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

Because malaria-stimulated cytokine production may have deleterious effects on human immunodeficiency virus type 1 (HIV-1) replication, the effects of Plasmodium falciparum antigens on HIV-1 replication were studied. Stimulation with malarial antigens significantly enhanced HIV-1 replication of HIV-1LAV and primary HIV-1 isolates (subtype A) in CD8-depleted peripheral blood mononuclear cells from naive donors. The malarial antigen-induced activation of HIV-1 was due to cellular activation as judged by the expression of cell activation markers and proliferative responses. While malarial antigen stimulation increased expression of tumor necrosis factor (TNF-alpha) and interleukin-6 (IL-6), only monoclonal antibodies (MAbs) to TNF-alpha inhibited malarial antigen-induced HIV-1 replication, whereas MAb to IL-6 had no effect. Malarial antigen increased HIV-1 replication by increasing viral mRNA expression and by activating long terminal repeat-directed viral transcription. These data suggest that P. falciparum infection can modulate HIV-1 pathogenesis by activating lymphocytes and stimulating viral replication through the production of cytokines.
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PMID:Plasmodium falciparum antigen-induced human immunodeficiency virus type 1 replication is mediated through induction of tumor necrosis factor-alpha. 946 33

Co-infections such as Mycobacterium tuberculosis (TB) and Pneumocystis pneumonia may affect the progress of HIV infection and speed the onset of death. As malaria and syphilis are both endemic in West Africa we examined their effects on HIV-2 infection, for these may also accelerate the progress of disease. A community-based case-control study was undertaken in a rural village in Guinea-Bissau, West Africa. One hundred and fifty asymptomatic subjects seropositive for HIV-2 and 154 age- and sex-matched controls were enrolled. Venous blood samples taken into EDTA were stained within six hours of collection with CD4 and CD8 monoclonal antibodies and processed by Q-Prep machine in the field. The stained cells were then transported on ice by road and analysed by FACS-can at the base laboratory in The Gambia within a week. The mean CD4% was significantly lower and geometric mean neopterin and beta 2-microglobulin levels were significantly higher in the HIV-2-infected subjects than in the controls (P < 0.01 for all cases versus all controls). The mean CD4% was lower and beta 2-microglobulin level was higher in both HIV-2 and control subjects with active or past syphilis when compared with subjects with no syphilis; however, syphilis did not have a marked effect on plasma neopterin level. Malaria infection raised neopterin levels, but had little effect on CD4%. Overall multiple regression analysis allowing for HIV-2 infection and other variables showed that syphilis lowered CD4% (P = 0.01) and raised beta 2-microglobulin levels (P = 0.05) and malaria raised neopterin levels (P = 0.05). The conclusions are that HIV-2 infection is associated with lower CD4% and higher neopterin and beta 2-microglobulin levels than controls, and co-infection with syphilis is associated with a further lowering of CD4%, suggesting a worse suppression of the immune system. Co-infection with malaria is associated with a modest immune disturbance.
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PMID:Immune stimulation by syphilis and malaria in HIV-2-infected and uninfected villagers in West Africa. 962 34

The production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by lymphocytes was examined in murine malaria. When spleen cells or lymph node cells from P. berghei-infected mice were cultured in vitro with malaria antigen, the GM-CSF production correlated with the incubation time up to 72 hours. When lymphocytes obtained at various days after infection were cultured with the antigen, GM-CSF became detectable as early as 2 days after infection, reached a peak at day 9 and then rapidly decreased. Production of GM-CSF was antigen-specific, and related to the dose of antigen. Treatment of lymphocytes with anti-Thy-1.2 antibody and complement resulted in almost complete loss of GM-CSF-producing activity, while treatment with either anti-CD4 or anti-CD8 antibody and complement resulted in partial loss of GM-CSF-producing activity, indicating that both CD4+ and CD8+ T cells are involved in GM-CSF production in malaria. GM-CSF exhibits glycoprotein nature, and has an apparent molecular weight of 36,000. The molecular properties of this T-cell derived GM-CSF were compared with those of known lymphokine GM-CSF.
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PMID:Granulocyte-macrophage colony-stimulating factor production by T lymphocytes in Plasmodium berghei-infected mice. 965 99

