In spite of research efforts to develop vaccines against the causative agent of 
human malaria, Plasmodium falciparum, effective control remains elusive. The 
predominant vaccine strategy focuses on targeting parasite blood stages in the 
vertebrate host. An alternative approach has been the development of 
transmission-blocking vaccines (TBVs). TBVs target antigens on parasite sexual 
stages that persist within the insect vector, anopheline mosquitoes, or target 
mosquito midgut proteins that are presumed to mediate parasite development. By 
blocking parasite development within the insect vector, TBVs effectively disrupt 
transmission and the resultant cascade of secondary infections. Using a mosquito 
midgut-specific mouse monoclonal antibody (MG96), we have partially 
characterized membrane-bound midgut glycoproteins in Anopheles gambiae and 
Anopheles stephensi. These proteins are present on the microvilli of midgut 
epithelial cells in both blood-fed and unfed mosquitoes, suggesting that the 
expression of the protein is not induced as a result of blood feeding. MG96 
exhibits a dose-dependent blocking effect against Plasmodium yoelii development 
in An. stephensi. We achieved 100% blocking of parasite development in the 
mosquito midgut. Preliminary deglycosylation assays indicate that the epitope 
recognized by MG96 is a complex oligosaccharide. Future investigation of the 
carbohydrate epitope as well as gene identification should provide valuable 
insight into the possible mechanisms of ookinete attachment and invasion of 
mosquito midgut epithelial cells.