Partial genetic characterisation of a novel alloherpesvirus detected by PCR in a farmed wels catfish (Silurus glanis).

By a broad-range PCR, we detected a novel herpesvirus (HV) in the specimen of a wels catfish (Silurus glanis) presenting disseminated, carp pox-like dermal lesions all over its body. The sequence analysis of the 463-bp PCR product from the viral DNA polymerase gene indicated the presence of a hitherto unknown virus, a putative member of the family Alloherpesviridae in the sample. Another PCR, targeting the terminase gene of fish HVs, provided an additional genomic fragment of over 1,000 bp. Surprisingly, the sequence of a co-amplified, off-target PCR product revealed its origin from a putative gene homologous to ORF87 and ORF45 of cyprinid HVs and anguillid herpesvirus 1 (AngHV-1), respectively. With specific primers, designed according to the genomic maps of the cyprinid and anguillid HVs, a genomic fragment of 15 kb was also amplified and sequenced by primer walking. In phylogeny inferences, based on several genes, the putative wels catfish HV clustered closest to various cyprinid HVs or to AngHV-1. The novel virus, named as silurid herpesvirus 2, represents a distinct species in the genus Cyprinivirus. However, its association with the skin disease remains unclear.

ICTV Virus Taxonomy Profile: Herpesviridae 2021.

Members of the family Herpesviridae have enveloped, spherical virions with characteristic complex structures consisting of symmetrical and non-symmetrical components. The linear, double-stranded DNA genomes of 125-241 kbp contain 70-170 genes, of which 43 have been inherited from an ancestral herpesvirus. In general, herpesviruses have coevolved with and are highly adapted to their hosts, which comprise many mammalian, avian and reptilian species. Following primary infection, they are able to establish lifelong latent infection, during which there is limited viral gene expression. Severe disease is usually observed only in the foetus, the very young, the immunocompromised or following infection of an alternative host. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Herpesviridae, which is available at ictv.global/report/herpesviridae.

Complete genome sequence of a novel fish papillomavirus detected in farmed wels catfish (Silurus glanis).

A novel papillomavirus (PV) was detected in farmed wels catfish (Silurus glanis) in Hungary showing clinical signs resembling those of wels catfish herpesvirus disease. The whole genome of Silurus glanis papillomavirus 1 (SgPV1) was identified using next-generation sequencing. The 5,612-bp complete genome contains four predicted protein coding regions (E1, E2, L1, and L2), which seem to have homologues in every PV genome sequenced to date. Five complete fish PV genome sequences are available in the GenBank database. Their genomes range between 5,748 and 6,086 bp and contain the minimal PV backbone genes E1, E2, L2, and L1, unlike PVs of higher vertebrates, which have larger genomes (6.8-8.6 kbp) and additional (onco)genes. Considering the current species demarcation criteria for the family Papillomaviridae, the establishment of a novel species named "Nunpapillomavirus siluri" is proposed for the SgPV1 in a novel genus, "Nunpapillomavirus", in the subfamily Secondpapillomavirinae.

Virus-Host Coevolution with a Focus on Animal and Human DNA Viruses.

Viruses have been infecting their host cells since the dawn of life, and this extremely long-term coevolution gave rise to some surprising consequences for the entire tree of life. It is hypothesised that viruses might have contributed to the formation of the first cellular life form, or that even the eukaryotic cell nucleus originates from an infection by a coated virus. The continuous struggle between viruses and their hosts to maintain at least a constant fitness level led to the development of an unceasing arms race, where weapons are often shuttled between the participants. In this literature review we try to give a short insight into some general consequences or traits of virus-host coevolution, and after this we zoom in to the viral clades of adenoviruses, herpesviruses, nucleo-cytoplasmic large DNA viruses, polyomaviruses and, finally, circoviruses.

Complete genome sequence and analysis of a novel lymphocystivirus detected in whitemouth croaker (Micropogonias furnieri): lymphocystis disease virus 4.

