1
|
Livingston ET, Mursalin MH, Callegan MC. A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections. Microorganisms 2019; 7:E537. [PMID: 31703354 PMCID: PMC6920826 DOI: 10.3390/microorganisms7110537] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 11/03/2019] [Accepted: 11/05/2019] [Indexed: 12/21/2022] Open
Abstract
Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This "Pyrrhic Victory" scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.
Collapse
Affiliation(s)
- Erin T. Livingston
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (E.T.L.); (M.H.M.)
| | - Md Huzzatul Mursalin
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (E.T.L.); (M.H.M.)
| | - Michelle C. Callegan
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (E.T.L.); (M.H.M.)
- Department of Ophthalmology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Oklahoma Center for Neuroscience, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Dean McGee Eye Institute, Oklahoma City, OK 73104, USA
| |
Collapse
|
2
|
Tullos NA, Thompson HW, Taylor SD, Sanders M, Norcross EW, Tolo I, Moore Q, Marquart ME. Modulation of immune signaling, bacterial clearance, and corneal integrity by toll-like receptors during streptococcus pneumoniae keratitis. Curr Eye Res 2013; 38:1036-48. [PMID: 23841825 DOI: 10.3109/02713683.2013.804094] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
PURPOSE Bacterial keratitis, without effective antimicrobial treatment, leads to poor patient prognosis. Even after bacterial clearance, the host inflammatory response can contribute to corneal damage. Though Streptococcus pneumoniae (pneumococcus) is a common cause of bacterial keratitis, the role of host innate immunity during pneumococcal keratitis is not well characterized. This study investigated the role of Toll-like receptors (TLRs) during pneumococcal keratitis. MATERIALS AND METHODS C57BL/6, as well as TLR2(-/-) and TLR4(-/-) mice, were infected with S. pneumoniae, and infected corneas were examined for 21 days. Quantitative real-time reverse-transcriptase polymerase chain reaction was performed using primers for genes involved in the inflammatory response and TLR signaling. Bacterial survival and leukocyte invasion were examined over a 72-h period. RESULTS The corneal expression of TLR2, TLR4, and other inflammatory genes was increased at 72 h post-infection (p.i.) compared to uninfected C57BL/6 scratch controls. TLR2(-/-) mice showed a significant increase in bacterial survival at 24 h p.i. likely due to decreased neutrophil infiltration; however, after Day 5 p.i. observed clinical scores of TLR2(-/-) and C57BL/6 mice were not significantly different. In contrast, permanent corneal damage was observed for TLR4(-/-) mice over 21 days. Initially, both TLR(-/-) mouse strains exhibited lower expression levels in many immune genes, but returned to similar or elevated levels compared to C57BL/6 mice by 72 h p.i. CONCLUSIONS TLR2 and TLR4 are involved in the response to pneumococcal keratitis and TLR2 may aid in bacterial clearance by recruitment of neutrophils to the cornea, whereas TLR4 may be necessary to modulate the immune response to limit cellular damage.
Collapse
Affiliation(s)
- Nathan A Tullos
- Department of Microbiology, University of Mississippi Medical Center, Jackson, MS, USA
| | | | | | | | | | | | | | | |
Collapse
|
3
|
Infectious keratitis: secreted bacterial proteins that mediate corneal damage. J Ophthalmol 2013; 2013:369094. [PMID: 23365719 PMCID: PMC3556867 DOI: 10.1155/2013/369094] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 12/12/2012] [Indexed: 12/17/2022] Open
Abstract
Ocular bacterial infections are universally treated with antibiotics, which can eliminate the organism but cannot reverse the damage caused by bacterial products already present. The three very common causes of bacterial keratitis—Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae—all produce proteins that directly or indirectly cause damage to the cornea that can result in reduced vision despite antibiotic treatment. Most, but not all, of these proteins are secreted toxins and enzymes that mediate host cell death, degradation of stromal collagen, cleavage of host cell surface molecules, or induction of a damaging inflammatory response. Studies of these bacterial pathogens have determined the proteins of interest that could be targets for future therapeutic options for decreasing corneal damage.
