The H7N9 subtype of avian influenza A virus was for the first time found to infect humans since the outbreaks in March 2013 in China. Concerns about its risk on human public health rises, and the mechanisms of pathogenesis and host immunity are studied. The ultra-structure of H7N9 virus infections is characterized, and reported in this issue. Viruses were grown in Madin-Darby canine kidney (MDCK) cells and human lung explants tissues, and morphogenesis features of viral replication were examined by electron microscopy. The cover depicts virus particles budding/releasing in alveolar space and an induced sieve-like structure in the cytoplasm.
Kuohan Li, Wint Wint Phoo and Dahai Luo. Functional interplay among the flavivirus NS3 protease, helicase, and cofactors[J]. Virologica Sinica, 2014, 29(2): 74-85. doi: 10.1007/s12250-014-3438-6.
Flaviviruses are positive-sense RNA viruses, and many are important human pathogens. Nonstructural protein 2B and 3 of the flaviviruses (NS2BNS3) form an endoplasmic reticulum (ER) membraneassociated hetero-dimeric complex through the NS2B transmembrane region. The NS2BNS3 complex is multifunctional. The N-terminal region of NS3, and its cofactor NS2B fold into a protease that is responsible for viral polyprotein processing, and the C-terminal domain of NS3 possesses NTPase/RNA helicase activities and is involved in viral RNA replication and virus particle formation. In addition, NS2BNS3 complex has also been shown to modulate viral pathogenesis and the host immune response. Because of the essential functions that the NS2BNS3 complex plays in the flavivirus life cycle, it is an attractive target for antiviral development. This review focuses on the recent biochemical and structural advances of NS2BNS3 and provides a brief update on the current status of drug development targeting this viral protein complex.
Liming Yan, Huan Liu, Xiaoming Li and Qin Fang. The VP2 protein of grass carp reovirus (GCRV) expressed in a baculovirus exhibits RNA polymerase activity[J]. Virologica Sinica, 2014, 29(2): 86-93. doi: 10.1007/s12250-014-3366-5.
The double-shelled grass carp reovirus (GCRV) is capable of endogenous RNA transcription and processing. Genome sequence analysis has revealed that the protein VP2, encoded by gene segment 2 (S2), is the putative RNA-dependent RNA polymerase (RdRp). In previous work, we have ex-pressed the functional region of VP2 that is associated with RNA polymerase activity (denoted as rVP2390-900) in E. coli and have prepared a polyclonal antibody against VP2. To characterize the GCRV RNA polymerase, a recombinant full-length VP2 (rVP2) was first constructed and expressed in a baculovirus system, as a fusion protein with an attached His-tag. Immunofluorescence (IF) assays, together with immunoblot (IB) analyses from both expressed cell extracts and purified Histagged rVP2, showed that rVP2 was successfully expressed in Sf9 cells. Further characterization of the replicase activity showed that purified rVP2 and GCRV particles exhibited poly(C)-dependent poly(G) polymerase activity. The RNA enzymatic activity required the divalent cation Mg2+, and was optimal at 28 ℃. The results provide a foundation for further studies on the RNA polymerases of aquareoviruses during viral transcription and replication.
Tiejun Bing, Hong Yu, Yue Li, Lei Sun, Juan Tan, Yunqi Geng and Wentao Qiao. Characterization of a full-length infectious clone of bovine foamy virus 3026[J]. Virologica Sinica, 2014, 29(2): 94-102. doi: 10.1007/s12250-014-3382-5.
The biological features of most foamy viruses (FVs) are poorly understood, including bovine foamy virus (BFV). BFV strain 3026 (BFV3026) was isolated from the peripheral blood mononuclear cells of an infected cow in Zhangjiakou, China. A full-length genomic clone of BFV3026 was obtained from BFV3026-infected cells, and it exhibited more than 99% amino acid (AA) homology to another BFV strain isolated in the USA. Upon transfection into fetal canine thymus cells, the full-length BFV3026 clone produced viral structural and auxiliary proteins, typical cytopathic effects, and virus particles. These results demonstrate that the full-length BFV3026 clone is fully infectious and can be used in further BFV3026 research.
Haiwei Wang, Shanshan Song, Jianxiong Zeng, Guohui Zhou, Decheng Yang, Te Liang and Li Yu. Single amino acid substitution of VP1 N17D or VP2 H145Y confers acid-resistant phenotype of type Asia1 foot-and-mouth disease virus[J]. Virologica Sinica, 2014, 29(2): 103-111. doi: 10.1007/s12250-014-3426-x.
Infection by foot-and-mouth disease virus (FMDV) is triggered by the acidic pH in endosomes after virus uptake by receptor-mediated endocytosis. However, dissociation of the FMDV 146S particle in mildly acidic conditions renders inactivated foot-and-mouth disease (FMD) vaccines much less effective. Type Asia1 FMDV mutants with increased resistance to acid inactivation were selected to study the molecular basis of viral resistance to acid-induced disassembly and improve the acid stability of FMDV. Sequencing of capsid-coding regions revealed four amino acid replacements (VP1 N17D, VP2 H145Y, VP2 G192D, and VP3 K153E) in the viral population of the acid-selected 10th passage. We performed single or combined mutagenesis using a reverse genetic system, and our results provide direct experimental evidence that VP2 H145Y or VP1 N17D substitution confers an acid-resistant phenotype to type Asia1 FMDV.
Ze Liu, Shukun Wang, Rusong Yang and Xia Ou. A case-control study of risk factors for severe hand-foot-mouth disease in Yuxi, China, 2010–2012[J]. Virologica Sinica, 2014, 29(2): 123-125. doi: 10.1007/s12250-014-3384-3.
Haizhou Liu, Na Han, Wei Fang, James Adams, Kou Zheng, Tianxian Li, Zhihong Hu and Simon Rayner. The limited number of available nucleotide and protein sequence data from the recent H7N9 cases in China impeded investigation and characterization of the outbreak[J]. Virologica Sinica, 2014, 29(2): 126-127. doi: 10.1007/s12250-014-3394-1.
Fang Fang Yuan, Zlatibor Velickovic, Lesley J Ashton, Wayne B Dyer, Andrew F Geczy, Heather Dunckley, Garry W Lynch and John S Sullivan. Influence of HLA gene polymorphisms on susceptibility and outcome post infection with the SARS-CoV virus[J]. Virologica Sinica, 2014, 29(2): 128-130. doi: 10.1007/s12250-014-3398-x.
Yingzi Liang, Wei Zhang, Huajun Zhang and Zhengli Shi. 3'-UTR sequence of Macrobrachium rosenbergii extra small virus (XSV) is important for viral RNA packaging[J]. Virologica Sinica, 2014, 29(2): 133-135. doi: 10.1007/s12250-014-3418-x.
Dipongkor Saha, Rubén Del Pozo Sacristán, Nicolaas Van Renne, Liping Huang, Ruben Decaluwe, Annelies Michiels, Alfonso Lopez Rodriguez, Maria José Rodríguez, Margarita García Durán, Ilse Declerk, Dominiek Maes and Hans J. Nauwynck. Anti-porcine circovirus type 2 (PCV2) antibody placental barrier leakage from sow to fetus: impact on the diagnosis of intra-uterine PCV2 infection[J]. Virologica Sinica, 2014, 29(2): 136-138. doi: 10.1007/s12250-014-3432-z.