Oral administration of PEDV-dissolved Alg-CS gel induces high and sustained mucosal immunity in mice.

Porcine epidemic diarrhea (PED) is a serious disease in piglets that leads to high mortality. An effective measure that provides higher IgA levels in the intestine and milk is required to decrease losses. Porcine epidemic diarrhea virus (PEDV) was dissolved in calcium alginate (Alg) and combined with chitosan (CS) via electrostatic interactions between cationic chitosan and anionic alginate to create a porous gel (Alg-CS+PEDV). The gel was used to immunize mice orally or in combination with subcutaneous injections of inactivated PEDV vaccine. At 12 and 24 days after immunization, levels of IgA and IgG in Alg-CS+PEDV were higher than with normal PEDV oral administration. At 24 days after immunization, the concentration of IFN-γ in Alg-CS+PEDV was higher than with normal PEDV oral administration. Furthermore, oral administration combining subcutaneous immunization induced higher levels of IgG and IgA than oral administration alone. Our study provides a new method for the preparation and administration of oral vaccines to achieve enhanced mucosal immunity against PEDV.

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.

N-terminal domain of classical swine fever virus Npro induces proteasomal degradation of specificity protein 1 with reduced HDAC1 expression to evade from innate immune responses.

IMPORTANCE: Of the flaviviruses, only CSFV and bovine viral diarrhea virus express Npro as the non-structural protein which is not essential for viral replication but functions to dampen host innate immunity. We have deciphered a novel mechanism with which CSFV uses to evade the host antiviral immunity by the N-terminal domain of its Npro to facilitate proteasomal degradation of Sp1 with subsequent reduction of HDAC1 and ISG15 expression. This is distinct from earlier findings involving Npro-mediated IRF3 degradation via the C-terminal domain. This study provides insights for further studies on how HDAC1 plays its role in antiviral immunity, and if and how other viral proteins, such as the core protein of CSFV, the nucleocapsid protein of porcine epidemic diarrhea virus, or even other coronaviruses, exert antiviral immune responses via the Sp1-HDAC1 axis. Such research may lead to a deeper understanding of viral immune evasion strategies as part of their pathogenetic mechanisms.

Porcine Epidemic Diarrhea Virus Infection Induces Autophagosome Formation but Inhibits Autolysosome Formation during Replication.

In this study, we investigated the correlation between the mechanism involved in porcine epidemic diarrhea virus (PEDV) replication and autophagic flux. In this study, we found that as PEDV replicated, production of LC3-II was significantly induced up to 24 h post-infection (hpi). Interestingly, although there was significant production of LC3-II, greater p62 accumulation was simultaneously found. Pretreatment with rapamycin significantly induced PEDV replication, but autolysosome formation was reduced. These results were confirmed by the evaluation of ATG5/ATG12 and LAMP1/LAMP2. Taken together, we conclude that PEDV infection induces autophagosome formation but inhibits autolysosome formation during replication.

Predicted 3D model of the M protein of Porcine Epidemic Diarrhea Virus and analysis of its immunogenic potential.

The membrane protein M of the Porcine Epidemic Diarrhea Virus (PEDV) is the most abundant component of the viral envelope. The M protein plays a central role in the morphogenesis and assembly of the virus through protein interactions of the M-M, M-Spike (S) and M-nucleocapsid (N) type. The M protein is known to induce protective antibodies in pigs and to participate in the antagonistic response of the cellular antiviral system coordinated by the type I and type III interferon pathways. The 3D structure of the PEDV M protein is still unknown. The present work exposes a predicted 3D model of the M protein generated using the Robetta protocol. The M protein model is organized into a transmembrane and a globular region. The obtained 3D model of the PEDV M protein was compared with 3D models of the SARS-CoV-2 M protein created using neural networks and with initial machine learning-based models created using trRosetta. The 3D model of the present study predicted four linear B-cell epitopes (RSVNASSGTG and KHGDYSAVSNPSALT peptides are noteworthy), six discontinuous B-cell epitopes, forty weak binding and fourteen strong binding T-cell epitopes in the CV777 M protein. A high degree of conservation of the epitopes predicted in the PEDV M protein was observed among different PEDV strains isolated in different countries. The data suggest that the M protein could be a potential candidate for the development of new treatments or strategies that activate protective cellular mechanisms against viral diseases.

Novel Neutralizing Epitope of PEDV S1 Protein Identified by IgM Monoclonal Antibody.

