Porcine epidemic diarrhoea virus: a comprehensive review of molecular epidemiology, diagnosis, and vaccines

Epidemiological investigation, isolation, and pathogenicity of porcine epidemic diarrhea virus subtype G2c in Sichuan province

Continued outbreaks of porcine epidemic diarrhea are causing serious economic losses to the swine industry in China. To monitor the prevalence, genetic mutations, and pathogenicity of porcine epidemic diarrhea virus (PEDV), 172 samples were collected from eight cities in Sichuan Province from 2020 to 2022. RT-PCR analysis revealed that 25.0% (43/172) of samples were positive for PEDV. Phylogenetic analysis of 17 S gene sequences (encoding the spike protein) showed that G2c was the main genotype circulating in Sichuan. One strain, Leshan-s-2020 (G2a), was identified as a recombinant resulting from inter-lineage recombination between the KM609212/LYG/2015 (G2a) and MianYang-s-2020 (G2a) strains in the S2 domain. In addition, the G2c strain YB2201, which was highly virulent in 4-day-old piglets, was successfully isolated. The results of this study enrich our understanding of the epidemiology of PEDV, the genetic characteristics and pathogenicity of the PEDV strains circulating in China, and the role of recombination in their evolution. These findings may contribute to the development of antigen detection reagents and vaccines.

Swine interferon-induced transmembrane proteins inhibit porcine epidemic diarrhea virus replication

Porcine epidemic diarrhea (PED) caused by porcine epidemic diarrhea virus (PEDV) has significantly harmed the global pig industry economically. Interferons can induce the expression of interferon-stimulated genes (ISGs) that encode various natural antiviral immune effectors. Notably, swine interferon-induced transmembrane proteins (SwIFITMs) have not been thoroughly investigated in the context of PEDV. In the present research, we explored the anti-PEDV effects of SwIFITMs. Both interferon and PEDV were found to upregulate swine IFITM mRNA levels. Swine IFITM knockdown results showed that SwIFITM1a, -1b, and -2 most significantly reduced PEDV replication. By overexpressing SwIFITMs and establishing a SwIFITM-expressing Vero cell line, we identified SwIFITM2 as having the most pronounced anti-PEDV effect. SwIFITM2 inhibited PEDV entry phase. Additionally, SwIFITM2 interacted with PEDV S2 and N proteins in a dose-dependent manner. Furthermore, it exhibited high co-localization with caveolin-1, while demonstrating the lowest co-localization ratio with clathrin. Upon infection with PEDV, the co-localization of caveolin-1 and PEDV S2 or N protein significantly increased compared with control in the presence of SwIFITM2, indicating that SwIFITM2 may play an antiviral role by confining PEDV within caveolin-1. This study elucidates the anti-PEDV mechanisms of SwIFITMs, providing critical insights into their potential roles in viral pathogenesis and host defense.

TOLLIP inhibits the replication of PEDV by autophagic degradation of Nsp9

Selective autophagy plays a crucial role in innate antiviral immunity by targeting essential viral components and host factors necessary for virus propagation. Among these factors, the nonstructural protein 9 (Nsp9) of Porcine Epidemic Diarrhea Virus (PEDV) is required for viral replication. However, the host factors regulating Nsp9 have remained elusive. In our study, we discovered that Nsp9 undergoes degradation through selective autophagy. Using coimmunoprecipitation combined with mass spectrometry analysis, we identified Toll-interacting protein (TOLLIP) as an autophagy cargo receptor binding to Nsp9 and facilitating its autophagic degradation. Additionally, we found that TOLLIP interacts with LC3A, LC3C, and GABARAPL1. Further investigations revealed that Nsp9 specifically enhances the binding of TOLLIP to LC3A, rather than LC3C or GABARAPL1. Importantly, TOLLIP promotes the engulfment of Nsp9 by LC3A-coated autophagosomes and mediates Nsp9 trafficking to lysosomes, ultimately leading to LC3A-dependent degradation of Nsp9. Consequently, TOLLIP suppresses PEDV replication. Overall, our findings highlight the role of TOLLIP in connecting viral proteins to LC3A-dependent autophagosome, emphasizing its significance in combating viruses through selective autophagy.

Induction of Immune Responses in Mice and Newborn Piglets by Oral Immunization with Recombinant Lactococcus lactis Expressing S1 and M Proteins of Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea (PED) is a severe gastrointestinal disease caused by the porcine epidemic diarrhea virus (PEDV), a virus that spreads through the intestinal tract, leading to significant economic losses in the global swine industry. Therefore, compared to traditional injection method, developing vaccines that effectively stimulate the mucosal immune system to induce a protective immune response is crucial for PED prevention. This study evaluated the immunogenicity of recombinant Lactococcus lactis (L. lactis) strains expressing the PEDV S1 and M proteins (MG1363/pMG36e-S1 and MG1363/pMG36e-M) via oral administration in BALB/c mice and neonatal piglets, assessing cellular, humoral, and mucosal immune responses in the host. The results demonstrated that the recombinant strains significantly stimulated lymphocyte proliferation in mice and increased the proportion of CD3+, CD4+, and CD3+, CD8+ double-positive cells in the spleens of mice and the peripheral blood of piglets (p < 0.05). Furthermore, the recombinant strains significantly increased serum IgG, IgA, and mucosal SIgA levels in piglets (p < 0.05). Meanwhile, serum cytokine levels, including IL-4 and IFN-γ, were significantly elevated in piglets when compared to the control group (p < 0.05). In conclusion, the recombinant L. lactis demonstrated promising potential as a novel live vector vaccine against PEDV.

POLM inhibits porcine epidemic diarrhea virus replication by degrading multiple viral structural proteins

Porcine epidemic diarrhea, as a porcine epidemic diarrhea virus (PEDV)-induced infectious intestinal condition typified by diarrhea, emesis, dehydration, and anorexia, leads to death rates as high as 100% among suckling piglets. Given the existing commercial vaccines, it is essential to study host-virus interactions and formulate efficient anti-viral regimes. This study concerned a host factor POLM (a DNA polymerase family member) that exerts an anti-viral effect against PEDV proliferation. Our results indicated that POLM expression was increased following PEDV infection and was regulated by the transcription factor FOXA1. In addition, our findings indicated that POLM targeted and degraded PEDV structural proteins (N, S2, and M) by the autophagy pathway to inhibit PEDV proliferation. POLM could recruit the E3 ubiquitination ligase MARCH8 for N, S2, and M protein ubiquitination, which was subsequently recognized by p62, a cargo receptor, for translocation to the autophagic lysosome, therefore degrading the N, S2, and M proteins and preventing PEDV proliferation. In summary, we showed a novel therapeutic target for combating PEDV, i.e., using the POLM-MARCH8-p62-autophagosome pathway to degrade the PEDV N, S2, and M proteins.IMPORTANCEPEDV is a coronavirus that causes high mortality in piglets, which poses significant economic damage to swine farming. During PEDV infection, the host cells may promote the natural anti-viral immune response to suppress viral replication through a variety of potential host factors. In this study, we found upregulation of a host factor POLM by FOXA1 (a transcription factor) during PEDV infection. It was indicated that POLM could be a new anti-viral protein against the PEDV replication, which interacted with MARCH8 (an E3 ubiquitin ligase) and p62 (a cargo receptor) to facilitate the PEDV N, S2, and M protein degradation via the autophagy process. Apart from elucidating a previously unidentified anti-viral function of POLM, this study also provides a novel perspective for studying host anti-viral factors that act as regulators of anti-PEDV protein degrading pathways.

Bacteriophage M13KE as a nanoparticle platform to display and deliver a pathogenic epitope: Development of an effective porcine epidemic diarrhoea virus vaccine

Porcine epidemic diarrhoea virus (PEDV) is a porcine enteric coronavirus, outbreaks and epidemics of which have caused huge economic losses to the livestock industry. The disadvantage of existing PEDV vaccines is that the unstable efficacy and high cost limit their widespread use. Therefore, there is an urgent need to develop a recombinant transgenic vaccine candidate for PEDV. In this study, three linear epitopes on the PEDV spike (S) were screened using peptide scanning. The screened epitopes were linked to targeting peptides for lung and intestinal epithelial cells, respectively, and displayed on the M13KE phage to form recombinant phage nanoparticles. Active immunisation experiments showed that a single B-cell epitope delivered by M13KE phage nanoparticles induced the production of specific neutralising antibodies against PEDV in mice. After PEDV stimulation, the immunised mice had significantly higher levels of interferon-γ (IFN-γ) than the control group. Simultaneously, PEDV stimulation caused lymphocyte activation and proliferation in the immunised mice, which is a typical immune response to viral infections. These results suggest that a single linear antigenic epitope delivered by M13KE phage nanoparticles induces significant humoral and cellular immune responses. The constructed recombinant phage nanoparticles are expected to be potential vaccine candidates for PEDV.

