A hepatitis B virus causes chronic infections in equids worldwide

Serological and Molecular Survey on Domestic Dog Hepadnavirus in Household Dogs, Italy

The discovery of hepadnaviruses in cats (domestic cat hepadnavirus, DCH) and of a DCH-like virus in dogs has raised several questions regarding the role of these viruses in pets, with particular emphasis on their potential impact on animal health and epidemiology, as well as possible zoonotic implications. In this study, by screening an age-stratified collection of 600 canine serum samples for DCH with an ELISA assay based on the recombinant core antigen (DCHCAg), specific antibodies were found with an overall prevalence of 10.0% (60/600), with a higher prevalence in younger and older dogs. By retesting the canine DCHCAbs-positive sera with an ELISA test based on the recombinant surface protein of DCH (DCHSAg), a total of 18 sera (30%, 18/60) also contained IgG anti-DCHSAg. All the sera were also assessed molecularly using either a consensus hepadnavirus PCR or a specific real-time PCR for DCH. Hepadnavirus DNA was detected in four seronegative dogs, with a prevalence rate of 0.7% (4/600). On sequence analysis of the polymerase region amplified with pan-hepadnavirus primers, the amplicons displayed the highest nucleotide identity (97.3-99.6%) to DCH sequences detected in cats and to the domestic dog hepadnavirus recently identified in a canine serum sample from Italy.

A seasonal idiopathic hepatitis syndrome in horses presented to a Midwestern veterinary teaching hospital

OBJECTIVE

To report history, clinical examination findings, clinicopathologic findings, diagnostic test results, treatment, and outcome in horses with a novel idiopathic hepatitis syndrome.

ANIMALS

13 client-owned horses.

PROCEDURES

Medical records of horses that were presented with fever and increased blood liver enzyme activity over a 16-month period were reviewed (December 1, 2020, to April 1, 2022). Collected data included signalment, history, clinical and clinicopathologic findings, diagnostic test results, treatment, clinical progression, and short-term outcome.

RESULTS

Affected horses were presented between December and April of each of the 2 seasons investigated. The majority of horses developed cyclic fevers over the course of 3 weeks, during which time histologic evidence of hepatitis was observed. Histologic lesions included hepatic necrosis, neutrophilic to lymphohistiocytic inflammation, biliary epithelial injury, and portal fibrosis. Systemic inflammation was evidenced by increased serum amyloid A concentration and leukon changes. No horse developed signs of hepatic insufficiency, and all horses clinically recovered. Return of serum activity of GGT to within the reference range occurred within 16 weeks in most horses. Histologic lesions remained evident up to 27 weeks after initial presentation in 1 horse.

CLINICAL RELEVANCE

Although an etiologic agent has not been identified, an apparently seasonal equine hepatitis syndrome was characterized by fever, systemic inflammation, increased liver enzyme activity, and histologic evidence of hepatitis. An infectious cause is suspected on the basis of histology and outcome.

Equine Hepacivirus: A Systematic Review and a Meta-Analysis of Serological and Biomolecular Prevalence and a Phylogenetic Update

Simple Summary

This is a comprehensive review containing the most up-to-date information on Equine Hepacivirus, one of the recently discovered hepatic equine viruses, together with an analysis of serological and biomolecular presence presented in apreviously published papers, and an update on its genetic relationship within the species and with similar species. Extensive description of the EqHV features is included, and results are presented with several tables and figures, providing a valuable reference guide for further studies.

Abstract

Viral hepatitis has recently assumed relevance for equine veterinary medicine since a variety of new viruses have been discovered. Equine Hepacivirus (EqHV) is an RNA virus belonging to the Flaviviridae family that can cause subclinical hepatitis in horses, occasionally evolving into a chronic disease. EqHV, to date, is considered the closest known relative of human HCV. EqHV has been reported worldwide therefore assessing its features is relevant, considering both the wide use of blood products and transfusions in veterinary therapies and its similitude to HCV. The present review resumes the actual knowledge on EqHV epidemiology, risk factors and immunology, together with potential diagnostics and good practices for prevention. Moreover, adhering to PRISMA guidelines for systematic reviews a meta-analysis of serological and biomolecular prevalence and an updated phylogenetic description is presented as a benchmark for further studies.

