Poultry Diagnostic and Research Center, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.
Merck Animal Health, Madison, NJ 07940.
Avian Dis. 2021 Sep;65(3):500-507. doi: 10.1637/aviandiseases-D-20-00050.
To produce more-stable, live attenuated vaccines for infectious laryngotracheitis virus (ILTV), deletion of genes related to virulence has been extensively pursued. Although its function remains unknown, the open reading frame C (ORF C) is among the genes potentially associated with viral virulence that is nonessential for replication . Earlier results indicated that the ILT virus with deletion of the ORF C gene (BΔORFC) was suitable and safe for eye drop administration but was not sufficiently attenuated for administration. The objective of this study was to evaluate the safety and protection efficacy of a cell line-adapted, gene-deleted strain (BΔORFC) of ILTV when administered and/or spray (SP) by itself, or in combination with the recombinant HVT-LT (rHVT-LT) vaccine. Results indicated that vaccination with the BΔORFC strain, either by itself or in combination with an rHVT-LT vaccine, did not affect hatchability, and only marginal signs of respiratory distress were recorded for groups of chickens that received the BΔORFC strain SP. The replication and seroconversion induced by the BΔORFC strain after and SP administration was very limited, whereas the replication of the rHVT-LT vaccine was delayed when combined with the BΔORFC strain . Compared to rHVT-LT or BΔORFC when administered alone, dual vaccination with rHVT-LT + BΔORFC was more effective in mitigating clinical signs of the disease and reducing challenge virus load in the trachea. To our knowledge, this study provides the first proof of concept that ILTV strains can be sufficiently attenuated for early vaccination or at hatch; also, this study documented the benefits of using a dual (recombinant and live attenuated) hatchery vaccination strategy for ILTV.
为了生产更稳定、活的减毒传染性喉气管炎病毒（ILTV）疫苗，已经广泛研究了删除与毒力相关的基因。尽管其功能仍然未知，但开放阅读框 C（ORF C）是与病毒毒力相关的潜在基因之一，对于复制是非必需的。早期的结果表明，缺失 ORF C 基因的 ILT 病毒（BΔORFC）适合且安全滴眼给药，但对喷雾（SP）给药的减毒效果不够。本研究的目的是评估单独或与重组 HVT-LT（rHVT-LT）疫苗联合使用时，细胞系适应、基因缺失的 ILTV 株（BΔORFC）的安全性和保护效力。结果表明，单独接种 BΔORFC 株或与 rHVT-LT 疫苗联合接种均不影响孵化率，仅接受 BΔORFC 株 SP 的鸡群记录到轻微的呼吸窘迫迹象。BΔORFC 株在接种后 SP 给药后的复制和血清转化非常有限，而当与 BΔORFC 株联合使用时，rHVT-LT 疫苗的复制被延迟。与单独接种 rHVT-LT 或 BΔORFC 相比，rHVT-LT+BΔORFC 双重接种更有效地减轻疾病的临床症状和减少气管中的挑战病毒载量。据我们所知，这项研究首次提供了概念验证，即 ILTV 株可以充分减毒用于早期接种或孵化；此外，本研究还记录了使用双重（重组和活减毒）孵化场接种策略防治 ILTV 的益处。
