Variation in maxadilan and its consequences
Maxadilan is a potent vsodilatory protein in the saliva of the sand fly, Lutzomyia longipalpis . Our observation that maxadilan is highly polymorphic was surprising. It would seem that the amino acid sequence of such a protein, with functions presumably vital to the sand fly, would be conserved. We hypothesize that hyper-variation in maxadilan has evolved as a mechanism for the avoidance of host immune response mounted against it. To test this hypothesis we propose studies aimed at determining amino acid sequence polymorphism in maxadilan from Lu. longipalpis (Aim #1). Population genetics studies will be conducted at field sites in Colombia , Nicaragua and Brazil . If variation in maxadilan does represent antigenic polymorphism and is adaptive, then it must be true that anti-maxadilan antibodies have a negative effect on vector fitness. In Aim #2 we propose a series of experiments to test this hypothesis. We will immunize hamsters with recombinant maxadilan. Flies will be fed on immunized and control animals and effects on sand fly fitness evaluated. In Aim #3 we will examine the impact of maxadilan on leishmanial infections. There is compelling evidence that the immunomodulatory activities of sand fly saliva, and maxadilan itself, enhances the establishment of parasite infections. The effects of vector saliva and specific maxadilan proteins on the pathogenesis of Leishmania chagasi will be evaluated by experimental infections (Aim #3). We have discovered that natural Lu. longipalpis populations differ dramatically in the amount of maxadilan present in their saliva. As part of Aim #3 we will conduct epidemiological field studies to determine the distribution of “high” and “low” maxadilan fly populations in relation to the distribution of visceral or atypical cutaneous disease caused by Le. chagasi . In Aim #4, we will study immunological specificity of maxadilan variants. The goal of these experiments is to determine if different maxadilan proteins illicit specific antibodies and to evaluate if these cross react (antigenic specificity).Population genomics of the mosquito An. gambiae in Africa
Malaria control strategies based on genetic manipulation of vectors will require extensive knowledge of vector population genetics. Critical information includes: population size, patterns of gene flow, the breeding structure of populations and the effects of natural selection on individual gene loci. The overall goal of the proposed research is to provide such a background. We propose to address these questions by: (1) Characterizing spatial variation in the genetic structure of populations of Anopheles gambiae in continental Africa by determining the distribution of chromosomal and molecular polymorphisms. Representative locations will be studied in two countries: Mali in West Africa and Cameroon in Central Africa . The genetic markers we will use include chromosome arrangements, microsatellite DNA loci, and mitochondrial DNA loci. (2) Identifying physical/ecological features and relate these to spatial varoiation in population genetic structure, patterns of gene flow, and as selective forces on individual loci. Migration rates among sites will be established by measuring their genetic similarity, then inferring how much gene flow is required to maintain such observed similarity. Based on this information we will employ a GIS-based procedure termed "Wombling", which will identify areas with high and low levels of gene flow. These will be then be correlated with ecological features determined on the ground and from remote imaging. In this manner ecological features associated with high and low population densities, and also with high and low levels of gene flow can thus be identified. Such information should be helpful to vector control efforts that require an understanding of dispersal and gene flow, including genetic control and insecticide resistance management. The effects of natural selection on individual loci and segregating sites within loci will be studied by taking a population genomics approach. This approach provides the means to study the behavior of individual functional genes in nature, bridging the gap between population genetics and molecular biology. For more information phone (530) 752-5652 or e-mail gclanzaro@ucdavis.edu.