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1308 Bacteria specific IL-10 secreting T-cells derived from the gut are cross-reactive with tumor antigens and accelerate tumor growth in mouse models
  1. Denise Cecil1,
  2. Jean Feng2,
  3. Alex Paynter2,
  4. Jessica Perry2,
  5. Noah Simon2,
  6. Nicholas Drovetto2,
  7. Lauren Corulli2,
  8. Erin Rodmaker2,
  9. Susan Strenk3,
  10. David Fredricks3 and
  11. Mary Disis1
  1. 1UW Medicine Cancer Vaccine Institute, Seattle, WA, USA
  2. 2University of Washington, Seattle, WA, USA
  3. 3Fred Hutch Cancer Center, Seattle, WA, USA


Background We developed a method of CD4 epitope identification that includes selecting Class II interacting sequences via a multi-algorithm followed by functional phenotyping. We have evaluated 152 epitopes from 17 non-mutated tumor antigens (TA) and demonstrated Class II restricted epitopes could be identified which elicit either a selective Type I (IFN-gamma) or Type II (IL-10) response across multiple human PBMC (n=40). IL-10 inducing TA epitopes often shared a >50% identity and cross reactivity with multiple gut bacterial species. We questioned how prevalent these bacteria-tumor antigen (BAC-TA) cross reactive T-cells were in humans and whether these cells had any effects in cancer.

Methods IL-10 ELISPOT quantified BAC-TA T-cells in human PBMC, murine spleen, and tumor infiltrating lymphocytes (TIL). Human and murine T-cell lines were tested against bacteria, TA, and controls to show cross reactivity and specificity. Murine BAC-TA T-cells were used for adoptive transfer. T-cells were characterized by cytokine array, PCR, and flow cytometry. The C3(1)-Tag transgenic model of mammary cancer was used to assess effects of BAC-TA T-cells on tumor growth.

Results Measurable BAC-TA T-cells occurred in in up to 90% of PBMC. TA epitopes with the highest incidence of response shared significant sequence homologies with greater than 10 bacterial species. TA specific T-cell lines from multiple donors showed significant reactivity to homologous bacteria and recombinant TA protein, but not unrelated bacteria and protein. Human BAC-TA T-cells secreted IL-6 and IL-10, were memory T-cells, and expressed genes similar to intraepithelial lymphocytes. Similar BAC-TA T-cells were identified in mice. P. aeruginosa-specific T-cells generated from FVB mice secreted significantly more IL-10 when stimulated with the 70% homologous peptide YB1-p82-96 as compared to HIV peptide; p=0.0004. We implanted a syngeneic tumor cell line into C3(1)-Tag. After tumor was established, fluorescently-labeled P. aeruginosa-YB1 specific T-cells were injected. Significantly increased florescence was seen in 100% of tumors and no fluorescence in mice injected with labeled naïve splenocytes (p<0.0001). Tumor volume 20 days after transfer was increased 55% in mice receiving P. aeruginosa/YB1-T-cells compared to splenocytes (p<0.0001). When C3(1)-Tag developed spontaneous tumors (500±75 mm3) TIL analysis revealed numerous IL-10-secreting BAC-TA T-cells that had migrated from blood to tumor.

Conclusions A select group of bacteria are associated with the majority of homologies driving generation of BAC-TA T-cells. We have also identified bacteria never associated with TA homologies. These data lay the foundation for precision probiotics designed to reduce the BAC-TA memory T-cell pool.

Acknowledgements This work was funded by the Department of Defence Breast Cancer Program, the Kuni Foundation, WIngs of Karen, and the Helen B Slonaker Professorship.

Ethics Approval University of Washington Institutional Approval was obtained for all animal work shown here (#2878-01). All blood samples were obtained with written informed consent by the University of Washington Human Subjects Division (Protocol #7721).

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