Prevalence and Genomic Sequence Analysis of Domestic Cat Hepadnavirus in the United States

Abstract

Hepadnaviruses are partially double-stranded DNA viruses that infect a variety of species. The prototypical virus in this family is the human hepatitis B virus, which chronically infects approximately 400 million people worldwide and is a risk factor for progressive liver disease and liver cancer. The first hepadnavirus isolated from carnivores was a domestic cat hepadnavirus (DCH), initially identified in Australia and subsequently detected in cats in Europe and Asia. As with all characterized hepadnaviruses so far, DCH infection has been associated with hepatic disease in its host. Prevalence of this infection in the United States has not been explored broadly. Thus, we utilized conventional and quantitative PCR to screen several populations of domestic cats to estimate DCH prevalence in the United States. We detected DCH DNA in 1 out of 496 animals (0.2%) in the U.S. cohort. In contrast, we detected circulating DCH DNA in 7 positive animals from a cohort of 67 domestic cats from Australia (10.4%), consistent with previous studies. The complete consensus genome of the U.S. DCH isolate was sequenced by Sanger sequencing with overlapping PCR products. An in-frame deletion of 157 bp was identified in the N-terminus of the core open reading frame. The deletion begins at the direct repeat 1 sequence (i.e., the 5′ end of the expected double-stranded linear DNA form), consistent with covalently closed circular DNA resultant from illegitimate recombination described in other hepadnaviruses. Comparative genome sequence analysis indicated that the closest described relatives of the U.S. DCH isolate are those previously isolated in Italy. Motif analysis supports DCH using NTCP as an entry receptor, similar to human HBV. Our work indicates that chronic DCH prevalence in the U.S. is likely low compared to other countries.

Domestic Cat Hepadnavirus: Molecular Epidemiology and Phylogeny in Cats in Hong Kong

“…Furthermore, a link between DCH and liver injury could justify the development of novel antivirals and vaccines for cats. Similarities between HBV and DCH DR/epsilon regions identified in this study, and the predicted viral receptor [ 11 ], support similar approaches to target DCH therapeutically. Unfortunately, many nucleoside/nucleotide analogues—the mainstay of human HBV antiviral treatment—are unacceptably toxic to cats [ 30 ].…”

“…This study showed that DCH is circulating among cats in Hong Kong, with a molecular prevalence of 11.1%, as measured by DCH DNA detection in whole blood. The prevalence in other regions varies widely, with DCH-positive cats apparently uncommon in the USA (0.2%) [ 11 ], Japan (0.78%) [ 12 ], and UK (1.9%) [ 10 ]; whereas virus DNA has been readily detected in cats in Australia (6.5%) [ 6 ], Italy (10.8%; 4.2%) [ 7 , 26 ], Thailand (18.5%) [ 15 ], and Malaysia (12.3%) [ 9 ]. Despite study design differences, it is likely that there are genuine regional differences in DCH prevalence, potentially caused by various transmission dynamics, as with human HBV [ 27 ].…”

“…Our analyses show that there is limited variation of DCH across large geographical regions. Phylogenetic analysis of complete DCH genome studies suggest isolates found in Hong Kong are closely related to those in Southeast Asia and Australia [ 8 , 11 , 12 ]. Using definitions stated previously for HBV, DCH exists as at least two genotypes (>8% nucleotide difference [ 31 ]), with all DCH viruses characterized so far clustering into a single genotype—referred to here as Genotype A—except for a single isolate from Japan, currently the only member of a second DCH genotype, Genotype B.…”

“…Since DCH was discovered in a domestic cat in Australia in 2018 [ 6 ], the virus has been shown to be geographically widespread and common, with infected cats identified in Australia, New Zealand, Italy, the UK, Malaysia, Thailand, Japan, and the USA [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. The reported prevalence of circulating DCH DNA varies from less than 1% in the USA and Japan to more than 18% in Thailand.…”

Conserved use of the sodium/bile acid cotransporter (NTCP) as an entry receptor by hepatitis B virus and domestic cat hepadnavirus

“…In 2018, an HBV-like virus, domestic cat hepadnavirus (DCH), was identified in domestic cats in Australia and was associated with feline chronic hepatitis (Aghazadeh et al, 2018), suggesting a similarity with HBV pathogenesis. Subsequently, DCH was identified in other countries, including Italy (Lanave et al, 2019), Thailand (Piewbang et al, 2020), Malaysia (Anpuanandam et al, 2021), United Kingdom (Jeanes et al, 2022), United States (Stone et al, 2022), Hong Kong (Capozza et al, 2023), and Japan (Takahashi et al, 2022). DCH has a partially double-stranded, circular DNA genome of ~3,200 bases in length (Aghazadeh et al, 2018).…”