Porcine epidemic diarrhea virus (PEDV) causes devastating enteric disease that inflicts huge economic damage on the swine industry worldwide. A safe and highly effective PEDV vaccine that contains only the virus-neutralizing epitopes (not enhancing epitope), as well as a ready-to-use PEDV neutralizing antibody for the passive immunization of PEDV vulnerable piglets (during the first week of life) are needed, particularly for PEDV-endemic farms. In this study, we generated monoclonal antibodies (mAbs) to the recombinant S1 domain of PEDV spike (S) protein and tested their PEDV neutralizing activity by CPE-reduction assay. The mAb secreted by one hybrodoma clone (A3), that also bound to the native S1 counterpart from PEDV-infected cells (tested by combined co-immunoprecipitation and Western blotting), neutralized PEDV infectivity. Epitope of the neutralizing mAb (mAbA3) locates in the S1A subdomain of the spike protein, as identified by phage mimotope search and multiple sequence alignment, and peptide binding-ELISA. The newly identified epitope is shared by PEDV G1 and G2 strains and other alphacoronaviruses. In summary, mAbA3 may be useful as a ready-to-use antibody for passive immunization of PEDV-susceptible piglets, while the novel neutralizing epitope, together with other, previously known protective epitopes, have potential as an immunogenic cocktail for a safe, next-generation PEDV vaccine.

LDH nanoparticle adjuvant subunit vaccine induces an effective immune response for porcine epidemic diarrhea virus.

Porcine Epidemic Diarrhea (PED) is a highly contagious intestinal disease which mostly caused by Porcine Epidemic Diarrhea Virus (PEDV). The PED has caused huge economic losses to the pig industry all over the world and a valid PEDV vaccine is needed to prevent the infection. In this study, we constructed expression plasmid based on the spike (S) gene of the epidemic PEDV strain. The recombinant eukaryotic S (Se) and prokaryotic S (Sp) subunit proteins were expressed and purified as vaccine antigens. We designed a new subunit vaccine based on S proteins, adjuvanted with layered double hydroxide (LDH). The results indicated that the LDH adjuvanted subunit vaccines induced a better immune effect in terms of antibody level and cellular immune response. In conclusion, this study showed a new design of a PEDV subunit vaccine with nanotechnology and demonstrated the potential for its clinical application.

Innate Immune Evasion of Porcine Epidemic Diarrhea Virus through Degradation of the FBXW7 Protein via the Ubiquitin-Proteasome Pathway.

Porcine epidemic diarrhea virus (PEDV) causes a porcine disease associated with swine epidemic diarrhea. Different antagonistic strategies have been identified, and the mechanism by which PEDV infection impairs the production of interferon (IFN) and delays the activation of the IFN response to escape host innate immunity has been determined, but the pathogenic mechanisms of PEDV infection remain enigmatic. Our preliminary results revealed that endogenous F-box and WD repeat domain-containing 7 (FBXW7) protein, the substrate recognition component of the SCF-type E3 ubiquitin ligase, is downregulated in PEDV-infected Vero E6 cells, according to the results from an isobaric tags for relative and absolute quantification (iTRAQ) analysis. Overexpression of FBXW7 in target cells makes them more resistant to PEDV infection, whereas ablation of FBXW7 expression by small interfering RNA (siRNA) significantly promotes PEDV infection. In addition, FBXW7 was verified as an innate antiviral factor capable of enhancing the expression of RIG-I and TBK1, and it was found to induce interferon-stimulated genes (ISGs), which led to an elevated antiviral state of the host cells. Moreover, we revealed that PEDV nonstructural protein 2 (nsp2) interacts with FBXW7 and targets FBXW7 for degradation through the K48-linked ubiquitin-proteasome pathway. Consistent with the results proven in vitro, FBXW7 reduction was also confirmed in different intestinal tissues from PEDV-infected specific-pathogen-free (SPF) pigs. Taken together, the data indicated that PEDV has evolved with a distinct antagonistic strategy to circumvent the host antiviral response by targeting the ubiquitin-proteasome-mediated degradation of FBXW7. Our findings provide novel insights into PEDV infection and pathogenesis. IMPORTANCE To counteract the host antiviral defenses, most viruses, including coronaviruses, have evolved with diverse strategies to dampen host IFN-mediated antiviral response, by interfering with or evading specific host regulators at multiple steps of this response. In this study, a novel antagonistic strategy was revealed showing that PEDV infection could circumvent the host innate response by targeted degradation of endogenous FBXW7 in target cells, a process that was verified to be a positive modulator for the host innate immune system. Degradation of FBXW7 hampers host innate antiviral activation and facilitates PEDV replication. Our findings reveal a new mechanism exploited by PEDV to suppress the host antiviral response.

