Sun Hailiang, Blackmon Sherry, Yang Guohua, Waters Kaitlyn, Li Tao, Tangwangvivat Ratanaporn, Xu Yifei, Shyu Daniel, Wen Feng, Cooley Jim, Senter Lucy, Lin Xiaoxu, Jarman Richard, Hanson Larry, Webby Richard, Wan Xiu-Feng
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, USA.
Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
J Virol. 2017 Oct 13;91(21). doi: 10.1128/JVI.00637-17. Print 2017 Nov 1.
Two subtypes of influenza A virus (IAV), avian-origin canine influenza virus (CIV) H3N2 (CIV-H3N2) and equine-origin CIV H3N8 (CIV-H3N8), are enzootic in the canine population. Dogs have been demonstrated to seroconvert in response to diverse IAVs, and naturally occurring reassortants of CIV-H3N2 and the 2009 H1N1 pandemic virus (pdmH1N1) have been isolated. We conducted a thorough phenotypic evaluation of CIV-H3N2 in order to assess its threat to human health. Using ferret-generated antiserum, we determined that CIV-H3N2 is antigenically distinct from contemporary human H3N2 IAVs, suggesting that there may be minimal herd immunity in humans. We assessed the public health risk of CIV-H3N2 × pandemic H1N1 (pdmH1N1) reassortants by characterizing their genetic compatibility and pathogenicity and transmissibility. Using a luciferase minigenome assay, we quantified the polymerase activity of all possible 16 ribonucleoprotein (RNP) complexes (PB2, PB1, PA, NP) between CIV-H3N2 and pdmH1N1, identifying some combinations that were more active than either parental virus complex. Using reverse genetics and fixing the CIV-H3N2 hemagglutinin (HA), we found that 51 of the 127 possible reassortant viruses were viable and able to be rescued. Nineteen of these reassortant viruses had high-growth phenotypes , and 13 of these replicated in mouse lungs. A single reassortant with the NP and HA gene segments from CIV-H3N2 was selected for characterization in ferrets. The reassortant was efficiently transmitted by contact but not by the airborne route and was pathogenic in ferrets. Our results suggest that CIV-H3N2 reassortants may pose a moderate risk to public health and that the canine host should be monitored for emerging IAVs. IAV pandemics are caused by the introduction of novel viruses that are capable of efficient and sustained transmission into a human population with limited herd immunity. Dogs are a a potential mixing vessel for avian and mammalian IAVs and represent a human health concern due to their susceptibility to infection, large global population, and close physical contact with humans. Our results suggest that humans are likely to have limited preexisting immunity to CIV-H3N2 and that CIV-H3N2 × pdmH1N1 reassortants have moderate genetic compatibility and are transmissible by direct contact in ferrets. Our study contributes to the increasing evidence that surveillance of the canine population for IAVs is an important component of pandemic preparedness.
甲型流感病毒（IAV）的两种亚型，禽源犬流感病毒（CIV）H3N2（CIV-H3N2）和马源CIV H3N8（CIV-H3N8），在犬类群体中呈地方流行性。已证明犬类会因多种IAV而发生血清转化，并且已分离出CIV-H3N2与2009年H1N1大流行病毒（pdmH1N1）的自然重组体。我们对CIV-H3N2进行了全面的表型评估，以评估其对人类健康的威胁。使用雪貂产生的抗血清，我们确定CIV-H3N2在抗原性上与当代人类H3N2 IAV不同，这表明人类中可能存在的群体免疫力极低。我们通过表征CIV-H3N2×大流行H1N1（pdmH1N1）重组体的遗传相容性、致病性和传播性，评估了它们对公共卫生的风险。使用荧光素酶微型基因组测定法，我们量化了CIV-H3N2和pdmH1N1之间所有可能的16种核糖核蛋白（RNP）复合物（PB2、PB1、PA、NP）的聚合酶活性，确定了一些比亲本病毒复合物更具活性的组合。使用反向遗传学并固定CIV-H3N2血凝素（HA），我们发现127种可能的重组病毒中有51种是可行的且能够被拯救。其中19种重组病毒具有高生长表型，其中13种在小鼠肺中复制。选择一种具有来自CIV-H3N2的NP和HA基因片段的重组体在雪貂中进行表征。该重组体通过接触有效传播，但不能通过空气传播途径传播，并且在雪貂中具有致病性。我们的结果表明，CIV-H3N2重组体可能对公共卫生构成中度风险，并且应该监测犬类宿主中出现的IAV。IAV大流行是由引入能够在群体免疫力有限的人群中有效且持续传播的新型病毒引起的。犬类是禽源和哺乳动物IAV的潜在混合宿主，由于它们易受感染、全球数量众多以及与人类有密切的身体接触，因此代表了一个人类健康问题。我们的结果表明，人类对CIV-H3N2可能预先存在的免疫力有限，并且CIV-H3N2×pdmH1N1重组体具有中等遗传相容性，并且能够在雪貂中通过直接接触传播。我们的研究进一步证明，监测犬类群体中的IAV是大流行防范的重要组成部分。