Acute respiratory failure on varicella pneumonia in Indonesian adult with chronic hepatitis B: A case report and review article

Background

Varicella pneumonia is a rare clinical manifestations and potentially lethal complications of varicella in a previously healthy adult.

Case presentation

An Indonesian male, 44 years old, Javanese ethnic, complained of progressive dyspnea two days. He had previously been contacting varicella from his daughter 3–4 days before dyspnea onset. He showed typical symptoms of varicella, such as fever and vesicles all over the body. He had been in good health despite having a chronic hepatitis B infection. Chest X-ray on admission revealed bilateral diffuse consolidation with air-bronchogram. Diagnosis of varicella pneumonia was based on typical varicella cutaneous, clinical and chest X-ray findings. We installed mechanical ventilatory support in the isolation ward and he received acyclovir and symptomatic treatment. Ventilatory support was removed on the 3rd day. He successfully recovered on the third day and uninstalled an endotracheal tube.

Discussion

The early and accurate diagnosis of varicella pneumonia was based on disease course and chest X-ray. Managing varicella pneumonia with acute respiratory failure was mechanical ventilator support (when needed), an antiviral, and other symptomatic treatment.

Conclusion

Varicella pneumonia is a rare and severe complication with a good prognosis if diagnosed and treated promptly.

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Chronic hepatitis B increases the risk of varicella developing into acute respiratory failure.

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Early diagnosis and prompt treatment give excellent outcome.

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Ventilation mechanical support is a crucial intervention in acute respiratory failure.

Constrained evolution of overlapping genes in viral host adaptation: Acquisition of glycosylation motifs in hepadnaviral precore/core genes

Hepadnaviruses use extensively overlapping genes to expand their coding capacity, especially the precore/core genes encode the precore and core proteins with mostly identical sequences but distinct functions. The precore protein of the woodchuck hepatitis virus (WHV) is N-glycosylated, in contrast to the precore of the human hepatitis B virus (HBV) that lacks N-glycosylation. To explore the roles of the N-linked glycosylation sites in precore and core functions, we substituted T77 and T92 in the WHV precore/core N-glycosylation motifs (⁷⁵NIT⁷⁷ and ⁹⁰NDT⁹²) with the corresponding HBV residues (E77 and N92) to eliminate the sequons. Conversely, these N-glycosylation sequons were introduced into the HBV precore/core gene by E77T and N92T substitutions. We found that N-glycosylation increased the levels of secreted precore gene products from both HBV and WHV. However, the HBV core (HBc) protein carrying the E77T substitution was defective in supporting virion secretion, and during infection, the HBc E77T and N92T substitutions impaired the formation of the covalently closed circular DNA (cccDNA), the critical viral DNA molecule responsible for establishing and maintaining infection. In cross-species complementation assays, both HBc and WHV core (WHc) proteins supported all steps of intracellular replication of the heterologous virus while WHc, with or without the N-glycosylation sequons, failed to interact with HBV envelope proteins for virion secretion. Interestingly, WHc supported more efficiently intracellular cccDNA amplification than HBc in the context of either HBV or WHV. These findings reveal novel determinants of precore secretion and core functions and illustrate strong constraints during viral host adaptation resulting from their compact genome and extensive use of overlapping genes.

Hepadnaviruses infect a wide range of hosts. The human hepatitis B virus (HBV) and woodchuck hepatitis virus (WHV) are two closely related hepadnaviruses. In contrast to the WHV precore protein, which is N-glycosylated, the HBV precore protein lacks N-glycosylation. As precore and core proteins expressed from the overlapping precore/core genes share most of their sequences but have distinct functions, we investigated the roles of the N-linked glycosylation sequons in HBV and WHV precore/core genes. Our results revealed an important role of the N-linked glycosylation sequons in enhancing precore secretion levels and regulating core protein functions in virion secretion and infection. Furthermore, cross-species complementation assays using HBV and WHV core proteins and HBV or WHV genomes defective in core protein expression indicated that both HBV and WHV core proteins could support intracellular viral replication but not virion secretion of the heterologous virus. These results provide novel insights into the evolution of overlapping genes during host adaptation of hepadnaviruses.

