Extracellular vesicles (EVs) have recently emerged as a highly promising cell-free bio-therapeutics. While a range of engineering strategies have been developed to functionalize the EV surface, current approaches fail to address the limitations associated with endogenous surface display, pertaining to the heterogeneous display of commonly used EV-loading moieties among different EV subpopulations. Karolinska Institutet researchers present a novel engineering platform to display multiple protein therapeutics simultaneously on the EV surface. As proof-of-concept, the researchers screened multiple endogenous display strategies for decorating the EV surface with cytokine binding domains derived from tumor necrosis factor receptor 1 (TNFR1) and interleukin 6 signal transducer (IL6ST), which can act as decoys for the pro-inflammatory cytokines TNFα and IL6, respectively. Combining synthetic biology and systematic screening of loading moieties, resulted in a three-component system which increased the display and decoy activity of TNFR1 and IL6ST, respectively. Further, this system allowed for combinatorial functionalization of two different receptors on the same EV surface. These cytokine decoy EVs significantly ameliorated disease phenotypes in three different inflammatory mouse models for systemic inflammation, neuroinflammation, and intestinal inflammation. Importantly, significantly improved in vitro and in vivo efficacy of these engineered EVs was observed when compared directly to clinically approved biologics targeting the IL6 and TNFα pathways.
Systematic screening of multiple endogenous EV display strategies for cytokine decoys
A) Schematic illustration showing the generation of engineered decoy EVs at the cellular level. Producer cells are genetically modified to express cytokine receptors without the signalling domain fused to an EV sorting domain for efficient display of cytokine receptors on the surface of the secreted EVs (decoy EVs), which can decoy cytokines specifically. B) and C) Schematic illustrations of the evolution of cytokine receptors to facilitate EV surface display and assessment of various designs in a cytokine induced reporter cell system for high throughput screening of TNFR1 and IL6ST decoy EVs. D) and E) List of various TNFR1 or IL6ST sorting domain fusions assessed in the initial screen. F) Engineered decoy EVs displaying TNFR1 purified from HEK293T cells transfected with the constructs encoding the different display constructs (Figure1D) evaluated for TNFα decoy in an in vitro cell assay responsive to TNFα induced NF-κB activation. Data were normalized to control cells treated with TNFα only (5 ng/ml). G) Engineered EVs displaying IL6ST purified from HEK293T cells transfected with constructs encoding the different display constructs (Figure1G) evaluated for IL6/sIL6R decoy in an in vitro cell assay respondent to IL6/sIL6R induced STAT3 activation. Data were normalized to control cells treated with IL6/sIL6R (5 ng/ml). F, G, Error bars, s.d. (n = 3), **** P < 0.0001, *** P < 0.001, ** P < 0.01, statistical significance calculated by two-way ANOVA with Dunnett’s post-test compared with response of Ctrl EVs at the respective dose.