Effector Mechanisms of Protection againstPseudomonas aeruginosaKeratitis in Immunized Rats

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen which causes sight-threatening corneal infections in humans. The purpose of this study was to evaluate various immunization routes that may provide protection against Pseudomonas keratitis and to define the molecular mechanisms involved in the protection. SpragueDawley rats (10 to 12 weeks old) were immunized using paraformaldehyde-killed P. aeruginosa (strain 6206) via oral, nasal, and intra-Peyer's patch (IPP) routes followed by an ocular topical booster dose. Scratched corneas were challenged with an infective dose of P. aeruginosa. Following clinical examination, eyes were enucleated for histology, polymorphonuclear leukocyte (PMN) quantitation, bacterial count, enzyme-linked immunosorbent assay, and RNase protection assay. PMN infiltration was higher early (4 h) during the infection in immunized rats than in nonimmunized rats. Later during the infection, the number of PMNs diminished in immunized rats while in nonimmunized animals the number of PMNs continued to increase. Bacteria were cleared much faster from immunized groups than from the nonimmunized group, and the nasally immunized group had the most efficacious response among the immunized groups. Nasal and IPP immunization groups had increased cytokine expression of interleukin-2 (IL-2) and IL-5 and differed from each other for IL-6. All three immunized groups had significantly reduced IL-1␤ levels when compared with the nonimmunized rats and a significantly altered profile for CINC-1 expression. This study has shown that the route of immunization modulates the inflammatory response to ocular P. aeruginosa infection, thus affecting the severity of keratitis and adverse pathology, with nasal immunization being the most effective.

Pathological findings in cornea tissue of patients with penetrating keratoplasty.

“…Local production of antibodies specific to different viral or microbial agents in cornea has been documented [14][15][16]. In our study some corneas were positive for immunoglobulins and inflammatory cells simultaneously.…”

A Live-Attenuated Pseudomonas aeruginosa Vaccine Elicits Outer Membrane Protein-Specific Active and Passive Protection against Corneal Infection

“…They found that, compared with oral and intra-Peyer's patch routes, nasal immunization resulted in the fastest bacterial clearance. In comparison with unimmunized rats, polymorphonuclear leukocyte (PMN) infiltration in the eyes of immunized rats was higher early during the infection, while at later points the number of PMNs diminished in immunized rats but continued to increase in the unimmunized group (42).…”

“…More recently, however, and despite these potential issues, protective efficacy using active immunization was achieved in the studies of Thakur and coworkers (42), who evaluated various routes of immunization of rats with paraformaldehydekilled P. aeruginosa. They found that, compared with oral and intra-Peyer's patch routes, nasal immunization resulted in the fastest bacterial clearance.…”

“…In rats, nasal immunization has been reported to be the most efficacious route for protection against corneal infection (42). In the current study, we evaluated the protective efficacies against murine corneal infection of active and passive immunization with PAO1⌬aroA and of therapy with a rabbit antiserum raised against PAO1⌬aroA.…”

Microbiota-Driven Immune Cellular Maturation Is Essential for Antibody-Mediated Adaptive Immunity to Staphylococcus aureus Infection in the Eye

“…It has become increasingly apparent that endogenous innate immune factors can also be important components for efficacy of acquired immune effectors such as antibodies (28,29), notably as cofactors in vaccine-induced immunity in the lung (30)(31)(32). We therefore evaluated the role of T cells and the IL-17/IL-22 pathways in antibody-mediated reductions in corneal pathology and bacterial levels in S. aureus-infected eyes.…”