Identification of a staphylococcal complement inhibitor with broad host specificity in equid Staphylococcus aureus strains.
Abstract: Staphylococcus aureus is a versatile pathogen capable of causing a broad range of diseases in many different hosts. S. aureus can adapt to its host through modification of its genome (e.g. by acquisition and exchange of mobile genetic elements that encode host-specific virulence factors). Recently, the prophage φSaeq1 was discovered in S. aureus strains from six different clonal lineages almost exclusively isolated from equids. Within this phage, we discovered a novel variant of staphylococcal complement inhibitor (SCIN), a secreted protein that interferes with activation of the human complement system, an important line of host defense. We here show that this equine variant of SCIN, eqSCIN, is a potent blocker of equine complement system activation and subsequent phagocytosis of bacteria by phagocytes. Mechanistic studies indicate that eqSCIN blocks equine complement activation by specific inhibition of the C3 convertase enzyme (C3bBb). Whereas SCIN-A from human S. aureus isolates exclusively inhibits human complement, eqSCIN represents the first animal-adapted SCIN variant that functions in a broader range of hosts (horses, humans, and pigs). Binding analyses suggest that the human-specific activity of SCIN-A is related to amino acid differences on both sides of the SCIN-C3b interface. These data suggest that modification of this phage-encoded complement inhibitor plays a role in the host adaptation of S. aureus and are important to understand how this pathogen transfers between different hosts.
© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.
Publication Date: 2018-02-05 PubMed ID: 29414776PubMed Central: PMC5868266DOI: 10.1074/jbc.RA117.000599Google Scholar: Lookup
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- Journal Article
- Research Support
- N.I.H.
- Extramural
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- Non-U.S. Gov't
Summary
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This research identifies a variant of the staphylococcal complement inhibitor (SCIN) in equid Staphylococcus aureus strains, a bacterium often found in horses. This variant, known as eqSCIN, disrupts the equine immune system and aids the bacteria’s survival, with the potential to function in a variety of hosts including horses, humans, and pigs.
Overview of Staphylococcus aureus and eqSCIN
- This study centers on Staphylococcus aureus (S. aureus), a bacterium capable of causing a wide array of diseases in numerous hosts.
- S. aureus is known to be adaptable, modifying its genome to thrive in different hosts by acquiring and exchanging genetic elements that result in host-specific disease-causing factors.
- This research focuses on the discovery of an equine variant of the staphylococcal complement inhibitor (eqSCIN) found in the prophage φSaeq1, which has been discovered in S. aureus strains isolated from horses.
eqSCIN’s Role in Immune System Disruption
- SCIN is a protein that interferes with the activation of the human complement system, a critical element of the body’s defense against infections.
- The study found that eqSCIN is effective in inhibiting the activation of the equine (horse) complement system.
- By disrupting equine immune responses, eqSCIN promotes bacterial survival through the blocking of phagocytosis – the process through which pathogens are engulfed and destroyed by immune cells.
Specificity and Broad Host Potential
- SCIN-A, another variant of SCIN found in human S. aureus isolates, specifically inhibits only the human complement system.
- Potentially marking a distinction, eqSCIN has been found to function in a broader range of hosts, including horses, humans, and pigs.
- Binding analyses suggested that the human-specific activity of SCIN-A is due to certain amino acid differences. In particular, it was noted that these differences occur on both sides of the interface between SCIN and the human complement component, C3b.
Implication of Findings
- The study’s findings suggest that the modification of this phage-encoded complement inhibitor plays a significant role in how S. aureus adapts to different hosts.
- This understanding about eqSCIN’s functioning across multiple hosts is important for comprehending how S. aureus transitions and survives across different species
Cite This Article
APA
de Jong NWM, Vrieling M, Garcia BL, Koop G, Brettmann M, Aerts PC, Ruyken M, van Strijp JAG, Holmes M, Harrison EM, Geisbrecht BV, Rooijakkers SHM.
(2018).
Identification of a staphylococcal complement inhibitor with broad host specificity in equid Staphylococcus aureus strains.
J Biol Chem, 293(12), 4468-4477.
https://doi.org/10.1074/jbc.RA117.000599 Publication
Researcher Affiliations
- From the Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands.
- From the Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands.
- the Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian EH25 9RG, United Kingdom.
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506.
- the Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands.
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506.
- From the Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands.
- From the Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands.
- From the Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands.
- the Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, United Kingdom, and.
- the Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506.
- From the Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands, s.h.m.rooijakkers@umcutrecht.nl.
MeSH Terms
- Animals
- Complement C3-C5 Convertases / metabolism
- Complement C3b / antagonists & inhibitors
- Complement C3b / metabolism
- Complement Inactivator Proteins / chemistry
- Complement Inactivator Proteins / metabolism
- Hemolysis
- Horses
- Host Specificity
- Humans
- Phagocytosis
- Protein Binding
- Staphylococcal Infections / metabolism
- Staphylococcal Infections / microbiology
- Staphylococcus aureus / isolation & purification
- Staphylococcus aureus / metabolism
- Swine
- Virulence Factors / chemistry
- Virulence Factors / metabolism
Grant Funding
- G1001787 / Medical Research Council
- WT098600 / Wellcome Trust
- R01 GM121511 / NIGMS NIH HHS
- 639209 / European Research Council
- R21 AI113552 / NIAID NIH HHS
- Wellcome Trust
- MR/P007201/1 / Medical Research Council
Conflict of Interest Statement
The authors declare that they have no conflicts of interest with the contents of this article
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