This project deals with both the laboratory and clinical aspects of infection caused by the intestinal nematode, Strongyloides stercoralis. The laboratory research involves analysis and characterization of parasite antigens. The clinical studies focus upon the immune response of infected individuals, and factors that influence the immune response. A cDNA library was made in lambdalgt II phage expression vector from mRNA extracted from third stage larvae of S. stercoralis. Two clones were identified which reacted with antibodies from a pool of patients' serum infected with the parasite. Recombinant material expressed by the clones in E coli reacted by Western blot to both IgG and IgE from most individual sera of infected patients. Attempts are under way to express the clones in another vector to obtain better sequence data, and more clones will be sought from the cDNA library. In one of the main clinical studies during the past year, the efficacy of Ivermectin was compared to that of the standard treatment with thiabendazole in a group of 53 Cambodian refugees now living in Lowell, Massachusetts. Only one treatment failure occurred in 18 thiabendazole- treated patients, and one failure in 35 Ivermctin-treated cases. Ivermectin was very well tolerated, but side effects were frequent with thiabendazole. The association of persistent strongyloides infection with HTLV-1 is still under investigation.