An oncolytic vaccinia virus expressing anti-CD47 nanobody exerts enhanced antitumor activity by mediating innate and adaptive immune cell infiltration and activation in the lymphoma tumor microenvironment

Abstract

Anti-CD47 antibodies targeting macrophage immune checkpoints demonstrate benefit in clinical trial, particularly in combination with targeted therapies. This strategy faces challenges from suboptimal efficacy and on-target toxicity due to immunosuppressive tumor microenvironment (TME) and ubiquitous CD47 expression. Here, we report a novel oncolytic vaccine virus (OVV) that expressed therapeutic transgenes encoding the anti-mouse CD47 nanobody or an anti-human CD47 nanobody fused with the IgG1 Fc fragment (term OVV-mCD47nb, OVV-hCD47nb-G1, respectively), and show that anti-CD47 nanobodies secreted by lymphoma cells infected with armed OVVs enhanced tumor phagocytosis via blockade of CD47/SIRPα signal pathway. In an implanted subcutaneously lymphoma mouse model, OVV-mCD47nb demonstrated superior therapeutic efficacy and significantly prolonged survival of tumor-bearing mice when compared to its parental OVV, which might be associated with the recruitment and activation of macrophages, nature killer cells, and T cells within TME. Importantly, we discovered that the specific binding of secreted hCD47nb-G1 to CD47 enhanced macrophage-mediated tumor cell phagocytosis while sparing red blood cells. OVV-hCD47nb-G1 demonstrated superior antitumor efficacy compared to the anti-CD47 antibody Hu5F9 in lymphoma models. Both intratumoral and intraperitoneal administration of OVV-hCD47nb-G1 achieved significant tumor regression and prolonged survival, potentially through TME reprogramming via enhanced immune cell activation. Notably, combination with CD19 CAR-T cells synergistically improved therapeutic outcomes in subcutaneous lymphomas by overcoming the critical barrier of limited CAR-T infiltration. Our findings establish that arming OVV with a CD47-blocking nanobody and IgG1 Fc creates a dual-functional therapeutic platform, offering a paradigm-shifting strategy for lymphoma immunotherapy through coordinated innate and adaptive immune activation.