A Comparative Analysis of Coronavirus Nucleocapsid (N) Proteins Reveals the SADS-CoV N Protein Antagonizes IFN-ß Production by Inducing Ubiquitination of RIG-I.

Coronaviruses (CoVs) are a known global threat, and most recently the ongoing COVID-19 pandemic has claimed more than 2 million human lives. Delays and interference with IFN responses are closely associated with the severity of disease caused by CoV infection. As the most abundant viral protein in infected cells just after the entry step, the CoV nucleocapsid (N) protein likely plays a key role in IFN interruption. We have conducted a comprehensive comparative analysis and report herein that the N proteins of representative human and animal CoVs from four different genera [swine acute diarrhea syndrome CoV (SADS-CoV), porcine epidemic diarrhea virus (PEDV), severe acute respiratory syndrome CoV (SARS-CoV), SARS-CoV-2, Middle East respiratory syndrome CoV (MERS-CoV), infectious bronchitis virus (IBV) and porcine deltacoronavirus (PDCoV)] suppress IFN responses by multiple strategies. In particular, we found that the N protein of SADS-CoV interacted with RIG-I independent of its RNA binding activity, mediating K27-, K48- and K63-linked ubiquitination of RIG-I and its subsequent proteasome-dependent degradation, thus inhibiting the host IFN response. These data provide insight into the interaction between CoVs and host, and offer new clues for the development of therapies against these important viruses.

Inhibitory effects of Lactobacillus plantarum metabolites on porcine epidemic diarrhea virus replication.

Porcine epidemic diarrhea virus (PEDV) is an enteropathogenic coronavirus; it causes diarrhea in pigs and is associated with high morbidity and mortality in sucking piglets. In this study, we performed in vitro and in vivo experiments to determine the inhibitory effects of Lactobacillus plantarum metabolites (LPM) on PEDV replication. Gas chromatography-mass spectrometry revealed exopolysaccharides to be one of the main components of LPM. We then determine whether L. plantarum exopolysaccharides (LPE) have an antiviral effect and also detected the expression levels of the apoptosis-related genes Bax and Bcl-2 and of the pro-apoptotic protein caspase-3. Further, we assessed the transcription levels of an immune-related protein (STAT1) and antiviral factors (MX1, MX2, ISG15, ZAP, PKR, and OAS1). Our results showed that the most effective method was to pretreat cells with LPM and that the optimal dose of LPM that could be safely administered to Vero cells was 1/8 times of the stock solution. LPE had a strong inhibitory effect on PEDV; the most effective method of administration was to co-incubate cells with LPE and PEDV, and the optimal concentration of LPE was 1.35 mg/mL. To conclude, LPE prevented PEDV adsorption and also alleviated inflammatory responses and induced early apoptosis of injured cells, but it could not regulate the immune function of cells.

Assessing the risk of recurrence of porcine epidemic diarrhea virus in affected farms on Jeju Island, South Korea.

BACKGROUND: Porcine epidemic diarrhea virus (PEDV) is a swine enteropathogenic coronavirus that has devastated the swine industry in South Korea over the last 30 years. The lack of an effective method to control the endemics has led to a surge in PEDV recurrences in affected farms throughout the country. OBJECTIVES: In the first step toward establishing systematic monitoring of and active control measures over the swine populations, we constructed an assessment model that evaluates the status of (1) biosecurity, (2) herd immunity, and (3) virus circulation in each of the PEDV-infected farms. METHODS: A total of 13 farrow-to-finish pig farms with a history of acute PEDV infection on Jeju Island were chosen for this study. The potential risk of the recurrence in these farms was estimated through on-site data collection and laboratory examination. RESULTS: Overall, the data indicated that a considerable number of the PEDV-infected farms had lax biosecurity, achieved incomplete protective immunity in the sows despite multi-dose vaccination, and served as incubators of the circulating virus; thus, they face an increased risk of recurrent outbreaks. Intriguingly, our results suggest that after an outbreak, a farm requires proactive tasks, including reinforcing biosecurity, conducting serological and virus monitoring to check the sows' immunity and to identify the animals exposed to PEDV, and improving the vaccination scheme and disinfection practices if needed. CONCLUSIONS: The present study highlights the significance of coordinated PEDV management in infected farms to reduce the risk of recurrence and further contribute towards the national eradication of PEDV.

