Abstract 4978: Adoptively transferred CMV-specific T-cells recognizing dominant and sub-dominant pp65 epitopes demonstrate improved in vivo inhibition of tumor xenografts in combination with PD-1 inhibition

Adoptive transfer of transplant donor or third party donor derived CMV-specific T cells (CMV-CTL) can effectively treat CMV infections in HSCT recipients. In clinical trials, infusion of partially matched third party CMV-CTLs, has demonstrated high response rates against persistent CMV infection. T-cells (TC) generated in vitro or directly selected in vivo demonstrate a striking preponderance of specificity for 1-2 immunodominant (ID) epitopes presented by specific HLA alleles. ID epitopes elicit higher TC functional activity in vivo, compared to sub-dominant (SD) epitopes. The relative clinical efficacy of TC directed against ID versus SD epitopes in vivo remains undefined. Agents augmenting activity of TC responsive to SD epitopes are unexplored. When these alleles are co-inherited in humans, epitopes of CMVpp65 presented by HLA A*02:01 are ID over HLA A*24:02 presented epitopes. We describe an in vivo model to assess efficacy of CMV-CTLs using colon carcinoma cells (coca)transduced to express CMVpp65, as a surrogate system. HLA A*02:01 + and A*24:02 + human coca cells were transduced to express CMVpp65 and GFP-firefly luciferase (cocapp65). CMV-CTLs responding to either the A*0201 presented ID NLV epitope (A2-NLV) or the A*24:02 presented SD QYD epitope (A24-QYD) were generated from donors co-inheriting HLA A*02:01 and A*24:02 by in vitro stimulation using NIH 3T3 artificial antigen presenting cells, expressing HLA A*02:01 or A*24:02, B7.1, LFA-3, and ICAM1. Tumor cells (10 5 cells) were injected subcutaneously into groups of 5-6 NSG mice on the R flank, and 10 5 cells from a pp65 expressing melanoma cell line (melpp65), lacking expression of HLA A*02:01 or A*24:02 were injected on the L shoulder as control. 2 Groups each received 10 6 of tetramer + A2-NLV or A24-QYD CMV-CTLs i.v per mouse; one of each CMV-CTL treated group also received 2 i.v doses ( 200µg /dose) of anti-PD1 antibody (Nivolumab-BMS) at day 2 and 7 post CTL infusion. Control groups received IL-2, with or without anti-PD1, or HLA mismatched CMV-CTLs. Tumor growth was monitored by bioluminescent imaging. CMV-CTLs responsive to SD A24-QYD epitope induced significant cocapp65 growth suppression compared to controls, but did not eradicate tumors in any animal. Combined treatment of A24-QYD CMV-CTLs with anti-PD-1 Ab induced complete cocapp65 eradication in 2 of 5 mice, with minute residual tumors in 3 mice. Treatment with ID A2-NLV CMV-CTLs induced complete cocapp65 eradication in 2 of 5 mice, and smaller residual tumors compared to SD A24-QYD CTL treatment. Combined treatment with anti-PD-1 and A2-NLV CMV-CTLs led to complete cocapp65 eradication in 3 of 5 mice, with minute tumors in 2 mice. Taken together, these data provide evidence that blocking the PD-1/PD-L1 interaction may significantly augment the antiviral activity of both ID and SD CMV-CTLs. Citation Format: Aisha N. Hasan, Annamalai Selvakumar, Tzu-Yun Kuo, Richard J. O9Reilly. Adoptively transferred CMV-specific T-cells recognizing dominant and sub-dominant pp65 epitopes demonstrate improved in vivo inhibition of tumor xenografts in combination with PD-1 inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4978. doi:10.1158/1538-7445.AM2017-4978