Malaria and mosquito gene expression

It has long been known that sexual development of Plasmodium falciparum occurs in the hindgut of the Anopheles gambiae mosquito. However, knowledge regarding the molecular basis of midgut–parasite interaction has been lacking. The identification of genes expressed during invasion and development of the sexual stage could shed light on host–parasite interactions. Furthermore, an understanding of the interactions between parasite and mosquito might also lead to the development of new strategies to interrupt malaria transmission.To this end, a recent study by Bonnet and colleagues1xTranscripts of the malaria vector Anopheles gambiae that are differentially regulated in the midgut upon exposure to invasive stages of Plasmodium falciparum. Bonnet, S. et al. Cell. Microbiol. 2001; 3: 449–458Crossref | PubMed | Scopus (25)See all References1 used differential display to identify mosquito genes expressed during the ingestion of a blood meal. As the in vitro production of gametocytes of P. falciparum is difficult, infection of mosquitoes was carried out in an endemic area of Cameroon, Africa, by experimental feeding on the blood of volunteers known to be infected with P. falciparum. The study focused specifically on the identification of genes differentially expressed in the midgut of mosquitoes fed on either parasite-free blood or on blood of P. falciparum gametocyte or asexual carriers. Five transcripts were identified: four corresponded to genes selectively upregulated by the presence of gametocyte-stage parasites, and one corresponded to a gene overexpressed in the presence of both gametocyte and asexual stages of P. falciparum. Seven additional transcripts were identified in the midgut of An. gambiae after a blood meal containing P. falciparum. Identified transcripts included rRNA genes, trypsin1xTranscripts of the malaria vector Anopheles gambiae that are differentially regulated in the midgut upon exposure to invasive stages of Plasmodium falciparum. Bonnet, S. et al. Cell. Microbiol. 2001; 3: 449–458Crossref | PubMed | Scopus (25)See all References1 and a profilin homolog. Analysis of the other transcripts revealed no known homology to other proteins. This is the first demonstration that ingestion of gametocyte-stage parasites of P. falciparum affects expression of An. gambiae midgut genes in a developmental-stage-dependent manner. The identification of mosquito genes involved in digestion of the blood meal or sexual development of malaria parasites might lead to the development of transgenic mosquitoes that are refractory to these parasites, possibly reducing the transmission of malaria.