Biology subjects

Mansouri, K.

Publications and source records attributed to Mansouri, K..

24 records · Page 2Linked to original sources

bioRxiv2020

Cold sensitivity of the SARS-CoV-2 spike ectodomain

The SARS-CoV-2 spike (S) protein, a primary target for COVID-19 vaccine development, presents its Receptor Binding Domain in two conformations: receptor-accessible "up" or receptor-inaccessible "down" conformations. Here, we report that the commonly used stabilized S ectodomain construct "2P" is sensitive to cold temperature, and that this cold sensitivity is resolved in a "down" state stabilized spike. Our results will impact structural, functional and vaccine studies that use the SARS-CoV-2 S ectodomain.

biochemistry↗

bioRxiv2020

A glycan cluster on the SARS-CoV-2 spike ectodomain is recognized by Fab-dimerized glycan-reactive antibodies

SummaryThe COVID-19 pandemic caused by SARS-CoV-2 has escalated into a global crisis. The spike (S) protein that mediates cell entry and membrane fusion is the current focus of vaccine and therapeutic antibody development efforts. The S protein, like many other viral fusion proteins such as HIV-1 envelope (Env) and influenza hemagglutinin, is glycosylated with both complex and high mannose glycans. Here we demonstrate binding to the SARS-CoV-2 S protein by a category of Fab-dimerized glycan-reactive (FDG) HIV-1-induced broadly neutralizing antibodies (bnAbs). A 3.1 Å resolution cryo-EM structure of the S protein ectodomain bound to glycan-dependent HIV-1 bnAb 2G12 revealed a quaternary glycan epitope on the spike S2 domain involving multiple protomers. These data reveal a new epitope on the SARS-CoV-2 spike that can be targeted for vaccine design.HighlightsFab-dimerized, glycan-reactive (FDG) HIV-1 bnAbs cross-react with SARS-CoV-2 spike.3.1 Å resolution cryo-EM structure reveals quaternary S2 epitope for HIV-1 bnAb 2G12.2G12 targets glycans, at positions 709, 717 and 801, in the SARS-CoV-2 spike.Our studies suggest a common epitope for FDG antibodies centered around glycan 709.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2020

Fab-dimerized glycan-reactive antibodies neutralize HIV and are prevalent in humans and rhesus macaques

SummaryThe HIV-1 envelope (Env) is comprised by mass of over 50% glycans. A goal of HIV-1 vaccine development is the induction of Env glycan-reactive broadly neutralizing antibodies (bnAbs). The 2G12 bnAb recognizes an Env glycan cluster using a unique variable heavy (VH) domain-swapped conformation that results in fragment antigen-binding (Fab) dimerization. Here we describe Fab-dimerized glycan (FDG)-reactive antibodies without VH-swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques that neutralized heterologous HIV-1 isolates. FDG precursors were boosted by vaccination in macaques, and were present in HIV-1-naïve humans with an average estimated frequency of one per 340,000 B cells. These data demonstrate frequent HIV-1 Env glycan-reactive bnAb B cell precursors in macaques and humans and reveal a novel strategy for their induction by vaccination.HighlightsDiscovery of Fab-dimerized HIV-1 glycan-reactive antibodies with a non-domain-swapped architectureFab-dimerized antibodies neutralize heterologous HIV-1 isolates.Antibodies with this architecture can be elicited by vaccination in macaques.Fab-dimerized antibodies are found in HIV-1 naïve humans.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2020

Glycans on the SARS-CoV-2 Spike Control the Receptor Binding Domain Conformation

The glycan shield of the beta-coronavirus (β-CoV) Spike (S) glycoprotein provides protection from host immune responses, acting as a steric block to potentially neutralizing antibody responses. The conformationally dynamic S-protein is the primary immunogenic target of vaccine design owing to its role in host-cell fusion, displaying multiple receptor binding domain (RBD) ‘up’ and ‘down’ state configurations. Here, we investigated the potential for RBD adjacent, N-terminal domain (NTD) glycans to influence the conformational equilibrium of these RBD states. Using a combination of antigenic screens and high-resolution cryo-EM structure determination, we show that an N-glycan deletion at position 234 results in a dramatically reduced population of the ‘up’ state RBD position. Conversely, glycan deletion at position N165 results in a discernable increase in ‘up’ state RBDs. This indicates the glycan shield acts not only as a passive hinderance to antibody meditated immunity but also as a conformational control element. Together, our results demonstrate this highly dynamic conformational machine is responsive to glycan modification with implications in viral escape and vaccine design.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biophysics↗

bioRxiv2020

Controlling the SARS-CoV-2 Spike Glycoprotein Conformation

The coronavirus (CoV) viral host cell fusion spike (S) protein is the primary immunogenic target for virus neutralization and the current focus of many vaccine design efforts. The highly flexible S-protein, with its mobile domains, presents a moving target to the immune system. Here, to better understand S-protein mobility, we implemented a structure-based vector analysis of available {beta}-CoV S-protein structures. We found that despite overall similarity in domain organization, different {beta}-CoV strains display distinct S-protein configurations. Based on this analysis, we developed two soluble ectodomain constructs in which the highly immunogenic and mobile receptor binding domain (RBD) is locked in either the all-RBDs down position or is induced to display a previously unobserved in SARS-CoV-2 2-RBDs up configuration. These results demonstrate that the conformation of the S-protein can be controlled via rational design and provide a framework for the development of engineered coronavirus spike proteins for vaccine applications.

immunology↗

bioRxiv2020

Interaction of intraocular pressure and ganglion cell function in open angle glaucoma

PurposeTo test the feasibility of simultaneous steady-state pattern electroretinogram (PERG) and intraocular pressure (IOP) measurements with an IOP sensor and to test a model for IOP manipulation during lateral decubitus positioning (LDP) and its impact on the PERG. DesignA prospective, observational study. Methods15 healthy controls and 15 treated glaucoma patients participated in the study. 8 patients had an intraocular IOP sensor (eyemate-IO(R), Implandata Ophthalmic Products GmbH) in the right eye (GLAIMP) and 7 had no sensor and with glaucoma in the left eye. (1) We tested the feasibility of simultaneous IOP and PERG recordings by comparing PERGs with and without simultaneous IOP-read out in GLAIMP. (2) All participants were positioned in the following order: sitting1 (S1), right LDP (LDR), sitting2 (S2), left LDP (LDL) and sitting3 (S3). For each position, PERG amplitudes and IOP were determined with rebound tonometry (Icare(R) TA01i) in all participants without the IOP sensor. ResultsElectromagnetic intrusions of IOP sensor readout onto steady-state PERG-recordings had, due to different frequency ranges, no relevant effect on PERG amplitudes. IOP and PERG measures were affected by LDP, e.g., IOP was increased during LDR vs S1 in the lower eyes of GLAIMP and controls (P < 0.001 and P < 0.05, respectively) and PERG amplitude was decreased (P < 0.05 and P < 0.01, respectively). ConclusionsDuring LDP, IOP and PERG measurements changed more in the lower eye. IOP changes induced by LDP may be a model for studying the interaction of IOP and ganglion cell function.

neuroscience↗