S1 domain of the porcine epidemic diarrhea virus spike protein as a vaccine antigen
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RESEARCH
Open Access
S1 domain of the porcine epidemic diarrhea virus spike protein as a vaccine antigen Niraj Makadiya, Robert Brownlie, Jan van den Hurk, Nathalie Berube, Brenda Allan, Volker Gerdts and Alexander Zakhartchouk*
Abstract Background: Porcine epidemic diarrhea virus (PEDV) is a highly contagious virus infecting pigs of all ages with high morbidity and mortality among newborn piglets. Currently, there is no effective vaccine available to protect the pigs from PEDV. The N-terminal subunit of spike protein (S1) is responsible for virus binding to the cellular receptor and contains a number of neutralizing antibody epitopes. Thus, we expressed and produced recombinant S1 protein to protect newborn piglets by immunization of sows. Methods: Affinity tagged PEDV S1 protein was expressed in a secretory form in yeast, insect and mammalian cells to identify the most suitable production system. Purified recombinant protein was analysed by SDS-PAGE, Western blot and deglycosylation assay. A pregnant sow was intramuscularly immunized three times with adjuvanted recombinant protein prior to farrowing. PEDV-specific immune responses in sera and colostrum of the sow and piglets were assayed by ELISA and virus neutralization assays. Piglets were challenged orally with PEDV, and clinical parameters were monitored for 6 days post-challenge. Results and conclusion: Of three eukaryotic expression systems tested (yeast, insect-cell, and mammalian), expression by HEK-293 T cells gave the highest yield of protein that was N-glycosylated and was the most appropriate candidate for vaccination. Administration of the subunit vaccine in a sow resulted in induction of S1-specific IgG and IgA that were passively transferred to the suckling piglets. Also, high virus neutralization titres were observed in the serum of the vaccinated sow and its piglets. After PEDV challenge, piglets born to the vaccinated sow exhibited less severe signs of disease and significantly lower mortality compared to the piglets of a control sow. However, there were no significant differences in diarrhea, body weight and virus shedding. Thus, vaccination with S1 subunit vaccine failed to provide complete protection to suckling piglets after challenge exposure, and further improvements are needed for the development of a subunit vaccine that fully protects against PEDV infection. Keywords: PEDV, S1, Subunit vaccine, Lactogenic immunity
Background Porcine epidemic diarrhea virus (PEDV) is an enveloped, positive-stranded RNA virus which readily infects pigs, resulting in highly contagious porcine epidemic diarrhea [1]. PEDV belongs to family Coronaviridae, subfamily Coronavirinae and genus Alphacoronavirus [2]. Some * Correspondence: [email protected] Vaccine and Infectious Disease Organization - International Vaccine Center (VIDO-InterVac), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
viruses of the Coronaviridae family cause severe disease in humans such as severe acute respiratory syndrome coronavirus (SARS-CoV) and Mi
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