Figure 3.

Immunization of mice with PPV:VLP-(LCMV) induces a long-lasting memory CD8⁺ CTL activity. (A) Mice were immunized i.p. on days 0 and 21 with 10 μg of PPV:VLP-(LCMV) in PBS (□) or with alum (▪). Spleens were removed 7 days later. (B) Mice were treated on days −1, 0, +1, and 9 with anti-CD4 (•) or anti-CD8 (▵) mAbs or with PBS (□) and were injected on day 0 with 10 μg PPV:VLP-(LCMV). Control mice received 10 μg of control PPV:VLP (⧫). Spleens were removed on day 14. (C) Mice were immunized i.p. on days 0 and 21 with 10 μg of either PPV:VLP (hatched bars) or PPV:VLP-(LCMV) (solid bars). Spleens were removed at various times after the second PPV:VLP injection as indicated. CTL activity was determined after in vitro stimulation of splenocytes as described in Fig. 2. Lysis of uncoated target cells was less than 10% and is not shown. Data represent the mean of percent specific lysis from duplicates (SD < 5%). Data in C were obtained at a 100:1 effector/target (E/T) ratio.