New Employee Orientation

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Virology
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Introduction

• 1.The discovery of virus
• 2.Feature and conception of virus
• 3.Relationship between viruses and diseases of
  human being

1892? ???????---??????
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2.Feature and conception of virus
?Feature
DNA or RNA non-cellural type
???? ???? ???? ????
multiply only in living and susceptible cells
?The most important difference between viruses
and other microbes
RNA or DNA mode of multiplication --- self
replication
?Conception
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3. Relationship between viruses and
diseases of human being
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(6?p2231)
Basic Properties of Viruses
???????
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Outline
(6?p2231,8183)

• Size and Shape of Viruses
• Structure and Chemical Composition
• Multiplication of Viruses
• Effect of physicochemical agents on virus
• Classification of Viruses
• Viral Heredity Variation (p8183)

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?.Size and Shape of Viruses
1.Size of virus
? Measuring unit (nanometer,nm) d30300 nm
visible only with EM
???390nm
????450nm
6595nm
15300nm
???
??????
????
?Divide into 3 types ---small ,median and
large virus (???lt150nm)
1000nm
100nm
70nm
????
300250nm

????
???
10nm
30nm
40nm
????

????
2. Shape of viruses
????
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2. Shape of viruses
??
200300nm
????
???
???
50200nm
??
???
?
lt50nm
????????
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1.Structure of virion
?.Structure and Chemical Composition
?????????? ???????
peplomer (spike)
Enveloped virus
envelope
capsid
viral core
nucleocapsid
(Naked virus)
nucleic acid
capsomere
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? Viral core---viral nucleic acid
? Only one type of nucleic acid

• either DNA or RNA
• diversity
• double or single stranded (ds-/ss-)
  
• circular or linear, in one piece or segmented
• plus and minus strand

(DNA????????,RNA ???????)
?Viral genome (DNA or RNA)
---determine infectivity, replication,
heredity and variation of virus
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? Protein coat----capsid(??)
?Consists of repeating polypeptide subunits
called capsomere(??) ?
Symmetry in arrangement
?three symmetric architecture
? Function
protect
participate in viral infection antigenicity
Helical symmetry
(????????,??????????)

Complex symmetry
Structure of the simplest virion Nucleic acid
capsid Nucleocapsid
???
???
(???)
Cubic symmetry
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? Envelope and spike
Enveloped virus
(virion ? nucleocapsidenvelope)
Composition of envelope
Peplomer or spike
(???? ??)
Function
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??????
??? (????)
???
???
???
??
capsid

??
DNA/RNA
(???)
??
?? ??
??
(DNA/RNA)
??
????
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2. Chemical composition
of viruses
? Nucleic acid
? Protein

• ? structural protein
• ? non-structural protein

(capsid,matrix and envelope)
? lipid and carbohydrate
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?. Multiplication of Virus
1.Multiplication of virus
?Mode of multiplication
--- self -replication
? Replicative cycle
????
?adsorption/attachment ? ?penetration
? ?uncoating ? ?biosynthesis
? ?assembly release
???????
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?Adsorption or attachment
Nonspecific adsorption Specific combination
---static electricity-combination between virus
and cell

---virion adsorb to specific receptor on the
surface of susceptible cells
(decide tissue or cell-tropism, such as gp120 of
HIV---CD4 molecule)
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?Uncoating
?Penetration
(?????)
naked virus---by endocytosis or viropexis
enveloped virus---by fusion of viral
envelope with host-cell membrane
(????????????)
---The viral nuclei acid is
released from the capsid
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?Biosynthesis
(eclipse period,???)
include replication of nucleic acid and
protein synthesis
biosynthetic site
DNA in the nucleus, RNA in the cytoplasm
protein in the cytoplasm
early protein (function protein) late
protein (structural protein)
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Biosynthesis of ds-DNA virus
??????DNA ?RNA?????

parental ds-DNA
early mRNA

?

in nucleus

in the cytoplasm
?
DNA???
?????

early protein

progeny ds-DNA
later mRNA

?
in the cytoplasm

later protein
?biosynthesis of early protein---??DNA?DNA????
?replication of progeny DNA
?biosynthesis of late protein
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Biosynthesis of ss-RNA virus
acts directly as mRNA
parental ?ss-RNA
early protein
in the cytoplasm
(??RNA?RNA???)
later protein
RNA acts as mRNA
?ss-RNA(RNA)
(?????)
progeny ?ss-RNA
?ss-RNA virus
----RNA must first transcribe the
complementary plus strand
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?Assembly release
assembly and maturation
assembly DNA virus --- in the nucleus
RNA virus--- in the cytoplasm
release
naked virus
enveloped virus
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Replication cycle of virus
progeny viruses produce cell
effects---damage and lysis of cells
adsorption
assembly and release
penetration
uncoating
biosynthesis
protein and nucleic acid


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2. Abnormal multiplication of viral
interference

? Abortive infection (????)
non-permissive cells permissive cells(?????)
? Defective virus
? Interference

?????????????,????????????????????????
? defective interfering particle (DIP)

???????????(?????)?????????, ??????????,
??????????????????(DIP)

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?.Effect of physicochemical agents on virus



?????

