Effects of Newcastle Disease/Infectious Bronchitis Vaccine and Feeding Yeast Products on the Innate Immune System in the Proventriculus and Ileum of Broiler Chicks

Abstract

The aim of this study was to determine whether Newcastle disease/infectious bronchitis (ND/IB) vaccination and yeast product diet supplementation modulate the expression of innate immune molecules in the proventriculus and ileum of broiler chicks. One-day-old male broiler chicks were divided into four groups (V-Y- (control), V-Y+, V+Y-, and V+Y+ groups, where V and Y represent vaccination and yeast product supplementation, respectively). Chicks in the V+Y- and V+Y+ groups were immunized with the live ND/IB vaccine, whereas chicks in the V-Y- and V-Y+ groups were not. Chicks in the V-Y+ and V+Y+ groups received feed containing yeast products from day 4, whereas chicks in the V-Y- and V+Y- groups did not. The proventriculus and ileum were collected on day 7 to analyze the expression of seven Toll-like receptors (TLRs) and Dectin-1. In the proventriculus, compared with those of the V-Y- control group, the TLR7 and TLR21 expression levels were higher in the V+Y- group; however, there were no differences in the expression levels of any TLR or Dectin-1 in the ileum. There were also no differences in the expression of avian β-defensins and cathelicidin-1 in the proventriculus and ileum between the control and treatment groups. The expression of granzyme in cytotoxic cells and interleukin (IL)-1B was upregulated by ND/IB vaccination in the proventriculus. Supplementation with yeast products upregulated only granzyme expression in the ileum and downregulated IL-6 expression in the proventriculus in chicks immunized with the ND/IB vaccine. Thus, we concluded that ND/IB vaccination is effective at enhancing the innate immune system in the proventriculus of chicks, at least until day 7 post-hatching, whereas the effects of diet supplementation with yeast products may be limited, at least under the present study conditions.

Keywords: chick gut; innate immunity; vaccination; yeast.

Fig. 1.

Reverse transcription-polymerase chain reaction (RT-PCR) products of the infectious bronchitis virus (IBV) in the proventriculus and ileum of 2-day-old chicks (n = 3, lanes 1–3) inoculated with Newcastle disease and IB vaccine (ND/IB) at one day old. The dense arrow (IBV) at the right side shows the position of the bands of specific PCR products.

Fig. 2.

Effects of Newcastle disease and infectious bronchitis (ND/IB) vaccination and yeast supplementation on the expression of TLRs and Dectin-1 in the proventriculus of chicks. Chicks in the V+Y– and V+Y+ groups were immunized with live ND/IB vaccine, whereas chicks of the V–Y– and V–Y+ groups were not. Chicks of the V–Y+ and V+Y+ groups received yeast product in their diet from day 4, whereas those in the V–Y– and V+Y– groups did not. Gene expression levels were analyzed at day 7. The dots indicate the fold changes in gene expression levels in each chick, and the solid bars represent the median value within each treatment. Asterisks indicate significant differences between the control (V–Y–) and treated (V–Y+, V+Y–, and V+Y+) groups as determined by Dunnett’s test (*P < 0.05).

Fig. 3.

Effects of Newcastle disease and infectious bronchitis (ND/IB) vaccination and yeast supplementation on the expression of TLRs and Dectin-1 in the proventriculus of chicks. See the legend to Figure 2 for the description of the chick groups (V–Y–, V–Y+, V+Y–, and V+Y+). The dots indicate the fold changes in gene expression levels in each chick, and the solid bars represent the mean value within each treatment.

Fig. 4.

Effects of Newcastle disease and infectious bronchitis (ND/IB) vaccination and yeast supplementation on the gene expression of antimicrobial peptides (avian β-defensin, AvBDs; cathelicidin-1, Cath-1) in the proventriculus of chicks. See the legend to Figure 2 for the description of the chick groups (V–Y–, V–Y+, V+Y–, and V+Y+). The dots indicate the fold changes in gene expression levels in each chick, and the solid bars represent the mean value within each treatment.

Fig. 5.

Effects of Newcastle disease and infectious bronchitis (ND/IB) vaccination and yeast supplementation on the gene expression of cytotoxic leukocyte-related molecules and proinflammatory cytokines in the proventriculus. See the legend to Figure 2 for the description of the chick groups (V–Y–, V–Y+, V+Y–, and V+Y+). The dots indicate the fold changes in gene expression levels in each chick, and the solid bars represent the mean value within each treatment. Asterisks indicate significant differences between the control (V–Y–) and treated (V–Y+, V+Y–, and V+Y+) groups as determined by Dunnett’s test (*P < 0.05).

Fig. 6.

Effects of Newcastle disease and infectious bronchitis (ND/IB) vaccination and yeast supplementation on the gene expression of cytotoxic leukocyte-related molecules and proinflammatory cytokines in the ileum. See the legend to Figure 2 for the description of the chick groups (V–Y–, V–Y+, V+Y–, and V+Y+). The dots indicate the fold changes in gene expression levels in each chick, and the solid bars represent the mean value within each treatment. Asterisks indicate significant differences between the control (V–Y–) and treated (V–Y+, V+Y–, and V+Y+) groups as determined by Dunnett’s test (*P < 0.05).