A Strong Antigen-Specific T-Cell Response Is Associated with Age and Genetically Dependent Resistance to Avian Enteric Salmonellosis

Abstract

Chicken genetics and age affect resistance to enteric infection with Salmonella enterica serovar Typhimurium and were used to identify the immune responses that may contribute to rapid clearance. When birds were infected at 40 days of age, line 6 1 chickens cleared the infection more effectively than line N chickens, whereas when birds were infected at 10 days of age, both chicken lines were highly susceptible to infection. Antibody levels, T-cell responsiveness, and cytokine mRNA levels were all elevated during infection. A negative correlation between resistance and antigen-specific antibody production was observed in older chickens. However, this finding was not replicated for age-related resistance; we found that older chickens exhibited a stronger and more rapid antibody response than younger chickens. The levels of interleukin-1␤ (IL-1␤) and gamma interferon (IFN-␥) mRNA were similar in the spleens and cecal tonsils of both line 6 1 and line N chickens, except for higher levels of IL-1␤ in the spleens of line 6 1 chickens at 6 days postinfection. Differences in the levels of IFN-␥ and IL-1␤ 1␤ mRNA between the lines were more apparent in younger chickens, but while the increases were greater than those observed in the older chickens, the clearance of enteric S. enterica serovar Typhimurium was much slower. The level of antigen-specific proliferation of splenocytes was associated with increased resistance in both experimental systems, and the strongest responses were observed in older and genetically resistant chickens. The data presented here implicate T-cell responses in the clearance of S. enterica serovar Typhimurium from the intestine of infected chickens.

Expression of Toll-Like Receptor 4 and Downstream Effectors in Selected Cecal Cell Subpopulations of Chicks Resistant or Susceptible to Salmonella Carrier State

“…Finally, there was no upregulation of TLR4 or of some of the downstream effectors of TLR4, such as IL-1␤, IL-8, and LITAF (in the resistant line only). This is in clear contrast with what has been reported for the acute phase, during which a massive recruitment of heterophils and macrophages has been observed (43) and the levels of expression of IL-8 and IL-1␤ have been shown to be increased in vitro and in vivo (5,11,17,36). Overall, this suggests that mechanisms responsible for resistance to infection and those involved in resistance to the carrier state are different.…”

Immunological and gene expression responses to aSalmonellainfection in the chicken intestine

“…It was also shown that after infection with Salmonella the number of CD8 + TCRγδ + T-cells in the chicken intestine increased [6]. CD4 + or CD8 + T-cell responses are not required for the early host response [14], but CD4 + T-cell responses, particularly Th1 responses, play an important role in the clearance of Salmonella from the gastrointestinal tract [5,10,27].…”

Utilization of a novel autologous killed tri-vaccine (serogroups B [Typhimurium], C [Mbandaka] and E [Orion]) forSalmonellacontrol in commercial poultry breeders

“…In the present study, 43% of hens were seropositive (titre785) after 20 weeks, suggesting flock immunity. The Guildhay method advocates an initial serum dilution of 1:500, whereas similar work with killed Typhimurium vaccines used initial serum dilutions of 1:250, 1:400 and 1:400, respectively (Bailey et al, 2007a;Beal et al, 2005;Withanage et al, 2005). The higher initial dilution may have reduced the number of positive ELISA results in this trial.…”