Towards developing multistrain PEDV vaccines: Integrating basic concepts and SARS-CoV-2 pan-sarbecovirus strategies

Porcine epidemic diarrhea virus (PEDV) is a major pathogen impacting the global pig industry, with outbreaks causing significant financial losses. The genetic variability of PEDV has posed challenges for vaccine development since its identification in the 1970s, a problem that intensified with its global emergence in the 2010s. Since current vaccines provide limited cross-protection against PEDV strains, and the development of multistrain PEDV vaccines remains an underexplored area of research, there is an urgent need for improved vaccine solutions. The rapid development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines and ongoing pan-sarbecovirus vaccine research, have demonstrated the potential of next-generation vaccine platforms and novel antigen design strategies. These advancements offer valuable insights for the development of multistrain PEDV vaccines. This review summarizes key aspects of PEDV virology and explores multistrain vaccine development considering SARS-CoV-2 vaccine innovations, proposing a framework for developing next-generation PEDV vaccine solutions.

BTG3 inhibits porcine epidemic diarrhea virus replication by promoting viral S2 protein degradation through the autophagy and proteasome pathways

BTG3, which belongs to the BTG/Tob gene family, is involved in various physiological processes. Infection with porcine epidemic diarrhea virus (PEDV), an alphacoronavirus, is associated with high mortality rates among piglets, contributing to major economic losses. This study elucidated a novel mechanism through which BTG3 suppresses PEDV replication. Endogenous BTG3 protein expression was upregulated in PEDV-infected host cells. PEDV replication was suppressed upon BTG3 overexpression but enhanced upon BTG3 knockdown. Additionally, BTG3 inhibited viral proliferation by targeting and degrading the S2 subunit of the PEDV spike (S) protein through both autophagy and proteasome pathways. BTG3 interacted and co-localized with the S2 protein, promoting S2 protein degradation through the recruitment of the cargo receptor NDP52 and the E3 ubiquitin ligase MARCHF8. In summary, this study elucidated a novel antiviral mechanism in which the host BTG3 targeted the viral S2 protein to inhibit PEDV proliferation through autophagy and proteasome pathways. These findings indicate that BTG3 is a potential novel target for the prevention and control of PEDV.

Porcine epidemic diarrhea coronavirus infection activates caspase-8 to enhance innate immunity by blocking CYLD-mediated deubiquitination of RIG-I

Caspase-8 is best known as an initiator caspase that induces apoptosis. However, recent studies suggest that caspase-8 can modulate innate antiviral immunity in a context-dependent manner. Porcine epidemic diarrhea virus (PEDV), a coronavirus that rapidly replicates in porcine intestinal epithelial cells, triggers apoptosis, in part through caspase-8 activation. In this study, we investigated the role of caspase-8 activation in regulating antiviral responses in IPEC-DQ cells, a porcine intestinal epithelial cell line. We found that inhibition of caspase-8 activity using Z-Vad (a pan-caspase inhibitor) and Z-IETD (a caspase-8-specific inhibitor) reduced PEDV-induced phosphorylation of TBK1, IRF3, and the p65 subunit of NF-κB, and inhibited the nuclear translocation of p65 and IRF3. Similarly, caspase-8 knockout inhibited PEDV-induced phosphorylation of p65, IRF3, and TBK1, as well as RIG-I expression and IRF3- and NF-κB-driven luciferase activity. Notably, inhibition of caspase-3 with Z-DEVD had no effect on PEDV-induced TBK1 and IRF3 phosphorylation. Mechanistically, caspase-8 cleaves and inactivates CYLD, a deubiquitinase that removes K63-linked ubiquitin from RIG-I. Caspase-8 knockout and Z-Vad blocked PEDV-induced RIG-I K63 ubiquitination. While Z-Vad inhibited cleavage of the viral N protein and promoted PEDV replication, neither Z-IETD nor caspase-8 knockout affected N protein cleavage or virus replication. Our results suggest that caspase-8 activation enhances innate antiviral immunity in PEDV-infected intestinal epithelial cells without affecting viral replication, likely due to viral manipulation of IFN signaling.

Characterization of a cell-adapted completely attenuated genotype GIIa porcine epidemic diarrhea virus strain

Porcine epidemic diarrhea virus (PEDV) has caused significant harm to the global pig industry since its discovery. In this study, a highly pathogenic strain of GIIa PEDV CH/HBXT/2018, isolated previously, was continuously passaged in Vero cells up to passage (P)240, resulting in a completely attenuated virus. The proliferation characteristics of different passages of the strain in Vero cells, pathogenicity in newborn piglets, and mutations in S gene sequence indicated that as the passage number increased, the replication efficiency of PEDV in Vero cells gradually improved, with a more pronounced cytopathic effect. However, its pathogenicity in piglets decreased progressively, evident as reduced viral loads in the feces and intestinal tissues, less-severe clinical symptoms, less-severe histopathological damage, and lower antigen expression in intestinal tissues. At P240, the strain was completely attenuated. A sequence analysis revealed 17 amino acid mutations in the structural spike protein, which may have contributed to the biological changes observed at P240. Furthermore, compared with P10, the strain's dependence on trypsin had decreased significantly at P200. A differential transcriptomic analysis revealed 1712 differentially expressed genes (DEGs) between the P10 and P200 infection groups, of which 458 were upregulated and 1254 downregulated. These DEGs were primarily involved in signaling pathways such as cytokine-cytokine receptor interaction, inflammatory response, and MHC protein complex. Our findings provide valuable insights into the mechanisms of PEDV attenuation and should facilitate the development of live vaccines.

First detection and molecular characterization of porcine epidemic diarrhea virus (PEDV) in India: evidence of a new variant in Karnataka

BACKGROUND

Porcine epidemic diarrhea (PED) is a significant pig disease causing high mortality in suckling pigs and high morbidity across all age groups. It is highly prevalent in Southeast Asia, posing a threat of transboundary transmission to India. Although antibodies were detected as early as 2003 in Assam, there was no evidence of viral detection or molecular characterization until this study. This study reports the first clinical outbreak of PED in India, followed by the detection and genetic characterization of PED virus (PEDV) during 2022-23.

METHODS

The outbreak was characterized, and fecal samples (n = 21) were collected from affected pigs. These samples were screened for PEDV using RT-PCR, targeting the N, S, and M genes. Serosurveillance was conducted in eight districts, and serum samples (n = 339) were tested for PEDV antibodies using ELISA. Partial N, S, and M gene sequencing, followed by phylogenetic analysis using MEGA v11.0.13, was performed to identify the prevailing genotype and variations in the coding region.

RESULTS

This study identified the first clinical outbreak of PEDV in India, with morbidity rates of 55-57.1% and symptoms including yellow watery diarrhea, vomiting, and abdominal pain. PEDV was confirmed in 17 of 21 fecal samples by amplifying the N, S, and M genes. Serosurveys showed seropositivity in Mandya (2.8%), Bengaluru Rural (6.6%), and Kolar (21.6%), districts indicating PEDV circulation in the state of Karnataka, India. The phylogenetic analysis of the S and M genes placed our study sequences within the Genotype 2a (G2a) clade, aligning with other known G2a strains. In contrast, the phylogenetic tree of the N gene clustered our sequences within the Genotype 1a (G1a) clade suggesting potential recombination. The Indian PEDV strains clustered with strains of China, with unique amino acid substitutions in the S gene, particularly in the receptor binding region.

CONCLUSION

This study reports the first clinical outbreak of PED in India and identifies the circulating genotype of PEDV. The study emphasizes the need for large-scale surveillance studies to understand the disease's status. Understanding PEDV's genetic diversity and evolution is essential to develop area-specific vaccines to mitigate the disease impact on India's pig population.

