Tissue expression of the Schistosoma mansoni 28 kDa glutathione S-transferase

The expression of the Schistosoma mansoni 28 kDa glutathione S-transferase (Sm28) was studied using molecular (PCR, in situ hybridization), and immunocytochemical techniques. The presence of Sm28 was demonstrated in all developmental stages of the parasite except the intra-uterine immature egg. In the parenchyma of male and female adult worms the distribution of Sm28 was limited to a subpopulation of parenchymal cells and to the dorsal tubercles of the male. The tegument, the muscles, the digestive tract, the neural mass, the vitelline glands, and mature gametes were not immunoreactive. Immature germinal cells in both sexes, and the ootype in the female genital system, were found to express Sm28. Deposits of immunoreactive material on host skin following cercarial penetration, exfoliation from the male tubercles, and especially emission of Sm28 from eggs in hepatic granulomas are suspected to be a source of antigen during the parasite infection. The reduction in worm fecundity previously observed in immunization experiments may result from an antibody response directed against Sm28 present in the ootype. There was no cross-reactivity observed, under the experimental conditions used, between the anti-Sm28 sera and either vertebrate or invertebrate host tissue.