All mice, pre-immunized with wild type Lm, the wild type L.inn strain and the L.inn::vgc strain were challenged 2 months later with a 206LD 50 (10 5 ) lethal dose of wild type Lm. A group of non preimmunized Balb/c mice were included as controls. Survival of mice was monitored for several days and expressed as percentage of animals surviving challenge with Lm.