Virology-To Students病毒学

,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,1,VIROLOGY,Yingchun Hou, M.D., Ph.D.,School of Life Sciences,Shaanxi Normal University,2,Introducing Myself,University Student:,Xian,Medical College,Master Degree:,Kunming,Medical College,Basic Medical Teacher: FMMU,Ph.D. Degree: FMMU,Physician (Internal Medicine) in Xi-,Jing,Hospital,Research Associate: Wayne State University,Postdoctoral Scholar: NIH,Postdoctoral Research Fellow: Wayne State University,Senior Scientist: VA Medical Center, Detroit, MI,Professor:,SNNU,3,Chapter 1: Virus and Virology,Virus:,Viruses belong to micro organism, but they are the most simple biological organism in the world that contain DNA or RNA core and protein coat or capsid only (Virion).,Viruses are so small that you can see them under a powerful microscope or electro microscope only.,The life cycle of viruses is very simple that shows virus replication only.,All of virus must survive in cells.,4,Most of viruses are very harmful to human being, animal, or plants. No any antibiotic is sensitive to virus so far. So, virus diseases are more threatened than other micro-organisms to human health.,Pseudovirus: Some “virus” contains DNA or RNA inside, but the DNA or RNA is from host. Pseudovirus can not be replicated, and it is not pathogen also.,Reverse transcript virus or DNA provirus: Some RNA virus can be reversely transcribed as cDNA, and the cDNA can combine into the genome of host.,Viroid: No coat or capsid, so, the nucleic acid is nude. Viroid is the pathogen to plants usually.,Phage: The virus parasites in bacteria only.,5,Virology and Its Importance to Us,Virology:,A academic field that includes the researches on virus and control the virus to protect human being and plant. Some time and for some virus, we can use the virus to make researches.,The roles of viruses to the development of life sciences:,Virus diseases, cardiovascular diseases, and cancers are the main killers to modern human being. Excepting that, virology is very important for the development of life sciences as the follows:,6,The Role of Animal Viruses in Understanding the Basic Outlines of Eukaryotic Gene Regulation:,The first transcriptional enhancer element (acts in an orientation- and distance-independent fashion) was described in the SV40 genome, as was a distance- and orientation-dependent promoter element observed with the same virus. The transcription factors that bind to the promoter, SP-1, or to the enhancer element, such as AP-1, AP-2, and which are essential to promote transcription along with the basal factors, were first described with SV40. Almost everything we know about the steps of messenger RNA (mRNA) processing began with observations made with viruses. For examples, RNA splicing of new transcripts was first described with the adenoviruses. The signal for,polyadenylation,in the mRNA was first found using SV40.,7,The cap and,methylation,of bases at the 5end of mRNA was first detected using,reoviruses,. The discovery of the role of interferon in inducing a set of gene products that act on translational regulatory events owes its origins to virology. Posttranslational processing of proteins by proteases, carbohydrate addition to proteins in the,Golgi,apparatus,phosphorylation,by a wide variety of important cellular protein,kinases, or the addition of fatty acids to membrane-associated proteins have all been profitably studied using viruses. Indeed, a good deal of our present-day knowledge in cell biology of how protein trafficking occurs and is regulated in cells comes from the use of virus-infected cell systems. Clearly, the field of gene regulation has relied on virology for many of its central tenets.,8,The Role of Animal Viruses in the Recombinant DNA Revolution:,The discovery of the enzyme reverse transcriptase in retroviruses (5,138) not only,helped to prove how retroviruses replicate but also provided an essential tool to produce complementary,DNAs,(,cDNAs,). The first restriction enzyme map of a chromosome,HindII,plus III, was with SV40 DNA, and the first DNA to show,the specificity of a restriction enzyme was SV40 DNA with,EcoRI,. Some of,the earliest DNA cloning experiments used SV40 DNA into lambda, or human b-hemoglobin genes into SV40 DNA, to construct the first mammalian expression vectors. Indeed, a debate about these very experiments led to a temporary moratorium on all such recombinant experiments.,9,From the beginning, several animal viruses had been developed into expression vectors for foreign genes, including SV40, the retroviruses, the adenoviruses, and,adeno,-associated virus, which has the remarkable property of site preferential integration. Modern day strategies of gene therapy will surely rely on some of these recombinant viruses. The first,cDNA,cloning of hemoglobin sequences