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

It is difficult to overestimate the evolutionary pressures exerted over the past few thousand years by endemic malaria. For most of hominid evolution, these parasites probably caused little morbidity and mortality. However, as Livingstone (1964, 1967, 1971) has pointed out, the advent of slash and burn horticulture and associated sedentary living patterns dramatically changed this situation. For many human populations, endemic malaria became an evolutionary emergency. In such pressing circumstances, genetic traits which ordinarily would carry with them an intolerable genetic load actually increase in frequency. Thus, although a few antimalarial red cell characteristics such as Duffy negativity are evidently innocuous, the majority of malaria-selected traits are not. Ovalocytosis, the abnormal hemoglobins and G-6-PD deficiencies are all quite deleterious in the homo- or hemizygote. This, more than anything else, bespeaks the extraordinary evolutionary pressures exerted by malaria. Needless to say, the mechanisms by which these various red cell traits protect are incompletely known. Although our discussion of such mechanisms has revolved about parasite/host cell relationships, the actual antimalarial effect may involve more distal interactions, especially of infected erythrocytes with the immune and reticuloendothelial systems. Protection exerted by modifications of such interactions would not be revealed by in vitro culture experiments upon which we rely for much of our information. For example, as normal red cells age and senesce, they express novel surface antigens which are recognized by specific immunoglobulins (Kay, 1983). Cells which have bound such antibodies are likely recognized and destroyed rapidly by the reticuloendothelial system. The expression of such senescence antigens may be hastened in already abnormal cells subject to the additional burden of an internal parasite. Therefore, it is quite possible that congenital defects of the red cell membrane, hemoglobin and metabolism may afford protection against malaria via immunologic mechanisms rather than by blocking penetration or predisposing the cell to spontaneous intravascular lysis. To be successful in the mammalian host, erythrocytic phase of malaria must recognize and attach to the host red cell, successfully penetrate, and replicate within. Remarkably, there are antimalarial red cells which impair each one of these individual steps. In this case, the ingenuity of natural selection has been almost--but not quite--a match for that of the malaria parasite.
 ...
PMID:Antimalarial red cells. 639 Apr 55

A high frequency of nonhemolytic hereditary ovalocytosis in Malayan aborigines is thought to result from reduced susceptibility of affected individuals to malaria. Indeed, Kidson et al. recently showed that ovalocytes from Melanesians in Papua New Guinea are resistant to infection in culture by the malarial parasite Plasmodium falciparum. In order to determine if protection against parasitic invasion in these ovalocytes might be the result of some altered membrane material property in these unusual cells, we measured their membrane and cellular deformability characteristics using an ektacytometer . Ovalocytic red cells were found to be much less deformable in comparison to normal discoid red cells. Similar measurements on isolated membrane preparations revealed a marked reduction in ovalocytic membrane deformability. To produce equal deformation of ovalocytic and normal membranes, ovalocytes required an 8-10-fold increase in applied shear stress, indicating that their membrane was capable of deforming under sufficient stress. To test the possibility that this increased membrane rigidity might confer resistance to parasitic invasion, we performed an in vitro invasion assay using Plasmodium falciparum merozoites and Malayan ovalocytes of varying deformability from seven different donors. The level of infection of the ovalocytes ranged from 1% to 35% of that in control cells, and the extent of inhibition appeared to be closely related to the reduction in membrane deformability. Moreover, we were able to induce similar resistance to parasitic invasion in nonovalocytic normal red cells by increasing their membrane rigidity with graded exposure to a protein crosslinking agent. Our findings suggest that resistance to parasite invasion of Malayan ovalocytes is the result of a genetic mutation that causes increased membrane rigidity.
 ...
PMID:Rigid membranes of Malayan ovalocytes: a likely genetic barrier against malaria. 672 55

Approximately 300 blood and fecal specimens were examined in a parasitologic survey of indigenous inhabitants of the small isolated Torro Valley in the mountains of Central Sulawesi. Schistosoma japonicum was not found although the parasite is endemic in the neighboring Lindu and Napu valleys. Hookworm infection (71%) was the most common helminthiasis. The prevalences of ascariasis (3%) and trichuriasis (2%) are low for Indonesia in general but similar to those found in nearby mountainous areas of Sulawesi. Intestinal protozoa endemic to the area are: Entamoeba histolytica (8%). E. coli (23%). Endolimax nana (9%), Iodamoeba butschii (9%) and Giardia lamblia (14%). Plasmodium vivax infections were found in 4% and P. falciparum in 2% of persons examined. Brugia malayi microfilaremia was found with a prevalence of 25%. The high rate of splenic (54%) and hepatic (22%) enlargement found on examination of 206 persons of all ages is considered to be a result of combined effects of endemic malaria and hereditary ovalocytosis.
 ...
PMID:Intestinal and blood parasites in the Torro Valley, Central Sulawesi, Indonesia. 722 87

