Distinct sensitivity of the corneal P. aeruginosa clinical isolates to neutrophil extracellular trap-mediated immunity (INM8P.449)

Abstract

Abstract Ocular bacterial keratitis is a frequent sight-threatening condition usually associated with P. aeruginosa infection. In this study we analyzed the contribution of the neutrophil extracellular traps (NETs) in mediating protection during ocular keratitis. Both, invasive and cytotoxic, P. aeruginosa clinical isolates induced NET release by neutrophils. NETs shared a common protein signature regardless of the inducing stimuli and were decorated with histones, elastase, lysozyme, myeloperoxidase, and metabolic enzymes. While the cytotoxic P. aeruginosa strains 6077 and 6206 strains (serogroup O11) and PA14 (serogroup 010) were resistant to NET capture, the invasive P. aeruginosa strains PAO1 (serogroup O5), 6294 (serogroup O6) were trapped by NETs. The mechanism of escape of the cytotoxic strains from adhesion to NETs depended on shedding of outer membrane vesicles (OMV) that competed with P. aeruginosa for NET binding. Unlike cytotoxic strains, NETs adherent invasive strains were weakly sensitive to NET-mediated killing. When ocular infection was caused by invasive strain, NETs were released at the ocular surface to capture bacteria, limiting it’s spread. Treatment with DNase I facilitated the clearance of NET-captured bacteria, decreasing ocular bacterial burden and disease pathology. Cumulatively, these data suggest that current therapeutic strategies might utilize DNAse I to promote recovery from acute keratitis.