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Chimeric antigen receptor (CAR) - engineered natural killer (NK) cell therapy has emerged as a promising platform for adoptive immunotherapy for cancer. However, CAR-NK or CAR-T therapy so far has achieved limited efficacy in solid tumors compared with hematologic malignancies. One of the challenges is the lack of prevalent tumor-specific surface antigen target in solid tumors. Hence, we are developing a novel oncolytic vaccinia virus (VV) to deliver a dual functional glycol-immune checkpoint inhibitor and universal tumor cell marker combined with CAR-NK cell therapy to increase anti-tumor efficacy. Using the vaccinia virus deleted in both viral TK and VGF genes (vvDD) to drive the expression of a membrane-bound sialidase derived from actinomyces viscosus (avSial) under the viral late promoter, we observed efficient desialylation of both VV-infected and non-infected tumor cells, which would alleviate the suppression of sialic acid on NK and other immune cells within TME. Further, the surface bound avSial on VV-infected tumor cells can also serve as a universal target for avSial-CAR NK cells, with less concern for cross-reactivity to normal human tissues and antigen loss. We developed anti-avSial antibodies through mice immunization study. The selected single chain variable fragments (scFV) were constructed in CAR format containing CD28 CD3 ζ for co-stimulation and human IL-15 gene for better NK persistence and function. The binding affinity of anti-avSial scFv to avSialidase were further screened in CAR constructs-transfected 293T cells. The selected anti-avSial scFv CAR were packaged into gamma retroviral vectors to transduce activated and expanded NK cells derived from healthy donor peripheral blood. For proof-of-concept, target tumor cell lines A375, A549 and HT-29 expressing transmembrane sialidase and GFP were also generated. Compared with CD19 CAR NK and none transduced (NT) NK cells, avSial CAR NK had markedly increased cytotoxicity against avSial-expressing tumor cells in co-culture assays at low E:T ratios Citation Format: Xiaomei Wang, Guowei Wei, Keshav B. Karki, Winnie Chan, Mariya Viskovska, Andrew Williams, Nancy Chang, Haiyan Jiang. Developing a novel combination therapy using engineered chimeric antigen receptor natural killer cells targeting avsialidase with avsialidase-armed oncolytic vaccinia virus in solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6225. |
