Identification of Anti-Alpha Toxin Monoclonal Antibodies That Reduce the Severity of Staphylococcus aureus Dermonecrosis and Exhibit a Correlation between Affinity and Potency

Tkaczyk, Christine; Liu, Hua; Varkey, Reena; Shi, Yueyue; Dettinger, L.; Woods, R. Claude; Barnes, Arnita; MacGill, Randall S.; Wilson, Susan; Chowdhury, Partha S.; Stover, C. Kendall; Sellman, Bret R.

doi:10.1128/cvi.05589-11

Cited by 112 publications

(145 citation statements)

References 37 publications

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“…To gain a better understanding about strain coverage of the anti-AT MAb clinical candidate MEDI4893 (29,34), its neutralization capacity was assessed against all of the isolates producing functional alpha-toxin. MEDI4893 effectively neutralized each of the different toxin variants.…”

Section: Resultsmentioning

confidence: 99%

“…In murine S. aureus skin and soft tissue infection models, both active immunization with a nontoxigenic alpha-toxin mutant and passive immunization with alpha-toxinspecific antiserum or IgG significantly improved survival and reduced disease severity (27,(32)(33)(34). Antibodies against alpha-toxin were both necessary and sufficient for protection against soft tissue infection and were inversely associated with bacterial counts (32) and had a protective role in keratitis (35).…”

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confidence: 99%

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Characterization of Alpha-Toxin hla Gene Variants, Alpha-Toxin Expression Levels, and Levels of Antibody to Alpha-Toxin in Hemodialysis and Postsurgical Patients with Staphylococcus aureus Bacteremia

Sharma-Kuinkel

Wu²,

Tabor³

et al. 2015

J Clin Microbiol

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c Alpha-toxin is a major Staphylococcus aureus virulence factor. This study evaluated potential relationships between in vitro alpha-toxin expression of S. aureus bloodstream isolates, anti-alpha-toxin antibody in serum of patients with S. aureus bacteremia (SAB), and clinical outcomes in 100 hemodialysis and 100 postsurgical SAB patients. Isolates underwent spa typing and hla sequencing. Serum anti-alpha-toxin IgG and neutralizing antibody levels were measured by using an enzyme-linked immunosorbent assay and a red blood cell (RBC)-based hemolysis neutralization assay. Neutralization of alpha-toxin by an anti-alpha-toxin monoclonal antibody (MAb MEDI4893) was tested in an RBC-based lysis assay. Most isolates encoded hla (197/200; 98.5%) and expressed alpha-toxin (173/200; 86.5%). In vitro alpha-toxin levels were inversely associated with survival (cure, 2.19 g/ml, versus failure, 1.09 g/ml; P < 0.01). Both neutralizing (hemodialysis, 1.26 IU/ml, versus postsurgical, 0.95; P < 0.05) and IgG (hemodialysis, 1.94 IU/ml, versus postsurgical, 1.27; P < 0.05) antibody levels were higher in the hemodialysis population. Antibody levels were also significantly higher in patients infected with alpha-toxin-expressing S. aureus isolates (P < 0.05). Levels of both neutralizing antibodies and IgG were similar among patients who were cured and those not cured (failures). Sequence analysis of hla revealed 12 distinct hla genotypes, and all genotypic variants were susceptible to a neutralizing monoclonal antibody in clinical development (MEDI4893). These data demonstrate that alpha-toxin is highly conserved in clinical S. aureus isolates. Higher in vitro alpha-toxin levels were associated with a positive clinical outcome. Although patients infected with alpha-toxin-producing S. aureus exhibited higher anti-alpha-toxin antibody levels, these levels were not associated with a better clinical outcome in this study. Staphylococcus aureus is a leading cause of bacterial infections (1-4), including skin and soft tissue infections (5), pneumonia (6), bacteremia (7), endocarditis (8-10), and bone and joint infections (11). The risk of invasive S. aureus infections is significantly higher among certain subgroups, including hemodialysisdependent patients and postoperative patients (12-14).These high-risk subpopulations are potential candidates for novel forms of prevention or treatment against invasive S. aureus infections.Alpha-toxin, a ␤-barrel pore-forming exotoxin encoded by hla (15, 16), is a key virulence factor produced by most S. aureus isolates (17, 18). It binds to ADAM10 (the A disintegrin and metalloproteinase domain-containing protein 10) on target cell membranes and then heptamerizes to generate a transmembrane pore, resulting in cell lysis (19). Hyperproduction of alpha-toxin is associated with enhanced virulence in strains of both epidemic (USA300 and USA500) and endemic (ST93) community-associated methicillin-resistant S. aureus (CA-MRSA) isolates (20,21). Studies with a number of animal models have also suggested that al...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Characterization of Alpha-Toxin hla Gene Variants, Alpha-Toxin Expression Levels, and Levels of Antibody to Alpha-Toxin in Hemodialysis and Postsurgical Patients with Staphylococcus aureus Bacteremia

Sharma-Kuinkel

Wu²,

Tabor³

et al. 2015

J Clin Microbiol

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“…The use of animal serum containing antibodies that target bacterial antigens was a common therapeutic approach pre-dating the development of small molecule antibiotics, 7 but technological advances in antibody discovery, including B-cell cloning from human patients, 8 has invigorated research into monoclonal antibody (mAb)-based antibiotics. Anti-infective biologics with novel mechanisms of action targeting S. aureus alpha toxin, 9,10 protective antigen of Bacillus anthracis , 11 toxins A and B from Clostridium difficile , 12 and Pseudomonas aeruginosa cell wall components 13,14 are currently approved or in clinical development. The presence of cell wall glycopolymers, particularly in Gram-positive bacteria, shields many epitopes that might confer bactericidal activity from antibodies and other host-defense molecules, 15 but these cell wall polysaccharides also represent a potential target for mAb therapeutics.…”

