this is the full description of viruses. structure, figure, and the diseases caused by the virus, viroids, prions are briefly describe here.

1. Viruses, Viroids, andViruses, Viroids, and
PrionsPrions
Bits and Pieces that causeBits and Pieces that cause
diseasedisease

2. Are Viruses LivingAre Viruses Living
or Non-living?or Non-living?
 Viruses are both and neitherViruses are both and neither
 They haveThey have some properties of lifesome properties of life
but not othersbut not others
 For example, viruses can be killed,For example, viruses can be killed,
even crystallized like table salteven crystallized like table salt
 However, theyHowever, they can’t maintain acan’t maintain a
constant internal stateconstant internal state
(homeostasis).(homeostasis).

3. What are Viruses?What are Viruses?
 Viruses are geneticViruses are genetic
elements that replicateelements that replicate
independent of the cell’sindependent of the cell’s
chromosome(s) but notchromosome(s) but not
independently of theindependently of the
cells themselves.cells themselves.
 Have anHave an extra cellularextra cellular
form-can exist ousideform-can exist ouside
the host(the host(VIRIONVIRION))
 To multiply-should enterTo multiply-should enter
cell-cell-InfectionInfection

4. VirusesViruses
 Viruses contain DNA or RNA and aViruses contain DNA or RNA and a
protein coatprotein coat
 Some are enclosed by an envelopeSome are enclosed by an envelope
Naked/envelopedNaked/enveloped
 Some viruses have spikesSome viruses have spikes
 Most viruses infect only specificMost viruses infect only specific
types of cells in one hosttypes of cells in one host
 Host range is determined byHost range is determined by
specific host attachment sites andspecific host attachment sites and
cellular factorscellular factors

5. CharacteristicsCharacteristics
 Some viruses are enclosedSome viruses are enclosed
in an protectivein an protective envelopeenvelope
 Some viruses may haveSome viruses may have
spikesspikes to help attach toto help attach to
the host cellthe host cell
 Most viruses infect onlyMost viruses infect only
SPECIFIC host cellsSPECIFIC host cells
CAPSID
ENVELOPE
DNA
SPIKES

6. CharacteristicsCharacteristics
 Non living structuresNon living structures
 NoncellularNoncellular
 Contain a protein coat called theContain a protein coat called the capsidcapsid
 Have a nucleic acid core containingHave a nucleic acid core containing DNA orDNA or
RNARNA
 Complete complex of NA and ProteinComplete complex of NA and Protein
packaged is called NUCLEOCAPSID.packaged is called NUCLEOCAPSID.
 Capable of reproducingCapable of reproducing only when inside aonly when inside a
HOST cellHOST cell

7. CharacteristicsCharacteristics
ViralViral capsidscapsids
(coats) are made of(coats) are made of
individualindividual proteinprotein
subunitssubunits
Individual subunitsIndividual subunits
are calledare called
capsomeres.capsomeres.(20sides)(20sides)
Process –Process –
self-assemblyself-assembly
CAPSOMERES

8. CharacteristicsCharacteristics
Outside of host cells,Outside of host cells,
viruses areviruses are inactiveinactive
Lack ribosomes andLack ribosomes and
enzymesenzymes needed forneeded for
metabolismmetabolism
Use theUse the raw materialsraw materials
and enzymes of the hostand enzymes of the host
cell to be able tocell to be able to
reproducereproduce
EBOLA VIRUS
HIV VIRUS

9. CharacteristicsCharacteristics
Some viruses causeSome viruses cause diseasedisease
Smallpox, measles,Smallpox, measles,
mononucleosis, influenza, colds,mononucleosis, influenza, colds,
warts, AIDS, Ebolawarts, AIDS, Ebola
Some viruses may causeSome viruses may cause somesome
cancers like leukemiacancers like leukemia
Virus-free cells areVirus-free cells are rarerare
MEASLES

10. Viral HistoryViral History

11. Tobacco Mosaic VirusTobacco Mosaic Virus
Wendell StanleyWendell Stanley
(1935) crystallized(1935) crystallized
sapsap from sickfrom sick
tobacco plantstobacco plants
He discoveredHe discovered
viruses were made ofviruses were made of
nucleic acid andnucleic acid and
proteinprotein

