CANINE ADENOVIRUS TYPE 1 IN A FENNEC FOX ( VULPES ZERDA )

Canine Adenoviruses in Wildlife: Role in At-Risk Species Conservation and Interface with Domestic Animals

Canine adenovirus type 1 (CAdV-1) and type 2 (CAdV-2) are well known pathogens of domestic dogs but are little investigated in wild animals. The few available studies about CAdV-1 in wild animals show that it circulates in various species and that transmission of the virus in the interface between wildlife and domestic animals is a frequent event. Furthermore, wild animals are usually subject to asymptomatic infections, but cases of serious and fatal diseases have been documented, with possible effects on the conservation of the species. In contrast, CAdV-2 infection was reported only recently and sporadically in some wild animals, with few data regarding its pathogenic role in these species. However, the real prevalence of these viruses in wildlife is still uncertain due to the use of serological tests that are largely unable to distinguish antibodies against CAdV-1 and CAdV-2. This review, reporting all the data currently available on CAdV-1 and CAdV-2 infection in wild animals, highlights the importance of these pathogens for wildlife conservation and their role in the potential transmission of the infection to domestic dogs.

Immunogenicity of a novel inactivated canine adenovirus type 2 variant vaccine for dogs

Purpose

The immunogenicity of vaccines containing the canine adenovirus (CAdV) type 2 (CAdV-2) variant has not yet been reported. We prepared a novel inactivated CAdV-2 variant vaccine using the CAV2232-41 strain, and evaluated its safety and immunogenicity in raccoon dogs.

Materials and Methods

The growth kinetics of CAV2232-41 were determined using Madin-Darby Canine Kidney (MDCK) cells. The nucleotide sequences of CAV2232 and CAV2232-41 were determined by next-generation sequencing. To generate the CAdV-2 variant vaccine, CAV2232-41 propagated in the MDCK cells was inactivated with 0.1% formaldehyde. Two vaccines were prepared by blending inactivated CAV2232-41 with Cabopol and Rehydragel adjuvants. Safety and immunogenicity of the CAV2232C and CAV2232R vaccines were evaluated in guinea pigs. Safety and immunogenicity of the CAV2232C vaccine were also evaluated in raccoon dogs. The virus neutralizing antibody (VNA) titer against CAV2232-41 was measured in sera collected from immunized guinea pigs and raccoon dogs.

Results

CAV2232-41 showed the highest viral titer on days 4-6 post-inoculation and had a deletion in the E3 gene, which was confirmed as a CAdV-2 variant. Guinea pigs inoculated with CAV2232C showed slightly higher VNA titers than those inoculated with CAV2232R 2 weeks after booster vaccination. Raccoon dogs immunized with the CAV2232C vaccine developed high mean VNA titers, while non-vaccinated raccoon dogs were antibody-negative.

Conclusion

The CAV2232C vaccine is safe and induces a protective VNA titer in raccoon dogs.

Canine distemper virus and canine adenovirus type 1 co-infection in a free-living hoary fox (Lycalopex vetulus) from Brazil

The present case is the first description of a co-infection with canine distemper virus (CDV) and canine adenovirus type 1 (CAdV-1) in a free-living hoary fox pup from Brazil. The animal was found and rescued with poor body condition, dehydration, incoordination, ataxia, excessive vocalization, and "blue eyes" phenomenon. Despite the efforts, euthanasia was elected due to worsening clinical signs and poor prognosis. Pathologic examination revealed a mild, acute, random, necrotizing hepatitis, acute bronchopneumonia, hydrocephalus, corneal edema with epithelium degeneration, and acidophilic intracytoplasmatic inclusion bodies in different epithelial cells types with rare syncytial. Through immunohistochemistry, CDV antigen was observed in the tongue, trachea, lungs, liver, spleen, stomach, intestine and urinary bladder. Adenovirus antigen was identified in the nucleus of scattered hepatocytes. Polymerase chain reaction and sequencing demonstrated high similarity with CAdV-1 and wild-type strain of CDV close related to Brazilian viral lineages isolated from domestic dogs. Disease surveillance in wildlife animals is essential to assess possible conservation threats and consider the implementation of mitigation or control measures.

