Studies of the SARS-CoV-2 Spike Protein

Division Of Basic Sciences - Nci

Investigators

Linked publications, trials & patents

Abstract

Due to the recent initiation of this project (April 2020) during the partial lab closure during the pandemic, progress on the objectives listed above has been limited, although 2 papers have been published already. In vitro studies in macaque bronchioalveolar lavage cells: So far, we have seen some effects in vitro on these cells of stimulating them with recombinant spike protein to affect expression of ACE2 and of interferons, that may play a role in infection. Little effect was seen on other cytokine or chemokine production. We recently published that S1 protein acts on macaque lung bronchoalveolar lavage cells to downregulate expression of the ACE2 receptor and also inhibit type I interferon production. Type I interferons have been shown to be essential for protection against SARS-CoV-2, and ACE2, besides being a receptor for spike protein, also protects the lung against respiratory viruses by cleaving angiotensin II, so downregulating these could worsen COVID-19. In vivo vaccine studies in macaques: Rhesus macaques have been primed IM with spike in different adjuvants and boosted systemically with spike in alum or mucosally intranasally with spike in nanoparticles with IL-15 and TLR ligand adjuvants. We have found and recently published that nanoparticles containing S1 spike protein delivered intranasally can boost macaques primed IM with S1 in alum and result in better protection against respiratory challenge with SARS-CoV-2 than can the IM vaccine alone even though the S1-binding and neutralizing antibody levels are lower. Other mechanisms must play a role and we have found correlations with mucosal IgA, dimeric IgA, and type I interferon production in the lung, and certain types of myeloid cells. We are now testing a mucosal nanoparticle boost with the B1.351 (South African) variant S1 protein to protect against this SARS-CoV-2 variant in macaques. Early results are promising for protection against variants. These studies suggest that a human intranasal nanoparticle COVID-19 vaccine given to people who had been previously immunized systemically with one of the approved vaccines, could improve protection against infection and reduce the risk of forward transmission to others by reducing intranasal virus, which is especially a problem with the new delta variant. In vivo studies in mice: ACE2-transgenic mice have been purchased despite delays, and are being bred. In wild type B6 mice, we have immunized with recombinant spike protein S1, S1+S2, or RBD in several different adjuvants to determine the best formulation. The best combination so far is IL-15 + ligands for TLR3 and 9, for both antibody and T cell responses. That work is in progress. The DNA vaccine with spike protein coupled to a chemokine is being constructed and that work is in progress. Human cell lines: We have received the immortalized human lung epithelial cell lines, that express ACE2, from John Minna at UTSW, as well as some of his non-small-cell lung cancer cell lines that also express ACE2. We have obtained an antibody to ACE2 to verify expression. Initial results show that omega-3 fatty acids and cholesterol differentially affect ACE2 expression on lung cancer cells as well as TMPRSS2 expression and may help explain how diet and obesity as well as lung cancer can affect susceptibility to SARS-CoV-2.