[Detection of latent herpes simplex virus in human vestibular ganglia]

Viral infections are considered to be one of the possible etiologies of vestibular neuronitis. Herpes simplex virus type 1 (HSV-1) is a likely candidate agent as this virus has a strong neurotropism, and can establish latent infections in the nervous system. However the existence of infections in the vestibular ganglia has not been established. In this study, 31 vestibular ganglia from autopsied adults were investigated. Polymerase chain reaction (PCR) was used to detect HSV-1 viral genomes, and reverse transcription-PCR (RT-PCR) and in situ hybridization (ISH) methods were employed to demonstrate latency associated transcripts (LAT) of HSV-1, which has been known to be latency specific. HSV-1 DNA was detected in 6 of 10 (60%) vestibular ganglia using the PCR method, and HSV-1 LAT was detected in 5 of 8 (63%) vestibular ganglia using the RT-PCR method. However, ISH showed that only 1 of 13 (7.7%) vestibular ganglia was HSV-1 LAT positive. In total only 1 of 3,830 (0.03%) neurons from 13 vestibular ganglia was found to be positive. The results indicate with certainty that HSV-1 does produce latent infections in human vestibular ganglia, and that the percentage of HSV-1 infected neurons is less than that of trigeminal ganglia. The results of this study also suggest that the rare presence of HSV-1 LAT in the ganglia may possibly correspond to the less frequent occurrence of vestibular neuronitis resulting from reactivation of HSV-1.