An inactivated vaccine made from a U.S. field isolate of porcine epidemic disease virus is immunogenic in pigs as demonstrated by a dose-titration

Porcine Epidemic Diarrhea: Insights and Progress on Vaccines

Porcine epidemic diarrhea (PED) is a swine-wasting disease caused by coronavirus infection. It causes great economic damage to the swine industry worldwide. Despite the continued use of vaccines, PED outbreaks continue, highlighting the need to review the effectiveness of current vaccines and develop additional vaccines based on new platforms. Here, we review existing vaccine technologies for preventing PED and highlight promising technologies that may help control PED virus in the future.

Intranasally inoculated bacterium-like particles displaying porcine epidemic diarrhea virus S1 protein induced intestinal mucosal immune response in mice

Porcine epidemic diarrhea virus (PEDV) causes acute watery diarrhea and high mortality in newborn piglets. Activation of intestinal mucosal immunity is crucial to anti-PEDV infection. To develop a vaccine capable of stimulating intestinal mucosal immunity, we prepared a bacterium (Lactococcus lactis)-like particle (BLP) vaccine (S1-BLPs) displaying the S1 protein, a domain of PEDV spike protein (S), based on gram-positive enhancer matrix (GEM) particle display technology. We further compared the effects of different vaccination routes on mucosal immune responses in mice induced by S1-BLPs. The specific IgG titer in serum of intramuscularly immunized mice with S1-BLPs was significantly higher than that of the intranasally administered. The specific IgA antibody was found in the serum and intestinal lavage fluid of mice vaccinated intranasally, but not intramuscularly. Moreover, the intranasally inoculated S1-BLPs induced higher levels of IFN-γ and IL-4 in serum than the intramuscularly inoculated. In addition, the ratio of serum IgG2a/IgG1 of mice inoculated intramuscularly was significantly higher with S1-BLPs compared to that of with S1 protein, suggesting that the immune responses induced by S1-BLPs was characterized by helper T (Th) cell type 1 immunity. The results indicated that S1-BLPs induced systemic and local immunity, and the immunization routes significantly affected the specific antibody classes and Th immune response types. The intranasally administered S1-BLPs could effectively stimulate intestinal mucosal specific secretory IgA response. S1-BLPs have the potential to be developed as PEDV mucosal vaccine.

Designing a multi-epitope vaccine to control porcine epidemic diarrhea virus infection using immunoinformatics approaches

Porcine epidemic diarrhea virus (PEDV), a continuously evolving pathogen, causes severe diarrhea in piglets with high mortality rates. However, current vaccines cannot provide complete protection against PEDV, so vaccine development is still necessary and urgent. Here, with the help of immunoinformatics approaches, we attempted to design a multi-epitope vaccine named rPMEV to prevent and control PEDV infection. The epitopes of rPMEV were constructed by 9 cytotoxic T lymphocyte epitopes (CTLs), 11 helper T lymphocyte epitopes (HTLs), 6 linear B cell epitopes (LBEs), and 4 conformational B cell epitopes (CBEs) based on the S proteins from the four representative PEDV G2 strains. To enhance immunogenicity, porcine β-defensin-2 (PBD-2) was adjoined to the N-terminal of the vaccine as an adjuvant. All of the epitopes and PBD-2 were joined by corresponding linkers and recombined into the multivalent vaccine, which is stable, antigenic, and non-allergenic. Furthermore, we adopted molecular docking and molecular dynamics simulation methods to analyze the interaction of rPMEV with the Toll-like receptor 4 (TLR4): a stable interaction between them created by 13 hydrogen bonds. In addition, the results of the immune simulation showed that rPMEV could stimulate both cellular and humoral immune responses. Finally, to raise the expression efficiency, the sequence of the vaccine protein was cloned into the pET28a (+) vector after the codon optimization. These studies indicate that the designed multi-epitope vaccine has a potential protective effect, providing a theoretical basis for further confirmation of its protective effect against PEDV infection in vitro and in vivo studies.