12. Discovery of VirusesDiscovery of Viruses
BeijerinckBeijerinck (1897) coined(1897) coined
the Latin name “virus”the Latin name “virus”
meaningmeaning poisonpoison
He studiedHe studied filtered plantfiltered plant
juicesjuices & found they& found they
caused healthy plants tocaused healthy plants to
become sickbecome sick

13. SmallpoxSmallpox
Edward JennerEdward Jenner
(1796)(1796) developed adeveloped a
smallpox vaccine usingsmallpox vaccine using
mildermilder cowpox virusescowpox viruses
Deadly viruses areDeadly viruses are
said to besaid to be virulentvirulent
Smallpox has beenSmallpox has been
eradicated in theeradicated in the
world todayworld today

14. Viewing VirusesViewing Viruses
Viruses areViruses are smallersmaller
than the smallest cellthan the smallest cell
Measured in nmMeasured in nm(20-300nm)(20-300nm)
Viruses couldn’t beViruses couldn’t be
seen until theseen until the electronelectron
microscopemicroscope waswas
invented in theinvented in the 2020thth
centurycentury

15. Size of VirusesSize of Viruses

16. Viral StructureViral Structure

17. Viral ShapesViral Shapes
Viruses come in aViruses come in a variety of shapesvariety of shapes
Some may beSome may be helicalhelical shape like theshape like the EbolaEbola
virusvirus
Some may beSome may be polyhedralpolyhedral (ICOSAHEDRAL)(ICOSAHEDRAL)
shapes like theshapes like the influenzainfluenza virusvirus
Others have moreOthers have more complex shapescomplex shapes likelike
bacteriophagesbacteriophages

18. Helical VirusesHelical Viruses

19. Polyhedral (icosahedral)Polyhedral (icosahedral)
VirusesViruses

20. Complex VirusesComplex Viruses

21. Taxonomy of VirusesTaxonomy of Viruses

22. Viral TaxonomyViral Taxonomy
 FamilyFamily names end innames end in -viridae-viridae
 GenusGenus names end innames end in -virus-virus
 Viral speciesViral species: A group of viruses sharing: A group of viruses sharing
the same genetic information andthe same genetic information and
ecological niche (host).ecological niche (host).
 Common namesCommon names are used forare used for speciesspecies
 SubspeciesSubspecies are designated by aare designated by a numbernumber

23. Viral Taxonomy ExamplesViral Taxonomy Examples
 HerpesviridaeHerpesviridae
 HerpesvirusHerpesvirus
 Human herpes virus 1, HHV 2, HHV 3Human herpes virus 1, HHV 2, HHV 3
 RetroviridaeRetroviridae
 LentivirusLentivirus
 Human Immunodeficiency Virus 1, HIV 2Human Immunodeficiency Virus 1, HIV 2

24. Herpes VirusHerpes Virus
SIMPLEX I and II

25. AdenovirusAdenovirus
COMMON COLD

26. Influenza VirusInfluenza Virus

27. Chickenpox VirusChickenpox Virus

28. Papillomavirus –Papillomavirus –
Warts!Warts!

29.  HOST they infect;HOST they infect;bacteriophages,animal,plantbacteriophages,animal,plant
 RNA or DNA Virus: ss or dsRNA or DNA Virus: ss or ds
 RNA DNA virusesRNA DNA viruses
Ss RNA = Retroviruses; ds DNA= HepadnavirusSs RNA = Retroviruses; ds DNA= Hepadnavirus
 Do or do NOT have an envelopeDo or do NOT have an envelope
 Capsid shape:Capsid shape:helical ;icosahedral; complexhelical ;icosahedral; complex
Used for VirusUsed for Virus
IdentificationIdentification

30. BacteriophagesBacteriophages

31. PhagesPhages
Viruses that attackViruses that attack
bacteria are calledbacteria are called
bacteriophagebacteriophage or justor just
phagephage
T-phagesT-phages are a specificare a specific
class of bacteriophagesclass of bacteriophages
withwith icosahedral headsicosahedral heads,,
double-strandeddouble-stranded DNADNA,,
andand tailstails

