EVALUATION OF RECOMBINANT CHITINASE AND SXP1 ANTIGENS AS ANTIMICROFILARIAL VACCINES

Prior studies indicate that a microfilarial stage-specific chitinase i s a possible candidate antigen for a transmission-blocking vaccine aga inst Brugian filariasis. The antigen is a functional enzyme that progr essively appears as microfilariae mature and become able to infect and develop in a susceptible mosquito vector. It is recognized by a monoc lonal antibody that reduces microfilaremia in infected animals and by a subset of sera from infected persons who remain amicrofilaremic. Imm unization of jirds with recombinant chitinase induced partial protecti on against microfilaremia resulting from subsequent infection with Bru gia malayi, but did not reduce adult worm burdens, Vaccination was muc h less effective when administered during the prepatent stage of infec tion and was ineffective when given to microfilaremic jirds. The prote ctive epitope appears to be located close to the carboxy terminus of t he chitinase molecule, Immunization of jirds with SXP1, an antigen pre sent in multiple worm stages, also reduced microfilaremia and, in some experiments, adult worm burdens, bur hyperimmunization with a recombi nant filarial myosin was not protective. These observations indicate t hat the relative timing-of immunization and infection is an important factor in the efficacy of antimicrofilarial vaccines.