gamma delta TCR immunoglobulin constant region domain exchange in human alpha beta TCRs improves TCR pairing without altering TCR gene-modified T cell function

摘要

The adoptive genetic transfer of T cell receptors (TCRs) has been shown to be overall feasible and offer clinical potential as a treatment for different types of cancer. However, this promising clinical approach is limited by the serious potential consequence that exogenous TCR mispairing with endogenous TCR chains may lead to the risk of self-reactivity. In the present study, domain-exchange and three-dimensional modeling strategies were used to create a set of chimeric TCR variants, which were used to exchange the partial or complete constant region of alpha beta TCR with corresponding gamma delta TCR domains. The expression, assembly and function of the chimeric TCR variants were examined in Jurkat T cells and peripheral mononuclear blood cells (PBMCs). Genetically-encoded chimeras were fused with a pair of fluorescent proteins (ECFP/EYFP) to monitor expression and the pairing between chimeric TCR alpha chains and TCR beta chains. The fluorescence energy transfer based on confocal laser scanning microscopy showed that the introduction of gamma delta TCR constant sequences into the alpha beta TCR did not result in a global reduction of mispairing with endogenous TCR. However, the TCR harboring the immunoglobulin-like domain of the gamma delta TCR constant region (i.e., TCR Delta IgC), showed a higher expression and preferential pairing, compared with wild-type (wt) TCR. The function analysis showed that TCR Delta IgC exhibited the same levels of interferon-gamma production and cytotoxic activity, compared with wtTCR. Furthermore, these modified TCR-transduced T cells retained the classic human leukocyte antigen restriction of the original TCR. The other two chimeric TCRs, had either exchange of the cp+tm+ic domain or exchange of the whole C domain (Fig. 1). Ultimately, exchange of these domains demonstrated defective function in the transduced T cells. Taken together, these findings may provide further understanding of the gamma delta TCRd constant domain with implications for the improvement of TCR gene transfer therapy.