The role of the erythrocyte skeleton in the invasion process of Plasmodium falciparum was evaluated using genetically variant erythrocytes containing well-defined molecular defects in alpha spectrin (alpha Sp) or protein 4.1 from eight unrelated families. Invasion into red cells from subjects of three black families with hereditary pyropoikilocytosis (HPP) due to inheritance of alpha I/74 mutant spectrin was significantly reduced in cells both from the patients and from the relatives of these who carried asymptomatic hereditary elliptocytosis (HE). Likewise, reduced invasion was also seen in red cells from two families with HE in which the alpha I/65 variant spectrin was present. Resistance to invasion was not absolute in any sample and varied between 38% and 71% of that seen in normal cells. The decreased invasion correlated with the percentage of spectrin dimers present within the membrane of variant cells. In contrast, invasion into elliptocytes from three families that had a partial deficiency in protein 4.1 (HE/4.1+) but a normal percentage of spectrin dimers was either unchanged or increased. The precise mechanism and molecular basis behind the reduced invasion into HPP and HE red cells bearing Sp alpha I domain variants remains to be elucidated but might relate to alterations in merozoite/red cell-receptor interactions and/or merozoite endocytosis. The occurrence of elliptocytosis with spectrin defects (in particular, Sp alpha I/65 and Sp alpha I/46 variants in West Africa) suggests that these mutations of the alpha Sp gene could be related to some protection against malaria.
 ...
PMID:Erythrocytes carrying mutations in spectrin and protein 4.1 show differing sensitivities to invasion by Plasmodium falciparum. 772 14

Man evolved as a hunter-gatherer, and the invention and spread of agriculture was followed by changes in diet, the environment and population densities which have resulted in globally high prevalences of anaemias due to nutritional deficiencies of iron, folate and (locally) vitamin B12, to infestations by hookworm and schistosomes, to malaria, and to the natural selection for the genes for sickle-cell diseases, beta-thalassaemias, alpha-thalassaemias, glucose-6-phosphate dehydrogenase deficiency, ovalocytosis and possibly (locally) elliptocytosis. The present explosion of population is driving an expansion of agriculture, especially the cultivation of rice, and this has led often to disastrous increases of transmission of malaria, schistosomiasis and other diseases, to widespread chemical pollution, and to degradation of the environment. Anaemia, as the commonest manifestation of human disease, is a frequent consequence. The urgent need for increased food production is matched by the urgent need for assessment and control of the health impact of agricultural development.
 ...
PMID:Agriculture-related anaemias. 775 42

To assess natural immunity against the circumsporozoite (CS) protein and the synthetic vaccine SPf66, immunologic studies were carried out in a highly endemic malarious area of Papua New Guinea. Antibody prevalence, antibody titers, and T cell proliferation against both antigens were measured in 214 adults. Immunologic data were analyzed with respect to longitudinal malariologic and morbidity data. Evidence of genetic traits such as glucose-6-phosphate dehydrogenase deficiency and ovalocytosis was analyzed. Antibody prevalence was high, with 79% and 84% for CS protein and SPf66, respectively, while T cell proliferation was infrequent and low, with 14% and 12% responders, respectively. Anti-CS protein antibodies increased with age but showed no association to malaria indices or morbidity. No protective value was observed with T cell responses or with humoral response to SPf66. These results provide a first description of naturally developed immunity against SPf66 and suggest further studies in to fully understand the mechanism of immunity against this antigen.
 ...
PMID:Assessment of the humoral and cell-mediated immunity against the Plasmodium falciparum vaccine candidates circumsporozoite protein and SPf66 in adults living in highly endemic malarious areas of Papua New Guinea. 794 57

The composition of the erythrocyte plasma membrane is extensively modified during the intracellular growth of the malaria parasite Plasmodium falciparum. It has been previously shown that an 80-kD phosphoprotein is associated with the plasma membrane of human red blood cells (RBCs) infected with trophozoite/schizont stage malaria parasites. However, the identity of this 80-kD phosphoprotein is controversial. One line of evidence suggests that this protein is a phosphorylated form of RBC protein 4.1 and that it forms a tight complex with the mature parasite-infected erythrocyte surface antigen. In contrast, evidence from another group indicates that the 80-kD protein is derived from the intracellular malaria parasite. To resolve whether the 80-kD protein is indeed RBC protein 4.1, we made use of RBCs obtained from a patient with homozygous 4.1(-) negative hereditary elliptocytosis. RBCs from this patient are completely devoid of protein 4.1. We report here that this lack of protein 4.1 is correlated with the absence of phosphorylation of the 80-kD protein in parasite-infected RBCs, a finding that provides conclusive evidence that the 80-kD phosphoprotein is indeed protein 4.1. In addition, we also identify and partially characterize a casein kinase that phosphorylates protein 4.1 in P falciparum-infected human RBCs. Based on these results, we suggest that the maturation of malaria parasites in human RBCs is accompanied by the phosphorylation of protein 4.1. This phosphorylation of RBC protein 4.1 may provide a mechanism by which the intracellular malaria parasite alters the mechanical properties of the host plasma membrane and modulates parasite growth and survival in vivo.
 ...
PMID:Phosphorylation of protein 4.1 in Plasmodium falciparum-infected human red blood cells. 819 70