32. T-phagesT-phages
The most commonly studiedThe most commonly studied
T-phages areT-phages are T4 and T 7T4 and T 7
They infectThey infect E. coliE. coli , an, an
intestinal bacteriaintestinal bacteria
Six smallSix small spikesspikes at the baseat the base
of a contractile tail are usedof a contractile tail are used
toto attach to the host cellattach to the host cell
Inject viral DNAInject viral DNA into cellinto cell

33. Escherichia ColiEscherichia Coli BacteriumBacterium
T - EVEN PHAGES ATTACK THIS BACTERIUM

34. T-EvenT-Even
BacteriophagesBacteriophages

35. Diagram of T-4Diagram of T-4
BacteriophageBacteriophage
Head withHead with 2020
triangulartriangular
surfacessurfaces
Capsid containsCapsid contains
DNADNA
Head & tailHead & tail
fibers made offibers made of
proteinprotein

36. RetrovirusesRetroviruses

37. Characteristics ofCharacteristics of
RetrovirusesRetroviruses
ContainContain RNARNA, not DNA, not DNA
FamilyFamily RetroviridaeRetroviridae
Contain enzyme calledContain enzyme called ReverseReverse
TranscriptaseTranscriptase
When a retrovirus infects a cell, itWhen a retrovirus infects a cell, it
injects itsinjects its RNA and reverseRNA and reverse
transcriptase enzymetranscriptase enzyme into theinto the
cytoplasm of that cellcytoplasm of that cell

38. ENZYME

39. RetrovirusesRetroviruses
The enzymeThe enzyme reversereverse
transcriptasetranscriptase (or RTase),(or RTase),
which causes synthesiswhich causes synthesis
of a complementary DNAof a complementary DNA
moleculemolecule (cDNA)(cDNA) usingusing
virus RNA as a templatevirus RNA as a template
RTase

40. RetrovirusesRetroviruses
HIV, the AIDSHIV, the AIDS
virus, is a retrovirusvirus, is a retrovirus
Feline LeukemiaFeline Leukemia
VirusVirus is also ais also a
retrovirusretrovirus

41. Enzymes in virionsEnzymes in virions
 LysozymeLysozyme
 RNA dependant DNA polymerase-RNA dependant DNA polymerase-
Reverse transcriptaseReverse transcriptase
 NeuraminadasesNeuraminadases

42. Viroids & PrionsViroids & Prions

43. ViroidsViroids
Small, circular ss-Small, circular ss-
RNARNA moleculesmolecules withoutwithout
a protein coata protein coat
InfectInfect plantsplants
Do not infect animalsDo not infect animals
Potato faminePotato famine inin
IrelandIreland
Resemble intronsResemble introns cutcut
out of eukaryoticout of eukaryotic
Mechanism ofMechanism of
infection unclearinfection unclear

44. ViriodsViriods
 ssRNAssRNA
 Size from 246 to 399 nmSize from 246 to 399 nm
 Show considerable sequence homologyShow considerable sequence homology
 Cause a no of plant diseases:Cause a no of plant diseases:
 Coconut cadang cadang viroid-246 nucleotidesCoconut cadang cadang viroid-246 nucleotides
 Citrus exocortis viroid- 375 nucleotidesCitrus exocortis viroid- 375 nucleotides
 Potato spindle tuber viroid -359 nucleotidesPotato spindle tuber viroid -359 nucleotides

45.  Extracellular form=naked RNAExtracellular form=naked RNA
 RNA has no protein encoding geneRNA has no protein encoding gene
 Viroid totally dep on host for its replication.Viroid totally dep on host for its replication.
 Tho’ ssRNA circular,secondary structure=resemblingTho’ ssRNA circular,secondary structure=resembling
ds molecule with closed ends.ds molecule with closed ends.
 Enters plant through wound:by insect or mechanicalEnters plant through wound:by insect or mechanical
damage.damage.
 Replicated by plant RNA polymerasesReplicated by plant RNA polymerases
 Symptomless or mild to lethal symptomsSymptomless or mild to lethal symptoms
 Severe symptoms growth related.-are type ofSevere symptoms growth related.-are type of
regulatory RNAregulatory RNA

46. PrionsPrionsPrions arePrions are “infectious proteins”“infectious proteins”
 They are normal body proteinsThey are normal body proteins
that getthat get converted into an alternateconverted into an alternate
configurationconfiguration by contact with otherby contact with other
prion proteinsprion proteins
 They haveThey have no DNA or RNAno DNA or RNA
The main protein involved in humanThe main protein involved in human
andand mammalian prion diseasesmammalian prion diseases isis
calledcalled “PrP”(neurons)“PrP”(neurons)
Prions don’t simply subvert hostPrions don’t simply subvert host
enzymes in the cell but convert aenzymes in the cell but convert a
normal protein into a selfnormal protein into a self
propagating conformational state.propagating conformational state.

