Difference Analysis Between Canine Adenovirus Types 1 And 2

The PB subunit vaccine evokes immune response against fox encephalitis

Canine adenovirus type 1 (CAdV-1) is an important pathogen for fox encephalitis, and posing a severe threat to the global fox farming industry. Although live CAdV-2 vaccines are currently available, its defect remains a considerable challenge. It is vital to develop a safe subunit vaccine. This study aimed to evaluate the immunogenicity and safety of the penton base (PB) subunit vaccine in fox with CAdV-1, for which little is known. Bioinformatics methods were used to design a recombinant protein vaccine based on conserved regions of protein consensus sequences in PB protein. The E.coli prokaryotic expression system was utilized to enhance protein expression, solubility and immunogenicity. After the PB proteins of CAdV-1 were successfully expressed, the mice and silver foxes were immunized. The specific antibody, neutralizing antibody titters, T lymphocyte proliferation, cytokine, tissue histopathology, virus shedding, and the survival rate were investigated. The results showed that the PB subunit vaccine induced the production of antibodies in mice at 7, 14, 21, 30, 60 d post-vaccination (dpv). Moreover, the neutralizing antibody level of the PB group was higher than that in the Knob group at 21 and 28 dpv. It indicates that PB subunit vaccine elicits immunity. In the silver fox, PB subunit vaccine induced the production of antibodies at 30 dpv. Moreover, the neutralizing antibody level in PB group was higher than that in the CAdV-2 vaccine group at 30 dpv. PB subunit vaccine conferred complete protection in fox against CAdV-1. The tissue histopathology suggested that the PB subunit vaccine was more effective in blocking the pathogenicity of CAdV-1. In addition, the PB subunit vaccine further reduced the virus shedding in silver foxes than the CAdV-2 vaccine. The results suggest that this vaccine could be a promising candidate for preventing CAdV-1 in foxes.

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.

Complete Genome Characterization of Canine Adenovirus From Türkiye With Next-Generation Sequencing

BACKGROUND

Determining the complete genome sequence data of adenoviruses has recently become greatly important due to their use by scientists as vectors in cancer studies and other fields, including vaccine development. However, the GenBank database currently has few complete genome sequences of adenoviruses, which are known for their large genomes. To address this gap, we analysed next-generation sequencing data obtained from our previous study to provide the complete genome sequence of the canine adenovirus-2 strain.

METHODS

For the obtained canine adenovirus-2 strain (OQ596341), comparative genomics, recombination and phylogenetic analysis were conducted. This sequence was compared and phylogenetically analysed with the 20 complete genome sequences of canine adenovirus previously reported in GenBank worldwide, as well as partial E3 ORFA sequences obtained from Türkiye.

RESULTS

The nucleotide similarity rates of the sequence obtained from this study with other CAdV-2 whole genomes are over 99.04%. The gene alignment results reveal that the OQ596341 was found to be closely related to the AC000020 reference genome and LC557011. There are two recombination events related to the genome in this study. Comparisons with other complete genome sequences revealed several previously unseen mutations. These mutations include H34Y in the E1A gene; P55A in the E1B 55K gene; D13N and D202N in the IVa2 gene; K679R, V934I and K989N in the Pol gene; E205K in the pTP gene; T455A in the pIIIa gene; A310V in the V gene; G151R in the protease gene; E268K in the 100K gene; G66S and G141S in the 33K gene; T14A, E250K, D287N and I293T in the E3 ORFA gene; and L193F in the E434K gene. Moreover, a comparison with partial sequences obtained from Türkiye revealed the E250K mutation in the E3 ORFA gene, which we report for the first time in Türkiye.

CONCLUSIONS

The complete CAdV-2 genome sequence obtained in the present study is the first sequence from Europe. Comparative analysis with other genomes revealed some unique mutations. This study is the first to report the E250K amino acid change in the E3 ORFA gene in Türkiye. We anticipate that this data can be used in future CAdV-2 vaccine development studies. Further studies are recommended to evaluate the impact of these mutations on viral tropism and other host interactions.

Establishment of a Quadruplex RT-qPCR for the Detection of Canine Coronavirus, Canine Respiratory Coronavirus, Canine Adenovirus Type 2, and Canine Norovirus

Canine coronavirus (CCoV), canine respiratory coronavirus (CRCoV), canine adenovirus type 2 (CAV-2), and canine norovirus (CNV) are important pathogens for canine viral gastrointestinal and respiratory diseases. Especially, co-infections with these viruses exacerbate the damages of diseases. In this study, four pairs of primers and probes were designed to specifically amplify the conserved regions of the CCoV M gene, CRCoV N gene, CAV-2 hexon gene, and CNV RdRp gene. After optimizing different reaction conditions, a quadruplex RT-qPCR was established for the detection of CCoV, CRCoV, CAV-2, and CNV. The specificity, sensitivity, and repeatability of the established assay were evaluated. Then, the assay was used to test 1688 clinical samples from pet hospitals in Guangxi province of China during 2022-2024 to validate its clinical applicability. In addition, these samples were also assessed using the reported reference RT-qPCR assays, and the agreements between the developed and reference assays were determined. The results indicated that the quadruplex RT-qPCR could specifically test only CCoV, CRCoV, CAV-2, and CNV, without cross-reaction with other canine viruses. The assay had high sensitivity with limits of detection (LODs) of 1.0 × 102 copies/reaction for CCoV, CRCoV, CAV-2, and CNV. The repeatability was excellent, with intra-assay variability of 0.19-1.31% and inter-assay variability of 0.10-0.88%. The positivity rates of CCoV, CRCoV, CAV-2, and CNV using the developed assay were 8.59% (145/1688), 8.65% (146/1688), 2.84% (48/1688), and 1.30% (22/1688), respectively, while the positivity rates using the reference assays were 8.47% (143/1688), 8.53% (144/1688), 2.78% (47/1688), and 1.24% (21/1688), respectively, with agreements of more than 99.53% between two methods. In conclusion, a quadruplex RT-qPCR with high sensitivity, specificity, and repeatability was developed for rapid, and accurate detection of CCoV, CRCoV, CAV-2, and CNV.

