Abstract 5199: Tumor-specific antibody response induced by novel immunomodulator, IFx-Hu2.0, reflects extent of epitope spreading to multiple tumor epitopes

Abstract

Abstract While the role of T cells in cancer immunotherapy has been well studied and is relatively clear and well defined, there are few studies elucidating the more complicated involvement of B cells in anti-cancer processes. Preclinical data showed that IFx-Hu2.0 primes both innate and adaptive immune responses through the expression of Emm55, a bacterial protein. Recognition by antigen presenting cells (APC) is followed by interantigenic epitope spreading to tumor antigens expressed in transfected tumor cells. The current study was designed to determine the extent of epitope spreading through quantitating the IgM and IgG responses to known melanoma antigens. Plasma samples (pre-and post-intralesional injection of IFx-Hu2.0) from seven patients with unresectable stage III-IV cutaneous melanoma enrolled in a first-in-human, phase 1 open-label trial (NCT03655756) were analyzed and compared using PEPperCHIP® Melanoma Antigen Microarrays with 21 melanoma-associated antigens converted into linear 15 amino acid peptides with a peptide-peptide overlap of 13 amino acids. The resulting array contained 4,125 different peptides printed in duplicate along with multiple control peptides. The arrays were incubated with plasma samples [collected immediately prior to and four weeks (N=6) or two weeks (N=1) post treatment and three weeks post injection #2 (N=1)] at three dilutions, followed by staining with secondary and control antibodies. Readout with a LI-COR Odyssey Imaging System was followed by quantification of spot intensities and peptide annotation with PepSlide® Analyzer. For generation of IgM/IgG intensity ratios, a minimal baseline intensity of 200 fluorescence units was set. Changes in both IgM and IgG epitope recognition to melanoma-associated antigens was detected in all patients. Baseline and IFx-Hu2.0-induced antibody response profiles for all individuals were heterogeneous, with no dominant common antibody response, pointing to the unpredictability of specific epitope recognition and a relative independence from MHC haplotype requirements due to epitope spreading. Notwithstanding the signals from adjacent peptides, high numbers of newly recognized melanoma epitopes were observed for all patients and all plasma samples. These data suggest enhanced crosstalk between innate and adaptive immune cells, epitope presentation by APC to T and B cells and epitope spreading to multiple previously unrecognized tumor epitopes. IgM and IgG levels were maintained at four weeks post IFx-Hu2.0 administration suggesting continued primary recognition and maturation of effector immune response. B cells represent an important proportion of infiltrating lymphocytes in melanoma and are associated with good prognosis in most cancer types. Studies are underway to determine the relative contribution of B cell activity to anti-tumor effects seen with IFx-Hu2.0. Citation Format: Patricia Lawman, Michael Shamblott, Ashraf Dehlawi, James Bianco. Tumor-specific antibody response induced by novel immunomodulator, IFx-Hu2.0, reflects extent of epitope spreading to multiple tumor epitopes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5199.