Recombinant human adenovirus type 5 based vaccine candidates against GIIa- and GIIb-genotype porcine epidemic diarrhea virus induce robust humoral and cellular response in mice

Porcine epidemic diarrhea virus (PEDV) is a porcine enteropathogenic coronavirus causing severe watery diarrhea, vomiting, dehydration, and death in piglets. However, most commercial vaccines are developed based on the GI genotype strains, and have poor immune protection against the currently dominant GII genotype strains. Therefore, four novel replication-deficient human adenovirus 5-vectored vaccines expressing codon-optimized forms of the GIIa and GIIb strain spike and S1 glycoproteins were constructed, and their immunogenicity was evaluated in mice by intramuscular (IM) injection. All the recombinant adenoviruses generated robust immune responses, and the immunogenicity of recombinant adenoviruses against the GIIa strain was stronger than that of recombinant adenoviruses against the GIIb strain. Moreover, Ad-XT-tPA-Sopt-vaccinated mice elicited optimal immune effects. In contrast, mice immunized with Ad-XT-tPA-Sopt by oral gavage did not induce strong immune responses. Overall, IM administration of Ad-XT-tPA-Sopt is a promising strategy against PEDV, and this study provides useful information for developing viral vector-based vaccines.

Lactate is useful for the efficient replication of porcine epidemic diarrhea virus in cell culture

Porcine epidemic diarrhea virus (PEDV) is a deadly pathogen infecting pig herds, and has caused significant economic losses around the world. Vaccination remains the most effective way of keeping the PEDV epidemic under control. Previous studies have shown that the host metabolism has a significant impact on viral replication. In this study, we have demonstrated that two substrates of metabolic pathway, glucose and glutamine, play a key role in PEDV replication. Interestingly, the boosting effect of these compounds toward viral replication appeared to be dose-independent. Furthermore, we found that lactate, which is a downstream metabolite, promotes PEDV replication, even when added in excess to the cell culture medium. Moreover, the role of lactate in promoting PEDV was independent of the genotype of PEDV and the multiplicity of infection (MOI). Our findings suggest that lactate is a promising candidate for use as a cell culture additive for promoting PEDV replication. It could improve the efficiency of vaccine production and provide the basis for designing novel antiviral strategies.

Visual and Rapid Detection of Porcine Epidemic Diarrhea Virus (PEDV) Using Reverse Transcription Loop-Mediated Isothermal Amplification Method

Porcine epidemic diarrhea virus (PEDV) can cause severe infectious porcine epidemic diarrhea (PED) and infect different ages of pigs, resulting in sickness and death among suckling pigs. For PEDV detection, finding an effective and rapid method is a priority. In this study, we established an effective reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for PEDV detection. Three sets of primers, specific for eight different sequences of the PEDV N gene, were designed in this study. The optimized RT-LAMP amplification program was as follows: 59 min at 61.9 °C and 3 min at 80 °C. The RT-LAMP results were confirmed with the addition of SYBR Green I fluorescence dye and with the detection of a ladder-like band by conventional gel electrophoresis analysis, which demonstrated a significant agreement between the two methods. The LOD of PEDV by RT-LAMP was 0.0001 ng/μL. Compared with RT-LAMP, the traditional RT-PCR method is 100-fold less sensitive. The RT-LAMP results had no cross-reaction with porcine parvovirus (PPV), porcine circovirus type 1 (PCV1), porcine pseudorabies virus (PRV), porcine circovirus type 2 (PCV2), rotavirus (RV), transmissible gastroenteritis virus (TGEV) and porcine reproductive and respiratory syndrome virus (PRRSV). Consequently, the newly developed RT-LAMP method could provide an accurate and reliable tool for PEDV diagnosis.

