Enhanced luminescence intensity in immunofluorescent preparations following trypsin treatment

: Comparative investigations were carried out on the immunofluorescent preparations of cell cultures infected with bovine viruses--rota-, corona-, respiratory-syncytial, parainfluenza-3, adeno-1, and herpes-1--to test various fixatives and the effect of trypsin in raising the sensitivity of the immunofluorescence method. The effect of trypsin was manifested in fixation with formalin, ethanol, methanol, and acetone treated immunofluorescent preparations of cell cultures infected with rota- and adeno-viruses as well as in fixation with acetone of cultures infected with respiratory syncytial virus, parainfluenza-3 virus, and corona virus. Formalin, ethanol, and partly methanol were shown to be unsuitable for the purpose of fixation of cell culture preparations infected with viruses that contained a lipoprotein envelope. It was found that the treatment of immunofluorescent preparations with trypsin following fixation and prior to their treatment with conjugated antisera enhanced considerably the number of fluorescent cells and the intensity of fluorescence itself provided 0.1 per cent trypsin was used for 5 to 10 min at 37 degrees C--for cell culture preparations, and 0.1 per cent trypsin was used for 20 to 30 min at 37 degrees C--for paraffin sections of acetone-fixed tissues.