Identification and nucleotide sequence of the early region 1 from canine adenovirus types 1 and 2

Successful treatment of coagulation disorders and hypoalbuminaemia in a puppy with Infectious Canine Hepatitis

Due to high vaccination coverage of the dog population in Western and Middle Europe, veterinarians are usually not familiar with clinical signs and treatment of Infectious Canine Hepatitis (ICH). This case report describes a 4-month-old female mixed breed dog that was imported from Bulgaria. According to the history, the puppy was presented with lethargy, pyrexia, icterus and melaena. On clinical examination, the dog additionally exhibited a painful abdomen and bleeding tendency at the venous puncture sites. Blood analysis revealed anaemia, left shift without leucocytosis, increased liver enzymes and prolonged coagulation times. Polymerase Chain Reaction (PCR) and subsequently sequence analysis performed out of urine confirmed Canine Adenovirus 1 (CAV-1) as the causative agent of the disease. Peripheral oedema developed on the dog´s head and limbs during the progression of the disease due to severe hypoalbuminaemia. Initial treatment of the puppy included transfusion of whole blood and fresh frozen plasma. Hypoalbuminaemia was treated by transfusion using human albumin. On day eight after starting the treatment, the dog was released from the hospital due to an unremarkable clinically condition. This case report indicates that ICH might become a re-emerging disease by means of rising dog imports. Especially, the severe form of ICH can be associated with several life-threatening complications that require hospitalisation and intensive care treatment.

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.

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.

Xenogenic Adenoviral Vectors

Many nonhuman adenoviruses (AdVs) of simian, bovine, porcine, canine, ovine, murine, and fowl origin are being developed as gene delivery systems for recombinant vaccines and gene therapy applications. In addition to circumventing preexisting human AdV (HAdV) immunity, nonhuman AdV vectors utilize coxsackievirus-adenovirus receptor or other receptors for vector internalization, thereby expanding the range of cell types that can be targeted. Nonhuman AdV vectors also provide excellent platforms for veterinary vaccines. A specific nonhuman AdV vector when used in its species of origin could provide an excellent animal model for evaluating the vector efficacy and pathogenesis. These vectors are useful in prime–boost approaches with other AdV vectors or with other gene delivery systems including DNA immunization and viral or bacterial vectors. When multiple vector inoculations are required, nonhuman AdV vectors could supplement HAdV or other viral vectors.

Sequence analysis of the canine adenovirus 2 fiber-encoding gene

The gene coding for the fiber protein (Fip) of canine adenovirus type 2 (CAV-2) has been cloned and sequenced. The putative protein has 80% sequence similarity with the CAV-1 Fip. The observed differences may contribute to the known differences in cell tropism and virulence of the two types of CAV.

Two genomic variations in the E1 region of canine adenovirus type 2 strains

We amplified the E1 region of canine adenovirus type 2 genomes by the polymerase chain reaction (PCR) and analyzed the PCR products by using eight restriction endonucleases. Restriction patterns of the E1 region cleaved with HaeIII and RsaI revealed two genomic variations among the canine adenovirus type 2 strains. Although the clinical significance of two distinct genotypes among the canine adenovirus type 2 strains is currently unknown, these genomic variations are well conserved among different strains in each genotype and suggest that the Japanese field strains, with reference to the E1 region, are different from the non-Japanese strains examined.

Differences in the E3 regions of the canine adenovirus type 1 and type 2

Sequence analysis of a region extending between the pVIII and the fiber gene of Canine adenovirus type 1 (Cav-1, Utrecht) and type 2 (Cav-2, Manhattan) was performed. The results revealed a high level of identity between the two viruses when the pVIII gene and the N-terminal part of the fiber gene were compared. The open reading frames of region E3 in of Cav-1 and Cav-2 encoded a 22 kDa and 40.7 kDa polypeptide, respectively. The Cav-1 and Cav-2 E3 region polypeptides shared conserved amino and carboxyl domains. In Cav-2 an extra sequence of about 500 nucleotides was present, appearing like an in frame insertion of foreign DNA. It can be speculated that this insertion in the E3 region contributes to the observed biological differences between Cav-1 and Cav-2.

Sequence analysis of putative E3 and fiber genomic regions of two strains of canine adenovirus type 1

The nucleotide sequences of the genomes of two strains of canine adenovirus, type 1 (Glaxo and CLL) have been determined within the region spanning approximately 0.80-0.91 map unit. Homology comparisons with other adenoviral DNAs indicate that this region contains part of the hexon-associated protein (pVIII) precursor gene on the left, and a 57-kDa fiber-encoding gene on the right. In both viral strains, the sequences of these genes are identical. Accepting the generally highly conserved nature of the genetic organization of adenoviral genomes, the 1136-bp sequence between them would include the canine equivalent of the human adenoviral E3 region. In the Glaxo strain, which is nonattenuated, this sequence contains only two R-strand open reading frames capable of coding for polypeptides of 60 residues or more. One of these appears to code for a transmembrane glycoprotein of 194 amino acid residues. Neither ORF, however, shows significant homology with any other known adenoviral DNA or protein sequence. The corresponding region in the attenuated strain CLL is almost identical with that of the Glaxo, but with a 325-bp deletion resulting in a fusion of the two ORFs. It seems, therefore, that neither ORF is essential for viral replication in vitro, since the CLL strain replicates just as efficiently as the Glaxo. The suggestion is made that the attenuation of the CLL strain may be related to the nonfunctionality of its E3 gene product(s).