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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In mice, immune responses to subunits of defined malaria antigens are regulated by genes mapping within the MHC and it has been suggested that such genetic restriction will be a major obstacle in the development of a human malaria vaccine. The relationship between class II human leukocyte antigen (HLA) genes and immune recognition of three candidate antigens for a vaccine against Plasmodium falciparum malaria has been investigated in a human population living in a malaria endemic area of West Africa. The study population was shown to be extremely heterogeneous for HLA class II alleles and marked differences in allelic frequency were detected between members of different ethnic groups. One class II DQA-DQB combination (serological specificity DQw2) was particularly common among members of the Fula ethnic group. This haplotype was significantly associated with higher than average levels of antibody to a peptide epitope, (EENV)6, of the malaria antigen Pf155/RESA. There was little evidence of association between HLA class II genotype and cellular proliferative or interferon gamma responses to the antigens tested. Overall, the number of significant associations between immune responses and specific HLA class II haplotypes was greater than would be expected by chance but less than would be expected if class II-dependent genetic restriction were a major factor governing human immune responses to malaria antigens. Thus, although some qualitative variation in the immune response to vaccine antigens may occur in ethnically different target populations, widespread HLA-associated nonresponsiveness to a multivalent subunit malaria vaccine is unlikely.
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PMID:MHC and malaria: the relationship between HLA class II alleles and immune responses to Plasmodium falciparum. 139 Apr 36

We have measured cellular and humoral immune responses to short synthetic peptides representing epitopes of the malaria vaccine candidate antigen Pf155/RESA in a longitudinal, prospective study of clinical immunity to Plasmodium falciparum malaria in a cohort of 354 Gambian children aged 3-8 years. A significant association was observed between presence of antibodies to the 3' repeat region peptide (EENV)6 and resistance to clinical malaria. The prevalence of protective antipeptide antibodies varied significantly between different ethnic groups, suggesting that immune recognition of some Pf155/RESA epitopes may be genetically regulated. There was no obvious association between proliferative or interferon gamma responses to T cell epitopes of Pf155/RESA and resistance to malaria infection or disease. At an individual level, the presence of peptide-binding antibodies was associated with the induction of interleukin 4 messenger ribonucleic acid expression in T cells activated with the overlapping T cell epitope EENVEHDA(EENV)2. This suggests that measurement of interleukin 4 production by T cells may represent a functional assay for T helper activity.
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PMID:Association between immune recognition of the malaria vaccine candidate antigen Pf155/RESA and resistance to clinical disease: a prospective study in a malaria-endemic region of west Africa. 175 42

Malaria infection crisis, at which the parasitemia drops precipitously and the parasite loses infectivity to the mosquito vector, occurs in many natural malaria systems, and has not been explained. We demonstrate that in a simian malaria parasite (Plasmodium cynomolgi in its natural host, the toque monkey), the loss of infectivity during crisis is due to the death of circulating intraerythrocytic gametocytes mediated by crisis serum. These parasite-killing effects in crisis serum are due to the presence in the serum of cytokines tumor necrosis factor and interferon gamma, which are produced by the host as a result of the malaria infection. The killing activity of each cytokine is absolutely dependent upon the presence of additional, as yet unidentified factor(s) in the crisis serum.
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PMID:Cytokines kill malaria parasites during infection crisis: extracellular complementary factors are essential. 190 73

Plasma levels of tumour necrosis factor (TNF) were significantly higher in 178 Gambian children with uncomplicated malaria due to Plasmodium falciparum than in 178 children with other illnesses. 110 children with cerebral malaria were studied shortly after admission to hospital; 28 subsequently died. Compared with the children with uncomplicated malaria, mean plasma TNF levels were twice as high in cerebral malaria survivors and ten times as high in the fatal cases. Although high TNF levels were associated with high parasitaemia and with hypoglycaemia, they predicted fatal outcome in cerebral malaria independently of parasitaemia and glucose concentrations. Concentrations of interleukin-1 alpha, but not interferon gamma, were also related to the severity of malaria. We conclude that increased TNF production is a normal host response to P falciparum infection, but that excessive levels of production may predispose to cerebral malaria and a fatal outcome.
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PMID:TNF concentration in fatal cerebral, non-fatal cerebral, and uncomplicated Plasmodium falciparum malaria. 197 68

Earlier, we reported that prophylactic treatment with human interferon gamma (rHuIFN-gamma) protected monkeys against Plasmodium cynomolgi B malaria infection. We have tested the efficacy of rHuIFN-gamma on relapsing stage of experimental P. cynomolgi B malaria infection in rhesus monkeys. No effect of rHuIFN-gamma was seen against experimental relapsing stage compared with controls; however, it appears that chloroquine (CHL) may have interfered with the antimalarial effect of IFN, since treatment with CHL inhibits the antiviral activity of mouse alpha/beta IFN and polyinosinic-polycytidylic acid (poly I:C) against Semliki forest virus (SFV) in mice. These results may have clinical implications especially with the use of IFN against virus infection, cancer and in parasitic infections in malaria endemic areas where CHL is one of the most widely used antimalarial drugs. Our result also shows that CHL treatment enhances the virus replication in mice and suggest a possible connection between AIDS and malaria infection, since the spread of AIDS has been rapid in parts of tropical Africa that have a high incidence of malaria, and chloroquine has been frequently used in the chemotherapy of malaria.
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PMID:Effects of interferon in malaria infection. 212 28

