Field testing of Schistosoma japonicum DNA vaccines in cattle in China.

Vaccines are needed to reduce the zoonotic reservoir of Schistosoma japonicum infection in bovines in China. We have developed two experimental DNA vaccines and have already shown these to be capable of inducing partial protection in water buffalo naturally exposed to the risk of S. japonicum infection in the field. We now report a similar field trial in cattle, the other major bovine reservoir host species in China. Groups of cattle were vaccinated with the VRSj28 vaccine or the VRSj23 vaccine, or, to test whether protection could be enhanced by combination vaccination, with both these DNA vaccines together. After vaccination, the cattle were exposed to natural infection in the field for a period of 54 days. Worm and egg counts carried out at the end of the experiment showed that each of the vaccine groups showed partial resistance, and that combined vaccination was not more effective than vaccination with the individual plasmids.

Cloning of Schistosoma japonicum Chinese Strain TPI Gene and Characterization of Its Expression Product in Escherichia coli.

Triose-phosphate isomerase is an important candidate for schistosoma antigens. An 800 bp DNA fragment was amplified by RT-PCR from adult Schistosoma japonicum mRNA. Sequence analysis revealed that this fragment contained S. japonicum (Chinese strain) triose-phosphate isomerase gene. Then this gene was cloned into the expression vector pGEX-4T and subsequently expressed in E. coli. The recombinant GST-fusion protein was purified by glutathione agarose affinity chromatography. Its molecular weight was determined to be 54 kD. The yield of expression was around 30 mg/L E. coli culture. Western blotting showed that the recombinant protein had good antigenicity which could be helpful for the making of anti-S. japonicum multi-valent recombinant vaccine.

Cloning of Schistosoma japonicum Chinese Strain Fatty Acid Binding Protein (Sj-FABPc) Gene and Its Overproduction in Escherichia coli.

A 600 bp DNA fragment was amplified by PCR, from an adult Schistosoma japonicum cDNA library. Sequence analysis revealed that this fragment containedthe S. japonicum Chinese Mainland strain fatty acid binding protein (Sj-14FABPc) gene. This gene was then cloned into the expression vector pGEX-2T, and subsequently expressed in Escherichia coli. The recombinant GST-fusion protein could be purified by glutathione agarose affinity chromatography. Its molecular weight was about 41 kD. The yield of expression was around 25 mg/L E. coli culture. The immunological test suggested that the recombinant protein had good antigenicity, and could be developed into a new vaccine molecule of S. japonicum.

Studies on the Expression of the 28 kD Glutathione S-transferase Gene from Schistosoma japonicum in the Silkworm (Bombyx mori) Larvae and Insect Cells.

The gene of the 28 kD glutathione S-transferase (GST) from the Chinese strain of Schistosoma japonicum had been expressed in the silkworm (Bombyx mori) cells and larvae by Bombyx mori nuclear polyhedrosis virus (BmNPV) vector which had been modified. The GST gene was inserted into the right position of the BmNPV genome as identified by Southern hybridization. The product was a 28 kD protein, had GST activity and antigenicity. The yield in BmN cells (1x10(6) cells/ml) was 0.77 mg and more than 5 mg in a silkworm larvae. All the results showed that it is possible to develop the GST expressed in the silkworm larvae to a new kind of genetic engineered schistosomiasis vaccine.