Collapse
|
4
|
Moore QC, McCormick CC, Norcross EW, Onwubiko C, Sanders ME, Fratkin J, McDaniel LS, O'Callaghan RJ, Marquart ME. Development of a Streptococcus pneumoniae keratitis model in mice. Ophthalmic Res 2009; 42:141-6. [PMID: 19628954 DOI: 10.1159/000229028] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Accepted: 04/16/2009] [Indexed: 11/19/2022]
Abstract
BACKGROUND Streptococcus pneumoniae is a common cause of bacterial keratitis, and models to examine the ocular pathogenesis of this bacterium would aid in efforts to treat pneumococcal keratitis. The aim of this study was to establish a murine model of pneumococcal keratitis. METHODS The corneas of A/J, BALB/c or C57BL/6 mice were scratched and topically infected with a clinical strain of S. pneumoniae. Slitlamp examination (SLE), enumeration of bacteria in the corneas and histology were performed. RESULTS Bacteria were recovered from the eyes of A/J mice on postinfection (PI) days 1 [1.96 +/- 0.61 log(10) colony-forming units (CFU)] and 3 (1.41 +/- 0.71 log(10) CFU). SLE scores were significantly higher in the infected A/J mice as compared to the BALB/c or C57BL/6 mice on PI day 3 (p < 0.0001) and steadily increased over time, reaching a maximal value of 3.00 +/- 0.35 on PI day 10. Histopathology revealed stromal edema and the influx of polymorphonuclear leukocytes on PI days 7 and 10, and corneal disruption on PI day 7. CONCLUSIONS S. pneumoniae keratitis was established in A/J mice, but not BALB/c or C57BL/6 mice.
Collapse
Affiliation(s)
- Quincy C Moore
- Department of Microbiology, University of Mississippi Medical Center, Jackson, Miss. 39216, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Green SN, Sanders M, Moore QC, Norcross EW, Monds KS, Caballero AR, McDaniel LS, Robinson SA, Onwubiko C, O'Callaghan RJ, Marquart ME. Protection from Streptococcus pneumoniae keratitis by passive immunization with pneumolysin antiserum. Invest Ophthalmol Vis Sci 2008; 49:290-4. [PMID: 18172105 DOI: 10.1167/iovs.07-0492] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine whether passive immunization with pneumolysin antiserum can reduce corneal damage associated with pneumococcal keratitis. METHODS New Zealand White rabbits were intrastromally injected with Streptococcus pneumoniae and then passively immunized with control serum, antiserum against heat-inactivated pneumolysin (HI-PLY), or antiserum against cytotoxin-negative pneumolysin (psiPLY). Slit lamp examinations (SLEs) were performed at 24, 36, and 48 hours after infection. An additional four corneas from rabbits passively immunized with antiserum against psiPLY were examined up to 14 days after infection. Colony forming units (CFUs) were quantitated from corneas extracted at 20 and 48 hours after infection. Histopathology of rabbit eyes was performed at 48 hours after infection. RESULTS SLE scores at 36 and 48 hours after infection were significantly lower in rabbits passively immunized with HI-PLY antiserum than in control rabbits (P < or = 0.043). SLE scores at 24, 36, and 48 hours after infection were significantly lower in rabbits passively immunized with psiPLY antiserum than in control rabbits (P < or = 0.010). The corneas of passively immunized rabbits that were examined up to 14 days after infection exhibited a sequential decrease in keratitis, with an SLE score average of 2.000 +/- 1.586 at 14 days. CFUs recovered from infected corneas were not significantly different between each experimental group and the respective control group at 20 or 48 hours after infection (P > or = 0.335). Histologic sections showed more corneal edema and polymorphonuclear leukocyte (PMN) infiltration in control rabbits compared with passively immunized rabbits. CONCLUSIONS HI-PLY and psiPLY both elicit antibodies that provide passive protection against S. pneumoniae keratitis.
Collapse
Affiliation(s)
- Sherrina N Green
- Department of Microbiology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Abstract
Pneumolysin is a thiol-activated membrane-damaging toxin produced by Streptococcus pneumoniae. The toxin plays a role in virulence of the pneumococcus in animal models of infection. Pneumolysin has a range of biological activity including the ability to lyse eukaryotic cells and to interfere with the function of cells and soluble molecules of the immune system. The use of purified native and mutant toxin and of isogenic mutants of the pneumococcus expressing altered versions of the toxin has allowed the contribution of the various activities of this multifunctional toxin to virulence to be defined.
