July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Absence of S-layer impacts pathogenesis of Bacillus endophthalmitis
Author Affiliations & Notes
  • Md Huzzatul Mursalin
    Microbiology and Immunology, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, United States
  • Phillip S Coburn
    Department of Ophthalmology, University of Oklahoma Health Science Center and Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
  • Erin Livingston
    Microbiology and Immunology, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, United States
  • Agnès Fouet
    Institut Cochin INSERM U1016, CNRS 8104, University Paris Descartes, Paris, France
  • Michelle C Callegan
    Microbiology and Immunology, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, United States
    Department of Ophthalmology, University of Oklahoma Health Science Center and Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
  • Footnotes
    Commercial Relationships   Md Huzzatul Mursalin, None; Phillip Coburn, None; Erin Livingston, None; Agnès Fouet, None; Michelle Callegan, None
  • Footnotes
    Support  R01EY024140; R01EY025947; R01EY28810; P30EY027125
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 6410. doi:
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      Md Huzzatul Mursalin, Phillip S Coburn, Erin Livingston, Agnès Fouet, Michelle C Callegan; Absence of S-layer impacts pathogenesis of Bacillus endophthalmitis. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6410.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To investigate the hypothesis that Bacillus S-layer protein (SLP) contributes to the pathogenesis of endophthalmitis, a rapidly blinding infection.

Methods : Wild-type (WT) and S-layer deficient (△slpA) Bacillus thuringiensis (B. thuringiensis) were compared for differences in phenotype and virulence. Endophthalmitis was induced in C57BL/6J mice by intravitreally injecting 100 cfu WT or △slpA B. thuringiensis. Infected eyes were analyzed by bacterial counts, retinal function analysis, histology, and neutrophil influx. Values represent N≥5, mean ± SEM. Nuclear proteins from human retinal Muller cells (MIO-M1) cells were extracted after treatment with SLP (10 µg/mL) and NF-kB activation was measured by ELISA. Total RNA was extracted from MIO-M1 cells treated with SLP (10 µg/mL ) or PBS for 10 hours and real-time qPCR was performed to examine the expression of inflammatory cytokines (IL-6, TNFα) and chemokines (CXCL-1, CCL2).

Results : Phenotypes were similar in WT and △slpA strains. The replication and localization of WT and △slpA B. thuringiensis in mouse eyes was similar. At 10 hours postinfection, both WT and △slpA B. thuringiensis were localized near the retina and in the anterior segment, as well as in the midvitreous. Surprisingly, the retention of retinal function in eyes infected with △slpA B. thuringiensis was greater than that of eyes infected with the WT strain at 8, 10, and 12 hours postinfection. In △slpA-infected eyes, retinas were intact, retinal layers were distinguishable, and inflammatory influx was minimal. In contrast, severe inflammation, anterior and posterior segment infiltration, and retinal detachments were observed in WT-infected eyes. Bacillus SLP was a potent stimulator of NF-κB pathway and induced the expression of proinflammatory mediators (IL6, TNFα, CXCL-1, and CCL2) in human retinal Muller cells.

Conclusions : Taken together, our results suggest that Bacillus SLP contributes to the pathogenesis of endophthalmitis, potentially by triggering innate inflammatory pathways in the retina. Further experiments will explore how S-layer drives innate immune recognition and acute inflammation in endophthalmitis and the utility of S-layer as a therapeutic target.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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