Effects of avian infectious bronchitis/Newcastle disease and Marek's disease vaccinations on the expression of Toll-like receptors and avian β-defensins in the kidneys of broiler chicks

Shimizu, Masahiro; Nii, Takahiro; Isobe, Naoki; Yoshimura, Yukinori

The aim of this study was to determine the effect of vaccinations for avian infectious bronchitis/Newcastle disease (IB/ND) and Marek's disease (MD) on the expression of Toll-like receptors (TLRs) that recognize viral RNA and microbial DNA, and avian β-defensins (AvBDs) in chick kidneys. Day-old chicks were vaccinated with MD or IB/ND vaccines, or received no treatment (control group). The gene expression of TLRs and AvBDs in the kidneys of 3-day-old chicks and 10-day-old chicks was examined using real-time PCR. The localization of AvBD2 and AvBD4 was examined by immunohistochemistry at day three only. At 3 days of age the expression of TLR7 and TLR21 was significantly higher in the IB/ND group (but not in the MD group) when compared to the control group. Conversely, at 10 days of age there was no significant difference in the expression of the three TLRs between groups. In the 3-day-old chicks the expression levels of AvBD4, 5, 6, and 7 were higher in the MD group when compared to the control group. Furthermore, at this age, the expression levels of other AvBDs were not significantly different between the control and vaccination (MD and IB/ND) groups. At 10 days of age, no AvBD expression was affected by MD and IB/ND vaccinations. Immunohistochemistry results localized AvBD2 in the leukocytes in the interstitial tissue and AvBD4 in the surface of microvillus epithelial cells of renal tubules, and in the epithelial cells of the collecting ducts and ureter. The localization of AvBD2 and AvBD4 was identified in all chicks. We suggest that the expression of innate immune molecules (including TLRs and AvBDs) in kidneys could be modulated by MD and IB/ND vaccination when performed at the day-old stage. Although the effects of both vaccinations may subside within 10 days, the enhanced expression of those innate immune molecules may support the innate immuno-defense function in the kidneys of young chicks.