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Allgemeine Virologie I Introduction in Virology History January 1796 vaccination against smallpox virus Virus • Definition of virus • Basic properties of viruses • Morphology – Structures of virues • Replication • Classification Bacteriophage Basic Virology Effect of viral replication CPE – Pathogenesis • Diseases • Immune response/ Immunopathogenesis • Diagnostic • Therapy • Prevention Medical Virology
1796 E. Jenner Vaccination against smallpox
Edward Jenner (1749-1823): European governments have officially encouraged or compelled the practise; and smallpox has ceased to be the almost universal scourge it was before Jenner's discovery. Modern History Sourcebook
Early Development of Virology • 1892:Dimitri Ivanowski • the causative agent of tobacco mosaic diseasewould pass through filters designed to remove bacteria • 1896: Beigerink---virus
Consequences of Viral Infections • Persistent disease • Fatal disease • Congenital disease • Contributory factor in cancer Some are asymptomatic!
WHAT ARE VIRUSES ? “A PIECE OFBAD NEWSWRAPPED UP IN A PROTEIN”
Virus 1. smallest infectious agents 2. one kind of nucleic acid (RNA or DNA) 3. intracellular parasites 4. assembly of the individual components 5. not usually respond to antibiotics
Size and Shape Virion: the complete fully assembled virus, serves to transfer the viral nucleic acid Range: from 20nm to 300nm in diameter Shapes: spheres, rods, bullets, bricks, tadpoles
Size & Shape • Virion : A complete infectious particle of virus • 20 nm ~ 300nm • spheres, rods, bullets or bricks • electron microscope, EM
A、Bacteriophage ( 65 ×95nm ) B、Adenovirus (70nm ) Chlamydia 390nm Rickettsia 450nm C、Poliovirus (30nm ) G A S.aureus (1000nm） D、JEV ( 40nm ) F Cowpox 300×250nm E、Protein (10nm ) B E C F、Influenza virus ( 100nm ) D G、TMV
Viral Structure nucleocapsid (naked virus) nucleic acid enveloped virus capsid envelope
peplomere/spike envelope enveloped virus capsomere capsid nucleocapsid(naked virus) nucleic acid Viral Structure
Virion structure • Core • Capsid • Envelop
A. Core • The core consists of a nucleic acid genome. • The genome of the virus consists of either DNA or RNA. Function: It provide the information of reproduction, heredity and mutation.
B. Capsid • The nucleic acid is surrounded by a protein coat called capsid, made up of subunits called capsomers. • The arrangement of capsomers gives the virus structure its geometric symmetry. • Three forms of symmetry in virus capsid: icosahedral, helical, complex forms
Icosahedral Symmetry • 20 equilateral triangle faces • 12 vertices
helical Tobacco Mosaic Virus nucleic acid protein
Complex Symmetry POXVIRUS FAMILY
The functions of capsid: • protect the genetic material • mediate the attachment of the virus to specific receptors on the host cell surface • important antigens -- The host’s defense mechanisms (cellular or humoral) are directed against the viral antigenic epitopes.
C.Envelope • The envelope is a lipoprotein membrane composed of lipid derived from the host cell membrane. • There are frequently glycoprotein in the form of spike on the surface, which attach to host cell receptors during the entry of the virus into the cell. • The envelope glycoprotein are also the principal antigens.
Chemical Composition  Viral protein  Viral nucleic acid  Viral lipid  Viral glycoprotein
 Viral protein 1.The structural proteins of viruses: (1) Capsid protein (2) Basic core protein These proteins are necessary to package the nucleic acid within the capsid !
2. The non-structural proteins The non-structural proteins are other proteins such as enzymes that are needed for the production of viral components but are not part of the virion.
Viral protein function: 1. Protect the nucleic acid 2. Take part in infection 3. Antigen
 Viral nucleic acid • Viruses contain a single kind of nucleic acid, either DNA or RNA that encodes the genetic information necessary for replication of the virus. • The genome may be single-stranded or double-stranded, circular or linear, and segmented or non-segmented.
Six different classes can be distinguished, based on mechanisms of transcription. 1. +-dsDNA 2.+ssDNA 3. +- dsRNA 4.+ssRNA 5.–ssRNA 6.Retroviruses +ssRNA
The type of nucleic acid, its strandedness, and its size are mayjor characteristics used for classifying viruses into families. • The size of the DNA genome ranges from 3.2Kbp (hepadnaviruses) to 375Kbp (poxviruses). • The size of the viral RNA genome range from about 7Kb (picornaviruses) to 30Kb (coronaviruses).
 Viral lipid • A number of different viruses contain lipid envelope as part of their structure. • The lipid is acquired when the viral nucleocapsid buds through a cellular membrane in the course of maturation.
 Viral glycoprotein • Viral envelope contain glycoprotein, and they are virus- encoded. • It is the surface glycoprotein of an enveloped virus that attach the virus particle to a target cell by interacting with a cellular receptor. • They are also important viral antigens.
Glycoprotein Spikes mediate the attachment of the virus to specific receptors on the host cell surface important antigens
Summary • Virion: fully assembled virus • Structure: core; capsid; envelop • Chemical composition: viral protein; nucleic acid; lipid; glycoprotein