Screening scaffold proteins for improved functional delivery of luminal proteins using engineered extracellular vesicles

The potential for engineered extracellular vesicles (EVs) to efficiently deliver biotherapeutics is still largely untapped. One of the key structures in determining cargo loading and subsequent functional delivery efficiency of engineered EVs is the sorting protein (scaffold). To determine the role of scaffold protein identity, a functional screen of scaffold proteins for efficient cargo delivery is required. Here, we applied the VEDIC (VSV-G plus EV-sorting Domain-Intein-Cargo) system, previously developed by our group, for the functional screen of 55 different scaffold proteins. Three tetraspanins (TSPAN2, TSPAN4 and TSPAN9) were identified that demonstrate enhanced intracellular delivery of cargo when compared to traditionally used CD63. We further explored the in vivo and ex vivo protein delivery performance of the best performing engineered EVs (TSPAN2) using melanoma xenografts and isolated primary cells from Cre-LoxP R26-LSL-tdTomato reporter mice, respectively. Finally, we report successful treatment of LPS-induced systemic inflammation by delivering a super-repressor inhibitor of NF-ĸB using TSPAN2 engineered EVs. This work highlights the importance of screening critical EV engineering elements, such as the scaffold protein, to modulate EV properties.