Figure 2. Induction of CD8⁺ CTL specific for HSP65 protein and M. tuberculosis by vaccination with HVJ-Envelope/HSP65 DNA + IL-12 DNA. Spleen cells from the naïve, BCG-, and HVJ-Envelope/HSP65 DNA + IL-12 DNA vaccinated mice were obtained eight weeks after the final vaccination. Cytotoxicity was assayed as release of radioactivity from ⁵¹Cr-labeled P815 target that had been transfected with HSP65 DNA using conventional ⁵¹Cr release assay as described in Materials and Methods.