Genetic content and evolution of adenoviruses

Pathogenicity and complete genome sequence of a fowl adenovirus serotype 8b isolate from China

In this study, we determined and analyzed the complete nucleotide sequence of the genome of a fowl adenovirus isolate SD1356 in China and examined its pathogenicity in specific pathogen-free chick embryos and newly hatched chicks. The full genome of SD1356 was 44,454 nucleotides in length with 58.1% G + C content. Sequence alignment and phylogenetic analysis revealed that strain SD1356 was clustered together belonging to serotype 8b of fowl adenoviruses E species (FAdV-8b). No regions homologous to early regions E1, E3, and E4 of mastadenoviruses were recognized, and being very similar to the typical organization of FAdV-E genomes. All infected embryos died 4-6 d post-inoculation with visible lesions, such as hyperemic, stunting, and clubbed down, etc. Additionally, adenovirus was found in tissues or cloacal swabs of all infected birds and most of the contact uninfected controls, despite lack of clinical signs and pathological changes. Together, our study describes the genomic characteristics of an FAdV-8b strain isolated in China. The reported FAdV-8b strain SD1356 is fetal to chick embryos and possesses horizontal transmission capacity in chickens.

Challenges in management of epidemic keratoconjunctivitis with emerging recombinant human adenoviruses

Adenoviral epidemic keratoconjunctivitis (EKC) presents as severe conjunctival inflammations involving the cornea that can lead to the development of corneal opacities and blurred vision, which can persist for months. EKC is highly contagious and responsible for outbreaks worldwide, therefore accurate diagnosis and rapid containment are imperative. EKC is caused by a number of types within Human adenovirus species D (HAdV-D): 8, 37 and 64 (formerly known as 19a) and these types were considered the major causes of EKC for over fifty years. Nonetheless, recent improved molecular typing methodologies have identified recombinant HAdV-D types 53, 54 and 56, as newly emerging etiologic agents of EKC infections worldwide. EKC cases due to these recombinant types have potentially been underdiagnosed and underestimated as a source of new EKC outbreaks. Recombination events among circulating HAdV-D types represent a source of new infectious disease threats. Also, the growing number of adenoviral types enabled genomic and phenotypic comparisons to determine pathological properties related to EKC. This review covers the clinical features of EKC, current challenges in clinical practice and recent progress in EKC-related HAdV research, which focuses on the development of novel diagnostic and therapeutic approaches.

In vitro growth kinetics and gene expression analysis of the turkey adenovirus 3, a siadenovirus

Turkey adenovirus 3 (TAdV-3) belongs to the genus Siadenovirus, family Adenoviridae. Previously, nucleotide sequencing and annotation of the Virginia avirulent strain (VAS) of TAdV-3 genome, isolated in our laboratory, indicated the presence of a total of 23 genes and open reading frames (ORFs). The goals of this study were 1) to delineate the growth kinetics of the virus using a qPCR-based infectivity assay, and 2) to determine the virus gene expression profile during the early and late phases of infection in target B lymphocytes. The one-step growth curve experiment demonstrated 3 phases of virus replication cycle: a lag phase lasted for 12-18 h post-infection (h.p.i.), in which the virus titer declined; a log phase from 18 to 120 h.p.i., in which the number of infectious virus particles increased over 20,000 folds, and a brief decline phase thereafter. Southern blot analysis indicated that the synthesis of new viral DNA started by 8 h.p.i. Gene-specific RT-PCR analysis revealed the expression of mRNAs from the 23 TAdV-3 genes/ORFs. According to the temporal transcriptional profiling of TAdV-3 genome, genes could be divided into 3 groups based on the time of transcription initiation: group 1 showed detectable levels of transcription at 2 h.p.i and included 7 genes, i.e., hyd, III, pX, pVI, II, 100 K, and 33 K; group 2 included 12 genes whose mRNAs were detected for the first time at 4 h.p.i., i.e., ORF1, IVa2, pol, pTP, pIIIa, EP, DBP, E3, U exon, IV, ORF7, and ORF8; group 3 of transcripts were detectable starting 8 h.p.i. and included only 4 genes, i.e., 52 K, 22 K, pVII, and pVIII. Our data suggest that the transcriptional kinetics of genus Siadenovirus differ from that observed in other adenoviral genera; however, a few TAdV-3 genes showed similar expression patterns to their adenoviral homologs.

Protracted course of disseminated adenovirus disease with necrotizing granulomas in the liver

A 52- year-old male with chronic lymphocytic leukemia was hospitalized with disseminated adenovirus disease. More than a month following recovery, hepatic necrotizing granulomas secondary to adenovirus were found. This case illustrates the protracted course that adenovirus disease may take and emphasizes an unusual presentation with hepatic necrotizing granulomas.

Emerging Themes in PDZ Domain Signaling: Structure, Function, and Inhibition

Post-synaptic density-95, disks-large and zonula occludens-1 (PDZ) domains are small globular protein-protein interaction domains widely conserved from yeast to humans. They are composed of ∼90 amino acids and form a classical two α-helical/six β-strand structure. The prototypical ligand is the C-terminus of partner proteins; however, they also bind internal peptide sequences. Recent findings indicate that PDZ domains also bind phosphatidylinositides and cholesterol. Through their ligand interactions, PDZ domain proteins are critical for cellular trafficking and the surface retention of various ion channels. In addition, PDZ proteins are essential for neuronal signaling, memory, and learning. PDZ proteins also contribute to cytoskeletal dynamics by mediating interactions critical for maintaining cell-cell junctions, cell polarity, and cell migration. Given their important biological roles, it is not surprising that their dysfunction can lead to multiple disease states. As such, PDZ domain-containing proteins have emerged as potential targets for the development of small molecular inhibitors as therapeutic agents. Recent data suggest that the critical binding function of PDZ domains in cell signaling is more than just glue, and their binding function can be regulated by phosphorylation or allosterically by other binding partners. These studies also provide a wealth of structural and biophysical data that are beginning to reveal the physical features that endow this small modular domain with a central role in cell signaling.

Current Use of Adenovirus Vectors and Their Production Methods

Various adenovirus (AdV) vector systems have proven to be lucrative options for gene delivery. They can serve as potential vaccine candidates for prevention of several common infectious diseases and hold the promise for gene therapy, especially for cancer. Several AdV vector-based therapies are currently at various stages of clinical trials worldwide, which make an immense interest of both the clinicians and researchers. Since these vectors are easy to manipulate, have broad tropism, and have the capability to yield high titers, this delivery system has a wide range of applications for different clinical settings. This chapter emphasizes on some of the current usages of AdV vectors and their production methods.

