Zoonosis Science Center, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
Department of Migration, Max Planck Institute of Animal Behavior, Radolfzell, Germany.
Microbiol Spectr. 2023 Aug 17;11(4):e0258622. doi: 10.1128/spectrum.02586-22. Epub 2023 Jun 26.
Cross-species transmission of influenza A virus (IAV) from wild waterfowl to poultry is the first step in a chain of events that can ultimately lead to exposure and infection of humans. Herein, we study the outcome of infection with eight different mallard-origin IAV subtypes in two different avian hosts: tufted ducks and chickens. We found that infection and shedding patterns as well as innate immune responses were highly dependent on viral subtypes, host species, and inoculation routes. For example, intraoesophageal inoculation, commonly used in mallard infection experiments, resulted in no infections in contrast to oculonasal inoculation, suggesting a difference in transmission routes. Despite H9N2 being endemic in chickens, inoculation of mallard-origin H9N2 failed to cause viable infection beyond 1 day postinfection in our study design. The innate immune responses were markedly different in chickens and tufted ducks, and despite the presence of retinoic acid-inducible gene-I (RIG-I) in tufted duck transcriptomes, it was neither up nor downregulated in response to infection. Overall, we have revealed the heterogeneity of infection patterns and responses in two markedly different avian hosts following a challenge with mallard-origin IAV. These virus-host interactions provide new insights into important aspects of interspecies transmission of IAV. Our current findings highlight important aspects of IAV infection in birds that have implications for our understanding of its zoonotic ecology. In contrast to mallards where the intestinal tract is the main site of IAV replication, chickens and tufted ducks show limited or no signs of intestinal infection suggesting that the fecal-oral transmission route might not apply to all bird IAV host species. Our results indicate that mallard-origin IAVs undergo genetic changes upon introduction into new hosts, suggesting rapid adaptation to a new environment. However, similar to the mallard, chickens and tufted ducks show a limited immune response to infection with low pathogenic avian influenza viruses. These findings and future studies in different IAV hosts are important for our understanding of barriers to IAV transmission between species and ultimately from the wild reservoir to humans.
甲型流感病毒（IAV）从野生水禽向家禽的跨物种传播是导致人类暴露和感染的一系列事件的第一步。在此，我们研究了 8 种不同的野鸭源 IAV 亚型在两种不同禽类宿主中的感染结果：绿头鸭和鸡。我们发现，感染和脱落模式以及先天免疫反应高度依赖于病毒亚型、宿主物种和接种途径。例如，在本研究设计中，经口内接种通常用于绿头鸭感染实验，但不会导致感染，而经眼鼻接种则相反，这表明存在不同的传播途径。尽管 H9N2 在鸡中流行，但在我们的研究设计中，接种野鸭源性 H9N2 无法在感染后 1 天以上引起可存活的感染。尽管绿头鸭转录组中存在视黄酸诱导基因-I（RIG-I），但鸡和绿头鸭的先天免疫反应明显不同，感染后也没有上调或下调。总体而言，我们揭示了两种明显不同的禽类宿主在受到野鸭源性 IAV 挑战后感染模式和反应的异质性。这些病毒-宿主相互作用为 IAV 的种间传播的重要方面提供了新的见解。我们的研究结果强调了鸟类中 IAV 感染的重要方面，这些方面对我们理解其人畜共患病生态学具有重要意义。与 IAV 在肠道中主要复制的绿头鸭不同，鸡和绿头鸭表现出有限或没有肠道感染的迹象，这表明粪-口传播途径可能不适用于所有鸟类 IAV 宿主物种。我们的研究结果表明，野鸭源性 IAV 在引入新宿主后会发生遗传变化，表明其对新环境的快速适应。然而，与绿头鸭类似，鸡和绿头鸭对低致病性禽流感病毒的感染表现出有限的免疫反应。这些发现和未来在不同 IAV 宿主中的研究对于我们理解 IAV 在物种间传播的障碍以及最终从野生动物宿主传播到人类具有重要意义。
