the beta-globin gene in Southeast Asia; it has been suggested that it confers resistance against Plasmodium falciparum malaria. In this study 306 adult patients with P. falciparum malaria (198 mild and 108 cerebral malaria patients) living in northwest Thailand were investigated to examine whether the HbE variant is associated with protection from cerebral malaria. Our results revealed that the sample allele frequency of HbE was not significantly different between mild (7.3%) and cerebral malaria (7.4%) patients. Thus, the HbA/HbE polymorphism would not be a major genetic factor influencing the onset of cerebral malaria in Thailand.
[Show abstract][Hide abstract] ABSTRACT: Although cerebral malaria is a major life-threatening complication of Plasmodium falciparum infection, its pathophysiology is not well understood. Prolonged activation of the T helper type 1 (Th1) response characterized by the production of pro-inflammatory cytokines such as IFN-gamma and TNF-alpha has been suggested to be responsible for immunopathological process leading to cerebral malaria unless they are downregulated by the anti-inflamatory cytokines produced by the Th2 response. The T cell immunoglobulin and mucin domain (TIM) family of proteins are cell surface proteins involved in regulating Th1 and Th2 immune responses. In this study, the possible association between the polymorphisms of TIM1, TIM3, and TIMD4 genes and the severity of malaria was examined in 478 adult Thai patients infected with P. falciparum malaria. The TIM1 promoter haplotype comprising three derived alleles, -1637A (rs7702919), -1549C (rs41297577) and -1454A (rs41297579), which were in complete linkage disequilibrium, was significantly associated with protection against cerebral malaria (OR = 0.41; 95% CI = 0.24-0.71; P= 0.0009). Allele-specific transcription quantification analysis revealed that the level of mRNA transcribed from TIM1 was higher for the protective promoter haplotype than for the other promoter haplotype (P= 0.004). Engagement with TIM1 in combination with T cell receptor stimulation induces anti-inflammatory Th2 cytokine production, which can protect the development of cerebral malaria caused by overproduction of pro-inflammatory Th1 cytokines. The present results suggest that the higher TIM1 expression associated with the protective TIM1 promoter haplotype confers protection against cerebral malaria.
Annals of Human Genetics 06/2008; 72(Pt 3):327-36. · 2.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ATP binding cassette transporter A1 (ABCA1) plays a role in the initial stage of removing cholesterol from the body via cholesterol efflux. Mutations of this gene cause wide-ranging HDL deficiency, as evident in Tangier disease and familial hypoalphalipoproteinemia. The aim of this study was to elucidate whether the presence of ABCA1 gene polymorphism could be a risk factor for overweight/obesity.
The presence of R219K and I883M genetic variant was determined by PCR-RFLP analysis in 112 overweight/obese and 117 control subjects of both sexes. Statistical analysis was performed to find an association between polymorphism and lipid data.
Overweight/obese men carrying the mutant allele of R219K had lower level of HDL than the control (p = 0.006). However, no positive association was observed using bivariate logistic regression analysis. On the contrary, there was no difference in HDL level among genotypes in I883M polymorphism. Both polymorphisms appeared to be common in Thai ethnic groups. No difference was detected in genotype frequency between the two populations for both polymorphisms.
Although the lower level of HDL in overweight/obese men carrying R219K in comparison to the control suggests the possible involvement of this gene with obesity, further investigations are needed to prove the influence of ABCA1 gene polymorphism on HDL level and to determine whether it could be a genetic determinant of obesity.
Archives of Medical Research 12/2007; 38(8):834-8. · 2.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined a possible association of three single nucleotide polymorphisms (SNPs) of the tumor necrosis factor alpha (TNF) promoter -1031T>C (rs1799964), -863C>A (rs1800630), and -857C>T (rs1799724) with severe malaria in 466 adult patients having Plasmodium falciparum malaria in northwest Thailand. Four TNF promoter alleles comprising these three SNPs were detected in the studied population. The frequency of the TNF U04 allele designated -1031C, -863C, and -857C was found to be significantly greater in patients with cerebral malaria than in patients with mild malaria (12.6%, cerebral malaria vs 5.6%, mild malaria; odds ratio =2.5; P=0.002). The association of U04 with susceptibility to cerebral malaria was not caused by linkage disequilibrium with any specific HLA-B and -DRB1 alleles.
