Immunoprophylaxis against filarial parasite,Brugia malayi: potential of excretory-secretory antigens in inducing immunity

The role of excretory-secretory antigens in inducing immunity in the host againstBrugia malayi microfilariae and infective larvae was studied byin vitro antibody dependent cell-mediated reaction as well asin vivo inoculation of filarial parasites within a microchamber in the host. The immune sera of jirds raised againstBrugia malayi microfilarial and infective larval excretory-secretory antigens(Bm Mf ESA andBm L₃ ESA) promoted the adherence of peritoneal exudate cells toBrugia malayi microfilariae and infective larvaein vitro and induced cytotoxicity to the parasites within 48 h. The antiBm Mf ESA serum was more effective than antiBm L3 ESA serum in inducing cytotoxicity to microfilariae and both antisera had a similar cytotoxic effect on infective larvae. In the microchambers implanted in the immune jirds, host cells could migrate and adhere to the microfilariae and infective larvae and kill them within 48–72 h. Further,Mastomys natalensis immunized againstBm Mf ESA and L₃ ESA generated a high degree of protective response against circulating microfilariae. These results suggest that excretory-secretory antigens are effective in inducing resistance against filarial parasites and thus have potential in immunoprophylaxis.