Evaluation of protective immune response against fowl typhoid in chickens vaccinated with the attenuated strain Salmonella Gallinarum Δ cob SΔ cbi A

Abstract

Salmonella enterica serovar Gallinarum biovar Gallinarum (SG) causes fowl typhoid in chickens, a septicemic infection which results in high mortality rates. This disease causes high economic impact to the poultry industry worldwide because of the mortality or elimination of positive flocks to control bacterial dissemination. Live vaccines are used in the fields, however the characterization of immune mechanisms important for protection are being studied to improve the efficacy of vaccination schemes. In this study, we evaluated the immune response in brown layer-hens, vaccinated or not, during the most critical period of infection. Cellular and humoral immunity were extensively evaluated until 7 days post-infection (DPI), by flow cytometry and ELISA, respectively. Furthermore, we evaluated the expression of important pro-inflammatory cytokines after infection of bone marrow derived macrophages (BMDMs) with the live attenuated SG vaccine and with the wild SG strain. The results showed an increasing production of IgG and IgM during the first week post-infection, in vaccinated layer-hens, which was absent in unvaccinated birds. The population of CD8(+)CD44(+) and CD4(+)CD44(+) T cells in spleen and cecal tonsils constantly decreased in unvaccinated birds in comparison with vaccinated layers. The expression of IFN-γ and TNF-α in BMDMs was induced by both SG strains (attenuated and wild) at similar levels (p>0.05). Vaccination with live SG vaccine reduced systemic infection by challenge strain of SG and prevented the mortality rate of 85% that occurred in unvaccinated layer-hens during 30 dpi. Furthermore, the immunization enhanced the proliferation of effector CD4(+) and CD8(+) T cells after challenge.

wecB Gene of Salmonella Gallinarum Plays a Critical Role in Systemic Infection of Fowl Typhoid

“…To promote the effective reproduction and growth of chickens and their global trade, attempts have been made to vaccinate chickens with live-attenuated strains of S . Gallinarum to control fowl typhoid (Kwon and Cho, 2011 ; Penha Filho et al, 2016 ; Wigley, 2017 ). However, live-attenuated vaccines retain some virulence and the protective effects of the vaccines are not yet completely satisfactory (Penha Filho et al, 2010 ; Ji et al, 2021 ).…”

The Simultaneous Administration of a Probiotic or Prebiotic with Live Salmonella Vaccine Improves Growth Performance and Reduces Fecal Shedding of the Bacterium in Salmonella-Challenged Broilers

“…Inactivated and/or live attenuated vaccines are used to prevent poultry infection with Salmonella organisms through promoting acquired immunity [6]. Salmonella vaccination has been proven to have some advantages that include reduction of transmission rate, either horizontal or vertical, of Salmonella among broiler breeder and/or broiler chicks [7], lowering the prevalence rate of contaminated table eggs with this pathogen [8] and improving survival rate [9]. Nevertheless, Berghaus et al [10] reported that this measure cannot decrease the environmental contamination of a breeder farm with Salmonella.…”

Evaluation of the Protective Immune Response Induced by an rfbG- Deficient Salmonella enterica Serovar Enteritidis Strain as a Live Attenuated DIVA (Differentiation of Infected and Vaccinated Animals) Vaccine in Chickens

“…Enteritidis vaccine strain, JOL919, induced significant systemic immunoglobulin responses in chickens after inoculation ( 22 ). Another study reported that IgG levels were significantly higher in chickens vaccinated with the cobS and cbiA mutant S. Gallinarum strains than in the control group ( 23 ). Similarly, in this study, all chickens immunized with 5 × 10 6 and 5 × 10 7 CFU of Z11Δ rfbG had significantly higher levels of S .…”