{
  "abstract": "Background FDA-approved therapies afamicel and tebentafusp target peptide antigens from MAGE-A4 and gp100, presented by HLA-A*02:01. Effective treatments are needed for patients with other common MHC I alleles, such as HLA-A*03:01. These require identification and cloning of T cell receptors (TCRs) with sufficient functional avidity to recognize cancer cells. High-avidity T cells reactive to non-mutated shared antigens (nmSAgs), including cancer-testis antigens and differentiation antigens, are rare in peripheral blood. We hypothesized that vaccination against nmSAgs may overcome central tolerance mechanisms and induce T cell responses with TCRs of sufficient avidity for potential therapeutic applications.Methods T cells were collected from a patient at the time of peak immune response after vaccination with 12 class I MHC-restricted nmSAg peptides ( NCT01585350) and evaluated for reactivity to the vaccine peptides. Antigen-reactive TCRs were sequenced and expressed in Jurkat cells to analyze their functional avidity (EC50; based on CD69 upregulation by flow cytometry) and in primary T cells to test their reactivity to human tumor cells. Responses to HLA-matched tumor cell lines with endogenously presented target antigens were measured by co-expression of activation markers CD137, CD69, and CD25, secretion of IFNγ and TNFα, and target cell lysis (xCELLigence assay).Results Vaccine-induced HLA-A*03:01-restricted TCRs for the peptides gp100 17-25 and MAGE-A196-104 were isolated from peripheral blood after vaccination. Multiple TCRs targeting gp10017-25 were identified with EC50s between 10-100 nM (figure 1A), and CD8-independent activation was observed for two clonotypes (figure 1B). TCR-transduced primary CD8 T cells upregulated CD137, CD69, and CD25 upon exposure to naturally processed antigen on an allogeneic HLA-A*03:01+ gp100+ human VMM18 melanoma cell line (figure 1C), and lysed VMM18 tumor cells at E:T ratios below 1:1 (figure 1D). Similarly, a vaccine-induced MAGE-A196-104-reactive TCR was obtained: TCR-transduced primary CD8 T cells were activated upon coculture with multiple HLA-A*03:01+ cancer cells expressing endogenous MAGE-A1 (figure 2A), secreted IFNγ and TNFα (figures 2B&C), lysed cancer cells at low E:T ratios (figure 2D), but did not respond to cells without HLA-A*03:01 or MAGE-A1.Conclusions HLA-A*03:01-restricted TCRs for nmSAgs were readily identified among circulating T cells after peptide vaccination. T cells engineered to express nmSAg-specific TCRs recognized endogenously presented antigen and demonstrated potent antigen-specific cytotoxicity. Expansion of these T cells in patients after vaccination was well-tolerated, suggesting safety in future therapeutic use. Our data demonstrate the potential of combining cancer vaccine therapy with downstream development of TCR-based therapies by facilitating the identification of high-avidity TCRs, without requiring affinity optimization.Abstract 340 Figure 1TCR reactivity from a vaccinated patient (VMM1113) targeting gp10017-25. EC50 concentrations on CD8+ Jurkat cells (A) and CD8+ and CD8- Jurkat cells (B). Engineered primary CD8+ T cell expression of activation-induced markers (C) and specific lysis at varying E:T ratios (D)Abstract 340 Figure 2Reactivity of a TCR targeting MAGE-A196-104 from patient VMM1113. Expression of activation-induced markers (A), secretion of IFNγ (B) and TNFα (C), and specific lysis at varying E:T ratios (D) by engineered primary CD8+ T cells after coculture with human cancer cell lines",
  "authors": [
    {
      "affiliations": [
        "Shennon Biotechnologies, San Francisco, CA, USA"
      ],
      "name": "Michael J Malone"
    },
    {
      "affiliations": [
        "University of Virginia, Charlottesville, VA, USA"
      ],
      "name": "Emily K Ninmer"
    },
    {
      "affiliations": [
        "Shennon Biotechnologies, San Francisco, CA, USA"
      ],
      "name": "Sonali Kanaya"
    },
    {
      "affiliations": [
        "University of Virginia, Charlottesville, VA, USA",
        "University of Virginia Comprehensive Cancer Center, Charlottesville, VA, USA"
      ],
      "name": "Kristin G Anderson"
    },
    {
      "affiliations": [
        "Shennon Biotechnologies, San Francisco, CA, USA"
      ],
      "name": "Li Sun"
    },
    {
      "affiliations": [
        "Shennon Biotechnologies, San Francisco, CA, USA"
      ],
      "name": "Kaitao Li"
    },
    {
      "affiliations": [
        "University of Virginia School of Medicine, Charlottesville, VA, USA"
      ],
      "name": "Craig L Slingluff"
    }
  ],
  "title": "340 Cancer vaccination induces high-avidity T cell receptors reactive to endogenously presented target antigens for use in future T cell therapies for HLA-A*03:01+ cancer patients",
  "uid": "1b7521aa-cee4-52e9-9f43-7a46d9c5ca43"
}