The Role of C-X-C Chemokines in Staphylococcus aureus Endophthalmitis

Purpose: To test the hypothesis that the C-X-C chemokines CXCL1, CXCL2, and CXCL10 contribute to inflammation during Staphylococcus aureus endophthalmitis. Methods: S. aureus endophthalmitis was induced by intravitreal injection of 5000 colony forming units of S. aureus into the eyes of C57BL/6J, CXCL1-/-, CXCL2-/-, or CXCL10-/- mice. At 12, 24, and 36 hours postinfection, bacterial counts, intraocular inflammation, and retinal function were assessed. Based on these results, the effectiveness of intravitreal administration of anti-CXCL1 in reducing inflammation and improving retinal function was evaluated in S. aureus-infected C57BL/6J mice. Results: We observed significant attenuation of inflammation and improvement in retinal function in CXCL1-/- mice relative to C57BL/6J at 12 hours but not at 24 or 36 hours postinfection with S. aureus. Co-administration of anti-CXCL1 antibodies with S. aureus, however, did not improve retinal function or reduce inflammation at 12 hours postinfection. In CXCL2-/- and CXCL10-/- mice, retinal function and intraocular inflammation were not significantly different from those of C57BL/6J mice at 12 and 24 hours postinfection. At 12, 24, or 36 hours, an absence of CXCL1, CXCL2, or CXCL10 did not alter intraocular S. aureus concentrations. Conclusions: CXCL1 appears to contribute to the early host innate response to S. aureus endophthalmitis, but treatment with anti-CXCL1 did not effectively limit inflammation in this infection. CXCL2 and CXCL10 did not seem to play an integral role in inflammation during the early stages of S. aureus endophthalmitis.