Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several human genetic factors, including red blood cell polymorphisms (ABO blood group, sickle-cell trait, G6PD deficiency) as well as point mutations in the mannose binding protein (MBP) and in the promoter regions of both the TNF-alpha and NOS2 genes, influence the severity of disease due to infection with Plasmodium falciparum. We assessed their impact on mild P. falciparum malaria, as part of a longitudinal investigation of clinical, parasitological and immunological parameters in a cohort of 300 Gabonese schoolchildren. We found the following frequencies: blood group O (0.54), sickle-cell trait (0.23), G6PD deficiency (0.09), MBP gene mutations (0.34), TNF-alpha promoter mutations (at positions -238: 0.17 and -308: 0.22) and NOS2 promoter mutation (0.18). Blood group O or hemoglobin AA were associated with protection against higher parasitemia. Girls with normal G6PD enzyme activity were protected against clinical malaria attacks. In addition, we demonstrated for the first time that the mutation at position -238 of the gene coding for the promoter region of TNF-alpha was positively correlated with the level of the antibody response specific for epitopes of the antigens MSA-2 and RAP-1 of P. falciparum.
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PMID:Human genetic factors related to susceptibility to mild malaria in Gabon. 1119 74

Fifty children from 9 families were enrolled in a longitudinal study of 8 months to evaluate individual levels of Plasmodium falciparum density in blood during asymptomatic infections. Individual parasite densities were adjusted for age and date of blood intake. The arithmetic means of these adjusted parasite densities (MAPD) were not influenced by sickle cell trait nor by G6PD enzyme activity. On the contrary, family analysis revealed the presence of similar MAPD values according to the sibships. Moreover, sibships frequently infected with P. malariae exhibited the highest P. falciparum MAPDs. The difference in aggressiveness of malaria vectors between the northern and southern halves of the village did not explain the distribution of MAPD, nor did it explain the differences in mean frequency of P. malariae infection among the sibships. We conclude that the familial characteristic of susceptibility to both P. falciparum and P. malariae infections is more likely influenced by the host's genetic background than by differences in the levels of malaria transmission.
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PMID:Family analysis of malaria infection in Dienga, Gabon. 1213 80

The ability to detect recent natural selection in the human population would have profound implications for the study of human history and for medicine. Here, we introduce a framework for detecting the genetic imprint of recent positive selection by analysing long-range haplotypes in human populations. We first identify haplotypes at a locus of interest (core haplotypes). We then assess the age of each core haplotype by the decay of its association to alleles at various distances from the locus, as measured by extended haplotype homozygosity (EHH). Core haplotypes that have unusually high EHH and a high population frequency indicate the presence of a mutation that rose to prominence in the human gene pool faster than expected under neutral evolution. We applied this approach to investigate selection at two genes carrying common variants implicated in resistance to malaria: G6PD and CD40 ligand. At both loci, the core haplotypes carrying the proposed protective mutation stand out and show significant evidence of selection. More generally, the method could be used to scan the entire genome for evidence of recent positive selection.
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PMID:Detecting recent positive selection in the human genome from haplotype structure. 1257 32

Several studies have focused their attention on the relationship between host genetic factors and susceptibility/resistance to severe malaria. However, there is a paucity of information concerning the role of host genetic factors in asymptomatic malaria, a form of low-grade Plasmodium falciparum infection without clinical symptoms. We investigated in this study the potential relationship between the host (human) genetic polymorphisms (glucose-6-phosphate dehydrogenase [G6PD], mannose binding lectin [MBL], tumor necrosis factor alpha [TNFalpha](-308) and (-238), and nitric oxide synthase 2 [NOS2](-954)) and the prevalence and profile of asymptomatic P. falciparum infection in 158 Gabonese schoolchildren. We found that G6PD A- heterozygous females (18 of 74) have a low prevalence of asymptomatic malaria (38.9% versus 67.3%; P = 0.03, by chi-square test). Children heterozygous for TNFalpha(-238) (25 of 156) carry high number of diverse infecting parasite genotypes (2.5 versus 1.99; variance F = 3.05). No statistically significant association was found between MBL, TNFalpha(-308), or NOS2 polymorphisms and asymptomatic malaria. Upon combining our data on asymptomatic forms with those from the literature for others forms, we conclude that G6PD A- heterozygous females are protected against all forms of P. falciparum malaria, and that the TNFalpha(-238A) allele confers protection against clinical malaria.
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PMID:Human genetic polymorphisms and asymptomatic Plasmodium falciparum malaria in Gabonese schoolchildren. 1264 10

As the production of NADPH in the pentose phosphate pathway is the main antioxidant defence mechanism available to the Plasmodium falciparum, we have studied the expression of P. falciparum glucose 6-phosphate dehydrogenase-6-phosphogluconolactonase (PfG6PD-6PGL) in G6PD-deficient and normal erythrocyte host cells. Both erythrocytes infected in vitro with a laboratory isolate and erythrocytes from natural human infections were used. Total RNA was prepared from parasites collected from five G6PD-deficient and nine G6PD-normal children in Ibadan, Nigeria, selected after screening 189 rural schoolchildren and 68 clinical malaria patients, and was subjected to Northern blot analysis. The probe was a cDNA fragment of the G6PD domain of the PfG6PD-6PGL gene, with an internal control probe of P. falciparum 18S ribosomal RNA. Quantification was performed using a phosphoimager. Relative to internal control, the abundance of PfG6PD-6PGL mRNA (mean +/- standard deviation) was lower in parasites from G6PD-deficient children (0.29 +/- 0.27) than in G6PD-normal control subjects (0.74 +/- 0.26) (P = 0.014, Mann-Whitney U-test). Although confirmation in a larger study is required, our results suggest a lower relative abundance of PfG6PD-6PGL, and presumably antioxidant activity, in malaria parasites from G6PD-deficient hosts, thus extending the current knowledge of the mechanism of G6PD-deficiency related host protection.
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PMID:Expression of Plasmodium falciparum G6PD-6PGL in laboratory parasites and in patient isolates in G6PD-deficient and normal Nigerian children. 1289 22

