Molecular biological study of the latent viral infection of the inner ear

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Viral infection, especially by reactivation of latent herpes virus has been considered to be a possible explanation for the pathogenesis of idiopathic peripheral facial nerve palsy (Bell's palsy),sudden sensorineural hearing loss,vestibular neuronitis and Ramsey-Hunt syndrome. As of yet,however, latent HSV-1 and VZV in the sensory neurons of the geniculate, spiral or vestibular ganglia has been sitll unknown.In this project,we examined the HSV type 1(HSV-1) and varicella-zoster virus DNA in human geniculate, spiral and vestibular ganglia of autopsy patients by using molecular bioological technique, polymerase chain reaction(PCR), in situ hybridization (ISH) and reverse transcrioption PCR(RT-PCR) methods.The summary of the results are as follows;1) We detected HSV-1 DNA in 15 of 17 geniculate ganglia, in 10 of 10 spiral ganglia and in 6 of 10 vestibular ganglia by PCR method.2) HSV-1 latency associated transcript (LAT) was detected in 11 of 15 geniculate ganglia, in none of 10 spiral and vestibular ganglia.by ISH method.3) By usingn more sensitive RT-PCR, we detected HSV-1 LAT in all of 8 geniculate ganglia examined,in 2 of 8 vestibular ganglia and none of 8 spiral ganglia.4) We also detected VZV DNA in 9 of 13 geniculate ganglia and 2 of 10 spiral and vestibular ganglia.by PCR method.These results suggest that latent HSV-1 and VZV in the human geniculate, spiral and vestibular ganglia may possible causes of idiopathic peripheral facial nerve palsy ( Bell's palsy ),sudden sensorineural hearing loss,vestibular neuronitis and Ramsey-Hunt syndrome. However, the absence of the HSV-1 LAT in spiral ganglia in particular indicates the incidence of HSV-1 reactivation of the spiral ganglia may be rare.