Molecular cloning and characterization of a novel Schistosoma japonicum "irradiated vaccine-specific" antigen, Sj14-3-3

A Schistosoma japonicum cDNA coding for a full length S. japonicum 14-3-3 p rotein was obtained by antibody screening of an adult worm cDNA library usi ng sera taken from mice vaccinated with UV-attenuated cercariae, which are capable of transferring high levels of passive immunity to this parasite. T he deduced amino acid sequence consists of 254 amino acids and is highly ho mologous with 14-3-3 family of proteins from a variety of species (55-69% i dentity). The recombinant S. japonicum 14-3-3 protein (rSj14-3-3) was expre ssed and purified in pGEX/E. coli, and in Western blotting was strongly rec ognised by sera from mice, rats and bovines vaccinated with irradiated S. j aponicum cercariae, Analysis of mRNA showed that Sj14-3-3 is expressed in s porocysts and adult worms, but not in cercariae, however mouse antisera aga inst rSj14-3-3 recognised a 29 kDa native antigen in antigen preparations m ade from eggs, cercariae, schistosomula and adult worms of S. japonicum ind icating that this antigen is present in all life-cycle stages. The presence of the native antigen in detergent extracts of intact schistosomula sugges ts that it is also present in the schistosomular tegument which is the most vulnerable target for immune attack. However, antisera against rSj14-3-3 d id not recognise a similar band in S. mansoni or S. haematobium antigens, i ndicating that, like the W-attenuated vaccines, this protein induced specie s-specific immune responses. Southern blot analysis suggested that there ma y exist more than one gene copy and/or polymorphism for Sj14-3-3. Immunoele ctron microscopy confirmed that the native antigen is present throughout th e body of adult worms including the tegument, but is less abundant in the m uscles. The potential of rSj14-3-3 as a vaccine is now under further invest igation. (C) 1999 Elsevier Science B.V. All rights reserved.