Canine Adenovirus 1 Isolation Bioinformatics Analysis of the Fiber

Canine adenovirus type 1 (CAdV-1) is a double-stranded DNA virus, which is the causative agent of fox encephalitis. The Fiber protein is one of the structural proteins in CAdV-1, which mediates virion binding to the coxsackievirus and adenovirus receptor on host cells. The suspected virus was cultured in the MDCK cells, and it was determined through the cytopathic effects, sequencing and electron microscopy. The informatics analysis of the Fiber was done using online bioinformatics servers. The CAdV-1-JL2021 strain was isolated successfully, and were most similar to the CAdV-1 strain circulating in Italy. The occurrence of negative selection and recombination were found in the CAdV-1-JL2021 and CAdV-2-AC_000020.1. Host cell membrane was its subcellular localization. The CAdV-1-JL2021 Fiber (ON164651) had 6 glycosylation sites and 107 phosphorylation sites, exerted adhesion receptor-mediated virion attachment to host cell, which was the same as CAdV-2-AC_000020.1 Fiber. The Fiber tertiary structure of the CAdV-1-JL2021 and CAdV-2-AC_000020.1 was different, but they had the same coxsackievirus and adenovirus receptor. “VATTSPTLTFAYPLIKNNNH” were predicted to be the potential CAdV-1 B cell linear epitope. The MHC-I binding peptide “KLGVKPTTY” were both presented in the CAdV-1-JL2021 and CAdV-2-AC_000020.1 Fiber and it is useful to design the canine adenovirus vaccine.

Difference Analysis Between Canine Adenovirus Types 1 And 2

Canine adenoviruses (CAdVs) include type 1 (CAdV-1, virulent strain) and type 2 (CAdV-2, attenuated strain). In recent years, the incidences of CAdV infections are increasing. However, they are difficult to distinguish when the symptoms are untypical. It is pivotal to find the differences between the two virus types for scientific, epidemiological, and specific treatment. CAdV-1 (virulent strain) and CAdV-2 (attenuated strain) induced canine hepatitis (ICH) and tracheobronchitis (ITB), respectively, but the clinical symptom is not obvious. CAdV-1 and CAdV-2 have the same genome structure, diameter, morphological features, and cytopathic features, but the same character hinder the diagnose time of the serotypes. CAdV-1 and CAdV-2 have a difference in the genome sequence, coding proteins, viral activity, hemagglutination patterns. After infection, pathogenicity and transmission route are different between the two serotypes. Sequence alignment, PCR, Real time-PCR assay are useful methods to distinguish the two serotypes. The attenuated live CAdV-2 vaccine is currently used to protect against CAdV-1, but it also has a risk. The further research should focus on the pathogenicity mechanism and the useful vaccine for the two serotypes of canine adenovirus.

Immunogenicity of an Inactivated Canine Adenovirus Type 1 Vaccine for Foxes

Canine adenovirus type 1 (CAdV-1) is the etiologic agent of fox encephalitis. As with most viral agents, the best method of prevention is vaccination. In this study, the CAdV-1 strain F1301 strain was used to construct a new type 1 canine adenovirus inactivated vaccine candidate, and its safety and immunogenicity were evaluated in silver foxes. Next, animals were challenged and survival rates of animals vaccinated with either the commercially available or the current candidate vaccine were examined. The results confirmed that the inactivated CAdV-1 vaccine prepared in this study can effectively protect against challenge with virulent CAdV-1 in silver foxes, and the safety profile was improved relative to that of the commercial vaccine. This study confirmed that the fox CAdV-1 F1301 strain can be used as a platform for an inactivated CAdV-1 vaccine.

Naturally Acquired Infectious Canine Hepatitis in Two Captive Maned Wolf (Chrysocyon brachyurus) Puppies