47. PrionsPrions
Figure 13.21
PrPc
PrPSc
1 2 3 4
5 6 7 8
Endosome
Lysosome

48. Prion DiseasesPrion Diseases
Prions formPrions form insolubleinsoluble
deposits in the braindeposits in the brain
Causes neurons toCauses neurons to
rapidly degeneration.rapidly degeneration.
Mad cow diseaseMad cow disease
(bovine spongiform(bovine spongiform
encephalitis: BSE) is anencephalitis: BSE) is an
exampleexample
People in New GuineaPeople in New Guinea
used to suffer fromused to suffer from
kurukuru, which they got, which they got
from eating the brainsfrom eating the brains
of their enemiesof their enemies

49. PrionsPrions
 Distict extracellular formDistict extracellular form
 Cause scrapie in sheepCause scrapie in sheep
 BSE in cattleBSE in cattle
 Chronic wasting disease in deer and elkChronic wasting disease in deer and elk
 Kuru and Creutzfeldt-Jacob disease CJD in humansKuru and Creutzfeldt-Jacob disease CJD in humans
 Prion diseases =transmissible spongiformPrion diseases =transmissible spongiform
encephalopathies –TSEencephalopathies –TSE
 1997-Stanley Pruisner –noble prize1997-Stanley Pruisner –noble prize
 1996 prion causing BSE can cause a new variant nv-1996 prion causing BSE can cause a new variant nv-
CJD in humans by consuming beef with BSECJD in humans by consuming beef with BSE

50. Viral ReplicationViral Replication

51. Viral AttackViral Attack
 Viruses are very specific as to whichViruses are very specific as to which
species they attackspecies they attack
 HOST specificHOST specific
 Humans rarely share viral diseases withHumans rarely share viral diseases with
other animalsother animals
 Eukaryotic virusesEukaryotic viruses usually haveusually have
protectiveprotective envelopesenvelopes made from themade from the
host cell membranehost cell membrane

52. Lytic vs LysogenicLytic vs Lysogenic
 Lytic cycleLytic cycle
 Phage causes lysis and death ofPhage causes lysis and death of
host cellhost cell
 Lysogenic cycleLysogenic cycle
 Prophage DNA incorporated inProphage DNA incorporated in
host DNAhost DNA

53. 5 Steps of Lytic Cycle5 Steps of Lytic Cycle
 1.1. AttachmentAttachment to the cellto the cell
 2.2. PenetrationPenetration (injection) of viral DNA or(injection) of viral DNA or
RNARNA
 3.3. Replication (Biosynthesis)Replication (Biosynthesis) of new viralof new viral
proteins and nucleic acidsproteins and nucleic acids
 4.4. AssemblyAssembly (Maturation)(Maturation) of the newof the new
virusesviruses
 5.5. ReleaseRelease of the new viruses into theof the new viruses into the
environment (cell lyses)environment (cell lyses)

54.  AttachmentAttachment Phage attaches by tail fibersPhage attaches by tail fibers
to host cell1to host cell1
 PenetrationPenetration Phage lysozyme opens cellPhage lysozyme opens cell
wall, tail sheath contracts to force tailwall, tail sheath contracts to force tail
core and DNA into cellcore and DNA into cell
 BiosynthesisBiosynthesis Production of phage DNAProduction of phage DNA
and proteinsand proteins
 MaturationMaturation Assembly of phage particlesAssembly of phage particles
 ReleaseRelease Phage lysozyme breaks cell wallPhage lysozyme breaks cell wall
Lytic Cycle ReviewLytic Cycle Review

