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

BALB/c mice were infected with Mycobacterium lepraemurium (MLM) in the foot pad or with M. bovis BCG intravenously with 5 x 10(7) bacilli. Recombinant interleukin-2 (IL-2) was injected intraperitoneally as a single dose (20,000 u), single course of 5 injections (400 u each) or 6 monthly courses starting 3 days or 60 days after the MLM infection. BCG infected mice received a single dose (1000 u) or 5 daily injections of 100 or 1000 u each. IL-2 significantly reduced the total bacterial counts in the footpad, lymph node and liver of MLM infected mice (50-85%) by 6 months and viable counts in the spleen (30-50%) by 60 days after BCG infection. The courses of IL-2 started at 60 days were more effective than at 3 days after MLM infection (P less than 0.05-0.001) and in the case of BCG, 100 u of IL-2 was better than 1000 u (P less than 0.05-0.01). These results indicate that IL-2 limits mycobacterial infections in mice, and raise the question of its possible use in humans.