αvβ3 Integrin Is Required for Efficient Infection of Epithelial Cells with Human Adenovirus Type 26

Human adenoviruses (HAdVs) are being explored as vectors for gene transfer and vaccination. Human adenovirus type 26 (HAdV26), which belongs to the largest subgroup of adenoviruses, species D, has a short fiber and a so-far-unknown natural tropism. Due to its low seroprevalence, HAdV26 has been considered a promising vector for the development of vaccines. Despite the fact that the in vivo safety and immunogenicity of HAdV26 have been extensively studied, the basic biology of the virus with regard to receptor use, cell attachment, internalization, and intracellular trafficking is poorly understood. In this work, we investigated the roles of the coxsackievirus and adenovirus receptor (CAR), CD46, and αv integrins in HAdV26 infection of human epithelial cell lines. By performing different gain- and loss-of-function studies, we found that αvβ3 integrin is required for efficient infection of epithelial cells by HAdV26, while CAR and CD46 did not increase the transduction efficiency of HAdV26. By studying intracellular trafficking of fluorescently labeled HAdV26 in A549 cells and A549-derived cell clones with stably increased expression of αvβ3 integrin, we observed that HAdV26 colocalizes with αvβ3 integrin and that increased αvβ3 integrin enhances internalization of HAdV26. Thus, we conclude that HAdV26 uses αvβ3 integrin as a receptor for infecting epithelial cells. These results give us new insight into the HAdV26 infection pathway and will be helpful in further defining HAdV-based vector manufacturing and vaccination strategies.IMPORTANCE Adenovirus-based vectors are used today for gene transfer and vaccination. HAdV26 has emerged as a promising candidate vector for development of vaccines due to its relatively low seroprevalence and its ability to induce potent immune responses against inserted transgenes. However, data regarding the basic biology of the virus, like receptor usage or intracellular trafficking, are limited. In this work, we found that efficient infection of human epithelial cell lines by HAdV26 requires the expression of the αvβ3 integrin. By studying intracellular trafficking of fluorescently labeled HAdV26 in a cell clone with stably increased expression of αvβ3 integrin, we observed that HAdV26 colocalizes with αvβ3 integrin and confirmed that αvβ3 integrin expression facilitates efficient HAdV26 internalization. These results will allow further improvement of HAdV26-based vectors for gene transfer and vaccination.

Combined Genetic and Chemical Capsid Modifications of Adenovirus-Based Gene Transfer Vectors for Shielding and Targeting

Adenovirus vectors are potent tools for genetic vaccination and oncolytic virotherapy. However, they are prone to multiple undesired vector-host interactions, especially after in vivo delivery. It is a consensus that the limitations imposed by undesired vector-host interactions can only be overcome if defined modifications of the vector surface are performed. These modifications include shielding of the particles from unwanted interactions and targeting by the introduction of new ligands. The goal of the protocol presented here is to enable the reader to generate shielded and, if desired, retargeted human adenovirus gene transfer vectors or oncolytic viruses. The protocol will enable researchers to modify the surface of adenovirus vector capsids by specific chemical attachment of synthetic polymers, carbohydrates, lipids, or other biological or chemical moieties. It describes the cutting-edge technology of combined genetic and chemical capsid modifications, which have been shown to facilitate the understanding and overcoming of barriers for in vivo delivery of adenovirus vectors. A detailed and commented description of the crucial steps for performing specific chemical reactions with biologically active viruses or virus-derived vectors is provided. The technology described in the protocol is based on the genetic introduction of (naturally absent) cysteine residues into solvent-exposed loops of adenovirus-derived vectors. These cysteine residues provide a specific chemical reactivity that can, after production of the vectors to high titers, be exploited for highly specific and efficient covalent chemical coupling of molecules from a wide variety of substance classes to the vector particles. Importantly, this protocol can easily be adapted to perform a broad variety of different (non-thiol-based) chemical modifications of adenovirus vector capsids. Finally, it is likely that non-enveloped virus-based gene transfer vectors other than adenovirus can be modified from the basis of this protocol.

Porcine Adenovirus Type 3 E3 Encodes a Structural Protein Essential for Capsid Stability and Production of Infectious Progeny Virions

The adenovirus E3 region encodes proteins that are not essential for viral replication in vitro The porcine adenovirus type 3 (PAdV-3) E3 region encodes three proteins, including 13.7K. Here, we report that 13.7K is expressed as an early protein, which localizes to the nucleus of infected cells. The 13.7K protein is a structural protein, as it is incorporated in CsCl-purified virions. The 13.7K protein appears to be essential for PAdV-3 replication, as mutant PAV13.7^3A expressing a mutated 13.7K could be isolated only in VIDO AS2 cells expressing the 13.7K protein. Analysis of PAV13.7^3A suggested that even in the presence of reduced levels of some late viral proteins, there appeared to be no effect on virus assembly and production of mature virions. Further analysis of CsCl-purified PAV13.7^3A by transmission electron microscopy revealed the presence of disrupted/broken capsids, suggesting that inactivation of 13.7K protein expression may produce fragile capsids. Our results suggest that the PAdV-3 E3 region-encoded 13.7K protein is a capsid protein, which appears to be essential for the formation of stable capsids and production of infectious progeny virions.IMPORTANCE Although E3 region-encoded proteins are involved in the modulation of leukocyte functions (N. Arnberg, Proc Natl Acad Sci U S A 110:19976-19977, 2013) and inducing a lytic infection of lymphocytes (V. K. Murali, D. A. Ornelles, L. R. Gooding, H. T. Wilms, W. Huang, A. E. Tollefson, W. S. Wold, and C. Garnett-Benson, J Virol 88:903-912, 2014), none of the E3 proteins appear to be a component of virion capsid or required for replication of adenovirus. Here, we demonstrate that the 13.7K protein encoded by the E3 region of porcine adenovirus type 3 is a component of progeny virion capsids and appears to be essential for maintaining the integrity of virion capsid and production of infectious progeny virions. To our knowledge, this is the first report to suggest that an adenovirus E3-encoded protein is an essential structural protein.

Interplay between sequence, structure and linear motifs in the adenovirus E1A hub protein

E1A is the main transforming protein in mastadenoviruses. This work uses bioinformatics to extrapolate experimental knowledge from Human adenovirus serotype 5 and 12 E1A proteins to all known serotypes. A conserved domain architecture with a high degree of intrinsic disorder acts as a scaffold for multiple linear motifs with variable occurrence mediating the interaction with over fifty host proteins. While linear motifs contribute strongly to sequence conservation within intrinsically disordered E1A regions, motif repertoires can deviate significantly from those found in prototypical serotypes. Close to one hundred predicted residue-residue contacts suggest the presence of stable structure in the CR3 domain and of specific conformational ensembles involving both short- and long-range intramolecular interactions. Our computational results suggest that E1A sequence conservation and co-evolution reflect the evolutionary pressure to maintain a mainly disordered, yet non-random conformation harboring a high number of binding motifs that mediate viral hijacking of the cell machinery.

Widespread occurrence of squirrel adenovirus 1 in red and grey squirrels in Scotland detected by a novel real-time PCR assay

The Eurasian Red Squirrel (Sciurus vulgaris) is distributed throughout large parts of Europe and Asia. However, its distribution in certain regions of Europe is endangered by the invasive, non-native Grey Squirrel (Sciurus carolinensis). Adenoviruses were already described in squirrels in Great Britain almost two decades ago. In 2013, a squirrel adenovirus (SqAdV-1) was additionally found in a red squirrel from Germany, which suffered from acute diffuse catarrhal enteritis, and the complete genome sequence was determined. Here, samples from dead red (n = 25) and grey (n = 12) squirrels collected in Scotland, UK, were analysed for the presence of this squirrel-associated virus. By using a newly developed real-time PCR targeting the adenoviral polymerase gene, viral DNA was detected in at least one of four tissue samples tested per animal in 64.0% of the red squirrels and 41.7% of the grey squirrels. Exceptionally high viral genome loads were detected in the intestine and liver, but SqAdV-1 DNA was also present in lung and kidney samples of affected animals. Almost complete genome sequence determination of a red squirrel-derived SqAdV-1 strain from Scotland indicated a very high degree of identity to the first German strain. Sequence analysis of the hexon gene, which encodes one of the major antigens of the virion, revealed an identity of 100% between viruses found in red and grey squirrels from Scotland. In conclusion, SqAdV-1 appears to be widespread in the Scottish red and grey squirrel population, which highlights the necessity for continuous wildlife surveillance. The novel real-time PCR assay offers a highly sensitive and robust method for SqAdV-1 surveillance.

