Colorado State University, Fort Collins, CO, USA.
Fogarty International Center, Bethesda, MD, USA.
J Gen Virol. 2012 Dec;93(Pt 12):2575-2583. doi: 10.1099/vir.0.045427-0. Epub 2012 Sep 5.
Low-pathogenicity avian influenza virus (LPAIV) can lead to epizootics that cause economic losses in poultry or the emergence of human-infectious strains. LPAIVs experience a complex immunity landscape as they are endemic in numerous host species, and many antigenically distinct strains co-circulate. Prevention and control of emergence of detrimental strains requires an understanding of infection/transmission characteristics of the various subtypes in different hosts, including interactions between subtypes. In order to develop analytical frameworks for examining control efficacy, quantification of heterosubtypic immunity interactions is fundamental. However, these data are scarce, especially for wild avian subtypes in natural hosts. Consequently, in this study, three host species (mallards, quail and pheasants) were infected with two LPAIV subtypes isolated from wild birds: H3N8 and H4N6. The recovered hosts were also reinfected with the alternate subtype to measure the effects of heterosubtypic immunity. Oropharyngeal and cloacal swabs were collected and viral RNA load was quantified by real-time RT-PCR. For secondary infections in recovered hosts, peak viral load was up to four orders of magnitude lower and shedding length was up to 4 days shorter. However, both the magnitude and presence of heterosubtypic immunity varied across specific host species/subtype combinations. Using a mathematical model of virus replication, the variation in virus replication dynamics due to host individuals was quantified. It was found that accounting for individual heterogeneity is important for drawing accurate conclusions about treatment effects. These results are relevant for developing epidemiological models to inform control practices and for analysing virus replication data.
低致病性禽流感病毒（LPAIV）可引发禽类爆发疾病，导致经济损失，或出现可感染人类的毒株。LPAIV 在众多宿主物种中流行，存在许多抗原不同的毒株共同传播，因此经历着复杂的免疫景观。为了预防和控制有害毒株的出现，需要了解各种宿主中不同亚型的感染/传播特征，包括亚型之间的相互作用。为了开发用于检查控制效果的分析框架，量化异源亚型免疫相互作用是基础。然而，这些数据非常稀缺，特别是在自然宿主的野生鸟类亚型中。因此，在这项研究中，三种宿主物种（野鸭、鹌鹑和野鸡）感染了两种从野生鸟类中分离出的 LPAIV 亚型：H3N8 和 H4N6。回收的宿主也被重新感染了另一种亚型，以测量异源亚型免疫的影响。采集口咽和泄殖腔拭子，并通过实时 RT-PCR 定量病毒 RNA 载量。在回收宿主的二次感染中，峰值病毒载量低至四个数量级，排出时间短至 4 天。然而，异源亚型免疫的幅度和存在因特定宿主物种/亚型组合而异。使用病毒复制的数学模型，量化了由于宿主个体差异导致的病毒复制动力学的变化。结果发现，考虑个体异质性对于得出关于治疗效果的准确结论非常重要。这些结果对于开发流行病学模型以告知控制实践和分析病毒复制数据具有重要意义。
