Su Lan, Xu Congrui, Cheng Chuangang, Lei Chengfeng, Sun Xiulian
Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Viruses. 2017 Apr 1;9(4):66. doi: 10.3390/v9040066.
(DpCPV) is an important pathogen of , but little is known about the mechanisms of DpCPV infection. Here, we investigated the effects of VP3, VP4 and VP5 structural proteins on the viral invasion. Both the C-terminal of VP3 (methyltransferase (MTase) domain) and VP4 (A-spike) bound to midgut brush border membrane vesicles (BBMVs) in a dose-dependent manner, and the binding was inhibited by purified DpCPV virions. Importantly, anti-MTase and anti-VP4 antibodies inhibited viral binding to BBMVs. Using far-Western blots, a 65 kDa protein in BBMVs, identified as alkaline phosphatase protein (ALP) by mass spectrometry, specifically interacted with DpCPV MTase. The interaction between MTase and ALP was verified by co-immunoprecipitation in vitro. Pretreatment of BBMVs with an anti-ALP antibody or incubation of DpCPV virions with prokaryotically expressed ALP reduced viral attachment. Additionally, ALP inhibited DpCPV infection in larvae. Our data provide evidence that the MTase domain and A-spike function as viral attachment proteins during the DpCPV infection process, and ALP is the ligand that interacts with DpCPV via the MTase domain. These results augment our understanding of the mechanisms used by cypoviruses to enter their hosts.
浓核病毒（DpCPV）是[某种生物]的重要病原体，但对DpCPV感染机制知之甚少。在此，我们研究了VP3、VP4和VP5结构蛋白对病毒入侵的影响。VP3的C末端（甲基转移酶（MTase）结构域）和VP4（A刺突）均以剂量依赖性方式与[某种生物]中肠刷状缘膜囊泡（BBMVs）结合，且这种结合受到纯化的DpCPV病毒粒子的抑制。重要的是，抗MTase和抗VP4抗体抑制病毒与BBMVs的结合。利用Far-Western印迹法，在BBMVs中鉴定出一种65 kDa的蛋白质，经质谱分析确定为碱性磷酸酶蛋白（ALP），它与DpCPV MTase特异性相互作用。MTase与ALP之间的相互作用通过体外共免疫沉淀得到验证。用抗ALP抗体预处理BBMVs或使DpCPV病毒粒子与原核表达的ALP孵育可减少病毒附着。此外，ALP抑制[某种生物]幼虫中的DpCPV感染。我们的数据表明，在DpCPV感染过程中，MTase结构域和A刺突作为病毒附着蛋白发挥作用，并且ALP是通过MTase结构域与DpCPV相互作用的配体。这些结果加深了我们对质型多角体病毒进入宿主所采用机制的理解。
