Experimental mumps virus-induced labyrinthitis. Immunohistochemical and ultrastructural studies.

Guinea pigs were inoculated with mumps virus (Torii strain) by the intralabyrinthine or intravascular route and their cochleas were examined by immunofluorescence and electron microscopy. In these animals, viral antigen was detected in the cochleas, most often in the stria vascularis. However, viral infection was produced only in those with intralabyrinthine inoculation. The cochlear lesion commonly observed in this study was severe degeneration of the organ of Corti, which was usually found in the basal turn. Morphological evidence of viral infection, as depicted by intracellular strands of nucleocapsids and budding of the virus at the endolymphatic surface, was prominent in both the stria vascularis and Reissner's membrane. The cochlear location of mumps infection correlated closely with that of the viral antigen formerly reported in newborn hamsters.