Research progress of porcine epidemic diarrhea virus S protein

Neutralizing antibody levels as a key factor in determining the immunogenic efficacy of the novel PEDV alpha coronavirus vaccine

Porcine epidemic diarrhea virus (PEDV) causes significant global agricultural losses. Despite commercial inactivated and live attenuated vaccines, persistent outbreaks underscore the need for more effective solutions. Here, we isolated a novel Chinese PEDV variant, PEDV ShXXY2-2023, with amino acid substitutions in key neutralizing epitopes (N-terminal domain, receptor-binding domain, and CO-26K equivalent epitope) compared to vaccine strains. An inactivated ShXXY2-2023 vaccine induced higher neutralizing antibodies and superior cross-protection versus commercial vaccines. Vaccinated sows conferred enhanced protection to offspring, improving piglet survival post-challenge. Maternal serum neutralizing antibody titers correlated strongly with piglet survival; titers of 1:377-1:774 at one week prepartum yielded >80% protective efficacy. These findings emphasize neutralizing antibodies' critical role in PEDV prevention and position ShXXY2-2023 as a promising vaccine candidate, with broader implications for coronavirus vaccine development.

Molecular characterization of porcine epidemic diarrhea virus in Sichuan from 2023 to 2024

Porcine Epidemic Diarrhea (PED) is an acute, highly contagious disease caused by Porcine Epidemic Diarrhea Virus (PEDV). It is characterized by symptoms such as diarrhea, vomiting, and dehydration in pigs of all ages, with particularly severe outcomes in neonatal pigs. In this study, a total of 254 samples were collected from Sichuan Province between 2023 and 2024 to investigate the prevalence and genetic characteristics of PEDV. The overall prevalence of PEDV was found to be 19.3 %, with regional prevalence rates of 26.5 % in the Guangyuan region and 14.3 % in the Suining region. Phylogenetic analysis revealed that the G2c genotype was the predominant circulating strain. Furthermore, sequence analysis demonstrated that the six isolates exhibited greater sequence similarity to the AJ1102 vaccine strain than to the CV7777 strain. Notably, consistent mutations were observed in the G2b and G2c genotypes, including the insertion of four amino acids (QGVN) at positions 59-62, as well as amino acid substitutions at positions 140 and 161 in the G2b and G2c strains, respectively. Moreover, the G1c (S-INDEL) strain displayed amino acid losses and gains at positions 140 and 160, respectively. N-glycosylation site analysis of the S proteins from both the isolates and the vaccine strains revealed the absence of an N-glycosylation site at position 510 in all isolates. Notably, the SC/GY/2022 isolate contained only six N-glycosylation sites throughout the S protein, which is significantly fewer than those found in the vaccine strains. These findings provide a comprehensive understanding of the epidemiology of PEDV in Sichuan Province and offer valuable insights for the development of more effective immunological prevention and control strategies against PEDV.

The biomechanical phenomena observed in the cell invasion pathway of porcine epidemic diarrhea virus: a review

Porcine epidemic diarrhea virus (PEDV) is the primary pathogen responsible for highly contagious intestinal infections in pigs, which results in significant economic losses to the global animal husbandry industry. PEDV is an enveloped virus that enters cells via endocytosis, a process that is dependent on the binding of the viral surface S protein to a receptor on the host cell membrane. This results in a series of biomechanical alterations that drive the fusion of the viral and host cell membranes. These alterations stabilise the binding of the virus to the receptor and also affect the tension and the curvature of the plasma membrane and the formation of endocytic vesicles. A comprehensive understanding of the mechanism by which PEDV enters cells and the biomechanical changes that accompany this process is of paramount importance for the development of PEDV inhibitors, vaccines, and disease prevention and control strategies. Here, we review the general mechanism of PEDV entry, the biomechanical phenomena that occur during endocytosis, and the potential applications of biomechanics in antiviral therapy. It is anticipated that by gaining insight into these mechanisms, novel approaches to regulating viral entry pathways through mechanical interference, vaccine development, and antiviral drug design can be explored.

