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Title: Identification, cloning and characterization of SpEX exotoxin produced by Staphylococcus pseudintermedius

Abstract

Staphylococci have evolved numerous strategies to evade their hosts’ immune systems. Some staphylococcal toxins target essential components of host innate immunity, one of the two main branches of the immune system. Analysis of the Staphylococcus pseudintermedius secretome using liquid chromatography mass spectrometry guided by genomic data, was used to identify an S. pseudintermedius exotoxin provisionally named SpEX. This exoprotein has low overall amino acid identity with the Staphylococcus aureus group of proteins named staphylococcal superantigen like proteins (SSLs) and staphylococcal enterotoxin- like toxin X (SEIX), but predictive modeling showed that it shares similar folds and domain architecture to these important virulence factors. In this study, we found SpEX binds to complement component C5, prevents complement mediated lysis of sensitized bovine red blood cells, kills polymorphonuclear leukocytes and monocytes and inhibits neutrophil migration at sub-lethal concentrations. A mutant version of SpEX, produced through amino acid substitution at selected positions, had diminished cytotoxicity. Anti-SpEX produced in dogs reduced the inhibitory effect of native SpEX on canine neutrophil migration and protected immune cells from the toxic effects of the native recombinant protein. These results suggest that SpEX likely plays an important role in S. pseudintermedius virulence and that attenuated SpEX may be anmore » important candidate for inclusion in a vaccine against S. pseudintermedius infections.« less

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3];  [2]; ORCiD logo [2];  [4]
  1. Univ. of Tennessee, Knoxville, TN (United States); Univ. of Sadat City, Menoufia (Egypt)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Indiana Univ., Bloomington, IN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1561612
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
PLoS ONE
Additional Journal Information:
Journal Volume: 14; Journal Issue: 7; Journal ID: ISSN 1932-6203
Publisher:
Public Library of Science
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Abouelkhair, Mohamed A., Bemis, David A., Giannone, Richard J., Frank, Linda A., Kania, Stephen A., and Bae, Taeok. Identification, cloning and characterization of SpEX exotoxin produced by Staphylococcus pseudintermedius. United States: N. p., 2019. Web. doi:10.1371/journal.pone.0220301.
Abouelkhair, Mohamed A., Bemis, David A., Giannone, Richard J., Frank, Linda A., Kania, Stephen A., & Bae, Taeok. Identification, cloning and characterization of SpEX exotoxin produced by Staphylococcus pseudintermedius. United States. doi:10.1371/journal.pone.0220301.
Abouelkhair, Mohamed A., Bemis, David A., Giannone, Richard J., Frank, Linda A., Kania, Stephen A., and Bae, Taeok. Mon . "Identification, cloning and characterization of SpEX exotoxin produced by Staphylococcus pseudintermedius". United States. doi:10.1371/journal.pone.0220301. https://www.osti.gov/servlets/purl/1561612.
@article{osti_1561612,
title = {Identification, cloning and characterization of SpEX exotoxin produced by Staphylococcus pseudintermedius},
author = {Abouelkhair, Mohamed A. and Bemis, David A. and Giannone, Richard J. and Frank, Linda A. and Kania, Stephen A. and Bae, Taeok},
abstractNote = {Staphylococci have evolved numerous strategies to evade their hosts’ immune systems. Some staphylococcal toxins target essential components of host innate immunity, one of the two main branches of the immune system. Analysis of the Staphylococcus pseudintermedius secretome using liquid chromatography mass spectrometry guided by genomic data, was used to identify an S. pseudintermedius exotoxin provisionally named SpEX. This exoprotein has low overall amino acid identity with the Staphylococcus aureus group of proteins named staphylococcal superantigen like proteins (SSLs) and staphylococcal enterotoxin- like toxin X (SEIX), but predictive modeling showed that it shares similar folds and domain architecture to these important virulence factors. In this study, we found SpEX binds to complement component C5, prevents complement mediated lysis of sensitized bovine red blood cells, kills polymorphonuclear leukocytes and monocytes and inhibits neutrophil migration at sub-lethal concentrations. A mutant version of SpEX, produced through amino acid substitution at selected positions, had diminished cytotoxicity. Anti-SpEX produced in dogs reduced the inhibitory effect of native SpEX on canine neutrophil migration and protected immune cells from the toxic effects of the native recombinant protein. These results suggest that SpEX likely plays an important role in S. pseudintermedius virulence and that attenuated SpEX may be an important candidate for inclusion in a vaccine against S. pseudintermedius infections.},
doi = {10.1371/journal.pone.0220301},
journal = {PLoS ONE},
issn = {1932-6203},
number = 7,
volume = 14,
place = {United States},
year = {2019},
month = {7}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

Fig 1 Fig 1: S. pseudintermedius SpEX structural characteristics. a. SpEX of S. pseudintermedius harbors an N-terminal signal peptide (green arrow) from position 1–35, OB domain (orange arrow) in residues 43–126 and C-terminal β grasp domain in residues 150–234 (orange arrow). b. The 3D model of S. pseudintermedius SpEX and S. aureusmore » SSL11 shows the N and C terminal domains fold into a five-stranded beta-barrel structure consisting of β1- β5 and β7, β6, β12, β9 and β10. A central helix is orientated diagonally in the center of the field from the top left to the bottom right leaving the N-terminal domain on the left and C-terminal domain on the right. A conserved sialated glycan binding domain forming V-shape depression is highlighted in purple in SpEX and SSL11 3D models.« less

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