Porcine Epidemic Diarrhea Virus Membrane Protein Interacted with IRF7 to Inhibit Type I IFN Production during Viral Infection.

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic porcine enteropathogenic coronavirus causing severe enteritis and lethal watery diarrhea in piglets. PEDV infection suppresses the synthesis of type I IFN, and multiple viral proteins of PEDV have been shown to target the adaptors of innate immune pathways to inhibit type I IFN production. In this study, we identified PEDV membrane (M) protein as a new antagonist of type I IFN production in both human embryonic kidney HEK293T cells and porcine kidney PK-15 cells and determined the antagonistic mechanism used by M protein to target IFN regulatory factor 7 (IRF7), an important regulator of type I IFN production. IRF7 is phosphorylated and activated by TBK1 and IKKε in response to viral infection. We found that PEDV M protein interacted with the inhibitory domain of IRF7 and significantly suppressed TBK1/IKKε-induced IRF7 phosphorylation and dimerization of IRF7, leading to the decreased expression of type I IFN, although it did not affect the interaction between TBK1/IKKε and IRF7. As expected, overexpression of M protein significantly increased PEDV replication in porcine cells. The M proteins of both epidemic PEDV strains and vaccine strain showed similar antagonistic effect on type I IFN production, and the 1-55 region of M protein was essential for disruption of IRF7 function by interacting with IRF7. Taken together, our data identified a new, to our knowledge, IFN antagonist of PEDV, as well as a novel, to our knowledge, antagonistic mechanism evolved by PEDV to inhibit type I IFN production.

The construction of recombinant Lactobacillus casei vaccine of PEDV and its immune responses in mice.

BACKGROUND: Porcine epidemic diarrhea (PED) is a contagious intestinal disease caused by porcine epidemic diarrhea virus (PEDV) characterized by vomiting, diarrhea, anorexia, and dehydration, which have caused huge economic losses around the world. At present, vaccine immunity is still the most effective method to control the spread of PED. In this study, we have constructed a novel recombinant L. casei-OMP16-PEDVS strain expressing PEDVS protein of PEDV and OMP16 protein of Brucella abortus strain. To know the immunogenicity of the recombinant L. casei-OMP16-PEDVS candidate vaccine, it was compared with BL21-OMP16-PEDVS-F, BL21-OMP16-PEDVS, and BL21-PEDVS recombinant protein. RESULTS: The results showed that we could detect higher levels of IgG, neutralizing antibody, IL-4, IL-10, and INF-γ in serum and IgA in feces of L. casei-OMP16-PEDVS immunized mice, which indicated that L. casei-OMP16-PEDVS candidate vaccine could induce higher levels of humoral immunity, cellular immunity, and mucosal immunity. CONCLUSION: Therefore, L. casei-OMP16-PEDVS is a promising candidate vaccine for prophylaxis of PEDV infection.

Expression and Purification of a PEDV-Neutralizing Antibody and Its Functional Verification.

Porcine epidemic diarrhea virus (PEDV) is a highly infectious and pathogenic virus causing high morbidity and mortality, especially in newborn piglets. There remain problems with contemporary PEDV vaccines, in part because of the rapid variation of PEDV, poor conferred immunity, and numerous side effects. The ability to produce PEDV-neutralizing antibodies suggests that we may be able to increase the success rate of PEDV prevention in piglets using these antibodies. In this study, we produced an anti-PEDV S protein monoclonal antibody (anti-PEDV mAb-2) that neutralized PEDV-CV777 (a G1 strain), PEDV-SDSX16 and PEDV-Aj1102 (two G2 strains). In vivo challenge experiments demonstrated that anti-PEDV mAb-2 inhibited the PEDV infection in piglets. We also produced three HEK293 cell lines that expressed anti-PEDV mAb-2. Overall, our study showed that anti-PEDV mAb-2 produced from hybridoma supernatants effectively inhibited PEDV infection in piglets, and the recombinant HEK293 cell lines expressed anti-PEDV mAb-2 genes.

Killed whole-genome reduced-bacteria surface-expressed coronavirus fusion peptide vaccines protect against disease in a porcine model.

