Isolation of the enhanced neurovirulent HSV-1 strains from Korean patients

Herpes simplex virus type 1 (HSV-1) is a neurotropic DNA virus which has latency in human. In this study, we isolated various HSV-1 strains, named KHS, from the skin lesions of Korean patients and characterized the specific features of each strain. We found that KHS strains produced small, cell associated and nonsyncycial plaques in Vero cells. We classified KHS strains into two substrains, KHS 1 which had highly condensed plaques and KHS 2 which had less condensed plaques. Since gD protein of HSV-1 plays important roles in viral plaque formation, we determined the nucleotide sequences of gD genes of KHS strains. According to deduced amino acid sequences of gD protein in KHS strains compared with prototype strains KOS and F, we found that gD of KHS strains have more putative O-glycosidic sites, serine in KHS 1 and threonine in KHS 2, respectively. To find out the establishment of viral latency, we infected each virus strain into eyes of mice and carried out trigerminal ganglia explanting experiment. We found that both KHS strains established latent infections stably just as did the prototype KOS and F strains. The eye swab experiments were carried out to check the viral replication in vivo. KHS 1 exhibited a longer shedding time in eyes of mice. We also found that KHS 1 has a higher neurotropic affinity by determining the time it took for the virus to reach the trigerminal ganglia from the eyes. Currently, we are studying the possible mechanism of high neuroinvasiveness of KHS 1 strain.