Prevention and Control of Porcine Epidemic Diarrhea: The Development of Recombination-Resistant Live Attenuated Vaccines

Porcine epidemic diarrhea (PED), causing up to 100% mortality in neonatal pigs, is a highly contagious enteric disease caused by PED virus (PEDV). The highly virulent genogroup 2 (G2) PEDV emerged in 2010 and has caused huge economic losses to the pork industry globally. It was first reported in the US in 2013, caused country-wide outbreaks, and posed tremendous hardship for many pork producers in 2013–2014. Vaccination of pregnant sows/gilts with live attenuated vaccines (LAVs) is the most effective strategy to induce lactogenic immunity in the sows/gilts and provide a passive protection via the colostrum and milk to suckling piglets against PED. However, there are still no safe and effective vaccines available after about one decade of endeavor. One of the biggest concerns is the potential reversion to virulence of an LAV in the field. In this review, we summarize the status and the major obstacles in PEDV LAV development. We also discuss the function of the transcriptional regulatory sequences in PEDV transcription, contributing to recombination, and possible strategies to prevent the reversion of LAVs. This article provides insights into the rational design of a promising LAV without safety issues.

Porcine Epidemic Diarrhea: Causative Agent, Epidemiology, Clinical Characteristics, and Treatment Strategy Targeting Main Protease

Aims:

This aimed to study the causative agent, epidemiology, clinical characteristics, and treatment strategy targeting the main protease in porcine epidemic diarrhea.

Background:

Porcine epidemic diarrhea (PED) is a contagious intestinal viral infection causing severe diarrhea, vomiting, and dehydration in pigs. High rates of mortalities and severe morbidities, approaching 100%, are reported in piglets infected with PEDV. In recent years, PED has been observed to influence the swine-farming nations in Europe, Asia, the USA, South Korea, and Canada. The PED virus (PEDV) transmission takes place through a faecal-oral route.

Objective:

The objective is to review the characteristics of PEDV and its role in the disease. In addition, we aim to outline some possible methods to combat PED infection, including targeting the main protease of coronavirus and their future perspectives.

Method:

This study is a review of literature on the PED virus.

Results:

Apart from symptomatic treatment and supportive care, there is no available specific treatment for PEDV. Appropriate disinfectants and cleaning are pivotal for the control of PEDV. To date, apart from anti-PEDV inhibitors, there are no specific drugs available commercially to treat the disease. Therefore, 3C-like protease (3CLpro) in PEDV that has highly conserved structure and catalytic mechanism serves as an alluring drug as it plays a vital role during viral polyprotein processing at the time of infection.

Conclusion:

A well synchronized and collective effort of scientists, swine veterinarians, pork industry experts, and associated authorities is essential for the accomplishment of proper execution of these required measures.

Inactivated Pseudomonas PE(ΔIII) exotoxin fused to neutralizing epitopes of PEDV S proteins produces a specific immune response in mice

Porcine epidemic diarrhea (PED) caused by the porcine epidemic diarrhea virus (PEDV), is a severe infectious and devastating swine disease that leads to serious economic losses in the swine industry worldwide. An increased number of PED cases caused by variant PEDV have been reported in many countries since 2010. S protein is the main immunogenic protein containing some B-cell epitopes that can induce neutralizing antibodies of PEDV. In this study, the construction, expression and purification of Pseudomonas aeruginosa exotoxin A (PE) without domain III (PEΔIII) as a vector was performed for the delivery of PEDV S-A or S-B. PE(ΔIII) PEDV S-A and PE(ΔIII) PEDV S-B recombinant proteins were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. The immunogenicity of PEDV S-A and PEDV S-B subunit vaccines were evaluated in mice. The results showed that PEDV-S-B vaccine could not only induce specific humoral and Th1 type-dominant cellular immune responses, but also stimulate PEDV-specific mucosal immune responses in mice. PEDV-S-B subunit vaccine is a novel candidate mucosal vaccine against PEDV infection.

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

Background: On October 30, 2020, piglets and sows in the farrowing house of a pig farm in Jiangxi showed clinical symptoms such as anorexia, watery diarrhea, and vomiting. Epidemiological test, clinical necropsy, and RT-PCR test were carried out on the pig farm for diagnosis. After comprehensive considerations, the disease was judged as porcine epidemic diarrhea virus infection.

