Antiviral effects of ergosterol peroxide in a pig model of porcine deltacoronavirus (PDCoV) infection involves modulation of apoptosis and tight junction in the small intestine

Research progress of porcine epidemic diarrhea virus S protein

Porcine epidemic diarrhea virus (PEDV) is a single-stranded RNA virus with a capsid membrane that causes acute infectious gastrointestinal disease characterized by vomiting, diarrhea, and dehydration in swine. Piglets are more susceptible to PEDV than adults, with an infection rate reaching 90% and a fatality rate as high as 100%. Moreover, PEDV has a rapid transmission rate and broad transmission range. Consequently, PEDV has caused considerable economic losses and negatively impacted the sustainability of the pig industry. The surface spike (S) glycoprotein is the largest structural protein in PEDV virions and is closely associated with host cell fusion and virus invasion. As such, the S protein is an important target for vaccine development. In this article, we review the genetic variation, immunity, apoptosis-induction function, virulence, vaccine potential, and other aspects of the PEDV S protein. This review provides a theoretical foundation for preventing and controlling PEDV infection and serves as a valuable resource for further research and development of PEDV vaccines.

Epidemiology, pathogenesis, immune evasion mechanism and vaccine development of porcine Deltacoronavirus

Coronaviruses have been identified as pathogens of gastrointestinal and respiratory diseases in humans and various animal species. In recent years, the global spread of new coronaviruses has had profound influences for global public health and economies worldwide. As highly pathogenic zoonotic viruses, coronaviruses have become the focus of current research. Porcine Deltacoronavirus (PDCoV), an enterovirus belonging to the family of coronaviruses, has emerged on a global scale in the past decade and significantly influenced the swine industry. Moreover, PDCoV infects not only pigs but also other species, including humans, chickens and cattles, exhibiting a broad host tropism. This emphasizes the need for in-depth studies on coronaviruses to mitigate their potential threats. In this review, we provided a comprehensive summary of the current studies on PDCoV. We first reviewed the epidemiological investigations on the global prevalence and distribution of PDCoV. Then, we delved into the studies on the pathogenesis of PDCoV to understand the mechanisms how the virus impacts its hosts. Furthermore, we also presented some exploration studies on the immune evasion mechanisms of the virus to enhance the understanding of host-virus interactions. Despite current limitations in vaccine development for PDCoV, we highlighted the inhibitory effects observed with certain substances, which offers a potential direction for future research endeavors. In conclusion, this review summarized the scientific findings in epidemiology, pathogenesis, immune evasion mechanisms and vaccine development of PDCoV. The ongoing exploration of potential vaccine candidates and the insights gained from inhibitory substances have provided a solid foundation for future vaccine development to prevent and control diseases associated with PDCoV.

Gut-brain communication mediates the impact of dietary lipids on cognitive capacity

Cognitive impairment, as a prevalent symptom of nervous system disorders, poses one of the most challenging aspects in the management of brain diseases. Lipids present in the cell membranes of all neurons within the brain and dietary lipids can regulate the cognition and memory function. In recent years, the advancements in gut microbiome research have enabled the exploration of dietary lipids targeting the gut-brain axis as a strategy for regulating cognition. This present review provides an in-depth overview of how lipids modulate cognition via the gut-brain axis depending on metabolic, immune, neural and endocrine pathways. It also comprehensively analyzes the effects of diverse lipids on the gut microbiota and intestinal barrier function, thereby affecting the central nervous system and cognitive capacity. Moreover, comparative analysis of the positive and negative effects is presented between beneficial and detrimental lipids. The former encompass monounsaturated fatty acids, short-chain fatty acids, omega-3 polyunsaturated fatty acids, phospholipids, phytosterols, fungal sterols and bioactive lipid-soluble vitamins, as well as lipid-derived gut metabolites, whereas the latter (detrimental lipids) include medium- or long-chain fatty acids, excessive proportions of n-6 polyunsaturated fatty acids, industrial trans fatty acids, and zoosterols. To sum up, the focus of this review is on how gut-brain communication mediates the impact of dietary lipids on cognitive capacity, providing a novel theoretical foundation for promoting brain cognitive health and scientific lipid consumption patterns.

