Commercial broilers are commonly exposed to gaseous ammonia (NH3) originating from degradation of nitrogen-containing excreta in the litter during the grow-out period. Ammonia concentrations in the air are higher in poorly ventilated houses and appear to coincide with the elevated incidence of respiratory disease occurring during the winter months. This study examined the effect of NH3 on the immune response to infectious bronchitis virus (IBV) vaccination and protection against homologous serotype challenge in commercial broiler chickens. One-day-old chicks were administered IBV vaccine and exposed to 30-60 ppm of NH3. At 28 DOA, birds were challenged oculonasally with a pathogenic homologous IBV, and protection was measured by viral detection, clinical signs, ciliostasis, and presence of airsacculitis. IBV-specific serum IgG and lacrimal fluid IgA titers, as well as Harderian gland (HG) immune cell phenotypes, were evaluated. Ammonia exposure was associated with an increased incidence of airsacculitis among non-vaccinated, challenged birds. Vaccinated, NH3-exposed birds were completely protected from IBV challenge. Ammonia had subtle effects on cilia morphology and function but did not affect vaccine or challenge virus replication and clearance, clinical signs, ciliostasis, tracheal histopathology scores, or immune responses. In the HG of vaccinated birds, the percent of leukocytes, MHC I+/MHC IIhi expression, IgM+ expression, and CD8+ expression was increased, while mucosal IgA and serum IgG titers were nominal. Non-vaccinated, IBV-challenged birds exhibited an increased percent of leukocytes, MHC I+/MHC IIhi expression, and IgM+ expression in the HG at 5 dpc, followed by increased mucosal IgA and serum IgG titers and CD8+ expression at 10-14 dpc. In contrast, vaccinated, IBV-challenged birds had a minimal increase in MHC I+/MHC IIhi expression, and serum IgG antibody titers in vaccinated birds increased rapidly. The results indicate that commercial broilers exposed to moderate levels of ambient NH3 are equally protected against IBV challenge if appropriately vaccinated, and the absence of robust immune activation in vaccinated, challenged birds suggests that the challenge virus was efficiently neutralized before establishing infection. In contrast, ambient NH3 exposure was associated with a higher incidence of airsacculitis in non-vaccinated, challenged birds, despite the apparent lack of differences in the immune response between birds in the NH3-exposed and NH3 control groups.

中文翻译：

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氨气似乎不能抑制对传染性支气管炎病毒疫苗的免疫反应，并能防止肉鸡受到同源攻击。

商用肉鸡通常在成长期期间暴露于源自垫料中含氮排泄物降解的气态氨（NH3）。在通风不良的房屋中，空气中的氨浓度较高，似乎与冬季几个月发生的呼吸道疾病的发病率升高相吻合。这项研究检查了NH3对商业性肉鸡对传染性支气管炎病毒（IBV）疫苗免疫反应的保护作用，以及针对同源血清型攻击的保护作用。给一天大的雏鸡接种IBV疫苗，并使其暴露于30-60 ppm的NH3中。在28 DOA时，用致病同源IBV进行眼鼻挑战，并通过病毒检测，临床体征，纤毛停滞和出现气囊炎来测量对鸟类的保护。评估了IBV特异性血清IgG和泪液IgA滴度，以及哈德兰（HG）免疫细胞表型。在未接种疫苗的挑战鸟类中，氨暴露与空气囊炎的发生率增加相关。接种过NH3疫苗的禽类受到了完全保护，免受IBV攻击。氨对纤毛的形态和功能有微妙的影响，但不影响疫苗或挑战病毒的复制和清除，临床体征，纤毛稳定，气管组织病理学评分或免疫反应。在接种禽类的HG中，白细胞，MHC I + / MHC IIhi表达，IgM +表达和CD8 +表达的百分比增加，而粘膜IgA和血清IgG滴度是正常的。未经疫苗接种，IBV感染的禽类的白细胞百分比增加，MHC I + / MHC IIhi表达，5 dpc时HG中IgM +表达，随后10-14 dpc时粘膜IgA和血清IgG滴度和CD8 +表达增加。相反，接种过IBV疫苗的鸡只MHC I + / MHC IIhi的表达增幅很小，并且接种过的鸡的血清IgG抗体滴度迅速增加。结果表明，如果适当接种疫苗，暴露于中等水平的NH3的商品肉鸡同样可以免受IBV攻击，并且在接种疫苗的受攻击鸡中缺乏强大的免疫激活作用，这表明在建立感染之前已有效中和了挑战病毒。相比之下，在未接种疫苗的挑战鸟类中，周围的NH3暴露与空气囊炎的发生率较高相关，