miR-17-5p-PD-L1 pathway is a potential mechanism by which stress inhibits immune response to NDV vaccine in chickens.

In poultry production, stress-induced immunosuppression (SIIS) often leads to poor immune response to vaccines, causing immunized chickens to still develop diseases. If the molecular mechanisms by which SIIS affects immune response can be comprehensively elucidated, it can provide new insights and strategies for improving and addressing this issue. However, the detailed molecular regulatory mechanisms remain unclear. In this study, dexamethasone-induced immunosuppression (DIIS) was used to simulate SIIS in chickens, and the Newcastle disease virus (NDV) attenuated vaccine was used for vaccination. The study aimed to explore the expression characteristics and functions of immune checkpoint gene PD-L1 (programmed cell death ligand 1), the regulatory mechanism of PD-L1 gene mediated by miR-17-5p, and the potential application of circulating miR-17-5p in the process of SIIS inhibiting the immune response to the NDV vaccine. Quantitative real-time PCR (qRT-PCR) results showed that PD-L1 gene was differentially expressed in nine candidate tissues (P < 0.05), and actively involved in the SIIS mediated immunosuppression of NDV vaccine response. There were significant regulatory relationships between miR-17-5p and PD-L1 gene in multiple tissues, suggesting that the miR-17-5p-PD-L1 pathway was a key regulatory mechanism of SIIS inhibiting NDV immune response. Furthermore, expression analysis demonstrated that SIIS significantly altered circulating miR-17-5p levels in serum at several time points, such as 2 days post immunization (dpi), 4 dpi and 5 dpi, indicating the potential of serum circulating miR-17-5p as a molecular marker. This study provides valuable references for detecting, preventing, and treating the effects of stress affecting immune response.