Field Investigation Evaluating the Efficacy of Porcine Reproductive and Respiratory Syndrome Virus Type 2 (PRRSV-2) Modified Live Vaccines in Nursery Pigs Exposed to Multiple Heterologous PRRSV Strains

This study was conducted to evaluate the protective efficacy of modified live vaccines (MLVs) against porcine reproductive and respiratory syndrome (PRRS) in nursery pigs in a worst case scenario where MLV does not match the genetic profile of the field isolate, different MLVs are used for sows and piglets, and piglets are naturally exposed to genetically distinct heterologous PRRS virus (PRRSV) isolates. We divided 76,075, 2-week-old piglets from a seropositive sow herd vaccinated with US1-MLV into four groups. US1-MLV, US2-MLV, and US3-MLV groups were vaccinated with PRRSV-2 MLV including Ingelvac® PRRS MLV (Boehringer Ingelheim, Ingelheim am Rhein, Germany), HP-PRRSV-2 based MLV (Harbin Veterinary Research Institute, CAAS, Harbin, China), and Prime Pac® PRRS (MSD Animal Health, Rahway, NJ, USA), respectively. The NonVac group was left unvaccinated. At 0, 14, 28, and 56 days post-vaccination (DPV), sera were assayed for the presence of PRRSV-specific antibodies using ELISA and serum neutralization (SN), and PRRSV RNA using PCR. Average daily gain (ADG) and survival rates were compared between treatment groups. The results demonstrated vaccinated groups significantly improved in ADG compared to the non-vaccinated control group. Only US1-MLV and US3-MLV were able to significantly reduce mortality associated with field PRRSV infection in nursery pigs. Pigs vaccinated with US3-MLV displayed significantly lower mortality and higher ADG compared to all other groups. Field isolates were isolated and genetically compared to all three MLV vaccines at the start of the trial. The MLV with closest genetic similarity to the field isolate was US2-MLV by ORF5 gene comparison. This provided the lowest protection judging by ADG improvement and mortality reduction, as compared to US1-MLV and US3-MLV. Separately, strains of Thai PRRSV-2 isolates collected in 2017, 2019, and 2020 in the study area were investigated for evolutionary changes. Over time, we observed a shift in PRRSV-2 isolates from lineage 8.7 to lineage 1. The field isolates found shared 82.59-84.42%, 83.75-85.74%, and 84.25-85.90% nucleotide identity with the US1-MLV, US3-MLV and US2-MLV based vaccine, respectively. Our findings suggest genetic similarity between field viruses and vaccine strains should not be used as a predictor of field performance. We found that zootechnical performance of piglets was best in US3-MLV, despite sows being treated with a different vaccine The results also support that different MLVs can be used at different stages of production. Finally, we concluded that the shift from lineage 8.7 to lineage 1 was due to shifts in the worldwide prevalence of PRRSV isolates during that period of time and not due to vaccine recombination between isolates. Overall, MLV vaccine selection should be based on production performance and safety profile.

Duplex qPCR for detecting and differentiating porcine epidemic diarrhea virus GI and GII subtypes

Introduction

Porcine epidemic diarrhea virus (PEDV) is a pathogen that causes a highly contagious intestinal disease in pigs, which causes significant economic losses to the pig industry worldwide. PCR is the most commonly used technique for PEDV diagnosis in practical clinics, however, reported works still suffer from shortcomings, for example, most of them cannot differentiate GI and GII subtypes, they suffer from low sensitivity, and some primer sequences are no longer able to match the mutant strains.

Methods

To address these issues, we conducted a comprehensive analysis by comparing the sequences of the PEDV S protein in the existing NCBI database with a recently isolated epidemic strain of PEDV, named SX0818-2022, of subtype GIIa from Shanxi, China. The conserved sequences of GI and GII subtypes were retrieved to design the primers and probe. Leveraging this information, we developed a TaqMan probe-based quantitative real-time PCR (qPCR) assay that is uniquely tailored to detect both PEDV GI and GII subtypes.

Results

Additionally, this qPCR can identify PEDV GI and GII subtypes with high sensitivities of 90 copies/μL and 40 copies/μL, respectively (refers to the number of copies of the DNA target per microliter of template in the reaction system), much higher than the previously reported works and especially suitable for early diagnosis and prevention. Besides, excellent specificity and repeatability of the duplex qPCR were verified, thus supporting its potential applications in practical clinics.

Discussion

Therefore, this work presents a promising tool for PEDV diagnosis, prevention, and control.

Upregulation of porcine epidemic diarrhea virus (PEDV) RNA translation by the nucleocapsid protein

The role of coronaviral nucleocapsid (N) protein in regulating viral translation remains poorly understood. Here, we showed that the N protein of porcine epidemic diarrhea virus (PEDV) enhances the translation of both virus-like genomic RNA (gRNA) and messenger RNA. Further characterization of the gRNA translation upregulation showed that the N-terminal domain (NTD) + Linker region plays a major role. The stem-loop 1 in the 5' untranslated region (UTR) and the budged stem loop in the 3'UTR are required for viral translation upregulation by PEDV N protein. The signaling kinase Akt exists in three isoforms. We found that Akt1 enhances viral gRNA translation upregulation by the N protein dependent on its kinase activity. We further showed an interaction between Akt1 and PEDV N, that is abolished by the NTD + Linker region. This suggested that the enhancing effect of Akt1 on translation upregulation by the N protein does not require interaction between these two proteins.

Surveillance of coronavirus in wild mammals seized and rescued by the National Forest and Wildlife Service of Peru

Coronaviruses are common around the world and infect a wide variety of animals, including domestic and wild ones. They are characterized by causing respiratory, enteric, hepatic, and neurological diseases of varying severity, from asymptomatic to severe. Wild animals play a crucial role in this group of viruses since they can act as hosts or reservoirs for pathogenic species of humans and domestic animals. The purpose of this study was to molecularly identify coronaviruses present in wild mammals seized and rescued by the National Forestry and Wildlife Service (SERFOR) of Peru. We molecularly analyzed tracheal and rectal swabs from 90 wild mammals seized and/or rescued by SERFOR, partially amplifying the coronavirus RdRp gene. Ten of the 90 animals studied (11.1%) were positive only for Alphacoronavirus. These were non-human primates (Aotus sp., Sapajus apella, and Saimiri sciureus), the crab-eating raccoon (Procyon cancrivorus), and the South American sea lion (Otaria flavescens). The partial sequence analysis of the RdRp gene revealed that nine sequences belonged to the Pedacovirus subgenus and shared 99.1% nucleotide identity with the porcine epidemic diarrhea virus (PEDV), and only one sequence belonged to the Tegacovirus subgenus and shared 95.6% identity with the Feline coronavirus (FCoV). The results show that various wild mammal species from Peru can act as hosts for coronaviruses capable of infecting domestic species. Due to this, it is necessary to implement measures that help us identify the genera and species of coronaviruses in these species to prevent and contain future epidemics or pandemics resulting from the high rate of recombination and mutation of this virus.

The development of a lateral flow immunochromatographic test strip for measurement of specific IgA and IgG antibodies level against porcine epidemic diarrhea virus in pig milk

Porcine epidemic diarrhea virus (PEDV) causes severe enteric disease and high mortality in neonatal piglets, leading to significant economic losses in the swine industry. Considering that passive lactogenic immunity is crucial for preventing infection in piglets, necessitating a rapid and accurate tool to measure immunity levels. This study aims to develop a lateral flow immunochromatographic strip (LFICS) to assess IgA and IgG antibodies in colostrum and milk, using PEDV S protein. The performance of LFICS was compared to viral neutralization (VN) and enzyme-linked immunosorbent assay (ELISA) as reference methods, with a visual scoring system applied for field monitoring. Colostrum (n = 82) and milk (n = 106) samples were analyzed, showing strong correlation with reference methods and no cross-reactivity with other pig pathogens. The LFICS exhibited high relative sensitivity (Se) and specificity (Sp), with colostrum showing 98.73% Se and 66.67% Sp for IgA, and 96.15% Se and 75.00% Sp for IgG. Milk demonstrated 95.60% Se and 80.00% Sp for IgA, and 84.88% Se and 85.00% Sp for IgG. These findings indicate that the LFICS is a reliable, simple, and rapid method for measuring PEDV-specific IgA and IgG levels, offering valuable support for monitoring herd immunity and evaluating vaccination programs.

Field-deployable porcine epidemic diarrhea virus diagnostics utilizing CRISPR-Cas13a

Porcine epidemic diarrhoea virus (PEDV), a pathogenic microorganism that induces epidemic diarrhoea in swine, causes substantial economic damage to swine-farming nations. To prevent and control PEDV infections, the availability of upgraded and rapid virus detection techniques is crucial. The clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas)13a system, namely, programmability of CRISPR RNA (crRNA) and "collateral" promiscuous RNase activity of Cas13a after target RNA identification. In this study, we aimed to develop a recombinase polymerase amplification (RPA)-based CRISPR-Cas13a approach for PEDV diagnosis for the first time. The results showed that up to 10 copies of the target PEDV DNA standard/µL were detected after 40 min at 37 °C. PEDV detection exhibited remarkable specificity compared to that of other selected pathogens. Additionally, this RPA-based CRISPR-Cas13a approach could be used to clinical samples, with similar performance to that of reverse transcription-quantitative polymerase chain reaction (RT - qPCR). The results of our proposed approach were visualized using either lateral flow strips or fluorescence for field-deployable viral diagnostics, thereby facilitating its use in endemic regions. Overall, our proposed approach showed good reliability, sensitivity, and specificity, suggesting that it is applicable for detecting other viruses in diagnosing diseases and inspecting food safety.

