Demonstration of herpes simplex 1 virus antigen mouse brain after fixation

The effects of several fixatives and fixation periods on recovery of viral antigen by indirect immunofluorescence (IF) and indirect immunoperoxidase (IP) were examined in mouse brains infected with type-1 herpes simplex virus. In 10% formalin, the sensitivity of antigen detection by IF decreased after one month fixation and viral antigen was barely detectable after fixation for three months. But in 10% buffered formalin antigenicity was not lost after six months. Similar effects were obtained by IP; however, specimens fixed in 10% formalin for three and six months showed positive reactions. Viral antigen was detectable without enzyme digestion in paraffin materials fixed in Bouin's, Carnoy's and Dubosq-Brazil solutions, but when treated with proteolytic enzyme for three hours, antigen could not be detected by either IF or IP. Ten per cent buffered formalin, Bouin's or Dubosq-Brazil solutions are recommended as fixatives for retrospective immunohistochemical and histopathological studies of viral infection in autopsy and biopsy materials.