The PERK/PKR-eIF2α pathway negatively regulates porcine hemagglutinating encephalomyelitis virus replication by attenuating global protein translation and facilitating stress granule formation

IFN-β contributes to astrocyte activation in the brain following coronavirus PHEV infection independent on peripheral immunity

Porcine hemagglutinating encephalomyelitis (PHE), caused by a betacoronavirus named porcine hemagglutinating encephalomyelitis virus (PHEV), is a highly fatal disease of pigs characterized by nonsuppurative encephalitis. Activation of astrocytes is a hallmark of viral encephalomyelitis; however, the mechanism of PHEV-induced astrocyte activation is currently unknown. Based on mouse model, we show that PHEV infection led to astrogliosis in mouse brain and brain slice cultures (BSCs), as indicated by increased expression of glial fibrillary acidic protein (GFAP). PHEV can neither infect nor activate primary astrocytes in vitro, indicating that activation of astrocytes maybe mediated by factors secreted from viral infected neurons but not by direct viral infection of astrocytes. PHEV infection results in increased interferon (IFN) response in later stage, we thereafter focused on whether IFN-β can activate astrocytes after PHEV infection similar to other neurotropic viruses. IFN-β treatment resulted in both the upregulation of GFAP and activation-associated cytokines/chemokines in mouse primary astrocytes. Furthermore, the addition of IFN-β neutralization antibody prevented PHEV-infected mouse brain tissue homogenate from activating astrocytes. Taken together, IFN-β triggers the activation of astrocytes in the central nervous system (CNS) following PHEV infection. Further understanding of the role of activated astrocytes during PHEV infection may provide new insights for treatment this disease.

GCRV-encoded circRNA circ_20 forms a ternary complex with BIP and PERK to delay virus replication by inhibiting the PERK-eIF2α pathway

Viral circRNAs play important roles in host-virus interactions. Previous reports showed that grass carp reovirus (GCRV) encodes 32 circRNAs, and circ_20 from the negative strand of GCRV genome segment 7 has the potential to regulate GCRV replication. However, the regulatory mechanism of circ_20 on GCRV remains unknown. In this study, circ_20 was further validated, and circ_20 negatively regulated ERS, the PERK pathway, and ROS production in GCRV-infected cells. Furthermore, circ_20 inhibited the PERK pathway by forming a ternary complex with BIP and PERK, resulting in delaying GCRV replication. RNA pull-down results indicated that the 51-102 nt region of circ_20 interacts with BIP, while the 451-502 and 514-565 nt regions interact with PERK. After the deletion of these interaction regions, the ability of circ_20 to promote BIP-PERK interaction decreases, leading to a decrease in the ability to inhibit GCRV proliferation. These findings uncovered new insights into the complex interplay between viruses and host cells and provided a novel understanding of the significance of viral circRNAs in virus-host interactions.

Enhancement of Stress Granule Formation by a Chiral Compound Targeting G3BP1 via eIF2α Phosphorylation

The chirality of a chemical differentiates it from its mirror-image counterpart. This unique property has significant implications in chemistry, biology, and drug discovery, where chiral chemicals display high selectivity and activity in achieving target specificity and reducing attrition rates in drug development. Stress granules (SGs) are dynamic assemblies of proteins and RNA that form in the cytoplasm of cells under stress conditions. Modulating their formation or disassembly could offer a novel approach to treating a wide range of diseases. This has led to significant interest in SGs as potential therapeutic targets. This study examined the NTF2-like domain of G3BP1 as a possible target for SG modulation. Molecular docking was used to simulate the interactions of compounds with the domain, and a potential candidate with a chiral structure was identified. The experiments showed that the compound induced the formation of SG-like granules. Importantly, the ability of this compound to modulate SG offers valuable insights into a new mechanism underlying the dynamics and promoting the assembly of SGs, and this new mechanism, in turn, holds potential for the development of drugs with diverse mechanisms of action and potentially synergistic effects.