A novel lymphocystivirus causing typical signs of lymphocystis virus disease in whitemouth croaker (Micropogonias furnieri) on the coast of Uruguay was detected and described recently. Based on genetic analysis of some partially sequenced core genes, the virus seemed to differ from previously described members of the genus Lymphocystivirus. In this study, using next-generation sequencing, the whole genome of this virus was sequenced and analysed. The complete genome was found to be 211,086 bp in size, containing 148 predicted protein-coding regions, including the 26 core genes that seem to have a homologue in every iridovirus genome sequenced to date. Considering the current species demarcation criteria for the family Iridoviridae (genome organization, G+C content, amino acid sequence similarity, and phylogenetic relatedness of the core genes), the establishment of a novel species ("Lymphocystis disease virus 4") in the genus Lymphocystivirus is suggested.

Molecular detection of a novel cyprinid herpesvirus in roach (Rutilus rutilus) and asp (Leuciscus aspius) showing typical signs of carp pox disease.

In the early spring of 2018, in Lake Balaton (Hungary), a roach (Rutilus rutilus) and an asp (Leuciscus aspius) were found in an fish trap at the outlet of the river Sió showing typical signs of the so-called carp pox disease, such as foci of epidermal hyperplasia on the head and the whole body surface, including the fins. Molecular tests revealed the presence of the DNA of an unknown fish herpesvirus. Three genes encoding the DNA-dependent DNA polymerase, major capsid protein and ATPase subunit of terminase were amplified and sequenced from the alloherpesviral genome. The gene sequences of the viruses obtained from the two different fish species shared 94.4% nucleotide sequence identity (98.1% amino acid sequence identity), suggesting that they belong to the same virus species. Phylogenetic analysis based on the DNA polymerase (and the concatenated sequences of the amplified genes, as well) implied that the detected virus belongs to the genus Cyprinivirus within the family Alloherpesviridae. The sequences of the novel alloherpesvirus diverge from those of the five cyprinivirus species described previously, so it putatively represents the sixth virus species in the genus.

Diagnosis of lymphocystis disease in a novel host, the whitemouth croaker Micropogonias furnieri, associated with a putatively novel Lymphocystivirus species (LCDV-WC).

In 2015, an episode of lymphocystis disease (LCD) was detected in wild and cultured populations of whitemouth croaker Micropogonias furnieri off the coast of Uruguay. Fish of both origins were collected for histopathological and molecular investigations. Macroscopically, multinodular tumorlike masses were observed in the skin. Histological examination of these masses revealed enlarged cells with a hyaline capsule and basophilic inclusion bodies in the cytoplasm. The inclusion bodies were further examined by electron microscopy and showed icosahedral virions with a median diameter of 182 nm. Routine molecular investigations targeting the DNA polymerase and major capsid protein genes showed the presence of the DNA of an unknown lymphocystis disease virus (LCDV) in all specimens showing external signs of LCD. Subsequently, 4 other core genes were amplified and sequenced from the viral genome. Phylogenetic tree reconstruction based on the concatenated sequence of 6 core genes indicated that the virus undoubtedly belongs to the genus Lymphocystivirus. However, the core gene sequences of the whitemouth croaker LCDV differ markedly from those of the 3 known LCDVs, putatively representing a fourth LCDV species.

Complete genome analysis confirms that the pygmy marmoset adenovirus is a variant of the skunk adenovirus 1 - Short communication.

The complete genomic sequence along with phylogenetic analyses of an adenovirus (AdV), isolated from a dead captive pygmy marmoset (Callithrix pygmaea) from a Hungarian zoo is reported. Earlier, based on the phylogenetic analysis of the sequence of a PCR-amplified fragment from the DNA polymerase gene, the pygmy marmoset AdV (PMAdV) has been reported to cluster closest to certain chiropteran AdVs. In the following years similar AdVs were discovered in additional mammalian hosts, including a skunk (Mephitis mephitis), African pygmy hedgehogs (Atelerix albiventris), North American porcupines (Erethizon dorsatum) and grey fox (Urocyon cinereoargenteus). After the full genome analysis of the skunk adenovirus (SkAdV-1), a novel species Skunk mastadenovirus A (SkAdV-A) has been established. The AdVs, originating from the African pygmy hedgehogs, have been found to belong to virus species SkAdV-A. Partial gene sequences from the porcupine AdVs have also implied their very close genetic relatedness to SkAdV-A. The complete genomic sequence of PMAdV, examined in this study, was found to share 99.83% nucleotide identity with SkAdV-1, thus unequivocally represents a genomic variant of SkAdV-1. The observation that viruses classifiable as SkAdV-A are able to infect and cause diseases in several, distantly related mammals seems to deserve further studies to elucidate the infection biology of this intriguing AdV.

