Caprine parainfluenza virus type 3 N protein promotes viral replication via inducing apoptosis

Rescue of a unique ovine parainfluenza virus type 3 strain via Red/ET assembly

Parainfluenza virus type 3 (PIV3) is an important pathogen that causes respiratory disease in humans and many animals, but ovine infection has been rarely reported. In this study, a strain of ovine parainfluenza virus type 3 (OPIV3) was isolated from a sheep farm in Tianjin, China, and named TJ2022. Phylogenetic analysis indicated a high homology between the TJ2022 strain and the OPIV3 TX01 strain. Compared with the TX01 strain, TJ2022 showed 17 and 13 unique amino acid mutations in the P and L proteins, respectively, and possessed a distinct gene end sequence, suggesting unique genetic evolution of TJ2022. Three-dimensional structural prediction analysis of the L protein indicated that characteristic mutations in the L protein may affect the virus's replication capacity. Host immune response analysis showed that the expression levels of IFN-α, IFN-β, and interferon stimulated genes (Mx1, IFI6, ISG15, and OAS1) were significantly elevated after TJ2022 infection. Furthermore, using the Red/ET homologous recombination system, we constructed an infectious clone of OPIV3 dependent on the T7 promoter (rTJ2022). The rTJ2022 exhibited genetic stability, growth kinetics, and host cell immune response similar to TJ2022. This study establishes the foundation for exploring OPIV3 infection and defense mechanisms, epidemiology, and the potential development of live vector vaccines.

Goose astrovirus induces apoptosis and endoplasmic reticulum stress in gosling hepatocytes

The ongoing Goose astrovirus (GoAstV) epidemic, which primarily infects goslings causing severe liver damage, has inflicted considerable damage on the poultry industry. Endoplasmic reticulum stress (ERS) is a significant modulator of several viral infections, while severe ERS may result in apoptosis. This study examined the roles and possible mechanisms of ERS and apoptosis in GoAstV-induced liver injury in goslings. Two hundred Xingguo gray geese were chosen and randomly separated into two groups (Con and Dis). The Dis group received a subcutaneous injection of GoAstV genotype 2 (GoAstV-2) JX01 (2 × 106 TCID50/0.2 mL), whereas the Con group received a subcutaneous injection of 0.2 mL physiological saline, both at 1 day of life. Subsequent analyses demonstrate that the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) increased following GoAstV infection. Hematoxylin and eosin (HE) staining revealed swollen and ruptured hepatocytes, with significant inflammatory cell infiltration. Electron microscopy revealed expansion of the endoplasmic reticulum (ER) and aggregation of chromatin at the periphery. TUNEL testing further demonstrated an increase in the quantity of positive cells. RT-qPCR and Western blot analyses indicated that GoAstV infection enhanced the expression of ER Ca2+ release channels (IP3R and RYR) and calmodulin-dependent protein kinase II (CaMKII), while decreasing the expression of ER Ca2+ uptake channels (SERCA). Further, GoAstV infection activated ERS-related factors, including GRP78, IRE1α, PERK, ATF6, eIF2α, ATF4, CHOP, TRAF2, and JNK, induced the expression of pro-apoptotic factors (Caspase-3, Caspase-9, and Bax), and inhibited the mRNA and protein expression of the anti-apoptotic factor Bcl-2. Correlation analysis further revealed a potential relationship among ERS gene expression, apoptotic gene expression, and liver injury. In summary, GoAstV infection can lead to liver injury by interfering with ER Ca2+ homeostasis, exacerbating ERS and inducing hepatocyte apoptosis.

PBLD promotes IRF3 mediated the type I interferon (IFN-I) response and apoptosis to inhibit viral replication

Recent studies have implicated the phenazine biosynthesis-like domain-containing protein (PBLD) in the negative regulation of the development and progression of various cancers. However, its function in viral infection remains unknown. In this study, we found that PBLD plays important roles in multiple virus infections including BPIV3, SeV, VSV, and HSV-1. Our study revealed that PBLD enhances the expression of type I interferon (IFN-I) and ISGs through interferon regulatory factor 3 (IRF3). Further study indicated that PBLD promotes transcriptional phosphorylation of IRF3 (S385/386), thereby facilitating virus-induced IFN-I production. Interestingly, PBLD mediates virus-triggered mitochondrial apoptosis through its dependence on IRF3 (K313/315). Mechanistically, PBLD facilitated virus-induced apoptosis by recruiting the Puma protein to the mitochondria via IRF3. Additionally, we performed mutational analyses of IRF3, showing that its loss of either transcriptional or apoptotic function markedly increased viral replication. Moreover, macrophages with PBLD deficiency during viral infection exhibited decreased the IFN-I and ISGs expression, exacerbating viral infection. Importantly, mice deficient in PBLD exhibited increased viral replication and susceptibility to SeV infection, leading to decreased survival. Notably, Cedrelone, a chemical activator of PBLD, has the ability to reduce SeV replication. Collectively, we first discovered the new function of PBLD in viral infection, broadening our understanding of potential therapeutic targets and offering new insights for antiviral drug development.

Autophagy and Apoptosis in Rabies Virus Replication

Rabies virus (RABV) is a single-stranded negative-sense RNA virus belonging to the Rhabdoviridae family and Lyssavirus genus, which is highly neurotropic and can infect almost all warm-blooded animals, including humans. Autophagy and apoptosis are two evolutionarily conserved and genetically regulated processes that maintain cellular and organismal homeostasis, respectively. Autophagy recycles unnecessary or dysfunctional intracellular organelles and molecules in a cell, whereas apoptosis eliminates damaged or unwanted cells in an organism. Studies have shown that RABV can induce both autophagy and apoptosis in target cells. To advance our understanding of pathogenesis of rabies, this paper reviews the molecular mechanisms of autophagy and apoptosis induced by RABV and the effects of the two cellular events on RABV replication.

Research Progress on Emerging Viral Pathogens of Small Ruminants in China during the Last Decade

China is the country with the largest number of domestic small ruminants in the world. Recently, the intensive and large-scale sheep/goat raising industry has developed rapidly, especially in nonpastoral regions. Frequent trading, allocation, and transportation result in the introduction and prevalence of new pathogens. Several new viral pathogens (peste des petits ruminants virus, caprine parainfluenza virus type 3, border disease virus, enzootic nasal tumor virus, caprine herpesvirus 1, enterovirus) have been circulating and identified in China, which has attracted extensive attention from both farmers and researchers. During the last decade, studies examining the etiology, epidemiology, pathogenesis, diagnostic methods, and vaccines for these emerging viruses have been conducted. In this review, we focus on the latest findings and research progress related to these newly identified viral pathogens in China, discuss the current situation and problems, and propose research directions and prevention strategies for different diseases in the future. Our aim is to provide comprehensive and valuable information for the prevention and control of these emerging viruses and highlight the importance of surveillance of emerging or re-emerging viruses.