Conditions for bacille Calmette-Guérin-induced resistance to infection with Schistosoma mansoni in mice.

Intravenous administration of a lyphilized preparation of bacille Calmette-Guérin (BCG-Tice) into mice significantly protected these animals from infection with Schistosoma mansoni. The protective effect depended on the dose of BCG and required the administration of at least 2 X 10(7) viable organisms. The route of administration of BCG was also crucial, as only intravenous inoculation produced significant protection. The BCG-induced resistance was found to last for eight weeks. Significant inflammation of the lungs was observed in mice receiving either viable or heat-killed BCG; however, protection followed only the administration of viable bacilli. Expression of BCG-induced protection was dependent on the presence of significant numbers of viable organisms and may have been associated with pulmonary inflammation at the time of passage of the schistosomula through the lungs.