Genes identified by an expression screen of the vector mosquito Anopheles gambiae display differential molecular immune response to malaria parasitesand bacteria

We performed a gene expression screen of the entire transcriptome of the ma jor African malaria vector Anopheles gambiae for immune response genes in a dult female mosquitoes, which is the developmental stage infected by malari a parasites. Mosquitoes were immune-stimulated for subtractive cloning by t reatment with bacterial lipopolysaccharide. a potent and general elicitor o f the innate immune response, and by injury. The screen yielded a highly en riched cDNA library in which more than half of the clones were immune respo nsive. In this paper, we describe 23 immune-regulated genes, including puta tive protease inhibitors, serine proteases, regulatory molecules, and a num ber of genes without known relatives. A molecule related to the protease in hibitor alpha-2-macroglobulin responded strongly to malaria parasite infect ion, but displayed little or no response to bacteria, whereas other genes e xhibited the inverse pattern. These results indicate that the insect immune system discriminates between molecular signals specific to infection with bacteria and malaria parasites.