van Diest, E. | bioRxiv Science

bioRxiv2021

Challenges of γ9δ2TCR affinity maturation when using phage display

BackgroundOver the past years we showed that the efficacy of {beta}T cells engineered to express a defined {gamma}{delta}TCR (TEG) depends on the functional avidity of the {gamma}9{delta}2TCR. We hypothesized that functional avidity mediated through {gamma}9{delta}2TCR in the TEG format could be further enhanced by increasing affinity of the {gamma}9{delta}2TCR. MethodsWe attempted to overcome limited affinity of natural occurring {gamma}9{delta}2TCRs through affinity maturation by phage display using a library containing mutations in CDR1 and CDR2 of both TCR chains. ConclusionAffinity maturation of {gamma}9{delta}2TCR by using phage display was not successful. The largest hurdle was the periplasmic expression of {gamma}9{delta}2TCR constructs in E.coli which is a prerequisite for successful phage display. The underlying reason for this lack of expression was the instability of the single chain (sc)TCR format. Expression of scTCR formats in HEK293F cells yielded only 15-20% correctly folded scTCR.

immunology↗

bioRxiv2021

Enhancing cancer targeting of γ9δ2TCR through modified NKG2D co-stimulation

Despite the ability of {gamma}{delta}T cells to mediate tumor killing independently of MHC recognition, all the clinical trials that have been carried out using these cells showed low response rate in patients, in part due to its poor proliferation ability. Recently, a new generation of CAR-T cells called {beta}T cells engineered to express a defined {gamma}{delta}TCR (TEG) has been developed. TEGs are {beta}T cells engineered to express a defined {gamma}{delta}TCR. These cells are able to mediate effective antitumor reactivity without showing any reactivity towards healthy tissue, and combine the best qualities of both {beta}T and {gamma}{delta}T cells. In fact, the high affinity {gamma}9{delta}2TCR clone 5 has recently been selected within the TEG format as a clinical candidate (TEG001). Here we present a strategy to improve the antitumor activity of TEG001 by co-expressing an activating chimeric co-receptor together with {gamma}{delta}TCR-Cl5.Therefore, we developed three different co-receptors by fusing the extracellular domain of the activating cell surface receptor NKG2D, that is able to bind stress induced ligands typically expressed on tumor cells, to the cytoplasmic signaling domains of the T cell costimulatory proteins ICOS, CD28 and 4-1BB. We determined that introduction of the chimeric co-receptors NKG2D-CD28wt and NKG2D-4-1BBCD28TM improved the activity of TEG001 against tumors that were recognized by {gamma}{delta}TCR-Cl5 and expressed NKG2D ligands, but did not affect tumors that either were not recognized by {gamma}{delta}TCR-Cl5 or did not express NKG2D ligands. This chimeric co-receptors approach open a wide range of opportunities that lead to a next generation of TEGs.

immunology↗