Biology subjects

Stefan, M. A.

Publications and source records attributed to Stefan, M. A..

2 recordsLinked to original sources

bioRxiv2024

Combining computational modeling and experimental library screening to affinity-mature VEEV-neutralizing antibody F5

Engineered monoclonal antibodies (mAbs) have proven to be highly effective therapeutics in recent viral outbreaks due to their specificity and ability to provide immediate protection, regardless of immune status. However, despite technical advancements in the field, an ability to rapidly adapt or increase antibody affinity and by extension, therapeutic efficacy, has yet to be fully realized. We endeavored to stand-up such a pipeline using molecular modeling combined with experimental library screening to increase the affinity of a given antibody, F5, to recombinant E1E2 antigen from Venezuelan Equine Encephalitis Virus (VEEV) subtype IAB (TC-83). F5 is a monoclonal antibody with potent neutralizing activity against VEEV that was isolated from human bone marrow donors. F5 is known to bind to spikes on the surface of VEEV made up of a trimer of heterodimers of the glycoproteins E1 and E2. In this work we modeled the interaction of F5 with the E1E2 trimer of VEEV (TC-83) and generated predictions for mutations to improve binding using a Rosetta-based approach and dTERMen, an informatics approach. Modeling the structure of the complex was complicated by the fact that a high-resolution structure of F5 is not available and the H3 loop of F5 exceeds the length for which current modeling approaches can determine a unique structure. To overcome these challenges nine F5 structures with varying H3 loop conformations were generated using RosettaAntibody, PIGS (Prediction of ImmunoGlobulin Structure), and SWISS-Model and these base antibody structures were evaluated in docking trials to recombinant VEEV E1E2 based on relative binding affinity for several subtypes. The structure that gave the best agreement with the experimental trend in relative binding affinity was used for mutation analysis. A subset of the predicted mutations from both methods were incorporated into a phage display library of scFvs (single-chain variable fragments) and screened for binding affinity to the recombinant E1E2 antigen. Results from this screen were used to identify favorable mutations which were then incorporated into twelve human-IgG1 variants. All twelve variants showed increased binding relative to the parental F5 human-IgG1. The best case showed > 60x increased binding to recombinant E1E2 relative to the parental antibody, notably showing a drastic improvement of the Kd or "off rate" compared to the parental F5 IgG. These results demonstrate the ability of our methods to rapidly increase affinity and could be leveraged for increasing Ab binding breadth to additional viral variants.

microbiology↗

bioRxiv2021

Development of Potent and Effective Synthetic SARS-CoV-2 Neutralizing Nanobodies

The respiratory virus responsible for Coronavirus disease 2019 (COVID-19), Severe acute respiratory syndrome coronavirus 2 (SARS-2), has impacted nearly every aspect of life worldwide, claiming the lives of over 2.5 million people globally, at the time of this publication. Neutralizing nanobodies (VHH) represent a promising therapeutic intervention strategy to address the current SARS-2 pandemic and provide a powerful toolkit to address future virus outbreaks. Using a synthetic, high-diversity VHH bacteriophage library, several potent neutralizing VHH antibodies were identified and evaluated for their capacity to tightly bind to the SARS-2 receptor-binding domain (RBD), to prevent binding of SARS-2 spike (S) to the cellular receptor Angiotensin-converting enzyme 2 (ACE2), and to neutralize viral infection. Preliminary preclinical evaluation of multiple nanobody candidates demonstrate that they are prophylactically and therapeutically effective in vivo against wildtype SARS-2. The identified and characterized nanobodies described herein represent viable candidates for further preclinical evaluation and another tool to add to our therapeutic arsenal to address the COVID-19 pandemic. Author SummaryTo fully address the on-going pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-2), it will be important to have both vaccines and therapeutic strategies to prevent and mitigate the effects of SARS-2. In this study, we describe the identification and characterization of potently neutralizing humanized single domain heavy chain (VHH) antibodies that have binding affinity for both the original Wuhan strain and widely circulating B.1.1.7/UK strain. VHH antibodies have the same therapeutic potential as conventional antibodies in half the size and with greater stability and solubility. Using a synthetic humanized high-diversity VHH phage library we identified several candidates with strong affinity for the SARS-2 spike that block the interaction of SARS-2 spike with the cellular receptor ACE2, and effectively neutralize infection with SARS-2 in vitro. By sequencing viral escape mutants generated in the presence of each VHH we mapped the binding sites of the VHH antibodies and assessed their affinity against newly emerging SARS-2 variants. Finally, we demonstrate that two of these VHH antibodies show prophylactic and therapeutic efficacy in vivo against challenge with SARS-2. This study establishes that screening highly diverse VHH phage libraries against viral threats can yield highly effective therapeutic agents in real time.

immunology↗