Adenoviromics: Mining the Human Adenovirus Species D Genome

Human adenovirus (HAdV) infections cause disease world-wide. Whole genome sequencing has now distinguished 90 distinct genotypes in 7 species (A-G). Over half of these 90 HAdVs fall within species D, with essentially all of the HAdV-D whole genome sequences generated in the last decade. Herein, we describe recent new findings made possible by mining of this expanded genome database, and propose future directions to elucidate new functional elements and new functions for previously known viral components.

Capsid Engineering of Adenovirus Vectors: Overcoming Early Vector-Host Interactions for Therapy

Adenovirus-based vectors comprise the most frequently used vector type in clinical studies to date. Both intense lab research and insights from the clinical trials reveal the importance of a comprehensive understanding of vector-host interactions. Especially for systemic intravenous adenovirus vector delivery, it is paramount to develop safe and efficacious vectors. Very early vector-host interactions that take place in blood long before the first cell is being transduced are phenomena triggered by the surface, shape, and size of the adenovirus vector particles. Not surprisingly, a multitude of different technologies ranging from genetics to chemistry has been developed to alter the adenovirus vector surface. In this review, we discuss the most important technologies and evaluate them for their suitability to overcome hurdles imposed by early vector-host interactions.

Novel Divergent Polar Bear-Associated Mastadenovirus Recovered from a Deceased Juvenile Polar Bear

Cross-species transmission of viral pathogens is becoming an increasing problem for captive-animal facilities. This study highlights how animals in captivity are vulnerable to novel opportunistic pathogens, many of which do not result in straightforward diagnosis from symptoms and histopathology. In this study, a novel pathogen was suspected to have contributed to the death of a juvenile polar bear. HTS techniques were employed, and a novel Mastadenovirus was isolated. The virus was present in both the tissue and blood samples. Phylogenetic analysis of the virus at both the gene and genome levels revealed that it is highly divergent to other known mastadenoviruses. Overall, this study shows that animals in isolated conditions still come into contact with novel pathogens, and for many of these pathogens, the host reservoir and mode of transmission are yet to be determined.

Polar bears in captivity can be exposed to opportunistic pathogens not present in their natural environments. A 4-month-old polar bear (Ursus maritimus) living in an isolated enclosure with his mother in the Tierpark Berlin, Berlin, Germany, was suffering from severe abdominal pain, mild diarrhea, and loss of appetite and died in early 2017. Histopathology revealed severe hepatic degeneration and necrosis without evidence of inflammation or inclusion bodies, although a viral infection had been suspected on the basis of the clinical signs. We searched for nucleic acids of pathogens by shotgun high-throughput sequencing (HTS) from genomic DNA and cDNA extracted from tissue and blood. We identified a novel Mastadenovirus and assembled a nearly complete genome from the shotgun sequences. Quantitative PCR (qPCR) revealed that viral DNA was present in various concentrations in all tissues examined and that the highest concentrations were found in blood. Viral culture did not yield cytopathic effects, but qPCR suggested that virus replication was sustained for up to three passages. Positive immunofluorescence staining confirmed that the virus was able to replicate in the cells during early passage. Phylogenetic analysis demonstrated that the virus is highly divergent compared to other previously identified Mastadenovirus members and basal to most known viral clades. The virus was found only in the 4-month-old bear and not in other captive polar bears tested. We surmised, therefore, that the polar bear was infected from an unknown reservoir, illustrating that adenoviral diversity remains underestimated and that cross-species transmission of viruses can occur even under conditions of relative isolation.

IMPORTANCE Cross-species transmission of viral pathogens is becoming an increasing problem for captive-animal facilities. This study highlights how animals in captivity are vulnerable to novel opportunistic pathogens, many of which do not result in straightforward diagnosis from symptoms and histopathology. In this study, a novel pathogen was suspected to have contributed to the death of a juvenile polar bear. HTS techniques were employed, and a novel Mastadenovirus was isolated. The virus was present in both the tissue and blood samples. Phylogenetic analysis of the virus at both the gene and genome levels revealed that it is highly divergent to other known mastadenoviruses. Overall, this study shows that animals in isolated conditions still come into contact with novel pathogens, and for many of these pathogens, the host reservoir and mode of transmission are yet to be determined.

Adaptation by copy number variation in monopartite viruses

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Viral gene amplification allows rapid adaptation, especially for large DNA viruses.

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Amplifications often incur fitness costs for viral replication.

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Adaptive mutations can arise in the expanded locus or elsewhere enabling collapse.

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Genome amplifications provide genetic substrate for the evolution of modified or new functions.

Viruses evolve rapidly in response to host defenses and to exploit new niches. Gene amplification, a common adaptive mechanism in prokaryotes, archaea, and eukaryotes, has also contributed to viral evolution, especially of large DNA viruses. In experimental systems, gene amplification is one mechanism for rapidly overcoming selective pressures. Because the amplification generally incurs a fitness cost, emergence of adaptive point mutations within the amplified locus or elsewhere in the genome can enable collapse of the locus back to a single copy. Evidence of gene amplification followed by subfunctionalization or neofunctionalization of the copies is apparent by the presence of families of paralogous genes in many DNA viruses. These observations suggest that copy number variation has contributed broadly to virus evolution.

Sequential circulation of canine adenoviruses 1 and 2 in captive wild carnivores, France

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Two canine adenoviruses (CAdVs) were found to circulate sequentially in captive wild carnivores in France.

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CAdV-1 caused the death of a Eurasian wolf (Canis lupus lupus) with gross lesions and histopathological changes compatible with infectious canine hepatitis.

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CAdV-2 was subsequently found to circulate subclinically in other carnivores of the same zoological park.

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Analysis of the full-length genome of the wolf CAdV-1 strain showed a high genetic relatedness with an Italian strain detected in the same species.

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Future studies are needed to assess the CAdV ecology in endangered wild carnivores.

Scarce data are currently available about the ecology of canine adenoviruses (CAdVs) in wild carnivores. In this paper, the consecutive circulation of CAdV-1 and CAdV-2 in wild carnivores maintained in a French zoological park is reported. A fatal CAdV-1 infection was observed in a Eurasian wolf (Canis lupus lupus), which displayed gross lesions, histopathological changes and immunohistochemical findings suggestive of CAdV-1 infection. The virus was isolated on cell cultures and its genome was determined through next-generation sequencing, resulting genetically related to a recent Italian CAdV-1 strain detected in an Italian wolf. Subsequently, subclinical circulation of CAdV-2 was demonstrated by molecular methods in wild carnivores maintained in the same zoological park, some of which had been previously vaccinated with a CAdV-2 vaccine. Virus detection at a long distance from vaccination and by unvaccinated animals was suggestive of infection by a CAdV-2 field strain, although no data are available about the extent and duration of shedding of CAdV-2 modified-live virus in wild or domestic carnivores. The present paper provides new insights into the CAdV ecology in wildlife, although future studies are needed to fully understand the pathogenic potential of both CAdVs especially in endangered carnivore species.

Oncolytic adenovirus Ad657 for systemic virotherapy against prostate cancer

Background

Human species C adenovirus serotype 5 (Ad5) is the archetype oncolytic adenovirus and has been used in the vast majority of preclinical and clinical tests. While Ad5 can be robust, species C Ad6 has lower seroprevalence, side effects, and appears to be more potent as a systemic therapy against a number of tumors than Ad5. Historically, there have only been four species C human adenoviruses: serotypes 1, 2, 5, and 6. More recently a new species C adenovirus, Ad57, was identified. Ad57 is most similar to Ad6 with virtually all variation in their capsid proteins occurring in the hypervariable regions (HVRs) of their hexon proteins. Most adenovirus neutralizing antibodies target the HVRs on adenoviruses. This led us to replace the hexon HVRs in Ad6 with those from Ad57 to create a new virus called Ad657 and explore this novel species C platform’s utility as an oncolytic virus.

