Data_Sheet_1.DOC

Newcastle disease (ND), caused by infections with virulent strains of Newcastle disease virus (NDV), is one of the most important infectious disease affecting wild, peridomestic, and domestic birds worldwide. Vaccines constructed from live, low-virulence (lentogenic) viruses are the most accepted prevention and control strategies for combating ND in poultry across the globe. Avian macrophages are one of the first cell lines of defense against microbial infection, responding to signals in the microenvironment. Although macrophages are considered to be one of the main target cells for NDV infection in vivo, very little is known about the ability of NDV to infect chicken macrophages, and virulence mechanisms of NDV as well as the polarized activation patterns of macrophages and correlation with viral infection and replication. In the present study, a cell culture model (chicken bone marrow macrophage cell line HD11) and three different virulence and genotypes of NDV (including class II virulent NA-1, class II lentogenic LaSota, and class I lentogenic F55) were used to solve the above underlying questions. Our data indicated that all three NDV strains had similar replication rates during the early stages of infection. Virulent NDV titers were shown to increase compared to the other lentogenic strains, and this growth was associated with a strong upregulation of both pro-inflammatory M1-like markers/cytokines and anti-inflammatory M2-like markers/cytokines in chicken macrophages. Virulent NDV was found to block toll-like receptor (TLR) 7 expression, inducing higher expression of type I interferons in chicken macrophages at the late stage of viral infection. Only virulent NDV replication can be inhibited by pretreatment with TLR7 ligand. Overall, this study demonstrated that virulent NDV activates a M1-/M2-like mixed polarized activation of chicken macrophages by inhibition of TLR7, resulting in enhanced replication compared to lentogenic viruses.

由强毒力新城疫病毒（Newcastle disease virus, NDV）感染引发的新城疫（Newcastle disease, ND），是全球范围内危害野生、近郊家养与家养禽类的重要传染病之一。以低毒力（缓发型）活病毒制备的疫苗，是全球范围内防控家禽新城疫的主流防治策略。禽巨噬细胞是机体抵御微生物感染的首批防御细胞系，可响应微环境中的信号。尽管巨噬细胞被认为是体内新城疫病毒感染的主要靶细胞之一，但目前对于新城疫病毒感染鸡巨噬细胞的能力、病毒的毒力机制，以及巨噬细胞的极化激活模式与病毒感染和复制的相关性，仍知之甚少。本研究采用鸡骨髓巨噬细胞系HD11（chicken bone marrow macrophage cell line HD11）这一细胞模型，以及3株不同毒力与基因型的新城疫病毒（包括基因II型强毒株NA-1、基因II型缓发型毒株LaSota，以及基因I型缓发型毒株F55），旨在解答上述尚未明确的科学问题。研究数据显示，3株新城疫病毒在感染早期的复制速率并无显著差异。但强毒新城疫病毒的滴度相较于其余2株缓发型毒株显著升高，且该增殖过程伴随鸡巨噬细胞中促炎性M1样标志物/细胞因子与抗炎性M2样标志物/细胞因子的显著上调。此外，强毒新城疫病毒可阻断Toll样受体7（Toll-like receptor, TLR7）的表达，并在病毒感染后期诱导鸡巨噬细胞内I型干扰素的高表达。仅强毒新城疫病毒的复制可被Toll样受体7配体预处理所抑制。综上，本研究证实，强毒新城疫病毒通过抑制Toll样受体7，激活鸡巨噬细胞的M1样/M2样混合极化状态，相较于缓发型毒株，其在鸡巨噬细胞内的复制能力得到显著增强。