utilized lambda vectors for the cloning and replication of these mRNA copies. In a nice twist of events, the long-elusive hepatitis virus C (non-A, non-B) was cloned from serum using recombinant DNA techniques, reverse transcriptase, and lambda phage vectors.,10,The Role of Animal Virology in Oncology:,It is not too strong a statement to say that we owe a great proportion of our present understanding of the origins of human cancers to two major groups of animal viruses, the retroviruses and DNA tumor viruses. The,oncogenes,were first discovered and proven to exist in a virus and then in the host cell genome using,Rous,sarcoma virus. A wide variety of retroviruses have captured, altered, and delivered,oncogenes,to the virologists. The insertion of retroviruses into the genomes of cancerous cells also helped to locate additional,oncogenes,. The second group of genes that contribute to the origins of human cancers, the tumor suppressor genes, has been shown to be intimately associated with the,DNA tumor viruses.,11,Genetic alterations at the p53 locus are the single most common,mutations known to occur in human cancers (60% to 65% of the time). The p53 protein was first discovered in association with the SV40 large T-antigen . SV40, the human adenoviruses, and the human,papilloma,viruses all encode,oncogenes,that produce proteins that interact with and inactivate the functions of two tumor suppressor gene products, the retinoblastoma susceptibility gene product (,Rb,) and p53. The cellular,oncogenes,and the tumor suppressor genes in human cancers have been studied and understood most profitably using these viruses.,12,The viruses that cause cancers have provided some of the most extraordinary episodes in modern animal virology. The story of the Epstein-Barr virus and its role in several cancers, as well as in infectious mononucleosis, provides us with the best in detective story science. The story is not yet complete and many mysteries remain. Similarly, the identification of a new pathologic disease, adult T-cell leukemia, led to the isolation of a virus that causes the disease and the realization that this virus human T-cell leukemia virus (HTLV-1) had been found previously. Although this discovery provided the virus, there is yet to be a satisfactory explanation of how this virus contributes to adult T-cell leukemia.,13,Equally interesting is the road to the hepatitis B virus and,hepatocellular,carcinomas.,By 1967, S.,Krugman,and his colleagues had good evidence distinguishing between hepatitis A and B viruses, and in the same year B. Blumberg et al. detected the Australia antigen. Through a tortuous path, it eventually became clear that the Australia antigen was a diagnostic marker for hepatitis B. Although this freed the blood supply of this dangerous virus,Hilleman,at Merck, Sharp and,Dohme,and the Chiron Corporation (which later isolated the hepatitis C virus) went on to produce the first human vaccine that prevents hepatitis B infections and very likely,hepatocellular,carcinomas associated with chronic virus infections. The idea of a vaccine that can prevent cancer comes some 82 to 85 years after the first discoveries of tumor viruses. At present, in many countries, newborn infants have been inoculated to prevent hepatitis B infections. Based on the epidemiologic predictions, this vaccination program should result in significant reduction of liver cancer cases in 40 to 50 years from now.,14,Vaccines:,The Salk and then,Sabin,poliovirus vaccines were the first beneficial products of the,cell culture revolution. In the early 1950s in the United States, just before the,introduction of the Salk vaccine, about 21,000 cases of poliomyelitis were reported,annually. Today, the number is fewer than 10.,Among the most remarkable achievements of last century is the complete eradication of smallpox, a disease with a history of over 2,000 years. In 1966, the World Health Organization began a program to immunize all individuals who had come into contact with an infected person. This strategy, as opposed to trying to immunize an entire population (which simply was not possible), worked and, in October 1977, Ali,Maolin,of Somalia was the last person in the world to have a naturally occurring case of smallpox. Because smallpox has no animal reservoir and requires person-to-person contact for its spread, most scientists agree that we are free of this disease. What most scientists do not agree on is whether we should store smallpox virus samples as a reference for the future.,15,The viral vaccines used in the past have included live attenuated vaccines, killed,virus vaccines, and subunit vaccines. Both the killed virus vaccine (Salk) and the,recombinant subunit vaccine (hepatitis B, S antigen) were new to the modern era of,virology. In the future, we will see one virus (,vaccinia,virus) presenting the antigens of a different virus, the injection of DNA-encoding viral antigens, and the use of specific interleukins or hormones with vaccines to stimulate immunity at specific locations in the host and to elucidate specific immunoglobulin classes.,16,Chapter 2:,Taxology,of Virus,Classification principles:,Nucleic acid: DNA, RNA, Double chain, Single chain, Linear and loop, Ratio of G+C, etc.,Virus morphology: Shapes (Band-form or Spherical, etc),Structures,The sensitivity to fat solvents: Ether, Chloroform, etc.,The relation between the serum features and antigen.,The features in cell culturing.,The sensitivity to other physic or chemical effects: Acid, Hot, and Bivalent positive ion or Amphoteric ion.,Epidemic features: Host, Transmission way, Vectors, Clinic features.,17,Classification:,A coherent and workable system of classification, a taxonomy, is a critical component of the discipline of virology. However, the unique nature of viruses has defied the strict application of many of the traditional tools of taxonomy used in other disciplines of biology. Thus, scientists who concern themselves with global taxonomy of organisms have traditionally left the viruses scattered throughout the major kingdoms, reasoning that viruses have more in common with their individual hosts than they do with each other.,18,Usually, based on their hosts, you can call some viruses as animal viruses (associated with human health), plant viruses (Important to agriculture and national economy), insect viruses, avian viruses, bacterial viruses (phages), and others. Also, prokaryotic viruses (phages) and eukaryotic viruses can be often found in some books or papers. So far, more than 4,000 species of virus have be established in the world. All viruses are,taxologically,sorted into an internationally acceptable system named as International Virus,Taxological,System. This system is handled by ICTV (International Committee of Taxonomy of Virus). The ICTV is a committee of the Virology Division of the International Union of,Microbiological Societies. The objectives of the ICTV are to develop an internationally agreed-upon taxonomy and nomenclature for viruses, to maintain an index of virus names, and to,communicate the proceedings of the committee to the international community of virologists. The ICTV publishes an update of the taxonomy at approximately 3-year intervals.,19,The ICTV also supports a web site (http:/,www.ncbi.nlm.nih.gov,/ICTV/), which contains all its published information in a conveniently interactive format, plus links to additional sites of interest, including the universal virus database of the ICTV (,ICTVdB,).,If you want to learn the detailed information about the system, the following websites are available for that:,http:/,life.anu.edu.au/viruses/welcome.htm,http:/,www.res.bbsrc.ac.uk/mirror/auz/welcome.htm,http:/,www.ncbi.nlm.nih.gov/ICTVdB/welcome.htm,Most important, the virus taxonomy that has been developed works well. For the,trained virologist, the mention of a virus family or genus name, such as family,Herpesviridae,or genus,Rotavirus, immediately conjures forth a set of characteristics that form the basis for further discussion or description. Virus taxonomy serves an important practical purpose as well, in that the identification of a limited number of biologic characteristics, such as,virion,morphology, genome structure, or antigenic properties, quickly provides a focus for identification of an unknown agent for the clinician or epidemiologist and can significantly impact further investigation into treatment or prevention of a virus disease.,20,Virus Properties and Their Use in Taxonomy:,The taxonomic method adopted for use in virology is,polythetic, meaning that any given virus group is described using a collection of individual properties. The description of a virus group is nonsystematic in that there exists no fixed list of properties that must be considered for all viruses, and no strict formula for the ordered consideration of properties. Instead, a set of properties describing a given virus is simply compared with other viruses described in a similar fashion to formulate rational groupings. Dozens of properties can be listed for description of a virus, but they break down generally into,virion,morphology, including size, shape,capsid,symmetry, and presence or absence of an envelope,virion,physical properties, including genome structure, sensitivity to physical or chemical insults; specific features of viral lipids, carbohydrates, and structural and nonstructural proteins; antigenic properties; and biologic properties including replication strategy, host range, mode of transmission, and,pathogenicity,.,21,The Hierarchy:,The ICTV has adopted a universal classification scheme that employs the hierarchical levels