Staphylococcus
enterotoxin A (SEA) stimulates T cells bearing certain TCR beta-chain variable regions, when bound to
MHC-II molecules, and is a potent inducer of CTL activity and
cytokines production. To decrease toxicity of SEA to the normal MHC-II(+) cells and to localize the immune response induced by SEA to the
tumor site, my colleague previously genetically fused SEA with B7.1 transmembrane region (named as SEAtm) to make SEA express on the surface of
tumor cells and
tumor cells modified with SEAtm could induce efficient antitumor immunity in vitro. The
tumor cell
vaccines modified with multiple immune activators frequently elicited stronger antitumor immune responses than single-modified
vaccines. In this study, we modified the
tumor cell
vaccine with B7.1 and SEAtm to improve efficiency in the application of SEA. First, SEAtm gene was subcloned from recombinant plasmid pLXSNSEP by PCR and murine B7.1 gene was cloned from splenocytes derived from C57BL/6 mice by RT-PCR. Then, the eukaryotic co-expression vector of SEA and murine B7.1 gene was constructed and named as pcDNA-BIS. B16 cell lines stably expressing SEA and/or B7.1 were established by screening with
G418 after transfection and inactivated for the preparation of
tumor cell
vaccines to treat mice bearing established B16
tumors. The results indicated that the dual-modified
tumor cell
vaccine B16/B7.1+SEAtm (B16-BIS) elicited significantly stronger antitumor immune responses in vivo when compared with the single-modified
tumor cell
vaccines B16/B7.1 (B16-B7.1) and B16/SEAtm (B16-SEAtm), and supported the feasibility and effectiveness of the dual-modified
tumor cell
vaccine with
superantigen and co-stimulatory molecule.