Mashchenko Anna, Riblet Sylva M, Zavala Guillermo, García Maricarmen
Poultry Diagnostic and Research Center, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
Avian Dis. 2013 Jun;57(2 Suppl):523-31. doi: 10.1637/10413-100512-Reg.1.
Conventional live attenuated vaccines have been used as the main tool worldwide for the control of infectious laryngotracheitis. However, their suboptimal attenuation combined with poor mass administration practices allowed chicken embryo origin vaccine-derived isolates to circulate in the field, regain virulence, and be the cause of continuous outbreaks of the disease. Previous studies indicated that stable attenuation of infectious laryngotracheitis virus (ILTV) can be achieved by the deletion of individual viral genes that are not essential for viral replication in vitro. One of these genes is the glycoprotein J (gJ) gene. Its deletion provided significant attenuation to virulent ILTV strains from Europe and the United States. The objective of this study was to construct an attenuated gJ-deleted ILTV strain and evaluate its safety and efficacy for in ovo (IO) administration of commercial broilers. A novel gJ-deleted virus (N(delta)gJ) was constructed, and a 10(3) median tissue culture infective dose administered at 18 days of embryo age was considered safe because it did not affect hatchability or survivability of chickens during the first week posthatch. Broilers vaccinated IO and IO + eye drop at 14 days of age presented a significant reduction in clinical signs and reduction of virus loads after challenge, as compared with the nonvaccinated challenged group of chickens. Therefore, this study presents initial proof that the N(delta)gJ strain is a potential ILTV live-attenuated vaccine candidate suitable for IO vaccination of commercial broilers.
传统的减毒活疫苗一直是全球防控传染性喉气管炎的主要手段。然而，其减毒效果欠佳，加上大规模接种操作不当，导致鸡胚源疫苗衍生毒株在田间传播，恢复毒力，成为该病持续暴发的原因。先前的研究表明，通过缺失在体外病毒复制中并非必需的单个病毒基因，可实现传染性喉气管炎病毒（ILTV）的稳定减毒。其中一个基因是糖蛋白J（gJ）基因。其缺失使来自欧洲和美国的强毒ILTV毒株显著减毒。本研究的目的是构建一种缺失gJ基因的减毒ILTV毒株，并评估其对商品肉鸡进行胚内（IO）接种的安全性和有效性。构建了一种新型缺失gJ基因的病毒（N(δ)gJ），在胚胎18日龄时接种10³半数组织培养感染剂量被认为是安全的，因为它不会影响雏鸡出壳后第一周的孵化率或存活率。与未接种疫苗的攻毒鸡群相比，14日龄时经IO和IO + 滴眼接种疫苗的肉鸡在攻毒后临床症状显著减轻，病毒载量降低。因此，本研究初步证明N(δ)gJ毒株是一种潜在的适合对商品肉鸡进行IO接种的ILTV减毒活疫苗候选株。
