Bioengineered. 2012 Jul-Aug;3(4):222-6. doi: 10.4161/bioe.20476. Epub 2012 Jun 18.
Vaccination is the most cost effective strategy for the control and prevention of the plethora of viral diseases affecting poultry production. The major challenge for poultry vaccination is the design of vaccines that will protect against multiple pathogens via a single protective dose, delivered by mass vaccination. The Marek disease virus and the highly pathogenic avian influenza virus cause severe disease outbreaks in chickens. Vaccination with live herpesvirus of turkeys protects chickens from Marek disease and inactivated influenza viruses are used as antigens to protect chickens against influenza virus infections. We developed herpesvirus of turkeys (HVT) as a vaccine vector that can act as a dual vaccine against avian influenza and Marek disease. The HVT vector was developed using reverse genetics based on an infectious bacterial artificial chromosome (BAC) clone of HVT. The BAC carrying the HVT genome was genetically modified to express the haemagglutinin (HA) gene of a highly pathogenic H7N1 virus. The resultant recombinant BAC construct containing the modified HVT sequence was transfected into chicken embryo fibroblast (CEF) cells and HVT recombinants (rHVT-H7HA) harbouring the H7N1 HA were recovered. Analysis of cultured CEF cells infected with the rHVT-H7HA showed that HA was expressed and that the rescued rHVT-H7HA stocks were stable during several in vitro passages with no difference in growth kinetics compared with the parent HVT. Immunization of one-day-old chicks with rHVT-H7HA induced H7-specific antibodies and protected chickens challenged with homologous H7N1 virus against virus shedding, clinical disease and death. The rHVT-H7HA vaccine also induced strong and long-lasting antibody titers against H7HA in chickens that were vaccinated in ovo 3 d before hatching. This vaccine supports differentiation between infected and vaccinated animals (DIVA), because no influenza virus nucleoprotein-specific antibodies were detected in the rHVT-H7HA vaccinated birds. The rHVT-H7HA not only provided protection against a lethal challenge with highly pathogenic H7N1 virus but also against highly virulent Marek disease virus and can be used as a DIVA vaccine.
疫苗接种是控制和预防影响家禽生产的大量病毒疾病的最具成本效益的策略。家禽疫苗接种的主要挑战是设计能够通过单次保护性剂量保护多种病原体的疫苗，通过大规模疫苗接种来实现。马立克氏病病毒和高致病性禽流感病毒会导致鸡群发生严重的疾病暴发。使用活火鸡疱疹病毒对鸡进行免疫接种可以预防马立克氏病，而灭活流感病毒则被用作抗原，以保护鸡免受流感病毒感染。我们开发了火鸡疱疹病毒（HVT）作为一种疫苗载体，可作为预防禽流感和马立克氏病的双重疫苗。HVT 载体是使用基于 HVT 感染性细菌人工染色体（BAC）克隆的反向遗传学开发的。携带 HVT 基因组的 BAC 经过基因修饰，表达高致病性 H7N1 病毒的血凝素（HA）基因。含有修饰的 HVT 序列的重组 BAC 构建体被转染到鸡胚成纤维细胞（CEF）中，并回收含有 H7N1 HA 的重组 HVT（rHVT-H7HA）。分析感染 rHVT-H7HA 的培养 CEF 细胞表明，HA 得到了表达，并且与亲本 HVT 相比，回收的 rHVT-H7HA 株在多次体外传代过程中保持稳定，生长动力学没有差异。用 rHVT-H7HA 免疫 1 日龄雏鸡可诱导产生 H7 特异性抗体，并可保护接种鸡免受同源 H7N1 病毒的病毒脱落、临床疾病和死亡。rHVT-H7HA 疫苗还可诱导在孵化前 3 天胚内接种的鸡中对 H7HA 产生强烈且持久的抗体滴度。这种疫苗支持感染与接种动物的区分（DIVA），因为在 rHVT-H7HA 接种的鸟类中未检测到流感病毒核蛋白特异性抗体。rHVT-H7HA 不仅为高致病性 H7N1 病毒的致死性挑战提供了保护，而且还为高致病性马立克氏病病毒提供了保护，可作为 DIVA 疫苗使用。
