Role of JC virus agnoprotein in virion formation

JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and causes progressive multifocal leukoencephalopathy in humans. JCV encodes early proteins (large T antigen, small T antigen, and T' antigen) and four late proteins (agnoprotein, and three viral capsid proteins, VP1, VP2, and VP3). In the current study, a novel function for JCV agnoprotein in the morphogenesis of JC virion particles was identified. It was found that mature virions of agnoprotein-negative JCV are irregularly shaped. Sucrose gradient sedimentation and cesium chloride gradient ultracentrifugation analyses revealed that the particles of virus lacking agnoprotein assemble into irregularly sized virions, and that agnoprotein alters the efficiency of formation of VP1 virus-like particles. An in vitro binding assay and immunocytochemistry revealed that agnoprotein binds to glutathione S-transferase fusion proteins of VP1 and that some fractions of agnoprotein colocalize with VP1 in the nucleus. In addition, gel filtration analysis of formation of VP1-pentamers revealed that agnoprotein enhances formation of these pentamers by interacting with VP1. The present findings suggest that JCV agnoprotein plays a role, similar to that of SV40 agnoprotein, in facilitating virion assembly.     

Location of Drosophila C virus target organs in Drosophila host population by an immunofluorescence technique

Using the immunofluorescence technique we attempted to locate, in the Drosophila host, Drosophila C virus (DCV) target organs after injection of adult flies. Two kinds of organs were infected: those which play a role in reproductive function, including the fat body and follicular cells, and other, including thoracic muscle fibers, tracheal cells, and the digestive tract. These organs correspond to those found in previous tests. Fat body proteins of a DCV-free host population seemed to cross-react with antivirus C antibody. This immune response depended on the origin of the host population. It is known that, when DCV is ingested from the first larval instar, it may have beneficial effects upon host development and reproduction. As DCV has a narrow host spectrum, it is suggested that it is well adapted to its natural host. Hypotheses are proposed to explain how the host resists viral infection and may in fact benefit from such an infection.     

Drosophila C virus cycle during the development of two Drosophila melanogaster strains (Charolles and Champetières) after larval contamination by food.

Drosophila C virus (DCV) cycle during Drosophila melanogaster development was studied after feeding contamination at the first, most sensitive, instar (L1). Two Drosophila strains were examined and compared. Presence of DCVC in apparently healthy animals (L3 larvae bred on a contaminated rearing medium and adults coming from larvae which were grown on medium containing DCVC) was demonstrated by biological tests. Using the immunofluorescence technique, DCV was exhibited in the diseased Charolles larvae, in the lumen of the digestive tract and in the basal part of gut cells which is in contact with the haemolymph. On the contrary, in Charolles larvae which seemed 'healthy', DCV was exhibited only in the lumen of the digestive tract at the apical boundary of the gut cells. But DCV typical protein capsid was not shown in the tissues of Drosophila L3 and adults. However, C virus remained in Drosophila tissues even after host metamorphosis and would seem to interact with Drosophila cells. Hypotheses are proposed concerning the intracellular state of Drosophila C virus in this case.     

The I Domain is Essential for Echovirus 1 Interaction with VLA-2

VLA-2, the α2β1 integrin, mediates cell adhesion to collagen and laminin, and is the receptor for the human pathogen echovirus 1. Because of its similarity to domains present in other proteins that interact with collagen, a 191 amino acid region within the α2 subunit (the I domain) has been proposed as a potential site for ligand interactions. Although the α2 subunits of human and murine VLA-2 are 84% identical, human α2 promotes virus binding whereas murine α2 does not. We used murine/human chimeric α2 molecules to identify regions of the human molecule essential for virus binding. Virus bound efficiently to a chimeric protein in which the human I domain was inserted into murine α2, indicating that the human I domain is responsible for specific virus interactions. Monoclonal antibodies that inhibited virus attachment all recognized epitopes within the human I do-main, further suggesting that virus interacts with this portion of the molecule. Similarly, antibodies that prevented VLA-2-mediated cell adhesion to collagen also mapped to the I domain. These results indicate that the I domain plays a role in VLA-2 interactions both with virus and with extracellular matrix ligands.     

小RNA病毒和小DNA病毒的三维结构模型

本文综述了小RNA病毒和小DNA病毒的主要结构特征,绘制出了它们的三维结构模型,从中找出了两者间的共同点和差异,为进一步研究两种病毒提供了依据。     

Comparison of the three-dimensional structure of two human rhinoviruses (HRV2 and HRV14)

An attempt has been made to build a model of human rhinovirus 2 (HRV2) based on the known human rhinovirus 14 (HRV14) structure. HRV2 was selected because its amino acid sequence is known and because it belongs to the minor rhinovirus receptor class as compared to HRV14, which belongs to the major class. Initial alignment of HRV2 with HRV14 based on the primary sequence and the knowledge of the three-dimensional structure of HRV14 showed that the most probable position of the majority of insertions and deletions occurred in the vicinity of the neutralizing immunogenic sites (NIm). Out of a total of 855 amino acids present in one copy of each of the capsid proteins VP1 through VP4 of HRV14, 411 are different between the two viruses. There are also 6 amino acid residues inserted and 14 residues deleted in HRV2 relative to HRV14. Examination of amino acid interactions showed several cases of conservation of function, e.g., salt bridges or the filling of restricted space. The largest variation amongst the residues lining the canyon, the putative receptor binding site, was in the carboxy-terminal residues of VP1.     

昆虫小RNA病毒研究进展

昆虫小RNA病毒依据基因组结构特点分为家蚕软化病毒组、蟋蟀痹病毒组和豌豆蚜病毒组。昆虫小RNA病毒蛋白质翻译具有独特性：不依赖于帽子结构,不需要启始因子eIF1、eIF1A和帽子结合蛋白eIF4E;而且蟋蟀痹病毒组和豌豆蚜病毒组结构蛋白翻译从内部核糖体进入位点独立启始,启始密码子是CUU。该文还简介了昆虫小RNA病毒复制机理及与其它动、植物小RNA病毒或类小RNA病毒的亲缘关系等的研究进展。     

空气净化消毒技术现状与展望

随着人民生活水平的不断提高,创造仅仅具有适宜温度、湿度的舒适性空气环境已不能满足人们生活的需要,健康清洁的空气质量开始成为大众关注的热点。近年来,新型冠状病毒肆虐全球,气溶胶传播作为感染途径之一理应得到足够的重视。空气净化消毒技术对于防止细菌、病毒等病原体的扩散传播具有切实重要的意义。本文主要对多种物理类及化学类空气净化消毒技术进行详细的归纳介绍,分析这些技术在研究及应用中存在的问题,总结未来理想的空气净化消毒技术应当具备的特点。