Salmonella immunotherapy engineered with highly efficient tumor antigen coating establishes antigen-specific CD8+ T cell immunity and increases in antitumor efficacy with type I interferon combination therapy

Abstract

Bacteria-based cancer therapy employs various strategies to combat tumors, one of which is delivering tumor-associated antigen (TAA) to generate specific immunity. Here, we utilized a poly-arginine extended HPV E7 antigen (9RE7) for attachment on Salmonella SL7207 outer membrane to synthesize the bacterial vaccine Salmonella-9RE7 (Sal-9RE7), which yielded a significant improvement in the amount of antigen presentation compared to the previous lysine-extended antigen coating strategy. In TC-1 tumor mouse models, Sal-9RE7 monotherapy decreased tumor growth by inducing E7 antigen-specific immunity. In addition, pairing Sal-9RE7 with adjuvant Albumin-IFNβ (Alb-IFNβ), a protein cytokine fusion, the combination significantly increased the antitumor efficacy and enhanced immunogenicity in the tumor microenvironment (TME). Our study made a significant contribution to personalized bacterial immunotherapy via TAA delivery and demonstrated the advantage of combination therapy.

Arginine-linked HPV-associated E7 displaying bacteria-derived outer membrane vesicles as a potent antigen-specific cancer vaccine

“…In this study, we wanted to demonstrate the wide applicability of our efficient arginine peptide-enhanced antigen coating platform that is not only restricted to bacteria as carriers [ 8 ], but also bacteria-derived OMVs. Here, we saw the importance of arginine residues in enhancing affinity between 9RE7 peptide and SOMV.…”

“…By retaining the similar inflammatory components to parental gram-negative bacteria, OMVs can engage APCs through TLR4 recognition and cross-present antigens to T cells [ 26 ]. Previously we saw that 9RE7 peptide could stimulate E7-specific through peptide loading on dendritic cells [ 8 ]. This creates a potential confound of false positive activation from unbound 9RE7 in SOMV-9RE7 synthesis that wasn’t removed during the filtration procedure.…”

“…Future investigation will focus on the differences in therapeutic efficacy of 9RE7-coated Salmonella and SOMV to determine the more efficacious and safer platform for bacterial immunotherapy in HPV-associated and other cancer models. Previous bacteria-based combination therapy results showed highly synergistic benefits of pairing cytokine or immune checkpoint inhibitors to enhance the efficacy of bacteria therapy [ 8 , 9 , 28 ]. Our future experiments will dive into augmenting the CD8+ T cell-mediated tumor-specific immune cascade to determine synergistic combination therapy targets.…”

“…Studies have shown that bacteria-based therapies can serve as a monotherapy or complement to other anticancer therapies [ 5 – 7 ]. Previously, we showed that live Salmonella and cytokine combination therapy induced potent T-cell immunity and long-term tumor control in mice [ 8 ]. We also demonstrated that heat-inactivated Salmonella (S. typhimurium) could display tumor antigens to achieve tumor-specific immune responses [ 9 ].…”

“…Previously, we optimized a bacteria antigen-display strategy through modification of the Human Papillomavirus (HPV)-associated E7 antigen, incorporating nine arginine residues (9RE7) for enhanced E7 coating [ 8 ]. Poly-l-arginine is a cell penetrating peptide (CPP), often used for mammalian cell uptake and delivery of drugs or macromolecules such as proteins and enzymes [ 22 , 23 ].…”