Endoplasmic reticulum stress in diseases

The endoplasmic reticulum (ER) is a key organelle in eukaryotic cells, responsible for a wide range of vital functions, including the modification, folding, and trafficking of proteins, as well as the biosynthesis of lipids and the maintenance of intracellular calcium homeostasis. A variety of factors can disrupt the function of the ER, leading to the aggregation of unfolded and misfolded proteins within its confines and the induction of ER stress. A conserved cascade of signaling events known as the unfolded protein response (UPR) has evolved to relieve the burden within the ER and restore ER homeostasis. However, these processes can culminate in cell death while ER stress is sustained over an extended period and at elevated levels. This review summarizes the potential role of ER stress and the UPR in determining cell fate and function in various diseases, including cardiovascular diseases, neurodegenerative diseases, metabolic diseases, autoimmune diseases, fibrotic diseases, viral infections, and cancer. It also puts forward that the manipulation of this intricate signaling pathway may represent a novel target for drug discovery and innovative therapeutic strategies in the context of human diseases.

The HRD1-SEL1L ubiquitin ligase regulates stress granule homeostasis in couple with distinctive signaling branches of ER stress

Stress granules (SGs) are membrane-less cellular compartments which are dynamically assembled via biomolecular condensation mechanism when eukaryotic cells encounter environmental stresses. SGs are important for gene expression and cell fate regulation. Dysregulation of SG homeostasis has been linked to human neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we report that the HRD1-SEL1L ubiquitin ligase complex specifically regulates the homeostasis of heat shock-induced SGs through the ubiquitin-proteasome system (UPS) and the UPS-associated ATPase p97. Mechanistically, the HRD1-SEL1L complex mediates SG homeostasis through the BiP-coupled PERK-eIF2α signaling axis of endoplasmic reticulum (ER) stress, thereby coordinating the unfolded protein response (UPR) with SG dynamics. Furthermore, we show that the distinctive branches of ER stress play differential roles in SG homeostasis. Our study indicates that the UPS and the UPR together via the HRD1-SEL1L ubiquitin ligase to maintain SG homeostasis in a stressor-dependent manner.

Insights into the Activation of Unfolded Protein Response Mechanism during Coronavirus Infection

Coronaviruses represent a significant class of viruses that affect both animals and humans. Their replication cycle is strongly associated with the endoplasmic reticulum (ER), which, upon virus invasion, triggers ER stress responses. The activation of the unfolded protein response (UPR) within infected cells is performed from three transmembrane receptors, IRE1, PERK, and ATF6, and results in a reduction in protein production, a boost in the ER's ability to fold proteins properly, and the initiation of ER-associated degradation (ERAD) to remove misfolded or unfolded proteins. However, in cases of prolonged and severe ER stress, the UPR can also instigate apoptotic cell death and inflammation. Herein, we discuss the ER-triggered host responses after coronavirus infection, as well as the pharmaceutical targeting of the UPR as a potential antiviral strategy.

Bovine parainfluenza virus type 3 infections induce ER stress-mediated autophagy to facilitate virus replication

Bovine Parainfluenza Virus Type 3 (BPIV3) serves as a crucial pathogen in cattle, adept at triggering severe respiratory symptoms. This investigation explores the intricate interplay of endoplasmic reticulum stress (ER stress), unfolded protein response (UPR), and autophagy upon BPIV3 infection. In this study, we initially confirm a substantial increase in glucose regulatory protein 78 (GRP78) expression, accompanied by noticeable morphological changes and significant expansion of the ER lumen observed through transmission electron microscopy upon BPIV3 infection. Our findings indicate that ER Stress is induced during BPIV3 infection in vitro. Subsequently, we illustrate that BPIV3 triggers ER Stress to facilitate viral replication through heightened autophagy through treatment with the ER stress inhibitor 4-phenylbutyrate (4-PBA) and utilizing small interfering RNA (siRNA) technology to knock down GRP78. Additionally, we observe that the activation of ER stress initiates the UPR via PERK and ATF6 pathways, with the IRE1 pathway not contributing to the regulation of ER stress-mediated autophagy. Moreover, intervention with the PERK inhibitor GSK2606414, ATF6 inhibitor Ceapin-A7, and siRNA technology successfully reverses BPIV3-induced autophagy. In summary, these findings propose that BPIV3 induces ER stress to enhance viral replication through increased autophagy, with the PERK and ATF6 pathways playing a significant role in ER stress-mediated autophagy.