[Show abstract][Hide abstract] ABSTRACT: Plasmodium falciparum invades erythrocytes via several routes using different red blood cell receptors that include glycophorin A (GYPA) and glycophorin B (GYPB). GYPA has two codominant alleles, i.e., M and N, that correspond to the M and N antigens, which differ by two amino acids (S1L, G5E); the codominant alleles of GYPB, i.e., S and s, correspond to the S and s antigens, which differ by a single amino acid (T29M). If these antigens influence the efficiency of erythrocyte invasion by malaria parasites, the MNSs phenotype may be associated with the severity of malaria. To examine this, the GYPA and GYPB genotypes carrying the MNSs antigens were analyzed in 109 and 203 Thai patients with cerebral malaria and mild malaria, respectively. Neither the genotype nor allele frequencies at each locus were statistically different between the cerebral and mild malaria patients. Thus, we conclude that the MNSs antigens do not reveal the difference in susceptibility to cerebral malaria.
Journal of Human Genetics 02/2007; 52(5):476-9. · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The pathogenesis of cerebral malaria from Plasmodium falciparum infection is thought to involve inflammation of the central nervous system. Since monocyte chemoattractant protein 1 (MCP-1) is a chemokine strongly involved in the inflammatory process, we here study MCP-1 gene polymorphisms in association with severe or cerebral malaria in Thailand. Malaria patients in the northwest of Thailand were grouped into mild (n=206), severe (165), and cerebral (110) malaria case groups. Five single nucleotide polymorphisms (SNPs) in the promoter (-2518A/G, -2348G/C, -2158C/T, -2076A/T, and -2072T/C), and 1 SNP in intron 1 (764C/G) were analyzed by PCR-RFLP, PCR-SSP, or direct sequencing. The SNP -2158 was a novel polymorphism found in this study. For all SNPs, genotype and allele frequencies were not significantly different between mild and severe or mild and cerebral malaria. Strong linkage disequilibrium was found among 4 SNPs (-2518A/G, -2348G/C, -2076A/T, and 764C/G), resulting in 4 major estimated haplotypes. The most common haplotype was GGAC. The results indicated that MCP-1 gene polymorphisms were not associated with malaria severity, implying that MCP-1 was not a cause of malaria severity in this Thai population.
Japanese journal of infectious diseases 09/2006; 59(4):239-44. · 1.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The high degree of polymorphism of human leukocyte antigen (HLA) genes has been suggested to result from natural selection against susceptibility to a variety of infectious pathogens, including malaria. HLA molecules are considered to play a crucial role in the defense of the host against malarial infection, and different HLA class I and class II alleles have been reported to be associated with reduced susceptibility to malaria or the severity of malaria in different populations. To test for associations between HLA alleles and the severity of malaria in a Thai population, polymorphisms of HLA-B and HLA-DRB1 genes were investigated in 472 adult patients in northwest Thailand with Plasmodium falciparum malaria. In this study, malaria patients were classified into three groups: mild malaria, non-cerebral severe malaria, and cerebral malaria. Our results revealed that the allele frequencies of HLA-B46, -B56, and -DRB1*1001 were statistically different between non-cerebral severe malaria and cerebral malaria (P = 0.005), between mild malaria and cerebral malaria (P = 0.032), and between mild malaria and non-cerebral malaria (P = 0.007). However, our results may be showing false positives due to multiple testing. Thus, further study with a larger sample size must be conducted to obtain conclusive evidence of the association of these HLA-B and DRB1 alleles with the severity of malaria in Thailand.
Japanese journal of infectious diseases 03/2005; 58(1):25-8. · 1.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: IL-1beta and IL-1RA levels are higher in the serum of cerebral malaria patients than in patients with mild malaria. Recently, the level of IL1B expression was reported to be influenced by a polymorphism in the promoter of IL1, IL1B -31C>T.
