Effect of anti-mosquito midgut antibodies on development of malaria parasite, Plasmodium vivax and fecundity in vector mosquito Anopheles culicifacies (Diptera: culicidae).

The effect of anti-mosquito-midgut antibodies on the development of the malaria parasite, P.vivax was studied by feeding the vector mosquito, An. culicifacies with infected blood supplemented with serum from immunized rabbits. In order to get antisera, rabbits were immunized with midgut proteins of three siblings species of Anopheles culicifacies, reported to exhibit differential vectorial capacity.  The mosquitoes that ingested anti-midgut antibodies along with infectious parasites had significantly fewer oocysts compared to the control group of mosquitoes. The immunized rabbits generated high titer of antibodies. Their cross reactivity amongst various tissues of the same species and with other sibling species was also determined. Immunogenic polypeptides expressed in the midgut of glucose or blood fed An. culicifacies sibling species were identified by Western blotting. One immunogenic polypeptide of 62 kDa was exclusively present in the midgut of species A. Similarly, three polypeptides of 97, 94 and 58 kDa and one polypeptide of 23 kDa were present exclusively in species B and C respectively. Immunoelectron microscopy revealed the localization of these antigens on baso-lateral membrane and microvilli. The effects of anti-mosquito midgut antibodies on fecundity, longevity, mortality and engorgement of mosquitoes were studied. Fecundity was also reduced significantly. These observations open an avenue for research toward the development of a vector-based malaria parasite transmission-blocking vaccine.

Monoclonal antibodies AC-43 and AC-29 disrupt Plasmodium vivax development in the Indian malaria vector Anopheles culicifacies (Diptera: culicidae).

A repertoire of monoclonal antibodies (mAbs) was generated against the midgut proteins of Anopheles culicifacies mosquitoes. The mAbs AC-43 and AC-29 signifi cantly inhibited Plasmodium vivax development inside the mosquito midgut. The number of oocysts that developed was reduced by 78.6% when mosquitoes ingested a combination of these two mAbs along with the blood meal. AC-43 mAb binds to the epitope common in 97, 80 and 43 kDa polypeptides from the midgut protein extract, as indicated by western blot analysis. Similarly, the mAb AC-29 recognized 52, 44, 40 and 29 kDa polypeptides. These female midgut-specifi c polypeptides are shared between An. culicifacies and An. stephensi, two major vectors of malaria in India. Deglycosylation assays revealed that O-linked carbohydrates are the major components in epitopes corresponding to AC-43 and AC-29. Gold particle labelling revealed that both these mAbs preferentially bind to glycoproteins at the apical microvilli and the microvillus-associated network present inside transverse sections of the gut epithelium. These regions are particularly known to have receptors for ookinetes, which enable them to cross this epithelial barrier and provide them with certain necessary chemicals or components for further development into oocysts. Therefore, these glycoproteins appear to be potential candidates for a vectordirected transmission-blocking vaccine (TBV).