A GH19 lysozyme and peptidase from Myoviridae cyanophages lacking the typical holin-endolysin system exhibit lytic activity.

Most of the dsDNA cyanophages employ holin-endolysin lysis systems to damage the host cells. This study aimed to elucidate the lytic activity of ORF91 and ORF117 in the cyanophage MaMV-DH01, which lacked a conventional cholinesterase system. These two proteins contained Lyz-like superfamily domains and were annotated as a member of GH family 19 (named DHGH19) and peptidase (named DHpeptidase), respectively.

Eukaryotic translation elongation factor 1 alpha (eEF1A) inhibits rhabdovirus (SCRV) infection through two distinct mechanisms.

Although a virus can regulate many cellular responses to facilitate its replication by interacting with host proteins, the host can also restrict virus infection through these interactions. In the present study, we showed that the host eukaryotic translation elongation factor 1 alpha (eEF1A), an essential protein in the translation machinery, interacted with two proteins of a fish rhabdovirus, rhabdovirus (SCRV), and inhibited virus infection via two different mechanisms: (i) inhibiting the formation of crucial viral protein complexes required for virus transcription and replication and (ii) promoting the ubiquitin-proteasome degradation of viral protein. We also revealed the functional regions of eEF1A that are involved in the two processes.

Advances on genomes studies of large DNA viruses in aquaculture: A minireview.

Genomic studies of viral diseases in aquaculture have received more and more attention with the growth of the aquaculture industry, especially the emerging and re-emerging viruses whose genome could contain recombination, mutation, insertion, and so on, and may lead to more severe diseases and more widespread infections in aquaculture animals. The present review is focused on aquaculture viruses, which is belonged to two clades, Varidnaviria and Duplodnaviria, and one class Naldaviricetes, and respectively three families: Iridoviridae (ranaviruses), Alloherpesviridae (fish herpesviruses), and Nimaviridae (whispoviruses). The viruses possessed DNA genomes nearly or larger than 100 kbp with gene numbers more than 100 and were considered large DNA viruses.

Genome Characteristics of Two Ranavirus Isolates from Mandarin Fish and Largemouth Bass.

Ranaviruses are promiscuous pathogens that threaten lower vertebrates globally. In the present study, two ranaviruses (SCRaV and MSRaV) were isolated from two fishes of the order Perciformes: mandarin fish () and largemouth bass (). The two ranaviruses both induced cytopathic effects in cultured cells from fish and amphibians and have the typical morphologic characteristics of ranaviruses.

Biological and Genomic Characteristics of MaMV-DH01, a Novel Freshwater Cyanophage Strain.

The genomic traits of cyanophages and their potential for metabolic reprogramming of the host cell remain unknown due to the limited number of studies on cyanophage isolates. In the present study, a lytic cyanophage, MaMV-DH01, was isolated and identified. MaMV-DH01 has an icosahedral head approximately 100 nm in diameter and a tail 260 nm in length.

Rhabdovirus (SCRV)-Induced Key Pathways and Major Antiviral Genes in Fish Cells.

Fish rhabdoviruses, including rhabdovirus (SCRV), are epidemic pathogens that harm fish aquaculture. To clarify the interactions between SCRV and its host and explore antiviral targets, the present study performed transcriptome analysis in a cultured skin cell line (SCSC) after SCRV infection at 3, 12, 24, and 36 h post-infection (hpi). Comparison with control obtained 38, 353, 896, and 1452 differentially expressed genes (DEGs) in the detected time points, respectively.

Environmental Factors and Their Threshold Affecting the Survival of Five Aquatic Animal Viruses in Different Animal Cells.

Aquatic animal viruses infect and transmit in aquatic environments, causing serious harm to the aquaculture industry and a variety of wild aquatic animals. How are they affected by environmental factors and do they represent potential threat to mammalian heath or not? Here, the effects of environmental factors (ultraviolet radiation (UV), temperature, pH, and drying) and their threshold on five epidemic aquatic animal viruses infecting amphibians and bony fish, including virus (RGV), ranavirus (ADRV), Grass carp reovirus (GCRV), rhabdovirus (PORV), and rhabdovirus (SMRV), were measured and compared in a fish cell line. The examination of virus titers after different treatment in fish cells showed that the two iridoviruses, RGV and ADRV, had a higher tolerance to all of the environmental factors, such as they only had a decay rate of 22-36% when incubated at 37 °C for 7 days.

Development and characterization of a skin cell line from Chinese perch (Siniperca chuatsi) and its application in aquatic animal viruses.

