ABSTRACT
There is a critical need for an oral-killed Salmonella vaccine for broilers. Chitosan nanoparticle (CNP) vaccines can be used to deliver Salmonella antigens orally. We investigated the efficacy of a killed Salmonella CNP vaccine on broilers. CNP vaccine was synthesized using Salmonella enterica serovar Enteritidis (S. Enteritidis) outer membrane and flagella proteins. CNP was stable at acidic conditions by releasing 14% of proteins at pH 5.5. At 17 h post-incubation, the cumulative protein release for CNP was 75% at pH 7.4. Two hundred microliters of PBS with chicken red blood cells incubated with 20 µg/ml CNP released 0% hemoglobin. Three hundred chicks were allocated into 1) Control, 2) Challenge, 3) Vaccine + Challenge. At d1 of age, chicks were spray-vaccinated with PBS or 40 mg CNP. At d7 of age, chicks were orally-vaccinated with PBS or 20 µg CNP/bird. At d14 of age, birds were orally-challenged with PBS or 1 × 107 CFU/bird of S. Enteritidis. The CNP-vaccinated birds had higher antigen-specific IgY/IgA and lymphocyte-proliferation against flagellin (p < 0.05). At 14 days post-infection, CNP-vaccinated birds reversed the loss in gut permeability by 13% (p < 0.05). At 21 days post-infection, the CNP-vaccinated birds decreased S. Enteritidis in the ceca and spleen by 2 Log10 CFU/g, and in the small intestine by 0.6 Log10 CFU/g (p < 0.05). We conclude that the CNP vaccine is a viable alternative to conventional Salmonella poultry vaccines.
ABSTRACT
Salmonella control strategies include vaccines that help reduce the spread of Salmonella in poultry flocks. In this study we evaluated the efficacy of administering a live Salmonella vaccine followed by a killed Salmonella chitosan nanoparticle (CNP) vaccine booster on the cellular and humoral immunity of broilers. The CNP vaccine was synthesized with Salmonella Enteritidis (S. Enteritidis) outer-membrane-proteins (OMPs) and flagellin-proteins. At d1-of-age, one-hundred-sixty-eight chicks were allocated into treatments: 1) No vaccine, 2) Live vaccine (Poulvac®ST), 3) CNP vaccine, 4) Live+CNP vaccine. At d1-of-age, birds were orally vaccinated with PBS, Live vaccine, or CNP. At d7-of-age, the No vaccine, Live vaccine and CNP vaccine groups were boosted with PBS and the Live+CNP vaccine group was boosted with CNP. At d14-of-age, birds were challenged with 1×109 CFU/bird S. Enteritidis. There were no significant differences in body-weight-gain (BWG) or feed-conversion-ratio (FCR). At 8h-post-challenge, CNP and Live+CNP-vaccinated birds had 17% and 24% greater levels (P<0.05) of anti-Salmonella OMPs IgA in bile, respectively, compared to control. At d28-of-age, CNP, Live, and Live+CNP-vaccinated birds had 33%, 18%, and 24% greater levels (P<0.05) of anti-Salmonella OMPs IgA in bile, respectively, compared to control. At d14-of-age, Live+CNP-vaccinated birds had 46% greater levels (P<0.05) of anti-Salmonella OMPs IgY in serum, compared to control. At d21-of-age, splenocytes from CNP and Live-vaccinated birds had increased (P<0.05) T-lymphocyte proliferation at 0.02 mg/mL OMPs stimulation compared to the control. At d28-of-age, CNP and Live+CNP-vaccinated birds had 0.9 Log10 CFU/g and 1 Log10 CFU/g decreased S. Enteritidis cecal loads (P<0.05), respectively, compared to control. The CNP vaccine does not have adverse effects on bird's BWG and FCR or IL-1ß, IL-10, IFN-γ, or iNOS mRNA expression levels. It can be concluded that the CNP vaccine, as a first dose or as a booster vaccination, is an alternative vaccine candidate against S. Enteritidis in broilers.