As the coronavirus disease 2019 (COVID-19) pandemic rages on, it is important to explore new evolution-resistant vaccine antigens and new vaccine platforms that can produce readily scalable, inexpensive vaccines with easier storage and transport. We report here a synthetic biology-based vaccine platform that employs an expression vector with an inducible gram-negative autotransporter to express vaccine antigens on the surface of genome-reduced bacteria to enhance interaction of vaccine antigen with the immune system. As a proof-of-principle, we utilized genome-reduced Escherichia coli to express SARS-CoV-2 and porcine epidemic diarrhea virus (PEDV) fusion peptide (FP) on the cell surface, and evaluated their use as killed whole-cell vaccines. The FP sequence is highly conserved across coronaviruses; the six FP core amino acid residues, along with the four adjacent residues upstream and the three residues downstream from the core, are identical between SARS-CoV-2 and PEDV. We tested the efficacy of PEDV FP and SARS-CoV-2 FP vaccines in a PEDV challenge pig model. We demonstrated that both vaccines induced potent anamnestic responses upon virus challenge, potentiated interferon-γ responses, reduced viral RNA loads in jejunum tissue, and provided significant protection against clinical disease. However, neither vaccines elicited sterilizing immunity. Since SARS-CoV-2 FP and PEDV FP vaccines provided similar clinical protection, the coronavirus FP could be a target for a broadly protective vaccine using any platform. Importantly, the genome-reduced bacterial surface-expressed vaccine platform, when using a vaccine-appropriate bacterial vector, has potential utility as an inexpensive, readily manufactured, and rapid vaccine platform for other pathogens.

PEDV Infection Generates Conformation-Specific Antibodies That Can Be Effectively Detected by a Cell-Based ELISA.

Porcine epidemic diarrhea virus (PEDV) is a coronavirus that causes serious and highly contagious enteric disease in swine worldwide. In this study, we constructed a recombinant baculovirus (S-Bac) expressing full-length spike protein of the virulent epidemic genotype 2b (G2b) PEDV strain for serological studies of infected pigs. We found that most spike-specific antibodies produced upon PEDV infection in pigs are conformation-specific and they could be detected on S-Bac-infected insect cells by immunofluorescent assay, but they were insensitive to Western blot analysis, the typical method for antiserum analysis. These results indicated that spike conformation is crucial for serum recognition. Since it is difficult to purify trimeric spike membrane protein for conventional enzyme-linked immunosorbent assay (ELISA), we used S-Bac to generate a novel cell-based ELISA for convenient PEDV detection. We analyzed 100 pig serum samples, and our cell-based ELISA exhibited a sensitivity of 100%, a specificity of 97%, and almost perfect agreement [Cohen's kappa coefficient value (κ) = 0.98] with immunocytochemical staining results. Our cell-based ELISA rapidly presented antigen for proper detection of conformation-specific antibodies, making PEDV detection more convenient, and it will be useful for detecting many viral diseases in the future.

Assessment of three commercial ELISAs for the detection of antibodies against Porcine epidemic diarrhea virus at different stages of the immune response.

Three commercial ELISAs -two based on spike (E1 and E3) and one on nucleocapsid protein (E2)-were used to analyze the development and persistence of antibodies against Porcine epidemic diarrhea virus (PEDV). Seventy-five four-week-old PEDV-negative piglets were inoculated orally with a European G1b PEDV (INOC) and fourteen were kept as controls (CTRL). After the inoculation, E3 detected positive animals as soon as 7 days post inoculation (dpi), while the earliest detection with E1 and E2 was at 14 dpi. All samples were positive at 21 and 28 dpi using E1 and E3, respectively, while E2 failed to detect 23.3 % of the inoculated pigs at any time point. The percentages of positive samples were different through the study: E1 and E3 > E2 from 14 to 56 dpi; and E3 > E1 > E2 from 56 to 154 dpi (P < 0.05). Five months after the inoculation, E3 still detected 92.0 % (IC95 % = 85.1-98.8 %) of pigs as positive, while E1 and E2 detected only 27.0 % (IC95 % = 16.0-37.9 %) and 0%, respectively. The sensitivity for E2 never exceeded 0.62. Specificity was 1 for all ELISAs. These different outcomes could be related to the ELISA strategies (indirect versus competition), the antigens used, the cut-off, or to other intrinsic factors of each test. The observed differences could be of importance when assessing whether older animals, such as fatteners or gilts, had previously been in contact with PEDV.

Porcine epidemic diarrhea virus E protein suppresses RIG-I signaling-mediated interferon-ß production.