Prevalence and genetic diversity of porcine epidemic diarrhea virus in Southwest China during 2020-2022

Porcine epidemic diarrhea (PED), caused by porcine epidemic diarrhea virus (PEDV), has been frequently occurring in the southwestern region of China over the past few years, continuously affecting the development of the swine industry. However, the genetic diversity and prevalence of PEDV strains circulating in the swine population in southwestern China in recent years have not been well studied. To address this gap, a total of 478 clinical samples were collected from 125 pig farms experiencing piglet diarrhea in 18 cities in southwestern China. The detection results revealed that 227 out of 478 samples tested positive for PEDV nucleic acid, with a positivity rate of 47.49%. Complete S gene sequences of 28 PEDV strains were obtained and classified into four subgroups, G1-a subgroup (classical strain), G1-b subgroup (S-INDEL), and two G2 subgroups (G2-a and G2-b), accounting for 17.86% (5/28), 3.57% (1/28), 35.71% (10/28), 42.86% (12/28) of the total sequenced strains, respectively. The coexistence of multiple genotypes indicates the complex genetic background and prevalence of PEDV in southwest China. Amino acid comparisons of the S proteins showed that the 28 PEDV strains sequenced in the study showed different patterns of variation in the epitope domains compared to vaccine strains belonging to different genotypes and contained many unique amino acid mutations compared to the reference strains, which might lead to immune escape of PEDV. The complex epidemiology of PEDV with multiple subgroups co-circulating in Southwest China underscores the importance of selecting appropriate vaccine strains based on locally prevalent strains and the ongoing need for epidemiological surveillance of PEDV. The emergence of new variant strains also highlights the urgency of developing updated vaccines, and effective management practices remain crucial for controlling PED outbreaks in pig farms.

IPEC-J2 Autophagy Induced by TLR4 and NSP6 Interactions Facilitate Porcine Epidemic Diarrhea Virus Replication

Autophagy is an important cellular response against intracellular pathogens. However, some viruses have evolved mechanisms to hijack this defensive process to provide favorable conditions for virus replication in host cells. The porcine epidemic diarrhea virus (PEDV) has been shown to alter autophagy pathways; however, it is still unknown through which receptors PEDV induces autophagy in IPEC-J2 cells, whether autophagy facilitates PEDV replication, and which functional domains of PEDV proteins are primarily responsible for inducing autophagy. Here, we found that PEDV infection induces autophagy in host cells via distinct and uncoupled molecular pathways. RNA-seq technology was used to analyze the expression patterns of intracellular genes in PEDV-infected IPEC-J2 cells using transcriptomics. The results demonstrate that PEDV triggers autophagy via the cellular pathogen receptor TLR4 and the AKT-mTOR pathway. As evidenced by autophagosome detection, PEDV infection increases autophagosomes and light chain 3 (LC3)-II as well as downregulated AKT-mTOR phosphorylation. Our study revealed that the binding of the viral protein NSP61-2C (56-151aa) to TLR4 triggers autophagy and inactivates the AKT-mTOR pathway, both of which are critical for facilitating PEDV infection. Through screening and analysis, TLR4 was found to be a key gene involved in PEDV-induced autophagy. The screening of the key functional domains of NSP6 (56-151aa) for their ability to induce autophagy in IPEC-J2 cells provided a basis for the in-depth analysis of the pathogenic mechanism of PEDV infection-induced autophagy and promotion of self-replication and also provided an important target for the study of PEDV antiviral drugs. In conclusion, we elucidated that the PEDV infection of IPEC-J2 cells could induce autophagy and found that PEDV could use autophagy to promote its own replication.

Neutralizing VHH Antibodies Targeting the Spike Protein of PEDV

Porcine epidemic diarrhea virus (PEDV) is a highly contagious coronavirus that infect pigs' intestinal epithelial cells, causing high morbidity and mortality. Due to the rapid mutation of PEDV, vaccine efficacy is uncertain, prompting exploration of alternative treatments. Nanobodies, also known as variable heavy chain domains of heavy chain-only antibodies (VHHs), offer significant potential in biomedical applications due to their small size and high specificity. In this study, yeast two-hybrid technology was employed to screen for eight specific VHH sequences targeting the PEDV S protein from a synthetically constructed nanobody yeast library. The VHH genes were then cloned into expression plasmids for recombinant protein production, and the resulting VHHs (termed PEDV S-VHHs) were purified. Indirect immunofluorescence assay (IFA) and Western blotting analysis confirmed that these VHHs specifically bind to both PEDV and its S protein. Neutralization assays demonstrated that seven PEDV S-VHHs exhibited potent neutralizing activity against PEDV. Additionally, a combination of these seven antibodies showed enhanced antiviral effects. Preliminary predictions were also made regarding the binding sites between these VHHs and PEDV. The PEDV S-VHHs described in this study hold potential as candidates for the prevention and treatment of PEDV infection.

Identification and characterization of new B cell epitopes on the nucleocapsid protein of porcine epidemic diarrhea virus using monoclonal antibodies

Porcine epidemic diarrhea virus (PEDV) is the pathogen of Porcine epidemic diarrhea (PED) and can mainly cause acute diarrhea, vomiting, dehydration and high mortality in neonatal piglets. The nucleocapsid (N) protein of PEDV is a highly conserved structural protein. In this study, 6-8-week-old BALB/c mice were immunized with purified PEDV, and three monoclonal antibodies (mAbs) against the PEDV N protein were generated, named 3C6,4F8,4C9. Among them, three new B cell epitopes, 235IGENPDKL242, 12KRVPLSLY19, 372DAFKTGNA380 were firstly identified in the viral N-protein. Among them, 4F8 and 4C9 had IgG1 isotype with Kappa light chain, while 3C6 had IgG2a isotype with Kappa light chain. Three monoclonal antibodies (mAbs) demonstrated specific reactivity with PEDV as evidenced by Western blot and indirect immunofluorescence assay. By studying the interaction between the mAbs and the N protein, we can gain insights into the protein's conformation and functional regions. This information will help develop fast and accurate PEDV diagnostic methods.

Lizhong decoction inhibits porcine epidemic diarrhea virus in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Lizhong decoction (LZD) is a frequently utilized traditional Chinese remedy for diarrhea. It is unknown how effective it is as an antiviral against PEDV infection.

AIM OF THE STUDY

In vitro and in vivo PEDV infection models were used to evaluate the anti-PEDV potential of LZD extract.

MATERIALS AND METHODS

LC-MS was used for qualitative analysis of LZD. The antiviral effect of LZD against PEDV using flow cytometry (FC), Quantitative real-time polymerase chain reaction (QPCR), immunofluorescence assay (IFA) analysis in Vero and IPEC-J2 cells. Additionally, we measured the survival rate, clinical symptoms, body weights, fecal scores, temperature, histological analysis, and viral load in a model of newborn piglets infected with PEDV in order to assess the antiviral impact of LZD in vivo.

RESULTS

In total, 648 compounds were identified, including 144 Alkaloids, 128 Terpenoids, etc. LZD effectively suppressed PEDV replication in vitro. According to time of addition experiments, LZD mostly inhibited PEDV during the viral life cycle's replication stages. During PEDV infection, LZD can Significantly decrease the apoptotic rate of IPEC-J2 cells and Vero cells. In comparison to the model group, LZD was able to decrease the viral titers in the infected piglets' intestinal and visceral tissues, ameliorate their intestinal pathology, cause a significant increase in body weight growth and increase the piglet survival rate.

CONCLUSION

Our findings indicate that the aqueous solution derived from LZD suppressed PEDV replication both in vitro and in vivo, indicating its potential as a candidate for pharmaceutical development.

RpIFN-λ1 alleviates the clinical symptoms of porcine epidemic diarrhea

Porcine epidemic diarrhea (PED), caused by the porcine epidemic diarrhea virus (PEDV), primarily affects the jejunum and ileum of pigs. Interferons, glycoproteins with high species specificity and potent antiviral activity, are crucial in defending against viral infections. Unlike other interferons, interferon-lambda (IFN-λ) mainly acts on mucosal epithelial cells and exhibits robust antiviral activity at mucosal surfaces. However, the high cost limits the use of naturally extracted interferons in farming. In this study, we expressed recombinant porcine interferon-lambda 1 (rpIFN-λ1) in eukaryotic cells, demonstrating effective antiviral activity against PEDV in Vero E6 and IPI-FX cells. In vivo, rpIFN-λ1 alleviated clinical symptoms and intestinal damage, enhanced antioxidant capacity, reduced inflammation, and significantly improved the survival rate of piglets following PEDV infection. Both in vitro and in vivo studies confirmed that rpIFN-λ1 upregulated interferon-stimulated genes (ISGs) via the JAK-STAT pathway, thereby exerting antiviral effects. In conclusion, rpIFN-λ1 significantly inhibited PEDV replication and alleviated clinical symptoms. The selectivity of rpIFN-λ1 for intestinal cells and its ability to reduce viral shedding suggest that this agent is a promising antiviral for enteric viruses such as PEDV. Our findings highlight rpIFN-λ1 as a cost-effective, efficient, and novel strategy for antiviral treatment of PEDV.