of order, family, subfamily, genus, and species. Because the,polythetic,approach to classification introduces viruses into the middle of the hierarchy, and because the ICTV has taken a relatively conservative approach to grouping,taxa, levels higher than order are not currently used. Levels lower than species, such as strains and variants, are not officially considered by the ICTV but are left to specialty groups.,22,Chapter 3: Structures and Life Cycle,I. Structures:,23,24,25,Shapes and Size of Virus:,The main shapes of virus are as the follows:,1. Spheroid or globoid virus with or without envelope. The number of virus member in this shape is biggest. Usually, they host in human being or animal.,2. Band or rod form virus. Usually, host in plants or insects.,3. Brick form virus. Brick form viruses are biggest and most complex viruses. Usually, host in human being or animal.,4. Virus with a globoid head and a rod tail. Usually, host in bacteria, and we give them a different name: Phage.,5. Insect viruses inside inclusion body. One inclusion body contain many virus particles inside.,26,Virus size,is very different between viruses from hundreds nm to ten more nm. So, usually, we use electron microscope to check or make observation on virus particles.,You have to remember the follows in your mind:,1. The resolving power of an optical microscope,= 0.25,m (250nm or 2500),2. The resolving power of an electron microscope,= 2.5,3. The diameter of a RBC = 8,m, The diameter of a,DNA double chain helix = 20, The diameter of an,-helix = 10, The diameter of an atom = 2 - 3.,27,Virus Life Cycle:,Viruses have to parasite in an alive cell to survive and replicate because they are so simple that they have no any basic structure to survive independently.,Replicative,Cycle:,Adsorption to cell,Invasion into cell Remove their envelope or coat Synthesize their DNA or RNA with nucleotides from host Assemble a new virus particle with the protein and others from host Release themselves from the hosted cell to out Another adsorption to a new cell,28,How to culture and amplify virus?,Bacterial culture for phage:,E. coli,strains and Plaque.,Cell culture for human or animal virus:,Cell culture technology.,Protoplasm culture for plant virus:,Protoplasm:,Plant cell Remove away the shell or wall Remained part can be cultured and grow up.,29,Adsorption to cell:,1.,Virus Surface Adsorption Protein:,The property and the electrostatic charge can affect or decide the combination of virus and cell. But, the combination mediated by electrostatic charge is reversible usually. I want to you know gp120 for HIV at least.,2.,Virus Receptor on Cell Surface:,The receptor can be recognized by virus adsorption protein. Receptor is very important to the host and tissue specificity, and the diseases caused by virus.,3.,Temperature, Concentration of ion, and pH,can put effects on the electrostatic charge and the mobility of cells and virus. So, their changes will result in the virus adsorption and invasion.,30,Invasion (Penetration, Insert) into cell:,1.,Invasion of phages:,(1),Injection with anal filament, and,(2),infect bacteria with sex,fimbria,.,(1),(2),31,2.,Invasion of animal viruses:,(1),Endocytosis, (2) Fusion (Envelope and Membrane), (3) Translocation.,(1),(2),(3),32,Remove their envelope and coat (Uncoating) or capsid:,Cell,Bacterium,33,3.,Invasion of plant viruses:,Plant viruses can not infect plant by themselves because the hard cell wall. They invade plant by other vectors, for example, grafting, pollen grain.,34,Synthesize their DNA or RNA with nucleotides from hosted cells:,A.,Combine into genome of host cell as,provirus,The futures of,a virus in cell,B.,Synthesize new virus particles with,the material resource from host cell,35,Assemble a new virus particle with the protein and others from hosted cells:,After the synthesize of a complete molecule was finished, the molecule is not a complete virus yet. It has to be assembled with capsid or coat to form a virus that can infect another cell.,1.,Phage:,Base-plate Caudal tube & sheath Head Caudal part Anal filament Hosted cell is broken,Viruses are released out,(For many detailed steps, you can read them but I don not want to you remember them in mind),36,2.,Animal Virus:,Capsid (Protein from cell nuclei membrane or cell membrane) Capsid combine to DNA/RNA Envelope (Protein is from cell nuclei membrane, plasma or cell membrane. Some viruses have no envelope),Virus is released out by some special tunnel or transportation structure on cell membrane or cell breakage.,37,3.,Plant virus:,Most of plant viruses have no envelope, so, they are more simple than animal viruses.,Capsid is formed automatically. Plant viruses do not break cell to release out usually. Plant viruses can transmit to other cells by filament between cells.,38,Host Cell,Paras