Apoptosis of cord blood T lymphocytes by herpes simplex virus type 1

We investigated apoptosis induced by herpes simplex virus type 1 (HSV-1) in cord blood T lymphocytes by using agarose gel electrophoresis, DNA content analysis and the terminal deoxytransferase (TdT)-mediated dUTP nick end-labelling (TUNEL) method. DNA fragmentation and the hypodiploid fraction in the cell cycle were both increased in HSV-1-infected CD4 and CD8 lymphocytes stimulated with phytohaemagglutinin (PHA) compared to mock-infected lymphocytes. The percentage of cells in the S phase was decreased in HSV-1-infected CD4 and CD8 lymphocytes. HSV-1 antigen, glycoprotein D (gD) and regulatory protein ICP27 were detected in 8-18% of the hypodiploid fraction of PHA-stimulated, HSV-1-infected lymphocytes. Apoptosis was induced not only in HSV-1 antigen-expressing cells but also in cells not expressing detectable viral proteins. Addition of anti-Fas antibody, anti-Fas-ligand antibody or a mixture of both had no effect on HSV-1-induced apoptosis, indicating that the Fas-Fas-ligand pathway did not contribute to HSV-1-induced apoptosis.