Anti-α-glucosidase, Anti-proliferative and Anti-enterovirus 71 Activity of Secondary Metabolites Identified from Grifola Frondosa

Grifola frondosa, an edible and medicinal resource, is widely used as functional foods worldwide. To explore bioactive compounds against α-glucosidase, human tumor cells and enterovirus 71 (EV71), eight compounds were isolated from G. frondosa by chromatographic column. Among the isolated compounds, heptadecanoic acid, uridine and adenosine exhibited potent inhibition activity against α-glucosidase, ergosterols and ergosterol-5,8-peroxide showed anti-proliferative activity on tumor cells, while ergosterol and methyl linoleate displayed inhibition against the replication of EV71. Also, to our knowledge, this is the first study to report that fatty acids isolated from G. frondosa show potent inhibition against α-glucosidase and EV71. Further molecular docking results revealed that the active compounds in G. frondosa form hydrogen bonding, hydrophobic interactive and π-stacking with the active sites on the surface of α-glucosidase, CASP3 and VP1 proteins, thus promoting the active compounds to combine with the target protein to form a stable complex, thus playing an antagonistic role. Our results could provide a new active compound and mode of action for G. frondosa to treat diabetes, cancer and EV71-infected patients.

Adamantoyl chloride inhibited replication of the largemouth bass virus via enhanced immunity and inhibition of apoptosis

The largemouth bass virus (LMBV) is a commonly encountered pathogen in aquaculture and presents significant challenges to development of the largemouth bass industry due to the lack of effective treatment methods. Here, the inhibitory potential and underlying mechanisms of adamantoyl chloride (AdCl) against LMBV were assessed both in vitro and in vivo. The results showed that AdCl (IC50 = 72.35 μM) significantly inhibited replication of LMBV in epithelioma papulosum cyprini (EPC) cells. The results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide and cytopathic effect (CPE) assays confirmed that AdCl inhibited replication of LMBV in EPC cells and significantly reduced the CPE effect, respectively. As a potential mechanism, AdCl inhibited apoptosis as determined by fluorescence and transmission electron microscopy. The results of flow cytometry showed that the apoptosis rate was decreased by 69 % in the AdCl-treated group as compared to the LMBV-infected group. Additionally, AdCl inhibited viral release. In vivo, the survival rate was 16.2 % higher in the AdCl-treated group as compared to the LMBV-infected group (26.9 % vs. 10.7 %, respectively). Additionally, the results of quantitative reverse transcription polymerase chain reaction (RT-qPCR) showed that AdCl significantly reduced the viral load of the fish liver, spleen, and kidneys at 3, 6, and 9 days postinfection. In addition, RT-qPCR analysis found that AdCl upregulated expression of immune-related genes to suppress replication of LMBV. Collectively, these results confirmed the anti-LMBV activities of AdCl for use in the aquaculture industry.

Anti-Toxoplasma gondii activity of Trametes versicolor (Turkey tail) mushroom extract

Toxoplasma gondii (T. gondii) infection continues to rise globally in humans and animals with high socioeconomic and public health challenges. Current medications used against T. gondii infection are limited in efficacy, safety, and affordability. This research was conducted to assess the higher fungi extract effect on T. gondii tachyzoites growth in vitro and possibly decipher its mechanism of action. Furthermore, we evaluated the extract's effect on human foreskin fibroblast viability. The methanol extracts of Turkey tail (TT) mushroom was tested against T. gondii tachyzoites growth using an RH-RFP type I strain that expresses red fluorescent protein throughout culture in a dose-dependent manner using a fluorescent plate reader. Similarly, we tested the effect of the extract on host cell viability. We observed that TT extract inhibited tachyzoites growth with a 50% minimum inhibitory concentration (IC_50s), IC₅₀ = 5.98 ± 1.22 µg/mL, and 50% cytotoxic concentration (CC_50s), CC₅₀ ≥ 100 µg/mL. It was discovered that TT extract induced strong mitochondria superoxide and  reactive oxygen species production and disrupted mitochondria membrane potential in T. gondii tachyzoites. Additionally, scanning electron microscopy depicted that TT extract and pyrimethamine (PY) caused a morphological deformation of tachyzoites in vitro. In conclusion, TT methanol extract made up of phytosterols, bioactive sphingolipids, peptides, phenolic acids, and lactones could be a promising source of new compounds for the future development of anti-Toxoplasma gondii drugs. Extracts were non-cytotoxic, even at higher concentrations.