Section: Introductionmentioning

confidence: 99%

Structural investigation of humanS. aureus-targeting antibodies that bind wall teichoic acid

Fong¹,

Kajihara²,

Chen³

et al. 2018

mAbs

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Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a growing health threat worldwide. Efforts to identify novel antibodies that target S. aureus cell surface antigens are a promising direction in the development of antibiotics that can halt MRSA infection. We biochemically and structurally characterized three patient-derived MRSA-targeting antibodies that bind to wall teichoic acid (WTA), which is a polyanionic surface glycopolymer. In S. aureus, WTA exists in both α- and β-forms, based on the stereochemistry of attachment of a N-acetylglucosamine residue to the repeating phosphoribitol sugar unit. We identified a panel of antibodies cloned from human patients that specifically recognize the α or β form of WTA, and can bind with high affinity to pathogenic wild-type strains of S. aureus bacteria. To investigate how the β-WTA specific antibodies interact with their target epitope, we determined the X-ray crystal structures of the three β-WTA specific antibodies, 4462, 4497, and 6078 (Protein Data Bank IDs 6DWI, 6DWA, and 6DW2, respectively), bound to a synthetic WTA epitope. These structures reveal that all three of these antibodies, while utilizing distinct antibody complementarity-determining region sequences and conformations to interact with β-WTA, fulfill two recognition principles: binding to the β-GlcNAc pyranose core and triangulation of WTA phosphate residues with polar contacts. These studies reveal the molecular basis for targeting a unique S. aureus cell surface epitope and highlight the power of human patient-based antibody discovery techniques for finding novel pathogen-targeting therapeutics.

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“…17,24 Polyclonal antibodies to the staphylococcal CPs protect mice against bacteremia but not lethal pneumonia, 25 whereas antibodies to S. aureus Hla protect mice against lethal pneumonia but not bacteremia. 21,22,25 We showed previously that polyclonal CP5-specific antibodies protected against experimental bacteremia induced by four different serotype 5 isolates. 25 In this study, the CP5 backbone-specific 4C2 mAb protected mice against experimental Reynolds (CP5) bacteremia.…”

Section: Discussionmentioning

confidence: 99%

“…Hla mAbs reduced the severity and tissue damage associated with staphylococcal skin infections and necrotizing pneumonia in preclinical studies. [20][21][22] A human mAb that neutralizes both Hla and four staphylococcal leukocidins 23 is beginning a phase 2 clinical trial for the prevention of S. aureus pneumonia in mechanically ventilated subjects. Because of the complexity of S. aureus pathogenesis and the diversity of staphylococcal infections, it is likely that immunoprophylaxis with mAbs will need to target multiple staphylococcal antigens.…”

Section: Introductionmentioning

confidence: 99%

Antibodies toStaphylococcus aureuscapsular polysaccharides 5 and 8 perform similarlyin vitrobut are functionally distinctin vivo

et al. 2016

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The capsular polysaccharide (CP) produced by Staphylococcus aureus is a virulence factor that allows the organism to evade uptake and killing by host neutrophils. Polyclonal antibodies to the serotype 5 (CP5) and type 8 (CP8) capsular polysaccharides are opsonic and protect mice against experimental bacteremia provoked by encapsulated staphylococci. Thus, passive immunotherapy using CP antibodies has been considered for the prevention or treatment of invasive antibioticresistant S. aureus infections. In this report, we generated monoclonal antibodies (mAbs) against S. aureus CP5 or CP8. Backbone specific mAbs reacted with native and O-deacetylated CPs, whereas Oacetyl specific mAbs reacted only with native CPs. Reference strains of S. aureus and a selection of clinical isolates reacted by colony immunoblot with the CP5 and CP8 mAbs in a serotype-specific manner. The mAbs mediated in vitro CP type-specific opsonophagocytic killing of S. aureus strains, and mice passively immunized with CP5 mAbs were protected against S. aureus bacteremia. Neither CP8-specific mAbs or polyclonal antibodies protected mice against bacteremia provoked by serotype 8 S. aureus clinical isolates, although these same antibodies did protect against a serotype 5 S. aureus strain genetically engineered to produce CP8. We detected soluble CP8 in culture supernatants of serotype 8 clinical isolates and in the plasma of infected animals. Serotype 5 S. aureus released significantly less soluble CP5 in vitro and in vivo. The release of soluble CP8 by S. aureus may contribute to the inability of CP8 vaccines or antibodies to protect against serotype 8 staphylococcal infections.

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Identification of Anti-Alpha Toxin Monoclonal Antibodies That Reduce the Severity of Staphylococcus aureus Dermonecrosis and Exhibit a Correlation between Affinity and Potency

Abstract: Staphylococcus aureus alpha toxin (AT) is an important virulence determinant and may be a valid target for immunoprophylaxis

Cited by 112 publications

References 37 publications

Characterization of Alpha-Toxin hla Gene Variants, Alpha-Toxin Expression Levels, and Levels of Antibody to Alpha-Toxin in Hemodialysis and Postsurgical Patients with Staphylococcus aureus Bacteremia

Characterization of Alpha-Toxin hla Gene Variants, Alpha-Toxin Expression Levels, and Levels of Antibody to Alpha-Toxin in Hemodialysis and Postsurgical Patients with Staphylococcus aureus Bacteremia

Structural investigation of humanS. aureus-targeting antibodies that bind wall teichoic acid

Antibodies toStaphylococcus aureuscapsular polysaccharides 5 and 8 perform similarlyin vitrobut are functionally distinctin vivo

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