医学微生物学英文版教学课件：第21章病毒的基本形状--（7年制）

1、 Part II virology 医学微生物学教研室 周亚滨 手足口感流典 非 艾滋病人类免疫缺陷病毒SARS病毒流感病毒柯萨奇病毒 乙型肝炎乙型肝炎病毒寨卡病毒埃博拉病毒麻疹病毒 Virus 1.small size: 20 300 nm, most were too small to be seen with the light microscope , filtrable. 2. simple structure: non-cellular entity, contain only one kind of nucleic acid (DNA or RNA) and protein. 3

2、. obligate intracellular parasites: they replicate only in the living cells. 4. self-replication ：in vivo 5. resistant to many antibioticsacellular microorganism General Propertiesof VirusChapter 21Section 1 Size Structure Chemical Composition Size and Shape of VirusVirion The complete virus particl

3、e. The basic infectious particle of a virus is known as the virion. The virion is composed of the nucleic acid genome, structural protein and in some viruses an enclosing lipid-containing envelope. size- measure unit： nm (nanometer) 20 -300 nm Shape spherical rodlikebrickbullet tadpole(filamentous)埃

4、博拉病毒狂犬病毒脊髓灰质炎病毒乙型肝炎病毒流感病毒人类免疫缺陷病毒Structure and Chemical Composition of VirusI. Structure of Virusvirion naked virusenveloped virusnucleocapsidcorecapsidenvelope(spike)capsidcoreenvelopenaked virusenveloped virusspikecapsomere (morphologic subunit)pentonhexonicosahedral symmetryEnveloped VirusNaked V

5、irusCubicHelicalHIVInfluenza virusspike1. Viral nucleic acid Composition: DNA or RNA size:3.2kp-375kb diversity: single-stranded(ss) / double-stranded(ds) circular / linear segmented / nonsegmented RNA: +RNA / -RNA II. Composition and function of virus Function: #encodes the genetic information nece

6、ssary for replication, infection, heredity and variation of the virus. #infectivity-infectious nucleic acid infectious nucleic acid some viral nucleic acid which can enter cells and reproduce new viruses. DNA virus（dsDNA, ssDNA） RNA virus (+ssRNA) 2. Viral protein structural protein: The protein whi

7、ch is the composition of virion . distribution: capsid; envelope; matrix. function: protect the viral genome provide the structure symmetry of virus determine the antigenic characteristics of virus determine the attachment of virus to the cell (viral attachment proteins，VAP) non-structural protein C

8、ode by virus; it is not the composition of virion. distribution: virion and/or infected cell. function : essential for viral replication -viral enzymes in virion influenzavirus: RNA-dependent RNA polymerase HIV: reverse transcriptase in host proteolytic enzyme; DNA polymerase; regulatory protein. in

9、terference the biosynthesis of host cell specific viral protein-in infected cell transformation protein of tumor virus. RNA-dependent RNA polymerasereverse transcriptase 3.lipid and carbohydrate distribution: envelope function: strengthening the structure of virion the viral infection-fusion virus-c

10、ell cell-cell lipid-containing viruses are sensitive to treatment with ether and other lipid solvents. derived from the host cellstructure composition function core nucleic acid replication of virus （DNA or RNA) encodes genetic information ( sequence/segment ) (double/single ) （ infectious nucleic a

11、cid ） protect nucleic acid capsid protein antigenicity specific binding sites (VAP ) envelope glycoprotein, lipid antigenicity keep the shape of virion fusion spike specific binding sites (VAP ) Section 3Viral Multiplication Replication The process of intracellular viral multiplication, consisting o

12、f the synthesis of proteins and nucleic acid of virus and assembly into a new infectious particle. Replication cycle adsorptionpenetrationuncoatingbiosynthesisassemblymaturation and release adsorption interaction between specific binding sites on viral capsid (or envelope) and specific receptors on

13、host cell surface.virushostvirus virus enter the cells. naked viruses: endocytosis enveloped virus : membranes fusion penetrationvirushostvirus hostvirushostinfluenza virus release the viral genome from nucleocapsid Lysosome enzyme uncoating Replication of viral nucleic acid Synthesis of viral prote