Methods

The HVR region from Ad57 was synthesized and used to replace the Ad6 HVR region by homologous recombination in bacteria generating a new viral platform that we call Ad657. Replication-competent Ad5, Ad6, and Ad657 were compared in vitro and in vivo for liver damage and oncolytic efficacy against prostate cancers after single intravenous treatment in mice.

Results

Ad5, Ad6, and Ad657 had similar in vitro oncolytic activity against human prostate cancer cells. Ad5 provoked the highest level of liver toxicity after intravenous injection and Ad657 caused the least damage in mice. Previous data demonstrated that Ad6 was superior to Ad5 at killing distant subcutaneous prostate cancer tumors in mouse models after a intravenous injection. Given this, Ad657 was compared to the Ad6 benchmark virus by single intravenous injection into mice bearing subcutaneous human DU145 prostate cancers. Under these conditions, Ad657 first infected the liver and then reached distant tumors. Both Ad6 and Ad657 mediated significant delays in tumor growth and extension of survival with Ad6 mediating higher efficacy.

Conclusions

These data suggest that Ad657 may have utility as a local or systemic oncolytic virotherapy for prostate cancers. These data also lay the foundation for serotype-switching with oncolytic species C Ads.

Serotype-specific restriction of wild-type adenoviruses by the cellular Mre11-Rad50-Nbs1 complex

During viral replication in the nucleus, the DNA genomes of adenoviruses are accessible to cellular DNA-binding proteins. Human adenovirus type 5 (Ad5) targets the cellular Mre11-Rad50-Nbs1 complex (MRN) to evade detection by the DNA damage response (DDR). Ad5 mutants that cannot target MRN have reduced viral propagation. Previous studies showed that diverse adenovirus serotypes interact differently with MRN. While these studies revealed diverse MRN interactions among serotypes, it remains unclear how these differences influence viral replication. Here, we examined effects of the DDR on several adenovirus serotypes. We demonstrate that wild-type Ad9 and Ad12 do not overcome MRN impairment. We also examined viral proteins involved in targeting MRN and found that unlike Ad5-E4orf3, expression of Ad9-E4orf3 is not sufficient for MRN mislocalization observed during infection. We conclude that adenovirus serotypes target MRN in distinct ways, and the MRN complex can impair DNA replication of wild-type viruses across the adenovirus family.

Molecular epidemiology of human adenovirus infections in Denmark, 2011-2016

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We developed new primers to improve genotyping of HAdV D.

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Six out of seven HAdV species from at least 13 HAdV types were identified.

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Young children (<5 years old) were more likely to be positive for HAdV.

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Co-infections with other gastrointestinal or respiratory viruses were common.

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A HAdV surveillance system is required to monitor circulating species and types.

Background

Human adenoviruses (HAdVs) can cause respiratory tract infections, conjunctivitis, diarrhoea and outbreaks have been reported. However, little is known about the disease burden and the molecular epidemiology of HAdV.

Objectives

To retrospectively perform a molecular characterization of HAdV positive samples received at Statens Serum Institut during the period 2011–2016 and to compare this with demographic information, geographic location, sample collection date and type and co-infection with other viral pathogens.

Study design

152 HAdV positive samples were genotyped by Sanger sequencing of a fragment of the hexon gene using published primers along with a newly developed primer set for enhanced genotyping of HAdV D. Phylogenetic analysis was used for genotyping and genotypes were compared with epidemiological information. In addition, HAdV burden and co-infection was evaluated for samples tested in laboratory analysis packages.

Results

Six out of seven HAdV species were identified and represented by 13 types. Young children (<5 years old) were more likely to be positive for HAdV and co-infections with other gastrointestinal or respiratory viruses were common. Possible outbreaks of ocular infections due to HAdV D could not be confirmed.

Conclusion

A diverse set of HAdV species were circulating in Denmark in the study period and although possible transmission clusters were identified, this could not be verified with current genotyping methods Young children were commonly affected by HAdV infection and co-infections with other viral pathogens were frequent suggesting a possible underestimation of the real HAdV burden.

An Engineered Virus Library as a Resource for the Spectrum-wide Exploration of Virus and Vector Diversity

Adenoviruses (Ads) are large human-pathogenic double-stranded DNA (dsDNA) viruses presenting an enormous natural diversity associated with a broad variety of diseases. However, only a small fraction of adenoviruses has been explored in basic virology and biomedical research, highlighting the need to develop robust and adaptable methodologies and resources. We developed a method for high-throughput direct cloning and engineering of adenoviral genomes from different sources utilizing advanced linear-linear homologous recombination (LLHR) and linear-circular homologous recombination (LCHR). We describe 34 cloned adenoviral genomes originating from clinical samples, which were characterized by next-generation sequencing (NGS). We anticipate that this recombineering strategy and the engineered adenovirus library will provide an approach to study basic and clinical virology. High-throughput screening (HTS) of the reporter-tagged Ad library in a panel of cell lines including osteosarcoma disease-specific cell lines revealed alternative virus types with enhanced transduction and oncolysis efficiencies. This highlights the usefulness of this resource.

Human Adenovirus Core Protein V Is Targeted by the Host SUMOylation Machinery To Limit Essential Viral Functions

Human adenoviruses (HAdV) are nonenveloped viruses containing a linear, double-stranded DNA genome surrounded by an icosahedral capsid. To allow proper viral replication, the genome is imported through the nuclear pore complex associated with viral core proteins. Until now, the role of these incoming virion proteins during the early phase of infection was poorly understood. The core protein V is speculated to bridge the core and the surrounding capsid. It binds the genome in a sequence-independent manner and localizes in the nucleus of infected cells, accumulating at nucleoli. Here, we show that protein V contains conserved SUMO conjugation motifs (SCMs). Mutation of these consensus motifs resulted in reduced SUMOylation of the protein; thus, protein V represents a novel target of the host SUMOylation machinery. To understand the role of protein V SUMO posttranslational modification during productive HAdV infection, we generated a replication-competent HAdV with SCM mutations within the protein V coding sequence. Phenotypic analyses revealed that these SCM mutations are beneficial for adenoviral replication. Blocking protein V SUMOylation at specific sites shifts the onset of viral DNA replication to earlier time points during infection and promotes viral gene expression. Simultaneously, the altered kinetics within the viral life cycle are accompanied by more efficient proteasomal degradation of host determinants and increased virus progeny production than that observed during wild-type infection. Taken together, our studies show that protein V SUMOylation reduces virus growth; hence, protein V SUMOylation represents an important novel aspect of the host antiviral strategy to limit virus replication and thereby points to potential intervention strategies.IMPORTANCE Many decades of research have revealed that HAdV structural proteins promote viral entry and mainly physical stability of the viral genome in the capsid. Our work over the last years showed that this concept needs expansion as the functions are more diverse. We showed that capsid protein VI regulates the antiviral response by modulation of the transcription factor Daxx during infection. Moreover, core protein VII interacts with SPOC1 restriction factor, which is beneficial for efficient viral gene expression. Here, we were able to show that core protein V also represents a novel substrate of the host SUMOylation machinery and contains several conserved SCMs; mutation of these consensus motifs reduced SUMOylation of the protein. Unexpectedly, we observed that introducing these mutations into HAdV promotes adenoviral replication. In conclusion, we offer novel insights into adenovirus core proteins and provide evidence that SUMOylation of HAdV factors regulates replication efficiency.

Structural and functional annotation of hypothetical proteins of human adenovirus: prioritizing the novel drug targets

OBJECTIVE

Human adenoviruses are small double stranded DNA viruses that provoke vast array of human diseases. Next generation sequencing techniques increase genomic data of HAdV rapidly, which increase their serotypes. The complete genome sequence of human adenovirus shows that it contains large amount of proteins with unknown cellular or biochemical function, known as hypothetical proteins. Hence, it is indispensable to functionally and structurally annotate these proteins to get better understanding of the novel drug targets. The purpose was the characterization of 38 randomly retrieved hypothetical proteins through determination of their physiochemical properties, subcellular localization, function, structure and ligand binding sites using various sequence and structure based bioinformatics tools.