Palmitoylation enhances the stability of porcine epidemic diarrhea virus spike protein by antagonizing its degradation via chaperone-mediated autophagy to facilitate viral proliferation

Porcine epidemic diarrhea (PED) is a highly pathogenic and infectious intestinal disease caused by the PED virus (PEDV) and has inflicted substantial economic losses on the global swine industry. Therefore, it is imperative to explore appropriate targets to restrain PEDV infection. PEDV spike (S) protein is crucial for viral infection and is regarded as an ideal target for the development of vaccines and antiviral therapeutics. Palmitoylation is a significant post-translational modification implicated in multiple viral replication cycles. Despite the fact that palmitoylation of certain coronavirus S proteins has been reported, the specific biological significance and underlying molecular mechanisms of PEDV S protein palmitoylation have not been fully defined. In the present study, we uncover that palmitoylation enhances the stability of PEDV S protein to promote viral proliferation. Mechanistically, we identify that a cysteine-rich region within the cytoplasmic tail of PEDV S protein is palmitoylated by the zinc finger Asp-His-His-Cys domain palmitoyltransferase 5 (ZDHHC5). We further illustrate that palmitoylation prevents the recognition of Lys-Phe-Glu-Arg-Gln (KFERQ)-like motif in PEDV S protein by heat shock cognate protein of 70 kDa (HSC70), thereby antagonizing its degradation via chaperone-mediated autophagy (CMA). Collectively, our findings underscore the importance of palmitoylation for PEDV pathogenesis and provide prospective targets for the development of antiviral interventions.IMPORTANCEPEDV poses a serious threat to pig farming worldwide. As a consequence, a comprehensive investigation of PEDV pathogenesis is of great significance for the prevention and control of the virus. Here, we verify that ZDHHC5-mediated palmitoylation of PEDV S protein enhances its stability through impeding recognition by HSC70 and antagonizing degradation via CMA to facilitate viral propagation. Our findings highlight the important role of palmitoylation in PEDV proliferation and support palmitoylation as a promising target for the development of antiviral strategies.

Development of a Paper-Based Microfluidic Chip for Point-of-Care Detection of PEDV

PEDV poses a significant threat to the global swine industry, necessitating rapid and accurate diagnostic methods for effective disease management. In this study, we developed a foldable, easy-to-use paper-based microfluidic analytical device (μPAD) for on-site detection of PEDV. The device seamlessly integrates paper-based nucleic acid enrichment, LAMP reaction, and visual lateral flow detection into a single platform. Key parameters, including nucleic acid extraction protocols, chromatographic channel configurations, colorimetric indicators, and reaction temperature and duration, were systematically optimized. The resulting LAMP-μPAD assay detects PEDV within 30 min at 60 °C, achieving a limit of detection of 4.82 × 102 copies/μL with no cross-reactivity against other viruses. When evaluated against RT-PCR using clinical specimens, the assay demonstrated a specificity of 100%, a sensitivity of 95.3%, and an overall concordance of 98.5%. This paper-based sensor offers a promising alternative for the rapid, on-site detection of PEDV and other highly transmissible pathogens.

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.

Epidemiological Study and Genetic Diversity Assessment of Porcine Epidemic Diarrhea Virus (PEDV) in Yunnan Province, China

Porcine epidemic diarrhea virus (PEDV) is a highly contagious pathogen responsible for devastating enteric disease and lethal watery diarrhea, leading to significant economic losses in the global swine industry. Understanding the epidemiology and genetic diversity of PEDV over the past decade is crucial for the effective prevention and treatment of porcine epidemic diarrhea. In this study, 1851 fecal samples were collected from pigs exhibiting diarrhea symptoms across 11 cities in Yunnan Province between 2013 and 2022. The prevalence of PEDV, along with other common swine diarrhea viruses, including porcine transmissible gastroenteritis virus (TGEV), porcine rotavirus (PoRV), porcine Sapporo virus (PoSaV), porcine stellate virus (PaStV), and porcine delta coronavirus (PDCoV) was assessed using a polymerase chain reaction (PCR) assay. The results revealed a total detection rate of 52.94% (980/1851) for the six viruses, with PEDV accounting for 25.93% (480/1851) of cases. Further analysis showed that weaned piglets were more susceptible to PEDV than fattening pigs, with the highest prevalence observed in spring (61.52%, 275/447) and the lowest in summer (12.68%, 97/765). Dual infections were also identified, with PEDV + PoSaV being the most common combination (2.81%, 52/1851), followed by PEDV + PoRV, with a detection rate of 1.67% (31/1851). Phylogenetic analysis of the PEDV S genes revealed that the 28 epidemic strains in Yunnan Province shared a nucleotide sequence homology from 91.4% to 98.4% and an amino acid sequence homology ranging from 85.6% to 99.3%. All strains were classified as GII variant strains. This study provides a comprehensive overview of the epidemiology of PEDV and its co-infection patterns with other common diarrhea-causing viruses in the swine herds of Yunnan Province over the past decade. These findings offer valuable insights for the development of effective prevention and control strategies to mitigate the impact of PEDV and other enteroviruses on the swine industry in Yunnan Province.

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.

