H7N9病毒的来源和重组模式

目的通过序列分析揭示H7N9病毒的来源和重组产生模式。方法收集H7N9序列，运用BLAST、MEGA5.0等生物信息
学软件分析序列相似性、多序列比对、构建进化树，确定H7N9病毒各节段序列的亲缘序列，模拟H7N9重组产生方式。结果系
统进化树显示HA、NA、PB2和NS节段最近缘关系序列只有一个；而PB1、PA、NP和MP节段序列，分布于不同的两个分枝。通
过组合分析亲缘序列，可以将目前流行的H7N9病毒分为5型：A、B、A/Shanghai/1/2013-H7N9、A/Pigeon/Shanghai/S1069-H7N9
和A/Zhejiang/HZ1/2013-H7N9。A型又可以分为A1和A2亚型。结论通过对序列的组合分析，推测此次H7N9病毒流行至少
由5个病毒经过4次重组产生，产生两个主要流行株A和B型。A1和A2亚型的出现是同一次重组过程中产生两株不同产物；A/
Pigeon/Shanghai/S1069-H7N9 是A 型H7N9 病毒在流行期间与当地H9N2 病毒的再一次重组产生。A/Zhejiang/HZ1/
2013-H7N9是A2亚型和B型重组后产生的混合型。

Origin and the recombinant model of H7N9 virus prevailing in China

Objective To investigate the origin and the recombinant model of H7N9 virus prevailing in China by sequence
analysis. Methods The sequences of H7N9 virus were collected and analyzed with the software BLAST and MEGA 5.0. The
phylogenetic trees were constructed after multiple sequences alignment. The homologous sequences of H7N9 segments were
determined and the model was inferred according to the origin of H7N9 segments. Results The most relevant sequences of
HA, NA, NS and PB2 segments were located at one branch of the phylogenetic tree, while the closest relevant sequences of
PB1, PA, NP and MP contained two H9N2 virus origins. According to the analysis of sequence origin, H7N9 viruses might be
divided into 5 genotypes: namely A, B, A/Shanghai/1/2013-H7N9, A/Pigeon/Shanghai/S1069-H7N9 and A/Zhejiang/HZ1/
2013-H7N9, and the genotype A consisted of A1 and A2 subtypes. Conclusion The prevailing H7N9 virus might be derived
from 5 different viruses after 4 times of recombination, which resulted in the two major types of A and B. The subtypes of A1
and A2 were two different derivatives from one reassortant. The A/Pigeon/Shanghai/S1069-H7N9 strain might be the
recombinant of type A H7N9 virus with a local H9N2 virus during the H7N9 epidemics. The A/Zhejiang/HZ1/2013-H7N9
strain could be the re-arrangement of subtype A2 with type B H7N9 virus.