Effect of interferon on a primary conjunctival epithelial cell model of trachoma.

This content is PDF only. Please click on the PDF icon to access.

Abstract

An in vitro human primary conjunctival epithelial system was adapted to determine if the effects of interferon-gamma (IFN-gamma), as described in cultured cell lines, were applicable to human ocular infection with Chlamydia trachomatis, Primary human epithelial cell cultures were exposed to varying concentrations of IFN-gamma. The treatment resulted in the induction of the tryptophan decyclizing enzyme indolamine 2,3-deoxygenase (IDO) in a dose-dependent manner as determined by assaying the conversion of tryptophan to its metabolites using reversed-phase high-performance liquid chromatography. Little IDO induction occurred in the presence of IFN-alpha or IFN-beta. Catabolism of up to 38% of available tryptophan occurred in IFN-gamma-treated cells in contrast to controls that showed only baseline activity. Cells cultured with IFN-gamma and then infected with an ocular isolate of C. trachomatis (TW-5), had a reduction in the percentage of inclusion-containing cells by over 80% in a dose-dependent manner. Reversal by the addition of exogenous tryptophan substantiated that IFN-gamma-mediated induction of IDO and catabolism of tryptophan were responsible for inhibition of intracellular growth of C. trachomatis.