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

Burkitt's lymphoma occurs mainly in parts of tropical Africa and has attracted the attention of experimental workers due to its epidemiological and clinical features, which indicate a viral etiology and a host immune response to the tumor. As a result of virological studies, Epstein-Barr virus (EBV) DNA has been demonstrated in almost all tested biopsies of African BL. This contrasts to the absence of EBV in all, or almost all, of the non-African Burkitt's lymphoma-like tumors, even though the number of tested tumors in this group is small, and to the lack of EBV in all other types of lymphoma or leukemia. Immunological studies have revealed the presence of antibodies to different EBV-associated antigens in all African patients with Burkitt's lymphoma. However the antibodies are not specific for Burkitt's lymphoma but are found in most adults all over the world, although at lower levels. They cannot therefore serve diagnostic purposes, but they can give prognostic information and occasionally give clues to the mechanisms behind late tumor recurrences, and possibly guide so-called immunotherapy. Burkitt's lymphoma patients contrast to appropriate control groups where some of the persons are anti-EBV seronegative, and this, together with the presence of EBV in Burkitt's lymphoma biopsies and the absence of EBV in other lymphomas, even though the cell type involved may be infectable by EBV in vitro and the tumor may arise in an EBV-carrying person, favors an etiological role in EBV in Burkitt's lymphoma and speaks against the "passenger" hypothesis, according to which EBV is picked up by the Burkitt's lymphoma cell which happens to be particularly suitable for EBV persistence. To explain the geographical distribution, a cofactor, such as certain forms of malaria, has been implied.
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PMID:Burkitt's lymphoma - a human tumor model system for immunological studies. 17 35

Infections with both Epstein-Barr virus (EBV) and malaria have been implicated as causal factors in the pathogenesis of Burkitt's lymphoma (BL). Proposed trials of preventive measures for both infections are receiving serious consideration as possible means of establishing a causal relationship with BL. In this paper we examine certain models for the interaction of EBV and malaria in the induction of BL, and also review the aims of the longitudinal, population-based study being conducted in the West Nile District of Uganda. Given existing knowledge, the outcome of preventive trials, even for the most simple interaction models, is unpredictable and, under certain circumstances, trials of an EBV vaccine could actually increase the incidence of BL. It is suggested that trials of an EBV vaccine at this time would be premature and should be delayed at least until the results from the West Nile prospective study are clear.
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PMID:Epstein-Barr virus-malaria interaction models for Burkitt's lymphoma: implications for preventive trials. 17 23

Epidemiology of tropical Burkitt's lymphoma shows the concomitant existence of the three following characteristics in endemic areas: - fairly dense rural population with a low standard of living; - early occurrence of primary infection by the Epstein-Barr virus (whose genome is always present in all tumour cells); - stable malaria. The social and economic level of these areas accounts for the specific features of the viral infection. Climatic factors determine permanent of prolonged transmission of malaria which could be mediated through a mitogen. Eradication of malaria could be a useful way to induce a fall in Burkitt's lymphoma incidence.
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PMID:[Epidemiology of Burkitt's lymphoma in tropical areas - its relationship with malaria (author's transl)]. 34 30

The epidemiology of Epstein-Barr virus (EBV) infection in populations at different risk for EBV-associated diseases indicates significant differences between the populations. EBV infection takes place much earlier in Uganda, where all children are infected before the age of 2 to 3 years, than in Southeast Asia, where nasopharyngeal carcinoma is prevalent. It is proposed that such early infection in Equatorial Africa is related to the risk for Burkitt's lymphoma. Four possible interventions to control EBV-associated diseases are presented: (a) simple hygienic measures to delay natural primary infection by EBV; (b) EBV vaccine; (c) intervention against cofactors such as malaria in Burkitt's lymphoma; and (d) characterization of high-risk groups to allow early detection and successful treatment.
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PMID:Epstein-Barr virus behavior in different populations and implications for control of Epstein-Barr virus-associated tumors. 125 56

Nine human monoclonal antibodies (MoAbs) recognizing 7 different antigenic structures of blood-stages of the human malarial parasite P. falciparum (Pf) were produced by Epstein-Barr virus transformed B-cell lines (EBV-TCL) with or without fusion to the lymphoblastoid cell line KR4. The peripheral blood B-lymphocytes were obtained from 8 Gambian donors immune to Pf malaria. Two of the EBV-TCL could be expanded and maintained for more than 6 months but neither one could be cloned. Six additional EBV-TCL were stabilized after fusion with the KR4 lymphoblastoid cell line. All resulting hybridomas permitted easy cloning. Some of the MoAbs produced distinct fluorescent staining patterns of asexual Pf blood-stage parasites when using high-resolution digitized video-intensified fluorescence microscopy. Antigens on 195 kD and 155 kD proteins were recognized by 3 and 1 MoAb, respectively, using Western blotting and immunoprecipitation techniques.
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PMID:Human monoclonal antibodies against Plasmodium falciparum: production, stabilization and characterization. 127 3

The function of c-myc in physiology is only partially known. Its product has DNA binding properties and plays a role in the control of proliferation and differentiation. In general, increased c-myc expression leads to proliferation and abolishment of differentiation. The involvement of c-myc in mouse plasmacytomas and human Burkitt's lymphoma is well known: due to chromosomal translocation c-myc comes under the influence of regulatory elements of immunoglobulin genes, leading to increased expression of the gene and proliferation of the cells. In man, the chromosomal translocations may occur within the increased pool of (pre) B-cells due to Epstein Barr virus (EBV) and malaria infection with subsequent immunosuppression. Apart from these early (primary?) events in lymphomagenesis, c-myc is also often involved in tumour progression, probably by a similar mechanism. Different types of c-myc involvement are associated with specific types of lymphoma: there are differences between endemic, sporadic and ileocecal Burkitt's lymphoma as well as between those and primary extranodal large cell lymphoma and large cell lymphoma which has progressed. These differences are associated with the differentiation of the involved lymphoid cells and may point to the stage of differentiation in which the oncogenic event occurred.
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PMID:The association of c-myc rearrangements with specific types of human non-Hodgkin's lymphomas. 149 39

