Despite recent advances in vector control and antifilarial drug development, human infection with the filarial parasites, Wuchereria bancrofti (Wb) and Loa Ioa (LI), remains a major cause of morbidity worldwide. While there is no direct proof that protective immunity exists in humans, the presence of populations of long-term residents of endemic areas who are both amicrofilaremic and without clinical manifestations of disease suggests that such immunity may develop in some individuals. These "putatively immune" individuals demonstrate both a cellular and humoral hyperresponsiveness to crude filarial antigens. Since vigorous responses to microfilariae and adult parasites have been associated with the pathophysiology seen in these infections, the infective larval stage appears a more promising target for protective immunity. To circumvent the lack of available parasite material, we plan to screen filarial larval cDNA libraries with sera from "putatively immune" individuals from two filaria-endemic areas in Benin, West Africa. Fusion products from recombinant clones selected in this manner will be assessed for their ability to stimulate T cell proliferation in these same individuals, and clones that remain of interest will be characterized further with respect to their nucleic acid and amino acid sequences, stage specificity and localization in the native parasite.