Detection of cyprinid herpesvirus 1 (CyHV-1) in barbel (Barbus barbus): First molecular evidence for the presence of CyHV-1 in fish other than carp (Cyprinus carpio).

Two adult barbels (Barbus barbus) with visible skin tumours were subjected to histopathological and molecular examinations. The fish were caught in the River Danube near Budapest. Papillomas were found around their oral cavity, at the operculum and at the pectoral fins, while epidermal hyperplasias were seen on the body surface. Cyprinid herpesvirus 1 (CyHV-1) was detected in the kidney of the specimens by polymerase chain reaction (PCR), and barbel circovirus 1 (BaCV1) was found in all internal organs and in the tissues of the tumours. The whole genome of BaCV1 and three conserved genes from the genome of CyHV-1 were sequenced. Previously, BaCV1 had been reported only once from a mass mortality event among barbel fry. The whole genome sequence of our circovirus shared 99.9% nucleotide identity with that of the formerly reported BaCV1. CyHV-1 is known to infect common carp and coloured carp (Cyprinus carpio), and has been assumed to infect other cyprinid fish species as well. We found the nucleotide sequences of the genes of CyHV-1 to be identical in 98.7% to those of the previous isolates from carp. To the best of our knowledge, this is the first molecular confirmation of the presence of CyHV-1 DNA in cyprinid fish species other than carp.

Isolation and complete genome sequence analysis of a novel ovine adenovirus type representing a possible new mastadenovirus species.

Pathological examination of a suckling male lamb showed severe viral pneumonia with suspected bacterial superinfection. Adenovirus was detected by immunohistochemical examination of the affected lung samples. Detection of the suspected adenovirus by PCR and subsequent isolation of the virus were successful. Using next-generation sequencing, the full genome of this ovine adenovirus was sequenced and analysed. A genome sequence comparison showed that it was a novel mastadenovirus type (named "ovine adenovirus 8") that did not belong to any of the established adenovirus species. The genome is 36,206 bp long, containing 93-bp inverted terminal repeats and 29 predicted genes, including the two genus-specific genes (encoding proteins V and IX). Ovine adenovirus 8 shows the closest relationship to ovine adenovirus 6. These two viruses seem to merit the establishment of a novel ovine mastadenovirus species for them, for which we proposed the name "Ovine mastadenovirus C".

Defining a Novel Role for the Coxsackievirus and Adenovirus Receptor in Human Adenovirus Serotype 5 Transduction In Vitro in the Presence of Mouse Serum.