Hepadnavirus DNA Is Detected in Canine Blood Samples in Hong Kong but Not in Liver Biopsies of Chronic Hepatitis or Hepatocellular Carcinoma

Chronic hepatitis and hepatocellular carcinoma (HCC) caused by the hepadnavirus hepatitis B virus (HBV) are significant causes of human mortality. A hepatitis-B-like virus infecting cats, domestic cat hepadnavirus (DCH), was reported in 2018. DCH DNA is hepatotropic and detectable in feline blood or serum (3.2 to 12.3%). Detection of HBV DNA has been reported in sera from 10% of free-roaming dogs in Brazil, whereas 6.3% of sera from dogs in Italy tested positive for DCH DNA by real-time quantitative PCR (qPCR). If DCH, HBV, or another hepadnavirus is hepatotropic in dogs, a role for such a virus in the etiology of canine idiopathic chronic hepatitis (CH) or HCC warrants investigation. This study investigated whether DCH DNA could be detected via qPCR in blood from dogs in Hong Kong and also whether liver biopsies from dogs with confirmed idiopathic CH or HCC contained hepadnaviral DNA using two panhepadnavirus conventional PCRs (cPCR) and a DCH-specific cPCR. DCH DNA was amplified from 2 of 501 (0.4%) canine whole-blood DNA samples. A second sample taken 6 or 7 months later from each dog tested negative in DCH qPCR. DNA extracted from 101 liver biopsies from dogs in Hong Kong or the USA, diagnosed by board-certified pathologists as idiopathic CH (n = 47) or HCC (n = 54), tested negative for DCH DNA and also tested negative using panhepadnavirus cPCRs. This study confirms that DCH DNA can be detected in canine blood by qPCR, although at a much lower prevalence than that reported previously. We identified no evidence to support a pathogenic role for a hepadnavirus in canine idiopathic CH or HCC.

A novel hepadnavirus in domestic dogs

Hepadnaviruses have been identified in several animal species. The hepadnavirus prototype, human hepatitis B virus (HBV), is a major public health problem associated with chronic liver diseases and hepatocellular carcinoma. Recently, a novel hepadnavirus, similar to HBV, was identified in domestic cats. Since several pathogens can be shared between cats and dogs, we hypothesized that dogs could also harbor hepadnaviruses and we tested a collection of canine sera with multiple molecular strategies. Overall, hepadnavirus DNA was identified in 6.3% (40/635) of canine serum samples, although the viral load in positive sera was low (geometric mean of 2.70 × 10² genome copies per mL, range min 1.36 × 10²—max 4.03 × 10⁴ genome copies per mL). On genome sequencing, the canine hepadnaviruses revealed high nucleotide identity (about 98%) and similar organization to the domestic cat hepadnavirus. Altered hepatic markers were found in hepadnavirus-positive dogs, although the role of hepadnavirus in canine health remains to be elucidated.

[Ten years of the National Reference Center for hepatitis B viruses and hepatitis D viruses in Giessen, Germany: activities and experiences]

The National Reference Center (NRC) for hepatitis B viruses (HBV) and hepatitis D viruses (HDV) has been located at the Institute of Medical Virology of the Justus Liebig University (JLU) in Giessen, Germany, since its establishment in 2011. This paper describes the NRC's areas of activity and related experience.The NRC offers comprehensive consulting services on all diagnostic and clinical aspects of acute and chronic HBV and HDV infections for the Public Health Service (ÖGD), diagnostic laboratories, clinics, research institutes, and physicians in private practice. Uncertain diagnostic findings can be analyzed and interpreted and epidemiological correlations clarified with the HBV/HDV special diagnostics established at the NRC using state-of-the-art molecular, biochemical, and genetic laboratory tools. The NRC has access to a strain collection of many well-characterized and cloned HBV/HDV isolates, allowing comparative analysis and evaluation of antiviral resistance mutations and immune escape variants. Together with its national and international partner institutions, the NRC initiates and supervises, among other things, interlaboratory studies for the diagnosis of HBV resistance and immune escape for the establishment and validation of international World Health Organization (WHO) standards and for the improvement of quantitative HDV genome determination. The NRC actively participates in current recommendations and guidelines on HBV and HDV and the recommendations of medical societies. It also highlights current HBV/HDV-relevant aspects with contributions in the form of national and international lectures as well as original articles and comments in national and international journals.

