Alanine Scanning Mutagenesis of the MEDI4893 (Suvratoxumab) Epitope Reduces Alpha Toxin Lytic Activity In Vitro and Staphylococcus aureus Fitness in Infection Models

Antimicrobial Agents and Chemotherapy
Christine TkaczykBret R Sellman

Abstract

Alpha toxin (AT) is a cytolytic pore-forming toxin that plays a key role in Staphylococcus aureus pathogenesis; consequently, extensive research was undertaken to understand the AT mechanism of action and its utility as a target for novel prophylaxis and treatment strategies against S. aureus infections. MEDI4893 (suvratoxumab) is a human anti-AT IgG1 monoclonal antibody (MAb) that targets AT and is currently in phase 2 clinical development. As shown previously, the MEDI4893-binding epitope on AT is comprised of the highly conserved amino acid regions 177 to 200 and 261 to 271, suggesting these amino acids are important for AT function. To test this hypothesis and gain insight into the effect of mutations in the epitope on AT neutralization by MEDI4893, nine MEDI4893 contact residues in AT were individually mutated to alanine. Consistent with our hypothesis, 8 out of 9 mutants exhibited >2-fold loss in lytic activity resulting from a defect in cell binding and pore formation. MEDI4893 binding affinity was reduced >2-fold (2- to 27-fold) for 7 out of 9 mutants, and no binding was detected for the W187A mutant. MEDI4893 effectively neutralized all of the lytic mutants in vitro and in vivo When the defective mutants were introduce...Continue Reading

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Citations

Apr 6, 2019·Current Opinion in Infectious Diseases·Michael P MotleyBettina C Fries
Nov 30, 2018·Medical Microbiology and Immunology·Vigyasa Singh, Ujjal Jyoti Phukan
Feb 2, 2021·Frontiers in Microbiology·Caleb A FordJames E Cassat
Mar 14, 2020·Infectious Disorders Drug Targets·Gerard M RajMangaiarkkarasi Adhimoolam

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Methods Mentioned

BETA
ion-exchange chromatography
flow cytometry
PCR
chip
fluorescence-activated cell sorting

Software Mentioned

Odyssey Image Studio Lite
FlowJo
BIAevaluation

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