Ramdas, P. | bioRxiv Science

bioRxiv2021

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.

microbiology↗

bioRxiv2020

Coevolution of retroviruses with SERINCs following whole-genome duplication divergence

The SERINC gene family comprises of five paralogs in humans of which SERINC3 and SERINC5 inhibit HIV-1 infectivity and are counteracted by Nef. The origin of this anti-retroviral activity, its prevalence among the remaining paralogs, and its ability to target retroviruses remain largely unknown. Here we show that despite their early divergence, the anti-retroviral activity is functionally conserved among four human SERINC paralogs with SERINC2 being an exception. The lack of activity in human SERINC2 is associated with its post-whole genome duplication (WGD) divergence, as evidenced by the ability of pre-WGD orthologs from yeast, fly, and a post-WGD-proximate SERINC2 from coelacanth to inhibit nef-defective HIV-1. Intriguingly, potent retroviral factors from HIV-1 and MLV are not able to relieve the SERINC2-mediated particle infectivity inhibition, indicating that such activity was directed towards other retroviruses that are found in coelacanth (like foamy viruses). However, foamy-derived vectors are intrinsically resistant to the action of SERINC2, and we show that a foamy virus envelope confers this resistance. Despite the presence of weak arms-race signatures, the functional reciprocal adaptation among SERINC2 and SERINC5 and, in response, the emergence of antagonizing ability in foamy virus appears to have resulted from a long-term conflict with the host.

microbiology↗