ena-STUDY-UNIVERSITY COLLEGE LONDON-27-10-2017-16:21:05:293-593
A unique spliced varicella-zoster virus latency transcript represses expression of the viral transactivator gene 61
During primary infection, neurotropic alphaherpesviruses (aHVs) gain access to neurons in sensory and cranial ganglia establishing lifelong latent infection from which they can later reactivate to cause debilitating disease. For most aHVs, including the best-studied herpes simplex type 1 ( HSV-1), viral latency is characterized by expression of a single or restricted set of transcripts that map antisense to the open reading frame (ORF) homologous to the major HSV immediate early viral transactivator, ICP0. These latency transcripts, either directly or through encoded miRNAs or proteins, repress expression of the ICP0 orthologues. The exception is varicella-zoster virus (VZV), an aHV which infects over 90% of adults and for which neither a canonical latency transcript1, nor a putative mechanism for repressing lytic transcription during latency have been identified. Here, we describe the discovery and functional characterization of a VZV latency transcript (VLT), that maps antisense to VZV ORF 61 (the VZV ICP0 homologue9,10), and which is consistently expressed in neurons of latently infected human trigeminal ganglia (TG). VLT encodes a protein with late kinetics during lytic VZV infection in vitro and in zoster skin lesions. Whereas multiple alternatively spliced VLT isoforms are expressed during lytic VZV infection, a single unique VLT isoform that specifically suppresses ORF61 gene expression predominates in latently VZV-infected human TG. The discovery of VLT directly unifies the latent VZV transcription program with those of better-characterized aHVs, removing longstanding barriers to understanding VZV latency and paving the way for research into the development of vaccines that do not establish latency or reactivate, and drugs that eradicate latent VZV.
During primary infection, neurotropic alphaherpesviruses (aHVs) gain access to neurons in sensory and cranial ganglia establishing lifelong latent infection from which they can later reactivate to cause debilitating disease. For most aHVs, including the best-studied herpes simplex type 1 ( HSV-1), viral latency is characterized by expression of a single or restricted set of transcripts that map antisense to the open reading frame (ORF) homologous to the major HSV immediate early viral transactivator, ICP0. These latency transcripts, either directly or through encoded miRNAs or proteins, repress expression of the ICP0 orthologues. The exception is varicella-zoster virus (VZV), an aHV which infects over 90% of adults and for which neither a canonical latency transcript1, nor a putative mechanism for repressing lytic transcription during latency have been identified. Here, we describe the discovery and functional characterization of a VZV latency transcript (VLT), that maps antisense to VZV ORF 61 (the VZV ICP0 homologue9,10), and which is consistently expressed in neurons of latently infected human trigeminal ganglia (TG). VLT encodes a protein with late kinetics during lytic VZV infection in vitro and in zoster skin lesions. Whereas multiple alternatively spliced VLT isoforms are expressed during lytic VZV infection, a single unique VLT isoform that specifically suppresses ORF61 gene expression predominates in latently VZV-infected human TG. The discovery of VLT directly unifies the latent VZV transcription program with those of better-characterized aHVs, removing longstanding barriers to understanding VZV latency and paving the way for research into the development of vaccines that do not establish latency or reactivate, and drugs that eradicate latent VZV.