We have tested the prophylactic effect of Escherichia coli-derived recombinant human interferon gamma (rHuIFN-(gamma] against sporozoite- or trophozoite-induced Plasmodium cynomolgi B malaria infection in rhesus monkeys. Data show that treatment with only five doses of rHuIFN-(gamma) (0.1 mg/kg body weight) given on days -2, 0, and +2 after infection protected the monkeys against sporozoite-induced P. cynomolgi infection. Animals initially protected by rHuIFN-(gamma) treatment remained susceptible to reinfection. No inhibitory effect of rHuIFN-(gamma) was seen against trophozoite-induced infection. We have also tested the effect of recombinant human tumour necrosis factor (rHuTNF) in rhesus monkeys. No significant activity of TNF was seen against trophozoite-induced P. cynomolgi B infection. rHuIFN-(gamma) inhibited schizogony in functional human hepatocytes infected with P. falciparum sporozoites. These results suggest that the inhibitory effect of IFN is limited to the exoerythrocytic stage of parasite development. Interleukin-1 (IL-1) also inhibited hepatic development of P. falciparum sporozoites; however, IL-1 treatment was effective only when applied before sporozoite inoculation. IL-2 and TNF were effective in higher doses.
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PMID:The role of cytokines in malaria infection. 212 26

In cerebral malaria, pathological changes can be found in the brain of infected people and in the brain of Plasmodium berghei-infected mice. The pathogenesis of cerebral malaria in mice is believed to be due to an immunopathological reaction giving rise to an excessive production of cytokines such as interferon gamma (IFN-gamma) and tumor necrosis factor (TNF). We find that low doses of interleukin 1 (IL-1) protect mice against cerebral malaria; IL-1 also inhibits parasitemia. The IL-1 effect on parasitemia was not observed in nude mice and was at least partly reversed in mice treated with IL-1 in combination with antibody to IFN-gamma, indicating the involvement of T cells. Mice protected against development of cerebral malaria by IL-1 treatment developed the syndrome when TNF was given as observed in control infected mice or infected mice treated with inactivated IL-1.
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PMID:Low dosages of interleukin 1 protect mice against lethal cerebral malaria. 223 Jun 43

Experimental cerebral malaria (ECM), a lethal hyperacute neurological syndrome associated with high blood levels of tumor necrosis factor, develops in genetically susceptible (CBA/Ca) mice 7 days after infection with Plasmodium berghei ANKA strain. Injections of neutralizing monoclonal antibody against recombinant murine interferon gamma, not later than 4 days after infection, markedly reduced the incidence of ECM and the elevation in serum levels of tumor necrosis factor. This treatment prevented the cerebral lesions (plugging of brain vessels by monocytes, lymphocytes, and parasitized erythrocytes). In contrast, the extent of macrophage infiltration in lymphoid organs (which is a characteristic feature of mice developing ECM), as well as the course of infection, remained unaffected by the antibody treatment. Protected mice died at a later time of severe anemia and overwhelming parasitemia, the usual outcome of P. berghei infection in mice that are not susceptible to ECM. The present data indicate that interferon gamma constitutes an important link in the cytokine network that leads to brain vessel inflammation in experimental malaria. It is proposed that interferon gamma released by activated CD4+ T cells acts by augmenting both production and action of tumor necrosis factor.
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PMID:Monoclonal antibody against interferon gamma can prevent experimental cerebral malaria and its associated overproduction of tumor necrosis factor. 250 93

Earlier we reported that prophylactic treatment with recombinant human interferon gamma (rHuIFN-gamma) for a prolonged duration completely suppressed experimental infection with Plasmodium cynomolgi B sporozoites in rhesus monkeys. We now show that reducing the rHuIFN-gamma treatment to three administrations given close to the time (on days -1, 0, and +1) of infection was sufficient for complete protection. Animals initially protected by rHuIFN-gamma treatment are susceptible to reinfection. Studies are in progress to understand the precise mechanism of protection afforded by HuIFN-gamma against sporozoite-induced malaria infection.
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PMID:Human interferon-gamma protects rhesus monkeys against sporozoite-induced Plasmodium cynomolgi malaria infection. 313 12

The effects of Plasmodium falciparum proteins released in asexual blood stage culture supernatants on human T-lymphocytes from malaria non-immune donors were examined. Supernatants from several plasmodial strains stimulated both CD+4 and CD+8 T-lymphocytes to proliferate and secrete interferon gamma in vitro. Active moieties were predominantly released during the final stages of the parasite cycle. They were enriched by gel filtration and were further purified by anion-exchange and Superose 12 column fast protein liquid chromatography. Three active fractions of apparent 250, 70 and 18 kilodaltons were identified. The parasitic origin of the predominant 70-kilodaltons protein(s) was shown by biosynthesis experiments with radioactive amino acid precursors and was also demonstrated by in vitro translation of parasitic mRNA species. Interestingly, antibodies to the 70-kilodalton exoprotein(s) also reacted to a schizont protein of similar molecular weight.
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PMID:Plasmodium falciparum exoprotein stimulation of human T-lymphocytes unsensitized to malaria. 313 89


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