Results: Thereafter, a series of comprehensive prevention and control measures such as emergency vaccination with autogenous vaccines were adopted. Half a month after inoculation with autogenous vaccines for the farm, the mortality rate of newborn piglets in the farrowing house began to decline, and production gradually returned to being stable. The second-generation sequencing analysis and phylogenetic analysis showed that the porcine epidemic diarrhea virus (PEDV) sequence obtained from the stool and small intestine samples of the diseased pigs on the farm was 97.8% homologous to the vaccine strain. At the same time, antibody testing found that the vaccinated pigs on the pig farm had satisfactory immune response.

Conclusion: This case indicated that the PEDV outbreak on the pig farm might aggravate owing to the strain being mutated and could escape the immune protection of the existing vaccine. This case has accumulated technical data for the clinical prevention and control of porcine epidemic diarrhea.

Aloe extract inhibits porcine epidemic diarrhea virus in vitro and in vivo

Porcine epidemic diarrhea virus (PEDV) causes severe diarrhoea and high mortality in neonatal suckling piglets, leading to significant economic losses to the swine industry. Currently there are no adequate control strategies against circulating PEDV variants, making an urgent need to exploit effect antiviral therapies to compensate for vaccines. Here, we report that Aloe extract can hamper completely the proliferation of PEDV at a non-cytotoxic concentration of 16 mg/mL determined by CCK-8 assay in Vero and IPEC-J2 cells in vitro. Furthermore, time course analysis indicated the extract exerted its inhibition at the late stage of the viral life cycle. Moreover, we also confirmed that the extract can inactivated PEDV directly but did not act on the viral genome and S1 protein. Importantly, the extract at a relatively safety concentration of 100 mg/kg of body weight, which was confirmed in mice, could reduce virus load and pathological change in intestinal tract of pigs and protect newborn piglets from lethal challenge with highly pathogenic PEDV variant GDS01 infection, indicating that Aloe extract efficiently inhibited PEDV infection in vivo. Collectively, our findings suggest that the aqueous extract from the Aloe could inhibit PEDV replication in vitro and in vivo and might be a good target for drug development against PEDV.

Genetic variations in S gene of porcine epidemic diarrhoea virus from 2018 in Sichuan Province, China

Porcine epidemic diarrhoea virus (PEDV) belongs to the family Coronavirus, a genus of coronavirus, a highly contact‐infectious intestinal disease pathogen. In this study, we downloaded 62 PEDV S gene sequences uploaded to GenBank, including 10 uploaded by our laboratory from 2018, and constructed a PEDV S gene evolution tree using MEGA V7.0 software. Phylogenetic tree analysis indicated that the genogroup of PEDV in Sichuan Province was divided into three coexisting genogroups (GII‐a, GII‐b and GI‐a), of them, GII‐a has become the main genogroup in the province due to its prevalence and range of spread. Amino acid sequence analysis showed that there were amino acid insertions and deletions in the S protein encoded by the amplified S gene, and there were amino acid mutations in the COE and SS6 of the epitope in the amplified S protein. These results provide a basic research theory for understanding the prevalence of PEDV variation and controlling PED in Sichuan.

A Minimally Replicative Vaccine Protects Vaccinated Piglets Against Challenge With the Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea virus (PEDV), is an economically important enteric coronavirus, with over a 90% mortality rate in neonatal piglets. The virus emerged in the US in 2013, resulting in severe production losses. Effective vaccine development against PEDV is a challenge. Inactivated vaccines are of questionable efficacy. Attenuated vaccines, while more effective, require a relatively long lead development time, are associated with safety concerns and are also unable to prevent new field outbreaks. To combine the safety and efficacy advantages of inactivated and attenuated PEDV vaccines, respectively, in this study, we tested the hypothesis that subjecting PEDV virions to heat treatment at 44°C for 10 min to reversibly unfold structural proteins, followed by exposure to RNAse to fragment the genome, would result in a vaccine preparation with intact viral structure/antigenicity but highly diminished replicative abilities. We expected the vaccine to be both safe and effective in a piglet challenge model. Following the heat and RNAse treatment, PEDV virions had an intact electron microscopic ultrastructure and were amplified only in the 3rd passage in Vero cells, indicating that diminished replication was achieved in vitro. Strong PEDV spike-protein specific and virus neutralizing antibody responses were elicited in vaccinated piglets. Upon challenge, all vaccinated pigs were protected against fecal viral shedding and intestinal pathology, while the unvaccinated controls were not. The vaccine virus was not detected in the fecal matter of vaccinated pigs prior to challenge; nor did they develop intestinal lesions. Thus, the described approach has significant promise in improving current approaches for PEDV immunization.

