Abstract
Salmonella is a zoonotic pathogen that persists in poultry. Salmonella vaccines that can be delivered in-ovo can be cost-effective and can decrease Salmonella load in poultry. This study evaluates the efficacy of a Salmonella chitosan-nanoparticle (CNP) vaccine, administered in-ovo, in broilers. CNP vaccine was synthesized with Salmonella Enteritidis (SE) outer-membrane-proteins (OMPs) and flagellin proteins. At embryonic-d18, one-hundred-thirty-six eggs were injected with 200μl PBS or 1000μg CNP into the amniotic cavity. At d1-of-age, 132 chicks were allocated in 6 pens/treatment with 11 chicks/pen. At d7, birds were orally challenged with 1×109 CFU/bird SE. At d1, 8h-post-challenge, d14, and d21, serum anti-SE-OMPs IgY were analyzed. At d14 and d21, cloacal swabs and bile anti-SE-OMPs IgA, CD4+/CD8+-T-cell ratios, and ceca SE loads were analyzed. At d21, cecal tonsil IL-1β, IL-10, and iNOS mRNA were analyzed. Body-weight-gain (BWG) and feed-conversion-ratio (FCR) were recorded weekly. Data were analyzed by Student’s t-test at P<0.05. There were no significant differences in BWG or FCR between vaccinated birds compared to control. At d1, CNP-vaccinated birds had 5.62% greater levels (P<0.05) of anti-SE-OMPs IgY, compared to control. At 8h-post-challenge, CNP-vaccinated birds had 6.39% greater levels (P<0.05) of anti-SE-OMPs IgY, compared to control. At 2wk-post-challenge, CNP-vaccinated birds had 7.34% lower levels (P<0.05) of anti-SE-OMPs IgY, compared to control. At 1wk-post-challenge, CNP-vaccinated birds had 15.30% greater levels (P<0.05) of bile anti-SE-OMPs IgA, compared to control. At d14 and d21, CNP-vaccinated birds had 0.62 and 0.85 Log10 CFU/g, decreased SE ceca load (P<0.05), respectively, compared to control. There were no significant differences in CD4+/CD8+-T-cell ratios between vaccinated birds compared to control. There were no significant differences in IL-1β, IL-10, iNOS mRNA between vaccinated birds compared to control. Findings demonstrate that the in-ovo administration of CNP vaccine can induce an antigen-specific immune response against SE and can decrease SE cecal load in broilers.
Highlights
Salmonella is an enteric pathogen in poultry
There were no losses in the hatchability of the birds immunized with the in-ovo Salmonella CNP vaccine
Sixty-four out of the 68 eggs hatched in the group injected with PBS, while 68 out of the 68 eggs hatched in the group injected with the Salmonella CNP vaccine
Summary
Salmonella is an enteric pathogen in poultry. Birds can have up to Log 5 of Salmonella CFU and remain asymptomatic [1]. More than 70% of salmonellosis cases in the United States have been attributed to the consumption of contaminated poultry products or eggs [2]. The Centers for Disease Control and Prevention estimates that Salmonella causes about 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States every year [3]. To prevent Salmonella infections and the economic burden it brings, the poultry industry employs the use of Salmonella vaccines, but currently, commercial vaccines have certain disadvantages. An oral-killed vaccine would circumvent the disadvantages of both live and killed vaccines while mimicking a natural infection and stimulating the mucosal and systemic immune responses [5]. There are currently no commercially available oral-killed Salmonella vaccines for poultry due to the acidic pH of the gastrointestinal tract (GIT) [6]
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