Experimental infection of HSV-I in vestibular gangila : detection of HSV-I DNA with PCR

It hase been suggested from clinical investigations that virus could be one of the causative agents of vestribular neuronitis. Among them herpes simplex virus (HSV) infection seems to be most popular because herpes virus preferentially infects the nerve system and can establish latent infection in the peripheral nerve ganglia. However, it is difficult to detect very small amount of virus genomes in ganglia in latent phase of HSV infection. In this study, KOS strain of HSV type I (HSV-I) was inoculated in the right middle ear cavity or intraperitoneal space of rats. Polymerase chain reaction (PCR) with thermostable DNA polymerase was developed to detect HSV-I DNA. Using this technique, we examined the vestibular ganglia, trigeminal ganglia, cerebrum, cerebellum and brainstem of latenly infected rats. On inoculation of the virus in the right middle ear cavity, 7 cases out of 10 rats died due to viral encephalitis within the 14th day after inoculation. In the other 3 rats with no symptom, specifically amplified HSV-I genomes were detected only from the right vestibular ganglia (67%),bilateral trigeminal ganglia (67% in the inoculated side, 33% in the opposite side) cerebellum and brainstem (100%). On the other hand, in incluation into intraperitoneal space, all rats presented no symptom, and HSV-I genomes were detected from bilateral vestibular ganglia (60%) and with no laterality. From trigeminal ganglia, HSV-I genome was detected in the cerebellum and brainstem. These data indicated the possibility that reactivation of HSV-I genomes and viral expression may lead to the disorder of vestibular system, which will be associated with various abnormalities of vestibular function, such as canal paralysis.