Mucosal immune responses induced by oral administration of recombinant Lactococcus lactis expressing the S1 protein of PDCoV

Porcine deltacoronavirus is an evolving coronavirus that primarily infects the intestine and may lead to intestinal disease in piglets. Up to now, no commercial vaccination is readily accessible to protect against the spread of PDCoV. Lactococcus lactis has been shown to have good immune efficacy and safety and can be used as a genetically engineered vaccine to deliver antigens. In this research, we utilized L. lactis NZ9000 to provide the S1 protein orally and improved the delivery efficiency by connecting the M cell targeting ligand Co1 with the S1 protein of PDCoV in tandem to obtain the recombinant protein S1-Co1. We successfully constructed two recombinant strains capable of expressing PDCoV-S1 and PDCoV-S1-Co1 proteins (i.e., L. lactis NZ9000-S1 and L. lactis NZ9000-S1-Co1), and their immunogenic capacity was evaluated in mice. Our study shows that Lactococcus is an advantageous bacterial live vector vaccine and is anticipated as a potential PDCoV vaccination option.

Co-infection of porcine deltacoronavirus and porcine epidemic diarrhea virus induces early TRAF6-mediated NF-κB and IRF7 signaling pathways through TLRs

Porcine deltacoronavirus (PDCoV) and porcine epidemic diarrhea virus (PEDV) infect the small intestine and cause swine enteric coronavirus disease. The mucosal innate immune system is the first line of defense against viral infection. The modulatory effect of PDCoV and PEDV coinfection on antiviral signaling cascades of the intestinal mucosa has not been reported. Here, we investigate the gene expression levels of pattern recognition receptors, downstream inflammatory signaling pathway molecules, and associated cytokines on the intestinal mucosa of neonatal piglets either infected with a single- or co-infected with PDCoV and PEDV using real-time PCR. The results demonstrate that single-PEDV regulates the noncanonical NF-κB signaling pathway through RIG-I regulation. In contrast, single-PDCoV and PDCoV/PEDV coinfection regulate proinflammatory and regulatory cytokines through TRAF6-mediated canonical NF-κB and IRF7 signaling pathways through TLRs. Although PDCoV/PEDV coinfection demonstrated an earlier modulatory effect in these signaling pathways, the regulation of proinflammatory and regulatory cytokines was observed simultaneously during single viral infection. These results suggested that PDCoV/PEDV coinfection may have synergistic effects that lead to enhanced viral evasion of the mucosal innate immune response.

A Review of Bioactive Compounds against Porcine Enteric Coronaviruses

Pig diarrhea is a universal problem in the process of pig breeding, which seriously affects the development of the pig industry. Porcine enteric coronaviruses (PECoVs) are common pathogens causing diarrhea in pigs, currently including transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV) and swine acute diarrhea syndrome coronavirus (SADS-CoV). With the prosperity of world transportation and trade, the spread of viruses is becoming wider and faster, making it even more necessary to prevent PECoVs. In this paper, the host factors required for the efficient replication of these CoVs and the compounds that exhibit inhibitory effects on them were summarized to promote the development of drugs against PECoVs. This study will be also helpful in discovering general host factors that affect the replication of CoVs and provide references for the prevention and treatment of other CoVs.

Exploration of PDCoV-induced apoptosis through mitochondrial dynamics imbalance and the antagonistic effect of SeNPs

Porcine Deltacoronavirus (PDCoV), an enveloped positive-strand RNA virus that causes respiratory and gastrointestinal diseases, is widely spread worldwide, but there is no effective drug or vaccine against it. This study investigated the optimal Selenium Nano-Particles (SeNPs) addition concentration (2 - 10 μg/mL) and the mechanism of PDCoV effect on ST (Swine Testis) cell apoptosis, the antagonistic effect of SeNPs on PDCoV. The results indicated that 4 μg/mL SeNPs significantly decreased PDCoV replication on ST cells. SeNPs relieved PDCoV-induced mitochondrial division and antagonized PDCoV-induced apoptosis via decreasing Cyt C release and Caspase 9 and Caspase 3 activation. The above results provided an idea and experimental basis associated with anti-PDCoV drug development and clinical use.

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.

