Molecular characterization of a 20.8-kDa Schistosoma mansoni antigen: Sequence similarity to tegumental associated antigens and dynein light chains

Survival of Schistosoma mansoni within the infected host requires the parasite to actively maintain its protective tegument. The components responsible for this maintenance are therefore attractive targets for immunoprophylaxis or chemotherapy. Here we report the molecular characterization of a 20.8-kDa tegumental antigen with sequence similarity to dynein light chains and tegumental associated antigens. A cDNA encoding the 20.8-kDa polypeptide contains an open reading frame of 181 amino acids and predicts an isoelectric point of 7.27. Expression of the 20.8-kDa antigen is developmentally regulated, with the highest concentration found in cercariae. Our data show that the 20.8-kDa polypeptide specifically interacts with a S. mansoni 10.4-kDa dynein light chain that we have previously described (Hoffmann, K. F., and Strand, M. (1996) J. Biol. Chem. 271, 26117-26123). Velocity sedimentation analysis of a parasite extract demonstrated that this 10.4-kDa dynein light chain and the 20.8-kDa polypeptide were present in a complex that sedimented at 4.4 Svedberg units. We have also shown by antibody cross-reactivity that a 20.8-kDa homolog of the S. mansoni antigen is present in Schistosoma japonicum, but not in Schistosoma hematobium or Fasciola hepatica. Because the 20.8-kDa polypeptide displays ideal characteristics of a potential vaccine candidate, including (i) expression in the tegument, (ii) significant divergence from mammalian brain cytoplasmic dynein, and (iii) a conserved homolog in S. japonicum, we are currently evaluating its immunoprophylactic efficacy.