Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, United States.
Infect Genet Evol. 2012 Aug;12(6):1305-11. doi: 10.1016/j.meegid.2012.05.003. Epub 2012 May 17.
Coronaviruses, which are single stranded, positive sense RNA viruses, are responsible for a wide variety of existing and emerging diseases in humans and other animals. The gammacoronaviruses primarily infect avian hosts. Within this genus of coronaviruses, the avian coronavirus infectious bronchitis virus (IBV) causes a highly infectious upper-respiratory tract disease in commercial poultry. IBV shows rapid evolution in chickens, frequently producing new antigenic types, which adds to the multiple serotypes of the virus that do not cross protect. Rapid evolution in IBV is facilitated by strong selection, large population sizes and high genetic diversity within hosts, and transmission bottlenecks between hosts. Genetic diversity within a host arises primarily by mutation, which includes substitutions, insertions and deletions. Mutations are caused both by the high error rate, and limited proof reading capability, of the viral RNA-dependent RNA-polymerase, and by recombination. Recombination also generates new haplotype diversity by recombining existing variants. Rapid evolution of avian coronavirus IBV makes this virus extremely difficult to diagnose and control, but also makes it an excellent model system to study viral genetic diversity and the mechanisms behind the emergence of coronaviruses in their natural host.
冠状病毒为单链、正链 RNA 病毒，可导致人类和其他动物发生多种现有和新发疾病。γ 冠状病毒主要感染禽类宿主。在冠状病毒属中，禽传染性支气管炎病毒（IBV）可导致商业家禽发生高度传染性上呼吸道疾病。IBV 在鸡群中快速进化，频繁产生新的抗原型，这增加了病毒的多个血清型，而这些血清型之间不具有交叉保护作用。IBV 的快速进化受到宿主内强选择、大种群数量和高遗传多样性以及宿主间传播瓶颈的促进。宿主内的遗传多样性主要由突变引起，包括替换、插入和缺失。突变既由病毒 RNA 依赖性 RNA 聚合酶的高错误率和有限的校对能力引起，也由重组引起。重组通过重组现有变体也产生新的单倍型多样性。禽冠状病毒 IBV 的快速进化使得该病毒极难诊断和控制，但也使其成为研究病毒遗传多样性以及冠状病毒在其自然宿主中出现背后机制的极佳模型系统。