Upregulation of CD4+CD8+ memory cells in the piglet intestine following oral administration of Bacillus subtilis spores combined with PEDV whole inactivated virus

Oral immunization is a commonly employed route for inducing local immunity. However, the application of oral immunization is limited by the short-term persistence of immunity, particularly for inactivated viruses. The ultimate goal for mucosal vaccination is to stimulate protective immunological memory. In the intestine, long-term persistence of immunity is related to CD4⁺CD8⁺ memory T-cells. In this study, piglets were orally immunized with Bacillus subtilis spores (B.s) plus whole inactivated porcine epidemic diarrhea virus (PEDV WIV), followed by booster oral immunization. Initially, the results showed that B.s plus PEDV WIV enhanced the anti-PEDV capability on mucosal surfaces, as evidenced by plaque reduction neutralization tests in serum and intestinal fluid. Elevated antigen-specific IgG titers in the serum and IgA titers in saliva, feces and nasal washing liquid were also observed. Meanwhile, B.s plus PEDV WIV increased the area of Peyer's patches and the number of intraepithelial lymphocytes in the ileum of piglets. Similarly, the percentage of CD4⁺CD8⁺ memory T-cells were upregulated and proliferation ability of antigen-specific memory T-cell was strengthened in intestinal mucosal-associated lymphocytes, which was accompanied with increased expression of CCR9 after oral immunization with B.s plus PEDV WIV. In addition, the activation of memory T-cells is correlated with the increased mRNA expression of Toll-like receptor 2 and 4, as well as interleukin-6 and induced by B.s. Collectively, the study provided further insight into the potential immunopotentiator ability of B.s to assist PEDV WIV in the potentiation of immunity by upregulating memory CD4⁺CD8⁺ T cells via oral immunization.

Antiviral effect of lithium chloride on porcine epidemic diarrhea virus in vitro

Porcine epidemic diarrhea virus (PEDV), a member of the Coronaviridae family, causes acute diarrhea, vomiting, dehydration, and high mortality rates in neonatal piglets. Severe outbreaks of PEDV variants have re-emerged in Asia and North America since 2010, causing tremendous economic losses to the swine industry. The lack of effective therapeutic treatment promotes the research for new antivirals. Lithium chloride (LiCl) has been reported as a potential antiviral drug for certain viruses. In this study, the antiviral effect of LiCl on PEDV in Vero cells was evaluated. Real-time quantitative PCR and indirect immunofluorescence assay indicated that LiCl effectively inhibited the entry and replication of PEDV in Vero cells. The expression of viral RNA and protein of PEDV in Vero cells was suppressed in a dose-dependent manner by LiCl. Moreover, addition of LiCl inhibited both early and late cell apoptosis induced by PEDV. Our data implied that LiCl could be a potential antiviral drug against PEDV infection. Further studies are required to explore the antiviral effect of lithium chloride on PEDV infection in vivo.

Efficacy of inactivated variant porcine epidemic diarrhea virus vaccines in growing pigs

PURPOSE

The first aim of this study was to develop a novel inactivated porcine epidemic diarrhea virus (PEDV) vaccine using the recently isolated Korean PEDV QIAP1401 strain and to evaluate its protective efficacy in growing pigs. The second was to determine the optimum adjuvant formulation of the inactivated PEDV vaccine that induces protection against viral challenge.