African swine fever virus maintains de novo global cellular protein synthesis and inhibits stress granules formation via dephosphorylating eIF2α

African swine fever virus (ASFV) has caused enormous economic losses since its first reported detection, and there is still no effective vaccines or drug treatment. During infection, viruses may employ various strategies, such as regulating the host endoplasmic reticulum stress/unfolded protein response or the formation of stress granules (SGs), to form an optimal environment for virus replication. However, how ASFV infection regulates host endoplasmic reticulum stress, eIF2α-regulated protein synthesis, and the formation of SGs remains unclear. Here, we evaluated the activation of ER stress and its three downstream axes during ASFV infection and identified a powerful dephosphorylation of eIF2α by ASFV ex vivo. This strong dephosphorylation property could maintain the efficiency of eIF2α-mediated de novo global protein synthesis, thus ensuring efficient viral protein synthesis at early stage. In addition, the powerful dephosphorylation of eIF2α by ASFV upon infection could also inhibit the formation of SGs induced by sodium arsenite. In addition, a specific eIF2α dephosphorylation inhibitor, salubrinal, could partially counteract ASFV-mediated eIF2α dephosphorylation and inhibit viral replication. Our results provide new insights into the areas of ASFV`s escape from host immunity and hijacking of the host protein translation system.

Cellular Stress Responses against Coronavirus Infection: A Means of the Innate Antiviral Defense

Cellular stress responses are crucial for maintaining cellular homeostasis. Stress granules (SGs), activated by eIF2α kinases in response to various stimuli, play a pivotal role in dealing with diverse stress conditions. Viral infection, as one kind of cellular stress, triggers specific cellular programs aimed at overcoming virus-induced stresses. Recent studies have revealed that virus-derived stress responses are tightly linked to the host's antiviral innate immunity. Virus infection-induced SGs act as platforms for antiviral sensors, facilitating the initiation of protective antiviral responses called "antiviral stress granules" (avSGs). However, many viruses, including coronaviruses, have evolved strategies to suppress avSG formation, thereby counteracting the host's immune responses. This review discusses the intricate relationship between cellular stress responses and antiviral innate immunity, with a specific focus on coronaviruses. Furthermore, the diverse mechanisms employed by viruses to counteract avSGs are described.

Porcine IGFBP3 promotes porcine circovirus type 2 replication via PERK/eIF2α mediated DNA damage

The infection of porcine circovirus type 2 (PCV2) triggers activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathway and leads to DNA damage. Insulin-like growth factor-binding protein 3 (IGFBP3) may interact with the endoplasmic reticulum (ER). It remains unclear whether IGFBP3 regulates DNA damage via ER stress to mediate PCV2 replication. In this study, we observed an upregulation of porcine IGFBP3 expression during PCV2 infection, and overexpression of IGFBP3 enhanced the expression of PCV2 Cap protein, PCV2 DNA copy number, and viral titers in PK-15 B6 cells and 3D4/21 cells. Additionally, overexpression of IGFBP3 induced an increase in the DNA damage marker γH2AX by activating the PERK/eIF2α pathway without concomitant activation of ATF4, IRE1α, and ATF6α/GRP78 pathways in PK-15 B6 cells and 3D4/21 cells. Knockdown of IGFBP3 had a reverse effect on PCV2 replication in PK-15 B6 cells and 3D4/21 cells. Furthermore, treatment with etoposide enhanced PCV2 replication while KU57788 decreased it. GSK2606414 and salubrinal limited both DNA damage and viral replication. Therefore, our findings suggest that porcine IGFBP3 promotes PCV2 replication through the PERK/eIF2α pathway-mediated induction of DNA damage in PK-15 B6 cells and 3D4/21 cells. Our study provides a basis for exploring novel antiviral strategies via the extensive understanding of the relationships between host cellular proteins and viral replication.

