Abstract 5639: Changes in local and peripheral T cell diversity after HPV E7 antigen-expressing Listeria-based immunotherapy (ADXS11-001) prior to robotic surgery for HPV-positive oropharyngeal cancer

Abstract

Abstract Human papilloma virus associated oropharyngeal cancers (HPVOPC) account for about one third of OPC and express foreign viral antigens such as the E6 and E7 oncogenes, which are suitable for immune targeting. We performed a “window of opportunity” trial of patients undergoing standard-of-care transoral surgery for HPVOPC to assess the effect of the HPV16-E7 targeting vaccine ADXS11-001 on the intratumoral and systemic immune response. We reported, in a prior abstract, that 5 of 8 ADXS11-treated patients showed increased E6 or E7-specific IFN-γ responses post-treatment and 4/8 patients demonstrated increased CD8 and CD4 tumor infiltrating lymphocytes (TILs) after vaccination. In the present study, we profiled peripheral blood immunocyte populations (PBMCs) pre-vaccination, post-vaccination and post-surgery via multicolor flow cytometry in 8 patients. Clonal expansion and diversification of PBMCs and tumor TILs post-treatment were determined via T cell receptor (TCR) DNA sequencing and correlated to HPV antigen specific immune responses determined by ELISPOT as well as tumor immune profile determined by quantitative immunofluorescence. While peripheral CD8 cytotoxic T cell (CTL) levels remained constant over the course of the study, we observed trends towards their increased expression of LAG-3 (1.6 fold, p=0.0821) and PD-1 (1.6 fold, p=0.0748) 6 weeks post-surgery, consistent with activation. We did not observe statistically significant changes in levels of CD4 T helper cells, MDSC or Tregs, although a modest trend towards decreased CD8/MDSC ratio was observed post-surgery (0.5 fold, p=0.0864). Overall TCR diversity/clonality of PBMCs and TILs did not change. However the comparison of similarity between T cell repertoires of the tumor and PBMCs (Morisita's index) demonstrated an increase of expanded clones post-vaccination limited to TILs in 5/6 patients, indicating clonal expansion in ADXS11-treated patients. When we analyzed T cell repertoire changes in individual patients, 4 of 8 patients demonstrated expansion of specific TCR clones post-vaccination. The two patients with the greatest increase in number of expanded TCR clones among both, PBMCs and TILs, also had the strongest increase of E6 or E7-specific IFN-γ responses post-treatment, and also had strongly increased CD8 TILs. Our results demonstrate that immunomodulatory effects of ADXS11-001 on the local and peripheral immune response vary among patients, with 2/8 treated patients demonstrating evidence of an integrated adaptive immune response in blood and tumor, consistent with selective clonal expansion in the context of a vaccine-induced anti-tumor T cell response. Profiling of additional patients will permit more detailed analysis of ADXS11-induced immune modulation and impact on TCR diversity. Citation Format: Rosemarie Krupar, Ravi R. Pathak, Naoko Imai, Eric Genden, Krzys Misiukiewicz, Elizabeth G. Demicco, Jigneshkumar Patel, Falguni Parikh, Michael Donovan, Seunghee Kim-Schulze, Sven Perner, Marshall Posner, Brett Miles, Sacha Gnjatic, Andrew G. Sikora. Changes in local and peripheral T cell diversity after HPV E7 antigen-expressing Listeria-based immunotherapy (ADXS11-001) prior to robotic surgery for HPV-positive oropharyngeal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5639.