Search Results (8)

The order Herpesvirales contains three families, Orthoherpesviridae, Alloherpesviridae, and Malacoherpesviridae. The time since divergence of families from the common ancestor makes protein primary sequence comparison an insensitive tool for identifying common genes. Comparison of three-dimensional protein structures can reveal similarities that are not evident in primary sequences. Salmonid herpesvirus 1 (SalHV-1) is an alloherpesvirus. Complete sequencing of SalHV-1 VR-868 strain Winthrop by a combination of short- and long-read methods revealed 120 putative open reading frames (ORFs). BLAST search for similar protein sequences discovered five ORFs that encoded proteins with homologs in the orthoherpesviruses, including the major capsid protein, capsid triplex subunit 2, the catalytic subunit of the DNA polymerase, the helicase subunit of the helicase/primase complex, and the terminase ATPase subunit. An annotation of the ORFs of SalHV-1 was performed in which ORFs of SalHV-1 were modeled using AlphaFold3, and the models were used as prompts for structural similarity search using DALI and FoldSeek. Completion of this search strategy for the entire genome expanded the set of genes shared among the Herpesvirales to include additional proteins related to DNA replication and genome integrity, capsid assembly and genome packaging, and capsid nuclear egress. No homologs for any tegument proteins or proteins of the conserved entry apparatus of the Herpesviridae (gB, gH or gL) were discovered. Full article

The alloherpesvirus esocid herpesvirus 1 (EsHV-1) causes epidermal hyperplasia on the skin and fins of northern pike (Esox lucius). For the first time, we present a near-complete genome sequence of EsHV-1, directly obtained from a pike skin sample. The 223,553 bp sequence of the genome has a GC-content of 56.47% and is organised into a long, unique segment (148,159 bp) and a short, unique segment (45,925 bp). The short segment is flanked by inverted repeat sequences (IRSs) of 14,733/6 bp, with the IRS length difference attributed to a codon deletion. The genome is predicted to contain 144 open reading frames, including eight duplicated within the IRSs. The leftmost third of the genome contains genes of unknown function, but many of which exhibit extensive inter-gene homology, suggesting gene duplication. Six paralogous groups were identified, each containing two to thirteen gene members. Homologues of all twelve alloherpesvirus core genes are present. The ATPase subunit of the terminase and the DNA polymerase is composed of three and two exons, respectively. However, an alternate splicing pattern is found, for which, speculatively, a role is suggested in the terminase assembly at the capsid portal. Full article

DNA sequence from a new alloherpesvirus named acipenserid herpesvirus 3 (AciHV-3) was found in sturgeon species that are vulnerable to decline globally. A study was undertaken to develop a better understanding of the virus genome and to develop diagnostic tools to support an epidemiological investigation. A 184,426 bp genome was assembled from PacBio HiFi sequences generated with DNA from a Lake Sturgeon Acipenser fulvescens gonad cell line. The AciHV-3 genome was contiguous with host chromosomal DNA and was structured with telomere-like terminal direct repeat regions, five internal direct repeat regions and a U region that included intact open reading frames encoding alloherpesvirus core proteins. Diagnostic testing conducted with a newly developed and analytically validated qPCR assay established the ubiquitous presence and high titer of AciHV-3 DNA in somatic and germline tissues from wild Lake Sturgeon in the Hudson Bay drainage basin. Phylogenetic reconstructions confirm that the monophyletic AciHV-3 lineage shares a common ancestor with AciHV-1 and that AciHV-3 taxa cluster according to their sturgeon host. The same genotype of AciHV-3 is found in disjunctive Lake Sturgeon populations within and among drainage basins. The results support the hypotheses that AciHV-3 has established latency through germline chromosomal integration, is vertically transmitted via a Mendelian pattern of inheritance, is evolving in a manner consistent with a replication competent virus and has co-evolved with its host reaching genetic fixation in Lake Sturgeon populations in central Canada. Full article

Background/Objectives: Anguillid herpesvirus 1 (AngHV-1) (recently renamed Cyvirus anguillidallo 1) is the etiologic agent of a lethal disease that affects several eel species. It is thought to be one of the main infectious agents causing a population decline in wild eels and economic loss within the eel aquaculture sector. To date, no vaccines are available against AngHV-1. Recently, we developed a safe and efficacious live attenuated recombinant vaccine against Cyprinid herpesvirus 3 (CyHV-3). This CyHV-3 recombinant vaccine encodes a deletion of ORF57. Orthologues of CyHV-3 ORF57 exist in Cyprinid herpesvirus 2 (CyHV-2, ORF57) and AngHV-1 (ORF35). Methods: In the present study, using recombinant strains and bioluminescent in vivo imaging, we investigated the effect of AngHV-1 ORF35 deletion on virus replication in vitro, virulence in vivo, and the potential of an AngHV-1 ORF35-deleted recombinant as a vaccine candidate for the mass vaccination of eels by immersion. With this goal in mind, we produced ORF35-deleted recombinants using two parental strains: a UK strain and a recombinant derived from the former strain by insertion of a Luciferase–GFP reporter cassette into a non-coding intergenic region. Results: Analyses of ORF35-deleted recombinants led to the following observations: (i) AngHV-1 ORF35 is not essential for viral growth in cell culture, and its deletion does not affect the production of extracellular virions despite reducing the size of viral plaque. (ii) In contrast to what has been observed for CyHV-3 ORF57 and CyHV-2 ORF57, in vivo bioluminescent analyses revealed that AngHV-1 ORF35 is an essential virulence factor and that its deletion led to abortive infection in vivo. (iii) Inoculation of the AngHV-1 ORF35-deleted recombinant by immersion induced a protective immune response against a wild-type challenge. This protection was shown to be dose-dependent and to rely on the infectivity of AngHV-1 ORF35-deleted virions. Conclusions: This study suggests that the AngHV-1 ORF35 protein has singular properties compared to its orthologues encoded by CyHV-2 and CyHV-3. It also supports the potential of AngHV-1 ORF35-deleted recombinants for the mass vaccination of eels by immersion. Full article

