1086 IGHV1-69 as a Promising Candidate for the Development of a Shared Immunotherapy to B-cell Lymphomas

Abstract

B-cell Non-Hodgkin Lymphomas (B-NHL) are a heterogeneous group of cancers, broadly diffused worldwide and often relapsing after standard treatment and rituximab. Therapeutic vaccines targeting B-NHL idiotype (Id) represent a promising approach to maintain the complete response induced by standard treatments. However, customized idiotypic vaccination still remains a non-approved, experimental therapeutic option, mostly due to the personalized use and penalized by the lack of reliable clinical or biological markers of patient eligibility and responsiveness. Nevertheless, the molecular characterization of different lymphoid tumor histotypes revealed a set of stereotyped immunoglobulins among distinct B-cell lymphoma types. On this ground, we focused our attention on the IGHV1-69 protein, frequently expressed in HCV-associated lymphomas, chronic lymphocytic leukaemia, and auto-immunity related lymphoproliferations, and we characterized the ex vivo immunogenicity of this protein.Seventy IGHV1-69 sequences obtained from patients affected by different B-NHLs or pre-malignant lymphoproliferations were compared to design an optimized sequence characterized by the highest degree of similarity among studied cancers, and thus CDR3 hypervariable region free. Within this "immunogenically" optimized sequence, we identified 13 potential HLA class-I cytotoxic T lymphocyte (CTL) epitopes and synthesized the corresponding pentamers (Pent). We assessed by flow cytometry the presence and extent of epitope-specific T-cell responses in peripheral blood of patients with IGHV1-69 + B-cell lymphoproliferative disorders and healthy donors, and validated these data in IFN-γ ELISPOT (Enzyme-linked immunosorbent spot) assays. Finally, we boosted in vitro IGHV1-69-specific responses by stimulating peripheral blood lymphocytes (PBL) from donors and patients with different protocols for the generation of epitope-specific CTL cultures.Interestingly, the IGHV1-69 Pent + population observed in patients' samples was generally larger than in donors, supporting the existence of spontaneous memory T-cell responses against IGHV1-69, at least for some HLA-restrictions. Surprisingly, in patients' samples, IGHV1-69-recognizing T cells displayed higher IFN-γ release in ELISPOT assays compared to viral-specific T cells. Moreover, we obtained peptide-specific CTL lines, which showed a weak but specific lysis against peptide-pulsed targets, especially when derived from patients' PBLs. In addition, we were able to generate IGHV1-69-epitope specific CTL clones from healthy donors CD8 + T cells, employing synthetic artificial APC, developed to elicit and expand low-avidity tumor-directed human CTL lines. Finally, IGHV1-69-induced CTL lines showed specific lysis also towards an IGHV1-69 naturally expressing cell line, suggesting that IGHV1-69 memory T-cell responses could be boosted for therapeutic purposes.These results show that IGHV1-69 constitutes a potential target for the development of a subset-specific Id vaccine. Furthermore, multimer (tetramers...