Electron-Beam–Inactivated Vaccine Against Salmonella Enteritidis Colonization in Molting Hens
2015
Jesudhasan, Palmy R. | McReynolds, Jackson L. | Byrd, Allen J. | He, Haiqi | Genovese, Kenneth J. | Droleskey, Robert | Swaggerty, Christina L. | Kogut, Michael H. | Duke, Sarah | Nisbet, David J. | Praveen, Chandni | Pillai, Suresh D.
Electron-beam (eBeam) irradiation technology has a variety of applications in modern society. The underlying hypothesis was that eBeam-inactivated Salmonella enterica serovar Enteritidis (SE) cells can serve as a vaccine to control SE colonization and shedding in poultry birds. An eBeam dose of 2.5 kGy (kilograys) was used to inactivate a high-titer (10⁸ colony-forming units [CFU]) preparation of SE cells. Microscopic studies revealed that the irradiation did not damage the bacterial cell membranes. The vaccine efficacy was evaluated by administering the eBeam-killed SE cells intramuscularly (1 × 10⁶ CFU/bird) into 50-wk-old single comb white leghorn hens. On day 14 postvaccination, the hens were challenged orally with live SE cells (1 × 10⁹ CFU) and SE colonization of liver, spleen, ceca, and ovaries determined on day 23. Blood samples were collected on days 0, 14, and 23 postvaccination and the sera were analyzed to quantify SE-specific IgG titers. The vaccinated chickens exhibited significantly (P < 0.0001) higher SE-specific IgG antibody responses and reduced SE ceca colonization (1.46 ± 0.39 log₁₀ CFU/g) compared to nonvaccinated birds (5.32 ± 0.32 log₁₀ CFU/g). They also exhibited significantly lower SE colonization of the ovaries (1/30), spleen (3/30), liver (4/30), and ceca (7/30) compared to nonvaccinated birds. These results provide empirical evidence that eBeam-based SE vaccines are immunogenic and are capable of protecting chickens against SE colonization. The advantages of eBeam-based vaccine technology are that it is nonthermal, avoids the use of formalin, and can be used to generate inactivated vaccines rapidly to address strain-specific infections in farms or flocks.
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