Biology subjects

Casner, R. G.

Publications and source records attributed to Casner, R. G..

4 recordsLinked to original sources

bioRxiv2024

Optimizing a Human Monoclonal Antibody for Better Neutralization of SARS-CoV-2

SARS-CoV-2 has largely evolved to resist antibody pressure, with each successive viral variant becoming more and more resistant to serum antibodies in the population. This evolution renders all previously authorized anti-spike therapeutic monoclonal antibodies inactive, and it threatens the remaining pipelines against COVID-19. We report herein the isolation of a human monoclonal antibody with a broad but incomplete SARS-CoV-2 neutralization profile, but structural analyses and mutational scanning lead to the engineering of variants that result in greater antibody flexibility while binding to the viral spike. Three such optimized monoclonal antibodies neutralize all SARS-CoV-2 strains tested with much improved potency and breadth, including against subvariants XEC and LP.8.1. The findings of this study not only present antibody candidates for clinical development against COVID-19, but also introduce a unique engineering approach to improve antibody activity via increasing conformational flexibility.

microbiology↗

bioRxiv2023

Antibodies that neutralize all current SARS-CoV-2 variants of concern by conformational locking

SARS-CoV-2 continues to evolve and evade most existing neutralizing antibodies, including all clinically authorized antibodies. We have isolated and characterized two human monoclonal antibodies, 12-16 and 12-19, which exhibited neutralizing activities against all SARS-CoV-2 variants tested, including BQ.1.1 and XBB.1.5. They also blocked infection in hamsters challenged with Omicron BA.1 intranasally. Structural analyses revealed both antibodies targeted a conserved quaternary epitope located at the interface between the N-terminal domain and subdomain 1, revealing a previously unrecognized site of vulnerability on SARS-CoV-2 spike. These antibodies prevent viral receptor engagement by locking the receptor-binding domain of spike in the down conformation, revealing a novel mechanism of virus neutralization for non-RBD antibodies. Deep mutational scanning showed that SARS-CoV-2 could mutate to escape 12-19, but the responsible mutations are rarely found in circulating viruses. Antibodies 12-16 and 12-19 hold promise as prophylactic agents for immunocompromised persons who do not respond robustly to COVID-19 vaccines.

microbiology↗

bioRxiv2022

Potent and pan-neutralization of SARS-CoV-2 variants of concern by DARPins

We report the engineering and selection of two synthetic proteins - FSR16m and FSR22 - for possible treatment of SARS-CoV-2 infection. FSR16m and FSR22 are trimeric proteins composed of DARPin SR16m or SR22 fused with a T4 foldon and exhibit broad spectrum neutralization of SARS-Cov-2 strains. The IC50 values of FSR16m against authentic B.1.351, B.1.617.2 and BA.1.1 variants are 3.4 ng/mL, 2.2 ng/mL and 7.4 ng/mL, respectively, comparable to currently used therapeutic antibodies. Despite the use of the spike protein from a now historical wild-type virus for design, FSR16m and FSR22 both exhibit increased neutralization against newly-emerged variants of concern (39- to 296-fold) in pseudovirus assays. Cryo-EM structures revealed that these DARPins recognize a region of the receptor binding domain (RBD, residues 455-456, 486-489) overlapping a critical portion of the ACE2-binding surface. K18-hACE2 transgenic mice inoculated with a B.1.617.2 variant and receiving intranasally-administered FSR16m were protected as judged by less weight loss and 10-100-fold reductions in viral burden in the upper and lower respiratory tracts. The strong and broad neutralization potency make FSR16m and FSR22 promising candidates for prevention and treatment of infection by current and potential future strains of SARS-CoV-2.

bioengineering↗

bioRxiv2021

A monoclonal antibody that neutralizes SARS-CoV-2 variants, SARS-CoV, and other sarbecoviruses

The repeated emergence of highly pathogenic human coronaviruses as well as their evolving variants highlight the need to develop potent and broad-spectrum antiviral therapeutics and vaccines. By screening monoclonal antibodies (mAbs) isolated from COVID-19-convalescent patients, we found one mAb, 2-36, with cross-neutralizing activity against SARS-CoV. We solved the cryo-EM structure of 2-36 in complex with SARS-CoV-2 or SARS-CoV spike, revealing a highly conserved epitope in the receptor-binding domain (RBD). Antibody 2-36 neutralized not only all current circulating SARS-CoV-2 variants and SARS-COV, but also a panel of bat and pangolin sarbecoviruses that can use human angiotensin-converting enzyme 2 (ACE2) as a receptor. We selected 2-36-escape viruses in vitro and confirmed that K378T in SARS-CoV-2 RBD led to viral resistance. Taken together, 2-36 represents a strategic reserve drug candidate for the prevention and treatment of possible diseases caused by pre-emergent SARS-related coronaviruses. Its epitope defines a promising target for the development of a pan-sarbecovirus vaccine.

microbiology↗