Subcutaneous administration in mice of recombinant Sindbis viruses expressing a class I major histocompatibility complex-restricted 9-mer epitope of the Plasmodium yoelii circumsporozoite protein or the nucleoprotein of influenza virus induces a large epitope-specific CD8(+) T-cell response. This immunization also elicits a high degree of protection against infection with malaria or influenza A virus.
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PMID:Recombinant Sindbis viruses expressing a cytotoxic T-lymphocyte epitope of a malaria parasite or of influenza virus elicit protection against the corresponding pathogen in mice. 965 44

CD8(+) T cells have been implicated as critical effector cells in protective immunity against malaria parasites developing within hepatocytes. A vaccine that protects against malaria by inducing CD8(+) T cells will probably have to include multiple epitopes on the same protein or different proteins, because of parasite polymorphism and genetic restriction of T-cell responses. To determine if CD8(+) T-cell responses against multiple P. falciparum proteins can be induced in primates by immunization with plasmid DNA, rhesus monkeys were immunized intramuscularly with a mixture of DNA plasmids encoding four P. falciparum proteins or with individual plasmids. All six monkeys immunized with PfCSP DNA, seven of nine immunized with PfSSP2 DNA, and five of six immunized with PfExp-1 or PfLSA-1 DNA had detectable antigen-specific cytotoxic T lymphocytes (CTL) after in vitro restimulation of peripheral blood mononuclear cells. CTL activity was genetically restricted and dependent on CD8(+) T cells. By providing the first evidence for primates that immunization with a mixture of DNA plasmids induces CD8(+) T-cell responses against all the components of the mixture, these studies provide the foundation for multigene immunization of humans.
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PMID:Simultaneous induction of multiple antigen-specific cytotoxic T lymphocytes in nonhuman primates by immunization with a mixture of four Plasmodium falciparum DNA plasmids. 971 67

Experimental cerebral malaria (ECM) can be induced in C57B1 mice by infection with Plasmodium berghei K173 parasites. Behavioral changes shortly before they die of ECM may reflect disturbance of the integrity of the blood-brain barrier (BBB). Folic acid elicits strong convulsive activity if the permeability of the BBB is increased. Administration of folic acid to mice during development of ECM induced convulsions. Interventions known to prevent fatal outcome from ECM, such as splenectomy or treatment with anti-CD4 or anti-CD8 monoclonal antibodies, also prevented sensitivity to folic acid-induced convulsions. In addition, infected mice with ECM and sensitive to folic acid-induced convulsions, recovered from this sensitivity after treatment with anti-T cell antibodies within 4 h. These data suggest that disturbance of the permeability of the BBB can be reversed and depends on the involvement of T cells.
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PMID:Convulsions due to increased permeability of the blood-brain barrier in experimental cerebral malaria can be prevented by splenectomy or anti-T cell treatment. 980 67

Trypanosoma cruzi was transformed with the Plasmodium yoelii gene encoding the circum-sporozoite (CS) protein, which contains the well-characterized CD8+ T cell epitope, SYVPSAEQI. In vivo and in vitro assays indicated that cells infected with the transformed T. cruzi could process and present this malaria parasite-derived class I MHC-restricted epitope. Immunization of mice with recombinant influenza and vaccinia viruses expressing the SYVPSAEQI epitope induced a large number of specific CD8+ T cells that strongly suppressed parasitemia and conferred complete protection against the acute T. cruzi lethal infection. CD8+ T cells mediated this immunity as indicated by the unrelenting parasitemia and high mortality observed in immunized mice treated with anti-CD8 antibody. This study demonstrated, for the first time, that vaccination of mice with vectors designed to induce CD8+ T cells is effective against T. cruzi infection.
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PMID:Induction of CD8+ T cell-mediated protective immunity against Trypanosoma cruzi. 1006 11

