Biology subjects

Muecksch, F.

Publications and source records attributed to Muecksch, F..

5 recordsLinked to original sources

bioRxiv2020

Escape from neutralizing antibodies by SARS-CoV-2 spike protein variants

Neutralizing antibodies elicited by prior infection or vaccination are likely to be key for future protection of individuals and populations against SARS-CoV-2. Moreover, passively administered antibodies are among the most promising therapeutic and prophylactic anti-SARS-CoV-2 agents. However, the degree to which SARS-CoV-2 will adapt to evade neutralizing antibodies is unclear. Using a recombinant chimeric VSV/SARS-CoV-2 reporter virus, we show that functional SARS-CoV-2 S protein variants with mutations in the receptor binding domain (RBD) and N-terminal domain that confer resistance to monoclonal antibodies or convalescent plasma can be readily selected. Notably, SARS-CoV-2 S variants that resist commonly elicited neutralizing antibodies are now present at low frequencies in circulating SARS-CoV-2 populations. Finally, the emergence of antibody-resistant SARS-CoV-2 variants that might limit the therapeutic usefulness of monoclonal antibodies can be mitigated by the use of antibody combinations that target distinct neutralizing epitopes.

microbiology↗

bioRxiv2020

Measuring SARS-CoV-2 neutralizing antibody activity using pseudotyped and chimeric viruses

The emergence of SARS-CoV-2 and the ensuing explosive epidemic of COVID19 disease has generated a need for assays to rapidly and conveniently measure the antiviral activity of SARS-CoV-2-specific antibodies. Here, we describe a collection of approaches based on SARS-CoV-2 spike-pseudotyped, single-cycle, replication-defective human immunodeficiency virus type-1 (HIV-1) and vesicular stomatitis virus (VSV), as well as a replication-competent VSV/SARS-CoV-2 chimeric virus. While each surrogate virus exhibited subtle differences in the sensitivity with which neutralizing activity was detected, the neutralizing activity of both convalescent plasma and human monoclonal antibodies measured using each virus correlated quantitatively with neutralizing activity measured using an authentic SARS-CoV-2 neutralization assay. The assays described herein are adaptable to high throughput and are useful tools in the evaluation of serologic immunity conferred by vaccination or prior SARS-CoV-2 infection, as well as the potency of convalescent plasma or human monoclonal antibodies.

microbiology↗

bioRxiv2020

Structures of human antibodies bound to SARS-CoV-2 spike reveal common epitopes and recurrent features of antibodies

Neutralizing antibody responses to coronaviruses focus on the trimeric spike, with most against the receptor-binding domain (RBD). Here we characterized polyclonal IgGs and Fabs from COVID-19 convalescent individuals for recognition of coronavirus spikes. Plasma IgGs differed in their degree of focus on RBD epitopes, recognition of SARS-CoV, MERS-CoV, and mild coronaviruses, and how avidity effects contributed to increased binding/neutralization of IgGs over Fabs. Electron microscopy reconstructions of polyclonal plasma Fab-spike complexes showed recognition of both S1A and RBD epitopes. A 3.4[A] cryo-EM structure of a neutralizing monoclonal Fab-S complex revealed an epitope that blocks ACE2 receptor-binding on "up" RBDs. Modeling suggested that IgGs targeting these sites have different potentials for inter-spike crosslinking on viruses and would not be greatly affected by identified SARS-CoV-2 spike mutations. These studies structurally define a recurrent anti-SARS-CoV-2 antibody class derived from VH3-53/VH3-66 and similarity to a SARS-CoV VH3-30 antibody, providing criteria for evaluating vaccine-elicited antibodies.

immunology↗

bioRxiv2020

Trimeric SARS-CoV-2 Spike interacts with dimeric ACE2 with limited intra-Spike avidity

A serious public health crisis is currently unfolding due to the SARS-CoV-2 pandemic. SARS-CoV-2 viral entry depends on an interaction between the receptor binding domain of the trimeric viral Spike protein (Spike-RBD) and the dimeric human angiotensin converting enzyme 2 (ACE2) receptor. While it is clear that strategies to block the Spike/ACE2 interaction are promising as anti-SARS-CoV-2 therapeutics, our current understanding is insufficient for the rational design of maximally effective therapeutic molecules. Here, we investigated the mechanism of Spike/ACE2 interaction by characterizing the binding affinity and kinetics of different multimeric forms of recombinant ACE2 and Spike-RBD domain. We also engineered ACE2 into a split Nanoluciferase-based reporter system to probe the conformational landscape of Spike-RBDs in the context of the Spike trimer. Interestingly, a dimeric form of ACE2, but not monomeric ACE2, binds with high affinity to Spike and blocks viral entry in pseudotyped virus and live SARS-CoV-2 virus neutralization assays. We show that dimeric ACE2 interacts with an RBD on Spike with limited intra-Spike avidity, which nonetheless contributes to the affinity of this interaction. Additionally, we demonstrate that a proportion of Spike can simultaneously interact with multiple ACE2 dimers, indicating that more than one RBD domain in a Spike trimer can adopt an ACE2-accessible "up" conformation. Our findings have significant implications on the design strategies of therapeutic molecules that block the Spike/ACE2 interaction. The constructs we describe are freely available to the research community as molecular tools to further our understanding of SARS-CoV-2 biology.

biochemistry↗

bioRxiv2020

Convergent Antibody Responses to SARS-CoV-2 Infection in Convalescent Individuals

During the COVID-19 pandemic, SARS-CoV-2 infected millions of people and claimed hundreds of thousands of lives. Virus entry into cells depends on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (S). Although there is no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-21-5. Here we report on 149 COVID-19 convalescent individuals. Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal neutralizing titers ranging from undetectable in 33% to below 1:1000 in 79%, while only 1% showed titers >1:5000. Antibody cloning revealed expanded clones of RBD-specific memory B cells expressing closely related antibodies in different individuals. Despite low plasma titers, antibodies to three distinct epitopes on RBD neutralized at half-maximal inhibitory concentrations (IC50s) as low as single digit ng/mL. Thus, most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.

immunology↗