Porcine epidemic diarrhea virus: A review of detection, inhibition of host gene expression and evasion of host innate immune

As one of the most important swine enteropathogenic coronavirus, porcine epidemic diarrhea virus (PEDV) is the causative agent of an acute and devastating enteric disease that causes lethal watery diarrhea in suckling piglets. Recent progress in studying PEDV has revealed many intriguing findings on its prevalence and genetic evolution, rapid diagnosis, suppression of host gene expression, and suppression of the host innate immune system. Due to the continuous mutation of the PEDV genome, viral evasions from innate immune defenses and mixed infection with other coronaviruses, the spread of the virus is becoming wider and faster, making it even more necessary to prevent the infections caused by wild-type PEDV variants. It has also been reported that PEDV nsp1 is an essential virulence determinant and is critical for inhibiting host gene expression by structural and biochemical analyses. The inhibition of host protein synthesis employed by PEDV nsp1 may contribute to the regulation of host cell proliferation and immune evasion-related biological functions. In this review, we critically evaluate the recent studies on these aspects of PEDV and assess prospects in understanding the function of PEDV proteins in regulating host innate immune response and viral virulence.

Genetic characteristics associated with the virulence of porcine epidemic diarrhea virus (PEDV) with a naturally occurring truncated ORF3 gene

Porcine epidemic diarrhea virus (PEDV) has emerged in American countries, and it has reemerged in Asia and Europe, causing significant economic losses to the pig industry worldwide. In the present study, the 17GXCZ-1ORF3d strain, which has a naturally large deletion at the 172-554 bp position of the ORF3 gene, together with the 17GXCZ-1ORF3c strain, was serially propagated in Vero cells for up to 120 passages. The adaptability of the two strains gradually increased through serial passages in vitro. Genetic variation analysis of the variants of the two strains from different generations revealed that the naturally truncated ORF3 gene in the 17GXCZ-1ORF3d variants was stably inherited. Furthermore, the survival, viral shedding and histopathological lesions following inoculation of piglets demonstrated that the virulence of 17GXCZ-1ORF3d-P120 was significantly attenuated. These results indicate that the naturally truncated ORF3 gene may accelerate the attenuation of virulence and is involved in PEDV virulence together with mutations in other structural genes. Importantly, immunization of sows with G2b 17GXCZ-1ORF3d-P120 increased PEDV-specific IgG and IgA antibody levels in piglets and conferred partial passive protection against heterologous G2a PEDV strains. Our findings suggest that an attenuated strain with a truncated ORF3 gene may be a promising candidate for protection against PEDV.

Lectin histochemistry in the small intestines of piglets naturally infected with porcine epidemic diarrhea virus

IMPORTANCE

Porcine epidemic diarrhea virus (PEDV) binds to particular cell surface receptors to penetrate cells. The virus specifically identifies certain carbohydrate structures present on the surface of the cell to facilitate the binding process. Nevertheless, the influence of viral infections on specific alterations of glycoconjugates in the small intestines remains unexplored.

OBJECTIVE

This work aimed to examine the alterations in glycoconjugates in the small intestines of piglets naturally infected with PEDV using lectin histochemistry.

METHODS

Six piglets including three PEDV-infected and three non-infected piglets were evaluated. Small intestinal samples were histopathologically examined, and lectin histochemistry was performed.

RESULTS

Piglets infected with PEDV had significant histological abnormalities in their small intestines, such as pronounced villous atrophy, varying degrees of villous fusion, and diverse mucosal alterations. Specific regions of the duodenum, jejunum, and ileum showed discernible variations in glycoconjugate distribution, as determined by lectin histochemistry. Compared with the controls, the PEDV-infected piglets showed significant changes in N-acetylglucosamine- and galactose-binding lectins (particularly wheat germ agglutinin and Arachis hypogaea (peanut) agglutinin) in multiple intestinal regions.

CONCLUSIONS AND RELEVANCE

These findings can enhance understanding of how viruses such as PEDV impact the glycoconjugate composition of the small intestines and emphasize the potential connection between the pathogenesis of PEDV and glycoconjugate.

A novel and cost-effective real-time RT-PCR targeting 24 nucleotides deletion to differentiate PEDV wild-type and classical attenuated vaccine strains

Porcine Epidemic Diarrhea Virus (PEDV) poses a significant threat to the swine industry, causing severe disease and resulting in substantial economic losses. Despite China's implementation of a large-scale vaccine immunization strategy in recent years, various strains of PEDV, including classical attenuated vaccine strains, continue to emerge in immunized pig herds. Here, we established a one-step real-time fluorescent reverse transcription PCR (one-step real-time RT-PCR) assay targeting a 24-nucleotide deletion in the ORF1 region of three PEDV classical attenuated vaccine strains, derived from classical strains. This assay effectively distinguishes between PEDV classical attenuated vaccine strains and wild-type strains, and we also explore the causes of this discriminatory target deficiency of this method through phylogenetic and recombination analysis. We found that these three classical attenuated vaccine strains exhibit closer phylogenetic relationships and higher sequence similarity with five cell-adapted strains. Recombination analysis revealed that although recombination is widespread in the PEDV genome, the 24-nucleotide deletion site remains stable without undergoing recombination and can be utilized as a target for identification. Further analysis revealed there are no enzyme cleavage sites near the 24-nucleotide site, suggesting that this deletion may have been lost during the process of culturing these viral strains in cells.The detection method we have established exhibits high specificity and sensitivity to PEDV, without cross-reactivity with other viruses causing diarrheal diseases. A total of 117 swine fecal samples were analyzed using this established one-step real-time reverse transcription PCR assay, indicating the presence of classical attenuated vaccine strains in pig herds in Gansu province, China. Additionally, the designed primer pairs and two probes can be placed in a single reaction tube to differentiate between these two types of strains, effectively reducing detection costs. These findings offer an efficient and cost-effective technological platform for clinical rapid identification testing of both wild-type and classical attenuated vaccine strains of PEDV, as well as for precise investigation of clinical data on natural infections and vaccine immunity in pig herds.

PA-824 inhibits porcine epidemic diarrhea virus infection in vivo and in vitro by inhibiting p53 activation

Porcine epidemic diarrhea virus (PEDV) is a type A coronavirus that causes severe watery diarrhea in piglets, resulting in severe economic losses worldwide. Therefore, new approaches to control PEDV infection are essential for a robust and sustainable pig industry. We screened 314 small-molecule drug libraries provided by Selleck and found that four drugs had obviously inhibitory effects on PEDV in Vero cells. PA-824, which had the highest SI index and the most reliable clinical safety, was selected for in vivo experiments. Animal attack tests showed that PA-824 effectively alleviated the clinical signs, intestinal pathological changes, and inflammatory responses in lactating piglets after PEDV infection. To further investigate the antiviral mechanism of PA-824, we measured the inhibitory effect of PA-824 on PEDV proliferation in a dose-dependent manner. By exploring the effect of PA-824 on the PEDV life cycle, we found that PA-824 acted directly on viral particles and hindered the adsorption, internalization, and replication phases of the virus, followed by molecular docking analysis to predict the interaction between PA-824 and PEDV non-structural proteins. Finally, we found that PA-824 could inhibit the apoptotic signaling pathway by suppressing PEDV-induced p53 activation. These results suggest that PA-824 could be protective against PEDV infection in piglets and could be developed as a drug or a feed additive to prevent and control PEDV diseases.IMPORTANCEPEDV is a highly contagious enteric coronavirus that widely spread worldwide, causing serious economic losses. There is no drug or vaccine to effectively control PEDV. In this study, we found that PA-824, a compound of mycobacteria causing pulmonary diseases, inhibited PEDV proliferation in both in vitro and in vivo. We also found that PA-824 directly acted on viral particles and hindered the adsorption, internalization, and replication stages of the virus. In addition, we found that PA-824 could inhibit the apoptotic signaling pathway by inhibiting PEDV-induced p53 activation. In conclusion, it is expected to be developed as a drug or a feed additive to prevent and control PEDV diseases.