Evaluating the Effects of Viruses on Eastern Indigo Snakes (Drymarchon couperi) with Gastric Cryptosporidiosis

A breeding colony of wild-origin eastern indigo snakes (EISs, Drymarchon couperi) that is part of a reintroduction program has been impacted by gastric cryptosporidiosis. Gastric cryptosporidiosis is an insidious disease of squamates caused by an apicomplexan protozoan, Cryptosporidium serpentis. Viral coinfections have been implicated as possible immunosuppressant agents that allow for disease progression and both adenovirus and reovirus have been implicated in allowing for the progression of gastric cryptosporidiosis during coinfection in other snake species. Molecular (PCR) screening for adenoviruses and reoviruses was performed for both C. serpentis-positive and C. serpentis-negative EIS within the breeding colony. No reoviruses were detected in the collection. Adenoviruses were present in 11/68 (16.2%) EISs evaluated, and there was no significant difference between C. serpentis-positive and C. serpentis-negative EISs (p = 0.196). There was no significant difference in adenovirus status between C. serpentis-positive EISs' lifespan (p = 0.191) or survival rates (p = 0.823). These findings suggest that the presence of the adenoviruses found in this study does not contribute to the formation or progression of gastric cryptosporidiosis in EISs.

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.

Molecular Detection and Genetic Characterization of Japanese Encephalitis Virus in Animals from 11 Provinces in China

Japanese encephalitis virus (JEV), which uses a mosquito primary vector and swine as a reservoir host, poses a significant risk to human and animal health. JEV can be detected in cattle, goats and dogs. A molecular epidemiological survey of JEV was conducted in 3105 mammals from five species, swine, fox, racoon dog, yak and goat, and 17,300 mosquitoes from 11 Chinese provinces. JEV was detected in pigs from Heilongjiang (12/328, 3.66%), Jilin (17/642, 2.65%), Shandong (14/832, 1.68%), Guangxi (8/278, 2.88%) and Inner Mongolia (9/952, 0.94%); in goats (1/51, 1.96%) from Tibet; and mosquitoes (6/131, 4.58%) from Yunnan. A total of 13 JEV envelope (E) gene sequences were amplified in pigs from Heilongjiang (5/13), Jilin (2/13) and Guangxi (6/13). Swine had the highest JEV infection rate of any animal species, and the highest infection rates were found in Heilongjiang. Phylogenetic analysis indicated that the predominant strain in Northern China was genotype I. Mutations were found at residues 76, 95, 123, 138, 244, 474 and 475 of E protein but all sequences had predicted glycosylation sites at ′N154. Three strains lacked the threonine 76 phosphorylation site from non-specific (unsp) and protein kinase G (PKG) site predictions; one lacked the threonine 186 phosphorylation site from protein kinase II (CKII) prediction; and one lacked the tyrosine 90 phosphorylation site from epidermal growth factor receptor (EGFR) prediction. The aim of the current study was to contribute to JEV prevention and control through the characterization of its molecular epidemiology and prediction of functional changes due to E-protein mutations.

Direct evidence of fiber-protein-directed hemagglutination by canine adenoviruses

Canine adenoviruses (CAdVs) are divided into two serotypes, CAdV1 and CAdV2, whose members mainly cause infectious hepatitis and laryngotracheitis, respectively, in canids. To gain insight into the molecular basis of viral hemagglutination, we constructed chimeric viruses whose fiber proteins or their knob domains, which play a role in viral attachment to cells, were swapped among CAdV1, CAdV2, and bat adenovirus via reverse genetics. The results revealed that, in each case, viral hemagglutination was specifically mediated by the fiber protein or knob domain, providing direct evidence for fiber-protein-directed receptor-binding characteristics of CAdVs.

Immunological evaluation of recombination PRRSV GP3 and GP5 DNA vaccines in vivo

The porcine reproductive and respiratory syndrome virus (PRRSV) is a threat to the health of pigs worldwide, but commercially available vaccines offer limited protection against PRRSV infection. It is necessary to develop a more effective DNA vaccine. The immunological effects of DNA vaccines with three adjuvants were examined in pigs (Susscrofa domestica) challenged with PRRSV. These DNA vaccines, which encoded PRRSV GP3 and GP5, were formulated with A1, A2, and A3. Serum specific and neutralizing antibodies, IL-4, IFN-γ, IL-2, IL-10, CD4⁺ and CD8⁺T-lymphocytes, health status, histopathology, and viral loads were determined. The results showed that the use of adjuvant A3 led to higher levels of neutralizing antibodies and a lower viral load in pigs compared to the other adjuvants. The neutralizing antibody titers of the pVAX-GP35+A1 and pVAX-GP35+A3 groups reached a peak of 1:19 at 35 dpi. The maximum concentration of IL-4 was 136.77 pg/mL in the pVAX-GP35+A3 group. At 35 dpi, the IFN-γ concentration in the pVAX-GP35+A1 group was 227.4 pg/mL. pVAX-GP35+A3 group shows the highest IL-2 and IL-10 expression to the peak of 597.6 pg/mL and 189.1 pg/mL, respectively. We found a formulation demonstrated beneficial immune outcomes. This study provides an alternative vaccine to protect pigs from PRRSV.