Aberrant Virion Assembly and Limited Glycoprotein C Production in Varicella-Zoster Virus-Infected Neurons

Abstract

Highly pure (>95%) terminally differentiated neurons derived from pluripotent stem cells appear healthy at 2 weeks after infection with varicella-zoster virus (VZV), and the cell culture medium contains no infectious virus. Analysis of the healthy-appearing neurons revealed VZV DNA, transcripts, and proteins corresponding to the VZV immediate early, early, and late kinetic phases of replication. Herein, we further characterized virus in these neuronal cells, focusing on (i) transcription and expression of late VZV glycoprotein C (gC) open reading frame 14 (ORF14) and (ii) ultrastructural features of virus particles in neurons. The analysis showed that gC was not expressed in most infected neurons and gC expression was markedly reduced in a minority of VZV-infected neurons. In contrast, expression of the early-late VZV gE glycoprotein (ORF68) was abundant. Transcript analysis also showed decreased gC transcription compared with gE. Examination of viral structure by high-resolution transmission electron microscopy revealed fewer viral particles than typically observed in cells productively infected with VZV. Furthermore, viral particles were more aberrant, in that most capsids in the nuclei lacked a dense core and most enveloped particles in the cytoplasm were light particles (envelopes without capsids). Together, these results suggest a considerable deficiency in late-phase replication and viral assembly during VZV infection of neurons in culture.