S1 domain of the porcine epidemic diarrhea virus spike protein as a vaccine antigen.

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.

Innate immune cocktail partially protects broilers against cellulitis and septicemia.

Antimicrobial/host defense peptides (A/HDP) are natural compounds that are found in leucocyte cells and on the skin and bodily fluids of birds, reptiles, and mammals. Not only do they possess antibacterial, antiviral, and antiparasitic characteristics but they also stimulate the host immune system to combat infectious diseases and may play a role in the promotion of wound repair. Gamma-amino butyric acid (GABA) is an amino acid-based inhibitory neurotransmitter in the brain that has also been shown to promote wound healing on skin. The objective of this study was to establish a therapeutic cocktail that protects birds against Escherichia coli-related disease and lesions in broilers. We injected a cocktail of six A/HDPs with or without GABA into 3-wk-old broilers by a subcutaneous or intramuscular route followed 24 hr later by challenge with a field isolate of serogroup O2 E. coli. Birds were examined for 5-6 days post-E. coli challenge and clinical, pathologic, and bacteriologic assessments were conducted. Birds that were subcutaneously injected with an A/HDP plus GABA cocktail had significantly higher survival rates and lower levels of bacteremia (P < 0.05), but a similar percentage of the surviving birds had large cellulitis lesions compared to the surviving phosphate-buffered saline-injected control birds. When this cocktail was administered intramuscularly, there was a trend towards protection against E. coli-related death, although the results were not statistically significant and there was no reduction in bacteremia. A significant number of birds had a reduced bacterial load on cellulitis lesions but no reduction in lesion size, which suggests that when the cocktail was administered intramuscularly it failed to protect against cellulitis. These results suggest that the route of administration of the cocktail influences disease outcome. Gene expression analysis was performed to investigate whether the cocktail induced immunomodulatory functions in avian cells that complemented their antimicrobial and anti-endotoxic effects. A/HDP plus GABA mediated temporal induction of pro-inflammatory cytokines but no induction of any of the chemokines under investigation. This cocktail shows potential to protect against E. coli-related death, which is a major economic burden to the poultry industry.