RESULTS

Function of six hypothetical proteins P03269, P03261, P03263, Q83127, Q1L4D7 and I6LEV1 were predicted confidently and then used further for structure analysis. We found that these proteins may act as DNA terminal protein, DNA polymerase, DNA binding protein, adenovirus E3 region protein CR1 and adenoviral protein L1. Functional and structural annotation leading to detection of binding sites by means of docking analysis can indicate potential target for therapeutics to defeat adenoviral infection.

Characterization of a Novel Bat Adenovirus Isolated from Straw-Colored Fruit Bat (Eidolon helvum)

Bats are important reservoirs for emerging zoonotic viruses. For extensive surveys of potential pathogens in straw-colored fruit bats (Eidolon helvum) in Zambia, a total of 107 spleen samples of E. helvum in 2006 were inoculated onto Vero E6 cells. The cell culture inoculated with one of the samples (ZFB06-106) exhibited remarkable cytopathic changes. Based on the ultrastructural property in negative staining and cross-reactivity in immunofluorescence assays, the virus was suspected to be an adenovirus, and tentatively named E. helvum adenovirus 06-106 (EhAdV 06-106). Analysis of the full-length genome of 30,134 bp, determined by next-generation sequencing, showed the presence of 28 open reading frames. Phylogenetic analyses confirmed that EhAdV 06-106 represented a novel bat adenovirus species in the genus Mastadenovirus. The virus shared similar characteristics of low G + C contents with recently isolated members of species Bat mastadenoviruses E, F and G, from which EhAdV 06-106 diverged by more than 15% based on the distance matrix analysis of DNA polymerase amino acid sequences. According to the taxonomic criteria, we propose the tentative new species name “Bat mastadenovirus H”. Because EhAdV 06-106 exhibited a wide in vitro cell tropism, the virus might have a potential risk as an emerging virus through cross-species transmission.

Whole genomic analysis of two potential recombinant strains within Human mastadenovirus species C previously found in Beijing, China

Human mastadenovirus species C (HAdV-C) are the most common etiologic agents of respiratory disease in young children and are frequently detected worldwide including China. Two recombinant HAdV-C strains (BJ04 and BJ09) were isolated from infants with acute respiratory infection (ARI) in Beijing in 2012–2013. The whole genome sequences (WGS) of BJ04 and BJ09 were generated and compared to other 35 HAdV-C WGSs publicly available. Phylogenetic analyses showed that the BJ04 strain might be the result of three homologous recombination events involving the parental strains JX173086 (HAdV-1), NC_001405 (HAdV-2) and LC068718 (HAdV-6), whereas BJ09 viral genome might be made of genetic elements from JX173083 (HAdV-1), KF268199 (HAdV-5), and KR699642 (strain CBJ113). Despite intratypic recombination, amino acid analysis showed that the gene repertoire of BJ04 and BJ09 were similar to type 2 viruses. Finally, this analysis revealed that at least three lineages of HAdV-C have been identified in China, represented by BJ04 related to NC_001405, BJ09 related to CBJ113, and KF951595 (strain DD28) related to virus isolated in Japan. This study showed that the frequent recombination played an important driving force for complexity of the HAdV-C epidemic in Beijing, thereby demonstrating the necessity for epidemiological and virological surveillance for HAdV-C in China.

Advancements in the design and scalable production of viral gene transfer vectors

The last 10 years have seen a rapid expansion in the use of viral gene transfer vectors, with approved therapies and late stage clinical trials underway for the treatment of genetic disorders, and multiple forms of cancer, as well as prevention of infectious diseases through vaccination. With this increased interest and widespread adoption of viral vectors by clinicians and biopharmaceutical industries, there is an imperative to engineer safer and more efficacious vectors, and develop robust, scalable and cost-effective production platforms for industrialization. This review will focus on major innovations in viral vector design and production systems for three of the most widely used viral vectors: Adenovirus, Adeno-Associated Virus, and Lentivirus.

PHYLOGENETIC ANALYSIS OF THE GENOME OF AN ENTERITIS-ASSOCIATED BOTTLENOSE DOLPHIN MASTADENOVIRUS SUPPORTS A CLADE INFECTING THE CETARTIODACTYLA

:  Adenoviruses are nonenveloped, double-stranded DNA viruses, known to infect members of all tetrapod classes, with a similarity between phylogenies of hosts and viruses observed. We characterized bottlenose dolphin adenovirus 2 (BdAdV-2) found in a bottlenose dolphin ( Tursiops truncatus) with enteritis. Virions were seen by negative staining electron microscopy of feces. Initial sequences obtained using conserved PCR primers were expanded using primer walking techniques, and the complete coding sequence was obtained. Phylogenetic analyses were consistent with coevolution of this virus and its bottlenose dolphin host, placing BdAdV-2 into a monophyletic group with other mastadenoviruses of Cetartiodactyla. When considering the low guanine/cytosine (G/C) content of BdAdV-2 with the phylogenetic data, this virus may represent a host-jumping event from another member of Cetartiodactyla. Analysis of partial polymerase indicated that bottlenose dolphin adenovirus 1, previously identified in Spain, and BdAdV-2 are sister taxa with harbor porpoise adenovirus 1, forming a cetacean clade. Bottlenose dolphin adenovirus 2 includes a highly divergent fiber gene. Two genes homologous to the dUTPase superfamily are also present which could play a role in enabling viral replication in nondividing cells. We used sequence data to develop a probe hybridization quantitative PCR assay specific to BdAdV-2 with a limit of detection of 10 copies.

Structure of a Reptilian Adenovirus Reveals a Phage Tailspike Fold Stabilizing a Vertebrate Virus Capsid

Although non-human adenoviruses (AdVs) might offer solutions to problems posed by human AdVs as therapeutic vectors, little is known about their basic biology. In particular, there are no structural studies on the complete virion of any AdV with a non-mammalian host. We combine mass spectrometry, cryo-electron microscopy, and protein crystallography to characterize the composition and structure of a snake AdV (SnAdV-1, Atadenovirus genus). SnAdV-1 particles contain the genus-specific proteins LH3, p32k, and LH2, a previously unrecognized structural component. Remarkably, the cementing protein LH3 has a trimeric β helix fold typical of bacteriophage host attachment proteins. The organization of minor coat proteins differs from that in human AdVs, correlating with higher thermostability in SnAdV-1. These findings add a new piece to the intriguing puzzle of virus evolution, hint at the use of cell entry pathways different from those in human AdVs, and will help development of new, thermostable SnAdV-1-based vectors.

Haemorrhagic enteritis of turkeys - current knowledge

Haemorrhagic enteritis virus (HEV), an adenovirus associated with acute haemorrhagic gastro-intestinal disease of 6-11-week old turkeys predominantly hampers both humoral and cellular immunity. Affected birds are more prone to secondary complications (e.g. colibacillosis and clostridiosis) and failure to mount an effective vaccine-induced immune response. HEV belongs to the new genus Siadenovirus. Feco-oral transmission is the main route of entry of the virus and it mainly colonizes bursa, intestine and spleen. Both naturally occurring virulent and avirulent strains of HEVs are serologically indistinguishable. Recent findings revealed that ORF1, E3 and fib genes are the key factors affecting virulence. The adoption of suitable diagnostic tools, proper vaccination and biosecurity measures have restrained the occurrence of disease epidemics. For diagnostic purposes, the best source of HEV is either intestinal contents or samples from spleen. For rapid detection highly sensitive and specific tests such as quantitative real-time PCR based on Taq man probe has been designed. Avirulent strains of HEV or MSDV can be effectively used as live vaccines. Novel vaccines include recombinant hexon protein-based subunit vaccines or recombinant virus-vectored vaccines using fowl poxvirus (FPV) expressing the native hexon of HEV. Notably, subunit vaccines and recombinant virus vectored vaccines altogether offer high protection against challenge or field viruses. Herein, we converse a comprehensive analysis of the HEV genetics, disease pathobiology, advancements in diagnosis and vaccination along with appropriate prevention and control strategies.

