Enveloped Oncolytic Viruses Boost CD19 CAR-T in Gastrointestinal Tumors

Chimeric antigen receptor T (CAR-T) cell therapy has emerged as a breakthrough in cancer immunotherapy. By genetically engineering patient-derived T cells to express synthetic receptors, CAR-T cells can specifically recognize and eliminate tumor cells. The therapeutic efficacy of CAR-T cells depends heavily on their ability to effectively home to and infiltrate the tumor microenvironment, as well as to specifically recognize tumor-associated antigens on malignant cells.

Early studies primarily targeted tumor-associated antigens (TAAs), but these antigens are also expressed in critical normal tissues, and off-tumor toxicity frequently leads to severe adverse events. For example, CAR-T cells targeting carcinoembryonic antigen (CEA) can induce marked but transient colitis, while CAR-T cells targeting MART-1 can damage skin, ocular, or auricular tissues.

Researchers subsequently sought tumor-specific antigens (TSAs) as alternative targets; however, naturally occurring TSAs are scarce and difficult to identify. Although CAR-T therapy has achieved striking success in hematologic malignancies, the scarcity of stable antigen targets and the highly immunosuppressive tumor microenvironment have greatly limited its application in solid tumors.

Recently, investigators from Shanghai Jiao Tong University in China published an online article in Biomaterials titled "Coated oncolytic viruses based ‘double strike’ strategy triggering CD19 CAR-T therapy in gastrointestinal tumors". To enhance the immunotherapeutic efficacy of CAR-T cells against solid tumors, the team developed an integrated system that employs an oncolytic adenovirus to simultaneously introduce a surface antigen target for CAR-T cells and remodel the immunosuppressive tumor microenvironment. The system uses B cell membrane-derived CD19 as an artificial antigen target displayed on tumor cells and can generate, in situ, an anti-CD3e × anti-epithelial cell adhesion molecule (EpCAM) bispecific T-cell engager, thereby further enhancing the binding and cytotoxicity of CD19 CAR-T cells against tumor cells.

Figure 1. A "Double Strike" strategy to trigger CD19 CAR-T thearpy on gastrointestinal tumors was established in this study through a coated oncolytic virus platform. (ZHANG, Haoyu, et al., 2026)

Oncolytic viruses offer unique advantages, including selective infection of tumor cells and activation of the tumor immune microenvironment. Through genetic engineering, oncolytic viruses can be armed with cytokines, bispecific T-cell engagers, and immune checkpoint inhibitors to enable multi-component combination therapy. Bispecific T-cell engagers bridge tumor antigens and T-cell receptors and have already achieved clinical success in B-cell malignancies.

Despite the promising potential of combining oncolytic viruses with CAR-T therapy, clinical application remains constrained by challenges associated with systemic delivery—notably, pre-existing or rapidly induced anti-viral antibodies—often limiting usage to intratumoral injections. To improve delivery, cell membrane-coating strategies have shown strong potential. Tumor cell membranes possess homotypic targeting capabilities, which can enhance intratumoral delivery, particularly for intravenous administration.

In this study, an oncolytic adenovirus expressing αCD3e-αEpCAM (Adv-αCD3e-αEpCAM, Epv) was encapsulated within a fusion membrane derived from B cells and tumor cells, and the fusion membrane was further modified with a glutathione-responsive, disulfide-linked polyethylene glycol long chain (PEG–SS–PEG), resulting in the Epv@CMP delivery system. This design aimed to improve tumor-targeted delivery efficiency and therapeutic outcomes.

The αCD3e-αEpCAM bispecific T-cell engager links T cells to tumor cells, while B cell membrane components integrate into the tumor cell surface to provide a CD19 target, together forming a “double strike” strategy that facilitates CD19 CAR-T therapy. The study found that Epv@CMP, when applied to gastrointestinal tumors, further activated the tumor immune microenvironment. Leveraging a three-pronged targeting and activation mechanism, Epv@CMP combined with CD19 CAR-T cells achieved superior therapeutic efficacy.