Human adenoviral serotype 5 (HAdV-5) vectors have predominantly hepatic tropism when delivered intravascularly, resulting in immune activation and toxicity. Coagulation factor X (FX) binding to HAdV-5 mediates liver transduction and provides protection from virion neutralization in mice. FX is dispensable for liver transduction in mice lacking IgM antibodies or complement, suggesting that alternative transduction pathways exist. To identify novel factor(s) mediating HAdV-5 FX-independent entry, we investigated HAdV-5 transduction in vitro in the presence of serum from immunocompetent C57BL/6 or immunocompromised mice lacking IgM antibodies (Rag 2-/- and NOD-scid-gamma [NSG]). Sera from all three mouse strains enhanced HAdV-5 transduction of A549 cells. While inhibition of HAdV-5-FX interaction with FX-binding protein (X-bp) inhibited transduction in the presence of C57BL/6 serum, it had negligible effect on the enhanced transduction observed in the presence of Rag 2-/- or NSG serum. Rag 2-/- serum also enhanced transduction of the FX binding-deficient HAdV-5HVR5*HVR7*E451Q (AdT*). Interestingly, Rag 2-/- serum enhanced HAdV-5 transduction in a FX-independent manner in CHO-CAR and SKOV3-CAR cells (CHO or SKOV3 cells transfected to stably express human coxsackievirus and adenovirus receptor [CAR]). Additionally, blockade of CAR with soluble HAdV-5 fiber knob inhibited mouse serum-enhanced transduction in A549 cells, suggesting a potential role for CAR. Transduction of HAdV-5 KO1 and HAdV-5/F35 (CAR binding deficient) in the presence of Rag 2-/- serum was equivalent to that of HAdV-5, indicating that direct interaction between HAdV-5 and CAR is not required. These data suggest that FX may protect HAdV-5 from neutralization but has minimal contribution to HAdV-5 transduction in the presence of immunocompromised mouse serum. Alternatively, transduction occurs via an unidentified mouse serum protein capable of bridging HAdV-5 to CAR.IMPORTANCE The intravascular administration of HAdV-5 vectors can result in acute liver toxicity, transaminitis, thrombocytopenia, and injury to the vascular endothelium, illustrating challenges yet to overcome for HAdV-5-mediated systemic gene therapy. The finding that CAR and potentially an unidentified factor present in mouse serum might be important mediators of HAdV-5 transduction highlights that a better understanding of the complex biology defining the interplay between adenovirus immune recognition and cellular uptake mechanisms is still required. These findings are important to inform future optimization and development of HAdV-5-based adenoviral vectors for gene therapy.

Complete genome sequence and analysis of ictalurid herpesvirus 2.

Ictalurid herpesvirus 2 (IcHV-2) has been causing substantial losses in the black bullhead aquaculture industry since the 1990s. Using next-generation sequencing, the genome of IcHV-2 was completely sequenced and analysed in this study. The complete genome was found to be 142,925 bp in size, containing 77 predicted protein-coding regions, including 12 ORFs that appear to have a homologue in every alloherpesvirus genome sequenced to date. The genome organization of the IcHV-2 shows high similarity to that of IcHV-1, the founding member of the genus Ictalurivirus within the family Alloherpesviridae. A unique sequence region of 101 kbp is flanked by terminal direct repeats of 20 kbp. Thirteen of the 77 putative genes do not show homology to any known genes with sequences in public databases; six of them are found in the repeat regions. Analysis of the whole genome confirms the previously established taxonomic position of IcHV-2.

Molecular detection and genome analysis of circoviruses of European eel (Anguilla anguilla) and sichel (Pelecus cultratus).

The prevalence and distribution of piscine circoviruses (CVs) were tested in a routine virus monitoring programme in Lake Balaton, Hungary. A high prevalence of European eel CV (EeCV) was found in the apparently healthy eel population (35.5%). The copy number of the viral DNA in different organs was determined by quantitative real-time PCR. The results suggested that some eel specimens were in active viraemic status despite their asymptomatic condition. Furthermore, a novel, previously undescribed CV was also detected in eel and sichel samples. Full genome characterisation confirmed that the virus represents a novel EeCV species (EeCV-2). The genome contains an integrated eel chromosome-derived fragment, suggesting that the original host of the virus was the eel and it probably emerged subsequently in the sichel by host switching. In some samples, an additional, 1,111-nt-long circular ssDNA was also observed involving a CV-like stem-loop structure and an ORF showing homology to CV capsid protein genes, without any sign of a replication initiator protein sequence.

Molecular characterization of a lizard adenovirus reveals the first atadenovirus with two fiber genes and the first adenovirus with either one short or three long fibers per penton.