Chinese perch (Siniperca chuatsi), an important fish for the aquaculture industry of China, is often affected by viral diseases. A stable and sensitive cell line can play an important role in virus identification and isolation, functional gene identification, virus pathogenic mechanism and antiviral immunity study. In the present study, a new cell line (S.

ADRV 12L: A Ranaviral Putative Rad2 Family Protein Involved in DNA Recombination and Repair.

The ranavirus (ADRV) is a member of the family and belongs to the nucleocytoplasmic large DNA viruses. Based on genomic analysis, an ADRV-encoding protein, ADRV , and its homologs from other iridoviruses were predicted as Rad2 family proteins based on the conserved amino acids, domains, and secondary structures. Expression analysis showed that the transcription of ADRV started at 4 h post infection, and its expression was not inhibited by a DNA-replication inhibitor.

Functional Analysis of the Endopeptidase and Holin From Cyanophage PaV-LD.

A cyanophage PaV-LD, previously isolated from harmful filamentous cyanobacterium , was sequenced, and co-expression of its two ORFs in tandem, ORF123 and ORF124, inhibited growth on the model cyanobacterium sp. PCC6803 cells. However, the mechanism of action of ORF123 and ORF124 alone remains to be elucidated.

Fish ACE2 is not susceptible to SARS-CoV-2.

• SARS-CoV-2 cannot use fish ACE2 to entry cells. • Fish cell lines (EPC, CIK, BF-2) were not susceptible to SARS-CoV-2 infection. • Proper disinfection of frozen food surfaces could prevent cold-chain transimission of SARS-CoV-2.

Replication and transcription machinery for ranaviruses: components, correlation, and functional architecture.

Background: Ranaviruses (family Iridoviridae) are promiscuous pathogens that can infect across species barriers in poikilotherms and can replicate in amphibian and fish cells and even in cultured mammalian cells. However, as nucleocytoplasmic large DNA viruses (NCLDVs), their replication and transcription mechanisms remain largely unknown. Here, we screened and uncovered the replication and transcription machinery of two ranaviruses, Andrias davidianus ranavirus (ADRV) and Rana grylio virus (RGV), by a combination of methods, including the isolation of proteins on nascent DNA, recombinant virus-based affinity, and NanoLuc complementation assay.

Two Duplicated Homeologs Cooperatively and Negatively Regulate RLR-Mediated IFN Response in Hexaploid Gibel Carp.

Src homology region 2 domain-containing phosphatase 1 (SHP1), encoded by the () gene, belongs to the family of protein tyrosine phosphatases (PTPs) and participates in multiple signaling pathways of immune cells. However, the mechanism of SHP1 in regulating fish immunity is largely unknown. In this study, we first identified two gibel carp () homeologs ( and ), each of which had three alleles with high identities.

Divergent Antiviral Mechanisms of Two Homeologs in a Recurrent Polyploid Fish.

Polyploidy and subsequent diploidization provide genomic opportunities for evolutionary innovations and adaptation. The researches on duplicated gene evolutionary fates in recurrent polyploids have seriously lagged behind that in paleopolyploids with diploidized genomes. Moreover, the antiviral mechanisms of Viperin remain largely unclear in fish.

Structural and Functional Diversity among Five RING Finger Proteins from Carassius Auratus Herpesvirus (CaHV).

herpesvirus (CaHV) has been identified as a high-virulence pathogenic virus that infects aquatic animals, but the key factor for virus-host interaction is still unclear. Five Really interesting new genes (RING) finger proteins (39L, 52L, 131R, 136L, and 143R) of CaHV were screened to determine structural diversity. RING finger proteins were also predicted in other known fish herpesviruses, with an arrangement and number similar to CaHV.

Infectious pancreatic necrosis virus inhibits infectious hematopoietic necrosis virus at the early stage of infection in a time dependent manner during Co-infection in Chinook salmon embryo cell lines.

Salmonids can be co-infected by infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV) under natural or experimental conditions. To reveal the influence of IPNV on IHNV in co-infections, CHSE-214 cells were inoculated with IPNV at different time intervals prior to or after IHNV infection. Propagation of IHNV was determined by an immunofluorescence antibody test, real-time quantitative polymerase chain reaction, flow cytometry, and virus titration.

Function characterization and expression regulation of two different-sized 3' untranslated region-containing interferon genes from clone F of gibel carp Carassius auratus gibelio.

