The neglected avian hepatotropic virus induces acute and chronic hepatitis in ducks: an alternative model for hepatology

Cheng

et al. 2018

Sci Rep

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Duck hepatitis A virus type 1 (DHAV-1) is one of the most harmful pathogens in the duck industry. The infection of adult ducks with DHAV-1 was previously shown to result in transient cytokine storms in their kidneys. To understand how DHAV-1 infection impacts the host liver, we conducted animal experiments with the virulent CH DHAV-1 strain and the attenuated CH60 commercial vaccine strain. Visual observation and standard hematoxylin and eosin staining were performed to detect pathological damage in the liver, and viral copy numbers and cytokine expression in the liver were evaluated by quantitative PCR. The CH strain (108.4 copies/mg) had higher viral titers than the CH60 strain (104.9 copies/mg) in the liver and caused ecchymotic hemorrhaging on the liver surface. Additionally, livers from ducklings inoculated with the CH strain were significantly infiltrated by numerous red blood cells, accompanied by severe cytokine storms, but similar signs were not observed in the livers of ducklings inoculated with the CH60 strain. In conclusion, the severe cytokine storm caused by the CH strain apparently induces hemorrhagic lesions in the liver, which might be a key factor in the rapid death of ducklings.

Section: Discussionsupporting

confidence: 54%

Cytokine storms are primarily responsible for the rapid death of ducklings infected with duck hepatitis A virus type 1

Xie

Cheng

et al. 2018

Sci Rep

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“…In coxsackievirus B3 (CVB3) infection, the 3C protease cleaves TRIF and mitochondrial antiviral signaling protein (MAVS) to suppress host immunity [33]. In DHAV infection, it has been reported that activation of the toll-like receptor 7 (TLR7) pathway is involved in the immune response and viral clearance [34]. To date, some epidemiological, pathogenic and immunological mechanisms of DHAV have been reported [35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Biochemical characterization of recombinant Avihepatovirus 3C protease and its localization

Sun

Wen

et al. 2019

Virol J

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Background The picornaviral 3C protease mediates viral polyprotein maturation and multiple cleavages of host proteins to modulate viral translation and transcription. The 3C protease has been regarded as a valid target due to its structural similarity among different picornaviruses and minimal sequence similarity with host proteins; therefore, the development of potent inhibitors against the 3C protease as an antiviral drug is ongoing. Duck hepatitis A virus (DHAV) belongs to the Picornavidea family and is a major threat to the poultry industry. To date, little is known about the roles of the DHAV 3C protease plays during infection. Methods In this study, we compared the full-length DHAV 3C protein sequence with other 3C sequences to obtain an alignment for the construction of a phylogenetic tree. Then, we expressed and purified recombinant DHAV 3C protease in the BL21 expression system using nickel-NTA affinity chromatography. The optimization of the cleavage assay conditions and the kinetic analysis for DHAV 3C protease were done by in vitro cleavage assays with a fluorogenic peptide respectively. The inhibitory activity of rupintrivir against the DHAV 3C protease was further evaluated. The localization of the 3C protease in infected and transfected cells was determined using immunofluorescence and confocal microscopy. Results Under different expression conditions, the 3C protease was found to be highly expressed after induction with 1 mM IPTG at 16 °C for 10 h. We synthesized a fluorogenic peptide derived from the cleavage site of the DHAV polyprotein and evaluated the protease activity of the DHAV 3C protease for the first time. We used fluorimetric based kinetic analysis to determine kinetic parameters, and V max and K m values were determined to be 16.52 nmol/min and 50.78 μM, respectively. Rupintrivir was found to exhibit inhibitory activity against the DHAV 3C protease. Using polyclonal antibody and an indirect immunofluorescence microscopy assay (IFA), it was determined that the DHAV 3C protease was found in the nucleus during infection. In addition, the DHAV 3C protease can enter into the nucleus without the cooperation of viral proteins. Conclusions This is the first study to examine the activity of the DHAV 3C protease, and the activity of the DHAV 3C protease is temperature-, pH- and NaCl concentration- dependent. The DHAV 3C protease localizes throughout DHAV-infected cells and can enter into the nucleus in the absence of other viral proteins. The kinetic analysis was calculated, and the V max and K m values were 16.52 nmol/min and 50.78 μM, respectively, using the Lineweaver–Burk plot.

“…The mature ducks in this study were asymptomatic without significantly elevated serum bilirubin, but with elevations of serum alanine aminotransferase (ALT) activity as described previously ( 8 ). This permitted us to study features of asymptomatic hepatitis.…”

Section: Resultsmentioning

confidence: 99%

“…From 140 dpi, the viral copies declined again and finally became undetectable from 224 dpi onward. Hepatitis was first detectable as significantly elevated serum ALT activity at 28 dpi ( 8 ).…”

Section: Resultsmentioning

confidence: 99%

“…Although the host innate immune responses in the development of acute hepatitis in DHAV-1-infected ducklings had been investigated adequately ( 3 , 5 , 6 ), corresponding research on adult ducks is rare ( 7 ). Recently, however, based on pathological research, mature ducks infected with DHAV-1 have been proven as small-animal models for human hepatitis A ( 8 ). Thus, advanced research on virus–host relationships in DHAV-1 infection in mature ducks is especially valuable, which will be beneficial in illuminating the development of human hepatitis.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Virologic and Immunologic Characteristics in Mature Ducks with Acute Duck Hepatitis A Virus 1 Infection

Mao

et al. 2017

Front. Immunol.

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Duck hepatitis A virus 1 (DHAV-1) infection in mature ducks has previously been proposed as a small-animal model for human hepatitis A. However, basic research on the outcome of DHAV-1 infection in mature ducks is limited. Here, we examined the course of viremia, the characteristics of antibody responses, and the profiles of plasma cytokines in mature ducks infected with DHAV-1. During the course of infection, the viremia was detectable soon after infection and persisted for 196 days, however, the ducks presented as clinically asymptomatic. Specific and timely immunoglobulin G (IgG), IgM, and IgA1 responses were elicited. At the same time, extensive inhibition of viral replication was observed with increasing IgG concentration. With respect to pattern-recognition receptors, TLR-7 was mainly involved in triggering the innate defense against the DHAV-1 infection. In addition, plasma immune analytes were measured and were determined to have bidirectional roles in virus clearance. It was concluded that DHAV-1 spreads quickly in blood. The spontaneous clearance of DHAV-1 during asymptomatic infection in mature ducks depends on the cooperation of timely antibody responses and alert innate immune responses. Moreover, the delayed clearance may be associated with a weak interferon-γ-producing CD8+ T cell response. This study allows us to reveal the mechanism of clearance and persistence of DHAV-1 infection in mature ducks. We anticipate that it will provide a basis for future studies focused on defining the nature mechanisms involved in the clearance and persistence of human hepatitis virus.