CXCR2−/− Mice Show Enhanced Susceptibility to Herpetic Stromal Keratitis: A Role for IL-6-Induced Neovascularization

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Abstract
Ocular infection with HSV results in a blinding immunoinflammatory lesion known as herpetic stromal keratitis (HSK). Early preclinical events include inflammatory cell, mainly neutrophils, infiltration of the stroma, and neovascularization. To further evaluate the role of neutrophils in pathogenesis, HSV infection was compared in BALB/c and mice of the same background, but lacking CXCR2, the receptor for chemokines involved in neutrophil recruitment. Our results show clear differences in the outcome of ocular HSV infection in CXCR2−/− compared with control BALB/c mice. Thus, CXCR2−/− animals had minimal PMN influx during the first 7 days postinfection, and this correlated with a longer duration of virus infection in the eye compared with BALB/c mice. The CXCR2−/− mice were also more susceptible to HSV-induced lesions and developed HSK upon exposure to a dose of HSV that was minimally pathogenic to BALB/c mice. The basis for the greater HSK lesion susceptibility of CXCR2−/− mice was associated with an elevated IL-6 response, which appeared in turn to induce the angiogenic factor, vascular endothelial growth factor. Our results serve to further demonstrate the critical role of angiogenesis in the pathogenesis of ocular lesions.