The role of protein kinase R in placental inflammation, mtUPR and apoptosis

INTRODUCTION

Placental inflammation is implicated in the pathophysiology of many pregnancy complications, including fetal growth restriction, preeclampsia, gestational diabetes, and choriocarcinoma. Mitochondrial dysfunction, one of the outcomes of placental inflammation, is characterized by loss of membrane potential, accumulation of oxygen radicals, mitochondrial protein folding defects, and disturbances in mitochondrial dynamics. Protein kinase R (PKR) is stimulated by double-stranded RNA and bacterial endotoxins in the presence of pathogens and is a critical immune response enzyme. PKR is also correlated with the cell death response during endoplasmic reticulum stress. In this study, we aim to investigate the effects of PKR activity stimulated by lipopolysaccharide (LPS), and double-stranded RNA analog (Poly I:C) on mitochondrial unfolded protein response (mtUPR), mitochondrial membrane potential, apoptosis, and oxidative stress in placental trophoblasts.

METHODS

We applied LPS and Poly I:C to BeWo cells to induce PKR activation. In addition, cells were treated with 2-aminopurine (2-AP) to inhibit the kinase activity of PKR. Protein levels of ATP-dependent Clp protease proteolytic subunit (CLPP) and heat shock protein 60 (HSP60) were determined after treatments. Apoptotic markers were detected by real-time PCR and flow cytometry. PKR-induced reactive oxygen radicals (ROS) accumulation and mitochondrial membrane potential change were assessed by flow cytometry.

RESULTS

It was determined that PKR activation-induced apoptosis in BeWo cells by reducing the levels of mtUPR proteins (CLPP and HSP60) and caused a decrease in mitochondrial membrane potential. PKR inhibition was sufficient for decreases in apoptotic markers and caused a reduction in the ratio of depolarized and ROS (+) cells.

DISCUSSION

Our results showed that LPS and Poly I:C administration stimulated PKR in BeWo cells in vitro. Furthermore, PKR activation is correlated with the levels of proteins involved in mitochondrial homeostasis and apoptosis. Our findings will contribute to understanding the role of PKR activation in placental inflammation and related diseases.

Starvation Protects Hepatocytes from Inflammatory Damage through Paradoxical mTORC1 Signaling

Background and aims: Sepsis-related liver failure is associated with a particularly unfavorable clinical outcome. Calorie restriction is a well-established factor that can increase tissue resilience, protect against liver failure and improve outcome in preclinical models of bacterial sepsis. However, the underlying molecular basis is difficult to investigate in animal studies and remains largely unknown.

METHODS

We have used an immortalized hepatocyte line as a model of the liver parenchyma to uncover the role of caloric restriction in the resilience of hepatocytes to inflammatory cell damage. In addition, we applied genetic and pharmacological approaches to investigate the contribution of the three major intracellular nutrient/energy sensor systems, AMPK, mTORC1 and mTORC2, in this context.

RESULTS

We demonstrate that starvation reliably protects hepatocytes from cellular damage caused by pro-inflammatory cytokines. While the major nutrient- and energy-related signaling pathways AMPK, mTORC2/Akt and mTORC1 responded to caloric restriction as expected, mTORC1 was paradoxically activated by inflammatory stress in starved, energy-deprived hepatocytes. Pharmacological inhibition of mTORC1 or genetic silencing of the mTORC1 scaffold Raptor, but not its mTORC2 counterpart Rictor, abrogated the protective effect of starvation and exacerbated inflammation-induced cell death. Remarkably, mTORC1 activation in starved hepatocytes was uncoupled from the regulation of autophagy, but crucial for sustained protein synthesis in starved resistant cells.