To examine whether polymorphisms in IL1B and IL1RA influence the susceptibility to cerebral malaria, IL1B -31C>T, IL1B 3953C>T, and IL1RA variable number of tandem repeat (VNTR) were analysed in 312 Thai patients with malaria (109 cerebral malaria and 203 mild malaria patients).
In this population, IL1B -31C>T and IL1RA VNTR were detected, while IL1B 3953C>T (i.e., IL1B 3953T) was not observed in the polymorphism screening for 32 patients. Further analyses for IL1B -31C>T and IL1RA VNTR in 110 cerebral malaria and 206 mild malaria patients showed no significant association of these polymorphisms with cerebral malaria.
The present results suggest that IL1B -31C>T and IL1RA VNTR polymorphisms do not play a crucial role in susceptibility or resistance to cerebral malaria.
[Show abstract][Hide abstract] ABSTRACT: A binding site for the repressor protein BP1, which contains a tandem (AT)x(T)y repeat, is located approximately 530 bp 5' to the human beta-globin gene (HBB). There is accumulating evidence that BP1 binds to the (AT)9(T)5 allele more strongly than to other alleles, thereby reducing the expression of HBB. In this study, we investigated polymorphisms in the (AT)x(T)y repeat in 57 individuals living in Thailand, including three homozygotes for the hemoglobin E variant (HbE; beta26Glu-->Lys), 22 heterozygotes, and 32 normal homozygotes. We found that (AT)9(T)5 and (AT)7(T)7 alleles were predominant in the studied population and that the HbE variant is in strong linkage disequilibrium with the (AT)9(T)5 allele, which can explain why the betaE chain is inefficiently synthesized compared to the normal betaA chain. Moreover, the mildness of the HbE disease compared to other hemoglobinopathies in Thai may be due, in part, to the presence of the (AT)9(T)5 repeat on the HbE chromosome. In addition, a novel (AC)n polymorphism adjacent to the (AT)x(T)y repeat (i.e., (AC)3(AT)7(T)5) was found through the variation screening in this study.
Journal of Human Genetics 01/2005; 50(1):7-11. · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The hemoglobin E variant (HbE; ( beta )26Glu-->Lys) is concentrated in parts of Southeast Asia where malaria is endemic, and HbE carrier status has been shown to confer some protection against Plasmodium falciparum malaria. To examine the effect of natural selection on the pattern of linkage disequilibrium (LD) and to infer the evolutionary history of the HbE variant, we analyzed biallelic markers surrounding the HbE variant in a Thai population. Pairwise LD analysis of HbE and 43 surrounding biallelic markers revealed LD of HbE extending beyond 100 kb, whereas no LD was observed between non-HbE variants and the same markers. The inferred haplotype network suggests a single origin of the HbE variant in the Thai population. Forward-in-time computer simulations under a variety of selection models indicate that the HbE variant arose 1,240-4,440 years ago. These results support the conjecture that the HbE mutation occurred recently, and the allele frequency has increased rapidly. Our study provides another clear demonstration that a high-resolution LD map across the human genome can detect recent variants that have been subjected to positive selection.
The American Journal of Human Genetics 07/2004; 74(6):1198-208. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined a possible association of single-nucleotide polymorphisms (SNPs) in the promoters of IL-3, IL-4, and IL-13 genes on the 5q31-33, IL-3 -16T>C, IL-4 -590T>C, and IL-13 -1055C>T, with severity of malaria in 361 adult malaria patients in Thailand. The IL-13 -1055T allele showed a significant association with protection from severe malaria (OR 0.51, 95% CI 0.32-0.80; P=0.0032 by the chi(2) test), while allele frequencies of IL-3 -16T>C and IL-4 -590T>C were not statistically different between mild and severe malaria patients. An IL-13 -1055C>T has been reported to alter the regulation of IL-13 production. Thus, IL-13 -1055T may show resistance to severe malaria through the alteration of IL-13 production.
Genes and Immunity 11/2003; 4(7):528-31. · 3.68 Impact Factor