The Laboratory of Malaria and Vector Research (LMVR) in cooperation with scientists at the National School of Medicine, Pharmacy and Odonto-Stomatology (FMPOS) of Mali conducts research at the Malaria Research and Training Center, a component of the NIAID International Center for Excellence in Research (ICER) on the campus of the National School of Medicine of Mali and at the Faculty of Science and Technology in Bamako. The goals of these research programs are several. The primary goal is to develop and sustain a center of research excellence in Africa where the work is planned, directed and executed in close collaboration with African scientists. This goal has been essentially achieved and the MRTC is viewed as a model for research centers in developing countries. A training program for MRTC staff continues to provide much needed expertise in all areas of biology tropical medicine, medical entomology and epidemiology with emphasis on molecular biology and immunology. Since its establishment in 1989, the NIAID has facilitated the graduate training of Malian staff at universities in the US and Europe. The LMVR program has research with Malian doctorates who have received additional PhD degrees at Tulane University (3), The University of Notre Dame (2), the London School of Hygiene and Tropical Medicine (1) and Oxford University (1). Several staff have received doctorates from the University of Bamako in cooperation and training from collaborators from the NIH and several US Universities. The LMVR program in Mali is divided into three main units: malaria pathogenesis and immunology, vector studies and Leishmaniasis. The goals of the malaria pathogenesis/immunology program are: 1) To understand how Malian children with hemoglobin S, alpha-thalassemia, G6PD deficiency, and ABO blood group polymorphisms are protected from both severe and fatal complications of Plasmodium falciparum malaria. 2) To develop a profile of the acquisition of malaria immunity in Malian children that incorporates both antibody responses and CD4+ T cell responses to specific malaria antigens. Results will be correlated with the blood group polymorphisms. 3) To identify the role of specific PfEMP-1 variants in pathogenesis. We will also study the acquisition of responses to PfEMP1 VAR2CSA in the population since this variant has been associated with placental malaria. 4) To investigate the genetic structure of the malaria parasites in this population and assess how this parasite population changes with time and with selective pressures such as drugs. These goals are being accomplished through a clinical study of 1300 children living in 3 villages in Mali, designated the Kenieroba study. Children ranging from 6 months to 18 years of age have been enrolled and are being followed for 5 years. In addition, all children have been typed for a series of hemoglobin and red cell polymorphisms such as HbS. In 2008, nearly 800 cases of malaria were diagnosed in this population and we have already shown that HbS allele provides significant protection against malaria in the population. Parasites from these children are being studied for their ability to adhere to human endothelial cells and moncytes and this is being correlated with the induction of inflammatory responses. A subset of these 1300 children are being studied for their acquired immune responses to specific malaria proteins. Plasma and cells were obtained from children in May prior to the rainy season and in December at the end of the malaria season. We have followed the acquisition of antibodies to a variety of sprozoite and erythrocytic stage malaria proteins. Peripheral blood cells are also being investigated for specific T cell responses to the same antigens. Vector studies encompass a number of areas of mosquito vector biology. 1. A study on dry season ecology was undertaken in a Sahelian village in Mali addressing one of the most enigmatic questions in vector biology: Does An. gambiae survive the dry season by aestivation? Employing a combination of ecological approaches, we could determine that An. gambiae aestivates under natural conditions. 2. A study on longevity of An. gambiae under field conditions has been undertaken in Mali. The specific goals were to assess aging effects on longevity under natural conditions and developing new means to estimate mosquito fitness under natural conditions. Such means are critical needed for studies of disease transmission (e.g., longevity, reproductive output, etc.) and vector control. 3. A study on mating behavior of An. gambiae was undertaken using 3-d night cinematography. These studies are designed to clarify details of mating behavior in swarms and its effects on genetic isolation of the various forms of An. gambiae. The LMVR program on malaria pathogenesis. 4. In cooperation with the President's Malaria Initiative (PMI), we are evaluating a strategy for vector control based on the observation that dry season persistence on An. gambiae in riverine villages provides the basis for reintroduction to inland villages after the start of the rainy season. Control of dry season populations could reduce or eliminate rainy season mosquito populations in inland villages. The LMVR program on Leishmaniasis and its sandfly vectors is designed to describe the essentially unexamined epidemiology of cutaneous Leishmaniasis in Mali. Based at the MRTC and various field sites, this program has examined the epidemiology of the diseases and the ecology of the sandfly vector. The LMVR team determined the baseline prevalence of Leishmania infection using the leishmanin skin test (LST) in Kemena and Sougoula, two villages in Central Mali from which cases of cutaneous leishmaniasis have been recently diagnosed by Mali reference dermatology center in Bamako. LST negative individuals were then re-tested over two consecutive years to estimate the annual incidence of Leishmania infection. The prevalence of Leishmania infection was significantly higher in Kemena than in Sougoula (45.4% vs. 19.9%;OR: 3.36, CI: 2.664.18). The annual incidence of Leishmania infection was also significantly higher in Kemena (18.5% and 17% for 2007 and 2008, respectively) than in Sougoula (5.7% for both years). These data demonstrate that the risk of Leishmania infection was stable in both villages and confirm the initial observation of a significantly higher risk of infection in Kemena (OR: 3.78;CI: 2.456.18 in 2007 and OR: 3.36;CI: 1.955.8 in 2008;P <0.005). The absence of spatial clustering of LST positive individuals in both villages indicated that transmission may be occurring anywhere within the villages. Although Kemena and Sougoula are only 5 km apart and share epidemiologic characteristics such as stable transmission and random distribution of LST positive individuals, they differ markedly in the prevalence and annual incidence of Leishmania infection. Here we establish ongoing transmission of Leishmania in Kemena and Sougoula, Central Mali, and are currently investigating the underlying factors that may be responsible for the discrepant infection rates we observed between them. The second objective is aimed to identify the sand fly salivary proteins that are recognized by antibodies from the inhabitants of Kemena and Sougoula. We have already tested around 1500 sera from these individuals and identified the presence of specific antibodies to the salivary proteins of the sand fly Phlebotomus duboscqi. We are also studying the cellular immune response of these individuals to the saliva of sand flies with the objective of identifying those proteins inducing IFN-gamma, a marker of protection to Leishmaniasis.
Showing the most recent 10 out of 55 publications
