The New Porcine Epidemic Diarrhea Virus Outbreak May Mean That Existing Commercial Vaccines Are Not Enough to Fully Protect Against the Epidemic Strains

Lactoferrin exhibits PEDV antiviral activity by interfering with spike-heparan sulfate proteoglycans binding and activating mucosal immune response

Neonatal piglets infected with Porcine Epidemic Diarrhea Virus (PEDV) experience a mortality rate of up to 90%, resulting in significant economic losses to the swine industry in China. Current strategies using specific antibodies in sow milk to prevent Porcine Epidemic Diarrhea (PED) in these piglets through specific antibodies in sow milk is unsatisfactory. Preliminary studies have shown limited success. Emerging evidence suggests that general immune factors in sow milk provide protection to neonatal piglets, particularly, lactoferrin, play a crucial role in protecting piglets by inhibiting PEDV replication. However, the precise mechanism by which lactoferrin exerts its antiviral effects remains unclear. This study sought to clarify these mechanisms through both in vitro and in vivo approaches, proposing that higher concentrations of lactoferrin lead to greater antiviral activity. It was hypothesized that lactoferrin can impede PEDV by blocking its binding to heparan sulfate proteoglycans (HSPG) on the surface of target cells, and molecular docking experiments was conducted to identify the binding sites between lactoferrin and HSPG. Additionally, the findings indicated that lactoferrin can effectively trigger the maturation of porcine dendritic cells and boosts their antigen-presenting functions, thereby improving intestinal mucosal immunity in neonatal piglets against PEDV. Overall, these findings aid to elucidate the antiviral actions and mechanisms of lactoferrin in sow colostrum, offering new insights for the effective prevention and control of PED in neonatal piglets.

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.

Porcine epidemic diarrhea virus strain CH/HLJ/18 isolated in China: characterization and phylogenetic analysis

BACKGROUND

Porcine epidemic diarrhea (PED) is an infectious disease of the digestive tract caused by the porcine epidemic diarrhea virus (PEDV), characterized by vomiting, severe diarrhea, and high mortality rates in piglets. In recent years, the distribution of this disease in China has remarkably increased, and its pathogenicity has also increased. PEDV has been identified as the main cause of viral diarrhea in piglets. This study aimed to understand the genetic evolution and diversity of PEDV to provide a theoretical basis for the development of new vaccines and the prevention and treatment of PED.

METHODS

A PEDV strain was isolated from the small intestine of a diarrheal piglet using Vero cells. The virus was identified using reverse transcription-polymerase chain reaction (RT-PCR), indirect immunofluorescence assay (IFA), and transmission electron microscopy. The whole genome sequence was sequenced, phylogenetic analysis was conducted using MEGA (version 7.0), and recombination analysis was performed using RDP4 and SimPlot. The S protein amino acid sequence was aligned using Cluster X (version 2.0), and the S protein was modeled using SWISS-MODEL to compare differences in structure and antigenicity. Finally, the piglets were inoculated with PEDV to evaluate its pathogenicity in newborn piglets.

RESULT

PEDV strain CH/HLJ/18 was isolated. CH/HLJ/18 shared 89.4-99.2% homology with 52 reference strains of PEDV belonging to the GII-a subgroup. It was a recombinant strain of PEDV BJ-2011-1 and PEDV CH_hubei_2016 with a breakpoint located in ORF1b. Unique amino acid deletions and mutations were observed in the CH/HLJ/18 S protein. The piglets then developed severe watery diarrhea and died within 7 d of inoculation with CH/HLJ/18, suggesting that CH/HLJ/18 was highly pathogenic to newborn piglets.

CONCLUSION

A highly pathogenic recombinant PEDV GII-a strain, CH/HLJ/18, was identified in China, with unique deletion and mutation of amino acids in the S protein that may lead to changes in protein structure and antigenicity. These results will be crucial for understanding the prevalence and variation of PEDV and for preventing and controlling PED.

