CD45RA expressing lymphocytes inhibit the outgrowth of Epstein-Barr Virus Specific T-cells from Patients with EBV+ Lymphoma

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Abstract EBV antigen specific T-cells (EBVSTs) are difficult to expand from patients with EBV-positive lymphoma, perhaps because they circulate with low frequency or are rendered dysfunctional by the suppressive lymphoma microenvironment. As a result, we were unable to produce EBVSTs from ~25% of EBV+ lymphoma patients in our clinical trial (NCT01555892). To enrich memory T-cells prior to EBVST generation, we depleted the CD45RA+ subset of PBMCs, that includes naïve T-cells (TN), NK-cells, T-stem cells (TSCM) and terminally differentiated T-cells (TEMRA). CD45RA depletion (RAD) enhanced EBVST proliferation, antigen-specificity, polyfunctionality, cytotoxicity and tumor clearance in a murine model, and most importantly, enabled the outgrowth of EBVSTs from patient PBMCs that had previously failed to respond. This observation led to our hypothesis that bystander CD45RA+ cells inhibit the outgrowth of memory EBV antigen specific T-cells. TCR-β chain sequencing showed that the clonotypes with greatest expansion in RAD-EBVSTs failed to expand or expanded poorly in EBVSTs from whole PBMCs (W-EBSVTs), reflecting a more selective clonal expansion in RAD-EBVSTs. TCR repertoire of W-EBVSTs was more similar to that of EBVSTs derived from CD45RA+ PBMCs that lacked detectable EBV specificity and to that of the original PBMCs. Subsets add back to RAD-PBMCs suggested that the CD3+ CD45RA+ subset inhibits the reactivation and clonal expansion of EBV-Ag specific memory T-cells. This may represent a physiological strategy to prevent the oligoclonal outgrowth of inappropriate memory T-cells during primary infection. This approach has been translated into our ongoing clinical trials using NCT01555892 and NCT04288726 using EBVST against lymphoma. This work was funded and supported by CPRIT RP160283- Baylor College of Medicine Comprehensive Cancer Training Program, NIH-NCI P50 CA126752, American Society of Gene and Cell Therapy (ASGCT) Career Development Award, and Tessa Therapeutics.

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