[Prokaryotic expression and immunization of glutamyl tRNA synthetase of Streptococcus suis]

Glutamyl tRNA Synthetase (Gts) is a protease which catalyzes esterification between tRNA and glutamine. The immunogenicity of Gts was evaluated through immunization and challenge experiment.

We cloned gts from the genome of SC19, and inserted it into prokaryotic expression plasmid pET28a-gts. The recombinant vector was transformed into E. coli BL21. Induced by IPTG, one 58 kD protein, was expressed and purified by using Ni - NTA column (Novagen). The purity of rGtS was 93.3% and the concentration of purified protein was 433 microg/mL. We proved the immunogenicity of recombinant protein rGtS by western blot analysis. We immunized Balb/c mice with rGtS and Freund's adjuvant, and after two boost vaccinations, all mice were challenged with 4 times LD50 amount of SC19 (1.2 x 10(9) CFU). The survive rate of vaccination group is 50% (4/8), significantly higher than blank vector control group (1/8).

These results proved that GtS has certain immunogenicity and can offer partial protection against high dose challenge. Therefore Gts could be a potential candidate of subunit vaccine against Streptococcus suis.