A novel CpG ODN compound adjuvant enhances immune response to spike subunit vaccines of porcine epidemic diarrhea virus

CpG oligodeoxynucleotides (CpG ODNs) boost the humoral and cellular immune responses to antigens through interaction with Toll-like receptor 9 (TLR9). These CpG ODNs have been extensively utilized in human vaccines. In our study, we evaluated five B-type CpG ODNs that have stimulatory effects on pigs by measuring the proliferation of porcine peripheral blood mononuclear cells (PBMCs) and assessing interferon gamma (IFN-γ) secretion. Furthermore, this study examined the immunoenhancing effects of the MF59 and CpG ODNs compound adjuvant in mouse and piglet models of porcine epidemic diarrhea virus (PEDV) subunit vaccine administration. The in vitro screening revealed that the CpG ODN named CpG5 significantly stimulated the proliferation of porcine PBMCs and elevated IFN-γ secretion levels. In the mouse vaccination model, CpG5 compound adjuvant significantly bolstered the humoral and cellular immune responses to the PEDV subunit vaccines, leading to Th1 immune responses characterized by increased IFN-γ and IgG2a levels. In piglets, the neutralizing antibody titer was significantly enhanced with CpG5 compound adjuvant, alongside a considerable increase in CD8+ T lymphocytes proportion. The combination of MF59 adjuvant and CpG5 exhibits a synergistic effect, resulting in an earlier, more intense, and long-lasting immune response in subunit vaccines for PEDV. This combination holds significant promise as a robust candidate for the development of vaccine adjuvant.

Porcine Epidemic Diarrhea Virus: Etiology, Epidemiology, Antigenicity, and Control Strategies in China

Porcine epidemic diarrhea virus (PEDV) is a porcine enteric coronavirus, which is one of the main causative agents of porcine epidemic diarrhea (PED), with 100% morbidity and 80-100% mortality in neonatal piglets. Since 2010, large-scale PED caused by highly pathogenic variants of PEDV has occurred successively in China and other countries in the world, posing a great threat to the global pig industry. It has been demonstrated in many investigations that the classic attenuated vaccine strain, PEDV CV777, is insufficient to fully protect against the PEDV variants. Moreover, the maternally derived antibodies elicited by inactivated vaccines also cannot completely protect piglets from infection. In addition, feedback feeding poses a risk of periodic PEDV recurrence in pig farms, making it challenging to successfully limit the spread of PEDV in China. This review focuses on the etiology, epidemiology, antigenicity, and control strategies of PEDV in China and provides information for the formulation of effective control measures.

Transcriptome Profiling of Vero E6 Cells during Original Parental or Cell-Attenuated Porcine Epidemic Diarrhea Virus Infection

Porcine epidemic diarrhea virus (PEDV) has led to significant economic losses in the global porcine industry since the emergence of variant strains in 2010. The high mutability of coronaviruses endows PEDV with the ability to evade the host immune response, which impairs the effectiveness of vaccines. In our previous study, we generated a highly cell-passaged PEDV strain, CT-P120, which showed promise as a live attenuated vaccine candidate by providing satisfactory protection against variant PEDV infection in piglets. However, the mechanism by which the attenuated CT-P120 adapts to cells during passage, resulting in increased replication efficiency, remains unclear. To address this question, we conducted a comparative transcriptomic analysis of Vero E6 cells infected with either the original parental strain (CT-P10) or the cell-attenuated strain (CT-P120) of PEDV at 6, 12, and 24 h post-infection. Compared to CT-P10, CT-P120 infection resulted in a significant decrease in the number of differentially expressed genes (DEGs) at each time point. Functional enrichment analysis of genes revealed the activation of various innate immune-related pathways by CT-P10, notably attenuated during CT-P120 infection. To validate these results, we selected eight genes (TRAF3, IRF3, IFNL1, ISG15, NFKB1, MAP2K3, IL1A, and CCL2) involved in antiviral processes and confirmed their mRNA expression patterns using RT-qPCR, in line with the transcriptomic data. Subsequent protein-level analysis of selected genes via Western blotting and enzyme-linked immunosorbent assay corroborated these results, reinforcing the robustness of our findings. Collectively, our research elucidates the strategies underpinning PEDV attenuation and immune evasion, providing invaluable insights for the development of effective PEDV vaccines.

