Anopheles gambiae salivary proteins: markers of exposure to bites of anopheline mosquitoes?

The saliva of adult female mosquitoes carries a cocktail of bioactive compounds whose function is to restrain potentially harmful responses of the vertebrate host such as hemostasis, inflammation and immunity. However, the salivary proteins injected at the feeding site also act as antigens eliciting an immune response with potentially interesting implications. It has been suggested that human antibody response against Anopheles saliva may represent a measure of exposure to bites of anopheline mosquitoes, and therefore a potential marker of malaria risk. However, mosquito saliva is a complex mixture: thus, cross-reactivity to salivary antigens found in other mosquitoes (Aedes and/or Culex) or in other blood-sucking arthropods may be misleading. In the framework of a more general effort of understanding the role of mosquito salivary proteins in parasite-vector-host interactions we are trying to identify immunogenic salivary proteins that are only found in Anopheles and may be used as sensitive and specific markers of exposure to bites of anopheline mosquitoes. Toward this direction we have expressed gSG6, a small female-specific salivary protein that is only found in Anopheles species. Silencing by RNA interference indicated an involvement in blood-feeding but the specific function of this protein remained so far elusive. Development of an ELISA assay to evaluate anti-gSG6 IgG serum levels in exposed individuals from Burkina Faso is in progress.