Efficacy of heat-labile enterotoxin B subunit-adjuvanted parenteral porcine epidemic diarrhea virus trimeric spike subunit vaccine in piglets

Abstract

Devastating outbreaks of porcine epidemic diarrhea (PED) started in China in late 2010 and rapidly spread to North America and Asia causing severe diarrhea and high mortality in neonatal piglets, indicating that a new generation of vaccine against porcine epidemic diarrhea virus (PEDV) is urgently needed. In the present study, to mimic the native spike (S) glycoprotein, a stable cell line producing the trimeric ectodomain of S glycoprotein of the PEDV Pintung-52 (PEDV-PT) strain was successfully established by incorporating T4 bacteriophage foldon sequence of fibritin trimerization domains at the C-terminal end and replacing the signal peptide of S protein with the tissue plasminogen activator signal peptide sequence at the N terminal end. The trimeric structure, bio-reactivity to PEDV-specific antibodies, and the N-glycosylation level of the recombinant S protein were characterized. To induce systemic and mucosal immunity, conventional 5-week-old piglets were immunized with the trimeric S glycoprotein combined with the B subunit of Escherichia coli heat-labile enterotoxin (LTB) by the intramuscular (IM) route. As compared with the control group, all piglets in the S protein-LTB immunized (IM PEDV S-LTB) group generated systemic PEDV S-specific IgG and neutralizing antibody in blood but a low level of fecal PEDV-specific IgA and limited protection against challenge of PEDV-PT strain. Our results suggest that the recombinant PEDV trimeric S glycoprotein could be a potential subunit vaccine candidate against PEDV, but IM immunization with LTB as the adjuvant provided insufficient protection. The development of a vaccine regimen for inducing mucosal immunity is an important task for generating a successful subunit vaccine against PEDVs.

Intramuscular Immunization with Chemokine-Adjuvanted Inactive Porcine Epidemic Diarrhea Virus Induces Substantial Protection in Pigs

“…The stimulation of mucosal immunity by trafficking antigen secreting cells (ASCs) to mucosa-related locations has been considered difficult via IM administration of vaccinations. However, IM administration is the most popular and convenient route for vaccinations in pig herds [6,[15][16][17]36,37]. In the present study, we have demonstrated that IM co-administration of iPEDV with CC chemokines as adjuvants could induce superior systemic antigen-specific IgG, mucosal antigen-specific IgA, and recruitment of CCR9+ and/or CCR10+ inflammatory cells at the injection site of the experimental pigs as compared to control piglets.…”

“…Many attempts have been made to develop a safe and protective vaccine for controlling PED [4][5][6][7][8][9][10]. However, similar to studies on most enterotropic and mucosal transmissible viral diseases [11][12][13][14], using intramuscular (IM) administration of inactive or subunit vaccines combined with commercial adjuvants, such as multiple emulsions of water/oil/water or a B subunit of Escherichia coli heat-labile enterotoxin (LTB) induced production of systemic IgG and neutralizing antibodies but failed to elicit a mucosal IgA response and efficient protection [6,7,[15][16][17]. Furthermore, poor efficacies of currently commercialized vaccines have been reported [18][19][20].…”

The Characterization of Immunoprotection Induced by a cDNA Clone Derived from the Attenuated Taiwan Porcine Epidemic Diarrhea Virus Pintung 52 Strain

“…To detect PEDV specific plasma IgG and fecal and salivary IgA, an in-house, PEDV S protein based indirect enzyme-linked immunosorbent assay (ELISA) was conducted as described in the previous study [ 24 ]. In brief, 96-well, flat-bottom microtiter plates (Nunc, Roskilde, Denmark) were coated with 2 μg/mL purified recombinant PEDVPT S protein (200 ng/well) and incubated overnight at 4 °C.…”

Oral administration of porcine epidemic diarrhea virus spike protein expressing in silkworm pupae failed to elicit immune responses in pigs

“…The PEDV S-specific ELISA for detecting the systemic IgG and oral mucosal IgA of pigs was established and conducted as previous described with some modifications (Chang et al 2018b). Briefly, the purified S protein of PEDV expressed by HEK 293 cells were diluted and coated on the Nunc maxi-soap plates (Thermo Fisher Scientific, Waltham, MA, USA) in the concentration of 2 ng/μL.…”