Immune response following vaccination against Salmonella Enteritidis using 2 commercial bacterins in laying hens

Abstract

The humoral and cell-mediated immune (CMI) response to 2 commercial killed Salmonella Enteritidis (SE) vaccines (Layermune and MBL SE4C) was evaluated in laying hens. Layers were distributed in 2 experimental groups. The first received a single immunization at 16 wk of age, while the second experimental group was immunized at 12 wk of age and again at 18 wk of age. Serum immunoglobulin (Ig)G antibodies were measured using a commercial SE ELISA kit and showed persistent levels from 3 to 32 and 34 wk post-vaccination. The vaccination protocol using 2 immunizations showed a higher seroconversion level than the single vaccination. However, our results for bacterial intracellular survival indicated that IgG titers were not linked with bacterial killing. Local IgA production was measured in the intestines and oviducts with an in-house SE whole cell antigen ELISA. Only the MBL SE4C vaccine elicited IgA antibody production when tested on intestine and oviduct mucosal secretions, 3-weeks post-vaccination in both immunization protocol groups. To evaluate the CMI response, the splenic T-cells and B-cells populations were analyzed using flow cytometry. The CD3/B-cell ratio decreased 3 wk after the second immunization in the twice vaccinated Layermune group due to an increase in B-cells.

Figure 1

A — Detection of antibodies (IgG) in sera of laying hens vaccinated once analyzed using Salmonella Enteritidis (SE) antibody test kit. B — Detection of antibodies (IgG) in sera of laying hens vaccinated twice. Antibodies (IgG) analyzed using SE antibody test kit. Vertical bars indicated the standard errors. Significant differences in mean titers were determined by using the Bonferroni test at P < 0.01. The mean titers of MBL SE4C vaccinated group (▪) and Layermune vaccinated group (▴) were compared with those of control group (♦). The titer of SE-antibodies is inversely proportional to the optical density (OD) values at 650 nm. Data represent mean ± standard deviation (n = 25 hens/group/sampling period). ^a,b,c P < 0.0001.

Figure 2

A — Immunoglobulin (Ig)A levels in the intestinal mucus of laying hens vaccinated once with subcutaneous Salmonella Enteritidis (SE) vaccine. B — IgA levels in the intestinal mucus of laying hens subcutaneous SE vaccinated twice. Salmonella Enteritidis whole cell-specific antibodies (IgA) were detected using ELISA. Data represent mean ± standard deviation (n = 3 hens/group/sampling period). OD — optical density; PV — post-vaccination; PPV — post primary vaccination; PSV — post second vaccination. ^a P < 0.01.

Figure 3

A — Immunoglobulin (Ig)A levels in the oviductal mucus of laying hens vaccinated once with subcutaneous Salmonella Enteritidis (SE) vaccine. B — IgA levels in the oviductal mucus of laying hens vaccinated twice with subcutaneous SE vaccine. Salmonella Enteritidis whole cell-specific antibodies (IgA) were detected using ELISA. Data represent mean ± standard deviation (n = 3 hens/group/sampling period). OD — optical density; PV — post-vaccination; PPV — post primary vaccination; PSV — post second vaccination. ^a P < 0.01.

Figure 4

The CD3/IgM cells ratio after immunization with single vaccination (A) and 2 immunizations (B). Data represent mean ± standard deviation (n = 3 hens/group/sampling period). PV — post-vaccination; PPV — post primary vaccination; PSV — post second vaccination. ^a,b P < 0.05.