Serum cytokine profile of neonatal broiler chickens infected with Salmonella Typhimurium

Abstract

The avian immune system responds to Salmonella infection by expressing cytokines and chemokines. We hypothesized that the immune status of Salmonella Typhimurium (ST) challenged neonatal broilers would differ from the uninfected treatment. The objective of this experiment was to evaluate 12 cytokines. Day of hatch male chicks were randomly allocated into a control or ST challenged group. At day three of age, sterile diluent or 5.0 × 10⁸ CFU of ST was given orally to each chick. Blood was obtained 24 h post challenge and serum separated for later analysis (n = 30 chicks/treatment). Significant (p ≤ 0.05) increases in pro-inflammatory cytokines-interleukin-6 (IL-6), IL-16, and IL-21; anti-inflammatory cytokines- IL-10; chemokines-regulated on activation, normal T cell expressed and secreted (RANTES), macrophage inflammatory protein-1β (MIP-1β), and MIP-3α; colony stimulating factors-macrophage colony-stimulating factor (M-CSF); and growth factors-vascular endothelial growth factor (VEGF) were observed in the serum of the challenged chicks when compared to the control. No significant differences were observed in IL-2, interferon gamma (IFNγ), and IFNα. These data indicate the detection of mucosal immune responses in broiler chickens following ST infection. The heightened levels of pro-inflammatory cytokines, chemokines, and colony stimulating factors align with known inflammatory mechanisms, like the influx of immune cells. However, the elevation of IL-10 was unexpected, due to its immunoregulatory properties. Notably, the rise in VEGF levels is compelling, as it suggests the possibility of tissue repair and angiogenesis in ST infected birds.

Keywords: Salmonella Typhimurium; immune response; immunoassay; poultry; serum cytokine.

FIGURE 1

Workflow of experimental design. The figure was created in BioRender.com by Allison Milby-Blackledge.

FIGURE 2

Cytokine and chemokine analysis of the serum of control and Salmonella Typhimurium (ST) challenged chicks. Day-old chicks were divided into control and ST treatment groups. Birds in the treatment group were challenged with 5.0 × 10⁸ CFU of ST. The levels of cytokines, chemokines, growth factors, and colony-stimulating factors were analyzed. The target sample size (n) was 30 samples. However, n differs between control and ST treatments of each analyte due to variation from low bead counts, concentrations that were below the readable limit, as well as outliers causing the actual n to range from 23 to 27 samples for the control group and 26 to 29 samples for the ST treatment group. An asterisk (*) indicates concentrations that are considered significant differences at p ≤ 0.05 compared to the control group.