Interactions between Asaia, Plasmodium and Anopheles: new insights in mosquito symbiosis and implications in Malaria Symbiotic Control

The recent identification of acetic acid bacteria belonging to the genus Asaia, that are stably associated with larvae and adults of different species of malaria transmitting mosquitoes, in particular Anopheles stephensi, indicates this bacterium as a suitable candidate for the paratransgenic or symbiotic control of the malaria infection. The presence of Asaia in the mosquito reproductive system represents an additional intriguing feature, particularly important towards the development of Paratransgenetically Modified (PM) mosquitoes that can mix with natural populations. By the means of Real Time quantitative PCR I have investigated the relative amount of Asaia and Plasmodium in co-infected mosquitoes thus providing evidence that the malaria infection does not interfere with the blooming of Asaia that follows a blood meal. Furthermore, by immunological studies we provided evidences that Asaia induces ‘in vitro' the expression of antimicrobial peptides (AMPs) in the mosquito and that, the adaptation of Asaia to the life into the insect, doesn't appear to be related with a reduced immunogenicity, but with a resistance to the immune reaction. In addition, by fluorescent recombinant strains of both Asaia and Plasmodium, we were able to precisely define the co-localisation of these organisms at the level of mosquito midgut and salivary glands. It was also considered necessary to verify the Asaia role about the vitality of adults mosquitoes. For this aim, has been adopted a novel strategy using monoclonal antibodies against Asaia, to interfere with the function of these bacteria by antibody opsonization. These studies while confirming the potential suitable use of Asaia as microbial agent for the paratransgenic control of malaria infection. Beyond bacteria, yeast-like organisms were also present in the mosquito midgut and in reproductive systems. We have identified Wickerhamomyces anomalus (Saccharomycetales) as an important component of the yeast microbiome in this mosquito species, suggesting multiple transmission patterns. The possibility to easily manipulate yeast, and the chance to express effector molecules in a eukaryotic organism renders W. anomalus another good potential candidate for paratransgenesis.