55. BacteriophageBacteriophage ReplicationReplication
Bacteriophage injectBacteriophage inject
their nucleic acidtheir nucleic acid
TheyThey lyse (break open)lyse (break open)
the bacterial cell whenthe bacterial cell when
replication is finishedreplication is finished

56. Attachment:
Phage
attaches to
host cell.
Penetration:
Phage pnetrates
host cell and
injects its DNA.
Merozoites
released into
bloodsteam from
liver may infect
new red blood cells
1
2
3
Bacterial
cell wall
Bacterial
chromosome
Capsid DNA
Capsid
Sheath
Tail fiber
Base plate
Pin
Cell wall
Tail
Plasma membrane
Sheath contracted
Tail core

57. 4 Maturation:
Viral components
are assembled into
virions.
Tail
5 Release:
Host cell lyses
and new virions
are released.
DNA
Capsid
Tail fibers

58. One-step GrowthOne-step Growth
CurveCurve

59. Viral LatencyViral Latency
Some viruses have the ability to becomeSome viruses have the ability to become
dormantdormant inside the cellinside the cell
CalledCalled latent viruseslatent viruses
They may remainThey may remain inactiveinactive for longfor long
periods of time (years)periods of time (years)
Later, theyLater, they activateactivate to produce newto produce new
virusesviruses in response to some externalin response to some external
signalsignal
HIVHIV andand HerpesHerpes viruses are examplesviruses are examples

60. Lysogenic CycleLysogenic Cycle
Phage DNAPhage DNA injectedinjected
into host cellinto host cell
Viral DNA joins hostViral DNA joins host
DNA forming aDNA forming a prophageprophage
When anWhen an activationactivation
signalsignal occurs, the phageoccurs, the phage
DNA starts replicatingDNA starts replicating

61. Lysogenic CycleLysogenic Cycle
Viral DNA (part ofViral DNA (part of
prophage) may stayprophage) may stay
inactiveinactive in host cell forin host cell for
long periods of timelong periods of time
Replicated during eachReplicated during each
binary fissionbinary fission
Over time,Over time, many cellsmany cells
form containing theform containing the
prophagesprophages

62. Viral LatencyViral Latency
Once aOnce a prophage cell is activatedprophage cell is activated, host, host
cell enters the lytic cellcell enters the lytic cell
New viruses form a & theNew viruses form a & the cell lysescell lyses
(bursts)(bursts)
Virus said to beVirus said to be virulent (deadly)virulent (deadly)
INACTIVE STAGE
ACTIVE
STAGE

63. Virulent VirusesVirulent Viruses
HOST
CELL
LYSES &
DIES

64. The Lysogenic CycleThe Lysogenic Cycle

65. Latency in EukaryotesLatency in Eukaryotes
SomeSome eukaryoticeukaryotic
virusesviruses remain dormantremain dormant
for many years in thefor many years in the
nervous system tissuesnervous system tissues
 ChickenpoxChickenpox (caused by(caused by
the virusthe virus VaricellaVaricella
zosterzoster) is a childhood) is a childhood
infectioninfection
It canIt can reappear later inreappear later in
life aslife as shinglesshingles, a painful, a painful
itching rash limited toitching rash limited to
small areas of the bodysmall areas of the body
SHINGLES

66. Latency in EukaryotesLatency in Eukaryotes
HerpesHerpes viruses alsoviruses also
becomebecome latent in thelatent in the
nervous systemnervous system
A herpes infectionA herpes infection lastslasts
for a person’s lifetimefor a person’s lifetime
Genital herpesGenital herpes (Herpes(Herpes
Simplex 2)Simplex 2)
Cold sores or feverCold sores or fever
blistersblisters (Herpes(Herpes
Simplex1)Simplex1)
SKIN TO SKIN CONTACT
PASSED AT BIRTH TO
BABY

67. Treatment forTreatment for
Viral DiseaseViral Disease

68. VaccinesVaccines
 AnAn attenuated virusattenuated virus is a weakened, lessis a weakened, less
vigorous virusvigorous virus
 ““Attenuate"Attenuate" refers to procedures thatrefers to procedures that
weaken an agent of diseaseweaken an agent of disease (heating)(heating)
 AA vaccinevaccine against a viral disease can beagainst a viral disease can be
made from an attenuated, less virulentmade from an attenuated, less virulent
strain of the virusstrain of the virus
 Attenuated virus is capable ofAttenuated virus is capable of stimulatingstimulating
an immune responsean immune response and creatingand creating immunity,immunity,
but not causing illnessbut not causing illness

