Non-viral -knocked-in CD19CAR-T and gp350CAR-T cells tested against Burkitt lymphomas with type 1 or 2 EBV infection: cellular dynamics and potency.

Introduction: The ubiquitous Epstein-Barr virus (EBV) is an oncogenic herpes virus associated with several human malignancies. EBV is an immune-evasive pathogen that promotes CD8 T cell exhaustion and dysregulates CD4 T cell functions. Burkitt lymphoma (BL) is frequently associated with EBV infections. Since BL relapses after conventional therapies are difficult to treat, we evaluated prospective off-the-shelf edited CAR-T cell therapies targeting CD19 or the EBV gp350 cell surface antigen.

Methods: We used CRISPR/Cas9 gene editing methods to knock in (KI) the CD19CAR.CD28z or gp350CAR.CD28z into the T cell receptor (TCR) alpha chain () locus.

Results: Applying upscaled methods with the ExPERT ATx MaxCyte system, KI efficacy was ~20% of the total ~2 × 10 TCR-knocked-out (KO) generated cells. TCRCAR-T cells were co-cultured with the gp350CD19 BL cell lines Daudi (infected with type 1 EBV) or with Jiyoye (harboring a lytic type 2 EBV). Both types of CAR-T cells showed cytotoxic effects against the BL lines . CD8CAR-T cells showed higher persistency than CD4CAR-T cells after co-culture with BL and upregulation of the activation/exhaustion markers PD-1, LAG-3, and TIM-3. Two preclinical xenograft models were set up with Nod.Rag.Gamma mice injected intravenously (i.v.) with 2 × 10 Daudi/fLuc-GFP or with Jiyoye/fLuc-GFP cells. Compared with the non-treated controls, mice challenged with BL and treated with CD19CAR-T cells showed delayed lymphoma dissemination with lower EBV DNA load. Notably, for the Jiyoye/fLuc-GFP model, almost exclusively CD4 CD19CAR-T cells were detectable at the endpoint analyses in the bone marrow, with increased frequencies of regulatory T cells (T) and TIM-3CD4 T cells. Administration of gp350CAR-T cells to mice after Jiyoye/GFP-fLuc challenge did not inhibit BL growth but reduced the EBV DNA load in the bone marrow and promoted gp350 antigen escape. CD8PD-1LAG-3 gp350CAR-T cells were predominant in the bone marrow.

Discussion: The two types of TCRCAR-T cells showed different therapeutic effects and dynamics. These findings reflect the complexities of the immune escape mechanisms of EBV, which may interfere with the CAR-T cell property and potency and should be taken into account for future clinical translation.