Genomic Characterizations of Porcine Epidemic Diarrhea Viruses (PEDV) in Diarrheic Piglets and Clinically Healthy Adult Pigs from 2019 to 2022 in China

Porcine epidemic diarrhea virus (PEDV) is a major causative pathogen of diarrheic disease. In this study, the prevalence and evolution of PEDV was evaluated using intestinal samples collected from six provinces of China in 2019-2022. PEDV could not only be detected in diarrheic piglets but also in adult pigs without enteric diseases. The complete genomes of five temporal and geographical representative PEDV strains were determined. Genome-based phylogenetic analysis indicated that XJ1904-700 belongs to the G2-a subgroup, while the other strains are clustered within the S-INDEL subgroup. Recombination analyses supported that JSNJ2004-919 is an inter-subgroup recombinant from SD2014-like (G2-b), CHZ-2013-like (G2-b) and CV777-like (G1-b) isolates, while FJFZ2004-1017 is an intra-subgroup recombinant from XM1-2-like (S-INDEL) and LYG-2014-like (S-INDEL) isolates. Both JSNJ2004-919 and FJFZ2004-1017 were from adult pigs, providing evidence that adult pigs may also serve as the host of PEDV reservoirs for virus evolution. Overall, this study provides new insights into PEDV's prevalence and evolution in both diseased piglets and clinically healthy adult pigs.

Targeting the PEDV 3CL protease for identification of small molecule inhibitors: an insight from virtual screening, ADMET prediction, molecular dynamics, free energy landscape, and binding energy calculations

BACKGROUND

The porcine epidemic diarrhea virus (PEDV) represents a major health issue for piglets worldwide and does significant damage to the pork industry. Thus, new therapeutic approaches are urgently needed to manage PEDV infections. Due to the current lack of a reliable remedy, this present study aims to identify novel compounds that inhibit the 3CL protease of the virus involved in replication and pathogenesis.

RESULTS

To identify potent antiviral compounds against the 3CL protease, a virtual screening of natural compounds (n = 97,999) was conducted. The top 10 compounds were selected based on the lowest binding energy and the protein-ligand interaction analyzed. Further, the top five compounds that demonstrated a strong binding affinity were subjected to drug-likeness analysis using the ADMET prediction, which was followed by molecular dynamics simulations (500 ns), free energy landscape, and binding free energy calculations using the MM-PBSA method. Based on these parameters, four putative lead (ZINC38167083, ZINC09517223, ZINC04339983, and ZINC09517238) compounds were identified that represent potentially effective inhibitors of the 3CL protease.

CONCLUSION

Therefore, these can be utilized for the development of novel antiviral drugs against PEDV. However, this requires further validation through in vitro and in vivo studies.

Adenovirus vector-mediated single chain variable fragments target the nucleocapsid protein of porcine epidemic diarrhea virus and protect against viral infection in piglets

