Adjuvant activity of GP96 C-terminal domain towards Her2eu DNA vaccine is fusion direction-dependent

摘要

The Her2 is one of tumor-associated antigens (TAA), regarded as an ideal target of immunotherapy. DNA encoding full-length or truncated rat Her2eu have shown protective and therapeutics potentials against Her2eu-expressing mammary tumors. However, the efficacy of active vaccination is limited since Her2 is a self-tolerated antigen. Hence, new strategies are required to enhance both the quality and quantity of the immune response against Her2-expressing tumors. Many studies have used Her2eu gene with cytokine or other molecules involved in regulation of immune response to enhance the potency of Her2eu DNA vaccines. Some studies fused adjuvant gene to C-terminal domain of Her2eu gene, while others fused the adjuvant gene N-terminally to Her2eu gene, but no comparison on how direction of fusion could affect efficiency of DNA vaccine has ever been made. Based on previous reports demonstrating potent adjuvant activity of gp96 C-terminal domain, we chose it as adjuvant. The aim of this study was to investigate if direction of fusion could affect adjuvant activity of gp96 C-terminal domain or potency of Her2eu DNA vaccination. To do so, we fused C-terminal domain of gp96 to downstream or C-terminal end of transmembrane and extracellular domain (TM+ECD) of rat Her2eu and resultant immune response to DNA vaccination was evaluated. The results were compared with that of N-terminally fusion of gp96 C-terminal domain to TM+ECD of rat Her2eu. Our results revealed that adjuvant activity of gp96 C-terminal domain is enhanced when fused N-terminally to TM+ECD of rat Her2eu. It suggests that adjuvant activity of gp96 C-terminal domain towards Her2eu is fusion direction-dependent.