Elevation of IL-8 secretion induced by PEDV infection via NF-κB signaling pathway

Porcine epidemic diarrhea virus (PEDV) is associated with severe enteritis, which contributes to high mortality in piglets. The aim of this study was to describe molecular mechanisms associated with proinflammatory cytokine(s) production during PEDV infection. We showed that infection of porcine intestine epithelial cell clone J2 (IPEC-J2) with PEDV induces a gradual increase in interleukin 8 (IL-8) production at different time points, as well as infection of Vero E6 with PEDV. The secretion of IL-8 in these two cell lines infected with PEDV is related to the activation of NF-κB. Furthermore, the cells expressing PEDV M or E protein can induce the upregulation of IL-8. These findings suggest that the IL-8 production can be the initiator of inflammatory response by the host cells upon PEDV infection.

Nsp10-interacting host protein SAP18 restricts PEDV replication in Marc-145 cells via enhancing dephosphorylation of RIG-I

PEDV, a single-stranded RNA virus, causes significant economic losses in the pig industry. Sin3-associated protein 18 (SAP18) is known for its role in transcriptional inhibition and RNA splicing. However, research on SAP18's involvement in PEDV infection is limited. Here, we identified an interaction between SAP18 and PEDV nonstructural protein 10 (Nsp10) using immunoprecipitation-mass spectrometry (IP-MS) and confirmed it through immunoprecipitation and laser confocal microscopy. Additionally, PEDV Nsp10 reduced SAP18 protein levels and induced its cytoplasmic accumulation. Overexpressing SAP18 suppressed PEDV replication, meanwhile its knockdown via short interfering RNA (siRNA) enhanced replication. SAP18 overexpression boosted IRF3 and NF-κB P65 phosphorylation, nuclear translocation, and IFN-β antiviral response. Furthermore, SAP18 upregulated RIG-I expression and facilitated its dephosphorylation, while SAP18 knockdown had the opposite effect. Finally, SAP18 interacted with phosphatase 1 (PP1) catalytic subunit alpha (PPP1CA), promoting PPP1CA-RIG-I interaction during PEDV infection. These findings highlight SAP18's role in activating the type I interferon pathway and inhibiting viral replication by promoting RIG-I dephosphorylation through its interaction with PPP1CA.

Development of a colloidal gold immunochromatographic strip for the simultaneous detection of porcine epidemic diarrhea virus and transmissible gastroenteritis virus

In recent years, porcine diarrhea-associated viruses have caused significant economic losses globally. These viruses present similar clinical symptoms, such as watery diarrhea, dehydration, and vomiting. Co-infections with porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) are common. For the rapid and on-site preliminary diagnosis on the pig farms, this study aimed to develop a colloidal gold immunochromatography assay (GICA) strip for the detection of PEDV and TGEV simultaneously. The GICA kit showed that there was no cross-reactivity with the other five common porcine viruses. With visual observation, the lower limits were approximately 104 TCID50/mL and 104 TCID50/mL for PEDV and TGEV, respectively. The GICA strip could be stored at 4°C or 25°C for 12 months without affecting its efficacy. To validate the GICA strip, 121 clinical samples were tested. The positive rates of PEDV and TGEV were 42.9 and 9.9%, respectively, and the co-infection rate of the two viruses was 5.8% based on the duplex GICA strip. Thus, the established GICA strip is a rapid, specific, and stable tool for on-site preliminary diagnosis of PEDV- and TGEV-associated diarrhea.

High-affinity monoclonal antibodies against the porcine epidemic diarrhea virus S1 protein

The porcine epidemic diarrhea virus (PEDV) infection inflicted substantial economic losses upon the global pig-breeding industry. This pathogen can infect all pigs and poses a particularly high fatality risk for suckling piglets. The S1 subunit of spike protein is a crucial target protein for inducing the particularly neutralizing antibodies that can intercept the virus-host interaction and neutralize virus infectivity. In the present study, the HEK293F eukaryotic expression system was successfully utilized to express and produce recombinant S1 protein. Through quantitative analysis, five monoclonal antibodies (mAbs) specifically targeting the recombinant S1 protein of PEDV were developed and subsequently evaluated using enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and flow cytometry assay (FCA). The results indicate that all five mAbs belong to the IgG1 isotype, and their half-maximal effective concentration (EC50) values measured at 84.77, 7.42, 0.89, 14.64, and 7.86 pM. All these five mAbs can be utilized in ELISA, FCA, and IFA for the detection of PEDV infection. MAb 5-F9 exhibits the highest sensitivity to detect as low as 0.3125 ng/mL of recombinant PEDV-S1 protein in ELISA, while only 0.096 ng/mL of mAb 5-F9 is required to detect PEDV in FCA. The results from antigen epitope analysis indicated that mAb 8-G2 is the sole antibody capable of recognizing linear epitopes. In conclusion, this study has yielded a highly immunogenic S1 protein and five high-affinity mAbs specifically targeting the S1 protein. These findings have significant implications for early detection of PEDV infection and provide a solid foundation for further investigation into studying virus-host interactions.

Inhibition of PEDV viral entry upon blocking N-glycan elaboration

Porcine Epidemic Diarrhea Virus (PEDV) poses a significant threat to the global swine industry, demanding a thorough understanding of its cellular invasion mechanism for effective interventions. This study meticulously investigates the impact of O- and N-linked glycans on PEDV proteins and host cell interaction, shedding light on their influence on the virus's invasion process. Utilizing CRISPR-Cas9 technology to inhibit cell surface O- and N-linked glycan synthesis demonstrated no discernible impact on virus infection. However, progeny PEDV strains lacking these glycans exhibited a minor effect of O-linked glycans on virus infection. Conversely, a notable 40% reduction in infectivity was observed when the virus surface lacked N-linked glycans, emphasizing their pivotal role in facilitating virus recognition and binding to host cells. Additionally, inhibition studies utilizing kifunensine, a natural glycosidase I inhibitor, reaffirmed the significant role of N-linked glycans in virus infection. Inhibiting N-linked glycan synthesis with kifunensine substantially decreased virus entry into cells and potentially influenced spike protein expression. Assessment of the stability and recovery potential of N-linked glycan-deficient strains underscored the critical importance of N-glycans at various stages of the virus lifecycle. In vivo experiments infecting piglets with N-glycan-deficient strains exhibited milder clinical symptoms, reduced virus excretion, and less severe pathological lesions compared to conventional strains. These findings offer promising translational applications, proposing N-glycosylation inhibitors as potential therapeutic interventions against PEDV. The utilization of these inhibitors might mitigate virus invasion and disease transmission, providing avenues for effective antiviral strategies and vaccine development. Nonetheless, further research is warranted to elucidate the precise mechanisms of N-linked glycans in PEDV infection for comprehensive clinical applications.

Virological evaluation of natural and modified attapulgite against porcine epidemic diarrhoea virus

BACKGROUND

The Porcine Epidemic Diarrhea Virus (PEDV) has caused significant economic losses in the global swine industry. As a potential drug for treating diarrhea, the antiviral properties of attapulgite deserve further study.

METHODS

In this study, various methods such as RT-qPCR, Western blot, viral titer assay, Cytopathic Effect, immunofluorescence analysis and transmission electron microscopy were used to detect the antiviral activity of attapulgite and to assess its inhibitory effect on PEDV.

RESULTS

When exposed to the same amount of virus, there was a significant decrease in the expression of the S protein, resulting in a viral titer reduction from 10-5.613 TCID50/mL to 10-2.90 TCID50/mL, which represents a decrease of approximately 102.6 folds. Results of cytopathic effect and indirect immunofluorescence also indicate a notable decrease in viral infectivity after attapulgite treatment. Additionally, it was observed that modified materials after acidification had weaker antiviral efficacy compared to powdered samples that underwent ultrasonic disintegration, which showed the strongest antiviral effects.

CONCLUSION

As a result, Attapulgite powders can trap and adsorb viruses to inhibit PEDV in vitro, leading to loss of viral infectivity. This study provides new materials for the development of novel disinfectants and antiviral additives.

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.