Whole-genome sequences of Odocoileus hemionus deer adenovirus isolates from deer, moose and elk are highly conserved and support a new species in the genus Atadenovirus

We present the first complete genome sequence of Odocoileus hemionus deer adenovirus 1 (OdAdV-1). This virus can cause sporadic haemorrhagic disease in cervids, although epizootics with high mortality have occurred in California. OdAdV-1 has been placed in the genus Atadenovirus, based on partial hexon, pVIII and fibre genes. Ten field isolates recovered from naturally infected mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginiana) and moose (Alces alces) from Wyoming, black-tailed deer (Odocoileus hemionus columbianus) from California, and Rocky Mountain elk (Cervus elaphus nelsoni) from Colorado and Washington state were sequenced. The genome lengths ranged from 30 620 to 30 699 bp, contained the predicted proteins and gene organization typical of members of genus Atadenovirus, and had a high percentage of A/T nucleotides (66.7 %). Phylogenic analysis found that the closest ancestry was with ruminant atadenoviruses, while a divergence of the hexon, polymerase and penton base proteins of more than 15 % supports classification as a new species. Genetic global comparison between the 10 isolates found an overall 99 % identity, but greater divergence was found between those recovered from moose and elk as compared to deer, and a single variable region contained most of these differences. Our findings demonstrate that OdAdV-1 is highly conserved between 10 isolates recovered from multiple related cervid species, but genotypic differences, largely localized to a variable region, define two strains. We propose that the virus type name be changed to cervid adenovirus 1, with the species name Cervid atadenovirus A. Sequence data were used to develop molecular assays for improved detection and genotyping.

Novel adenoviruses detected in British mustelids, including a unique Aviadenovirus in the tissues of pine martens (Martes martes)

Several adenoviruses are known to cause severe disease in veterinary species. Recent evidence suggests that canine adenovirus type 1 (CAV-1) persists in the tissues of healthy red foxes (Vulpes vulpes), which may be a source of infection for susceptible species. It was hypothesized that mustelids native to the UK, including pine martens (Martes martes) and Eurasian otters (Lutra lutra), may also be persistently infected with adenoviruses. Based on high-throughput sequencing and additional Sanger sequencing, a novel Aviadenovirus, tentatively named marten adenovirus type 1 (MAdV-1), was detected in pine marten tissues. The detection of an Aviadenovirus in mammalian tissue has not been reported previously. Two mastadenoviruses, tentatively designated marten adenovirus type 2 (MAdV-2) and lutrine adenovirus type 1 (LAdV-1), were also detected in tissues of pine martens and Eurasian otters, respectively. Apparently healthy free-ranging animals may be infected with uncharacterized adenoviruses with possible implications for translocation of wildlife.

Getting genetic access to natural adenovirus genomes to explore vector diversity

Recombinant vectors based on the human adenovirus type 5 (HAdV5) have been developed and extensively used in preclinical and clinical studies for over 30 years. However, certain restrictions of HAdV5-based vectors have limited their clinical applications because they are rather inefficient in specifically transducing cells of therapeutic interest that lack the coxsackievirus and adenovirus receptor (CAR). Moreover, enhanced vector-associated toxicity and widespread preexisting immunity have been shown to significantly hamper the effectiveness of HAdV-5-mediated gene transfer. However, evolution of adenoviruses in the natural host is driving the generation of novel types with altered virulence, enhanced transmission, and altered tissue tropism. As a consequence, an increasing number of alternative adenovirus types were identified, which may represent a valuable resource for the development of novel vector types. Thus, researchers are focusing on the other naturally occurring adenovirus types, which are structurally similar but functionally different from HAdV5. To this end, several strategies have been devised for getting genetic access to adenovirus genomes, resulting in a new panel of adenoviral vectors. Importantly, these vectors were shown to have a host range different from HAdV5 and to escape the anti-HAdV5 immune response, thus underlining the great potential of this approach. In summary, this review provides a state-of-the-art overview of one essential step in adenoviral vector development.

Seroprevalence of neutralizing antibodies against adenovirus type 14 and 55 in healthy adults in Southern China

Re-emerging human adenovirus types 14 (Ad14) and 55 (Ad55) have caused severe respiratory diseases and even deaths during recent outbreaks. However, the seroprevalence of neutralizing antibodies (nAbs) in healthy adults, which may reflect previous circulation and help to predict potential outbreaks, remains unclear. In this study, we established micro-neutralizing (MN) assays on the basis of recombinant Ad14 and Ad55 reporter viruses, and we investigated serum nAbs in healthy blood donors from Southern China. We found that the overall seropositive rates were 24.8% and 22.4% for Ad14 and Ad55 nAbs, respectively. The seropositive rates were low in individuals younger than 20, and they gradually increased with age. Ad55-seropositive individuals tended to have high nAb titers (>1000), while low (72–200) and moderate (201–1000) nAb levels were frequently observed in Ad14-seropositive ones. Surprisingly, the seropositive rates and nAb levels were associated with the blood type but not the gender of the blood donors, with type AB individuals displaying higher seropositive rates and nAb levels. Interestingly, a significant positive correlation was observed between Ad14 and Ad55 seroprevalence, and higher titers of nAbs were detected in double-positive individuals compared to single-positive ones. These results clarified the human humoral immune responses against Ad14 and Ad55 and revealed a low level of herd immunity in some subpopulations, which emphasized the importance of monitoring these two highly virulent adenoviruses and reinforced the development of prophylactic vaccines.

Adenovirus-Mediated Gene Delivery: Potential Applications for Gene and Cell-Based Therapies in the New Era of Personalized Medicine

With rapid advances in understanding molecular pathogenesis of human diseases in the era of genome sciences and systems biology, it is anticipated that increasing numbers of therapeutic genes or targets will become available for targeted therapies. Despite numerous setbacks, efficacious gene and/or cell-based therapies still hold the great promise to revolutionize the clinical management of human diseases. It is wildly recognized that poor gene delivery is the limiting factor for most in vivo gene therapies. There has been a long-lasting interest in using viral vectors, especially adenoviral vectors, to deliver therapeutic genes for the past two decades. Among all currently available viral vectors, adenovirus is the most efficient gene delivery system in a broad range of cell and tissue types. The applications of adenoviral vectors in gene delivery have greatly increased in number and efficiency since their initial development. In fact, among over 2,000 gene therapy clinical trials approved worldwide since 1989, a significant portion of the trials have utilized adenoviral vectors. This review aims to provide a comprehensive overview on the characteristics of adenoviral vectors, including adenoviral biology, approaches to engineering adenoviral vectors, and their applications in clinical and pre-clinical studies with an emphasis in the areas of cancer treatment, vaccination and regenerative medicine. Current challenges and future directions regarding the use of adenoviral vectors are also discussed. It is expected that the continued improvements in adenoviral vectors should provide great opportunities for cell and gene therapies to live up to its enormous potential in personalized medicine.

