Duck hepatitis A virus type 1 mediates cell cycle arrest in the S phase

DHAV-1 3C protein promotes viral proliferation by antagonizing type I interferon via upregulating the ANXA2 protein

The picornavirus 3C protein plays a crucial role in viral infection. One of its functions is inhibiting the immune response by cleaving or degrading innate immune-related proteins to promote viral infection. Annexin A2 (ANXA2) is a multifunctional host protein that plays a key role in various cellular processes, it also participates in viral infection. However, whether the ANXA2 protein interacts with the picornavirus 3C protein to regulate viral infection and its effect on type I interferon (IFN) has not been reported. In this study, we found that the 3C protein of duck hepatitis A virus 1 (DHAV-1) interacts with the ANXA2 protein and upregulates ANXA2 expression. Moreover, the ANXA2 protein interacts with the cGAS, STING, RIG-I, MDA5, MAVS, and TBK1 proteins, suppresses its activated IFN-β and ISRE promoter activity, promotes RIG-I, MDA5, and TBK1 protein degradation through caspase-dependent pathway, thereby inhibiting IFN-β production and promoting DHAV-1 proliferation. This study lays a theoretical foundation for further understanding the interaction between viruses and hosts, as well as for analyzing the function of the picornavirus 3C protein and the ANXA2 protein. It also suggests a novel pathway, such as targeting key sites on the 3C protein to upregulate ANXA2, for a target-based antiviral strategy.

Matrine relieved DHAV-1-induced hepatocyte excessive interferon and pyroptosis by activating mitophagy

Duck hepatitis A virus type 1 (DHAV-1) is a significant pathogen affecting ducklings, capable of causing rapid mortality and adversely impacting the development of the duck industry. Matrine, the primary active ingredient in various Chinese herbal medicines, has demonstrated antiviral and anti-inflammatory properties. Nevertheless, the effects and mechanisms of action of matrine against DHAV-1 infection remain unclear. This research investigates the effects of matrine on DHAV-1 infection and elucidates the mechanisms involved. We found that matrine mitigated the excessive retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) signaling response, pyroptosis, and mitochondrial damage induced by DHAV-1 in duckling livers and duck embryonic hepatocytes (DEHs). Additionally‌, by incorporating the autophagy inhibitor chloroquine, we observed that the effects of matrine on the regulation of excessive interferon (IFN) production, pyroptosis, mitochondrial damage, and oxidative stress were reversed. Overall, matrine inhibited excessive IFN production and pyroptosis by promoting mitophagy, suggesting that matrine may act as a possible therapeutic agent for addressing DHAV-1 infection and other viral hepatitis.

Advances in the Duck Hepatitis A virus and lessons learned from those in recent years

Duckviral hepatitis (DVH) is a highly lethal and highly transmissible viral infectious disease of ducklings caused by the Duck Hepatitis A virus (DHAV), which is characterized by clinical neurological symptoms and liver enlargement with spot-like hemorrhages. In recent years, the change in diagnosis, prevention, and control of the disease has brought great challenges due to the mutation and recombination of epidemic strains, outbreaks and epidemics of genotype 3 (DHAV-3), and the rising trend of mixed infections. Here, we review DHAV on aspects of molecular biological characteristics, epidemiology, pathologic changes, pathogenesis, diagnosis, prevention, and control of the DVH to provide a scientific basis for basic and applied research in the future.

PI4KB is an essential host factor for duck hepatitis a virus 1 replication and translation

Duck hepatitis A virus 1 (DHAV-1) is one of the most serious pathogens endangering the duck industry. Phosphatidylinositol 4-kinases (PI4Ks) are important for viral replication, and different viruses have different strategies to hijack PI4Ks. To date, few studies have investigated the DHAV-1 life cycle; thus, whether PI4Ks are required for DHAV-1 replication has not been reported. In this study, we found that the PI4KB protein, a PI4K, promoted the replication and translation of DHAV-1, and the 2A2, 2C, 2BC, 3A, 3AB, 3D, and 3CD proteins of DHAV-1 were able to interact with the PI4KB protein. Amino acids 101-120 of the 2A2 protein is the region where the 2A2 protein interacts with the PI4KB protein.

Duck hepatitis A virus 1-encoded 2B protein disturbs ion and organelle homeostasis to promote NF-κB/NLRP3-mediated inflammatory response