Fish interferon (IFN)-mediated antiviral innate immunity is the first line of defense against virus invasion. In the present study, we identify two fish IFN genes (here tentatively named IFNa and IFNc) with different-sized 3' UTRs from clone F strain of gibel carp Carassius auratus gibelio. Carp IFNa has a relatively short 3'UTR without AU-rich elements (AREs) but IFNc has a long one with 9 AREs.

A transmembrane domain of ranavirus 13R is crucial for co-localization to endoplasmic reticulum and viromatrix.

, a core gene of ranavirus (ADRV), encoded a protein containing a transmembrane domain (TMD) and a restriction endonuclease-like domain. However, the characterization and function of and the protein it encodes remain unclear. In this study, Chinese giant salamander thymus cell (GSTC) was used to investigate the function of .

Fish herpesvirus protein (CaHV-138L) can target to mitochondrial protein FoF1 ATPase.

Herpesvirus infection usually relies on the interaction between viral protein and host protein to enhance replication of the enveloped virus. Fish Carassius auratus herpesvirus (CaHV) is highly pathogenic pathogen causing gill acute hemorrhages of crucian carp (Carassius auratus) and high moritality rates among those infected fish. The protein of CaHV (CaHV-138 L) containing two transmembrane (TM) domains and an immunoglobulin C-2 Type (IGc2) domain was predicted as a viral membrane protein.

Ranaviruses Bind Cells from Different Species through Interaction with Heparan Sulfate.

Ranavirus cross-species infections have been documented, but the viral proteins involved in the interaction with cell receptors have not yet been identified. Here, viral cell-binding proteins and their cognate cellular receptors were investigated using two ranaviruses, Andrias davidianus ranavirus (ADRV) and Rana grylio virus (RGV), and two different cell lines, Chinese giant salamander thymus cells (GSTC) and Epithelioma papulosum cyprinid (EPC) cells. The heparan sulfate (HS) analog heparin inhibited plaque formation of ADRV and RGV in the two cell lines by more than 80% at a concentration of 5 μg/mL.

Differential expression of innate and adaptive immune genes in the survivors of three gibel carp gynogenetic clones after herpesvirus challenge.

Background: Accompanied with rapid growth and high density aquaculture, gibel carp has been seriously threatened by Carassius auratus herpesvirus (CaHV) since 2012. In previous study, distinct CaHV resistances and immune responses were revealed in the diseased individuals of three gibel carp gynogenetic clones (A, F and H). However, little is known about the gene expression changes in the survivors after CaHV challenge, particularly their differences of innate and adaptive immune system between susceptible clone and resistant clone.

Interaction between Two Iridovirus Core Proteins and Their Effects on Ranavirus (RGV) Replication in Cells from Different Species.

The two putative proteins RGV-63R and RGV-91R encoded by virus (RGV) are DNA polymerase and proliferating cell nuclear antigen (PCNA) respectively, and are core proteins of iridoviruses. Here, the interaction between RGV-63R and RGV-91R was detected by a yeast two-hybrid (Y2H) assay and further confirmed by co-immunoprecipitation (co-IP) assays. Subsequently, RGV-63R or RGV-91R were expressed alone or co-expressed in two kinds of aquatic animal cells including amphibian Chinese giant salamander thymus cells (GSTCs) and fish cells (EPCs) to investigate their localizations and effects on RGV genome replication.

Aquatic animal viruses mediated immune evasion in their host.

Viruses are important and lethal pathogens that hamper aquatic animals. The result of the battle between host and virus would determine the occurrence of diseases. The host will fight against virus infection with various responses such as innate immunity, adaptive immunity, apoptosis, and so on.

Real-Time Dissecting the Entry and Intracellular Dynamics of Single Reovirus Particle.

Reoviruses are non-enveloped viruses with wide host range, can cause serious infections in animals, plants and microorganism, e.g., aquareovirus, which is capable of causing serious haemorrhagic in aquatic animals.

Diversity, evolutionary contribution and ecological roles of aquatic viruses.

Aquatic viruses include infected viruses in aquatic animals, plants and microorganisms, and free-floating viruses (virioplankton) in water environments. In the last three decades, a huge number of aquatic viruses, especially diverse free-floating viruses, including cyanophages, phycoviruses, archaea viruses, giant viruses, and even virophages, have been identified by virological experiments and metagenomic analyses. Based on a comprehensive introduction of aquatic virus classification and their morphological and genetic diversity, here, we summarize and outline main virus species, their evolutionary contribution to aquatic communities through horizontal gene transfer, and their ecological roles for cyanobacterial bloom termination and global biogeochemical cycling in freshwater and marine ecosystems.