Engineered Lactococcus lactis secreting Flt3L and OX40 ligand for in situ vaccination-based cancer immunotherapy

Abstract

In situ vaccination is a promising strategy to convert the immunosuppressive tumor microenvironment into an immunostimulatory one with limited systemic exposure and side effect. However, sustained clinical benefits require long-term and multidimensional immune activation including innate and adaptive immunity. Here, we develop a probiotic food-grade Lactococcus lactis-based in situ vaccination (FOLactis) expressing a fusion protein of Fms-like tyrosine kinase 3 ligand and co-stimulator OX40 ligand. Intratumoural delivery of FOLactis contributes to local retention and sustained release of therapeutics to thoroughly modulate key components of the antitumour immune response, such as activation of natural killer cells, cytotoxic T lymphocytes, and conventional-type-1-dendritic cells in the tumors and tumor-draining lymph nodes. In addition, intratumoural administration of FOLactis induces a more robust tumor antigen-specific immune response and superior systemic antitumour efficacy in multiple poorly immune cell-infiltrated and anti-PD1-resistant tumors. Specific depletion of different immune cells reveals that CD8+ T and natural killer cells are crucial to the in situ vaccine-elicited tumor regression. Our results confirm that FOLactis displays an enhanced antitumour immunity and successfully converts the ‘cold’ tumors to ‘hot’ tumors.

Engineered Bacteriophage-Based In Situ Vaccine Remodels a Tumor Microenvironment and Elicits Potent Antitumor Immunity

“…However, the tumor growth of the anti-PD-1 antibody group (792.22 mm 3 ) was not inhibited significantly compared with the PBS group (987.28 mm 3 ), which might be partially due to the poor tumor-infiltrating of CD8 + T cell of the cold tumor model. 37,38 Notably, the combination therapy of the H-GM-M13 CD40 + anti-PD-1 antibody achieved a marvelous 100% survival rate in mice over 46 days, and the H-GM-M13 CD40 group also achieved a 50% survival rate. In contrast, all mice in the anti-PD-1 antibody group died within 36 days, and those in the PBS group died within 32 days (Figure 7e).…”

Cytotoxicity as a form of immunogenic cell death leading to efficient tumor antigen cross‐priming

“…Advancing our knowledge of all these processes may permit translation into innovative therapeutic interventions such as raising cDC1 numbers using sFLT3L in combination with immunotherapy strategies. 31,33,34,38,45,[87][88][89] Moreover, perhaps by mimicking or enforcing cytotoxicity in part of the tumor lesions, we could generate endogenous vaccines. Furthermore, even if cytotoxicity is immunogenic for CTL priming, it might be suboptimal, hence calling for stronger cDC1 maturation stimuli such as TLR agonists or CD40 agonists 90,91 to render more efficacious results (Figure 2).…”

“…Advancing our knowledge of all these processes may permit translation into innovative therapeutic interventions such as raising cDC1 numbers using sFLT3L in combination with immunotherapy strategies 31,33,34,38,45,87–89 . Moreover, perhaps by mimicking or enforcing cytotoxicity in part of the tumor lesions, we could generate endogenous vaccines.…”

Radiotherapy-Triggered In Situ Tumor Vaccination Boosts Checkpoint Blockaded Immune Response via Antigen-Capturing Nanoadjuvants

“…The limited progress can be largely attributed to various challenges faced by the current tumor vaccines, , including tumor heterogeneity with diverse somatic mutations, unsatisfactory delivery efficiency, DCs dysfunction, and the immune escape of tumors via programmed death ligand-1/programmed death 1 (PD-L1/PD-1) signaling pathway. In situ vaccination (ISV) is becoming an increasingly attractive strategy that combines tumor autoantigens, derived from immunogenic cell death (ICD) induced by radiotherapy or chemotherapy, with immunostimulants. , It offers potential for overcoming tumor heterogeneity and eliciting a systemic antitumor immune response capable of targeting unrecognized metastases in a personalized manner. − Until now, numerous clinical or preclinical trials have been focused on ISV induced by radiotherapy. , For example, in combination with intratumorally injected CpG oligonucleotide, an agonist of Toll-like receptor 9 (TLR9), radiotherapy was demonstrated to induce regression at the treated tumor site as well as significant shrinkage at distant tumor site . Researchers at the Icahn School of Medicine at Mount Sinai also proposed a radiotherapy-induced ISV that involved repeated intratumoral injections of Fms-like tyrosine kinase 3 ligands to recruit DCs into tumor, followed by multiple intratumoral injections of a TLR3 agonist to activate DCs .…”