Phylogenomic analysis of the complete sequence of a gastroenteritis-associated cetacean adenovirus (bottlenose dolphin adenovirus 1) reveals a high degree of genetic divergence

Adenoviruses are common pathogens in vertebrates, infecting a wide range of hosts, but only having rarely been detected and correlated with disease in cetaceans. This article describes the first complete genomic sequence of a cetacean adenovirus, bottlenose dolphin adenovirus 1 (BdAdV-1), detected in captive bottlenose dolphin population (Tursiops truncatus) suffering from self-limiting gastroenteritis. The complete genome sequence of BdAdV-1 was recovered from data generated by high-throughput sequencing and validated by Sanger sequencing. The genome is 34,080bp long and has 220 nucleotides long inverted terminal repeats. A total of 29 coding sequences were identified, 26 of which were functionally annotated. Among the unusual features of this genome is a remarkably long 4380bp E3 ORF1, that displays no sequence homology with the corresponding E3 regions of other adenoviruses. In addition, the fiber protein only has 26% identity with fiber proteins described in other adenoviruses. Three hypothetical proteins were predicted. The phylogenetic analysis indicates that the closest known relative to BdAdV-1 is an adenovirus detected in bottlenose dolphin (KR024710), with an amino acid sequence identity between 36 and 79% depending on the protein. Based on the phylogenic analysis, the BdAdV-1 appears to have co-evolved with its host. The results indicate that BdAdV-1 belongs to the Mastadenovirus genus of the Adenoviridae family, however, it is clearly different from other adenoviruses, especially in the 3'-end of the viral genome. The high degree of sequence divergence suggests that BdAdV-1 should be considered as a novel species in the Mastadenovirus genus. The study also demonstrates the usefulness of high-throughput sequencing to obtain full-length genomes of genetically divergent viruses.

Cryo-EM structure of human adenovirus D26 reveals the conservation of structural organization among human adenoviruses

Human adenoviruses (HAdVs) cause acute respiratory, ocular, and gastroenteric diseases and are also frequently used as gene and vaccine delivery vectors. Unlike the archetype human adenovirus C5 (HAdV-C5), human adenovirus D26 (HAdV-D26) belongs to species-D HAdVs, which target different cellular receptors, and is differentially recognized by immune surveillance mechanisms. HAdV-D26 is being championed as a lower seroprevalent vaccine and oncolytic vector in preclinical and human clinical studies. To understand the molecular basis for their distinct biological properties and independently validate the structures of minor proteins, we determined the first structure of species-D HAdV at 3.7 Å resolution by cryo-electron microscopy. All the hexon hypervariable regions (HVRs), including HVR1, have been identified and exhibit a distinct organization compared to those of HAdV-C5. Despite the differences in the arrangement of helices in the coiled-coil structures, protein IX molecules form a continuous hexagonal network on the capsid exterior. In addition to the structurally conserved region (3 to 300) of IIIa, we identified an extra helical domain comprising residues 314 to 390 that further stabilizes the vertex region. Multiple (two to three) copies of the cleaved amino-terminal fragment of protein VI (pVIn) are observed in each hexon cavity, suggesting that there could be ≥480 copies of VI present in HAdV-D26. In addition, a localized asymmetric reconstruction of the vertex region provides new details of the three-pronged "claw hold" of the trimeric fiber and its interactions with the penton base. These observations resolve the previous conflicting assignments of the minor proteins and suggest the likely conservation of their organization across different HAdVs.

A Novel Recombinant Canine Adenovirus Type 1 Detected from Acute Lethal Cases of Infectious Canine Hepatitis

In this study, canine adenoviruses (CAdVs) from two acute fatal cases of infectious canine hepatitis (ICH) were analyzed using molecular detection and sequencing of the pVIII, E3, and fiber protein genes. Pathological findings in affected dogs were typical for CAdV-1 associated disease, characterized by severe centrilobular to panlobular necrohemorrhagic hepatitis and the development of disseminated intravascular coagulation in the terminal stages of disease. Comparison of partial genome sequences revealed that although these newly detected viruses mainly had CAdV-1 genome characteristics, their pVIII gene was more similar to that of CAdV-2. This likely suggests that a recombination has occurred between CAdV-1 and CAdV-2, which possibly explains the cause of vaccine failure or increased virulence of the virus in the observed ICH cases.

Fowl adenovirus: history, emergence, biology and development of a vaccine against hydropericardium syndrome

The poultry industry has emerged as one of the largest and fastest growing public sectors in the developed and developing countries. Unfortunately, this industry is under a major threat from diseases that are viral (Newcastle disease, infectious bursal disease, influenza, hydropericardium syndrome), bacterial (colibacillosis, pasteurellosis, salmonellosis, mycoplasmosis), parasitic (coccidiosis, histoplasmosis) or nutritional (dyschondroplasia, osteoporosis). Among these diseases, hydropericardium syndrome (HPS) is one of the important emerging diseases occurring in the specific areas of the world where broilers (chickens) are reared under intensive conditions. HPS was first observed in 1987 at Angara Goth, an area near Karachi, Pakistan, where broilers are raised. Since then, HPS has been reported in many countries of the world. From these reported cases, an adenovirus that was either isolated from or visualized electron microscopically in the liver of affected broilers has been implicated in the syndrome. The syndrome has been reproduced by inoculation of isolated fowl adenovirus (FAdV) strains, and hence, the syndrome is also called infectious hydropericardium syndrome. To our knowledge, HPS has not been observed in humans, so it is not considered a zoonotic disease, but it is of economic importance and causes huge losses to the poultry industry. Efforts have been made to develop conventional vaccines against this disease, which were formulated from infected liver homogenate. Formalin-inactivated liver organ vaccines have failed to protect the poultry industry. Hence, there is a dire need to develop a suitable vaccine to combat this disease. Currently, recombinant vaccine candidates are being developed by using molecular biology and biotechnological approaches for the prevention and control of infectious diseases, including HPS. Therefore, it is suggested that the immunogenicity of these recombinant proteins should be evaluated for their use as subunit vaccines.

The tripartite leader sequence is required for ectopic expression of HAdV-B and HAdV-E E3 CR1 genes

The unique repertoire of genes that characterizes the early region 3 (E3) of the different species of human adenovirus (HAdV) likely contributes to their distinct pathogenic traits. The function of many E3 CR1 proteins remains unknown possibly due to unidentified intrinsic properties that make them difficult to express ectopically. This study shows that the species HAdV-B- and HAdV-E-specific E3 CR1 genes can be expressed from vectors carrying the HAdV tripartite leader (TPL) sequence but not from traditional mammalian expression vectors. Insertion of the TPL sequence upstream of the HAdV-B and HAdV-E E3 CR1 open reading frames was sufficient to rescue protein expression from pCI-neo constructs in transfected 293T cells. The detection of higher levels of HAdV-B and HAdV-E E3 CR1 transcripts suggests that the TPL sequence may enhance gene expression at both the transcriptional and translational levels. Our findings will facilitate the characterization of additional AdV E3 proteins.

Adenoviral Vectors Armed with Cell Fusion-Inducing Proteins as Anti-Cancer Agents

Cancer is a devastating disease that affects millions of patients every year, and causes an enormous economic burden on the health care system and emotional burden on affected families. The first line of defense against solid tumors is usually extraction of the tumor, when possible, by surgical methods. In cases where solid tumors can not be safely removed, chemotherapy is often the first line of treatment. As metastatic cancers often become vigorously resistant to treatments, the development of novel, more potent and selective anti-cancer strategies is of great importance. Adenovirus (Ad) is the most commonly used virus in cancer clinical trials, however, regardless of the nature of the Ad-based therapeutic, complete responses to treatment remain rare. A number of pre-clinical studies have shown that, for all vector systems, viral spread throughout the tumor mass can be a major limiting factor for complete tumor elimination. By expressing exogenous cell-fusion proteins, many groups have shown improved spread of Ad-based vectors. This review summarizes the research done to examine the potency of Ad vectors expressing fusogenic proteins as anti-cancer therapeutics.

