Duck plague virus US3 protein kinase phosphorylates UL47 and regulates the subcellular localization of UL47

Pathogenicity studies and molecular characterization of DPV infection in ducklings

In the spring of 2023, 10 to 21-day-old chicks in a broiler duck farm in Shandong Province, China, developed swelling of the head and neck, moist eyes with mucous discharge, difficulty in walking, shrinking of the neck, and loose and disorganized coat. Anatomical observation revealed hemorrhages in the esophageal mucosa, myocardium, and liver, and severe hemorrhages in the trachea with copious inflammatory secretions. Soon after, similar symptoms appeared in a large number of ducks in the flock, which eventually led to the elimination of all the 20,000-odd newly introduced ducklings on the farm, resulting in huge economic losses. We detected duck plague virus in the tissues of liver, spleen and lungs of diseased and dead ducks, and successfully isolated the pathogenic strain, named SD423, by inoculating duck embryos and inoculating duck embryo fibroblasts. We successfully conducted animal regression experiments with the isolated strain, and the experimental animals in the 1 d of age group showed symptoms of swollen eyes and tearing, shrinking of the neck, crouching, and hemorrhage in organs such as the liver and intestines successively from the 3rd d. We sequenced the whole genome of the isolated duck plague strain, and by comparing the homology with the published duck plague virus whole sequences in Genbank, the virus strain obtained in this study had the highest homology with the Chinese virulent strain SD (MN518864.1), with nucleotide (nt) homology of about 99.90% and amino acid (aa) homology of about 99.75%, which indicated that the isolate is a virulent strain. Previously, it was reported that the natural infection of duck plague virus mainly occurs above 30 d of age, but the duck plague virus found in this study can naturally infect ducklings up to 20 d of age, and the mortality rate is as high as 100%. In this study, the pathogenicity test and whole genome sequence analysis of this isolate provided data support and theoretical basis for further research on pathogenicity and virulence-related gene analysis of duck plague virus.

The precise function of alphaherpesvirus tegument proteins and their interactions during the viral life cycle

Alphaherpesvirus is a widespread pathogen that causes diverse diseases in humans and animals and can severely damage host health. Alphaherpesvirus particles comprise a DNA core, capsid, tegument and envelope; the tegument is located between the nuclear capsid and envelope. According to biochemical and proteomic analyses of alphaherpesvirus particles, the tegument contains at least 24 viral proteins and plays an important role in the alphaherpesvirus life cycle. This article reviews the important role of tegument proteins and their interactions during the viral life cycle to provide a reference and inspiration for understanding alphaherpesvirus infection pathogenesis and identifying new antiviral strategies.

Duck plague virus Us3 regulates the expression of pUL48

Duck plague (DP) is one of the contagious diseases caused by Duck plague virus (DPV), which is a serious threat to the development of duck farming. Us3 is a PKA-like protein kinase in alphaherpesvirus, which can regulate the biological functions of many viral proteins, but whether Us3 regulates pUL48 protein has not been reported. In this paper, Western Blot, qRT-PCR, dual luciferase reporter system and Co-IP were used to investigate the relationship between pUL48 and Us3. The results showed that: 1) pUL48 interacted with Us3 at 138-256aa through its DBD region. 2) Us3 enhanced the protein expression of pUL48 in a dose-dependent manner. 3) Us3 promoted the mRNA level of pUL48 by activating its promoter activity. 4) Us3 inhibited the transcriptional activation function of pUL48. The results can provide scientific data for perfecting and supplementing the function of alpha herpesvirus Us3 and pUL48.

Mechanism of herpesvirus UL24 protein regulating viral immune escape and virulence

Herpesviruses have evolved a series of abilities involved in the process of host infection that are conducive to virus survival and adaptation to the host, such as immune escape, latent infection, and induction of programmed cell death for sustainable infection. The herpesvirus gene UL24 encodes a highly conserved core protein that plays an important role in effective viral infection. The UL24 protein can inhibit the innate immune response of the host by acting on multiple immune signaling pathways during virus infection, and it also plays a key role in the proliferation and pathogenicity of the virus in the later stage of infection. This article reviews the mechanism by which the UL24 protein mediates herpesvirus immune escape and its effects on viral proliferation and virulence by influencing syncytial formation, DNA damage and the cell cycle. Reviewing these studies will enhance our understanding of the pathogenesis of herpesvirus infection and provide evidence for new strategies to combat against viral infection.

Effects of US3 protein kinase activity on localization of UL31/UL34 protein and nucleocapsids egress of duck plague virus

Duck plague virus (DPV) is a pathogen causing duck plague and has caused huge economic losses in poultry industry. In our previous report, US3 gene deletion from DPV genome seriously impaired virus replication. In this study, we constructed a US3 kinase-inactive mutant (US3K213A) to further explore the function of US3 protein (pUS3) in DPV. Our results showed that the loss of pUS3 kinase activity caused lower viral titers, smaller plaque sizes and a blockage of capsids nuclear egress including primary enveloped virion (PEV) accumulation compared to the parental virus infection. It indicates that the effects of DPV pUS3 on viral propagation depended on its kinase activity. In addition, we conducted electron microscopy analysis to show the outer nuclear membrane (ONM) evaginations and the nuclear envelope (NE) deep invagination in US3K213A-infected cells. Finally, an irregular distribution of pUL31/pUL34 in the NE in △US3- and US3K213A-infected cells and an interaction of pUS3 and pUL31 were found, which suggests that pUS3 potentially targets pUL31 and regulates the localization of pUL31/pUL34 to promote nucleocapsids egress through its kinase activity.