During Herpes Simplex Virus Type 1 Infection of Rabbits, the Ability To Express the Latency-Associated Transcript Increases Latent-Phase Transcription of Lytic Genes

Department of Molecular Genetics and Microbiology, Box 100266, University of Florida College of Medicine, Gainesville, FL 32610-0266, USA.
Journal of Virology (Impact Factor: 4.44). 07/2008; 82(12):6056-60. DOI: 10.1128/JVI.02661-07
Source: PubMed


Trigeminal ganglia (TG) from rabbits latently infected with either wild-type herpes simplex virus type 1 (HSV-1) or the latency-associated
transcript (LAT) promoter deletion mutant 17ΔPst were assessed for their viral chromatin profile and transcript abundance.
The wild-type 17syn+ genomes were more enriched in the transcriptionally permissive mark dimethyl H3 K4 than were the 17ΔPst genomes at the 5′
exon and ICP0 and ICP27 promoters. Reverse transcription-PCR analysis revealed significantly more ICP4, tk, and glycoprotein C lytic transcripts in 17syn+ than in 17ΔPst. These results suggest that, for efficient reactivation from latency in rabbits, the LAT is important for
increased transcription of lytic genes during latency.

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Available from: Dacia L Kwiatkowski, Apr 21, 2014
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    • "Since 1978 [8], we have utilized the rabbit eye model for HSV-1 studies on antiherpetic chemotherapy [8-13], HSV-1 latency [14,15], and spontaneous and induced viral reactivations and recurrent ocular herpetic disease [16-35]. We have also investigated up-regulation and down-regulation of host gene expression [36,37] and alterations in reactivation phenotypes in HSV-1 genomic structure by histone modifications as a result of mutations in the viral genome [38-41] that take place following induction stimuli that could induce reactivation [42-44]. "
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    ABSTRACT: Background Rabbits latent with HSV-1 strain McKrae spontaneously shed infectious virus and viral DNA into their tears and develop recurrent herpetic-specific corneal lesions. The rabbit eye model has been used for many years to assess acute ocular infections and pathogenesis, antiviral efficacy, as well as latency, reactivation, and recurrent eye diseases. This study used real-time PCR to quantify HSV-1 DNA in the saliva and tears of rabbits latent with HSV-1 McKrae. Methods New Zealand white rabbits used were latent with HSV-1 strain McKrae and had no ocular or oral pathology. Scarified corneas were topically inoculated with HSV-1. Eye swabs and saliva were taken from post inoculation (PI) days 28 through 49 (22 consecutive days). Saliva samples were taken four times each day from each rabbit and the DNA extracted was pooled for each rabbit for each day; one swab was taken daily from each eye and DNA extracted. Real-time PCR was done on the purified DNA samples for quantification of HSV-1 DNA copy numbers. Data are presented as copy numbers for each individual sample, plus all the copy numbers designated as positive, for comparison between left eye (OS), right eye (OD), and saliva. Results The saliva and tears were taken from 9 rabbits and from 18 eyes and all tested positive at least once. Saliva was positive for HSV-1 DNA at 43.4% (86/198) and tears were positive at 28.0% (111/396). The saliva positives had 48 episodes and the tears had 75 episodes. The mean copy numbers ± the SEM for HSV-1 DNA in saliva were 3773 ± 2019 and 2294 ± 869 for tears (no statistical difference). Conclusion Rabbits latent with strain McKrae shed HSV-1 DNA into their saliva and tears. HSV-1 DNA shedding into the saliva was similar to humans. This is the first evidence that documents HSV-1 DNA in the saliva of latent rabbits.
    Full-text · Article · Sep 2012 · Virology Journal
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    • "Like other herpesviruses, incoming cytomegalovirus genomes rapidly associate with cellular histone proteins upon entering the nucleus and numerous studies have confirmed the role chromatin structure plays in both the lytic and latent phases of cytomegalovirus infection [14], [15], [16], [17], [18], [19], [20]. Nucleosomes associate with the HCMV genome within 30 minutes after infection and are subject to various PTMs, generating an irregular chromatin structure on the genome [21]. "
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    ABSTRACT: Regulation of viral transcription by chromatin structure has emerged as a fundamental determinant in the establishment of lytic and latent herpesvirus infections. The Polycomb group (PcG) of epigenetic repressors promotes heterochromatin formation by trimethylating histone H3 on lysine-27 (H3K27me3) and regulates development, stem cell renewal and differentiation and the cell cycle. These cellular processes are tightly coupled to the molecular switch between lytic and latent herpesvirus infections. Using chromatin immunoprecipitation analysis, we observed enrichment of H3K27me3 at the major immediate-early (MIE) locus of murine cytomegalovirus (MCMV) very early following infection of permissive fibroblasts. As lytic replication progressed, we observed a loss of H3K27me3 enrichment concomitant with the appearance of H3K4me3. However, late during infection, as viral replication centers are established, we observed a significant increase in PcG protein association with chromatin. Additionally, in co-immunofluorescence assays using confocal microscopy, we detected strong enrichments for PcG protein within the viral replication compartment, suggesting an association between viral DNA synthesis machinery and PcG proteins. Together, our results suggest a novel, dynamic interaction between PcG epigenetic repressors and MCMV genomes.
    Full-text · Article · Jan 2012 · PLoS ONE
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    • "In contrast to the situation in the mouse, studies in rabbits have led to an opposing view on the role of LATs in the regulation of lytic cycle promoter activity. Thus, in rabbits, LATs function to keep the virus genome in a more transcriptionally active state (Giordani et al., 2008). Furthermore, a recent report using a mouse model has indicated that LATs may function to suppress the accumulation of facultative heterochromatin on the latent virus genome (Kwiatkowski et al., 2009). "
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    ABSTRACT: Herpes simplex virus type 1 is a neurotropic herpesvirus that establishes latency within sensory neurones. Following primary infection, the virus replicates productively within mucosal epithelial cells and enters sensory neurones via nerve termini. The virus is then transported to neuronal cell bodies where latency can be established. Periodically, the virus can reactivate to resume its normal lytic cycle gene expression programme and result in the generation of new virus progeny that are transported axonally back to the periphery. The ability to establish lifelong latency within the host and to periodically reactivate to facilitate dissemination is central to the survival strategy of this virus. Although incompletely understood, this review will focus on the mechanisms involved in the regulation of latency that centre on the functions of the virus-encoded latency-associated transcripts (LATs), epigenetic regulation of the latent virus genome and the molecular events that precipitate reactivation. This review considers current knowledge and hypotheses relating to the mechanisms involved in the establishment, maintenance and reactivation herpes simplex virus latency.
    Full-text · Article · Dec 2011 · FEMS microbiology reviews
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