MATERIALS AND METHODS

To generate high titers of infectious PEDV, the QIAP1401 isolate was passaged in Vero cells. The experimental vaccines were prepared from a binary ethyleneimine-inactivated QIAP1401 strain passaged sequentially 70 times (QIAP1401-p70), formulated with four commercial adjuvants, and administered twice intramuscularly to growing pigs. Challenge studies using a virulent homologous strain of PEDV QIAP1401-p11, which was passaged 11 times after isolation, were performed to assess protection against disease progression and viral shedding during the 15-day observation period. The vaccine-induced antibody responses were measured in serum samples collected at predetermined time points by indirect enzyme-linked immunosorbent assay and virus neutralization test.

RESULTS

The QIAP1401-p70 strain had 42 amino acid (aa) mutations, including a 25 aa deletion, and was selected as the inactivated PEDV vaccine candidate. Although none of the pigs that received the experimental vaccines were completely protected against subsequent viral challenge, they exhibited a significantly higher immune response than did non-vaccinated control pigs. Among the vaccine groups, the highest antibody responses were observed in the pigs that received an oil-based multiphasic water/oil/water (W/O/W) emulsion adjuvanted vaccine, which delayed the onset of clinical symptoms and viral shedding.

CONCLUSION

A novel inactivated PEDV vaccine formulated with a W/O/W emulsion adjuvant was both immunogenic and protective against viral challenge.

Trypsin-independent porcine epidemic diarrhea virus US strain with altered virus entry mechanism

BACKGROUND

Porcine Epidemic Diarrhea Virus (PEDV) is a coronavirus that infects the intestinal tract and causes diarrhea and vomiting in older pigs or extreme dehydration and death that could reach 100% mortality in neonatal piglets. In the US, the first PEDV outbreaks occurred in 2013 and since then US PEDV strains have quickly spread throughout the US and worldwide, causing significant economic and public health concerns. Currently two conditionally approved vaccines exist in the US, but there is no live attenuated vaccine, which is considered the best option in controlling PEDV by inducing transferrable mucosal immunity to susceptible neonatal piglets. In this study, we passaged an US PEDV isolate under various conditions to generate three strains and characterized their growth and antigenicity in cell culture using various assays including Western blot analysis, serum neutralization assay, sequencing analysis and confocal microscopy. Finally, these strains were evaluated for pathogenicity in nursing piglets (1-4 days old).

RESULTS

One of the PEDV strains generated in this study (designated as PEDV 8aa) is able to replicate in cells without any protease and grows to a high titer of >8 log10 TCID50/ml in cell culture. Interestingly, replication of PEDV 8aa was severely reduced by trypsin and this correlated with the inhibition of virus attachment and entry into the cells. In neonatal nursing piglets, PEDV 8aa (passage number 70 or 105) was found to be fully attenuated with limited virus shedding.

CONCLUSIONS

These results suggest that applying selective pressure during viral passages can facilitate attainment of viral attenuation and that PEDV 8aa warrants further investigation as an attenuated vaccine.

Evaluation of the efficacy of a commercial inactivated genogroup 2b-based porcine epidemic diarrhea virus (PEDV) vaccine and experimental live genogroup 1b exposure against 2b challenge

