Asia-Pacific Centre for Animal Health, Melbourne Veterinary School, The University of Melbourne, Parkville, Australia.
Avian Pathol. 2020 Aug;49(4):369-379. doi: 10.1080/03079457.2020.1754331. Epub 2020 Jun 2.
Latency is an important feature of infectious laryngotracheitis virus (ILTV) yet is poorly understood. This study aimed to compare latency characteristics of vaccine (SA2) and field (CL9) strains of ILTV, establish an reactivation system and examine ILTV infection in peripheral blood mononuclear cells (PBMC) in specific pathogen-free chickens. Birds were inoculated with SA2 or CL9 ILTV and then bled and culled at 21 or 35 days post-inoculation (dpi). Swabs (conjunctiva, palatine cleft, trachea) and trigeminal ganglia (TG) were examined for ILTV DNA using PCR. Half of the TG, trachea and PBMC were co-cultivated with cell monolayers to assess reactivation of ILTV infection. ILTV DNA was detected in the trachea of approximately 50% of ILTV-inoculated birds at both timepoints. At 21 dpi, ILTV was detected in the TG only in 29% and 17% of CL9- and SA2-infected birds, respectively. At 35 dpi, ILTV was detected in the TG only in 30% and 10% of CL9- and SA2-infected birds, respectively. Tracheal organ co-cultures from 30% and 70% of CL9- and SA2-infected birds, respectively, were negative for ILTV DNA at cull but yielded quantifiable DNA within 6 days post-explant (dpe). TG co-cultivation from 30% and 40% of CL9-and SA2-infected birds, respectively, had detectable ILTV DNA within 6 dpe. Latency characteristics did not substantially vary based on the strain of virus inoculated or between sampling timepoints. These results advance our understanding of ILTV latency and reactivation. Following inoculation, latent ILTV infection was detected in a large proportion of chickens, irrespective of whether a field or vaccine strain was inoculated. reactivation of latent ILTV was readily detected in tracheal and trigeminal ganglia co-cultures using PCR. ILTV latency observed in SPF chickens at 21 days post-infection was not substantially different to 35 days post-infection.
潜伏期是传染性喉气管炎病毒（ILTV）的一个重要特征，但了解甚少。本研究旨在比较疫苗（SA2）和田间（CL9）株 ILTV 的潜伏期特征，建立再激活系统，并研究无特定病原体鸡外周血单核细胞（PBMC）中的 ILTV 感染。鸡接种 SA2 或 CL9 ILTV 后，在接种后 21 或 35 天采血和扑杀。使用 PCR 检测拭子（结膜、腭裂、气管）和三叉神经节（TG）中的 ILTV DNA。将一半的 TG、气管和 PBMC 与细胞单层共培养，以评估 ILTV 感染的再激活。在两个时间点，约 50%的 ILTV 接种鸡的气管中均可检测到 ILTV DNA。在 21 dpi 时，CL9 和 SA2 感染鸡的 TG 中仅分别检测到 29%和 17%的 ILTV。在 35 dpi 时，CL9 和 SA2 感染鸡的 TG 中仅分别检测到 30%和 10%的 ILTV。分别从 30%和 70%的 CL9 和 SA2 感染鸡的气管器官共培养物中，扑杀时 ILTV DNA 为阴性，但在培养后 6 天（dpe）内可检测到定量 DNA。分别从 30%和 40%的 CL9 和 SA2 感染鸡的 TG 共培养物中，在 6 dpe 内可检测到 ILTV DNA。潜伏期特征与接种的病毒株或采样时间点之间没有显著差异。这些结果提高了我们对 ILTV 潜伏期和再激活的理解。接种后，无论接种的是田间株还是疫苗株，大量鸡都检测到潜伏性 ILTV 感染。使用 PCR 可在气管和三叉神经节共培养物中轻易检测到潜伏性 ILTV 的再激活。在感染后 21 天的 SPF 鸡中观察到的 ILTV 潜伏期与感染后 35 天的潜伏期没有显著差异。