14、ins biosynthesisEarly biosynthesisLate biosynthesisnonstructural protein viral nucleic acid structural proteinThe type of viral biosynthesis ds DNA virusesss DNA viruses+ssRNA viruses-ssRNA virusesdsRNA virusesretrovirusesDNA virusesreplicate in the nucleususe the host cell DNA dependent RNA polymer

15、ase to synthesize their mRNAdsDNA viruses dsDNA mRNA(early) early protein dsDNA mRNA(later) later protein （structural protein）RNA polymerasetranslationtranslationtranscription（DNA polymerase ）transcriptionreplication Three kinds of RNA viruses: (1) plus-strand viruses :+ssRNA (2) minus-strand viruse

16、s: -ssRNA (3) retroviruses: ssRNA RNA viruses plus-strand RNA viruses (+ssRNA): +ssRNA -ssRNA （mRNA） +ssRNA -ssRNA early protein later protein +ssRNAtranslation（structural protein）replicationtranslationRNA polymerasereplicationreplication minus-strand viruses (-ssRNA): -ssRNA -ssRNA +ssRNA viral pro

17、tein -ssRNA (structural protein) (RNA polymerase)replication RNA polymerasetranslation replication Retrovirus: viral RNA reverse transcriptase RNA RNase H ssDNA DNA DNA polymerase host cell DNA dsDNA DNA insertion cyclizationintegrasereplicationRNAenzymolysisintegraseproteinnaked viruses - by lysis

18、of the host cell. enveloped viruses - by budding through cell membrane .assembly and release virus buddingOne-step multiplication curves of virus Unnormal multiplication 1.abortive infection： a virus infects a cell (non-permissive cell), but cannot complete the full replication cycle, i.e. a non-pro

19、ductive infection. non-permissive cell permissive cell 2.defective virus The virus that lacks one or more functional genes required for viral replication. Defective virus require helper activity from another virus for some step in replication or maturation. helper virus defective interfering particl

20、e (DIP) spontaneous deletion mutants may interfere with the replication of homologous virus. The DIP has lost essential segment of genome but contain normal capsid protein Interference Infection of either cell culture or host with two viruses often leads to an inhibition of multiplication of one of

21、the viruses. alive virusinactive virusalive virusinterferencedefective virus biosynthesisAssembly, maturation and releaseadsorptionpenetrationuncoatinginterferenceinterferenceinterferon# disturb adsorption# disturb biosynthesis# produce interferonSection 4 viral heredity and variation viral genome g

22、enetic substance: DNA; RNA mutation Mutation in viral DNA and RNA occur by the processes of base substitution, deletion and frame shift. Conditional-lethal mutant: these mutations function normally under permissive conditions but fail to replicate or to express the mutation gene under restrictive co

23、nditions. Temperature-sensitive mutant (ts) permissive temperature: 2835 non permissive temperature: 3740 Interaction of viral genetic material Recombination: the exchange of genes between two viruses which infected the same cell. ( active virus-active virus; active virus-inactive virus). genetic re

24、activation Reassortment exchange of genetic material between two segmented viruses which infected the same cell. Interaction of viral gene products Complementation： If we infect the same cell with two viruses, one or both of which may be defective, one virus provides a gene product in which the seco

25、nd is defective , allow the second virus to grow. The genotypes of the two viruses remain unchanged.defective virushelper virusdefective virus Phenotypic mixing: If two different viruses infect a cell, progeny viruses may contain coat components derived from both parents and so they will have coat p

26、roperties of both parents.biosynthesisassemblyTRANSCAPSIDATIONPhenotypic maskingSection 5Effects of Physical and Chemical Agents on Viruses Inactivation : the virus lose their infections when they are affected by some factors, such as physical or chemical factors . lose their infections the virus ca

27、nnot produce infectious virion。 Resistance: low temperature： - 196 pH： 59 antibioticSensitivity： high temperature: 50 radiation and UV lipo-solvent : enveloped virus毛蚶甲型肝炎病毒 section 6 Classification Subvirus - unconventional agents refer to the kind of infectious factor which is smaller than virus. 1. satellites virus: RNA, protein. 2. viroid contain RNA only, cause plant disease 3. prion: protein Prion: are infectious particles that are composed solely of pr