IN-VIVO CHARACTERIZATION OF HOST AND BACTERIAL PROTEASE EXPRESSION DURING PSEUDOMONAS-AERUGINOSA CORNEAL INFECTIONS IN NAIVE AND IMMUNIZED MICE

Purpose. The corneal destruction resulting from P. aeruginosa keratiti s is thought to be due, in part, to the actions of host and bacterial proteases on corneal tissue. The intent of the current study was to co mpare host and bacterial protease expression in the ocular tissues of mice that have been shown to be susceptible to corneal infection with mice that have been protected from such infection as a result of prior immunization. Methods. Supernatants of infected corneal homogenates f rom naive mice or from mice immunized as a result of prior corneal inf ection or that had been immunized against bacterial protease were anal yzed by gelatin zymography for the presence of host gelatinases and ba cterial proteases at various times after infection. In addition, studi es were carried out to examine the effect of immunization with bacteri al protease on numbers of ocular bacteria. Results. Mice that were pro tected against the tissue destruction during infection were found to h ave reduced proteolytic activity in corneal tissues when compared with susceptible mice. More specifically, the resistant mice displayed low er levels of bacterial alkaline protease, latent MMP-2, and both the a ctive and latent forms of MMP-9. In addition, immunization against eit her bacterial alkaline protease or elastase failed to reduce bacterial numbers in ocular tissues from 6 to 72 hours after infection. Conclus ions. These results suggest that increased proteolytic activity in ocu lar tissues during P. aeruginosa infection may contribute to the irrev ersible corneal damage observed during the infection.