CONCLUSIONS

AMPK engagement and paradoxical mTORC1 activation and signaling mediate protection against pro-inflammatory stress exerted by caloric restriction in hepatocytes.

Multiple functions of stress granules in viral infection at a glance

Stress granules (SGs) are distinct RNA granules induced by various stresses, which are evolutionarily conserved across species. In general, SGs act as a conservative and essential self-protection mechanism during stress responses. Viruses have a long evolutionary history and viral infections can trigger a series of cellular stress responses, which may interact with SG formation. Targeting SGs is believed as one of the critical and conservative measures for viruses to tackle the inhibition of host cells. In this systematic review, we have summarized the role of SGs in viral infection and categorized their relationships into three tables, with a particular focus on Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. Moreover, we have outlined several kinds of drugs targeting SGs according to different pathways, most of which are potentially effective against SARS-CoV-2. We believe this review would offer a new view for the researchers and clinicians to attempt to develop more efficacious treatments for virus infection, particularly for the treatment of SARS-CoV-2 infection.

Contribution to pathogenesis of accessory proteins of deadly human coronaviruses

Coronaviruses (CoVs) are enveloped and positive-stranded RNA viruses with a large genome (∼ 30kb). CoVs include essential genes, such as the replicase and four genes coding for structural proteins (S, M, N and E), and genes encoding accessory proteins, which are variable in number, sequence and function among different CoVs. Accessory proteins are non-essential for virus replication, but are frequently involved in virus-host interactions associated with virulence. The scientific literature on CoV accessory proteins includes information analyzing the effect of deleting or mutating accessory genes in the context of viral infection, which requires the engineering of CoV genomes using reverse genetics systems. However, a considerable number of publications analyze gene function by overexpressing the protein in the absence of other viral proteins. This ectopic expression provides relevant information, although does not acknowledge the complex interplay of proteins during virus infection. A critical review of the literature may be helpful to interpret apparent discrepancies in the conclusions obtained by different experimental approaches. This review summarizes the current knowledge on human CoV accessory proteins, with an emphasis on their contribution to virus-host interactions and pathogenesis. This knowledge may help the search for antiviral drugs and vaccine development, still needed for some highly pathogenic human CoVs.

Porcine epidemic diarrhea virus activates PERK-ROS axis to benefit its replication in Vero E6 cells

Of the three branches of unfolded protein response (UPR) that were reportedly activated by porcine epidemic diarrhea virus (PEDV), PERK is recently shown to act as an upstream regulator of oxidative response of the cells. However, it remains unknown if and how PERK activation during PEDV infection would result in oxidative stress, and whether activation of PERK and its downstream molecules affect PEDV replication. Here, we demonstrate that infection with the PEDV strain YJH/2015 triggered UPR in Vero E6 cells by activating the PERK/eIF2α pathway and led to significant increase in the expression of proapoptotic protein C/EBP homologous protein (CHOP) and ER oxidoreductase 1 alpha (ERO1α). Inhibition of PERK by short hairpin RNA (shRNA) or GSK2606414 and knockdown of CHOP by small interfering RNA reduced expression of ERO1α and generation of ROS in PEDV-infected cells. Inhibition of ERO1α by shRNA or EN460 decreased PEDV-induced ROS generation. Genetic or pharmacological inhibition of each component of PERK, CHOP, ERO1α, and ROS led to significant suppression of PEDV replication. Collectively, our study provides the first evidence that PEDV manipulates endoplasmic reticulum to perturb its redox homeostasis via the PERK-CHOP-ERO1α-ROS axis in favor of its replication.

Suppression of porcine hemagglutinating encephalomyelitis virus replication by resveratrol

BACKGROUND

Porcine hemagglutinating encephalomyelitis virus (PHEV), a member of the genus Betacoronavirus, is the causative agent of neurological disease in pigs. No effective therapeutics are currently available for PHEV infection. Resveratrol has been shown to exert neuroprotective and antiviral effects. Here resveratrol was investigated for its ability to inhibit PHEV replication in nerve cells and central nervous system tissues.

