Key Role of Staphylococcal Fibronectin-Binding Proteins During the Initial Stage of Staphylococcus aureus Keratitis in Humans

Abstract

ObjectivesStaphylococcus aureus is one of the main causes of bacterial keratitis in humans. This study was aimed at investigating the mechanisms of S. aureus adhesion to the human corneal epithelium involved during the initial stage of infectious keratitis.MethodsHuman corneas stored in a specific active storage machine that restores a normal pluristratified epithelium were used to assess S. aureus adhesion level to intact and injured tissues using immunostaining. S. aureus adhesion to immobilized fibronectin was measured in microtiter plate. Internalization of S. aureus clinical isolates recovered from keratitis was assessed on human corneal epithelial HCE-2 cells.ResultsSuperficial corneal injury unmasked fibronectin molecules expressed within the human corneal epithelium. S. aureus adhesion level was increased by 117-fold in the area of injured epithelium (p < 0.0001). The deletion of staphylococcal fnbA/B genes decreased by 71% the adhesion level to immobilized fibronectin (p < 0.001). The deletion of fnbA/B genes and the incubation of the corneas with anti-fibronectin blocking antibodies prior to the infection significantly reduced the S. aureus adhesion level to injured corneal epithelium (p < 0.001). Finally, S. aureus clinical isolates triggered its internalization in human corneal epithelial cells as efficiently as the 8325-4 wt.ConclusionS. aureus was almost unable to bind the intact corneal epithelium, whereas a superficial epithelial injury of the corneal epithelium strongly increased S. aureus adhesion, which is mainly driven by the interaction between staphylococcal fibronectin-binding proteins and unmasked fibronectin molecules located underneath the most superficial layer of the corneal epithelium.

Virulence Genes of Staphylococcus aureus Associated With Keratitis, Conjunctivitis, and Contact Lens–Associated Inflammation

“…The virulence factors of S. aureus that have been associated with microbial keratitis (MK) include genes encoding adhesins clfA , 27 fnbpA , 18 , 28 , 29 eap , 18 and coa 24 and evasins scpA , sspB , 18 , 30 , hla , 20 , 21 sspA , 31 and invasins coa 24 hlg. 25 , 26 , 32 The virulence factor of S. aureus that has been associated with conjunctivitis is pvl 23 ; seb is reported to be involved in contact lens corneal infiltrative events.…”

Staphylococcus aureus and Pseudomonas aeruginosa infectious keratitis: key bacterial mechanisms that mediate pathogenesis and emerging therapeutics

“…Specifically, Maurin et al. found that fibronectin-binding proteins were the principal driving factor for epithelial invasion, especially in injured epithelium ( Maurin et al., 2021 ). Similarly, collagen-binding adhesion (coa) promotes bacterial attachment to the corneal surface, and in a rabbit model of keratitis, may also promote a more severe suppurative keratitis ( Rhem et al., 2000 ).…”

“…Other S. aureus virulence factors that have been implicated in keratitis include fibronectin-binding protein, collagen-binding adhesion, Staphopain A, and Eap. Fibronectin-binding protein mediates attachment of bacteria to fibronectin molecules on the surface of corneal epithelial cells which is a precursor for host cellular invasion (Jett and Gilmore, 2002;Maurin et al, 2021). Specifically, Maurin et al found that fibronectin-binding proteins were the principal driving factor for epithelial invasion, especially in injured epithelium (Maurin et al, 2021).…”

“…Fibronectin-binding protein mediates attachment of bacteria to fibronectin molecules on the surface of corneal epithelial cells which is a precursor for host cellular invasion (Jett and Gilmore, 2002;Maurin et al, 2021). Specifically, Maurin et al found that fibronectin-binding proteins were the principal driving factor for epithelial invasion, especially in injured epithelium (Maurin et al, 2021). Similarly, collagen-binding adhesion (coa) promotes bacterial attachment to the corneal surface, and in a rabbit model of keratitis, may also promote a more severe suppurative keratitis (Rhem et al, 2000).…”

New Insight in Pain Relief and Reparative Efficacy of rh-EGF on Rabbit Corneal Injury Running title：Rh-EGF: Pain Relief and Repair in Corneal Injury

“…The stromal layer's bers are ensheathed by a protein with hydrating properties, allowing light to pass through freely [2] . External physical stimuli [3] , bacterial infections [4] , surgeries [5] , environmental pollutions [6] , or high-pressure gas impact [7] often result in corneal damage, leading to the loss of central epithelial cells and limbal epithelial cells [8] . Upon corneal injury, interleukin (IL)-1α and IL-1β are released, permeating the corneal stroma to bind with IL-1 receptors, initiating apoptosis in corneal cells [9][10][11][12] .…”