69. Other Viral TreatmentsOther Viral Treatments
InterferonInterferon are naturallyare naturally
occurring proteinsoccurring proteins mademade
by cellsby cells to fight virusesto fight viruses
Genetic alteringGenetic altering ofof
viruses (attenuatedviruses (attenuated
viruses)viruses)
Antiviral drugsAntiviral drugs (AZT)(AZT)
Protease inhibitorsProtease inhibitors ––
prevent capsid formationprevent capsid formation

70. Growing VirusesGrowing Viruses
 Viruses must beViruses must be
grown in livinggrown in living
cells.cells.
 BacteriophagesBacteriophages
form plaques onform plaques on
a lawn ofa lawn of
bacteria.bacteria. 
Figure 13.6

71. Growing VirusesGrowing Viruses
 AnimalAnimal
viruses mayviruses may
be grown inbe grown in
living animalsliving animals
or inor in
embryonatedembryonated
eggs.eggs.
Figure 13.7

72. Growing VirusesGrowing Viruses
 Animal and plants viruses may be grownAnimal and plants viruses may be grown
in cell culture.in cell culture.
 Continuous cell lines may be maintainedContinuous cell lines may be maintained
indefinitely.indefinitely.
Figure 13.8

73.  Cytopathic effectsCytopathic effects
 Serological testsSerological tests
 Detect antibodies against viruses in a patientDetect antibodies against viruses in a patient
 Use antibodies to identify viruses in neutralizationUse antibodies to identify viruses in neutralization
tests, viral hemagglutination, and Western blottests, viral hemagglutination, and Western blot
 Nucleic acidsNucleic acids
 RFLPsRFLPs
 PCRPCR
Virus IdentificationVirus Identification

74. Virus IdentificationVirus Identification
Figure 13.9

75. Multiplication of AnimalMultiplication of Animal
virusesviruses
 AttachmentAttachment Viruses attaches to cellViruses attaches to cell
membranemembrane
 PenetrationPenetration By endocytosis or fusionBy endocytosis or fusion
 UncoatingUncoating By viral or host enzymesBy viral or host enzymes
 BiosynthesisBiosynthesis Production of nucleic acid andProduction of nucleic acid and
proteinsproteins
 MaturationMaturation Nucleic acid and capsid proteinsNucleic acid and capsid proteins
assembleassemble
 ReleaseRelease By budding (enveloped viruses) orBy budding (enveloped viruses) or
rupturerupture

76. Attachment, Penetration,Attachment, Penetration,
and Uncoatingand Uncoating
Figure 13.14

77. Release of an enveloped virus byRelease of an enveloped virus by
buddingbudding
Figure 13.20

78. Multiplication of DNA VirusMultiplication of DNA Virus
Figure 13.15
Virion attaches to host cell
Virion penetrates
cell and its DNA is
uncoated
Early transcription and
translation; enzymes are
synthesized
1
2
3
DNA
Late transcription;
DNA is replicated
4
Late translation;
capsid proteins
are synthesized
5
Virions mature6
Capsid
Papovavirus
Host cell
DNA
Cytoplasm
Virions are released7
Capsid proteins
mRNA

79. Pathways of Multiplication forPathways of Multiplication for
RNA-Containing VirusesRNA-Containing Viruses
Figure 13.17

80. Multiplication of a RetrovirusMultiplication of a Retrovirus
Figure 13.19
Retrovirus penetrates
host cell.
Virion penetrates
cell and its DNA is
uncoated
The new viral DNA is
tranported into the host cell’s
nucleus and integrated as a
provirus. The provirus may
divide indefinitely with the
host cell DNA.
1
2
3
DNA
Transcription of the
provirus may also occur,
producing RNA for new
retrovirus genomes and
RNA that codes for the
retrovirus capsid and
envelope proteins.
4
Mature
retrovirus
leaves host
cell, acquiring
an envelope as
it buds out.
5
Capsid
Reverse
transcriptase
Virus Two identical + stands of RNA
DNA of one of the host
cell’s chromosomes
Provirus
Host
cell
Reverse
transcriptase
Viral RNA
RNA
Viral proteins
Identical
strands of
RNA

