Ali Ahmed, Hassan Mohamed S H, Najimudeen Shahnas M, Farooq Muhammad, Shany Salama, El-Safty Mounir Mohamed, Shalaby Adel A, Abdul-Careem Mohamed Faizal
Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
Department of Pathology, Faculty of Veterinary Medicine, Beni-Suef University, Beni Suef 62511, Egypt.
Vaccines (Basel). 2023 Feb 2;11(2):338. doi: 10.3390/vaccines11020338.
Vaccination remains the leading control method against infectious bronchitis (IB) in poultry despite the frequently observed IB outbreaks in vaccinated flocks. Here, two vaccination regimes were evaluated against challenge with the Massachusetts (Mass) infectious bronchitis virus (IBV) strain that was linked to egg production defects in Western Canada. One vaccination strategy included live attenuated IB vaccines only, and the other used both inactivated and live attenuated IB vaccines. The two immunization programs involved priming with a monovalent live attenuated IB vaccine (Mass serotype) at day-old, followed by intervals of bivalent live attenuated IB vaccines containing the Mass and Connecticut (Conn) serotypes given to the pullets at 2-, 5-, 9-, and 14-week-old. Inactivated IB vaccine (Mass serotype) was administrated to only one group of the vaccinated birds at 14-week-old. At the peak of lay, the hens were challenged with the Mass IBV isolate (15AB-01) via the oculo-nasal route. The efficacy of the vaccines was assessed following the challenge by observing clinical signs, egg production, egg quality parameters, seroconversion, and systemic T-cell subsets (CD4+ and CD8+ cells). Moreover, the viral genome loads in the oropharyngeal (OP) and cloacal (CL) swabs were quantified at predetermined time points. At 14 days post-infection (dpi), all the hens were euthanized, and different tissues were collected for genome load quantification and histopathological examination. Post-challenge, both vaccination regimes showed protection against clinical signs and exhibited significantly higher albumen parameters, higher anti-IBV serum antibodies, and significantly lower levels of IBV genome loads in OP swabs (at 3 and 7 dpi) and trachea and cecal tonsils compared to the mock-vaccinated challenged group. However, only the birds that received live attenuated plus inactivated IB vaccines had significantly lower IBV genome loads in CL swabs at 7 dpi, as well as decreased histopathological lesion scores and IBV genome loads in magnum compared to the mock-vaccinated challenged group, suggesting a slightly better performance for using live attenuated and inactivated IB vaccines in combination. Overall, the present findings show no significant difference in protection between the two vaccination regimes against the Mass IBV challenge in laying hens.
尽管在接种疫苗的鸡群中经常出现传染性支气管炎（IB）疫情，但疫苗接种仍然是家禽预防传染性支气管炎的主要控制方法。在此，针对与加拿大西部产蛋缺陷有关的马萨诸塞州（Mass）传染性支气管炎病毒（IBV）毒株的攻毒试验，评估了两种疫苗接种方案。一种疫苗接种策略仅包括活的减毒IB疫苗，另一种则使用了灭活和活的减毒IB疫苗。这两种免疫程序包括在雏鸡一日龄时用单价活的减毒IB疫苗（Mass血清型）进行初免，随后在2周龄、5周龄、9周龄和14周龄时给小母鸡接种含有Mass和康涅狄格州（Conn）血清型的二价活的减毒IB疫苗。仅在一组接种疫苗的鸡14周龄时接种灭活IB疫苗（Mass血清型）。在产蛋高峰期，通过眼鼻途径用Mass IBV分离株（15AB - 01）对母鸡进行攻毒。攻毒后，通过观察临床症状、产蛋量、蛋品质参数、血清转化以及全身T细胞亚群（CD4 +和CD8 +细胞）来评估疫苗的效力。此外，在预定时间点对咽（OP）拭子和泄殖腔（CL）拭子中的病毒基因组载量进行定量。感染后14天（dpi），对所有母鸡实施安乐死，并收集不同组织进行基因组载量定量和组织病理学检查。攻毒后，与未接种疫苗的攻毒组相比，两种疫苗接种方案均显示出对临床症状的保护作用，并且蛋白参数显著更高、抗IBV血清抗体更高，OP拭子（在3 dpi和7 dpi）以及气管和盲肠扁桃体中的IBV基因组载量显著更低。然而，与未接种疫苗的攻毒组相比，仅接受活的减毒加灭活IB疫苗的鸡在7 dpi时CL拭子中的IBV基因组载量显著更低，并且在输卵管膨大部中的组织病理学病变评分和IBV基因组载量降低，这表明联合使用活的减毒和灭活IB疫苗的效果略好。总体而言，目前的研究结果表明，两种疫苗接种方案在保护蛋鸡抵抗Mass IBV攻毒方面没有显著差异。
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