Immunogenicity of Sm32 synthetic peptides derived from the Schistosoma mansoni adult worm

The previously called “hemoglobinase” Sm32 molecule of the adult worm of Schistosoma mansoni was chemically synthesized in 22 polymeric peptides based on the t-boc strategy. Their immunogenicity was evaluated in rabbits to which a mixture of five to six peptides of 20 amino acids long were given in three doses with Freund's adjuvant. Seventeen peptides were found to be immunogenic, and sera from immunized rabbits corresponding to the molecule from the first 335 amino acids, recognized the 32 kDa native protein from the adult worm antigen by western blot. Of those, the relevant peptides responsible of the recognition of the original molecule corresponded to amino acids 101–120, 121–140 and 244–268, based on inhibition competitive assays. Because Sm32 is one of the excretory and secretory molecules released with the vomitus of the adult worm, it is one of the target antigens for detection in plasma of infected individuals. The production of these polyclonal monospecific antibodies against the synthetic peptides could be of value in the immunodiagnosis of this parasitosis.