FIG. 1.

Generation and characterization of the L. monocytogenes fMIVTLF^neg strain. (A) The MIVTLF sequence in the attM region of L. monocytogenes 10403s was mutated to MIVIL to generate an L. monocytogenes strain lacking the fMIVTLF sequence (L. monocytogenes fMIVTLF^neg). (B) L. monocytogenes (L.m.) fMIVTLF^neg (open circles) grows with kinetics similar to that of L. monocytogenes 10403s (black squares). Cultures were inoculated with 1 ml of cultures grown overnight in 1,000 ml brain heart infusion broth. Cultures were grown at 37°C, and the bacterial concentration was determined at the indicated time points. (C) Bacterial numbers in spleens and livers of C57BL/6 mice 72 h after primary infection (infected with 5,000 bacteria) with L. monocytogenes fMIVTLF^neg or L. monocytogenes 10403s. The values are shown as means ± standard errors (error bars) of three mice per group. (D) Priming of H2-M3- but not H2-K^d-restricted CD8⁺ T cells in the absence of the cognate peptide antigen. Flow cytometric histograms are gated on donor CD8⁺ Thy1.1⁺ T cells and are representative of three mice per group.