Recombinant interleukin-2 limits the replication of Mycobacterium lepraemurium and Mycobacterium bovis BCG in mice

BALB/c mice were infected with Mycobacterium lepraemurium in the footpad or with Mycobacterium bovis BCG intravenously with 5 x 10(7) bacilli. Recombinant interleukin-2 (IL-2) was injected intraperitoneally as a single dose (20,000 U), as a single course of five injections (400 U each), or as a 6-month course starting 3 days after the M. lepraemurium infection. BCG-infected mice received a single dose (1,000 U) or five daily injections of 100 or 1,000 U each. IL-2 significantly reduced the total bacterial counts in the footpad, lymph nodes, and liver of M. lepraemurium-infected mice (50 to 85%) by 6 months and viable counts in the spleen (30 to 50%) by 60 days after BCG infection. The courses of IL-2 started at 60 days were more effective than those started at 3 days after M. lepraemurium infection (P less than 0.05 to 0.001), and for BCG, 100 U of IL-2 was better than 1,000 U (P less than 0.05 to 0.01). These results indicate that IL-2 limits mycobacterial infections in mice and raise the question of its possible use in humans.