81.  Activated oncogenes transform normalActivated oncogenes transform normal
cells into cancerous cells.cells into cancerous cells.
 Transformed cells have increased growth,Transformed cells have increased growth,
loss of contact inhibition, tumor specificloss of contact inhibition, tumor specific
transplant and T antigens.transplant and T antigens.
 The genetic material of oncogenic virusesThe genetic material of oncogenic viruses
becomes integrated into the host cell'sbecomes integrated into the host cell's
DNA.DNA.
CancerCancer

82.  Oncogenic DNAOncogenic DNA
VirusesViruses
 AdenoviridaeAdenoviridae
 HeresviridaeHeresviridae
 PoxviridaePoxviridae
 PapovaviridaePapovaviridae
 HepadnaviridaeHepadnaviridae
Oncogenic VirusesOncogenic Viruses
 Oncogenic RNAOncogenic RNA
virusesviruses
 RetroviridaeRetroviridae
 Viral RNA isViral RNA is
transcribed to DNAtranscribed to DNA
which can integratewhich can integrate
into host DNAinto host DNA
 HTLV 1HTLV 1
 HTLV 2HTLV 2

83. Latent vs PersistentLatent vs Persistent
 Latent Viral InfectionsLatent Viral Infections
 Virus remains in asymptomatic host cell forVirus remains in asymptomatic host cell for
long periodslong periods
 Cold sores, shinglesCold sores, shingles
 Persistent Viral InfectionsPersistent Viral Infections
 Disease processes occurs over a long period,Disease processes occurs over a long period,
generally fatalgenerally fatal
 Subacute sclerosing panencephalitis (measlesSubacute sclerosing panencephalitis (measles
virus)virus)

84. Figure 13.22
 Plant VirusesPlant Viruses
 Plant virusesPlant viruses
enter throughenter through
wounds or viawounds or via
insectsinsects
 ViroidsViroids
 Viroids areViroids are
infectiousinfectious
RNA; potatoRNA; potato
spindle tuberspindle tuber
diseasedisease

85. Some Plant VirusesSome Plant Viruses
Table 13.6

86. Virus FamiliesVirus Families
 Single-stranded DNA,Single-stranded DNA,
nonenveloped virusesnonenveloped viruses
 ParvoviridaeParvoviridae
 Human parvovirusHuman parvovirus
 Fifth diseaseFifth disease
 Anemia inAnemia in
immunocompromisedimmunocompromised
patientspatients

87. Double-stranded DNA,Double-stranded DNA,
nonenveloped virusesnonenveloped viruses
 MastadenovirusMastadenovirus
 RespiratoryRespiratory
infections ininfections in
humanshumans
 Tumors inTumors in
animalsanimals

88. Double-stranded DNA,Double-stranded DNA,
nonenveloped virusesnonenveloped viruses
 PapillomavirusPapillomavirus
(human wart(human wart
virus)virus)
 PolyomavirusPolyomavirus
 Cause tumors,Cause tumors,
some causesome cause
cancercancer

89. Double-stranded DNA,Double-stranded DNA,
nonenveloped virusesnonenveloped viruses
 OrthopoxvirusOrthopoxvirus
(vaccinia and(vaccinia and
smallpoxsmallpox
viruses)viruses)
 MolluscipoxvirusMolluscipoxvirus
 Smallpox,Smallpox,
molluscummolluscum
contagiosum,contagiosum,
cowpoxcowpox

90.  SimplexvirusSimplexvirus (HHV1 and HHV 2)(HHV1 and HHV 2)
 VaricellavirusVaricellavirus (HHV 3)(HHV 3)
 LymphocryptovirusLymphocryptovirus (HHV 4)(HHV 4)
 CytomegalovirusCytomegalovirus (HHV 5)(HHV 5)
 RoseolovirusRoseolovirus (HHV 6)(HHV 6)
 HHV 7HHV 7
 Kaposi's sarcoma (HHV 8)Kaposi's sarcoma (HHV 8)
 Some herpesviruses can remainSome herpesviruses can remain
latent in host cellslatent in host cells
Double-stranded DNA,Double-stranded DNA,
nonenveloped virusesnonenveloped viruses