Incomplete autophagy promotes the proliferation of Mycoplasma hyopneumoniae through the JNK and Akt pathways in porcine alveolar macrophages

Autophagy is an important conserved homeostatic process related to nutrient and energy deficiency and organelle damage in diverse eukaryotic cells and has been reported to play an important role in cellular responses to pathogens and bacterial replication. The respiratory bacterium Mycoplasma hyopneumoniae has been identified to enter porcine alveolar macrophages, which are considered important immune cells. However, little is known about the role of autophagy in the pathogenesis of M. hyopneumoniae infection of porcine alveolar macrophages. Our experiments demonstrated that M. hyopneumoniae infection enhanced the formation of autophagosomes in porcine alveolar macrophages but prevented the fusion of autophagosomes with lysosomes, thereby blocking autophagic flux and preventing the acidification and destruction of M. hyopneumoniae in low-pH surroundings. In addition, using different autophagy regulators to intervene in the autophagy process, we found that incomplete autophagy promoted the intracellular proliferation of M. hyopneumoniae. We also found that blocking the phosphorylation of JNK and Akt downregulated the autophagy induced by M. hyopneumoniae, but pathways related to two mitogen-activated protein kinases (Erk1/2 and p38) did not affect the process. Collectively, M. hyopneumoniae induced incomplete autophagy in porcine alveolar macrophages through the JNK and Akt signalling pathways; conversely, incomplete autophagy prevented M. hyopneumoniae from entering and degrading lysosomes to realize the proliferation of M. hyopneumoniae in porcine alveolar macrophages. These findings raise the possibility that targeting the autophagic pathway may be effective for the prevention or treatment of M. hyopneumoniae infection.

Medicinal Fungi with Antiviral Effect

Pandemics from various viruses make natural organisms face challenges over and over again. Therefore, new antiviral drugs urgently need to be found to solve this problem. However, drug research and development is a very difficult task, and finding new antiviral compounds is desirable. A range of medicinal fungi such as Ganoderma lucidum and Cordyceps sinensis are widely used all over the world, and they can enhance human immunity and direct anti-virus activities and other aspects to play an antiviral role. Medicinal fungi are used as foods or as food supplements. In this review, the species of medicinal fungi with antiviral activity in recent decades and the mechanism of antiviral components were reviewed from the perspectives of human, animal, and plant viruses to provide a comprehensive theory based on better clinical utilization of medicinal fungi as antiviral agents.

Supplementation of Dietary Quercetin and Vitamin E Promotes the Intestinal Structure and Immune Barrier Integrity in Aged Breeder Hens

In aged animals, the physiological functions of the gastrointestinal tract (GIT) are reduced. Dietary intervention is necessary to re-activate GIT functions. The objective of this study was to investigate the impacts of dietary combination of quercetin (Q) and vitamin E (VE) on the intestinal structure and barrier integrity in aged breeder chickens. A sum of 400 (65-wks-old) Tianfu breeder hens were randomly allotted into four (4) groups with four (4) replicates, and fed with basal diet; basal diet supplemented with 0.4g/kg of Q; basal diet supplemented with 0.2g/kg of VE; and basal diet supplemented with the combination of Q (0.4 g/kg) and VE (0.2 g/kg) for 14 weeks. At the end of the 14^th week, serum and gut segments were collected from eight hens per group for analyses. The results showed that Q+VE exerted synergistic effects on intestinal morphology by promoting villi height and crypt depth (P < 0.05), as well as mitigated the intestinal inflammatory damage of the aged hens, but decreased the concentration of serum D-lactate and diamine oxidase; and increased the levels of secretory immunoglobulin A (sIgA) and Mucin-2 mRNA (P < 0.05). Furthermore, the mRNA expression of intestinal tight junction proteins including occludin, ZO1, and claudin-1 was increased by Q+VE (P < 0.05). Moreover, Q+VE decreased the mRNA expression of the pro-inflammatory genes (TNF-α, IL-6, and IL-1β), and increased the expression of anti-inflammatory genes (IL-10 and IL-4) (P < 0.05). These results were consistent with the mRNA expression of Bax and Bcl-2. In addition, Q+VE protected the small intestinal tract from oxidative damage by increasing the levels of superoxide dismutase, total antioxidant capacity, glutathione peroxidase, catalase (P < 0.05), and the mRNA expression of SOD1 and GPx-2. However, Q+VE decreased malondialdehyde levels in the intestine compared to the control (P < 0.05). These results indicated that dietary Q+VE improved intestinal function in aged breeder hens, by protecting the intestinal structure and integrity. Therefore, Q+VE could act as an anti-aging agent to elevate the physiological functions of the small intestine in chickens.

