Greater protection against M. tuberculosis aerosol challenge by vaccination with hly⁺ rBCG⁺ and ΔureC hly⁺ rBCG. (A) BALB/c mice were vaccinated with hly⁺ rBCG (triangles) or parental BCG (circles) or left naive (squares). At day 120 after vaccination, mice were aerosol challenged with 200 CFU of M. tuberculosis H37Rv. P = 0.016 (Mann-Whitney U test) for hly⁺ rBCG compared with parental BCG at day 150 after infection (p.i.). Shown is 1 representative experiment of 2. The mean of results from 7 mice is shown (± SEM). (B and C) BALB/c mice were vaccinated with ΔureC hly⁺ rBCG (diamonds) or parental BCG (circles) or left naive (squares). At day 120 after vaccination, mice were aerosol challenged with 30 CFU (B) and 200 CFU (C) of M. tuberculosis H37Rv. M. tuberculosis load in lung was determined at the indicated time points. Shown are 2 representative experiments. *P = 0.0012 and **P = 0.001 (Mann-Whitney U test) for ΔureC hly⁺ rBCG compared with parental BCG at day 90 p.i. The mean of results for 7 mice is shown (± SEM).