Development of Glycyrrhizinic Acid-Based Lipid Nanoparticle (LNP-GA) as An Adjuvant That Improves the Immune Response to Porcine Epidemic Diarrhea Virus Spike Recombinant Protein

Porcine epidemic diarrhea virus (PEDV) has affected the pork industry worldwide and during outbreaks the mortality of piglets has reached 100%. Lipid nanocarriers are commonly used in the development of immunostimulatory particles due to their biocompatibility and slow-release delivery properties. In this study, we developed a lipid nanoparticle (LNP) complex based on glycyrrhizinic acid (GA) and tested its efficacy as an adjuvant in mice immunized with the recombinant N-terminal domain (NTD) of porcine epidemic diarrhea virus (PEDV) spike (S) protein (rNTD-S). The dispersion stability analysis (Z-potential -27.6 mV) confirmed the size and charge stability of the LNP-GA, demonstrating that the particles were homogeneously dispersed and strongly anionic, which favors nanoparticles binding with the rNTD-S protein, which showed a slightly positive charge (2.11 mV) by in silico analysis. TEM image of LNP-GA revealed nanostructures with a spherical-bilayer lipid vesicle (~100 nm). The immunogenicity of the LNP-GA-rNTD-S complex induced an efficient humoral response 14 days after the first immunization (p < 0.05) as well as an influence on the cellular immune response by decreasing serum TNF-α and IL-1β concentrations, which was associated with an anti-inflammatory effect.

A novel recombination porcine epidemic diarrhea virus isolated from Gansu, China: Genetic characterization and pathogenicity

Porcine epidemic diarrhea virus (PEDV) is an acute and highly contagious porcine enteric coronavirus. It has caused serious economic losses of pig industry in China. Here we insolated a current PEDV field strain named GS2022, analyzed the characters of genetic variation and pathogenicity. The results demonstrated that the GS2022 strain was belong to a newly defined subgroup G2 d, forming an independent branch which mainly contains strains isolated in China from 2017 to 2023. Notably, there are multiple mutations and extensive N-glycosylation compared to CV777 strain and PT-P5 strain, therefore the structure of GS2022 strain is different from 6U7K and 7W6M. Animal pathogenicity test showed that GS2022 strain could cause severe clinical signs and the high level of virus shedding in 7-day-old piglets. But recovery of diarrhea after 5 days, and no pathological damage to important organs. Further study on 3-day-old piglets also indicated GS2022 strain have pathogenicity. In this study no piglets died, which make it possible for that GS2022 strain become a candidate vaccine. These results are helpful to understand the epidemiology, molecular characteristics, evolution, and antigenicity of PEDV circulating in China. It also provides reference for designing effective vaccines against PEDV.

Metagenomic survey of viral diversity obtained from feces of piglets with diarrhea

Pigs are natural host to various zoonotic pathogens including viruses. In this study, we analyzed the viral communities in the feces of 89 piglets with diarrhea under one month old which were collected from six farms in Jiangsu Province of the Eastern China, using the unbiased virus metagenomic method. A total of 89 libraries were constructed, and 46937894 unique sequence reads were generated by Illumina sequencing. Overall, the family Picornaviridae accounted for the majority of the total reads of putative mammalian viruses. Ten novel virus genomes from different family members were discovered, including Parvoviridae (n = 2), Picobirnaviridae (n = 4) and CRESS DNA viruses (n = 4). A large number of phages were identified, which mainly belonged to the order Caudovirales and the family Microviridae. Moreover, some identified viruses were closely related to viruses found in non-porcine hosts, highlighting the potential for cross-species virus dissemination. This study increased our understanding of the fecal virus communities of diarrhea piglets and provided valuable information for virus monitoring and preventing.

Targeting protein-protein interaction interfaces with antiviral N protein inhibitor in SARS-CoV-2

Coronaviruses not only pose significant global public health threats but also cause extensive damage to livestock-based industries. Previous studies have shown that 5-benzyloxygramine (P3) targets the Middle East respiratory syndrome coronavirus (MERS-CoV) nucleocapsid (N) protein N-terminal domain (N-NTD), inducing non-native protein-protein interactions (PPIs) that impair N protein function. Moreover, P3 exhibits broad-spectrum antiviral activity against CoVs. The sequence similarity of N proteins is relatively low among CoVs, further exhibiting notable variations in the hydrophobic residue responsible for non-native PPIs in the N-NTD. Therefore, to ascertain the mechanism by which P3 demonstrates broad-spectrum anti-CoV activity, we determined the crystal structure of the SARS-CoV-2 N-NTD:P3 complex. We found that P3 was positioned in the dimeric N-NTD via hydrophobic contacts. Compared with the interfaces in MERS-CoV N-NTD, P3 had a reversed orientation in SARS-CoV-2 N-NTD. The Phe residue in the MERS-CoV N-NTD:P3 complex stabilized both P3 moieties. However, in the SARS-CoV-2 N-NTD:P3 complex, the Ile residue formed only one interaction with the P3 benzene ring. Moreover, the pocket in the SARS-CoV-2 N-NTD:P3 complex was more hydrophobic, favoring the insertion of the P3 benzene ring into the complex. Nevertheless, hydrophobic interactions remained the primary stabilizing force in both complexes. These findings suggested that despite the differences in the sequence, P3 can accommodate a hydrophobic pocket in N-NTD to mediate a non-native PPI, enabling its effectiveness against various CoVs.

Phylogenetic and Molecular Analysis of the Porcine Epidemic Diarrhea Virus in Mexico during the First Reported Outbreaks (2013-2017)

The characteristics of the whole PEDV genome that has circulated in Mexico from the first outbreak to the present are unknown. We chose samples obtained from 2013 to 2017 and sequenced them, which enabled us to identify the genetic variation and phylogeny in the virus during the first four years that it circulated in Mexico. A 99% identity was found among the analyzed pandemic strains; however, the 1% difference affected the structure of the S glycoprotein, which is essential for the binding of the virus to the cellular receptor. The S protein induces the most efficacious antibodies; hence, these changes in structure could be implicated in the clinical antecedents of the outbreaks. Antigenic changes could also help PEDV avoid neutralization, even in the presence of previous immunity. The characterization of the complete genome enabled the identification of three circulating strains that have a deletion in ORF1a, which is present in attenuated Asian vaccine strains. The phylogenetic analysis of the complete genome indicates that the first PEDV outbreaks in Mexico were caused by INDEL strains and pandemic strains related to USA strains; however, the possibility of the entry of European strains exists, which may have caused the 2015 and 2016 outbreaks.

Expression and immunogenicity of non-structural protein 8 of porcine epidemic diarrhea virus

The non-structural protein (nsp) 8 of the porcine epidemic diarrhea virus (PEDV) is highly stable across different PEDV strains and plays an important role in PEDV virulence. In current study, nsp8 prokaryotic expression vectors were constructed based on parental vectors pMAL-c2x-maltose binding protein (MBP) and pET-28a (+). Subsequently, the optimization of expression conditions in Escherichia coli, including induced temperature, time and isopropyl β-D-thiogalactopyranoside concentration were performed to obtain a stable expression of MBP-nsp8 and nsp8. The nsp8 fused with MBP increased the water solubility of the expressed products. Target proteins were further purified from E. coli culture and their immunogenicities were evaluated in vivo by mice. The antibody titers of serum from nsp8 immunized mice were up to 1:7,750,000 when measured by indirect enzyme-linked immunosorbent assay; meanwhile, the mice immunized with MBP-nsp8 gave an antibody titer reaching 1:1,000,000. In all, the expression and purification system of PEDV nsp8 and MBP-nsp8 were successfully established in this work and a strong immune response was elicited in mice by both purified nsp8 and MBP-nsp8, providing a basis for the study of the structure and function of PEDV nsp8.

Angiotensin converting enzyme 2 does not facilitate porcine epidemic diarrhea virus entry into porcine intestinal epithelial cells and inhibits it-induced inflammatory injury by promoting STAT1 phosphorylation

ACE2 has been confirmed to be a functional receptor for SARS-CoV and SARS-CoV-2, but research on animal coronaviruses, especially PEDV, are still unknown. The present study investigated whether ACE2 plays a role in receptor recognition and subsequent infection during PEDV invasion of host cells. IPEC-J2 cells stably expressing porcine ACE2 did not increase the production of PEDV-N but inhibited its expression. Porcine ACE2 knockout cells was generated by CRISPR/Cas9 genome editing in IPEC-J2 cells. The expression of PEDV-N did not decrease but slightly increased. The Co-IP results showed that there was no significant association between ACE2 and PEDV-S. There were no obvious interaction between PEDV-S, PEDV-E, PEDV-M and porcine ACE2 promoters, but PEDV-N could inhibit the activity of ACE2 promoters. PEDV-N degraded STAT1 and prevented its phosphorylation, thereby inhibiting the expression of interferon-stimulated genes. Repeated infection of PEDV further confirmed the above results. PEDV activated ACE-Ang II-AT1R axis, while ACE2-Ang (1-7)-MasR axis activity was decreased and inflammatory response was intensified. However, excess ACE2 can reverse this reaction. These results reveal that ACE2 does not facilitate PEDV entry into cells, but relieves PEDV-induced inflammation by promoting STAT1 phosphorylation.

