Despite therapeutic advances, multiple myeloma (MM) remains incurable due to the development of drug resistance by malignant plasma cells (PCs) and a severe immunosuppressive bone marrow (BM) microenvironment. Oncolytic virotherapy offers the dual benefit of tumor cell lysis and immune activation, but the efficacy of human viruses is often hampered by pre-existing antiviral immunity. Here, we demonstrated that bovine herpesvirus type 1 (BoHV-1), a virus that is nonpathogenic to humans, efficiently infected MM cells, inducing mitochondrial apoptosis and suppressing pro-survival programs, including MYC targets, oxidative phosphorylation, and the unfolded protein response. Infected tumor cells upregulated NK-activating ligands and downregulated MHC class I, enhancing susceptibility to NK-mediated cytotoxicity. In patientderived BM mononuclear cells (BMMCs), BoHV-1 selectively reduced malignant PCs and immunosuppressive myeloid subsets, while sparing lymphoid populations and hematopoietic progenitors. The infection promoted activation of CD8⁺ T cells, NK cells, and monocytes, driving a shift toward a pro-inflammatory M1-like polarization. Monocyte depletion in BMMCs attenuated the BoHV-1 anti-MM effect, confirming their functional contribution. This pronounced immune remodeling was accompanied by an inflammatory cytokine storm dominated by type I/II interferons and key innate immune mediators. Co-treatment of BoHV-1 with either bortezomib or lenalidomide increased anti-MM cytotoxicity. Finally, BoHV-1 upregulated CD38 on both MM cells and immune effectors, thereby increasing sensitivity to the anti-CD38 daratumumab. These findings establish BoHV-1 as a promising immunovirotherapy agent, effective as a single agent and in combination strategies, by coupling direct oncolysis with broad immune remodeling of the BM microenvironment.
Raimondi et al. (Thu,) studied this question.
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