Cloning, expression and immunization of the new antigen gene Sj-Ts4 of Schistosoma japonicum.

In order to explore the molecular mechanism of high immune protection against schistosomes infection in animals infected with Trichinella spiralis, and to provide several cross-protective antigen genes for developing anti-schistosomiasis vaccine, a Schistosoma japonicum adult worm cDNA library was immunoscreened using sera taken from mice infected with Trichinella spiralis. Nine positive clones were obtained after 3 rounds of immunoscreening. Among them, Sj-Ts4 represents a novel gene of S. japonicum, which coding for a novel protein of 210 amino acids. The protein has a deduced molecular mass of 23 kD and isoelectric point of 7.72. Sj-Ts4 was expressed as a glutathione-S-transferase (GST) fusion protein by cloning into the prokaryotic expression vector pGEX-5X-3. The recombinant Sj-Ts4 protein (rSj-Ts4) was purified and could be recognized by sera of mice infected with S.japonicum. Vaccination of several groups of mice with rSj-Ts4 or rSj-Ts4 incorporated into Freund's complete adjuvant induced high titers of specific IgG antibodies. Two vaccination groups all obtained significant reduction in worm burden (31.36%, 36.80%, P<0.01), compared with the control groups.