Previous studies by our group and others have highlighted the critical role of hyperinflammation in the pathogenicity of duck hepatitis A virus 1 (DHAV-1), an avian picornavirus that has caused significant devastation in the duck industry worldwide for decades. However, the precise mechanisms by which DHAV-1 infection regulates the inflammatory responses, particularly the production of IL-1β, remain poorly understood. In this study, we demonstrate that DHAV-1 infection triggers NF-κB- and NLRP3 inflammasome-mediated IL-1β production. Mechanistically, DHAV-1 infection, particularly its replication and translation, disrupts cellular homeostasis of Ca2+, K+, ROS and cathepsin, which act cooperatively as assembly signals for NLRP3 inflammasome activation. By screening DHAV-1-encoded proteins, we identified that the viroporin 2B dominates NF-κB as well as NLRP3 inflammasome activation. Mutation analysis revealed that I43 within the 2B protein is the key amino acid for Ca2+ mobilization and subsequent activation of NF-κB transcriptional activity and NLRP3 inflammasome. Moreover, DHAV-1 infection and the 2B protein activate the MAVS- and MyD88-NF-κB pathways by relay, providing the necessary priming signals for NLRP3 inflammasome activation. In summary, our findings elucidate a mechanism through which DHAV-1 triggers inflammatory responses via NF-κB/NLRP3 inflammasome activation, offering new perspectives on DHAV-1 pathogenesis and informing the development of targeted anti-DHAV-1 treatments.

Multiple functions of the nonstructural protein 3D in picornavirus infection

3D polymerase, also known as RNA-dependent RNA polymerase, is encoded by all known picornaviruses, and their structures are highly conserved. In the process of picornavirus replication, 3D polymerase facilitates the assembly of replication complexes and directly catalyzes the synthesis of viral RNA. The nuclear localization signal carried by picornavirus 3D polymerase, combined with its ability to interact with other viral proteins, viral RNA and cellular proteins, indicate that its noncatalytic role is equally important in viral infections. Recent studies have shown that 3D polymerase has multiple effects on host cell biological functions, including inducing cell cycle arrest, regulating host cell translation, inducing autophagy, evading immune responses, and triggering inflammasome formation. Thus, 3D polymerase would be a very valuable target for the development of antiviral therapies. This review summarizes current studies on the structure of 3D polymerase and its regulation of host cell responses, thereby improving the understanding of picornavirus-mediated pathogenesis caused by 3D polymerase.

Duck hepatitis a virus: Full-length genome-based phylogenetic and phylogeographic view during 1986-2020

Duck hepatitis A virus (DHAV) is one of key pathogens for duck viral hepatitis, especially in Asian duck industry. Currently, two main genotypes (DHAV-1 and -3) exist. To explore insightfully the evolutionary character, we assessed the available 141 full-length genome sequences of DHAV isolated in 1986-2020 globally and divided DHAV-1 and DHAV-3 into further seven (DHAV-1 a-g) and five (DHAV-3 a-e) sub-clades, respectively. Phylogenetic and phylogeographic network analyses indicated great genetic diversity of DHAV identified in China, where the DHAV-1 cluster and DHAV-3 cluster were linked by virus strain HDHV1-BJ (GenBank ID: FJ157172.1) and Du_CH_LSD_090612 (GenBank ID: JF828995.1) via a long mutational branch and intermediate strains. Several strains previously identified as DHAV-1 according to the partial gene sequences were actually clustered within DHAV-3 in full-length genome-based analysis. Furthermore, we identified 32 recombination events across virus genome with the recombination hotspot at the 5' end and upstream of the capsid coding region. The highest variability of DHAV polyprotein was shown at the upstream region of the N terminus P-loop region, e.g., amino acids 672-716, followed by the aa 334-359 in the Capsid encoding region. The results presented here provides a robust insight into the genetic exchange patterns of DHAV genomes during the past decades, which may be used to map the evolutionary history and facilitate preventive measures of DHAVs.

Specific DNAzymes cleave the 300-618 nt of 5'UTR to inhibit DHAV-1 translation and replication

DNAzymes effectively inhibit the expression of viral genes. Duck hepatitis A virus type-1 (DHAV-1) genomic RNA carries an internal ribosome entry site (IRES). The IRES initiates the translation of DHAV-1 via a mechanism that differs from that of cap-dependent translation. Therefore, it is an attractive target for the treatment of DHAV-1. In this study, we designed 6 DNAzymes (Dzs) specifically targeting 300-618 nt sequence in the DHAV-1 5'untranslated region (UTR; a predicted IRES-like element). In the presence of divalent metal ions, three designed DNAzymes (DZ369, DZ454, and DZ514) efficiently cleaved the 300-618 nt sequence of the DHAV-1 5'UTR RNA. The activity of the Dzs was particularly dependent on Mg²⁺ ions. Subsequently, the translation inhibitory activity of these Dzs was determined by western blotting experiments. The Dzs effectively inhibited the translation mediated by the 300-618 nt of DHAV-1 5'UTR in duck embryo fibroblasts (DEFs). Importantly, DZ454 showed the strongest inhibitory effect, and its inhibition was time and dose dependent. However, none of the Dzs showed significant inhibition of cap-dependent translation. These results suggest that these Dzs show specificity for target RNA. Moreover, DZ454 inhibited the replication of DHAV-1. In conclusion, the designed DNAzymes can be used as inhibitors of DHAV-1 RNA translation and replication, providing new insights useful for the development of anti-DHAV-1 drugs.