UNLABELLED: Although adenoviruses (AdVs) have been found in a wide variety of reptiles, including numerous squamate species, turtles, and crocodiles, the number of reptilian adenovirus isolates is still scarce. The only fully sequenced reptilian adenovirus, snake adenovirus 1 (SnAdV-1), belongs to the Atadenovirus genus. Recently, two new atadenoviruses were isolated from a captive Gila monster (Heloderma suspectum) and Mexican beaded lizards (Heloderma horridum). Here we report the full genomic and proteomic characterization of the latter, designated lizard adenovirus 2 (LAdV-2). The double-stranded DNA (dsDNA) genome of LAdV-2 is 32,965 bp long, with an average G+C content of 44.16%. The overall arrangement and gene content of the LAdV-2 genome were largely concordant with those in other atadenoviruses, except for four novel open reading frames (ORFs) at the right end of the genome. Phylogeny reconstructions and plesiomorphic traits shared with SnAdV-1 further supported the assignment of LAdV-2 to the Atadenovirus genus. Surprisingly, two fiber genes were found for the first time in an atadenovirus. After optimizing the production of LAdV-2 in cell culture, we determined the protein compositions of the virions. The two fiber genes produce two fiber proteins of different sizes that are incorporated into the viral particles. Interestingly, the two different fiber proteins assemble as either one short or three long fiber projections per vertex. Stoichiometry estimations indicate that the long fiber triplet is present at only one or two vertices per virion. Neither triple fibers nor a mixed number of fibers per vertex had previously been reported for adenoviruses or any other virus. IMPORTANCE: Here we show that a lizard adenovirus, LAdV-2, has a penton architecture never observed before. LAdV-2 expresses two fiber proteins-one short and one long. In the virion, most vertices have one short fiber, but a few of them have three long fibers attached to the same penton base. This observation raises new intriguing questions on virus structure. How can the triple fiber attach to a pentameric vertex? What determines the number and location of each vertex type in the icosahedral particle? Since fibers are responsible for primary attachment to the host, this novel architecture also suggests a novel mode of cell entry for LAdV-2. Adenoviruses have a recognized potential in nanobiomedicine, but only a few of the more than 200 types found so far in nature have been characterized in detail. Exploring the taxonomic wealth of adenoviruses should improve our chances to successfully use them as therapeutic tools.

Molecular detection of a putatively novel cyprinid herpesvirus in sichel (Pelecus cultratus) during a mass mortality event in Hungary.

In the early summer of 2014, mass mortality of sichel (Pelecus cultratus) was observed in Lake Balaton, Hungary. Histological examination revealed degenerative changes within the tubular epithelium, mainly in the distal tubules and collecting ducts in the kidneys and multifocal vacuolisation in the brain stem and cerebellum. Routine molecular investigations showed the presence of the DNA of an unknown alloherpesvirus in some specimens. Subsequently, three genes of the putative herpesviral genome (DNA polymerase, terminase, and helicase) were amplified and partially sequenced. A phylogenetic tree reconstruction based on the concatenated sequence of these three conserved genes implied that the virus belongs to the genus Cyprinivirus within the family Alloherpesviridae. The sequences of the sichel herpesvirus differ markedly from those of the cypriniviruses CyHV-1, CyHV-2 and CyHV-3, putatively representing a fifth species in the genus.

Full genome sequence of a novel circo-like virus detected in an adult European eel Anguilla anguilla showing signs of cauliflower disease.

An adult European eel Anguilla anguilla, showing typical signs of the so-called cauliflower disease, was subjected to pathological and molecular virological examinations. Samples taken from internal organs and the polypoid proliferative tissue from the mouth were examined by PCR for the detection of several viruses. Positive results were obtained with a nested PCR targeting the rep gene of circoviruses. Analysis of the partial rep sequence indicated the presence of a putative novel circovirus, but attempts to isolate it remained unsuccessful. The missing part of the genome was acquired by an inverse nested PCR with 2 specific primer pairs, designed from the newly determined rep sequence, followed by genome walking. The circular full genome was found to consist of 1378 nt (GenBank accession no. KC469701). Two oppositely oriented open reading frames (ORFs) were present, of which one was unambiguously identified as a circoviral rep gene. However, the predicted product of the other ORF, though it is a clear positional counterpart of the cap genes, showed no obvious homology to any known circoviral capsid proteins. A stem-loop-like element in the intergenic region between the 5' ends of the ORFs was also found. Phylogenetic calculations indicated that the novel virus belongs to the genus Circovirus in the family Circoviridae. The relative amount of the viral DNA in the organ samples was estimated by quantitative real-time PCR. The results suggested that the examined fish was caught in an active viremic state, although the role of this circovirus in the etiology of the cauliflower diseases could not be ascertained.

