PLASMODIUM-GALLINACEUM - SPOROZOITE INVASION OF AEDES-AEGYPTI SALIVARY-GLANDS IS INHIBITED BY ANTI-GLAND ANTIBODIES AND BY LECTINS

There is evidence which suggests that malaria sporozoites recognize mo squito salivary glands by specific receptor-ligand interactions. We ar e interested in identifying the putative salivary gland receptor(s) fo r sporozoite invasion. We used an in vivo bioassay for sporozoite inva sion of salivary glands. In this assay, purified sporozoites from matu re oocysts of Plasmodium gallinaceum were injected into Aedes aegypti mosquitoes and salivary glands were dissected at different time points after injection. One half of the maximum invasion of salivary glands by sporozoites occurred by 6 hr, and salivary gland sporozoite load di d not increase further after 24 hr postinjection. This assay was used to determine the effect of experimental treatments with antibodies and lectins at 24 hr postinjection. We raised a rabbit polyclonal antiser um against female Ae. aegypti salivary glands which recognized tissue- specific determinants in the basal lamina of salivary glands. Purified IgG antibody fraction of the immune serum blocked sporozoite invasion in vivo. We tested a panel of 19 lectins and found 7 which bound to s alivary glands. Of these 7, succinylated wheat germ agglutinin and whe at germ agglutinin completely blocked sporozoite invasion; Pisum sativ um agglutinin and soybean agglutinin partially blocked; and concanaval in A, Dolichos biflorus agglutinin, and Phaseolus vulgaris erythroaggl utinin did not block. Our results suggest that sporozoites interact wi th glycosylated salivary gland surface molecules which serve as recept ors for invasion, and which may be in the salivary,oland basal lamina. Because the putative sporozoite receptors contain immunogenic determi nants, it is feasible to identify them by an immunological strategy. ( C) 1995 Academic Press, Inc.