Comparison of serological response between oil emulsion and aluminum hydroxide emulsion inactivated 3-way Salmonella vaccines

Abstract

Bacterins have been used in long-lived birds to reduce vertical transmission of Salmonella in eggs, DOC (day old chicks), and to provide high MDAs (maternal delivered antibodies). In addition to the composition of antigens present in the vaccine, the adjuvant can directly influence the immune response of birds, inducing different levels of circulating antibodies. The goal of this study was to evaluate the dynamics of the serological response induced by 2 bacterins against Salmonella containing different adjuvant technologies. A total of 600 1-day-old Lohmman Brown layer chicks were housed in a completely randomized design, divided into 2 treatments: T1 - bacterin in an oil emulsion containing strains of S. enteritidis, S. typhimurium and S. infantis (0.3 ml/bird - Salmin Plus®); T2 - inactivated vaccine containing strains of S. enteritidis, S. typhimurium and S. infantis (0.5 ml/bird) in aluminum hydroxide-based adjuvant. All groups were vaccinated at 10 and 14 weeks of age, by intramuscular injection in the pectoral muscle. Management and nutrition were according to the genetic line recommendations. Twenty blood samples of each treatment were collected for Salmonella enteritidis (O:9) ELISA (BioChek B.V. Fokkerstraat 14, 2811 ER Reeuwijk, Netherlands) at the following ages: 10; 14; 17; 27; 33; 40; 48; 56 and 65 weeks of age. Antibody titers were submitted to homogeneity and normality and analyzed for variance using the Jamovi® software, with means compared by Tukey’s test (5 % significance). The antibody titers of the two groups were statistically similar at 10 weeks (P=0.932). At the ages of 14; 17; 27; 40; 48; 56 and 65 weeks, birds vaccinated with the oil emulsion-based vaccine demonstrated higher circulating antibody titers than T2 birds (P<0.05). At 33 weeks, antibody titers did not differ between groups (P=0.296). We can conclude from this study that even though they contain a similar composition of antigens, the immune response of birds can also be modulated by the adjuvant used in the vaccine. In this case, birds vaccinated with an oil emulsion vaccine had higher levels of serum antibodies than birds vaccinated with the aluminum hydroxide adjuvanted vaccine. It can be assumed that higher titers in the breeders will result in lower vertical transmission and higher MDA titers in the DOC.