Infectious diseases are a leading cause of losses in the aquaculture industry and conservation programs globally. Simultaneously, infectious diseases pose a substantial risk to fish being hatchery-reared and released into natural habitats for conservation purposes, including the Great Lakes lake sturgeon (Acipenser fulvescens, i.e., GL-LST). Recently, an alloherpesvirus (lake sturgeon herpesvirus 2, i.e., LSHV-2) capable of inducing disease and/or mortality in adult and juvenile GL-LSTs was detected in two adult GL-LST populations. To begin developing disease prevention and/or control methods, in vitro experiments were designed to determine the susceptibility of LSHV-2 to disinfectants commonly used in hatchery and aquaculture facilities (Virkon^®-Aquatic: potassium peroxymonosulfate; Ovadine^®: polyvinylpyrrolidone iodine complex; and Perox-Aid^®: hydrogen peroxide). Cultured LSHV-2 was exposed to each disinfectant at two concentrations (Virkon^®-Aquatic: 0.5% and 1%; Ovadine^®: 50 and 100 ppm; and Perox-Aid^®: 500 and 1000 ppm) in duplicate for durations of 1, 10, and 30 min. Following exposure, the disinfectant was neutralized, and after a 14-day incubation period on a white sturgeon × lake sturgeon hybrid cell line (WSxLS), percent reduction was calculated by comparing the 50% tissue culture infectious doses (TCID₅₀/mL) of the virus with and without disinfectant exposure. When exposed to Perox-Aid^®, LSHV-2 percent reduction ranged from 58.7% to 99.5%. When exposed to Ovadine^®, the percent reduction ranged from 99.4% to 100%. Lastly, the percent reduction when exposed to Virkon^®-Aquatic was 100% for both concentrations and all timepoints. The results herein provide evidence that both Virkon^®-Aquatic and Ovadine^® are virucidal to LSHV-2 and may represent a means to reduce virus transmission risk under field settings. Full article

Herpesvirus infections of sturgeon pose a potential threat to sturgeon culture efforts worldwide. A new epitheliotropic herpesvirus named Acipenser herpesvirus 3 (AciHV-3) was detected in hatchery-reared Lake Sturgeon Acipenser fulvescens displaying skin lesions in central Canada. The growths were discovered in the fall, reached average prevalence levels of 0.2–40% and eventually regressed. No unusual mortality was observed. The cellular changes within the lesions included epithelial hyperplasia and were reminiscent of other herpesvirus infections. The virus was not evident in lesions examined by electron microscopy. Skin tissue homogenates from symptomatic sturgeon produced atypical cytopathic effects on a primary Lake Sturgeon cell line, and next-generation sequence analysis of the DNA samples revealed the presence of an alloherpesvirus. A new genotyping PCR assay targeting the major capsid protein sequence detected AciHV-3 in symptomatic Lake Sturgeon as well as other apparently healthy sturgeon species. Bayesian inference of phylogeny reconstructed with a concatenation of five alloherpesvirus core proteins revealed a new Alloherpesviridae lineage isomorphic with a new genus. The presence of AciHV-3 homologs in cell lines and sturgeon sequence datasets, low sequence divergence among these homologs and branching patterns within the genotyping phylogeny provide preliminary evidence of an endogenous virus lifestyle established in an ancestral sturgeon. Full article

The zebrafish (Danio rerio) represents an increasingly important model organism in virology. We evaluated its utility in the study of economically important viruses from the genus Cyprinivirus (anguillid herpesvirus 1, cyprinid herpesvirus 2 and cyprinid herpesvirus 3 (CyHV-3)). This revealed that zebrafish larvae were not susceptible to these viruses after immersion in contaminated water, but that infections could be established using artificial infection models in vitro (zebrafish cell lines) and in vivo (microinjection of larvae). However, infections were transient, with rapid viral clearance associated with apoptosis-like death of infected cells. Transcriptomic analysis of CyHV-3-infected larvae revealed upregulation of interferon-stimulated genes, in particular those encoding nucleic acid sensors, mediators of programmed cell death and related genes. It was notable that uncharacterized non-coding RNA genes and retrotransposons were also among those most upregulated. CRISPR/Cas9 knockout of the zebrafish gene encoding protein kinase R (PKR) and a related gene encoding a protein kinase containing Z-DNA binding domains (PKZ) had no impact on CyHV-3 clearance in larvae. Our study strongly supports the importance of innate immunity-virus interactions in the adaptation of cypriniviruses to their natural hosts. It also highlights the potential of the CyHV-3-zebrafish model, versus the CyHV-3-carp model, for study of these interactions. Full article

Herpesviruses are host specific pathogens that are widespread among vertebrates. Genome sequence data demonstrate that most herpesviruses of fish and amphibians are grouped together (family Alloherpesviridae) and are distantly related to herpesviruses of reptiles, birds and mammals (family Herpesviridae). Yet, many of the biological processes of members of the order Herpesvirales are similar. Among the conserved characteristics are the virion structure, replication process, the ability to establish long term latency and the manipulation of the host immune response. Many of the similar processes may be due to convergent evolution. This overview of identified herpesviruses of fish discusses the diseases that alloherpesviruses cause, the biology of these viruses and the host-pathogen interactions. Much of our knowledge on the biology of Alloherpesvirdae is derived from research with two species: Ictalurid herpesvirus 1 (channel catfish virus) and Cyprinid herpesvirus 3 (koi herpesvirus). Full article