Synbiotics improve growth performance and nutrient digestibility, inhibit PEDV infection, and prevent intestinal barrier dysfunction by mediating innate antivirus immune response in weaned piglets

This experiment was conducted to explore the effects of dietary synbiotics (SYB) supplementation on growth performance, immune function, and intestinal barrier function in piglets challenged with porcine epidemic diarrhea virus (PEDV). Forty crossbred (Duroc × Landrace × Yorkshire) weaned piglets (26 ± 1 d old) with a mean body weight (BW) of 6.62 ± 0.36 kg were randomly allotted to five groups: control (CON) I and CONII group, both fed basal diet; 0.1% SYB group, 0.2% SYB group, and 0.2% yeast culture (YC) group, fed basal diet supplemented with 0.1%, 0.2% SYB, and 0.2% YC, respectively. On day 22, all piglets were orally administrated with 40 mL PEDV (5.6 × 103 TCID50/mL) except piglets in CONI group, which were administrated with the same volume of sterile saline. The trial lasted for 26 d. Before PEDV challenge, dietary 0.1% SYB supplementation increased final BW, average daily gain (ADG), and decreased the ratio of feed to gain during 0 to 21 d (P < 0.05), as well as improved the apparent nutrient digestibility of dry matter (DM), organic matter (OM), crude protein, ether extract (EE), and gross energy (GE). At the same time, 0.2% YC also improved the apparent nutrient digestibility of DM, OM, EE, and GE (P < 0.05). PEDV challenge increased diarrhea rate and diarrhea indexes while decreased ADG (P < 0.05) from days 22 to 26, and induced systemic and intestinal mucosa innate immune and proinflammatory responses, destroyed intestinal barrier integrity. The decrease in average daily feed intake and ADG induced by PEDV challenge was suppressed by dietary SYB and YC supplementation, and 0.1% SYB had the best-alleviating effect. Dietary 0.1% SYB supplementation also increased serum interleukin (IL)-10, immunoglobulin M, complement component 4, and jejunal mucosal IL-4 levels, while decreased serum diamine oxidase activity compared with CONII group (P < 0.05). Furthermore, 0.1% SYB improved mRNA expressions of claudin-1, zonula occludens protein-1, mucin 2, interferon-γ, interferon regulatory factor-3, signal transducers and activators of transcription (P < 0.05), and protein expression of occludin, and downregulated mRNA expressions of toll-like receptor 3 and tumor necrosis factor-α (P < 0.05) in jejunal mucosa. Supplementing 0.2% SYB or 0.2% YC also had a positive effect on piglets, but the effect was not as good as 0.1% SYB. These results indicated that dietary 0.1% SYB supplementation improved growth performance under normal conditions, and alleviated the inflammatory response and the damage of intestinal barrier via improving innate immune function and decreasing PEDV genomic copies, showed optimal protective effects against PEDV infection.

Veratramine inhibits porcine epidemic diarrhea virus entry through macropinocytosis by suppressing PI3K/Akt pathway

Porcine epidemic diarrhea (PED) is a contagious intestinal disease caused by α-coronavirus porcine epidemic diarrhea virus (PEDV). At present, no effective vaccine is available to prevent the disease. Therefore, research for novel antivirals is important. This study aimed to identify the antiviral mechanism of Veratramine (VAM), which actively inhibits PEDV replication with a 50 % inhibitory concentration (IC50) of ∼5 µM. Upon VAM treatment, both PEDV-nucleocapsid (N) protein level and virus titer decreased significantly. The time-of-addition assay results showed that VAM could inhibit PEDV replication by blocking viral entry. Importantly, VAM could inhibit PEDV-induced phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) activity and further suppress micropinocytosis, which is required for PEDV entry. In addition, PI3K inhibitor LY294002 showed anti-PEDV activity by blocking viral entry as well. Taken together, VAM possessed anti-PEDV properties against the entry stage of PEDV by inhibiting the macropinocytosis pathway by suppressing the PI3K/Akt pathway. VAM could be considered as a lead compound for the development of anti-PEDV drugs and may be used during the viral entry stage of PEDV infection.

Inhibitory effects of quercetin on porcine epidemic diarrhea virus in vitro and in vivo

Porcine epidemic diarrhea (PED) is an acute, severe, highly contagious disease. Porcine epidemic diarrhea virus (PEDV) strains are prone to mutation, and the immune response induced by traditional vaccines may not be strong enough to be effective against the virus. Therefore, there is an urgent need to develop novel anti-PEDV drugs. This study aimed to explore the therapeutic effects of quercetin in PEDV infections in vitro (Vero cells) and in vivo (suckling piglets). Using transmission electron microscopy and laser confocal microscopy, we found that PEDV infection promotes the accumulation of lipid droplets (LDs). In vitro, studies showed that quercetin inhibits LD accumulation by down-regulating NF-κB signaling and IL-1β, IL-8, and IL-6 levels, thereby inhibiting viral replication. In vivo, studies in pigs demonstrated that quercetin can effectively relieve the clinical symptoms and intestinal injury caused by PEDV. Collectively, our findings suggest that quercetin inhibits PEDV replication both in vivo and in vitro, which provides a new direction for the development of PED antiviral drugs.

Accurate location of two conserved linear epitopes of PEDV utilizing monoclonal antibodies induced by S1 protein nanoparticles

Porcine Epidemic diarrhea virus (PEDV), which can result in severe vomiting, diarrhea, dehydration and death in newborn piglets, poses a great threat to the pig industry around the world. The S1 subunit of S protein is crucial for triggering neutralizing antibodies binding to the receptor. Based on the advantages of high immunogenicity and precise assembly of nanoparticles, the mi3 nanoparticles and truncated S1 protein were assembled by the SpyTag/SpyCatcher system and then expressed in HEK293F cells, whereafter high-efficiency monoclonal antibodies (mAbs) were produced and identified. The obtained five mAbs can bind to various genotypes of PEDV, including a mAb (12G) which can neutralize G1 and G2 genotypes of PEDV in vitro. By further identification of monoclonal antibody target sequences, 507FNDHSF512 and 553LFYNVTNSYG562 were first identified as B-cell linear epitopes, in which 553LFYNVTNSYG562 was a neutralizing epitope. Alanine scans identified the key amino acid sites of two epitopes. Moreover, the results of multiple sequence alignment analysis showed that these two epitopes were highly conserved in various subtype variants. In brief, these findings can serve as a basis for additional research of PEDV and prospective resources for the creation of later detection and diagnostic techniques.

A recombination-resistant genome for live attenuated and stable PEDV vaccines by engineering the transcriptional regulatory sequences

IMPORTANCE

Coronaviruses are important pathogens of humans and animals, and vaccine developments against them are imperative. Due to the ability to induce broad and prolonged protective immunity and the convenient administration routes, live attenuated vaccines (LAVs) are promising arms for controlling the deadly coronavirus infections. However, potential recombination events between vaccine and field strains raise a safety concern for LAVs. The porcine epidemic diarrhea virus (PEDV) remodeled TRS (RMT) mutant generated in this study replicated efficiently in both cell culture and in pigs and retained protective immunogenicity against PEDV challenge in pigs. Furthermore, the RMT PEDV was resistant to recombination and genetically stable. Therefore, RMT PEDV can be further optimized as a backbone for the development of safe LAVs.

Molecular Characterization of Porcine Epidemic Diarrhea Virus from Field Samples in South Korea

Porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric pathogen of swine. PEDV has been a major problem in the pig industry since its first identification in 1992. The aim of this study was to investigate the diversity, molecular characteristics, and phylogenetic relationships of PEDVs in field samples from Korea. Six PEDVs were identified from the field samples, and the full spike (S) glycoprotein gene sequences were analyzed. A phylogenetic analysis of the S gene sequences from the six isolates revealed that they were clustered into the G2b subgroup with genetic distance. The genetic identity of the nucleotide sequences and deduced amino acid sequences of the S genes of those isolates was 97.9-100% and 97.4-100%, respectively. A BLAST search for new PEDVs revealed an identity greater than 99.5% compared to the highest similarity of two different Korean strains. The CO-26K equivalent (COE) epitope had a 521H→Y/Q amino acid substitution compared to the subgroup G2b reference strain (KNU-1305). The CNU-22S11 had 28 amino acid substitutions compared to the KNU-1305 strain, which included two newly identified amino acid substitutions: 562S→F and 763P→L in the COE and SS6 epitopes, respectively. Furthermore, the addition and loss of N-linked glycosylation were observed in the CNU-22S11. The results suggest that various strains of PEDV are prevalent and undergoing evolution at swine farms in South Korea and can affect receptor specificity, virus pathogenicity, and host immune system evasion. Overall, this study provides an increased understanding of the prevalence and control of PEDV in South Korea.