370 Identification and validation of a T cell receptor recognizing shared HLA-A02:01 presented epitope from TP53 frameshift

Regular and Young Investigator Award Abstracts, pp. A426

Abstract

Background The recognition of epitopes derived from tumor antigens via T cell receptors (TCR) of T cells is prerequisite for efficient tumor cell destruction. One of the limiting factors in T cell-mediated immunotherapy is the availability of shared targets highly expressed on tumor cells and absent from healthy tissue. Neo-open reading frame peptides (NOPs) arising from insertions or deletions in tumor DNA are a class of antigens providing opportunities for designing T cell receptor therapies. Methods NOPs were predicted for all patients in The Cancer Genome Atlas and binding of NOP-derived epitopes was predicted for HLA-A*02:01 allele. The top 30 predicted binding epitopes were used to make HLA-A*02:01 fluorescently labeled tetramers. Peripheral blood mononuclear cells of multiple healthy donors were incubated with pooled peptide loaded tetramers. Tetramer positive cells were further expanded and enriched for antigen specific CD8+ T cells which were used to identify the alpha and beta chains of TCR. Either in vitro expanded or TCR engineered CD8+ T cells were used in co-culture assays with either cells overexpressing selected NOP of interest or with cell lines naturally expressing the same antigen. Additionally, mRNA construct encoding a NOP was used to transfect human monocyte-derived dendritic cells (moDC) and the epitope presentation was detected by co-culture with in vitro expanded antigen specific CD8 T cells. The activation of antigen specific CD8+ T cells was detected by increased CD137 and CD107a expression. The engineered T cells were tested in a dose titration experiment to assess the TCR affinity. Results The in vitro expansion of antigen specific CD8 T cells recognizing HLA-A*02:01 bound peptides derived from NOPs was successful for 15 peptides. Out of all in vitro expanded CD8+ T cell populations, only 2 recognized their cognate peptide presented in the context of HLA-A*02:01 allele. One of the TCRs recognized an epitope derived from TP53 NOP. This TCR was cloned into naïve CD8+ T cells of a healthy donor which specifically recognized naturally expressed and presented TP53 NOP peptide in all tested models, including mRNA transfected moDC. Conclusions We identified and validated a TCR recognizing an HLA-A*02:01 epitope from TP53 NOP. TP53 NOP is expressed in 1–3% of patients across multiple cancer types. This study shows feasibility of identifying targets for shared T cell therapies.

Authors 10

1. Michael V. Martin
   Affiliation as printed

   CureVac Netherlands B.V., Amsterdam, Netherlands

2. Saskia J A M Santegoets Aachen

   Leiden University Medical Center

   Affiliation as printed

   Leiden University Medical Center, Leiden, Netherlands

3. Jamie van Langelaar
   Affiliation as printed

   CureVac Netherlands B.V., Amsterdam, Netherlands

4. Wim van Esch
   Affiliation as printed

   CureVac Netherlands B.V., Amsterdam, Netherlands

5. Hugo Olsman
   Affiliation as printed

   CureVac Netherlands B.V., Amsterdam, Netherlands

6. Finn Edwards
   Affiliation as printed

   CureVac Netherlands B.V., Amsterdam, Netherlands

7. Anouk Stolk Aachen

   Leiden University Medical Center

   Affiliation as printed

   Leiden University Medical Center, Leiden, Netherlands

8. Wigard P. Kloosterman
   Affiliation as printed

   CureVac Netherlands B.V., Amsterdam, Netherlands

9. Sjoerd van der Burg Aachen

   Leiden University Medical Center

   Affiliation as printed

   Leiden University Medical Center, Leiden, Netherlands

10. Katka Franke
    Affiliation as printed

    CureVac Netherlands B.V., Amsterdam, Netherlands