PLASMODIUM ACTIVATES THE INNATE IMMUNE-RESPONSE OF ANOPHELES-GAMBIAE MOSQUITOS

Innate immune-related gene expression in the major disease vector mosq uito Anopheles gambiae has been analyzed following infection by the ma laria parasite, Plasmodium berghei. Substantially increased levels of mRNAs encoding the antibacterial peptide defensin and a putative Gram- negative bacteria-binding protein (GNBP) are observed 20-30 h after in gestion of an infected blood-meal, at a time which indicates that this induction is a response to parasite invasion of the midgut: epitheliu m. The induction is dependent upon the ingestion of infective, sexual- stage parasites, and is not due to opportunistic co-penetration of res ident gut micro-organisms into the hemocoel, The response is activated following infection both locally (in the midgut) and systemically (in remaining tissues, presumably fat body and/or hemocytes), The observa tion that Plasmodium can trigger a molecularly defined immune response in the vector constitutes an important advance in our understanding o f parasite-vector interactions that are potentially involved in malari a transmission, and extends knowledge of the innate immune system of i nsects to encompass responses to protozoan parasites.