The new-world monkeys Saimiri sciureus (squirrel monkeys) are currently used as a model to test the efficacy of vaccines against human malaria. To improve our knowledge on this model, we tested the susceptibility of S. sciureus B cells to Epstein-Barr virus (EBV) infection. B-lymphoblastoid cell lines were obtained from six of six healthy animals after infection with the B95-8 source of EBV. The frequency distributions of spleen B cells clonally committed to the production of immunoglobulins M and G, as measured by limiting dilution analysis, were from 1 in 179 to 1 in 1,085 and from 1 in 45 to 1 in 60, respectively, in three monkeys naturally infected with Plasmodium brasilianum. In the same three animals, the frequency of spleen B cells committed to the production of P. brasilianum-specific antibody ranged from 1 in 2,211 to 1 in 9,099. One B-lymphoblastoid cell line producing anti-P. brasilianum-specific antibody was cloned twice, and the immunoglobulin G produced was purified. This monoclonal antibody recognized a parasite component of 197 kDa and was specific for Plasmodium malariae and P. brasilianum parasites. These data document that squirrel monkey B cells naturally primed by an infectious agent can be efficiently used to produce monospecific antibodies against the infectious agent.
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PMID:Epstein-Barr virus transformation of Saimiri sciureus (squirrel monkey) B cells and generation of a Plasmodium brasilianum-specific monoclonal antibody in P. brasilianum-infected monkeys. 164 69

Burkitt's lymphoma (BL) is a highly malignant B cell tumor characterized by three types of chromosomal translocation which constitutively activate the c-myc oncogene by juxtaposing it to Ig coding sequences. Epstein-Barr virus (EBV) infection, hyperendemic malaria and HIV-caused immunosuppression are thought to contribute to the pathogenesis of the tumor. Cell lines derived from EBV carrying and EBV negative BLs often show altered MHC class I antigen expression. The defects include a lower expression of all HLA class I antigens compared to EBV transformed normal B-blasts, and selective down-regulation of certain HLA-A and HLA-C alleles. As a consequence BL cells are often resistant to cytotoxic T lymphocyte (CTL) mediated destruction. Alleles selective down-regulations are found only in cell lines that maintain the tumor cell phenotype while shift towards a more activated 'B-blast like' phenotype is accompanied by HLA class I up-regulation. A similar pattern of HLA class I expression can be found in a subpopulation of germinal center B cells which express a 'BL like' phenotype. Our findings suggest that the HLA class I expression of BL cells reflects the characteristics of the normal B cell precursor and is probably not the result of immune selection.
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PMID:Cell phenotype dependent expression of MHC class I antigens in Burkitt's lymphoma cell lines. 165 15

Epstein-Barr virus (EBV) infection and Plasmodium falciparum malaria are two known cofactors in the aetiology of endemic Burkitt's lymphoma. To assess the relation between these factors, limiting dilution analysis was used to assess the number of EBV-carrying B cells in the circulation of Gambian children during and after acute malaria. Numbers of virus-carrying cells were five times higher in acute malaria patients and in UK patients with infectious mononucleosis than in convalescent malaria patients and in healthy control adults from the UK. Spontaneous outgrowth in limiting dilution cultures from acute malaria samples was inhibited by acyclovir, a viral DNA polymerase inhibitor. The mechanism of outgrowth, therefore, was virus release from the in-vivo infected cell, which led to infection and immortalisation of co-cultured normal B cells. The findings provide evidence that acute malaria is associated with an increase in the number of EBV-carrying B cells in the circulation. Because of this increase, there is a greater chance of a cytogenetic abnormality occurring in such a cell, with consequent evolution of Burkitt's lymphoma.
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PMID:Circulating Epstein-Barr virus-carrying B cells in acute malaria. 167 68

Eighteen tissue samples from lymphoproliferative lesions and lymphomas in immunodeficiency states were investigated for their content of Epstein-Barr virus (EBV) genome by dot blotting and for the distribution of EBV in tissue sections by in situ hybridization. Fourteen lymphomas from AIDS patients and four children with disorders of the immune system were available. For control reasons, six cases of infectious mononucleosis (IM) and eight Burkitt's lymphomas (BL) from malaria-free regions of Africa were included in the study. Two different patterns of EBV distribution are described: 1) heterogeneous scattered EBV-positive cells, as originally seen in IM and therefore called the IM-type pattern, 2) and a BL-type pattern seen in endemic Burkitt's lymphoma with homogeneous EBV-positive cells all over the tumor. In lymphomas in patients with inborn immunodeficiencies, an IM-type pattern was found. In lymphomas from AIDS patients, the two different patterns were found. There were lymphomas with the IM-type pattern as well as some with the BL-type pattern. In some AIDS-associated lymphomas, both patterns occurred in one tumor. The findings suggest that it is not the disease process that is the distinguishing feature between the two patterns of EBV infection but rather the patient's underlying disease and the extent of this disease.
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PMID:Different Epstein-Barr virus expression in lymphomas from immunocompromised and immunocompetent patients. 169 92


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