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


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 introduced into an S. aureus clinical isolate, the mutant-expressing strains exhibited less severe disease in mouse models and were effectively neutralized by MEDI4893. These results indicate the MEDI4893 epitope is highly conserved due in part to its role in AT pore formation and bacterial fitness, thereby decreasing the likelihood for the emergence of MAb-resistant variants.

Submission Details

ID: mdncvu3V

Submitter: Shu-Ching Ou

Submission Date: March 12, 2019, 1:21 p.m.

Version: 1

Publication Details
Tkaczyk C;Semenova E;Shi YY;Rosenthal K;Oganesyan V;Warrener P;Stover CK;Sellman BR,Antimicrob Agents Chemother (2018) Alanine Scanning Mutagenesis of the MEDI4893 (Suvratoxumab) Epitope Reduces Alpha Toxin Lytic Activity In Vitro and Staphylococcus aureus Fitness in Infection Models. PMID:30150481
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
200.0 A,B Alpha-hemolysin Q2G1X0 HLA_STAA8
199.4 A,B Alpha-hemolysin P09616 HLA_STAAU
198.0 H,K Alpha-hemolysin P01857 IGHG1_HUMAN
191.8 H,K Alpha-hemolysin P01766 HV313_HUMAN
190.2 H,K Alpha-hemolysin P01860 IGHG3_HUMAN
184.2 H,K Alpha-hemolysin P01861 IGHG4_HUMAN
188.8 L,M Alpha-hemolysin P0DOX7 IGK_HUMAN
200.0 L,M Alpha-hemolysin P01834 IGKC_HUMAN
193.6 L,M Alpha-hemolysin P01602 KV105_HUMAN
182.2 L,M Alpha-hemolysin A0A0C4DH73 KV112_HUMAN
182.2 L,M Alpha-hemolysin P01611 KVD12_HUMAN
182.2 L,M Alpha-hemolysin P01597 KV139_HUMAN
182.2 L,M Alpha-hemolysin P04432 KVD39_HUMAN