Forsythoside A is the main active ingredient in the Chinese medicine Forsythia suspensa, which has antiviral, anti-inflammatory, antioxidation, and immunoregulatory effects. It is reported that Forsythoside A can significantly inhibit the replication of the avian infectious bronchitis virus(IBV) in cells, but there is no report in chickens. The present study aimed to investigate the effect of Forsythoside A on IBV-M41, experiments were designed using 120 chickens at 12 days of age. The chickens were randomly divided into eight groups: Forsythoside A high-, medium-, and low-dose prevention groups, Forsythoside A high-, medium-, and low-dose treatment groups, model control group and normal control group. All chickens, except the normal control group, were inoculated with 0.2 ml of IBV-M41 at 15 days of age.The antiviral effects were evaluated by clinical signs, weight, histopathology, T-,B-lymphocyte proliferation, T-lymphocyte subsets and cytokine levels.The results showed that the infection rate in each Forsythoside A prevention group was significantly lower than that in the treatment group and model control group (P < 0.05). The recovery rate in each Forsythoside A treatment group was significantly higher than that in the model control group (P < 0.05), and the recovery rate in high- and medium-dose treatment group was the highest, at up to 86.67%. Lymphocytic transformation ability significantly improved in the prevention and treatment groups. Forsythoside A significantly improved the CD3+, CD4+, and CD8+ T-lymphocyte of infected chickens. The cytokine level was able to maintain high concentrations of IL-2 and IFN-α for a long time and maintain a dynamic IL-4-concentration balance. A number of results showed that Forsythoside A had both preventive and therapeutic effects in IBV-M41-infected chickens, among which the high-dose (80 mg/kg/d) prevention group，the high- (80 mg/kg/d) and medium (40 mg/kg/d) -dose treatment group had significant effects.

连翘苷A是中药连翘中的主要活性成分具有抗病毒，抗炎，抗氧化和免疫调节作用。据报道，连翘苷A可以显着抑制禽传染性支气管炎病毒（IBV）在细胞中的复制，但在鸡中尚无报道。本研究旨在研究连翘苷A对IBV-M41的影响，设计了使用120只12日龄鸡的实验。将鸡随机分为八组：连翘苷A高，中，低剂量预防组，连翘苷A高，中，低剂量治疗组，模型对照组和正常对照组。除正常对照组外，所有鸡在15日龄时均接种0.2 ml IBV-M41。通过临床体征，体重，组织病理学，T-，B-淋巴细胞增殖，P  <0.05）。每个连翘甙A治疗组的恢复率均明显高于模型对照组（P <0.05），高剂量和中剂量治疗组的恢复率最高，达86.67％。预防和治疗组的淋巴细胞转化能力显着提高。连翘苷A显着改善了感染鸡的CD3 +，CD4 +和CD8 + T淋巴细胞。细胞因子水平能够长时间维持高浓度的IL-2和IFN-α，并维持动态的IL-4浓度平衡。许多结果表明，连翘苷A对IBV-M41感染的鸡均具有预防和治疗作用，其中高剂量（80 mg / kg / d）预防组，高剂量（80 mg / kg / d）预防组中剂量（40 mg / kg / d）治疗组有显着疗效。