PROTEOLYTIC-ENZYME ACTIVITY AND PLASMODIUM-FALCIPARUM SPOROGONIC DEVELOPMENT IN 3 SPECIES OF ANOPHELES MOSQUITOS

If proteolytic enzymes affect the innate vector competence of Anophele s mosquitoes for Plasmodium infections, then mechanistic effects shoul d be most pronounced at the zygote to ookinete developmental transitio n. Anopheles freeborni, Anopheles gambiae, and Anopheles albimanus exh ibit excellent, good, and poor susceptibility to P. falciparum, respec tively. Aminopeptidase and trypsin activity were determined relative t o the kinetics of P. falciparum ookinete development in these 3 Anophe les species. Ookinetes in A. freeborni, A, gambiae, and A, albimanus w ere first observed at 18 hr postinfection. For separate infection expe riments, peak parasite densities were observed at either 18, 24, or 30 hr for A. albimanus, at 24 or 30 hr for A. freeborni, and at either 2 4, 30, or 36 hr for A. gambiae. Although the 3 species supported ookin ete development equally, they had significantly different oocyst infec tion rates. Similar patterns of aminopeptidase activity were observed for the most susceptible species, A. freeborni, and the least suscepti ble species, A. albimanus. Anopheles gambiae had the lowest levels of aminopeptidase. Anopheles freeborni also had higher levels of trypsin activity than either A. albimanus or A. gambiae. Irrespective of diffe rences in innate vector competence, the 3 species showed peak levels o f aminopeptidase and trypsin that were coincident with peak ookinete d ensities. Thus, the close correspondence between the kinetics of ookin etes and enzymes associated with bloodmeal digestion indicates that pr oteolytic enzymes alone do not limit the early stages of sporogonic de velopment in vector species ofAnopheles.