Transfection experiments with heated herpes simplex virus and the unreliability of current inactivation controls

Significant infectivity was found in heated and apparently inactivated herpes simplex virus (HSV) types 1 and 2 when cell entry was promoted using the Ca-DMSO transfection technique. Infectivity was quantitated in RSB-1 (rabbit skin fibroblast) and BHK-21 cells, dose-response curves being found to depend upon both cell substrate and thermal side effects. Titres varied with the initial infectivity and cell origin of the virus, and were stable for 6 hours at 56 degrees C, and slightly lower and less stable at 70 degrees C. This report shows that current knowledge concerning the heat-sensitivity of viruses should be revised, and controls for effective inactivation complemented by tests capable of detecting any residual activity of the viral genome.