For many years, the clinical responses observed in cancer patients treated with antitumor antibodies have been viewed only as a consequence of the recruitment and activation of innate immune cells. Several preclinical studies have indicated that anti-tumor antibodies can also induce a potent anti-tumor adaptive T-cell response capable of protecting animals from tumor challenge. Our studies have shown that CD4+ Th1 cells play a central role in the response to anti-CD20 tumor therapy by opposing Treg expansion and that CD20-specific memory T cells are responsible for anti-tumor protection observed in surviving animals subjected to tumor rechallenge. Whether an adaptive T-cell response is elicited in patients with Follicular Lymphoma (FL) receiving anti-CD20-based treatment is not known. In the present work, we analyzed peripheral T cells before and during anti-CD20-chemotherapy treatment of FL patients (R-CHOP) with high tumor burden. We first examined in ELISPOT assays the IFN-γ production by PBMC from 20 patients against human CD20-derived peptides previously selected by combining in silico and in vivo screening using transgenic human HLA-DR mice. Both FL patients before treatment and patients undergoing R-CHOP treatment exhibited peripheral T-cell responses to the selected CD20-derived peptides. However, these responses were markedly lower than those observed in healthy donors. Similar results were also obtained when T cell responses against viruses commonly infecting large numbers of individuals (CMV, EBV, influenza) were assessed, suggesting that high tumor burden FL patients exhibit an immune exhaustion of T cells. Multiparametric flow cytometry analyses suggested that their poor ability to respond to viral and CD20-derived peptides is related to the presence of an immunocompromised and exhausted blood T-cell peripheral compartment with higher percentages of TIGIT- and PD-1-expressing T cells, of peripheral Treg, and terminally differentiated CD8+ TEMRA. R-CHOP therapy induced a shift of CD4+ and CD8+ T cells toward a central memory phenotype (TCM), an additional shift of CD8+ T cells to a naive phenotype, and a decrease in the number of PD-1+ and TIGIT+ T cells, making these cells evolving toward a lesser degree of exhaustion. However, it did not restore a level of specific responses similar to those observed in healthy donors. These results support the use of anti-PD-1 and anti-TIGIT antibodies in combination with anti-CD20 in FL patients with high-tumor burden.

Citation Format: Benoit Milcent, Pauline Brice, Catherine Thieblemont, Jean-Luc Teillaud, Sophie Siberil. Rituximab chemotherapy induces a partial recovery from T-cell exhaustion in follicular lymphoma patients [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 5616.