Serologic reactivities of the 23-kDa integral membrane proteins of schistosomes.

The 23-kDa integral membrane proteins of Schistosoma mansoni and Schistosoma japonicum (Sm23 and Sj23) are Ag of some interest in terms of both antiparasite vaccination and immunodiagnosis. We have raised an antiserum against a recombinant fusion protein expressing the extracellular hydrophyllic domain of Sm23 (Sm23HD-pGEX) and used this serum, as well as other antibody reagents reacting with Sm/Sj23, in immunochemical analyses. The immunogenicity and antigenicity of Sm23HD-pGEX, and the surprising lack of cross-reactivity between Sm23 and Sj23 support the hypothesis that Sm/Sj23 are host-like molecules with a very limited number of B cell epitopes that are likely to reside in the extracellular hydrophilic domain. We also present evidence that, unlike the highly immunogenic Sj23, Sm23 is not immunogenic in chronically infected mice. Moreover, we confirm a surface location for Sj23 in adult worms, in S. japonicum.