(454c) Remote Control of Engineered T Cells Using Photothermal Pulses

Remote
Control of Engineered T Cells Using Photothermal Pulses

Ian
C. Miller, Marielena
Gamboa Castro, Lee-Kai Sun, Jason P. Weis and Gabriel A. Kwong

Georgia
Institute of Technology and Emory School of Medicine

Introduction:  Recent advances in synthetic biology are
providing new tools to modulate cellular activity and elucidate complex
signaling pathways in T cells.  These include the ability to redirect T cell
specificity towards cancer-associated antigens, migrate towards synthetic
chemical cues, or sense combinatorial antigens using Boolean logic.  Yet
despite such striking progress, our ability to precisely control the activity
of engineered T cells in vivo remains limited. This issue is a barrier
to widespread application of T cell therapies in solid tumors and has raised safety
concerns stemming from off-target toxicity in healthy tissues. The next generation
of engineered T cells that can be remotely controlled by external cues, such as
light or heat, will enhance the field’s ability to dictate cellular behavior to
augment anti-tumor immune activity. We leverage the precision with which heat
can be spatially targeted by photothermal pulses, and engineer T cells with
thermal gene switches which are constructed from the heat shock protein HSPA6
promoter (Fig. 1a). Using localized heating, we trigger gene expression
of engineered T cells to levels 200-fold over basal activity in mice. 
Additionally, we show that delivery of heat as thermal pulse trains increases T
cell thermal tolerance compared to continuous heating profiles with identical
areas-under-the-curve (AUC). In the future, this strategy could increase the
safety and potency of engineered T cell therapies for cancer.

Results and
Discussion:  To
construct a thermal gene switch, we identified a construct of the HSPA6 promoter
with low basal activity and strong heat induction, and characterized its
response to mild hyperthermia (40 – 42 °C) in Jurkat T cells (Fig. 1b,c).
We also used NIR laser light and injected gold nanorods to precisely heat
targeted sites in vivo and increase translational activity of engineered
cells greater than 200-fold (Fig. 1d,e,f). Heating samples using pulse
trains, in contrast to continuous heating profiles, increased thermal tolerance
of T cells (Fig. 1g) and enabled long-term remote control over cellular
activity in vivo (Fig. 1h). Accordingly, this platform may be
used to augment the therapeutic efficacy of engineered T cells in clinical
settings.

Conclusion:  Using photothermal activation of
thermal bioswitches, we controlled the translational activity of engineered
cells in vivo. Looking forward, this platform could enable precise
control over cellular behavior with exquisite spatial resolution and provide an
orthogonal mechanism to dictate cellular activity in addition to small-molecule
or light-based methods.