Cytotoxic T lymphocytes (CTL) mediate immunity to intracellular infections and tumors by directly killing infected or aberrant cells by delivering pro-apoptotic granzyme proteases into the cytoplasm of target cells via the pore-forming protein Perforin. During an immune response, stimulation of T cell antigen receptors (TCR) on antigen-specific naive CD8+ T cells initiates their exponential accumulation and differentiation into cells that upregulate Perforin and granzymes. Near the peak response, most responding cells in the circulation comprise terminal effector (TE) CTL, but these cells have short half-lives after the acute immune challenge is resolved. A smaller fraction comprises memory precursor (MP) effector CTL that efficiently give rise to long-lived memory CTL, which reside in lymphoid tissue as TCN and that provide a stem cell-like memory reservoir that regenerates immune responses upon re-challenge.. In addition, a fraction of CTL differentiate into cells that depart the general circulation and lodge in non-lymphoid tissues where they persist long-term as TRM (tissue-resident memory) and provide immediate protection in situ at the surfaces where infections and solid tumors originate. Until now, the molecules and mechanisms that remodel chromatin structure and transcriptional programs that drive activated CD8+ T cells to differentiate into TCM (central memory) and TRM (tissue-resident memory ) CTL, and ensure they do not "skew" into TE CTL which do not persist, were virtually unknown.
Researchers at UC San Diego have developed methods to modify activated CD8+ T cells epigenetically, to induce their differentiation into TCM and TRM CD8+ CTLs by controlling expression of Runt-family transcription factors in either endogenous or adoptively transferred T cells. In its simplest form, the invention comprises a retroviral vector encoding the murine Runx3 cDNA which is used to transduce naive, briefly activated antigen-specific CD8 T cells. These cells are then applied by infusing them back into either infected or tumor-bearing hosts. We demonstrate that by enhancing Runx3 expression in tumor-specific CTLs and using these cells in adoptive cell therapy models in mice, the transferred CTLs more efficiently invade and destroy established melanoma tumors, conferring longer survival.
The utility of the invention lies in engineering durable immunity to infections and tumors by tuning the differentiated states of CTL and/or their activity at the chromatin-level to stably promote their functional potential in situ as TRM cells that colonize non-lymphoid tissues and that more efficiently infiltrate solid tumors. Additional applications include gene-editing of endogenous Runx-gene loci in ex vivo human T cells that are used in adoptive T cell (ACT) therapies, and in chimeric antigen receptor (CAR) T cell therapies. Not only that, the combination of immune checkpoint inhibitor therapies (e.g. anti_PD-1, anti-CTLA4, etc.) with this RunX-based therapy may increase the low response rate observed today with immunotherapies alone or immunotherapies combined with chemotherapeutic agents.
The proposed invention represents a first-in-kind tool to alter epigenetically the differentiation of CTL in the context of ACT, CART, and potentially, endogenous T cell therapies. It provides the first example of engineering CTL differentiation to promote the natural properties that accentuate both non-lymphoid tissue homing and accumulation within solid tumors, as well as, long-term persistence in of memory T cells in lymphoid tissues.
A prototype in which murine Runx3 is expressed from an MLV-based ecotropic retrovirus has been developed, applied and validated in vivo, in mice. Multiple mutant murine Runx3 analogs, and the human RUNX3 ortholog, have been generated and are currently under investigation to discover whether and how altered Runx3 forms might provide additional gain-of-function in vivo.
This technology is patent pending and available for licensing and/or research sponsorship.
Tissue-resident memory CD8+ T cells (TRM), Runx3 transcription factor, effector memory T cells (TEM), cytotoxic T lymphocytes (CTL), adoptive cell therapy, T cell therapy, combined immune checkpoint inhibitor therapies, anti-PD-1, anti-CTLA4