Nanobodies agains Sars Cov 2 Nsp9 protein protects cells from virus infection

Nanobodies are emerging as ideal instruments for drug design and several have recently been created to block SARS-Cov-2 entry in the host cell by targeting surface-exposed Spike protein. However, due to the high frequency of mutations that affect Spike, these nanobodies may not efficiently target Spike during viral entry. Here we have established a pipeline that instead targets highly conserved viral proteins that are made only after viral entry into the host cell when the SARS-Cov-2 RNA-based genome is translated. As proof of principle, we designed nanobodies against the SARS-CoV-2 non-structural protein Nsp9, required for replication of the viral genome. To find out if this strategy efficiently blocked viral replication, one of these anti-Nsp9 nanobodies, 2NSP23, previously characterized using immunoassays and NMR spectroscopy for epitope mapping, was encapsulated into lipid nanoparticles (LNP) as mRNA. We show that this nanobody, hereby referred to as LNP-mRNA-2NSP23, is internalized and translated in HEK293 cells. We next infected HEK293-ACE2 cells subjected to LNP-mRNA-2NSP23 with multiple SARS-CoV-2 variants. Analysis of total RNA isolated form infected cells treated or untreated with LNP-mRNA-2NSP23 using qPCR and RNA deep sequencing shows that the LNP-mRNA-2NSP23 nanobody protects HEK293-ACE2 cells and suppresses replication of several SARS-CoV-2 variants. These observations indicate that following translation, the nanobody 2NSP23 inhibits viral replication by targeting Nsp9 in living cells. We propose that LNP-mRNA-2NSP23 may be translated into an innovative technology to generate novel antiviral drugs highly efficient across coronaviruses. RNA seq analysis of 293T cells treated with lipid nanoparticles containing control dTomato (LNP45) or Nsp9 nanobody mRNA (LNP23) which are subsequently infected with different variants of Sars Cov 2 virus