Porcine epidemic diarrhea virus (PEDV) mainly infects the intestinal epithelial cells of pigs, causing porcine epidemic diarrhea (PED). In particular, the virus causes severe diarrhea, dehydration, and death in neonatal piglets. Maternal immunity effectively protects neonatal piglets from PEDV infection; however, maternal antibodies can only prevent PEDV attachment and entry into target cells, but have no effects on intracellular viruses. Intracellular antibodies targeting virus-encoded proteins are effective in preventing viral infection. We previously identified four single chain variable fragments (scFvs), ZW1-16, ZW3-21, ZW1-41, and ZW4-16, which specifically targeted the PEDV N protein and significantly inhibited PEDV replication and up-regulated interferon-λ1 (IFN-λ1) expression in host cells. In our current study, the four scFvs were subcloned into replication-defective adenovirus vectors to generate recombinant adenoviruses rAdV-ZW1-16, rAdV-ZW3-21, rAdV-ZW1-41, and rAdV-ZW4-16. ScFvs were successfully expressed in Human Embryonic Kidney 293 (HEK293) cells and intestinal porcine epithelial cell line J2 (IPEC-J2) and were biosafe for piglets as indicated by body temperature and weight, scFv excretion in feces, IFN-γ and interleukin-4 (IL-4) expression in jejunum, and pathological changes in porcine tissue after oral administration. Western blotting, immunofluorescence, and immunohistochemical analyses showed that scFvs were expressed in porcine jejunum. The prophylactic effects of rAdV-ZW, a cocktail of the four rAdV-scFvs, on piglet diarrhea caused by PEDV was investigated. Clinical symptoms in piglets orally challenged with PEDV, following a two-time treatment with rAdV-ZW, were significantly reduced when compared with PEDV-infected piglets treated with phosphate buffered saline (PBS) or rAdV-wild-type. Also, no death and jejunal lesions were observed. ScFv co-localization with the PEDV N protein in vivo was also observed. Next, the expression of pro-inflammatory serum cytokines such as tumor necrosis factor-α (TNF-α), IL-6, IL-8, IL-12, and IFN-λ was assessed by enzyme-linked immunosorbent assay (ELISA), which showed that scFvs significantly suppressed PEDV-induced pro-inflammatory cytokine expression and restored PEDV-inhibited IFN-λ expression. Therefore, our study supported a promising role for intracellular scFvs targeting the PEDV N protein to prevent and treat diarrhea in PEDV-infected piglets.

Resistance of Field-Isolated Porcine Epidemic Diarrhea Virus to Interferon and Neutralizing Antibody

Variant porcine epidemic diarrhea virus (PEDV), belonging to the genogroup G2b, has higher pathogenicity and mortality than classical PEDV, belonging to the genogroup G1a. To understand the pathogenesis of the G2b PEDV, we examined the resistance of the G2b PEDV to interferon (IFN) and neutralizing antibodies, which are important for controlling PEDV infection. We found that the G2b PEDV showed higher resistance to IFN than G1a PEDV. The G1a PEDV could replicate in IFN-deficient Vero cells, but not in IFN-releasing porcine alveolar macrophages, whereas the G2b PEDV showed similar infectivity in both types of cells. We also found that G2b PEDV was not effectively blocked by neutralizing antibodies, unlike G1a PEDV, suggesting differences in the antigenicity of the two strains. These results provide an understanding of the occurrence of variant PEDV and its pathogenesis.

hnRNP K Degrades Viral Nucleocapsid Protein and Induces Type I IFN Production to Inhibit Porcine Epidemic Diarrhea Virus Replication

Porcine epidemic diarrhea virus (PEDV) is a re-emerging enteric coronavirus currently spreading in several nations and inflicting substantial financial damages on the swine industry. The currently available coronavirus vaccines do not provide adequate protection against the newly emerging viral strains. It is essential to study the relationship between host antiviral factors and the virus and to investigate the mechanisms underlying host immune response against PEDV infection. This study shows that heterogeneous nuclear ribonucleoprotein K (hnRNP K), the host protein determined by the transcription factor KLF15, inhibits the replication of PEDV by degrading the nucleocapsid (N) protein of PEDV in accordance with selective autophagy. hnRNP K was found to be capable of recruiting the E3 ubiquitin ligase, MARCH8, aiming to ubiquitinate N protein. Then, it was found that the ubiquitinated N protein could be delivered into autolysosomes for degradation by the cargo receptor NDP52, thereby inhibiting PEDV proliferation. Moreover, based on the enhanced MyD88 expression, we found that hnRNP K activated the interferon 1 (IFN-1) signaling pathway. Overall, the data obtained revealed a new mechanism of hnRNP K-mediated virus restriction wherein hnRNP K suppressed PEDV replication by degradation of viral N protein using the autophagic degradation pathway and by induction of IFN-1 production based on upregulation of MyD88 expression. IMPORTANCE The spread of the highly virulent PEDV in many countries is still leading to several epidemic and endemic outbreaks. To elucidate effective antiviral mechanisms, it is important to study the relationship between host antiviral factors and the virus and to investigate the mechanisms underlying host immune response against PEDV infection. In the work, we detected hnRNP K as a new host restriction factor which can hinder PEDV replication through degrading the nucleocapsid protein based on E3 ubiquitin ligase MARCH8 and the cargo receptor NDP52. In addition, via the upregulation of MyD88 expression, hnRNP K could also activate the interferon (IFN) signaling pathway. This study describes a previously unknown antiviral function of hnRNP K and offers a new vision toward host antiviral factors that regulate innate immune response as well as a protein degradation pathway against PEDV infection.

