Genetic manipulation of human T cells for use in adoptive T cell therapy
Sonja Haupt*, Rebecca Brownlie, Rose Zamoyska
Institute for Immunology and Infection Research, Ashworth Laboratories, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
Treatment of cancer has considerably progressed in the past years with the introduction of adoptive T cell therapy and immune checkpoint blockade. A variety of cancers have been targeted using T cells that have been engineered to express tumor-specific T cell receptors (TCRs) or chimeric antigen receptors and some remarkable responses have been reported. Together with recent advances in the use of checkpoint inhibitors these studies indicate that long term remission or cure may be achieved by activating anti-tumor T cell responses. Despite these encouraging results, persistence of disease has consistently been observed in a subset of patients, so there is room for improvement.
We have taken the novel approach of modifying intracellular signaling molecules to improve anti-tumor T cells for therapy. The cytoplasmic tyrosine phosphatase PTPN22 is a negative regulator of TCR signaling and a polymorphism in the gene has been identified as a risk factor for autoimmunity. Autoimmune T cells have many characteristics that are desirable in anti-tumor T cells. Using a Ptpn22-/- mouse model, we showed that Ptpn22-/- CD8 T cells are superior at clearing established tumors because they respond better to weak antigens and are resistant to suppression by Treg cells and TGF-β. Ptpn22-/- T cells showed increased proliferation and greater production of effector cytokines. This data suggest that engineering human T cells to lack PTPN22 expression is a viable strategy to improve T cell therapy. To test this hypothesis, we transduced primary human peripheral PBMC T cells with TCRs specific for a defined antigen and used the CRISPR/Cas9 system to delete PTPN22 protein expression. We achieved up to 30% knockout of PTPN22 alleles, demonstrated by reduced protein expression by intracellular staining. The PTPN22-/- T cells will be tested for improved responses to weak antigens and resistance to tumor suppressive environment.