Antibody studies in a rabbit model of corneal phlyctenulosis and catarrhal infiltrates related to Staphylococcus aureus

Abstract

Hypersensitivity to ribitol teichoic acid (RTA), the major antigenic determinant of Staphylococcus aureus, may be important in a rabbit model of corneal phlyctenules and catarrhal infiltrates. Over a 5-month period, an enzyme-linked immunosorbent assay was used to measure immunoglobulin (Ig) G and IgA antibody levels to RTA in sera, tears, and corneas from rabbits immunized using the following routes: Group 1, intradermal injections of S. aureus cell wall (CW) mixed with complete Freund's adjuvant (CFA); Group 2, subconjunctival injections of CW-CFA; Group 3, prolonged topical application of viable S. aureus to the eye; Group 4, intradermal injections of CW-CFA plus prolonged topical application of viable S. aureus; and Group 5, subconjunctival injections of CW-CFA plus prolonged topical application of viable S. aureus. Over the 5-month period, the IgG and IgA antibody levels were correlated to RTA with the development of corneal phlyctenules and catarrhal infiltrates. The IgG titers to RTA were higher than IgA titers in serum, tears, and cornea. The highest antibody titers were IgG titers in cornea. Only rabbits immunized by intradermal or subconjunctival injections of CW-CFA followed by prolonged topical application of viable S. aureus (Groups 4 and 5) developed moderate to severe conjunctival hyperemia and edema with corneal phlyctenules and catarrhal infiltrates. When corneal lesions developed between 2-3 months, both groups had the highest corneal IgG and IgA antibody titers to RTA with IgG titers being more than 60 times higher than IgA titers. In the remaining 2 months of the study, the conjunctival response in both groups decreased from moderate-to-severe to mild, and no new corneal lesions developed, despite continued topical application of viable S. aureus and elevated antibody titers in cornea, serum, and tears. In this study, IgG and IgA antibody levels to RTA were measured in serum, tears, and cornea in a rabbit model of corneal phlyctenules and catarrhal infiltrates, and the antibody response was correlated with the development of these hypersensitivity lesions.