Demonstration of viral antigen in cryostat sections by a new immunoperoxidase procedure eliminating endogenous peroxidase activity.

Abstract

Demonstration of viral antigens in infected cell cultures or clinical specimens by means of the immunoperoxidase technique is well established and yields results in accordance with the immunofluorescence technique ( 15). However, the presence of endogenous peroxidase activity may make the interpretation of stained preparations difficult (2) and, therefore, several methods have been developed to remove endogenous peroxidase activity (10-14). Unfortunately, viral antigens may also be removed by these techniques and as Gardner et al. (2) have recently stated much research work must be devoted to this problem before the immunoperoxidase method can be used to detect viruses in clinical material. In the course of experiments undertaken to establish a rapid diagnostic method for Newcastle disease virus (NDV) infections by means of the immunoperoxidase technique numerous procedures for removal of endogenous peroxidase activity ( 10-14) were tested. Treatment with methanol followed by highly diluted hydrogen peroxide was found to be the most suitable. The endogenous enzymatic activity was eliminated completely and no partial inhibition was observed as is the case in other methods. However, the leading envelope antigens