Identification of hepadnavirus in the sera of cats

Abstract

Hepadnaviruses infect several animal species. The prototype species, human hepatitis B virus (HBV), increases the risk of liver diseases and may cause cirrhosis and hepatocellular carcinoma. Recently a novel hepadnavirus, similar to HBV, has been identified through transcriptomics studies in a domestic cat with large cell lymphoma in Australia. Herewith, a collection of 390 feline serum samples was screened for hepadnavirus. Overall, the virus was identified in 10.8% of the sera with a significantly higher prevalence (17.8%) in the sera of animals with a clinical suspect of infectious disease. Upon genome sequencing, the virus was closely related (97.0% nt identity) to the prototype Australian feline virus Sydney 2016. The mean and median values of hepadnavirus in the feline sera were 1.3 × 10⁶ and 2.1 × 10⁴ genome copies per mL (range 3.3 × 10⁰-2.5 × 10⁷ genome copies per mL). For a subset of hepadnavirus-positive samples, information on the hemato-chemical parameters was available and in 10/20 animals a profile suggestive of liver damage was present. Also, in 7/10 animals with suspected hepatic disease, virus load was >10⁴ genome copies per mL, i.e. above the threshold considered at risk of active hepatitis and liver damage for HBV.

Figure 1

Results of the screening for DCH in the feline sera. The prevalence of DCH was evaluated in sera collected for the diagnosis of infectious diseases (collection A) and sera submitted to the laboratory for pre-surgical evaluation or for suspected metabolic or neoplastic disease (collection B) and used for comparison (panel A). The prevalence of DCH was also evaluated in relation to sex (panel B) and age (panel C) of the animals.

Figure 2

Genome organization of the DCH. The complete genome consists of 3184 bp. The outermost circles represent the read mapping coverage (orange) of the genome. In the innermost circles the proteins encoded by the polymerase, surface, core and X ORFs are labelled (yellow), as are the positions of the primers (green) and probe (red) used in this study (Table 2) are indicated.

Figure 3

Bayesian phylogenetic tree based on complete genomic sequences of hepadnaviruses retrieved from the Genbank database. Posterior probability values >95% are shown on the nodes of the tree. Italian feline strain ITA/2018/165-83 (GenBank accession nr. MK117078) is indicated by black arrow. White Sucker hepadnavirus (NC_027922) was used as outgroup. The scale bar indicates the number of nucleotide substitutions per site.