METHODS

Anti-PHEV effect of resveratrol was evaluated using an in vitro cell-based PHEV infection model and employing a mouse PHEV infection model. The collected cells or tissues were used for quantitative PCR analysis, western blot analysis, or indirect immunofluorescence assay. The supernatants were collected to quantify viral loads by TCID₅₀ assay in vitro. EC50 and CC50 were determined by dose-response experiments, and the ratio (EC50/CC50) was used as a selectivity index (SI) to measure the antiviral versus cytotoxic activity.

RESULTS

Our results showed that resveratrol treatment reduced PHEV titer in a dose-dependent manner, with a 50% inhibition concentration of 6.24 μM. A reduction of > 70% of viral protein expression and mRNA copy number and a 19-fold reduction of virus titer were achieved when infected cells were treated with 10 µM resveratrol in a pre-treatment assay. Quantitative PCR analysis and TCID₅₀ assay results revealed that the addition of 10 μM resveratrol to cells after adsorption of PHEV significantly reduced 56% PHEV mRNA copy number and eightfold virus titer. 10 µM resveratrol treatment reduced 46% PHEV mRNA copy number and fourfold virus titer in virus inactivation assay. Moreover, the in vivo data obtained in this work also demonstrated that resveratrol inhibited PHEV replication, and anti-PHEV activities of resveratrol treatment via intranasal installation displayed better than oral gavage.

CONCLUSION

These results indicated that resveratrol exerted antiviral effects under various drug treatment and virus infection conditions in vitro and holds promise as a treatment for PHEV infection in vivo.

Antiviral effect of lysosomotropic disaccharide trehalose on porcine hemagglutinating encephalomyelitis virus, a highly neurotropic betacoronavirus

Many members of the genus Betacoronavirus are neurotropic viruses that frequently cause serious harm to humans or animals, including highly neurotropic porcine hemagglutinating encephalomyelitis virus (PHEV). Nevertheless, very few approved treatments exist to combat these viruses. Lysosomotropic trehalose, a widely used, nontoxic, natural disaccharide that can traverse the blood-brain barrier, has been proposed as a potential antiviral agent for use in prevention or treatment of betacoronavirus-associated infections. The purpose of this study was to determine if trehalose could inhibit PHEV infection of cells of a mouse central nervous system-derived neuroblastoma cell line in vitro or brain cells in vivo. Our results demonstrated that treatment of PHEV-infected mouse neuroblastoma cells and mice with trehalose reduced viral replication and that these trehalose antiviral effects were dependent on expression of lysosomal protein progranulin. Collectively, these results indicated that trehalose holds promise as a new antiviral agent for use in controlling neurotropic betacoronavirus infections.

The Effects of Swine Coronaviruses on ER Stress, Autophagy, Apoptosis, and Alterations in Cell Morphology

Swine coronaviruses include the following six members, namely porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine delta coronavirus (PDCoV), swine acute diarrhea syndrome coronavirus (SADS-CoV), porcine hemagglutinating encephalomyelitis virus (PHEV), and porcine respiratory coronavirus (PRCV). Clinically, PEDV, TGEV, PDCoV, and SADS-CoV cause enteritis, whereas PHEV induces encephalomyelitis, and PRCV causes respiratory disease. Years of studies reveal that swine coronaviruses replicate in the cellular cytoplasm exerting a wide variety of effects on cells. Some of these effects are particularly pertinent to cell pathology, including endoplasmic reticulum (ER) stress, unfolded protein response (UPR), autophagy, and apoptosis. In addition, swine coronaviruses are able to induce cellular changes, such as cytoskeletal rearrangement, alterations of junctional complexes, and epithelial-mesenchymal transition (EMT), that render enterocytes unable to absorb nutrients normally, resulting in the loss of water, ions, and protein into the intestinal lumen. This review aims to describe the cellular changes in swine coronavirus-infected cells and to aid in understanding the pathogenesis of swine coronavirus infections. This review also explores how the virus exerted subcellular and molecular changes culminating in the clinical and pathological findings observed in the field.

