Engineering a streamlined virus-like particle for programmable tissue-specific gene delivery.

Transient gene delivery vehicles have emerged as crucial tools in biomedicine, among them, virus-like particles (VLPs) stand out for their unique characteristics, yet the limited tropisms hinder their widespread applications. VLPs have potential to broaden their targeting range through the acquisition of programmable tropisms, however, current retrovirus-based VLPs pose engineering challenges due to multiple viral proteins. Here, we streamline the VLP system by customizing a backbone utilizing positive-strand Semliki Forest Virus (SFV) for a programmable VLP vector, minimizing virus-derived composition. The vector accommodates mRNA, protein, or ribonucleoprotein (RNP) cargos, supporting mRNA ranging from 500 bp to 10 kb. Through the engineering of the envelope protein (Env) via rational peptide insertion or pseudotyping with other fusogens, we generate VLP candidates exhibiting enhanced in vivo blood-brain barrier (BBB) penetration, expanded in vitro targeting ranges and the ability to escape neutralizing antibodies (Nab), or muscle-targeting capabilities. The programmable engineering capabilities and customizable tropisms provide the possibility and flexibility to be tailored for diverse treatment strategies in the future.