SARS CoV-2 nucleoprotein enhances the infectivity of lentiviral spike particles

The establishment of SARS CoV-2 spike-pseudotyped lentiviral (LV) systems has enabled the rapid identification of entry inhibitors and neutralizing agents, alongside allowing for the study of this emerging pathogen in BSL-2 level facilities. While such frameworks recapitulate the cellular entry process in ACE2+ cells, they are largely unable to factor in supplemental contributions by other SARS CoV-2 genes. To address this, we performed an unbiased ORF screen and identified the nucleoprotein (N) as a potent enhancer of spike-pseudotyped LV particle infectivity. We further demonstrate that this augmentation by N renders LV spike particles less vulnerable to the neutralizing effects of a human IgG-Fc fused ACE2 microbody. Biochemical analysis revealed that the spike protein is better enriched in virions when the particles are produced in the presence of SARS CoV-2 nucleoprotein. Importantly, this improvement in infectivity is achieved without a concomitant increase in sensitivity towards RBD binding-based neutralization. Our results hold important implications for the design and interpretation of similar LV pseudotyping-based studies.