Triacetyl Resveratrol Inhibits PEDV by Inducing the Early Apoptosis In Vitro

PEDV represents an ancient Coronavirus still causing huge economic losses to the porcine breeding industry. Resveratrol has excellent antiviral effects. Triacetyl resveratrol (TCRV), a novel natural derivative of resveratrol, has been recently discovered, and its pharmacological effects need to be explored further. This paper aims to explore the relationship between PEDV and TCRV, which offers a novel strategy in the research of antivirals. In our study, Vero cells and IPEC-J2 cells were used as an in vitro model. First, we proved that TCRV had an obvious anti-PEDV effect and a strong inhibitory effect at different time points. Then, we explored the mechanism of inhibition of PEDV infection by TCRV. Our results showed that TCRV could induce the early apoptosis of PEDV-infected cells, in contrast to PEDV-induced apoptosis. Moreover, we observed that TCRV could promote the expression and activation of apoptosis-related proteins and release mitochondrial cytochrome C into cytoplasm. Based on these results, we hypothesized that TCRV induced the early apoptosis of PEDV-infected cells and inhibited PEDV infection by activating the mitochondria-related caspase pathway. Furthermore, we used the inhibitors Z-DEVD-FMK and Pifithrin-α (PFT-α) to support our hypothesis. In conclusion, the TCRV-activated caspase pathway triggered early apoptosis of PEDV-infected cells, thereby inhibiting PEDV infections.

Isolation and oral immunogenicity assessment of porcine epidemic diarrhea virus NH-TA2020 strain: One of the predominant strains circulating in China from 2017 to 2021

Porcine epidemic diarrhea (PED) caused by porcine epidemic diarrhea virus (PEDV) is one of the most devastating diseases in the global pig industry due to its high mortality rate in piglets. Maternal vaccines can effectively enhance the gut-mammary gland-secretory IgA axis to boost lactogenic immunity and passive protection of nursing piglets against PEDV challenge. From 2017 to 2021, we collected 882 diarrhea samples from 303 farms in China to investigate the epidemiology of PEDV. The result showed that about 52.15% (158/303) of the farms were positive for PEDV with an overall detection rate of 63.95% (564/882) of the samples. The S1 fragments of S gene from 104 strains were sequenced for the phylogenetic analysis. A total of 71 PEDV strains (68.27%) sequenced in this study were clustered into the predominant G2c subgroup, while the newly-defined G2d strains (9.62%) were identified in three provinces of China. The NH-TA2020 strain of G2c subgroup was isolated and cultured, and its infection to piglets caused watery diarrhea within 24 ​h, indicating its strong pathogenicity. Oral administration of NH-TA2020 strain to pregnant gilts stimulated high levels of IgA antibody in colostrum. The piglets fed by the gilts above were challenged with NH-TA2020 strain or CH–HeB-RY-2020 strain from G2d subgroup, and the clinical symptoms and virus shedding were significantly reduced compared to the mock group. Our findings suggest that G2c subgroup is the predominant branch circulating in China from 2017 to 2021. Oral administration of NH-TA2020 enhances maternal IgA and lactogenic immune responses, which confer protection against the homologous and emerging G2d PEDV strains challenges in neonates.

