(A) CTL activity in mice splenocytes after intratumoral inoculation with HSV amplicon vector. EL4 cells were inoculated SC in mice and tumors allowed to grow to 5 to 6 mm in diameter over 6 to 7 days. On days 7 and 14, HSV amplicon virus was injected as indicated directly into the tumors. Spleens were harvested 1 month later and splenocytes were cultured in vitro in the presence of irradiated EL4 cells. After 6 days in culture, CTL activity was measured by release of⁵¹Cr from labeled EL4 cells. CTL activity of splenocytes harvested from individual mice intratumorally injected with HSVB7.1 (▴, ▵, ▾) HSVrantes (▪, ⊞, □) HSVB7.1 and HSVrantes (•, ⊕, ○), or HSVlac (*, ×) are shown. Data are expressed as the percentage of specific lysis versus E:T ratio. (B) Antibody blocking of the CTL activity with anti-CD4, anti-CD8, anti–Thy-1, or anti–T-cell cocktail (anti-CD4, anti-CD8, and anti–Thy-1) antibodies. Splenocytes with known CTL activity (harvested from HSV-B7.1+ HSVrantes inoculated mouse no. 26 [A]) were used in an antibody blocking assay. No antibody (▪), anti-CD4 (GK1.5, □), anti-CD8 (3.155, ○), or anti–T-cell antibody cocktail (anti-CD4, anti-CD8, and anti–Thy-1, ▵) were added to the CTL assay at the indicated effector:target ratios as described in Materials and Methods. In a separate experiment, Yac-1 cells were used as target cells (*) for measuring NK activity. Data are represented as the percentage of specific lysis versus E:T ratio.