Expression and bioactivity analysis of staphylococcal enterotoxin G and staphylococcal enterotoxin I

The filtrate of Staphylococcus aureus culture, named staphylococcal enterotoxin C injection, has been used for 10 years in China. SEC2 has been claimed to be the only staphylococcal enterotoxins (SEs) without certifiable evidence.

To present an efficient procedure for the expression and purification of recombinant proteins SEG and SEI, from S. aureus.

In present work, we extracted total DNA from S. aureus (FRI 1230) and the recombinant proteins of SEG and SEI were then cloned, expressed and purified using E. coli. Splenic lymphocytes were used as effector cells and K562 and B16 cells were used as target cells to evaluate the inhibitory and stimulatory abilities of purified rSEG and rSEI on in vitro proliferation.

The size of amplified products of SEG and SEI genes were found to be about 400 and 467 bp, respectively. pGEX-SEG and pGEX-SEI were constructed successfully. SEG and SEI were demonstrated to be active stimulators of T-cell proliferation; moreover, they inhibited the proliferation of K562 cells and B16 cells.

The current findings suggest that SEC2 might not be the only active component of staphylococcal enterotoxin C injection and may involve other essential proteins like SEG and SEI in its clinical efficacy.

This efficient procedure for the expression and purification of SEG and SEI and may be useful for mass production of therapeutically important proteins. In the future, proteins acting as active stimulators of T-cell proliferation may help in developing effective cancer therapy.