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From 2017 to 2021, PEDV positive rate of Chinese farms and samples tested in this study was 52.15% and 63.95%, respectively.

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A total of 71 sequenced PEDV strains (68.27%) were clustered into the predominant G2c subgroup.

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The newly-defined G2d strains (9.62%) were identified in three provinces of China.

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NH-TA2020 strain belonging to the G2c subgroup was isolated and its strong pathogenicity was confirmed.

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The milk containing high levels of IgA antibody induced by NH-TA2020 strain could protect piglets against PEDV challenge.

FUBP3 Degrades the Porcine Epidemic Diarrhea Virus Nucleocapsid Protein and Induces the Production of Type I Interferon

Porcine epidemic diarrhea virus (PEDV) is the globally distributed alphacoronavirus that can cause lethal watery diarrhea in piglets, causing substantial economic damage. However, the current commercial vaccines cannot effectively the existing diseases. Thus, it is of great necessity to identify the host antiviral factors and the mechanism by which the host immune system responds against PEDV infection required to be explored. The current work demonstrated that the host protein, the far upstream element-binding protein 3 (FUBP3), could be controlled by the transcription factor TCFL5, which could suppress PEDV replication through targeting and degrading the nucleocapsid (N) protein of the virus based on selective autophagy. For the ubiquitination of the N protein, FUBP3 was found to recruit the E3 ubiquitin ligase MARCH8/MARCHF8, which was then identified, transported to, and degraded in autolysosomes via NDP52/CALCOCO2 (cargo receptors), resulting in impaired viral proliferation. Additionally, FUBP3 was found to positively regulate type-I interferon (IFN-I) signaling and activate the IFN-I signaling pathway by interacting and increasing the expression of tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3). Collectively, this study showed a novel mechanism of FUBP3-mediated virus restriction, where FUBP3 was found to degrade the viral N protein and induce IFN-I production, aiming to hinder the replication of PEDV.

IMPORTANCE PEDV refers to the alphacoronavirus that is found globally and has re-emerged recently, causing severe financial losses. In PEDV infection, the host activates various host restriction factors to maintain innate antiviral responses to suppress virus replication. Here, FUBP3 was detected as a new host restriction factor. FUBP3 was found to suppress PEDV replication via the degradation of the PEDV-encoded nucleocapsid (N) protein via E3 ubiquitin ligase MARCH8 as well as the cargo receptor NDP52/CALCOCO2. Additionally, FUBP3 upregulated the IFN-I signaling pathway by interacting with and increasing tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) expression. This study further demonstrated that another layer of complexity could be added to the selective autophagy and innate immune response against PEDV infection are complicated.

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.

Oral Administration of Coronavirus Spike Protein Provides Protection to Newborn Pigs When Challenged with PEDV

To investigate whether oral administration of maize-produced S antigen can provide passive immunity to piglets against porcine epidemic diarrhea virus (PEDV), 16 pregnant sows were randomly assigned to one of four treatments: (1) injection of PEDV vaccine (INJ), (2) maize grain without S protein (CON), (3) maize grain containing low dose of S antigen (LOV) and (4) maize grain containing a high dose of S antigen (HOV). Vaccines were administered on days 57, 85 and 110 of gestation. Sows’ serum and colostrum were collected at farrowing and milk on day 6 post-challenge to quantify neutralizing antibodies (NABs) and cytokines. Piglets were challenged with PEDV 3–5 d after farrowing, and severity of disease and mortality assessed on day 11 post-challenge. Disease severity was lower in LOV and INJ compared with HOV and CON, whereas the survival rate increased in piglets from LOV sows compared with HOV and CON (p ≤ 0.001). Higher titers of NABs and lower levels of cytokine granulocyte-macrophage colony-stimulating factor in sows’ milk were positively correlated with piglet survivability (p ≤ 0.05). These data suggest that feeding S protein in corn to pregnant sows protects nursing piglets against PEDV.