Variation between ASP-1 molecules from Ancylostoma caninum in China and the United States

Hookwarm infection continues to be a serious problem in rural areas of Chin a. Rapid reinfection and high cost limit the effectiveness of deworming pro grams. Vaccination offers an attractive alternative to mass chemotherapy. H owever, variation in vaccine antigens from field hookworm populations could conceivably limit efficacy of a vaccine developed from laboratory strains. Reported here are initial experiments to ascertain levels of molecular var iation in a promising vaccine antigen, ASP-I, from the dog hookworm Ancylos toma caninum. ASP-I from a Chinese strain of A. caninum was isolated from a third-stage larval cDNA library and compared to ASP-1 from a U.S. strain. There was 97% and 98% similarity in the DNA and amino acid sequences. respe ctively. There were 42 polymorphic sites between the sequences, 30 of which were synonymous. The 12 nonsynonymous substitutions resulted in 10 changes in the deduced amino acid sequence. Five of the amino acid changes were in the N-terminal domain, whereas the C-terminal domain was more highly conse rved, containing only 2 amino acid changes. The results suggest that the ef fect of molecular variation in antigens from geographically separated paras ite populations should be considered during vaccine development.