T-cell proliferation and antitumour activities of a truncated mutant of staphylococcal enterotoxin 02 with decreased cytokine secretion

As a superantigen, staphylococcal enterotoxin C2 (SEC2) has commonly been used as an antitumour immunotherapy agent in China. However, the clinical application of SEC2 has been hampered by its pyrogenic toxicity and the presence of neutralizing antibody in patients. Thus, an improvement in its superantigen-based immunotherapy is highly needed. In this study, a truncated SEC2 mutant, SEC(14-128), was constructed without the N-terminal 13 and C-terminal 111 aa. This mutant retained T-cell proliferation and antitumour activities in in vitro experiments. However, it induced a significantly decreased release of the main inflammatory cytokines inerleukin-2 and gamma interferon. Moreover, SEC(14-128) exhibited reduced toxicity and affinity to anti-SEC2 IgG compared with native SEC2. Based on the considerable antitumour activity and low toxicity, it is proposed that the mutant SEC(14-128) could be a potential candidate for cancer treatment.