Abstract
A state of marked resistance of the toxic corneal effects of Newcastle virus (NDV) was observed in rabbit eyes after intravenous injection of 10 or 100 [mu]g of thyphoid endotoxin. By use of tissue cultures of rabbit corneal endothelial cells for assay, higher titers of an inter-teron-like viral inhibitor were detected in serum and in ocular aqueous homor of these animals. The pretreatment of eyes with aqueous humor or serum containing the inhibitor markedly suppressed the production of corneal toxicity by NDV. The intravenous injection of 1 [mu]g of the endotoxin had a negligible effect on the corneal reaction, and little or no inhibitor was found in either serum or aqueous humor. Normal aqueous homor or serum contained no inhibitor and had no suppressive effect on the NDV-induced reactions. The results indicated that the inhibitor played an important role in the induction of corneal resistance to NDV in vivo. The inhibitor in aqueous humor of endotoxin-injected rabbits was found to be derived from blood after an increase in the permeability of "blood-aqueous barrier" of iris due to the endotoxin. Therefore, intravenously administered thyphoid endotoxin induced corneal resistance to NDV in rabbits through its dual action on host: (i) release of an interferon-like viral inhibitor into the blood stream and (ii) distuption of the blood-aqueous barrier of the iris, thus allowing the passage of the viral inhibitor from blood into the anterior chamber, where it modified the corneal endothelial cells to render them resistant to NDV.