We report the clinicopathological manifestations of canine adenovirus type 1 (CAV 1) infection in captive-born naturally infected maned wolves (Chrysocyon brachyurus). Two 3-month-old maned wolves presented with lethargy, emesis, dehydration, pallor, hypothermia, leucocytosis, neutrophilia, lymphopaenia and thrombocytopaenia. One of the puppies died shortly after admission, with gross changes that included marked gastrointestinal petechiae, splenomegaly, hepatomegaly and pulmonary haemorrhage. Histologically, large eosinophilic intranuclear body inclusions were found in the liver and kidneys. The other wolf had elevated alkaline phosphatase, alanine aminotransferase and creatine kinase activities, and later developed anaemia, hypoalbuminaemia, bilirubinaemia, bilirubinuria, haematuria and proteinuria. Ultrasound demonstrated hepatomegaly, splenomegaly, inguinal lymphadenomegaly and lesions suggestive of gastritis and enteritis. Despite supportive treatment, the animal died. At necropsy, there was icterus, subcutaneous oedema in the inguinal region and hindlimbs, subchondral haemorrhage of articular cartilage of the femoral-tibial-patellar and tarsal joints of both hindlimbs, lymphadenomegaly, bronchopneumonia, hepatomegaly and petechiae in the gastrointestinal mucosa. Microscopically, there was a severe necrotizing hepatitis with intranuclear viral inclusions, fibrinous-necrotizing splenitis, non-suppurative meningoencephalitis and interstitial nephritis. A quantitative PCR test for CAV 1 using DNA extracted from peripheral blood was positive. The clinicopathological findings are similar to those of CAV 1 infection in dogs and other canids.

The biological characteristics of the canine adenovirus type 1 from fox and the transcriptome analysis of the infected MDCK cell

Canine adenovirus type 1 (CAdV-1) is the etiologic agent of fox encephalitis, and a virus strain from fox encephalitis is isolated and related research are conducted. In this experiment, the results showed that the F1301 strain was confirmed to be the CAdV-1. The whole genome of the CAdV-1 F1301 strain isolated from fox was 30,535 bp and had higher homology to the other reported CAdV-1 strains. After 0, 12, and 36 h of CAdV-1 infection, the difference gene of the 592 long noncoding RNA and 11,215 microRNA were involved in cell responses to CAdV-1 infection through the PI3K-AKT, Wnt, Herpes simplex, hepatitis C, and Epstein-Barr virus infection pathway in Madin-Darby canine kidney cell line (MDCK). The results indicate that the biological characterization of the CAdV-1 and the MDCK cell-CAdV-1 interaction are clarified.

Molecular evidence for vaccine-induced canine distemper virus and canine adenovirus 2 coinfection in a fennec fox

A 61-d-old fennec fox (Vulpes zerda), 11 d after receiving a multivalent, modified-live virus vaccine containing canine distemper virus (CDV), canine adenovirus 2 (CAdV-2), parainfluenza virus, parvovirus, and canine coronavirus, developed oculonasal discharge, and subsequently convulsions, and hemoptysis, and died. Microscopic changes in the cerebrum were evident, including neuronal degeneration and necrosis; intracytoplasmic eosinophilic inclusion bodies were observed in astrocytes. CDV was detected in the brain tissue by immunohistochemistry. Pulmonary lesions of multifocal necrotizing bronchopneumonia had Cowdry type A intranuclear inclusions in the bronchial epithelial cells. Electron microscopy revealed crystalline arrays of adenovirus-like particles within the intranuclear inclusions. Additionally, the hemagglutinin gene of CDV and the CAdV-2 DNA polymerase gene were detected in the fennec fox; sequence analysis showed 100% identity with those of the vaccine strain viruses. To our knowledge, vaccine-induced CDV and CAdV-2 coinfections using molecular analysis have not been reported previously. Therefore, vaccine strains should be considered prior to CDV vaccination in nondomestic carnivores.

Immunogenicity of a new, inactivated canine adenovirus type 2 vaccine for dogs

PURPOSE

We constructed a new canine adenovirus type 2 (CAV-2) vaccine candidate using the recently isolated Korean CAV-2 strain; we termed the vaccine APQA1701-40P and evaluated its safety and immunogenicity in dogs.

MATERIALS AND METHODS

To generate the anti-CAV-2 vaccine, APQA1701 was passaged 40 times in MDCK cells growing in medium containing 5 mM urea and the virus was inactivated using 0.05% (volume per volume) formaldehyde. Two vaccines were prepared by blending inactivated APQA1701-40P with two different adjuvants; both were intramuscularly injected (twice) into guinea pigs. The safety and immunogenicity of the Cabopol-adjuvanted vaccine were evaluated in seronegative dogs. The humoral responses elicited were measured using an indirect enzyme-linked immunosorbent assay (I-ELISA), and via a virus neutralization assay (VNA).

RESULTS

The new, inactivated CAV-2 vaccine strain, APQA1701-40P, lacked six amino acids of the E1b-19K protein. In guinea pigs, the Cabopol-adjuvanted vaccine afforded a slightly higher VNA titer and I-ELISA absorbance than an IMS gel-adjuvanted vaccine 4 weeks post-vaccination (p>0.05). Dogs inoculated with the former vaccine developed a significantly higher immune titer than non-vaccinated dogs.

