Ex vivo evaluation of Newcastle disease virus to enhance natural killer cell function against acute myeloid leukemia cells

Natural killer (NK) cells are promising for adoptive cell therapy in hematological malignancies due to their ability to target tumors and tolerate HLA mismatch. However, their effectiveness is often limited by tumor immune evasion. The aim of this study was to investigate whether infection of AML cells with a non-lytic strain of Newcastle Disease Virus (NDV) can enhance NK cell-mediated cytotoxicity ex-vivo, as a preclinical proof-of-concept for potential sensitization strategies in AML immunotherapy. In the present study, AML cell lines and primary cells derived from newly diagnosed and relapsed/refractory patients were infected with the non-lytic NDV strain Ulster. Following infection, AML cells were co-cultured with NK cells at different Effector-to-Target ratios. Anti-tumor activity of NK cells was assessed by flow cytometry (CFSE/PI staining), lactate dehydrogenase release, and IFN-γ, perforin and granzyme B production. Our results showed that NDV infection of AML cells led to surface expression of viral hemagglutinin-neuraminidase, a danger signal and ligand for NK cell activating receptors. This, in turn, stimulated the specific cytotoxicity response of NK cells against AML cells and significantly elicited IFN-γ production as well as perforin and granzyme B secretion by activated NK cells. To the best of our knowledge, this is the first study demonstrating the potential of cancer immunotherapy through NDV infection of AML cells to enhance NK cell activation and cytotoxicity. Our findings could provide a rationale for a sequential therapeutic strategy in which NDV is administered in vivo to sensitize leukemic blasts, followed by adoptive transfer of ex vivo expanded NK cells to maximize anti-leukemic efficacy.