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Mihaela Gadjeva; Impact of commensals on ocular immunity to infection. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5772.
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© ARVO (1962-2015); The Authors (2016-present)
The impact of ocular exposure to commensal organisms on immunity of the eye remains controversial. Over the past year we accumulated evidence that commensal species promote resistance to infection with P. aeruginosa.
Ocular swabs were collected from Swiss Webster and C57BL/6N male and female mice from different vendors and animal facilities. Commensal species were identified using standard microbiology culturing techniques and mass spectroscopy analysis. Mice were treated with topical antibiotics to ablate culturable bacterial presence in the conjunctiva, then rested, and subsequently colonized with different commensal strains including CNS xylosus, Streptococcus oralis. Commensal presence was monitored for three weeks to determine colonization capacity. The impact of colonizing commensal species on immunity to P. aeruginosa and mechanisms of protection were examined.
We observed that commensal strains like Streptococus oralis and Corynebacterium mastitidis colonize conjuncival surfaces for extended periods of time. They were recoverable from the conjunctival swabs as late as 3 weeks after the initial exposure. The presence of commensals significantly promoted immunity to P. aeruginosa by facilitating neutrophil recruitment to CALT in an IL-1-dependent mechanism. Neutrophil trafficking to the cornea during infection was dependent on L-plastin, an adaptor protein connecting actin filaments. Consistently, L-plastin knockout mice had elevated bacterial burdens in the cornea and significanlty increased pathology as keratitis progressed.
Our data suggest that tonic signals from local commensal flora continuously induce surveillance of the ocular mucosa limiting microbial presence at the ocular surfaces and strengthening protection during infection.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Variety of conjunctival commensals grown from mice.
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