In this investigation, we have measured the invasion and growth of the malaria parasite Plasmodium falciparum into elliptocytic red blood cells (RBCs) obtained from subjects with homozygous hereditary elliptocytosis. These elliptocytic RBCs have been previously characterized to possess molecular defects in protein 4.1 and glycophorin C. Our results show that the invasion of Plasmodium falciparum into these protein 4.1 (-) RBCs is significantly reduced. Glycophorin C (-) Leach RBCs were similarly resistant to parasite invasion in vitro. The intracellular development of parasites that invaded protein 4.1 (-) RBCs was also dramatically reduced. In contrast, no such reduction of intracellular parasite growth was observed in the glycophorin C (-) Leach RBCs. In conjunction with our recent finding that a third protein termed p55 is also deficient in protein 4.1 (-) and glycophorin C (-) RBCs, the present data underscore the importance of the membrane-associated ternary complex between protein 4.1, glycophorin C, and p55 during the invasion and growth of malaria parasites into human RBCs.
 ...
PMID:Reduced invasion and growth of Plasmodium falciparum into elliptocytic red blood cells with a combined deficiency of protein 4.1, glycophorin C, and p55. 860 65

South-east Asian ovalocytosis status was determined in 1629 individuals originating from 12 different geographical areas of Papua New Guinea, representing different ethnic groups and degrees of malaria endemicity. This was achieved by using polymerase chain reaction amplification to demonstrate a 27 base pair deletion in the erythrocyte band 3 (AE1) gene. By using this method, the prevalence of erythrocyte band 3 gene deletion was determined to range from zero in both the lowland inland area of Wosera, East Sepik Province and the highland region of Goroka, Eastern Highlands Province to 35% on the north coast of Madang Province. In general, the prevalence correlated well with altitude, being highest on the coast where malaria transmission is high, intermediate in the lowlands, and lowest in the non-malarious highlands. However, Wosera, a lowland area in the Sepik River Plains, which is hyperendemic for malaria, was an exception in that no ovalocytosis was detected. These results largely confirm the prevalence rates that have been reported in the past using microscopy. In keeping with the autosomal dominant mode of inheritance, the male:female ratio was 1.02 and no homozygote was detected, indicating that homozygosity for the ovalocytosis band 3 gene deletion is lethal.
 ...
PMID:Occurrence of the erythrocyte band 3 (AE1) gene deletion in relation to malaria endemicity in Papua New Guinea. 875 56

Southeast-Asian ovalocytosis (SAO) was diagnosed in children from Madang, Papua New Guinea, by detection of the SAO band 3 gene variant using the polymerase chain reaction. SAO band 3 was present in 16/241 (6.6%) children living in the community and 32/389 (8.2%) children with acute Plasmodium falciparum malaria (P=0.42). SAO band 3 was detected in 8.2% (23/281) of alpha+-thalassaemia homozygotes, 9.4% (20/214) of heterozygotes and 2.4% (2/85) of children with a normal alpha-globin genotype (P=0.12). The most consistent feature of SAO band 3 on microscopy of thin blood films was red cells with two or more linear or irregularly-shaped pale regions. In children living in the community, these were present in 15 with SAO band 3 (sensitivity 93.8%) and only two normals (specificity 99.1%). The presence of > or = 20% ovalocytosis was a poorer indicator of SAO band 3 (sensitivity 68.8% and specificity 100%). Haematological data were similar in SAO band 3 and normal children. However, in children with acute malaria, haemoglobin levels and red cell counts were significantly lower in SAO band 3 than normal children. The degree of ovalocytosis was lower in children with SAO band 3 during acute malaria, suggesting that a selective loss of ovalocytes may contribute to malaria anaemia in Southeast-Asian ovalocytosis.
 ...
PMID:Red cell morphology and malaria anaemia in children with Southeast-Asian ovalocytosis band 3 in Papua New Guinea. 963 78


<< Previous 1 2 3 4 Next >>