Comprehensive Analysis of Hepatitis Delta Virus Assembly Determinants According to Genotypes: Lessons From a Study of 526 Hepatitis Delta Virus Clinical Strains

Human hepatitis Delta virus (HDV) infection is associated to the most severe viral hepatic disease, including severe acute liver decompensation and progression to cirrhosis, and hepatocellular carcinoma. HDV is a satellite of hepatitis B virus (HBV) that requires the HBV envelope proteins for assembly of HDV virions. HDV and HBV exhibit a large genetic diversity that extends, respectively to eight (HDV-1 to -8) and to ten (HBV/A to/J) genotypes. Molecular determinants of HDV virion assembly consist of a C-terminal Proline-rich domain in the large Hepatitis Delta Antigen (HDAg) protein, also known as the Delta packaging domain (DPD) and of a Tryptophan-rich domain, the HDV matrix domain (HMD) in the C-terminal region of the HBV envelope proteins. In this study, we performed a systematic genotyping of HBV and HDV in a cohort 1,590 HDV-RNA-positive serum samples collected between 2001 to 2014, from patients originated from diverse parts of the world, thus reflecting a large genetic diversity. Among these samples, 526 HBV (HBV/A, B, C, D, E, and G) and HDV (HDV-1, 2, 3, and 5 to -8) genotype couples could be obtained. We provide results of a comprehensive analysis of the amino-acid sequence conservation within the HMD and structural and functional features of the DPD that may account for the yet optimal interactions between HDV and its helper HBV.

Natural co-infection of divergent hepatitis B and C virus homologues in carnivores

In humans, co-infection of hepatitis B and C viruses (HBV, HCV) is common and aggravates disease outcome. Infection-mediated disease aggravation is poorly understood, partly due to lack of suitable animal models. Carnivores are understudied for hepatitis virus homologues. We investigated Mexican carnivores (ringtails, Bassariscus astutus) for HBV and HCV homologues. Three out of eight animals were infected with a divergent HBV termed ringtail HBV (RtHBV) at high viral loads of 5 × 10⁹ -1.4 × 10¹⁰ copies/ml serum. Two of the RtHBV-infected animals were co-infected with a divergent hepacivirus termed ringtail hepacivirus (RtHV) at 4 × 10⁶ -7.5 × 10⁷ copies/ml in strain-specific qRT-PCR assays. Immunofluorescence assays relying on HBV core and RtHV NS3/4a proteins indicated that none of the animals had detectable hepadnavirus core-specific antibodies, whereas one RtHV-infected animal had concomitant RtHV-specific antibodies at 1:800 end-point titre. RtHBV and RtHV complete genomes showed typical HBV and HCV structure and length. All RtHBV genomes were identical, whereas RtHV genomes showed four amino acid substitutions located predominantly in the E1/E2-encoding genomic regions. Both RtHBV (>28% genomic nucleotide sequence distance) and RtHV (>30% partial NS3/NS5B amino acid sequence distance) formed new species within their virus families. Evolutionary analyses showed that RtHBV grouped with HBV homologues from different laurasiatherian hosts (carnivores, bats, and ungulates), whereas RtHV grouped predominantly with rodent-borne viruses. Ancestral state reconstructions showed that RtHV, but not RtHBV, likely emerged via a non-recent host switch involving rodent-borne hepacivirus ancestors. Conserved hepatitis virus infection patterns in naturally infected ringtails indicate that carnivores may be promising animal models to understand HBV/HCV co-infection.

Entry of hepatitis B virus: going beyond NTCP to the nucleus

Hepatitis B virus (HBV) infection remains a major cause of liver diseases and hepatocellular carcinoma. HBV infection begins by low-affinity attachment to hepatocytes and subsequent binding with a specific receptor sodium taurocholate cotransporting polypeptide (NTCP) on sinusoidal-basolateral side of liver parenchymal cells. Following internalization with an unclear mechanism, HBV undergoes uncoating, capsid disassembling and culminates in delivering its genome into the nucleus and forms the covalently closed circular (ccc) DNA. In this review, we briefly summarize the current understanding of HBV entry and discuss some unanswered questions along the entry pathway beyond NTCP binding into the nucleus.