Immunogenic differences in primary immune response profiles to electron beam irradiated and formalin-inactivated Salmonella vaccines in pullets

Authors: SANTAMARIA, JOSIE - University Of Arkansas; BECK, CHRISTA - University Of Arkansas; PERERA, RUVINDU - University Of Arkansas; Jesudhasan, Palmy; ERF, GISELA - University Of Arkansas

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/28/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: In general, inactivation of pathogens for vaccine preparation is by chemicals, but the chemicals used in inactivation are know to damage epitopes/antigens, which are important to produce good immune response. Recently, electron Beam (eBeam) technology is being used for vaccine preparation, which does not affect or damage epitopes/antigens. So, in this study, we have compared the effect an eBeam-killed-Salmonella vaccine with a formalin-killed-Salmonella vaccine on local tissue cellular responses as well as plasma SE-specific antibody levels. We have conducted bird study to evaluate the effects of both vaccines using different route and we found that the eBeam-killed-Salmonella vaccine is better than the formalin-killed-Salmonella vaccine.

Technical Abstract: Chemical inactivation of vaccines can damage pathogen epitopes, reducing vaccine efficacy. Electron beam irradiation (eBeam) is a novel approach to inactivate pathogens while keeping their immunogenic properties. A longitudinal study was conducted to assess the effects of a first immunization with an eBeam and a formalin-killed (FK) Salmonella Enteritidis (SE) vaccine on local tissue cellular responses as well as plasma SE-specific antibody levels. Vaccines were administered to two groups of 14-week-old Light-brown Leghorn pullets either by intradermal (i.d.) injection of the pulp of growing feathers (GF) or intramuscularly (i.m.) in breast tissue. Injections of GF-pulp (10 µL/GF-pulp; 200 µL/bird) and breast tissue (500 µL/bird) were done with either eBeam-SE, FK-SE, or endotoxin-free PBS (vehicle); 5 birds/vaccine, 3 birds/vehicle. GF-pulp collected before (0h) and at 6, 24, 48, and 72h post-injection were used for leukocyte population analyses. Blood sampled at 0, 3, 5, 7, 10, 14, 21, and 28d post-GF-pulp or i.m. injection was used to assess relative plasma levels in absorbance units (a.u) of SE-specific IgM, IgG, and IgA by ELISA. Antibody data from each injection route was analyzed separately. The effects of treatments, time, and their interactions on GF-pulp leukocyte profiles were analyzed using 2-way ANOVA, while 2-way RM-ANOVA was used for antibody data. Tukey’s HSD was used for multiple-means comparisons. Statistical significance was at P=0.05. In GF-pulp, infiltration (% GF-pulp cells) of heterophils and macrophages was similar with Ebeam-SE and FK-SE, reaching peak levels (P=0.001) at 6h for both vaccines. Infiltration of CD4, CD8, and 'd T cell subsets peaked at 48h with both vaccines, at this time, these T cell subsets were higher (P<0.05) with eBeam-SE than with FK-SE. B cell recruitment reached the highest (P=0.027) levels at 72h for both vaccines. Overall, SE-specific antibody levels were higher with i.d. than with i.m. vaccination. Relative plasma levels of SE-specific IgM peaked 5d post i.d. injection and were higher with eBeam-SE than with FK-SE (P=0.001); in contrast, independent of vaccine, i.m. injection had highest IgM levels by 10d (P=0.001). IgG peaked on 10d with both injection routes, but only i.d. had a stronger response with eBeam-SE than with FK-SE (P<0.05). IgA levels peaked by 7d (P<0.05) independent of vaccine and route. Based on observations regarding the local (GF-pulp) cellular responses and the SE-specific antibody response profiles, it appears that the eBeam-SE vaccine is better at eliciting T-dependent activities than the FK-SE vaccine.