Porcine epidemic diarrhea virus (PEDV) encodes many multifunctional proteins that inhibit host innate immune response during virus infection. As one of important structural proteins, PEDV E protein has been found to block the production of type I interferon (IFN) in virus life cycle, but little is known about this process that E protein subverts host innate immune. Thus, in this present study, we initiated the construction of eukaryotic expression vectors to express PEDV E protein. Subsequently, cellular localization analysis was performed and the results showed that the majority of PEDV E protein distributed at cytoplasm and localized in endoplasmic reticulum (ER). Over-expression of PEDV E protein significantly inhibited poly(I:C)-induced IFN-ß and IFN-stimulated genes (ISGs) productions. We also found that PEDV E protein remarkably suppressed the protein expression of RIG-I signaling-associated molecules, but all their corresponding mRNA levels remained unaffected and unchanged. Furthermore, PEDV E protein obviously interfered with the translocation of IRF3 from cytoplasm to nucleus through direct interaction with IRF3, which is crucial for the IFN-ß production induced by poly(I:C). Taken together, our results suggested that PEDV E protein acts as an IFN-ß antagonist through suppression of the RIG-I-mediated signaling. This study will pave the way for the further investigation into the molecular mechanisms by which PEDV E protein evades host innate immune response.

Immunodominant and Neutralizing Linear B-Cell Epitopes Spanning the Spike and Membrane Proteins of Porcine Epidemic Diarrhea Virus.

Porcine epidemic diarrhea virus (PEDV) is the causative agent of PED, an enteric disease that causes high mortality rates in piglets. PEDV is an alphacoronavirus that has high genetic diversity. Insights into neutralizing B-cell epitopes of all genetically diverse PEDV strains are of importance, particularly for designing a vaccine that can provide broad protection against PEDV. In this work, we aimed to explore the landscape of linear B-cell epitopes on the spike (S) and membrane (M) proteins of global PEDV strains. All amino acid sequences of the PEDV S and M proteins were retrieved from the NCBI database and grouped. Immunoinformatics-based methods were next developed and used to identify putative linear B-cell epitopes from 14 and 5 consensus sequences generated from distinct groups of the S and M proteins, respectively. ELISA testing predicted peptides with PEDV-positive sera revealed nine novel immunodominant epitopes on the S protein. Importantly, seven of these novel immunodominant epitopes and other subdominant epitopes were demonstrated to be neutralizing epitopes by neutralization-inhibition assay. Our findings unveil important roles of the PEDV S2 subunit in both immune stimulation and virus neutralization. Additionally, our study shows the first time that the M protein is also the target of PEDV neutralization with seven neutralizing epitopes identified. Conservancy profiles of the epitopes are also provided. In this study, we offer immunoinformatics-based methods for linear B-cell epitope identification and a more complete profile of linear B-cell epitopes across the PEDV S and M proteins, which may contribute to the development of a greater next-generation PEDV vaccine as well as peptide-based immunoassays.

Immune Responses in Pregnant Sows Induced by Recombinant Lactobacillus johnsonii Expressing the COE Protein of Porcine Epidemic Diarrhea Virus Provide Protection for Piglets against PEDV Infection.

Porcine epidemic diarrhea (PED) induced by porcine epidemic diarrhea virus (PEDV) is an intestinal infectious disease in pigs that causes serious economic losses to the pig industry. To develop an effective oral vaccine against PEDV infection, we used a swine-origin Lactobacillus johnsonii (L. johnsonii) as an antigen delivery carrier. A recombinant strain pPG-T7g10-COE/L. johnsonii (L. johnsonii-COE) expressing COE protein (a neutralizing epitope of the viral spike protein) was generated. The immunomodulatory effect on dendritic cell in vitro and immunogenicity in pregnant sows was evaluated following oral administration. L. johnsonii-COE could activate monocyte-derived dendritic cell (MoDC) maturation and triggered cell immune responses. After oral vaccination with L. johnsonii-COE, levels of anti-PEDV-specific serum IgG, IgA, and IgM antibodies as well as mucosal secretory immunoglobulin A (SIgA) antibody were induced in pregnant sows. High levels of PEDV-specific SIgA and IgG antibodies were detected in the maternal milk, which provide effective protection for the piglets against PEDV infection. In summary, oral L. johnsonii-COE was able to efficiently activate anti-PEDV humoral and cellular immune responses, demonstrating potential as a vaccine for use in sows to provide protection of their piglets against PEDV.