???????
pH5.0???pH9.0 ??????


?????????????
?????? ??????????

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1.Basis of classification
p30
?. Classification of viruses

• ? Type structure of nucleic acid
• ? Structure of virus
  (envelope, symmetry)
• ? Size and shape of virus
• ? Sensitive to lipid solvent

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2.Categories of viruses
? DNA viruses
? RNA viruses
? DNA and RNA retroviruses
(??DNA??????????)
Subvirus

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Subvirus ---pathogenic agents of
unconventional virus (?????)
???????????????

?Viroids(???)
ss-RNA,possess no capsid or envelope cause
plant disease
?satellites (????) ??plant disease
can encode self-capsid protein
satellites RNA molecules (???????) (ssRNA
capsid protein from helper virus)

?prion(??) ---??????
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?Prion(??)/Virino(???)
( p335)
?possess no structure of virion and contain no
detectable nucleic acid in prions
?consist of prion protein
(PrP,???)
specific protein with infectivity

??????????,?prion,??????(PrP) encoded by gene of
normal host cells and no homology with normal
protein
?resistant to physical and chemical agents ? 2
isomer of PrP
(highly)
PrPc (cellular prion protein) PrPsc (scrapie
prion protein)
difference ?
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sensitive to proteinase K
resistant to proteinase K
PrPC ? PrPSC (?????????)

?Diseases asso-ciated with prions

• human disease
• common characteristics

(Kuru disease, CJD, vCJD ,etc.)
??????
---a fatal disease of CNS
??PrPSC????????????????????(????????????
?????)
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p81
?. Viral Heredity and Variation
1.Two important variations
? Variations in antigenicity ?
Variations in virulence
2.Gene mutation
3.Recombination reassortment
4.Gene integration
5.Phenotype variation

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2.Mutation

• ? Conception of mutant and variant
• ? Important mutant

??? ???
--- temperature sensitive mutant
(ts mutant)
??????(2835?)????,????????(3740?)???????
??????ts ???
ts ????????????????,??????????
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3.Gene recombination and reassortment

• ? Gene recombination (??)

(nonsegmented genome)
? Reassortment (??)

(segmented genome)
4.Gene integration
5.Phenotype variation

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Infection and Immunity of Viruses
????????
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Outline
?Pathogenesis of Viruses ?Modes of Viral
Transmission ?Types of Viral Infection ?Antivira
l Immunity
p4853
p6265
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?. Pathogenesis of Virus

• 1. Direct effects of viral infection on host cells

• Cytolytic infection (??????)

Infection of naked viruses ?cytocidal
effect
Mechanism of
cell death and lysis
??????????????? ???????????????? ??????????????

In vitro infection of cytocidal virus
?cytopathic effect (CPE,???????)
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Steady-state infection
(??????)
Infection of enveloped viruses
Change of cell membrane

• fusion of cells
  
• ?form multinucleated giant cells
• appearance of new antigen on
• the surface of host cells

(???????????)
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? Inclusion body formation (?????)
?????????????????
?Cell apoptosis(????)
?Gene Integration cell
transformation(?????????)
( Relationship between viruses and
cancers)
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2.Immunopathogenesis
of viral infection

• ? Immunopathogenesis mediated by Ab
• ?Immunopathogenesis mediated by cells
• ?Immunopathogenesis of autoimmunity

(Type ?,? hypersensitivity)
(type ? hypersensitivity)
(LSP?IR common Ag ? cross reaction)
3.Immune suppression
(suppression of immune function)
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?. Modes of Viral Transmission
1.horizontal transmission
??????????????????, ????????????
? conception ? portal of entry
skin
mucous membrane via blood
?? ???????????? ????????!
???????!
2.vertical transmission
(or perinatal transmission, ?????)

• ? conception
• ? portal of entry

?????????, ?????????????????,????????????
placenta vagina (???????????)