Porcine epidemic diarrhea virus strains from the G1b cluster are considered less pathogenic compared to the G2b cluster. The aim of this study was to compare the ability of G1b-based live virus exposure against use of a commercial G2b–based inactivated vaccine to protect growing pigs against G2b challenge. Thirty-nine PEDV naïve pigs were randomly divided into five groups: EXP-IM-1b (intramuscular G1b exposure; G2b challenge), EXP-ORAL-1b (oral G1b exposure; G2b challenge), VAC-IM-2b (intramuscular commercial inactivated G2b vaccination; G2b challenge), POS-CONTROL (sham-vaccination; G2b challenge) and NEG-CONTROL (sham-vaccination; sham-challenge). Pigs were vaccinated/exposed at 3 weeks of age (day post-vaccination 0, dpv 0), VAC-IM-2b pigs were revaccinated at dpv 14, and the pigs were challenged at dpv 28. Among all groups, VAC-IM-2b pigs had significantly higher anti-PEDV IgG levels on dpv 21 and 28 while EXP-ORAL-1b pigs had significantly higher anti-PEDV IgA levels on dpv 14, 21, 28 and 35. EXP-ORAL-1b also had detectable IgA in feces. Intramuscular PEDV exposure did not result in a detectable antibody response in EXP-IM-1b pigs. The fecal PEDV RNA levels in VAC-IM-2b pigs were significantly lower 5–7 days after challenge compared to the POS-CONTROL group. Under the study conditions a commercial inactivated G2b-based vaccine protected pigs against G2b challenge, as evidenced by reduction of PEDV RNA in feces for 3–4 logs during peak shedding and a shorter viral shedding duration. The oral, but not the intramuscular, experimental G1b-based live virus exposure induced a high anti-PEDV IgA response prior to challenge, which apparently did not impact PEDV shedding compared to POS-CONTROL pigs.

Porcine epidemic diarrhea in China

Porcine epidemic diarrhea (PED) is a contagious intestinal disease caused by Porcine epidemic diarrhea virus (PEDV) that characterized by vomiting, diarrhea, and dehydration. PEDV was first identified in the 1980s in China, and since then, it has become one of the most common viral causes of diarrhea. In October 2010, a large-scale outbreak of PED caused by a PEDV variant occurred in China, resulting in tremendous economic losses. This review presents a comprehensive description of PEDV history, prevalence, molecular features, and prevention and control strategies in China.

Porcine epidemic diarrhea virus: An overview of current virological and serological diagnostic methods

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Molecular assays such as rRT-PCR are the method of choice for PEDV diagnosis.

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Multiplex rRT-PCR allow simultaneous testing for PEDV, TGEV and PDCoV.

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Serological assays provide valuable information on previous exposure to PEDV and population immunity.

Porcine epidemic diarrhea virus (PEDV) is the causative agent of an acute, highly contagious, and severe enteric disease that leads to high mortality rates in suckling piglets. Therefore, accurate diagnosis of PEDV infection is critical for the implementation of control measures for the virus. Many diagnostic tests have been recently developed and are currently available for the detection of PEDV, its proteins or nucleic acid, including virus isolation, immunofluorescence (IF) or immunohistochemistry (IHC), polymerase chain reaction (PCR) and isothermal amplification assays. Additionally, several serological assays have been developed and are currently used for the detection of antibodies against PEDV. Molecular assays such as real-time reverse transcriptase-PCR (rRT-PCR) became the methods of choice for the diagnosis of PEDV infection, providing sensitive, specific and rapid detection of the virus RNA in clinical samples. Whereas serological assays have been widely used to monitor prior exposure to the virus and to evaluate the efficacy of novel vaccine candidates or vaccination strategies. Here we discuss the properties of current PEDV diagnostic assays and prospects for improving diagnostic strategies in the future.

Structural basis for the dimerization and substrate recognition specificity of porcine epidemic diarrhea virus 3C-like protease

Porcine epidemic diarrhea virus (PEDV), a member of the genus Alphacoronavirus, has caused significant damage to the Asian and American pork industries. Coronavirus 3C-like protease (3CL^pro), which is involved in the processing of viral polyproteins for viral replication, is an appealing antiviral drug target. Here, we present the crystal structures of PEDV 3CL^pro and a molecular complex between an inactive PEDV 3CL^pro variant C144A bound to a peptide substrate. Structural characterization, mutagenesis and biochemical analysis reveal the substrate-binding pockets and the residues that comprise the active site of PEDV 3CL^pro. The dimerization of PEDV 3CL^pro is similar to that of other Alphacoronavirus 3CL^pros but has several differences from that of SARS-CoV 3CL^pro from the genus Betacoronavirus. Furthermore, the non-conserved motifs in the pockets cause different cleavage of substrate between PEDV and SARS-CoV 3CL^pros, which may provide new insights into the recognition of substrates by 3CL^pros in various coronavirus genera.

