A Mammalian Surface Display Platform to Optimize the Antigenicity of Viral Proteins for Vaccine Design

Vaccine development often involves modifying native viral proteins to enhance their stability and antigenicity, as seen in approved Covid-19 vaccines and multiple HIV vaccine candidates currently under investigation. High throughput screening on the surface of mammalian cells enables the rapid evaluation of oligomeric, glycosylated viral proteins and the identification of mutations that improve their properties for vaccine design. Here, we developed an experimental platform that uses the PiggyBac transposon system to display libraries of viral protein variants on the surface of mammalian cells for efficient screening. This approach addresses common challenges in existing mammalian display systems, including low transfection efficiency and the development of stable cell lines for iterative selection rounds. The new platform was validated by expressing and characterizing antigenically diverse viral proteins from influenza, SARS-CoV-2, and HIV. In a further application, library screening of influenza haemagglutinin libraries identified mutations that increased binding of broadly cross-reactive antibodies to a conserved, but partially occluded, epitope of interest for the development of a universal influenza vaccine. These results demonstrate the potential of this mammalian display platform to rapidly engineer immunogens with desired antigenic properties for vaccine design.