CONCLUSION

The Cabopol-adjuvanted, inactivated CAV-2 vaccine was safe and induced a high VNA titer in dogs.

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.

Detection of canine adenovirus 1 in red foxes (Vulpes vulpes) and raccoons (Procyon lotor) in Germany with a TaqMan real-time PCR assay

We developed a real-time (rt)PCR assay based on TaqMan probe technology for the specific detection of canine adenovirus 1 (CAdV-1). The assay is able to detect three 50% tissue culture infectious dose/mL in CAdV-1–containing cell culture supernatant. Viral genomes were not amplified of canine adenovirus 2 or of several bovine, porcine, and avian adenoviruses. In silico analysis provided no indication of amplification of other heterologous genomes. The sensitivity of the real-time assay exceeded that of a conventional gel-based CAdV-1 PCR by a factor of 100. Following the integration of the novel PCR into the Hessian wildlife-monitoring program, CAdV-1 DNA was detected in none of the tested raccoons ( n = 48) but in 11 of 97 foxes.

ENDEMIC INFECTION OF STRANDED SOUTHERN SEA OTTERS (ENHYDRA LUTRIS NEREIS) WITH NOVEL PARVOVIRUS, POLYOMAVIRUS, AND ADENOVIRUS

Over the past century, the southern sea otter (SSO; Enhydra lutris nereis) population has been slowly recovering from near extinction due to overharvest. The SSO is a threatened subspecies under federal law and a fully protected species under California law, US. Through a multiagency collaborative program, stranded animals are rehabilitated and released, while deceased animals are necropsied and tissues are cryopreserved to facilitate scientific study. Here, we processed archival tissues to enrich particle-associated viral nucleic acids, which we randomly amplified and deeply sequenced to identify viral genomes through sequence similarities. Anelloviruses and endogenous retroviral sequences made up over 50% of observed viral sequences. Polyomavirus, parvovirus, and adenovirus sequences made up most of the remaining reads. We characterized and phylogenetically analyzed the full genome of sea otter polyomavirus 1 and the complete coding sequence of sea otter parvovirus 1 and found that the closest known viruses infect primates and domestic pigs ( Sus scrofa domesticus), respectively. We tested archived tissues from 69 stranded SSO necropsied over 14 yr (2000-13) by PCR. Polyomavirus, parvovirus, and adenovirus infections were detected in 51, 61, and 29% of examined animals, respectively, with no significant increase in frequency over time, suggesting endemic infection. We found that 80% of tested SSO were infected with at least one of the three DNA viruses, whose tissue distribution we determined in 261 tissue samples. Parvovirus DNA was most frequently detected in mesenteric lymph node, polyomavirus DNA in spleen, and adenovirus DNA in multiple tissues (spleen, retropharyngeal and mesenteric lymph node, lung, and liver). This study describes the virome in tissues of a threatened species and shows that stranded SSO are frequently infected with multiple viruses, warranting future research to investigate associations between these infections and observed lesions.

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.

A duplex real-time PCR assay based on TaqMan technology for simultaneous detection and differentiation of canine adenovirus types 1 and 2

Canine adenoviruses are a major cause of disease in dogs, coyotes, red foxes and wolves, as well as in other carnivores and marine mammals. Canine adenovirus type 1 (CAdV-1) and canine adenovirus type 2 (CAdV-2) cause infectious canine hepatitis (ICH) and infectious tracheobronchitis (ITB), respectively. In this study, a duplex real-time PCR assay for simultaneous detection and characterisation of CAdV-1 and CAdV-2 was developed by using a single primer pair and virus-specific probes. The assay was validated testing standard DNAs produced on purpose and clinical samples of various matrices known to be positive for CAdV-1, CAdV-2 or both viruses. Precise calculation of DNA loads in samples containing a wide range of viral amounts was allowed by generating a standard curve for absolute quantification. The assay was proven to be highly specific, since no cross-reactions with the different CAdV type was observed, and sensitive, being able to detect less than 10 copies of CAdV-1/CAdV-2 DNA. The low intra-assay and interassay coefficient of variations demonstrated a high repeatability, thus confirming the potential use of this assay for quantitative detection of CAdV-1 and CAdV-2 for rapid diagnosis and epidemiological investigations.