Suppression of Adenovirus Replication by Cardiotonic Steroids

The dependence of adenovirus on the host pre-RNA splicing machinery for expression of its complete genome potentially makes it vulnerable to modulators of RNA splicing, such as digoxin and digitoxin. Both drugs reduced the yields of four human adenoviruses (HAdV-A31, -B35, and -C5 and a species D conjunctivitis isolate) by at least 2 to 3 logs by affecting one or more steps needed for genome replication. Immediate early E1A protein levels are unaffected by the drugs, but synthesis of the delayed protein E4orf6 and the major late capsid protein hexon is compromised. Quantitative reverse transcription-PCR (qRT-PCR) analyses revealed that both drugs altered E1A RNA splicing (favoring the production of 13S over 12S RNA) early in infection and partially blocked the transition from 12S and 13S to 9S RNA at late stages of virus replication. Expression of multiple late viral protein mRNAs was lost in the presence of either drug, consistent with the observed block in viral DNA replication. The antiviral effect was dependent on the continued presence of the drug and was rapidly reversible. RIDK34, a derivative of convallotoxin, although having more potent antiviral activity, did not show an improved selectivity index. All three drugs reduced metabolic activity to some degree without evidence of cell death. By blocking adenovirus replication at one or more steps beyond the onset of E1A expression and prior to genome replication, digoxin and digitoxin show potential as antiviral agents for treatment of serious adenovirus infections. Furthermore, understanding the mechanism(s) by which digoxin and digitoxin inhibit adenovirus replication will guide the development of novel antiviral therapies.

IMPORTANCE

Despite human adenoviruses being a common and, in some instances, life-threating pathogen in humans, there are few well-tolerated therapies. In this report, we demonstrate that two cardiotonic steroids already in use in humans, digoxin and digitoxin, are potent inhibitors of multiple adenovirus species. A synthetic derivative of the cardiotonic steroid convallotoxin was even more potent than digoxin and digitoxin when tested with HAdV-C5. These drugs alter the cascade of adenovirus gene expression, acting after initiation of early gene expression to block viral DNA replication and synthesis of viral structural proteins. These findings validate a novel approach to treating adenovirus infections through the modulation of host cell processes.

A novel pathogenic aviadenovirus from red-bellied parrots (Poicephalus rufiventris) unveils deep recombination events among avian host lineages

Competing roles of coevolution, selective pressure and recombination are an emerging interest in virus evolution. We report a novel aviadenovirus from captive red-bellied parrots (Poicephalus rufiventris) that uncovers evidence of deep recombination among aviadenoviruses. The sequence identity of the virus was most closely related to Turkey adenovirus D (42% similarity) and other adenoviruses in chickens, turkeys and pigeons. Sequencing and comparative analysis showed that the genome comprised 40,930 nucleotides containing 42 predicted open reading frames (ORFs) 19 of which had strong similarity with genes from other adenovirus species. The new genome unveiled a lineage that likely participated in deep recombination events across the genus Aviadenovirus accounting for an ancient evolutionary relationship. We hypothesize frequent host switch events and recombination among adenovirus progenitors in Galloanserae hosts caused the radiation of extant aviadenoviruses and the newly assembled Poicephalus adenovirus genome points to a potentially broader host range of these viruses among birds.

Evolution and Cryo-electron Microscopy Capsid Structure of a North American Bat Adenovirus and Its Relationship to Other Mastadenoviruses

Since the first description of adenoviruses in bats in 2006, a number of micro- and megabat species in Europe, Africa, and Asia have been shown to carry a wide diversity of adenoviruses. Here, we report on the evolutionary, biological, and structural characterization of a novel bat adenovirus (BtAdV) recovered from a Rafinesque's big-eared bat (Corynorhinus rafinesquii) in Kentucky, USA, which is the first adenovirus isolated from North American bats. This virus (BtAdV 250-A) exhibits a close phylogenetic relationship with Canine mastadenovirus A (CAdV A), as previously observed with other BtAdVs. To further investigate the relationships between BtAdVs and CAdVs, we conducted mass spectrometric analysis and single-particle cryo-electron microscopy reconstructions of the BtAdV 250-A capsid and also analyzed the in vitro host ranges of both viruses. Our results demonstrate that BtAdV 250-A represents a new mastadenovirus species that, in contrast to CAdV, has a unique capsid morphology that contains more prominent extensions of protein IX and can replicate efficiently in a phylogenetically diverse range of species. These findings, in addition to the recognition that both the genetic diversity of BtAdVs and the number of different bat species from disparate geographic regions infected with BtAdVs appears to be extensive, tentatively suggest that bats may have served as a potential reservoir for the cross-species transfer of adenoviruses to other hosts, as theorized for CAdV.

IMPORTANCE

Although many adenoviruses are host specific and likely codiverged with their hosts over millions of years, other adenoviruses appear to have emerged through successful cross-species transmission events on more recent time scales. The wide geographic distribution and genetic diversity of adenoviruses in bats and their close phylogenetic relationship to Canine mastadenovirus A (CAdV A) has raised important questions about how CAdV A, and possibly other mammalian adenoviruses, may have emerged. Although most adenoviruses tend to cause limited disease in their natural hosts, CAdV A is unusual in that it may cause high morbidity and sometimes fatal infections in immunocompetent hosts and is thus an important pathogen of carnivores. Here, we performed a comparative evolutionary and structural study of representative bat and canine adenoviruses to better understand the relationship between these two viral groups.

Metformin Is Associated With Higher Relative Abundance of Mucin-Degrading Akkermansia muciniphila and Several Short-Chain Fatty Acid-Producing Microbiota in the Gut

The global obesity epidemic, dubbed “globesity” by the World Health Organisation, is a pressing public health issue. The aetiology of obesity is multifactorial incorporating both genetic and environmental factors. Recently, epidemiological studies have observed an association between microbes and obesity. Obesity-promoting microbiome and resultant gut barrier disintegration have been implicated as key factors facilitating metabolic endotoxaemia. This is an influx of bacterial endotoxins into the systemic circulation, believed to underpin obesity pathogenesis. Adipocyte dysfunction and subsequent adipokine secretion characterised by low grade inflammation, were conventionally attributed to persistent hyperlipidaemia. They were thought of as pivotal in perpetuating obesity. It is now debated whether infection and endotoxaemia are also implicated in initiating and perpetuating low grade inflammation. The fact that obesity has a prevalence of over 600 million and serves as a risk factor for chronic diseases including cardiovascular disease and type 2 diabetes mellitus is testament to the importance of exploring the role of microbes in obesity pathobiology. It is on this basis that Massachusetts General Hospital is sponsoring the Faecal Microbiota Transplant for Obesity and Metabolism clinical trial, to study the impact of microbiome composition on weight. The association of microbes with obesity, namely, adenovirus infection and metabolic endotoxaemia, is reviewed.

Oral vaccination of fish: Lessons from humans and veterinary species

The limited number of oral vaccines currently approved for use in humans and veterinary species clearly illustrates that development of efficacious and safe oral vaccines has been a challenge not only for fish immunologists. The insufficient efficacy of oral vaccines is partly due to antigen breakdown in the harsh gastric environment, but also to the high tolerogenic gut environment and to inadequate vaccine design. In this review we discuss current approaches used to develop oral vaccines for mass vaccination of farmed fish species. Furthermore, using various examples from the human and veterinary vaccine development, we propose additional approaches to fish vaccine design also considering recent advances in fish mucosal immunology and novel molecular tools. Finally, we discuss the pros and cons of using the zebrafish as a pre-screening animal model to potentially speed up vaccine design and testing for aquaculture fish species.