Pentagon packing models for "all-pentamer" virus structures.

A connection is made between 1) the observed structures of virus capsids whose capsomers are all pentamers and 2) the mathematical problem of determination of the largest size of a given number of equal regular spherical pentagons that can be packed on the surface of the unit sphere without overlapping. It is found that papillomaviruses provide the conjectured solution to the spherical pentagon packing problem for 72 pentagons. Thus, a study of some virus structures has given additional insight into a mathematical problem. At the same time this mathematical problem enables prediction of an octahedral form of papillomavirus particles consisting of 24 pentamers. It is also found that the various tubular and spherical "all-pentamer" virus structures identified so far can be represented by closet-packing arrangements of equal morphological units composed of equal regular pentagons on a cylinder and on a sphere.     

Future virus problems?

Of seventeen viruses that infect British grasses several have been reported only recently; others that occur in Europe have hosts and vectors in Britain and could become a problem. Ryegrass bacilliform virus and ryegrass spherical virus are described and maize dwarf mosaic virus, maize rough dwarf virus and brome mosaic virus are considered as possible pathogens.     

Generation of a purely clonal defective interfering influenza virus

Defective interfering (DI) influenza viruses carry a large deletion in a gene segment that interferes with the replication of infectious virus; thus, such viruses have potential for antiviral therapy. However, because DI viruses cannot replicate autonomously without the aid of an infectious helper virus, clonal DI virus stocks that are not contaminated with helper virus have not yet been generated. To overcome this problem, we used reverse genetics to generate a clonal DI virus with a PB2 DI gene, amplified the clonal DI virus using a cell line stably expressing the PB2 protein, and confirmed its ability to interfere with infectious virus replication in vitro. Thus, our approach is suitable for obtaining purely clonal DI viruses, will contribute to the understanding of DI virus interference mechanisms and can be used to develop DI virus‐based antivirals.     

Honeybee viruses in Uruguay

Mortality of honeybees is a serious problem that beekeepers have to face periodically in Uruguay and worldwide. The presence of RNA viruses, in addition to other pathogens may be one of its possible causes. In this work, we detected Chronic bee paralysis virus, Acute bee paralysis virus, Black queen cell virus, Sacbrood virus and Deformed wing virus in samples of Uruguayan honeybees with or without Varroa destructor and Nosema apis. The detection of viruses in different provinces, simultaneous co-infection of colonies by several viruses and the fact that 96% of the samples were infected with one or more virus, indicates they are widely spread in the region.     

Genetic control of virus production in cell lines

A procedure to maintain genetic control of virus production in tissue cell lines, has been proposed and discussed. Both the tissue cell which replicates the virus and the virus inoculum must be homogeneous in order to produce a product with the expected characteristics. Certain philosophical and technical aspects of the problem are discussed in relation to developing and maintaining genetically homogeneous stock cultures, inoculum, and product.     

Electron Microscopic Study of the Development of Simian Virus 40 by Use of Ferritinlabeled Antibodies

An electron microscopic study of simian virus 40 has revealed a number of structural changes that are related to the development of the virus. The presence of viral antigens in both the nucleus and the cytoplasm has been demonstrated by means of ferritin-labeled antibodies. Although cytoplasmic virions are readily tagged, the lack of tagging of nuclear particles presents a perplexing problem. Presumably, the virus, after release from the nucleus, acquires a new antigenic reactivity in the cytoplasm.     

植物抗病毒基因工程研究进展

病毒作为一种依赖于宿主细胞代谢的病原体对全球农业造成了重大经济损失。虽然目前已利用多种防治策略来控制病毒病,例如培育抗病毒品种、使用化学杀菌剂、切断病毒的感染途径、组织脱毒、传统农业防治等,但都无法从根本上控制病毒病的危害。近年来的研究表明,基因工程手段能够有效对抗植物病毒病害。本文综述了基因工程手段改造植物抗病毒能力的技术和方法。     

Exotic viral diseases

Marburg virus disease, Lassa fever, monkeypox, and Ebola virus diseases of humans have all been recognized since 1967. These are examples of some of the exotic virus diseases which through importation may present a potential public health problem in the United States. Some of these viruses are also highly hazardous to laboratory and medical personnel. This paper is a review of the general characteristics, the epidemiology, and laboratory diagnosis of the exotic viruses which have been described during the last 25 years.     