Induction and modulation of the unfolded protein response during porcine deltacoronavirus infection

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogenic coronavirus that has the potential for cross-species infection. Many viruses have been reported to induce endoplasmic reticulum stress (ERS) and activate the unfolded protein response (UPR). To date, little is known about whether and, if so, how the UPR is activated by PDCoV infection. Here, we investigated the activation state of UPR pathways and their effects on viral replication during PDCoV infection. We found that PDCoV infection induced ERS and activated all three known UPR pathways (inositol-requiring enzyme 1 [IRE1], activating transcription factor 6 [ATF6], and PKR-like ER kinase [PERK]), as demonstrated by IRE1-mediated XBP1 mRNA cleavage and increased mRNA expression of XBP1s, ATF4, CHOP, GADD34, GRP78, and GRP94, as well as phosphorylated eIF2α expression. Through pharmacologic treatment, RNA interference, and overexpression experiments, we confirmed the negative role of the PERK-eIF2α pathway and the positive regulatory role of the ATF6 pathway, but found no obvious effect of IRE1 pathway, on PDCoV replication. Taken together, our results characterize, for the first time, the state of the ERS response during PDCoV infection and identify the PERK and ATF6 pathways as potential antiviral targets.

PHEV infection: A promising model of betacoronavirus-associated neurological and olfactory dysfunction

Porcine hemagglutinating encephalomyelitis virus (PHEV) is a highly neurotropic coronavirus belonging to the genus Betacoronavirus. Similar to pathogenic coronaviruses to which humans are susceptible, such as SARS-CoV-2, PHEV is transmitted primarily through respiratory droplets and close contact, entering the central nervous system (CNS) from the peripheral nerves at the site of initial infection. However, the neuroinvasion route of PHEV are poorly understood. Here, we found that BALB/c mice are susceptible to intranasal PHEV infection and showed distinct neurological manifestations. The behavioral study and histopathological examination revealed that PHEV attacks neurons in the CNS and causes significant smell and taste dysfunction in mice. By tracking neuroinvasion, we identified that PHEV invades the CNS via the olfactory nerve and trigeminal nerve located in the nasal cavity, and olfactory sensory neurons (OSNs) were susceptible to viral infection. Immunofluorescence staining and ultrastructural observations revealed that viral materials traveling along axons, suggesting axonal transport may engage in rapid viral transmission in the CNS. Moreover, viral replication in the olfactory system and CNS is associated with inflammatory and immune responses, tissue disorganization and dysfunction. Overall, we proposed that PHEV may serve as a potential prototype for elucidating the pathogenesis of coronavirus-associated neurological complications and olfactory and taste disorders.

Study on the Anti-Adenovirus Mechanism of Sargassum fusiforme

Human adenovirus (HAdV) has a worldwide distribution and remains a major pathogen that leads to infections of the respiratory tract. No specific treatments or vaccines are yet available for HAdV infection. Sargassum fusiforme, an edible seaweed, has attracted a lot of attention for its various bioactivities. S. fusiforme has been reported to exhibit antiviral activity. However, research studies about its anti-HAdV activity are few. In this research, we found that S. fusiforme had low cytotoxicity and possessed anti-human adenovirus type 7 (HAdV7) activity in vitro, and the most effective ingredient was alginate. The time of addition assay demonstrated inhibitory effects that were observed in all life stages of the virus. In addition, we observed that the antiviral activity of alginate against HAdV7 infection might be closely related to the endoplasmic reticulum stress (ERS) pathway. Taken together, these results suggest that S. fusiforme extracts have potential application in the prevention and treatment of HAdV infection.