Correlation between the IgG/IgA Antibody Response against PEDV Structural Protein and Virus Neutralization

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

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

Feeding Sows with Multi-Species Probiotics During Late Pregnancy and the Lactating Period Influences IgA Concentration in Colostrum and Subsequently Increases the Survival Rate of Piglets in Porcine Epidemic Diarrhea Outbreak Herd

Porcine epidemic diarrhea (PED) virus is an important cause of diarrhea in sows and piglets [...].

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

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

Efficacy evaluation of a bivalent subunit vaccine against epidemic PEDV heterologous strains with low cross-protection

Variant Porcine epidemic diarrhea virus (PEDV), which causes diarrhea and high mortality in piglets, has become a major pathogen, and co-epidemics of different subtypes of the virus have become a very thorny problem for the clinical prevention and control of PEDV. However, cross-protection between epidemic G2a and G2b subtype strains has not been observed, and there is currently no vaccine against both G2a and G2b strains. In this study, we demonstrate the low cross-protection between G2a and G2b strains with piglet immunization and challenge tests. The trimeric full-length S proteins of G2a and G2b variants were purified and a bivalent subunit vaccine against PEDV G2a/G2b-S was developed. In active and passive immune protection tests, the bivalent subunit vaccine produced high neutralizing antibody titers and S-specific immunoglobulin G (IgG) and IgA titers against both the G2a and G2b strains in piglets and sows. In the attack phase of the viruses, the clinical symptoms and microscopic lesions in the immunized groups were significantly alleviated. Importantly, the PEDV G2a/G2b-S bivalent subunit vaccine conferred effective passive immunity against PEDV G2a and G2b challenges in the form of colostrum-derived antibodies from the immunized sows. In conclusion, our data demonstrate the low cross-protection of PEDV epidemic G2a and G2b strains and show that the G2a/G2b-S bivalent subunit vaccine is protective against both G2a and G2b strains. It is therefore a candidate vaccine for PEDV prevention.

IMPORTANCE

The detection rate of PEDV G2a subtype strains is currently increasing. Although commercial vaccines are available, most vaccines do not exert an ideal protective effect against these strains. Furthermore, there is no definitive research into the cross-protection between G2a and G2b strains, and no bivalent vaccine provides joint protection against both. Therefore, in this study, we investigated the cross-protection between PEDV G2a and G2b strains and designed a candidate bivalent subunit vaccine combining the trimeric S proteins of the G2a and G2b subtypes. We demonstrate that the cross-protection between strains G2a and G2b is poor and that this bivalent subunit vaccine protects piglets from viral attack by inducing both active and passive immunity. This study emphasizes the effectiveness of the PEDV G2a/G2b-S bivalent subunit vaccine and provides a feasible method for the development of efficient PEDV vaccines.

Development and evaluation of a monoclonal antibody-based competitive ELISA for detecting porcine deltacoronavirus antibodies

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that can cause acute diarrhea and vomiting in newborn piglets and poses a potential risk for cross-species transmission. It is necessary to develop an effective serological diagnostic tool for the surveillance of PDCoV infection and vaccine immunity effects. In this study, we developed a monoclonal antibody-based competitive ELISA (cELISA) that selected the purified recombinant PDCoV nucleocapsid (N) protein as the coating antigen to detect PDCoV antibodies. To evaluate the diagnostic performance of the cELISA, 122 swine serum samples (39 positive and 83 negative) were tested and the results were compared with an indirect immunofluorescence assay (IFA) as the reference method. By receiver operating characteristic (ROC) curve analysis, the optimum cutoff value of percent inhibition (PI) was determined to be 26.8%, which showed excellent diagnostic performance, with an area under the curve (AUC) of 0.9919, a diagnostic sensitivity of 97.44% and a diagnostic specificity of 96.34%. Furthermore, there was good agreement between the cELISA and virus neutralization test (VNT) for the detection of PDCoV antibodies, with a coincidence rate of 92.7%, and the κ analysis showed almost perfect agreement (κ = 0.851). Overall, the established cELISA showed good diagnostic performance, including sensitivity, specificity and repeatability, and can be used for diagnostic assistance, evaluating the response to vaccination and assessing swine herd immunity.

Serum IgA antibody level against porcine epidemic diarrhea virus is a potential pre-evaluation indicator of immunization effects in sows during parturition under field conditions

BACKGROUND

Porcine Epidemic Diarrhea (PED) is a highly contagious disease caused by Porcine Epidemic Diarrhea Virus (PEDV), resulting in a mortality rate of suckling piglets as high as 100%. Vaccination is the primary strategy for controlling PEDV infection, however, there is currently a lack of reliable methods for assessing the efficacy of vaccination. This study aimed to analyze serum and colostrum samples from 75 parturient sows with a specific vaccination strategy to measure levels of IgG, IgA, and neutralizing antibodies (nAbs) against PEDV, and to investigate the correlation between serum and colostrum antibody levels, as well as to identify potential biomarkers that can be used to evaluate immunization effects under field conditions.