Collapse
Affiliation(s)
- T J Mitchell
- Division of Infection and Immunity, University of Glasgow, Scotland
| | | |
Collapse
|
7
|
Johnson MK, Callegan MC, Engel LS, O'Callaghan RJ, Hill JM, Hobden JA, Boulnois GJ, Andrew PW, Mitchell TJ. Growth and virulence of a complement-activation-negative mutant of Streptococcus pneumoniae in the rabbit cornea. Curr Eye Res 1995; 14:281-4. [PMID: 7606914 DOI: 10.3109/02713689509033527] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Our previous work has demonstrated the importance of pneumolysin in the virulence of S. pneumoniae in a rabbit intracorneal model. This was accomplished by showing that deletion of the gene encoding pneumolysin resulted in reduced virulence, whereas restoration of the wild-type gene resulted in restoration of the virulent phenotype. To assess the importance of a particular domain in the pneumolysin molecule, we have now constructed a strain which produces a pneumolysin molecule which is hemolytic but which bears a site-specific mutation in the domain known to be associated with the complement-activating properties of this molecule. Comparison of the virulence of this strain with that of a strain bearing the wild-type gene showed statistically significantly lower total slit lamp examination (SLE) scores at 12, 18, 24, and 36 h (particularly with respect to fibrin formation), but no difference at 48 h. Determination of colony forming units (CFU) in eyes infected with the two strains showed approximately 10(6) bacteria per cornea until 36 h. Between 36 and 48 h, the bacteria were almost completely cleared with very few bacteria recoverable at the later time point. The loss of virulence observed with this mutation in the complement-activation domain of pneumolysin, though less than that observed with the gene deletion mutant, suggests that complement activation by pneumolysin has a significant role in the pathology observed in this model of corneal infection.
Collapse
Affiliation(s)
- M K Johnson
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Callegan MC, O'Callaghan RJ, Hill JM. Pharmacokinetic considerations in the treatment of bacterial keratitis. Clin Pharmacokinet 1994; 27:129-49. [PMID: 7955776 DOI: 10.2165/00003088-199427020-00005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The eye is relatively impermeable to micro-organisms and other environmental elements. However, if corneal integrity is breached by trauma, a sight-threatening bacterial infection can result. Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae are the most common bacterial pathogens associated with infection of compromised corneas. Bacterial enzymes and toxins, as well as factors associated with the host immune response, can lead to tissue destruction during corneal infection. For successful therapy, an antibacterial agent must be active against the pathogen and must be able to overcome the permeability barrier of the cornea. Topical application of antibacterial agents adequately delivers drugs to the cornea and aqueous humour. However, drug concentrations at the site of infection are not always sufficient to rapidly kill infective organisms. Infections with antibiotic-resistant strains present an even greater therapeutic challenge. In addition, sterilisation of the cornea by antibacterial agents does not eliminate inflammation and corneal scarring that accompany infection. Steroidal and non-steroidal antiinflammatory agents limit corneal scarring during experimentally induced bacterial keratitis. However, although promising, concomitant use of these drugs with antibacterial agents remains controversial. Two ocular drug delivery systems that provide high and sustained concentrations of drug to ocular tissues are corneal collagen shields and transcorneal iontophoresis. The collagen shield, originally designed as a bandage lens, prolongs drug contact with the cornea. Chemotherapeutic studies of experimental bacterial keratitis demonstrate that shields hydrated with antibacterial agents reduce bacteria in the cornea as well as or better than frequent applications of fortified antibacterial drops. Transcorneal iontophoresis uses an electric current to drive charged drugs into the cornea. In experimentally induced bacterial keratitis, transcorneal iontophoresis of antibacterial agents is superior to topically administered ocular drops for reducing the numbers of bacteria in the cornea. Although both drug delivery systems appear to be well tolerated and nontoxic in animal models, clinical trials in patients are required to determine the usefulness of these drug delivery systems in clinical trials. Based on present experimental results, future therapy of bacterial keratitis will involve efficient drug delivery devices, the use of new antibacterial agents or combinations of presently available antibacterial agents, and careful use of adjuvant anti-inflammatory agents.