Cross-protection of mice against a global spectrum of rabies virus variants.

Rabies, a continuing worldwide problem, kills tens of thousands of people and millions of animals each year. The problem is most severe in developing countries, where cell culture-derived vaccines are unaffordable and the available nervous tissue-derived vaccines are often of questionable immunogenicity and may produce neurological complications. To determine the feasibility of developing a vaccine with worldwide applicability, we investigated whether recombinant vaccinia viruses expressing either the glycoprotein (G), the nucleoprotein (N), or both the G and N (GN) of the challenge virus strain (CVS) of rabies virus would cross-protect mice against 17 rabies virus isolates representing the spectrum of rabies virus variants found worldwide. The results were compared with the commercially available human diploid cell vaccine (HDCV). Among mice injected with any of the 17 viruses, > or = 95% were protected by vaccination with recombinant viruses expressing G or GN, and > or = 85% of the mice were protected by the HDCV. The recombinant virus expressing N was less protective, protecting against only 11 of the 17 viruses. Antibody prepared against the G of the strains used in the vaccines neutralized all 17 viruses, and sera from mice infected with any one virus variant cross-neutralized all of the other viruses. Thus, no antigenic differences that would potentiate vaccine failures were identified. These studies suggest that a single rabies virus strain or its G would protect globally against wild-type rabies viruses.     

甲型流感病毒RNA聚合酶——抗病毒药物靶点

甲型流感病毒的RNA聚合酶由PB1、PB2和PA 三个亚基组成,在病毒的生命周期中负责行使病毒基因组的转录与复制等多方面功能. 甲型流感病毒由于频繁变异,导致其对传统抗病毒药物的敏感性降低,因此开发疗效好、针对性强、毒性低的新型抗病毒药物已成为当前亟待解决的问题.由于RNA聚合酶是甲型流感病毒生命周期重要的调控蛋白,并且编码聚合酶各亚基的基因序列具有高度保守性,故成为当前抗病毒药物的重要靶点.     

Influenza-virus-induced signaling cascades: targets for antiviral therapy?

Influenza viruses continue to pose a severe threat worldwide, causing thousands of deaths and an enormous economic loss every year. The major problem in fighting influenza is the high genetic variability of the virus, resulting in the rapid formation of variants that escape the acquired immunity against previous virus strains, or have resistance to antiviral agents. Every virus depends on its host cell and, hence, cellular functions that are essential for viral replication might be suitable targets for antiviral therapy. As a result, intracellular signaling cascades induced by the virus, in particular mitogen-activated protein kinase pathways, have recently come into focus.     

Infection of Cattle with Parainfluenza 3 Virus with Special Reference to Udder Infection

Thirty-seven strains of parainfluenza 3 virus were isolated on bovine kidney cell cultures from Japanese cattle in herds suffering from acute respiratory illness. This finding, together with the clinical and epidemiologic observations and the results of a serologic survey, indicates that in Japan, as in the United States and other countries, this virus is one of the important causes of acute respiratory disease in cattle. A significant finding in the present study is that virus was recovered from milk as well as from nasal secretions. This finding suggests an important role for milk, along with nasal discharges, in disseminating the virus among cattle. In addition, the recovery of virus from milk presents a new problem concerning this infection in cattle, in particular, the potential role of this virus in the pathogenesis of mastitis.     

Reconcentration of poliovirus from sewage.

Virus can be adsorbed from effluents of sewage treatment plants on large-surface membranes. Subsequent elution of virus requires large volumes, which in turn requires reconcentration of virus for assay. However, reconcentration of such viral eluates on small adsorbent surfaces is difficult because certain soluble sewage components are adsorbed along with the virus on the initial virus adsorbent and are removed along with the virus by the eluent. Upon acidification of the initial eluate to reconcentrate the virus on smaller membrane surfaces, flocs are formed that interfere with the reconcentration process. To circumvent this problem, the interfering sewage components can be removed by activated carbon and ion-exchange resins. The virus is then readily reconcentrated on small membranes.     

Reconcentration of poliovirus from sewage.