RESULTS

The findings of correlation analysis between antibody levels of IgA, IgG, and nAbs in serum or colostrum samples revealed that IgG demonstrated the most robust correlation with nAbs exhibiting a correlation coefficient of 0.64 in serum samples. Conversely, IgA exhibited the highest correlation with nAbs, with a correlation coefficient of 0.47 in colostrum samples. Additionally, the correlation analysis of antibody levels between serum and colostrum samples indicated that serum IgA displayed the strongest correlation with colostrum IgA, with a coefficient of 0.63, indicating that serum IgA may serve as a viable alternative indicator for evaluating IgA levels in colostrum samples. To further evaluate the suitability of serum IgA as a substitute marker for colostrum IgA, levels of IgA antibodies in serum samples from sows were examined both pre- and post-parturition. The findings indicated that serum IgA levels were initially low prior to the initial immunization, experienced a notable rise 21 days after immunization, and maintained a significant elevation compared to pre-immunization levels from 21 days pre-parturition to 14 days postpartum, spanning a total of 35 days.

CONCLUSIONS

Serum anti-PEDV IgA antibody levels may serve as a valuable predictor for immunization effects, allowing for the assessment of colostrum IgA antibody levels up to 21 days in advance. This insight could enable veterinarians to timely adjust or optimize immunization strategies prior to parturition, thereby ensuring adequate passive immunity is conferred to piglets through colostral transfer postpartum.

PEDV-spike-protein-expressing mRNA vaccine protects piglets against PEDV challenge

Porcine epidemic diarrhea virus (PEDV), a swine enteropathogenic coronavirus, causes severe diarrhea in neonatal piglets, which is associated with a high mortality rate. Thus, developing effective and safe vaccines remains a top priority for controlling PEDV infection. Here, we designed two lipid nanoparticle (LNP)-encapsulated mRNA (mRNA-LNP) vaccines encoding either the full-length PEDV spike (S) protein or a multiepitope chimeric spike (Sm) protein. We found that the S mRNA-LNP vaccine was superior to the Sm mRNA-LNP vaccine at inducing antibody and cellular immune responses in mice. Evaluation of the immunogenicity and efficacy of the S mRNA vaccine in piglets confirmed that it induced robust PEDV-specific humoral and cellular immune responses in vivo. Importantly, the S mRNA-LNP vaccine not only protected actively immunized piglets against PEDV but also equipped neonatal piglets with effective passive anti-PEDV immunity in the form of colostrum-derived antibodies after the immunization of sows. Our findings suggest that the PEDV-S mRNA-LNP vaccine is a promising candidate for combating PEDV infection.IMPORTANCEPorcine epidemic diarrhea virus (PEDV) continues to harm the global swine industry. It is important to develop a highly effective vaccine to control PEDV infection. Here, we report a PEDV spike (S) mRNA vaccine that primes a potent antibody response and antigen-specific T-cell responses in immunized piglets. Active and passive immunization can protect piglets against PED following the virus challenge. This study highlights the efficiency of the PEDV-S mRNA vaccine and represents a viable approach for developing an efficient PEDV vaccine.

Immunogenicity and protective efficacy of a trimeric full-length S protein subunit vaccine for porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) has caused serious economic losses to the pig husbandry worldwide, and the effects of existing commercialized vaccines are suboptimal. Therefore, research to develop an efficacious vaccine for prevention and control of PEDV is essential. In this study, we designed and produced trimerized proteins of full-length PEDV spike (S) protein, S1 subunit, and a tandem of multiple epitopes of S protein using an efficient mammalian expression vector system in HEK 293F cells. The immunogenicity of two commercial adjuvants, M401 and M103, was also evaluated in mice. Enzyme-linked immunosorbent assays demonstrated that all immunized mice generated highly systemic PEDV S-specific IgG and IgA antibodies. Mice in S/M103-immunized group generated the highest neutralizing antibody titer with 1:96. Compared with control group, the subunit vaccines elicited multifunctional CD3+CD4+ and CD3+CD8+ T cells, B220+CD19+ B cells, and CD3-CD49b+ natural killer cells in the spleen. PEDV S/M103 vaccine, which had the best immune effect, was selected for further evaluation in piglets. Immunization with S/M103 vaccine induced high levels of S-specific IgG, IgA, and neutralizing antibodies, and increased the proliferation of peripheral blood mononuclear cells and the expression levels of interferon-γ and interleukin-4 in peripheral blood of piglets. Virus challenge test results showed significantly lower diarrheal index scores and fecal viral loads, and less pathological damage to the intestines in S/M103-immunized piglets than in controls, indicating that S/M103 provides good protection against the virulent virus challenge. Our findings suggest that trimeric PEDV S/M103 has potential as a clinical vaccine candidate.

Genetic signatures associated with the virulence of porcine epidemic diarrhea virus AH2012/12

IMPORTANCE

Porcine epidemic diarrhea (PED) caused by PED virus (PEDV) remains a big threat to the swine industry worldwide. Vaccination with live attenuated vaccine is a promising method to prevent and control PED, because it can elicit a more protective immunity than the killed vaccine, subunit vaccine, and so on. In this study, we found two obvious deletions in the genome of a high passage of AH2012/12. We further confirmed the second deletion which contains seven amino acids at the carboxy-terminus of the S2 gene and the start codon of ORF3 can reduce its pathogenicity in vivo. Animal experiments indicated that the recombinant PEDV with deleted carboxy-terminus of S gene showed higher IgG, IgA, neutralization antibodies, and protection effects against virus challenge than the killed vaccine. These data reveal that the engineering of the carboxy-terminus of the S2 gene may be a promising method to develop live attenuated vaccine candidates of PEDV.