Anti-tumor efficacy of plasmid encoding emm55 in a murine melanoma model

Abstract

Emm55 is a bacterial gene derived fromStreptococcus pyogenes(S. pyogenes) that was cloned into a plasmid DNA vaccine (pAc/emm55). In this study, we investigated the anti-tumor efficacy of pAc/emm55in a B16 murine melanoma model. Intralesional (IL) injections of pAc/emm55significantly delayed tumor growth compared to the pAc/Empty group. There was a significant increase in the CD8(+)T cells infiltrating into the tumors after pAc/emm55treatment compared to the control group. In addition, we observed that IL injection of pAc/emm55increased antigen-specific T cell infiltration into tumors. Depletion of CD4(+)or CD8(+)T cells abrogated the anti-tumor effect of pAc/emm55. Combination treatment of IL injection of pAc/emm55with anti-PD-1 antibody significantly delayed tumor growth compared to either monotherapy. pAc/emm55treatment combined with PD-1 blockade enhanced anti-tumor immune response and improved systemic anti-tumor immunity. Together, these strategies may lead to improvements in the treatment of patients with melanoma.