Detection and Phylogenetic Analysis of an Exotic Strain of Porcine Epidemic Diarrhea Virus and Its Effect on an Affected Herd Immunized Against the Endemic Strain in Thailand

Porcine epidemic diarrhea (PED) is caused by the PED virus, with genogroup 2 (G2), comprising G2a and G2b, being the primary contributors to outbreaks worldwide. In Thailand, G2a was the only virulent strain identified until the emergence of the first G2b strain in 2014, followed by additional G2b strains in 2015-2016, particularly those closely related to virulent strains from China. This led to increased awareness of more frequent and complex outbreaks. This study examined farms affected by G2a and G2b strains, both employing planned exposure of sows to intestines from G2a-affected piglets, a traditional practice in Thailand. The analysis focused on the milk and colostrum profiles of sows, including viral neutralization and ELISA methods, as well as histopathological assessments of piglet intestinal villi. Additionally, a novel G2b strain was sequenced for phylogenetic and protein structure analyses. The results revealed no significant differences in colostrum and milk profiles between the farms. However, piglets infected with G2b showed significantly more severe intestinal damage. A unique insertion in the protein structure of the novel G2b strain led to the identification of a new epitope and potential changes in viral properties. This study highlights the importance of monitoring emerging strains and provides valuable insights for enhancing preventive strategies and advancing phylogenetic research.

Nanoparticle Vaccine Triggers Interferon-Gamma Production and Confers Protective Immunity against Porcine Reproductive and Respiratory Syndrome Virus

The swine industry annually suffers significant economic losses caused by porcine reproductive and respiratory syndrome virus (PRRSV). Because the available commercial vaccines have limited protective efficacy against epidemic PRRSV, there is an urgent need for innovative solutions. Nanoparticle vaccines induce robust immune responses and have become a promising direction in vaccine development. In this study, we designed and produced a self-assembling nanoparticle vaccine derived from thermophilic archaeal ferritin to combat epidemic PRRSV. First, multiple T cell epitopes targeting viral structural proteins were identified by IFN-γ screening after PRRSV infection. Three different self-assembled nanoparticles with epitopes targeting viral GP3, GP4, and GP5 proteins were constructed and mixed to generate a FeCocktail vaccine. Experiments showed that the FeCocktail vaccine effectively activated CD4+ and CD8+ T cells and effector memory T cells in mice. Piglets immunized with the FeCocktail vaccine generated specific antibodies and exhibited increased levels of PRRSV-specific IFN-γ produced by functional CD4+ and CD8+ cells. The FeCocktail also provided protective efficacy against PRRSV challenge, including mitigation of clinical symptoms, reduction of viral loads in serum and lungs, and the alleviation of lung tissue damage. In conclusion, this study offers a promising candidate vaccine for combating epidemic PRRSV, and affirms the utility of nanoparticle protein as a platform for next-generation PRRSV vaccine development.

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.

Construction and Immunogenicity of a Recombinant Porcine Pseudorabies Virus (PRV) Expressing the Major Neutralizing Epitope Regions of S1 Protein of Variant PEDV

Porcine epidemic diarrhea virus (PEDV) infection causes severe diarrhea and high mortality in neonatal piglets. Pseudorabies causes acute and often fatal infections in young piglets, respiratory disorders in growing pigs, and reproductive failure in sows. In late 2011, pseudorabies virus (PRV) variants occurred in Bartha-K61-vaccine-immunized swine herds, resulting in economic losses to the global pig industry. Therefore, it is essential to develop a safe and effective vaccine against both PEDV and PRV infections. In this study, we constructed a recombinant virus rPRV-PEDV S1 expressing the major neutralizing epitope region (COE, SS2, and SS6) of the PEDV S1 protein by homologous recombination technology and CRISPR/Cas9 gene editing technology, and then evaluated its biological characteristics in vitro and immunogenicity in pigs. The recombinant virus rPRV-PEDV S1 had similar growth kinetics in vitro to the parental rPRV NY-gE-/gI-/TK- strain, and was proven genetically stable in swine testicle (ST) cells and safe for piglets. PEDV S1-specific antibodies were detected in piglets immunized with rPRV-PEDV S1 on the 7th day post-immunization (dpi), and the antibody level increased rapidly at 14-21 dpi. Moreover, the immunized piglets receiving the recombinant virus exhibited alleviated clinical signs and reduced viral load compared to the unvaccinated group following a virulent PEDV HN2021 strain challenge. Also, piglets immunized with rPRV-PEDV S1 developed a PRV-specific humoral immune response and elicited complete protection against a lethal PRV NY challenge. These data indicate that the recombinant rPRV-PEDV S1 is a promising vaccine candidate strain for the prevention and control of PEDV and PRV infections.

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.