Structure and Biological Activity of Ergostane-Type Steroids from Fungi

Mushrooms are known not only for their taste but also for beneficial effects on health attributed to plethora of constituents. All mushrooms belong to the kingdom of fungi, which also includes yeasts and molds. Each year, hundreds of new metabolites of the main fungal sterol, ergosterol, are isolated from fungal sources. As a rule, further testing is carried out for their biological effects, and many of the isolated compounds exhibit one or another activity. This study aims to review recent literature (mainly over the past 10 years, selected older works are discussed for consistency purposes) on the structures and bioactivities of fungal metabolites of ergosterol. The review is not exhaustive in its coverage of structures found in fungi. Rather, it focuses solely on discussing compounds that have shown some biological activity with potential pharmacological utility.

Ergosterol Peroxide Inhibits Porcine Epidemic Diarrhea Virus Infection in Vero Cells by Suppressing ROS Generation and p53 Activation

Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus that causes severe watery diarrhea in piglets with high morbidity and mortality, resulting in serious economic losses to the farming industry. Ergosterol peroxide (EP) is a sterol with diverse biological activities including antiviral activity. In this study, we explored whether EP extracted from the fruiting body of the mushroom Cryptoporus volvatus had the potential to inhibit PEDV infection in Vero cells. The results revealed that EP had a remarkable inhibitory effect on PEDV infection. It could significantly inhibit multiple stages of the PEDV life cycle, including internalization, replication and release, and could directly inactivate PDCoV infectivity. However, it did not affect PEDV attachment. Furthermore, EP alleviated PEDV-induced apoptosis and mitigated the decrease in mitochondrial membrane potential caused by PEDV infection. It suppressed ROS generation and p53 activation caused by PEDV infection. The ROS scavenger N-acetyl-l-cysteine (NAC) and the p53 specific inhibitor Pifithrin-α (PFT-α) suppressed PEDV-induced apoptosis and impeded viral replication, suggesting that ROS and p53 play an important role in PEDV-induced apoptosis and viral replication. Collectively, EP can prevent PEDV internalization, replication and release, possesses the ability to directly inactivate PEDV, and can inhibit PEDV-induced apoptosis by interfering with PEDV-induced ROS production and p53 activation. These findings highlight the therapeutic potential of EP against PEDV infection.

An Updated Review of Porcine Deltacoronavirus in Terms of Prevalence, Pathogenicity, Pathogenesis and Antiviral Strategy

The recent experience with SARS-COV-2 has raised our alarm about the cross-species transmissibility of coronaviruses and the emergence of new coronaviruses. Knowledge of this family of viruses needs to be constantly updated. Porcine deltacoronavirus (PDCoV), a newly emerging member of the genus Deltacoronavirus in the family Coronaviridae, is a swine enteropathogen that causes diarrhea in pigs and may lead to death in severe cases. Since PDCoV diarrhea first broke out in the United States in early 2014, PDCoV has been detected in many countries, such as South Korea, Japan and China. More importantly, PDCoV can also infect species other than pigs, and infections have even been reported in children, highlighting its potential for cross-species transmission. A thorough and systematic knowledge of the epidemiology and pathogenesis of PDCoV will not only help us control PDCoV infection, but also enable us to discover the common cellular pathways and key factors of coronaviruses. In this review, we summarize the current knowledge on the prevalence, pathogenicity and infection dynamics, pathogenesis and immune evasion strategies of PDCoV. The existing anti-PDCoV strategies and corresponding mechanisms of PDCoV infection are also introduced, aiming to provide suggestions for the prevention and treatment of PDCoV and zoonotic diseases.

Porcine deltacoronavirus infection is inhibited by Griffithsin in cell culture

Porcine deltacoronavirus (PDCoV) is an emerging porcine enteric coronavirus that causes severe diarrhea in piglets and results in serious economic losses. There are no effective vaccines and antiviral drugs to prevent and treat PDCoV infection currently. Griffithsin (GRFT) is a lectin with potent antiviral activity against enveloped viruses because of its ability to specifically bind N-linked high-mannose oligosaccharides. GRFT has been reported to possess antiviral activity against severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and porcine epidemic diarrhea virus (PEDV). Here, we first confirmed the antiviral activity of GRFT against PDCoV in vitro. The infected cells (%) and virus titers were significantly decreased at concentration 1 μg/mL or above of GRFT. Time-course experiments revealed that GRFT inhibits PDCoV infection at the adsorption and penetration step. GRFT binding to PDCoV spike (S) protein on the surface wraps the virus and blocks its entry. The outstanding antiviral potency indicates that GRFT has the potential value as a candidate drug for the prevention and treatment of PDCoV infection.