Gene delivery of antioxidant enzymes reduces the number of caspases-positive cells after gp120 injection. Four weeks after injection of SV(SOD1), SV(GPx1) or SV(BUGT) into the CP, we injected an oxidant neurotoxic challenge intra-CP, 500 ng ml−1 gp120. Apoptotic and caspases-positive cells were enumerated by TUNEL and immunocytochemistry one day later. A. The number of TUNEL-positive cells in the CP after gp120 challenge was reduced by prior injection of SV(SOD1) and SV(GPx1) into the same structure by approximately 81% [SV(GPx1)] to 85% [(SVSOD1)], P < 0.01 for both, compared to the control vector SV(BUGT). B. The numbers of caspases-positive cells were reduced between 82 to 85% for SV(SOD1) and between 75 to 83% for SV(GPx1), P < 0.01 for both compared to SV(BUGT).