Transfusion-acquired malaria in a neonate is uncommon and factors such as drug resistance and concomitant G6PD deficiency can cause treatment difficulties. We report a 26-day-old premature infant with chloroquine-resistant malaria who underwent exchange transfusion. The aim was to correct anaemia, decrease parasitaemia and remove G6PD-deficient cells to allow successful use of quinine.
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PMID:Neonatal transfusion malaria requiring exchange transfusion. 1456 36

The aim of this study was to determine the frequency of G6PD deficiency and assess its impact on morbidity, especially anemia, in preschool-aged children in Cambodia. A total of 151 children including 82 boys and 69 girls from the Kandal province near Phnom Penh were studied. Ages ranged from 8 to 69 months. Blood was collected in EDTA-coated tubes. Blood counts were performed with an ABX Micros 60 system and G6PD in red blood cells was measured with a Roche Cobas Mira Plus system using Gamma reagents. G6PD deficiency was found in 14 cases (13.4% of boys and 4.3% of girls). Deficiency was complete in 7.3% of children and partial in 2%. Anemia defined as hemoglobin concentration less than 110 g/l was detected in 29.1% of children. No case of anemia could be attributed to enzyme deficiency since no sign of hemolysis was observed in any of the three children presenting both conditions. Further study is needed on G6PD deficiency in Cambodia including malaria-endemic areas and on the frequency and severity of jaundice due to enzyme deficiency in newborns.
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PMID:[Frequency of G6PD deficiency in a group of preschool-aged children in a centrally located area of Cambodia]. 1561 86

Molecular screening for glucose-6-phosphate (G6PD) mutations in two Jordanian populations revealed six different mutations and higher incidences of G6PD deficiency and G6PD A- (376A-->G + 202G-->A) mutation in Jordan Valley than in the Amman area. These observations may be explained by historically higher rates of malaria and African ancestral origins, respectively.
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PMID:Molecular heterogeneity of glucose-6-phosphate dehydrogenase deficiency in Jordan. 1633 Apr 44

The evidence of protection afforded by red blood cell polymorphisms against either clinical malaria or Plasmodium falciparum blood levels varies with the study site and the type of malaria transmission. Nevertheless, no clear implication of an antibody-related effect has yet been established in the protection related to red blood cell polymorphisms. We performed a prospective study, where plasma IgG and IgG subclasses directed to recombinant proteins from the merozoite surface protein 2 (MSP2/3D7 and MSP2/FC27) and the ring-infected erythrocyte surface antigen (RESA) were determined in a cohort of 413 Senegalese children before the annual malaria transmission season. The antibody response was dependent on age, and to a lesser extent, on the village of residence. IgG3 responders to all proteins, IgG responders to RESA and MSP2/3D7, as well as IgG2 to RESA and IgG1 responders to MSP2/3D7, presented enhanced mean values of parasite density, as evaluated during an 18-month follow-up. The levels of IgG and IgG3 to MSP2/3D7 were negatively associated with the risk of occurrence of a malaria attack during the following transmission season. Compared to normal children, sickle cell trait carriers presented lower levels of IgG to MSP2/3D7. Similarly, G6PD A- girls had lower levels of IgG and IgG3 to MSP2/FC27 than did G6PD normal girls. The impact of these particular genetic polymorphisms on the modulation of the antibody response is discussed.
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PMID:Impact of red blood cell polymorphisms on the antibody response to Plasmodium falciparum in Senegal. 1667 42

Numerous studies have shown that several red blood cell polymorphisms protect against severe malaria. Such a relation is much less clear for mild malaria attacks and for the asymptomatic carriage of Plasmodium falciparum. The impact of red blood cell polymorphisms on the level of parasite density was assessed in a group of 464 Senegalese children from the Sereer ethnic group, studied for 18 months. These genetic factors were also related to the malarial morbidity, investigated during 2 successive transmission seasons among 169 of these children. The frequencies of the host genetic factors in the whole group were 0.52 for blood group O, 0.13 for hemoglobin S, 0.16 for the G6PD A-deficient variant and 0.24 for alpha+-thalassemia (-alpha(3.7) deletion). Hemoglobin S was associated with protection against mild malaria attacks. None of the genetic factors was implicated in a better control of parasite densities. These associations may be particular to this ethnic group due to the specificities of malaria endemicity in this area. The pressure exerted in the area by other non-malarial infectious diseases as well as the genetic heterogeneity of circulating parasites may also contribute to these observations.
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PMID:Red blood cell polymorphisms in relation to Plasmodium falciparum asymptomatic parasite densities and morbidity in Senegal. 1685 49


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