INDUCTION OF ALPHA BETA INTERFERON AND DEPENDENT NITRIC-OXIDE SYNTHESIS DURING CHLAMYDIA-TRACHOMATIS INFECTION OF MCCOY CELLS IN THE ABSENCE OF EXOGENOUS CYTOKINE/

The propensity of two Chlamydia trachomatis strains (L2/434/Bu [biovar LGV] and E/DK20/ON [biovar trachoma]) to induce putative host defense responses upon infection of McCoy (mouse) cell cultures was examined, Both strains induced production of alpha/beta interferon and nitric o xide (NO) by McCoy cells, NO synthesis was mediated by the inducible i soform of NO synthase as indicated by the ability of cycloheximide or the arginine analog N-G-monomethyl-L-arginine to abolish NO production ; the extent of the response was dependent upon the dose of chlamydiae applied, Incubation of McCoy cells with chloramphenicol prior to infe ction reduced NO production by strain 434 but not by DK2O, suggesting that initial chlamydial metabolism was essential to induction by the L GV strain, Antibody inhibition studies indicated that NO synthesis was dependent upon production of alpha/beta interferon and induction via lipopolysaccharide, Overall, our findings show that chlamydiae are cap able of the induction of interferon and NO in murine fibroblasts in th e absence of exogenous cytokines, However, the role of NO as an antich lamydial effector could not be clearly demonstrated since treatment wi th an arginine analog, while suppressing NO production, gave no consis tent enhancement of infected cell numbers.