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ARS Home » Southeast Area » Fayetteville, Arkansas » Poultry Production and Product Safety Research » Research » Publications at this Location » Publication #421299
Research Project: Multi-hurdle Approaches for Controlling Foodborne Pathogens in Poultry

Location: Poultry Production and Product Safety Research

Title: Secondary immune response profiles to electron beam- or formalin-inactivated Salmonella vaccines in egg-type pullets: immunogenic differences

Author
item SANTAMARIA, JOSSIE - University Of Arkansas
item BECK, CHRYSTA - University Of Arkansas
item PERERA, RUVINDU - University Of Arkansas
item Jesudhasan, Palmy
item ERF, GISELA - University Of Arkansas

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/27/2024
Publication Date: 1/20/2025
Citation: Santamaria, J.M., Beck, C.N., Perera, R., Jesudhasan, P., Erf, G.F. 2025. Secondary immune response profiles to electron beam- or formalin-inactivated Salmonella vaccines in egg-type pullets: immunogenic differences. Abstract. International Poultry Scientific Forum, January 27-28, 2025.

Interpretive Summary: Salmonella is one of the top 10 human foodborne pathogens cause more than one million foodborne illnesses in the United States. Poultry is one of the major reservoirs for Salmonella. Controlling Salmonella in chickens would reduce foodborne outbreaks. Current vaccines against Salmonella are not effective, so in this study, we have tested the effect of electron beam (eBeam)-inactivated Salmonella Enteritidis (SE) vaccine and compared the effect with formalin-killed (FK) SE by vaccinating chickens through different route: intradermal (i.d.), and growing feather (GF) pulp. We have evaluated the vaccine efficacy using flow cytometry and ELISA. We found that in both vaccines, CD8+ T cell levels peaked (P<0.05) at 2d, while total lymphocytes and B cells peaked at 3d. Recruitment of B cells and all T cell subsets were higher (P<0.05) with FK-SE than with eBeam-SE and PBS. SE-specific IgM in plasma peaked (P=0.001) at 5d, while SE-IgG (P=0.001) and SE-IgA (P=0.001) peaked by 7d p.i. with both vaccines. While both the eBeam-SE and FK-SE vaccines generated a similar SE-specific humoral response, the rapid and greater heterophil recruitment to GF-pulps in response to the secondary i.d. eBeam-SE vaccination suggests a form of trained innate immunity that may be beneficial in elimination of Salmonella infection. Further studies with Salmonella challenge after vaccination is necessary.

Technical Abstract: Previously, an intradermal (i.d.) injection of an electron beam (eBeam)-inactivated Salmonella Enteritidis (SE) vaccine initiated a greater leukocyte response in the growing feather (GF) pulp (vaccination site) and a more robust plasma SE-specific antibody response than with i.d. vaccination with formalin-killed (FK) SE. This study assessed the effects of a second i.d. vaccination with eBeam-SE or FK-SE vaccines (10^8 CFU/mL) on local leukocyte responses and SE-specific antibodies levels in plasma. Further, 14-wk-old layer pullets were vaccinated with either eBeam-SE, FK-SE (5 birds/vaccine), or PBS (3 birds) in the breast muscle (500 µL/bird), and at 18-wks by i.d. GF-pulp injection (10 µL/GF; 200 µL/bird) of the respective vaccines. GFs were collected before (0d) and at 6h 1-, 2-, 3-, 5-, and 7-d post-pulp-injection (p.i.) for leukocyte population analyses, and blood was sampled at 0, 3, 5, 7, 10, 14, 21, and 28d p.i. to measure relative plasma levels of SE-specific IgM, IgG, and IgA by ELISA. Two-way ANOVA was used for GFs, and repeated measures of 2-way ANOVA for blood to assess the effects of treatment, time, and their interactions. Tukey's HSD test was applied as needed, and significance was set at P=0.05. In GF, infiltration of heterophils peaked (P=0.001) at 6h and declined to near 0d levels (% pulp cells) by 2d; whereby at 6h, levels were higher (P=0.001) with eBeam-SE than with FK-SE and PBS. Regardless of treatment, macrophage levels increased (P=0.001) at 6h, remained elevated at 1d, and declined to near 0d levels by 2d p.i. At 1d, macrophage levels were higher with eBeam-SE than with FK-SE and PBS. For both vaccines, CD8+ T cell levels peaked (P<0.05) at 2d, while total lymphocytes and B cells peaked at 3d. Recruitment of B cells and all T cell subsets were higher (P<0.05) with FK-SE than with eBeam-SE and PBS. SE-specific IgM in plasma peaked (P=0.001) at 5d, while SE-IgG (P=0.001) and SE-IgA (P=0.001) peaked by 7d p.i. with both vaccines. While both the eBeam-SE and FK-SE vaccines generated a similar SE-specific humoral response, the rapid and greater heterophil recruitment to GF-pulps in response to the secondary i.d. eBeam-SE vaccination suggests a form of trained innate immunity that may be beneficial in elimination of Salmonella infection.