Collapse
Affiliation(s)
- M C Callegan
- Department of Microbiology, Louisiana State University Medical Center School of Medicine, New Orleans
| | | | | |
Collapse
|
9
|
Hobden JA, Engel LS, Callegan MC, Hill JM, Gebhardt BM, O'Callaghan RJ. Pseudomonas aeruginosa keratitis in leukopenic rabbits. Curr Eye Res 1993; 12:461-7. [PMID: 8344069 DOI: 10.3109/02713689309024628] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
To study the role of the host inflammatory response in Pseudomonas aeruginosa keratitis, rabbits were made leukopenic with intravenous injections of cyclophosphamide and dexamethasone. Twenty-four hr later, keratitis was initiated in all rabbits with an intrastromal injection of 1,000 log phase P. aeruginosa strain 27853. Slit lamp examination of eyes showed that leukopenic rabbits had significantly less (P < 0.0001) ocular pathology at 16, 22, and 27 hr postinfection. The number of viable bacteria recovered from corneas of leukopenic rabbits was the same as the number recovered from nonleukopenic rabbits (P = 0.95). These results suggest that the host inflammatory response significantly contributes to the overall ocular pathology associated with P. aeruginosa keratitis, but does not influence the survival of the infecting organism in the cornea at the height of the infection.
Collapse
Affiliation(s)
- J A Hobden
- Lions Eye Research Laboratories, Louisiana State University Medical Center School of Medicine, New Orleans 70112
| | | | | | | | | | | |
Collapse
|
10
|
Johnson MK, Hobden JA, Hagenah M, O'Callaghan RJ, Hill JM, Chen S. The role of pneumolysin in ocular infections with Streptococcus pneumoniae. Curr Eye Res 1990; 9:1107-14. [PMID: 2095322 DOI: 10.3109/02713689008997584] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Pneumolysin, a cytolytic protein produced by Streptococcus pneumoniae, has many properties which suggest it may be an important virulence factor in pneumococcal ocular infections. To directly test this possibility, we have constructed pneumolysin-negative strains of S. pneumoniae and compared their virulence with that of the wild type in a rabbit model of intracorneal infection. A pneumolysin-negative strain produced by chemical mutagenesis (probably a point mutant) was found to be no less virulent than the parent strain. However, a strain bearing a deletion in the pneumolysin gene showed greatly reduced virulence. This strain produced less pathology while showing significantly higher bacterial counts. These results suggest that a property of the pneumolysin molecule other than its cytolytic (hemolytic) activity may be involved in its pathogenic mechanism of action. This property may be the ability to activate complement, known to be a function of pneumolysin, which results in influx of PMNs, reducing the bacterial counts but also producing tissue damage.
Collapse
Affiliation(s)
- M K Johnson
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112
| | | | | | | | | | | |
Collapse
|
11
|
Johnson MK, Gebhardt BM, Berman MB. Appearance of collagenase in pneumolysin-treated corneal fibroblast cultures. Curr Eye Res 1988; 7:951-3. [PMID: 2846236 DOI: 10.3109/02713688808997252] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Sub-lethal levels of pneumolysin, a cytolytic toxin produced by the pneumococcus, have been shown to increase collagenase concentration in cultures of rabbit corneal fibroblasts. Interactions between pneumolysin and corneal cells may be involved in the pathogenesis of pneumococcal ocular infections.
Collapse
Affiliation(s)
- M K Johnson
- Department of Microbiology and Immunology, Tulane Medical Center, New Orleans, LA
| | | | | |
Collapse
|
12
|
Fielder RJ, Gaunt IF, Rhodes C, Sullivan FM, Swanston DW. A hierarchical approach to the assessment of dermal and ocular irritancy: a report by the British Toxicology Society Working Party on Irritancy. HUMAN TOXICOLOGY 1987; 6:269-78. [PMID: 3623573 DOI: 10.1177/096032718700600404] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
13
|
Abstract
Since its introduction 40 years ago, the Draize test for eye irritancy has remained largely unchanged in spite of long-standing controversy over ethical and scientific aspects. It is suggested that deficiencies in the data derived from the test which arise from defects in the basic test design, cannot be fully compensated for by supplementary methods or data handling schemes. As a limited amount of in vivo testing is still required, attempts should be made to improve the method by attention to the scientific principles involved, using current knowledge of inflammatory mechanisms. Proper attention to design and approach will help to resolve both the scientific deficiencies in the test and help to overcome the reservations that are currently felt with regard to the ethics of the test.
Collapse
|