Long-term protection against L. monocytogenes challenge in RAE-1γMCMVList–immunized mice. BALB/c mice were f.p. immunized with 105 pfu per mouse of indicated viruses. (A) Three weeks postimmunization, mice were challenged with 104 cfu per mouse of L. monocytogenes. One day before the challenge, mice were depleted of CD8 T cells or left undepleted. Four days later, the bacterial loads were determined (mean ± SEM, n = 4–5). (B) Challenge with 2 × 104 cfu per mouse of L. monocytogenes was performed 60 d postimmunization. Survival and body weight loss (mean ± SEM) on day 3 (n = 9–12) is shown. (C) Bacterial load of survived mice on day 4 postchallenge in spleen is shown (individual animals and median values, n = 9; † indicates the death of a mouse). (D) Challenge with 4 × 104 cfu per mouse of L. monocytogenes was performed 60 d postimmunization, and the survival rate was followed (n = 9). (E) Mice were injected with an equal ratio of unstimulated and LLO-peptide–stimulated CSFE-stained splenocytes 2 and 11 mo postimmunization. Percentage of listeriolysin peptide-specific killing is shown (mean ± SEM, n = 3–4).