Protective immunity to malaria has been achieved in human volunteers utilizing the pre-erythrocytic Plasmodium falciparum antigen, the circumsporozoite protein (CS). However, T cell reactivity to CS is focused on several highly polymorphic T cell epitope regions, potentially limiting the efficacy of any vaccine to specific malaria strains. Another important pre-erythrocytic malaria antigen, the thrombospondin-related adhesive protein (TRAP), can induce protection in animal models of malaria, but knowledge of human T cell responses is limited to the identification of CD8 T cell epitopes, with no CD4 epitopes identified to date. This comprehensive study assessed reactivity to overlapping peptides spanning almost the whole of P. falciparum TRAP (PfTRAP), as well as peptides selected on the basis of HLA class II-binding motifs. A total of 50 naturally exposed Gambian adults were assessed to define 26 T cell epitopes in PfTRAP capable of inducing rapid IFN-gamma or IL-4 production, as assessed by enzyme-linked immunospot assays. In contrast to the CS protein, this reactivity was broadly distributed along the length of TRAP. Moreover, of the 26 epitopes identified, 10 were found to be conserved in West Africa.
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PMID:Broadly distributed T cell reactivity, with no immunodominant loci, to the pre-erythrocytic antigen thrombospondin-related adhesive protein of Plasmodium falciparum in West Africans. 1038 57

The frequency of cytokine-producing CD4-/CD8- mononuclear cells was assessed in patients of different age groups (29 infants, aged 1-5 years; 30 schoolchildren, aged 6-14 years, 26 adults, aged > 15 years) with acute Plasmodium falciparum malaria, from Gabon. Fifteen patients were followed up before antimalarial treatment (day 0), during parasite clearance (day 3) and after resolution of parasitemia (day 10). By using flow cytometry for intracellular detection of cytokines, a striking expansion of CD4-/CD8- cells producing the type 1 cytokines interleukin (IL)-2-/interferon (IFN)-gamma+, IL-2+/IFN-gamma+ and IL-2+/IFN-gamma- was observed in adults as compared with children. Type 2 cytokine expression (IL-4+/IFN-gamma-, IL-13+/IFN-gamma-) and type 0 cells (IL-4+/IFN-gamma+, IL-13+/IFN-gamma+) were not significantly different between the three age groups. Patients with severe malaria had a significantly increased frequency of type 2 cytokine-producing CD4-/CD8- cells. Drug-induced clearance of parasitemia was characterized by a decrease of IL-2+/IFN-gamma- and type 2 cytokine expressing CD4-/CD8- cells and by a gradual increase of IL-10+/IFN-gamma- expression. The type 1/type 2 dichotomy observed within the CD4-/CD8- cell population is likely to be of significance in the host response against P. falciparum malaria.
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PMID:Frequency of cytokine-producing CD4-CD8- peripheral blood mononuclear cells in patients with Plasmodium falciparum malaria. 1040 Aug 21

Malaria, a disease responsible for immense human suffering, is caused by infection with Plasmodium spp. parasites, which have a very complex life cycle - antigenically unique stages infect different tissues of the body. This review details recent developments in our understanding of immunity both to pre-erythrocytic stage antigens and to erythrocytic stage antigens. The former is largely mediated via CD8(+) T cells and involves IFN-gamma, nitric oxide, IL-12 and natural killer cells; the latter varies (in different hosts and with different parasites) but is largely mediated by antibody, helper T cells, nitric oxide and gammadelta T cells. The recent progress towards clinical trials of vaccine candidates against both the pre-erythrocytic stage and erythrocytic stage is also summarized, in particular the use of heterologous prime/boost strategies for the former and the use of MSP1 as a candidate vaccine for the latter.
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PMID:Immune effector mechanisms in malaria. 1044 41


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