Atlantic salmon papillomatosis in Russia and molecular characterization of the associated herpesvirus.

Papillomatosis of Atlantic salmon Salmo salar has been reported for decades in Russia, Scandinavia and Scotland. The disease is typically benign although heavy losses have occasionally been reported. A herpesviral etiology has been suggested based on ultrastructural evidence; however, the virus has not been isolated or genetically characterized. In this study, we provide the first viral sequences detected in the papillomas from diseased Russian Atlantic salmon. Phylogenetic analyses, based on the partial sequences of the herpesviral polymerase and terminase genes, supported the virus as a novel member of the genus Salmonivirus within the family Alloherpesviridae. The sequences of the Atlantic salmon papillomatosis virus differ markedly from those of the 3 known salmoniviruses; therefore, the authors propose the species designation Salmonid herpesvirus 4 to be considered for approval by the International Committee on Taxonomy of Viruses.

Silver Nanoparticles Proved to Be Efficient Antivirals In Vitro against Three Highly Pathogenic Fish Viruses.

The efficacy of silver nanoparticles (AgNPs) was tested in vitro against three different fish viruses, causing significant economic damage in aquaculture. These viruses were the spring viraemia of carp virus (SVCV), European catfish virus (ECV), and Ictalurid herpesvirus 2 (IcHV-2). The safe concentration of AgNPs that did not cause cytotoxic effects in EPC cells proved to be 25 ng/mL. This dose of AgNPs decreased significantly (5-330×) the viral load of all three viruses in three different types of treatments (virus pre-treatment, cell pre-treatment, and cell post-treatment with the AgNPs). In a higher concentration, the AgNPs proved to be efficient against ECV and IcHV-2 even in a delayed post-cell-treatment experiment (AgNP treatment was applied 24 h after the virus inoculation). These first in vitro results against three devastating fish viruses are encouraging to continue the study of the applicability of AgNPs in aquaculture in the future.

Genome sequence of white sturgeon herpesvirus 1 isolated from farmed white sturgeon (Acipenser transmontanus).

The genome sequence of white sturgeon herpesvirus 1, which was isolated from farmed white sturgeon (Acipenser transmontanus), was determined. Comparative analyses suggest the classification of this virus as a new species in a new genus in the family Alloherpesviridae.

Juvenile Wels Catfish (Silurus glanis) Display Age-Related Mortality to European Catfish Virus (ECV) under Experimental Conditions.

We have limited knowledge about the course of the European catfish virus (ECV) infection in different age groups of wels catfish (Silurus glanis). The results of this study demonstrate that an ECV strain isolated from the brown bullhead (Ameiurus nebulosus) in Hungary could cause devastating losses among juvenile wels catfish. Furthermore, the age-related mortality rate following ECV infection was investigated in three virus challenge experiments at two different virus dosages. Eight-week-old (ca. 3 g), ten-week-old (ca. 8 g), and sixteen-week-old (ca. 55 g) catfish were infected with ECV at 21°C. In the youngest age group, 96% (at a 106 TCID50/mL dosage) and 100% (at 105 TCID50/mL) mortality rates were observed, while these rates were reduced to 56% and 68% in the ten-week-old groups, respectively. The mortality was significantly higher in the virus-exposed groups than in the control ones. In the sixteen-week-old group, 23% mortality was detected at a 105 TCID50/mL concentration of ECV. Here, a significant difference was not found between the exposed and control groups. The performed experiments show that different age groups of wels catfish may have various susceptibility to ECV. These findings draw attention to the importance of the prevention of/protection against virus infections in juvenile (up to 3-month-old) wels catfish in aquaculture.