Wang Jia, Wu Maocai, Hong Wenshan, Fan Xiaohui, Chen Rirong, Zheng Zuoyi, Zeng Yu, Huang Ren, Zhang Yu, Lam Tommy Tsan-Yuk, Smith David K, Zhu Huachen, Guan Yi
Joint Influenza Research Center, Shantou University Medical College, Shantou, China State Key Laboratory of Emerging Infectious Diseases and Centre of Influenza Research, School of Public Health, The University of Hong Kong, Hong Kong, China.
Joint Influenza Research Center, Shantou University Medical College, Shantou, China.
J Virol. 2016 Jan 13;90(7):3506-14. doi: 10.1128/JVI.02605-15.
The H9N2 influenza viruses that are enzootic in terrestrial poultry in China pose a persistent pandemic threat to humans. To investigate whether the continuous circulation and adaptation of these viruses in terrestrial poultry increased their infectivity to pigs, we conducted a serological survey in pig herds with H9N2 viruses selected from the aquatic avian gene pool (Y439 lineage) and the enzootic terrestrial poultry viruses (G1 and Y280 lineages). We also compared the infectivity and transmissibility of these viruses in pigs. It was found that more than 15% of the pigs sampled from 2010 to 2012 in southern China were seropositive to either G1 or Y280 lineage viruses, but none of the sera were positive to the H9 viruses from the Y439 lineage. Viruses of the G1 and Y280 lineages were able to infect experimental pigs, with detectable nasal shedding of the viruses and seroconversion, whereas viruses of the Y439 lineage did not cause a productive infection in pigs. Thus, adaptation and prevalence in terrestrial poultry could lead to interspecies transmission of H9N2 viruses from birds to pigs. Although H9N2 viruses do not appear to be continuously transmissible among pigs, repeated introductions of H9 viruses to pigs naturally increase the risk of generating mammalian-adapted or reassorted variants that are potentially infectious to humans. This study highlights the importance of monitoring the activity of H9N2 viruses in terrestrial poultry and pigs.
H9N2 subtype of influenza viruses has repeatedly been introduced into mammalian hosts, including humans and pigs, so awareness of their activity and evolution is important for influenza pandemic preparedness. However, since H9N2 viruses usually cause mild or even asymptomatic infections in mammalian hosts, they may be overlooked in influenza surveillance. Here, we found that the H9N2 viruses established in terrestrial poultry had higher infectivity in pigs than those from aquatic birds, which suggests that adaptation of the H9N2 viruses in terrestrial poultry might have increased the infectivity of the virus to mammals. Therefore, monitoring the prevalence and evolution of H9 viruses prevalent in terrestrial birds and conducting risk assessment of their threat to mammals are critical for evaluating the pandemic potential of this virus.
在中国陆地家禽中呈地方流行性的H9N2流感病毒对人类构成持续的大流行威胁。为了调查这些病毒在陆地家禽中的持续传播和适应性是否会增加其对猪的感染性，我们对从水禽基因库（Y439谱系）和地方流行性陆地家禽病毒（G1和Y280谱系）中选取的H9N2病毒的猪群进行了血清学调查。我们还比较了这些病毒在猪中的感染性和传播性。结果发现，2010年至2012年在中国南方采集的猪中，超过15%对G1或Y280谱系病毒呈血清阳性，但没有一份血清对Y439谱系的H9病毒呈阳性。G1和Y280谱系的病毒能够感染实验猪，病毒可在鼻腔检测到且出现血清转化，而Y439谱系的病毒在猪中未引起有效感染。因此，在陆地家禽中的适应性和流行可能导致H9N2病毒从鸟类跨物种传播到猪。虽然H9N2病毒似乎不会在猪之间持续传播，但H9病毒自然地反复传入猪群会增加产生可能感染人类的适应哺乳动物或重配变体的风险。本研究强调了监测陆地家禽和猪中H9N2病毒活动的重要性。
H9N2亚型流感病毒已多次传入包括人类和猪在内的哺乳动物宿主，因此了解其活动和进化对于流感大流行防范很重要。然而，由于H9N2病毒通常在哺乳动物宿主中引起轻度甚至无症状感染，它们可能在流感监测中被忽视。在此，我们发现陆地家禽中存在的H9N2病毒对猪的感染性高于水禽中的病毒，这表明H9N2病毒在陆地家禽中的适应性可能增加了该病毒对哺乳动物的感染性。因此，监测陆地鸟类中流行的H9病毒的流行情况及其对哺乳动物的威胁进行风险评估对于评估该病毒大流行潜力至关重要。
