Immunological Response to NDV Vaccine in Chickens

Two hundred non-immunized one-day-old Hy-Line Brown chickens were obtained from Xiangfang farm in Harbin city and equally divided into 4 groups: control group, Dex group, ND group and Dex+ND group. Adequate feed and drinking water were offered ad libitum, and different treatment groups were reared in isolation. At 7-day-old, sterile water containing dexamethasone (Dex) (1.5 mg/L, Shanxi Ruicheng Kelong Veterinary Pharmaceutical Co., Ltd., China) was free to drink in Dex group and Dex +ND group for five consecutive days. At 12-day-old, chickens of ND group and Dex+ND group were administered with NDV LaSota vaccine (Harbin veterinary research institute, China) by eye drop (about 25 µL) according to the instruction, and the chickens from control group and Dex group were treated with NDV vaccine diluent (Harbin veterinary research institute, China). Several tissues including heart, liver, spleen, bursa of Fabricius, thymus, glandular stomach, cecal tonsil and serums of three chickens were collected on 1day post immunization (dpi), 2dpi, 3dpi, 4dpi, 5dpi, 7dpi, 14dpi, 21dpi, 28dpi, and 35dpi. Three randomly-selected chickens from each group were humanely euthanized by an anesthetic overdose of Sumianxin II (0.2 mL/kg body weight; Shengda Animal Medicine Co., Ltd., Dunhua, China) at each time point. All samples were frozen in liquid nitrogen and stored at −80 °C.