A stable platform for the production of virus-like particles pseudotyped with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spike protein

In this study, we showed that a codon optimized version of the spike (S) protein of SARS-CoV-2 can migrate to the cell membrane. However, efficient production of Moloney murine leukemia (MLV) infectious viral particles was only achieved with stable expression of a shorter S version in C-terminal (Delta S) in MLV Gag-pol expressing cells. As compared to transient transfections, this platform generated viruses with a 1000-fold higher titer. Delta S was 15-times more efficiently incorporated into VLPs as compared to S, and that was not due to steric inter-ference between the cytoplasmic tail and the MLV capsid, as similar differences were also observed with extracellular vesicles. The amount of Delta S incorporated into VLPs released from producer cells was high and estimated at 1.25 mu g/mL S2 equivalent (S is comprised of S1 and S2). The resulting VLPs could potentially be used alone or as a boost of other immunization strategies for COVID-19.