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Staphylococcus aureus Alpha-Toxin Is Conserved among Diverse Hospital Respiratory Isolates Collected from a Global Surveillance Study and Is Neutralized by Monoclonal Antibody MEDI4893

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ABSTRACT

Staphylococcus aureus infections lead to an array of illnesses ranging from mild skin infections to serious diseases, such endocarditis, osteomyelitis, and pneumonia. Alpha-toxin (Hla) is a pore-forming toxin, encoded by the hla gene, that is thought to play a key role in S. aureus pathogenesis. A monoclonal antibody targeting Hla, MEDI4893, is in clinical development for the prevention of S. aureus ventilator-associated pneumonia (VAP). The presence of the hla gene and Hla protein in 994 respiratory isolates collected from patients in 34 countries in Asia, Europe, the United States, Latin America, the Middle East, Africa, and Australia was determined. Hla levels were correlated with the geographic location, age of the subject, and length of stay in the hospital. hla gene sequence analysis was performed, and mutations were mapped to the Hla crystal structure. S. aureus supernatants containing Hla variants were tested for susceptibility or resistance to MEDI4893. The hla gene was present and Hla was expressed in 99.0% and 83.2% of the isolates, respectively, regardless of geographic region, hospital locale, or age of the subject. More methicillin-susceptible than methicillin-resistant isolates expressed Hla (86.9% versus 78.8%; P = 0.0007), and S. aureus isolates from pediatric patients expressed the largest amounts of Hla. Fifty-seven different Hla subtypes were identified, and 91% of the isolates encoded an Hla subtype that was neutralized by MED4893. This study demonstrates that Hla is conserved in diverse S. aureus isolates from around the world and is an attractive target for prophylactic monoclonal antibody (MAb) or vaccine development.

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Related in: MedlinePlus

Alpha-toxin monomer and heptamer structures. (A) Hla heptamer, top view. (B) Hla heptamer, bottom view. (C) Hla monomer, 0°. (D) Hla monomer, 135°. (E) Hla monomer, 270°. The frequencies of amino acid substitutions in relation to the USA300 reference strain are shown using a color scale. The MEDI4893 binding region is shown in white.
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Figure 6: Alpha-toxin monomer and heptamer structures. (A) Hla heptamer, top view. (B) Hla heptamer, bottom view. (C) Hla monomer, 0°. (D) Hla monomer, 135°. (E) Hla monomer, 270°. The frequencies of amino acid substitutions in relation to the USA300 reference strain are shown using a color scale. The MEDI4893 binding region is shown in white.

Mentions: The structures of the Hla monomer (35), the Hla heptamer (36), and the MEDI4893 binding region (35) have been previously described. The MEDI4893 binding region encompasses amino acid residues 203 to 226 and 287 to 297 (35) and neutralizes Hla by preventing Hla binding to cells (35). The 82 amino acid substitutions were color coded based on frequency and mapped to both the monomer and the heptamer structures (Fig. 6A to E) in relation to the MEDI4893 epitope (shown in white). This analysis showed that 6 out of the 82 amino acid mutations identified were within the MEDI4893 binding region, representing 19 different isolates. However, four out of these six amino acids do not directly participate in the interaction with the antibody (amino acids [aa] 203, 218, 223, and 295, representing 4 different isolates), and these mutations are not expected to be of consequence. The other two amino acid mutations either make very little contribution to the interaction or the amino acid substitution is conservative. The change of an N to a T at position 214 results in the loss of a weak hydrogen bond and represents 1 isolate. The V-to-I change at position 216, representing 14 isolates, is conservative and is also unlikely to affect MEDI4893 binding to Hla. In summary, the MEDI4893 binding region is highly conserved.


Staphylococcus aureus Alpha-Toxin Is Conserved among Diverse Hospital Respiratory Isolates Collected from a Global Surveillance Study and Is Neutralized by Monoclonal Antibody MEDI4893
Alpha-toxin monomer and heptamer structures. (A) Hla heptamer, top view. (B) Hla heptamer, bottom view. (C) Hla monomer, 0°. (D) Hla monomer, 135°. (E) Hla monomer, 270°. The frequencies of amino acid substitutions in relation to the USA300 reference strain are shown using a color scale. The MEDI4893 binding region is shown in white.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4997823&req=5

Figure 6: Alpha-toxin monomer and heptamer structures. (A) Hla heptamer, top view. (B) Hla heptamer, bottom view. (C) Hla monomer, 0°. (D) Hla monomer, 135°. (E) Hla monomer, 270°. The frequencies of amino acid substitutions in relation to the USA300 reference strain are shown using a color scale. The MEDI4893 binding region is shown in white.
Mentions: The structures of the Hla monomer (35), the Hla heptamer (36), and the MEDI4893 binding region (35) have been previously described. The MEDI4893 binding region encompasses amino acid residues 203 to 226 and 287 to 297 (35) and neutralizes Hla by preventing Hla binding to cells (35). The 82 amino acid substitutions were color coded based on frequency and mapped to both the monomer and the heptamer structures (Fig. 6A to E) in relation to the MEDI4893 epitope (shown in white). This analysis showed that 6 out of the 82 amino acid mutations identified were within the MEDI4893 binding region, representing 19 different isolates. However, four out of these six amino acids do not directly participate in the interaction with the antibody (amino acids [aa] 203, 218, 223, and 295, representing 4 different isolates), and these mutations are not expected to be of consequence. The other two amino acid mutations either make very little contribution to the interaction or the amino acid substitution is conservative. The change of an N to a T at position 214 results in the loss of a weak hydrogen bond and represents 1 isolate. The V-to-I change at position 216, representing 14 isolates, is conservative and is also unlikely to affect MEDI4893 binding to Hla. In summary, the MEDI4893 binding region is highly conserved.

View Article: PubMed Central - PubMed

ABSTRACT

Staphylococcus aureus infections lead to an array of illnesses ranging from mild skin infections to serious diseases, such endocarditis, osteomyelitis, and pneumonia. Alpha-toxin (Hla) is a pore-forming toxin, encoded by the hla gene, that is thought to play a key role in S. aureus pathogenesis. A monoclonal antibody targeting Hla, MEDI4893, is in clinical development for the prevention of S. aureus ventilator-associated pneumonia (VAP). The presence of the hla gene and Hla protein in 994 respiratory isolates collected from patients in 34 countries in Asia, Europe, the United States, Latin America, the Middle East, Africa, and Australia was determined. Hla levels were correlated with the geographic location, age of the subject, and length of stay in the hospital. hla gene sequence analysis was performed, and mutations were mapped to the Hla crystal structure. S. aureus supernatants containing Hla variants were tested for susceptibility or resistance to MEDI4893. The hla gene was present and Hla was expressed in 99.0% and 83.2% of the isolates, respectively, regardless of geographic region, hospital locale, or age of the subject. More methicillin-susceptible than methicillin-resistant isolates expressed Hla (86.9% versus 78.8%; P = 0.0007), and S. aureus isolates from pediatric patients expressed the largest amounts of Hla. Fifty-seven different Hla subtypes were identified, and 91% of the isolates encoded an Hla subtype that was neutralized by MED4893. This study demonstrates that Hla is conserved in diverse S. aureus isolates from around the world and is an attractive target for prophylactic monoclonal antibody (MAb) or vaccine development.

No MeSH data available.


Related in: MedlinePlus