ICP10 PK has antiapoptotic activity and inhibits caspase-3 activation in virus-infected hippocampal cultures. (A) Primary hippocampal cultures were infected (24 h) with HSV-2, HSV-2(R), ICP10ΔPK, or ICP10ΔRR (10 PFU/cell) and analyzed by TUNEL. The results are expressed as the mean percent apoptotic cells ± SEM estimated by counting cells in five randomly chosen microscopic fields and subtracting the percent positive cells in mock-infected cultures, as described in Materials and Methods. *, P < 0.01 versus HSV-2 and HSV-2(R) or ICP10ΔRR; +, P = 0.046 versus HSV-2 or HSV-2(R) by ANOVA. (B) Hoechst staining of representative nuclei from TUNEL-positive ICP10ΔPK-infected cells. (C) Hoechst staining of representative nuclei from TUNEL-negative HSV-2-infected cells. (D) Primary hippocampal cultures infected with HSV-2, HSV-2(R), ICP10ΔPK, or ICP10ΔRR as in A were stained with antibody to the activated caspase-3. The results are expressed as the mean percent staining cells ± SEM estimated by counting cells in five randomly chosen microscopic fields as in A. *, P < 0.05 versus HSV-2, HSV-2(R), or ICP10ΔRR by ANOVA.