???????!
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?.Types of Viral Infection
Infection or disease
virus
host
target organ
portal of entry
spread to
1.Inapparent viral infection 2.Apparent viral
infection

IR
(?????,??????????????????)
????????? ????????????
? Acute viral infection
? Persistent viral
infection(?????)
??????
???/???????? ?????
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Persistent viral infection
chronic infection
????????????, ???????, ??? ? HBV
latent infection
???????????? ???????????????????
? HSV?VZV????
slow virus infection
?????, ???????????? ?? ?HIV ?AIDS
delayed complication after acute viral infection
?????, CNS??????,???????????? ??.???????????????(S
SPE)

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?.Antiviral Immunity (p6265)
1.Nonspecific immunity
(similar to antibacterial immunity)
?Barriers ?Effects of cells ?Antibacterial
substances in normal tissues and body fluide
(placenta barrier)
(M? , NK cell)
(IFN)
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Interferon (IFN)
? definition
???????????????????????????????????????????
?????????????
? types and properties
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? Mechanism of antiviral activity
IFN
AVP ?2-5 A synthetase ( 2-5 A ???) ?
protein kinase(????) ?phosphodiesterase (?????)
binds to surface receptor of an neighbouring cells
?????mRNA
induce
????????????
the synthesis of antiviral protein(AVP)
?????????
by blocking the translation of viral proteins
inhibit the replication of viruses
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? Feature of antiviral activity
inhibit replication of a variety of
viruses---broad spectrum indirect
effect species-specific
(???????,???????????)

(???????)

(??????)
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?Action of IFN in antiviral
immunity


----inhibit replication of virus
discontinue viral infection limit the spread
of virus and protect neighbouring cells
IFN
specific immunity
the bodys first-line defense against
viral infection
?????? ??????
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NK cell

• ?Killing virus-infected cells(natural killer
  activity)
• ?Mechanism of killing target cell

AM of NK cell binding to corresponding ligand
of target cell ?necrosis or
apoptosis of cells mediate
ADCC
release killer
madiator
??????
??????
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2.Specific immunity
induce
Viral protein
HI/CMI
(processing and presenting)

• ?Humoral immunity
  
• virus-neutralizing antibodies
• non-neutralizing antibody

neutralize infectivity of virus
types(IgG/IgM/sIgA) and mechanism
????????
???????????
hemagglutination inhibition Ab
?inhibit hemagglutination complement
fixation Ab?opsonization
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? Cell-mediated immunity
???????,??????

• Direct killing activity of CTL
• Antiviral effect of CD4Th1 cell

???????
??IFN-??TNF???????
?? IFN-??TNF??M? ?NK ?? ??CTL???
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3.Lasted time of immunity

• ? Transient immunity
• ? Long-lasting immunity (or
  lifelong immunity)

(????)
(?????????)
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6? p112
Detection, Prevention and Treatment of Viral
Infection
????????? ?????
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?.Diagnosis of Viral Infection
p112116

• 1.Collection and transport of specimens
• 2.Isolation and identifi-cation of viruses
• 3.Serological diagnosis of viral infection
• 4. Quick diagnosis

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1.Collection and transport
of specimens
(principles of collecting specimens)
? Specimens of viral isolation or detection
of viral nucleic acid ? Specimens of
serological tests
(in time,proper specimens and proper treatment)
Double-specimens of serum a single sample of
serum
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2.Isolation and identification of viruses
? Principles of viral culture
---multiply only in living and susceptible cells
? Three main methods

• animal inoculation
• embryonated eggs inoculation
• tissue or cell culture

(susceptible animal,proper route)
(sites of inoculation)
(types of cells---?????????????)
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? Isolation of virus
specimen
inoculate
(removing bacteria)
( into the susceptible host as soon as possible)
embryonated egg
animal inoculation
cell culture
preliminary diagnosis
serologic identification
??????????(???)
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Identification of the virus in cell culture
Produces a characteristic cytopathic effect
virus
virus

multiply
produce CPE
normal cells
????????????????????,????????(CPE)
(?????????????)
CPE including
morphologic changes

fusion of cells
form multinucleated giant cells
inclusion body formation

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Not produce a CPE
hemadsorption(?????) interference change of
cell metabolisms
? Detection of virus amount and
infectivity---- TCID50 or PFU
50 tissue culture infective dose
plaque forming unit (??????)
?Final identification of virus
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3.Serological diagnosis
of viral infection
? Principles
???????????? ???????????
? Methods
neutralization test hemagglutination
inhibition test immunolabelling technique
western blot
(???????????)
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Hemagglutination
inhibition test
a.virusRBC?agglutination of RBC
HA
receptoe
(hemagglutination)
???????
b.(virusserum)RBC
?
absence of agglutination
(hemagglutination inhibition)
???????? ????????
????????????
???? ?,????
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4.Quick diagnosis
Light microscope
( inclusion body)
EM/IEM
(viral particles )
IF /SPRIA
(viral antigen)
ELISA
(viral antigen or antibody)
Hybridization and PCR
(viral nucleic acid)
Gene chip
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?. Prevention and Treatment of Viral
Infection

• 1.Antiviral drugs or agents

2.Immunopreparation
?IFN and IFN inducers
?gamma-globulin and antiviral
specific Ig ?Gene therapy

3. Prevention
(vaccines)
? Artificial active immunity ? Artificial passive
immunity
(HBIG, RIG and VZIG)