AGE AND GENDER-RELATED SPONTANEOUS BACTERIAL KERATITIS IN CD36KO MICE

Purpose: CD36 is a scavenger receptor with many ligands such as fatty acids, phospholipids, and TSP-1. While its main function is to clear apoptotic cells, CD36 is also required for full activation of TLR 2 triggered by Staphylococcus aureus. Although S. aureus is found in the normal flora of the ocular surface, mice do not spontaneously develop bacterial keratitis. Since both TLR 2 and CD36 are expressed in the cornea, we hypothesize that CD36 is required to prevent S. aureus keratitis. Methods: Corneas of CD36KO and wild-type C57BL/6 mice were screened via slit lamp. Corneas containing lesions were sectioned, stained, and examined microscopically. Bacterial load in corneal tissue was determined and Staphylococcus was identified by gram stain and ChromAgar. Serum was collected and analyzed for ANA (anti-nuclear antibodies). Results: CD36KO mice displayed spontaneous corneal lesions that increased in frequency and severity with age. High levels of Staphylococcus were found in corneas with severe lesions, and not controls. Severe corneal lesions showed a massive CD45+ infiltrate in the anterior part of the cornea. The frequency of corneal lesions in the colony was 74% (female) and only 26% (males). ANAs were found in the serum of older female mice with corneal lesions, but not in the controls. Conclusion: CD36KO mice develop spontaneous bacterial keratitis. The infection may be secondary to autoimmunity since the highest frequency of keratitis occurred in older female mice with ANA. This is the first report of a spontaneous bacterial keratitis in mice.