BCG vaccination and experimental corneal tuberculosis in the mouse

Abstract

By giving viable BCG organisms intravenously to mice an immunity has been set up which protects against subsequent corneal tuberculosis experimentally induced. The degree of protection has been quantitatively related to the dose of vaccine employed. This immunity takes about four weeks to reach its maximum and remains thus for a few weeks and later diminishes gradually but is not lost altogether by twenty-eight weeks. A heat-killed vaccine of the same dosage has proved ineffective, while treating the mice with isoniazid after vaccination has considerably reduced the level of immunity from that otherwise expected. Cortisone, too, given after the challenge corneal infection, has overcome the vaccination immunity. A comparison of similar doses of bovine, BCG and H37Ra strains of tubercle bacilli as vaccines has shown the first of these to be the most potent, with the other two of a similar order of potency. Reconstituted freeze-dried BCG vaccines have also been satisfactory for establishing immunity in mice, their capacities in this respect being apparently determined by the number of viable organisms contained therein. The possibility of using the intracorneal technique for estimating the potency of antituberculosis vaccines is considered.