[Protective immunity of the recombinant Schistosoma japonicum specific very low density lipoprotein binding protein as a vaccine candidate].

OBJECTIVE: To investigate the protective immunity against Schistosoma japonicum in mice immunized with recombinant specific very low density lipoprotein binding protein (SVLBP) and its potential as vaccine candidate. METHODS: Recombinant SVLBP antigen was over-expressed under IPTG induction and purified by Ni-NTA affinity chromatography. C57BL/6 mice were immunized three times with purified reSVLBP complexed with Freund's adjuvant, at biweekly intervals. Then 35+/-1 cercariae of S. japonicum were given to each mouse by abdominal skin 10 days after the 3rd immunization. 45 days later, all mice were sacrificed to collect adult worms and count liver eggs. serum samples were collected before immunization and after challenge respectively, and were probed the antigen-specific antibodies using a panel of ELISAs. RESULTS: The worm burden and the egg deposition in liver tissue were reduced by 33.4% and 47.6% respectively in the immunized group, in comparison with the adjuvant control group (P<0.05). Higher titer (>1:6 400) of total IgG was observed after challenge infection. The vaccinated mice developed significantly higher levels of IgG2a, IgG2b, IgG1 than those of control mice. CONCLUSION: The recombinant tegumental SVLBP antigen could induce partial protection against S. japonicum infection. These data demonstrate the potential of SVLBP as a schistosome vaccine candidate.

High-level expression and secretion of recombinant mouse endostatin by Escherichia coli.

The expression of murine endostatin was achieved by placing its gene downstream of an alkaline phosphatase gene (phoA) promoter. To ensure proper folding and secretion of the recombinant protein, the mouse endostatin was fused with alkaline phosphatase signal peptide. SDS/polyacrylamide gel electrophoresis analysis of the culture medium of recombinant Escherichia coli cells revealed that endostatin was efficiently secreted. The signal peptide was efficiently cleaved during secretion as demonstrated by N-terminal amino acid sequencing. The maximum yield of secreted endostatin during fermentation was 40 mg/liter. Up to 28 mg of endostatin was purified from 1 liter of cell culture broth. The biological activity of recombinant protein was tested in a bovine aortic endothelial (BAE) cell proliferation assay. The recombinant endostatin inhibited the growth of BAE cells stimulated by basic fibroblast growth factor, and its ED50 was comparable to that from a previous report. Flow cytometric measurements of BAE cells cultivated in medium with endostatin demonstrated a cell cycle arrest mainly in the G0/G1 phase and a decrease in the S phase.