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The substrate binding mechanism of PEDV 3CL^pro has been characterized.

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The large buried surface area is responsible for dimerization of PEDV 3CL^pro.

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Non-conserved motifs cause different cleavage between PEDV and SARS-CoV 3CL^pros.

Microbiological characterization of a newly established pig breed, Aachen Minipigs

BACKGROUND

To alleviate the shortage of human donor organs or tissues for the treatment of organ and tissue failure including diabetes, pigs are considered suitable donor animals. As organs from conventional pigs are usually too large, those from minipigs may be better suited. We recently characterized the Göttingen Minipigs, a breed well characterized concerning the presence of zoonotic microorganisms and found hepatitis E virus (HEV) and porcine cytomegalovirus (PCMV) in some animals. Here, we characterize another minipig, the Aachen Minipig (AaMP), a pig breed recently established close to the town Aachen in Germany.

METHODS

The animals were tested for the prevalence and expression of porcine endogenous retroviruses (PERVs) and the presence of some selected microorganisms, among them HEV, PCMV, and porcine lymphotropic herpesviruses (PLHVs) using highly sensitive and specific PCR and RT-PCR methods. In addition, we screened for antibodies against HEV and PLHV.

RESULTS

PERV-A, PERV-B, and PERV-C sequences were found in the genome of all Aachen Minipigs. HEV RNA was found by real-time RT-PCR in most, and DNA of PCMV, PLHV-2, and PLHV-3 was found by PCR in some animals. The animals were free of eight other microorganisms tested, but some were seropositive for porcine circovirus 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine epidemic diarrhea virus (PEDV).

CONCLUSION

Based on medical examinations by veterinarians, the AaMP are in a good health status and seem to harbor only few microorganisms. To improve their status for use as donor pigs in xenotransplantation, the viruses detected might be eliminated by selection of negative animals, Cesarean section, and vaccination.

Collection and review of updated scientific epidemiological data on porcine epidemic diarrhoea

Porcine epidemic diarrhoea (PED) is a non-zoonotic viral disease of pigs caused by a coronavirus and characterised by watery diarrhoea and weight loss. PED is not notifiable to the EU or World Organisation for Animal Health listed but it is notifiable at the national level in Finland, France, Ireland and Sweden. PED case reports from seven countries and PED surveillance and monitoring activities in thirteen countries were reported. This information was combined with an extensive literature review to provide an update on global PED occurrence, circulating strains and impact in 2014-2015. PED confirmed cases have been reported in North America, South America, Asia and Europe. PED virus (PEDV) sequences originating from EU pig herds indicate that the strains currently in circulation share nearly 100% sequence identity and have greater than 99% sequence identity with the reference INDEL (insertion/deletion) strain USA/OH851/2014. In 2014-2015, greater genetic variability has been reported in strains circulating in Asia compared with EU Member States and a non-INDEL strain has been detected in the Ukraine in 2014. Data on impact confirms that mortality is higher in suckling piglets and diarrhoea is observed in all age groups. The reported impact is in agreement with that reported in EFSA AHAW Panel (2014) indicating that the impact of recently reported PED outbreaks in Asia and the USA seems to be more severe than that described in EU countries, although the impact of different PEDV strains is difficult to compare between one country and another, as impact is dependent not only on pathogenicity but also on factors such as biosecurity, herd size, farm management, sanitary status or herd immune status.

Porcine epidemic diarrhoea: new insights into an old disease

Porcine epidemic diarrhea (PED) is an enteric disease in swine caused by an alphacoronavirus. It affects swine of all ages causing acute diarrhoea and can lead to severe dehydration and death in suckling piglets. Being recognized for the first time in Europe and Asia during the seventies and the eighties, respectively, it has remained a relevant cause of diarrhea outbreaks in Asia for years and to the present. It has become a major concern in swine production since 2013 when the virus was detected for first time in the USA and in other American countries causing a high number of pig deaths and significant economic losses. The present review aims at approaching the reader to the state of the art of PED giving answer to some of the most recent questions which have arisen related to this disease.