Virus can be adsorbed from effluents of sewage treatment plants on large-surface membranes. Subsequent elution of virus requires large volumes, which in turn requires reconcentration of virus for assay. However, reconcentration of such viral eluates on small adsorbent surfaces is difficult because certain soluble sewage components are adsorbed along with the virus on the initial virus adsorbent and are removed along with the virus by the eluent. Upon acidification of the initial eluate to reconcentrate the virus on smaller membrane surfaces, flocs are formed that interfere with the reconcentration process. To circumvent this problem, the interfering sewage components can be removed by activated carbon and ion-exchange resins. The virus is then readily reconcentrated on small membranes.     

Role of Cellular DNA Repair Systems in HIV-1 Replication

Molecular Biology - A serious problem in the treatment of HIV infection is the emergence of drug-resistant forms of the virus. One promising approach to solving this problem is the development of...     

Attenuated modified vaccinia virus Ankara can be used as an immunizing agent under conditions of preexisting immunity to the vector

A problem associated with the use of vaccinia virus recombinants as vaccines is the existence of a large human population with preexisting immunity to the vector. Here we showed that after a booster with attenuated recombinant modified vaccinia virus Ankara (rMVA), higher humoral and cellular immune responses to foreign antigens (human immunodeficiency virus type 1 Env and beta-galactosidase) were found in mice preimmunized with rMVA than in mice primed with the virulent Western Reserve strain and boosted with rMVA. This enhancement correlated with higher levels of expression of foreign antigens after the booster.     

抗乙型肝炎病毒的天然药物研究

如何从丰富的天然生物中筛选具有抗乙型肝炎病毒活性的药物 ,并且研究它们的作用机理 ,寻找特异性强、毒副作用小的药物 ,是我国中药现代化的一个重要研究方向。本文综述了近年来中草药和一些重要的天然化合物抗乙型肝炎病毒的作用机理以及体内外研究和临床应用 ,并提出了在抗乙型肝炎病毒药物筛选中存在的一些问题     

Single-chain antibodies against a plant viral RNA-dependent RNA polymerase confer virus resistance

Crop loss due to viral diseases is still a major problem for agriculture today. We present a strategy to achieve virus resistance based on the expression of single-chain Fv fragments (scFvs) against a conserved domain in a plant viral RNA-dependent RNA polymerase (RdRp), a key enzyme in virus replication. The selected scFvs inhibited complementary RNA synthesis of different plant virus RdRps in vitro and virus replication in planta. Moreover, the scFvs also bound to the RdRp of the distantly related hepatitis C virus. T(1) and T(2) progeny of transgenic lines of Nicotiana benthamiana expressing different scFvs either in the cytosol or in the endoplasmic reticulum showed varying degrees of resistance against four plant viruses from different genera, three of which belong to the Tombusviridae family. Virus resistance based on antibodies to RdRps adds another tool to the repertoire for combating plant viruses.     

Tulane Virus as a Potential Surrogate To Mimic Norovirus Behavior in Oysters

Oyster contamination by noroviruses is an important health and economic problem. The present study aimed to compare the behaviors of Norwalk virus (the prototype genogroup I norovirus) and two culturable viruses: Tulane virus and mengovirus. After bioaccumulation, tissue distributions were quite similar for Norwalk virus and Tulane virus, with the majority of viral particles detected in digestive tissues, while mengovirus was detected in large amounts in the gills and mantle as well as in digestive tissues. The levels of persistence of all three viruses over 8 days were comparable, but clear differences were observed over longer periods, with Norwalk and Tulane viruses displaying rather similar half-lives, unlike mengovirus, which was cleared more rapidly. These results indicate that Tulane virus may be a good surrogate for studying norovirus behavior in oysters, and they confirm the prolonged persistence of Norwalk virus in oyster tissues.     

Hepatitis C--new developments in the studies of the viral life cycle

Hepatitis C virus (HCV) is a causative agent of chronic liver disease leading to cirrhosis, liver failure and hepatocellular carcinoma. The prevalence of HCV is estimated as 3% of the world population and the virus is a major public health problem all over the world. For over 16 years, since HCV had been discovered, studies of the mechanisms of the viral life cycle and virus-host interactions have been hampered by the lack of a cell culture system allowing the virus to be grown in laboratory conditions. However, in recent years some new model systems to study HCV have been developed. The major breakthrough of the last two years was the cell culture system for maintaining the virus in an adapted hepatocyte-derived cell line. This review describes the techniques and applications of most of the in vitro systems and animal models currently used for working with hepatitis C virus.