91. Double-stranded DNA,Double-stranded DNA,
nonenveloped virusesnonenveloped viruses
 HepadnavirusHepadnavirus
(Hepatitis B(Hepatitis B
virus)virus)
 Use reverseUse reverse
transcriptase totranscriptase to
produce DNAproduce DNA
from mRNAfrom mRNA

92. Single-stranded RNA, +Single-stranded RNA, +
strand, nonenvelopedstrand, nonenveloped
 EnterovirusEnterovirus
 EnterovirusesEnteroviruses
includeinclude
poliovirus andpoliovirus and
coxsackieviruscoxsackievirus
 RhinovirusRhinovirus
 Hepatitis AHepatitis A
virusvirus

93. Single-stranded RNA, +Single-stranded RNA, +
strand, nonenvelopedstrand, nonenveloped
 Hepatitis E virusHepatitis E virus
 NorovirusNorovirus
(Norwalk agent)(Norwalk agent)
causescauses
gastroenteritisgastroenteritis

94. Single-stranded RNA, +Single-stranded RNA, +
strand, nonenvelopedstrand, nonenveloped
 AlphavirusAlphavirus
 Alphaviruses areAlphaviruses are
transmitted bytransmitted by
arthropods;arthropods;
include EEE,include EEE,
WEEWEE
 RubivirusRubivirus
(rubella virus)(rubella virus)

95. Single-stranded RNA, +Single-stranded RNA, +
strand, nonenvelopedstrand, nonenveloped
 ArbovirusesArboviruses cancan
replicate inreplicate in
arthropods; includearthropods; include
yellow fever, dengue,yellow fever, dengue,
SLE, and West NileSLE, and West Nile
virusesviruses
 Hepatitis C virusHepatitis C virus

96. Single-stranded RNA, +Single-stranded RNA, +
strand, nonenvelopedstrand, nonenveloped
 CoronavirusCoronavirus
 UpperUpper
respiratoryrespiratory
infectionsinfections

97. Single-stranded RNA, –Single-stranded RNA, –
strand, one RNA strandstrand, one RNA strand
 VesiculovirusVesiculovirus
 LyssavirusLyssavirus
(rabies virus)(rabies virus)
 Cause numerousCause numerous
animal diseasesanimal diseases

98. Single-stranded RNA, –Single-stranded RNA, –
strand, one RNA strandstrand, one RNA strand
 FilovirusFilovirus
 Enveloped,Enveloped,
helical viruseshelical viruses
 Ebola andEbola and
MarburgMarburg
virusesviruses

99. Single-stranded RNA, –Single-stranded RNA, –
strand, one RNA strandstrand, one RNA strand
 ParamyxovirusParamyxovirus
 MorbillivirusMorbillivirus
 ParamyxovirusParamyxovirus
causescauses
parainfluenza,parainfluenza,
mumps andmumps and
NewcastleNewcastle
diseasedisease

100. Single-stranded RNA, –Single-stranded RNA, –
strand, one RNA strandstrand, one RNA strand
 Hepatitis DHepatitis D
virusvirus
 Depends onDepends on
coinfection withcoinfection with
HepadnavirusHepadnavirus

101.  InfluenzavirusInfluenzavirus
(Influenza(Influenza
viruses A and B)viruses A and B)
 Influenza CInfluenza C
virusvirus
 Envelope spikesEnvelope spikes
can agglutinatecan agglutinate
RBCsRBCs
Single-stranded RNA, –Single-stranded RNA, –
strand, multiple RNA strandsstrand, multiple RNA strands

102.  BunyavirusBunyavirus (CE virus)(CE virus)
 HantavirusHantavirus
Single-stranded RNA, –Single-stranded RNA, –
strand, multiple RNA strandsstrand, multiple RNA strands

103.  ArenavirusArenavirus
 Helical capsidsHelical capsids
contain RNA-contain RNA-
containingcontaining
granulesgranules
 LymphocyticLymphocytic
choriomeningitischoriomeningitis
 VEE and LassaVEE and Lassa
FeverFever
Single-stranded RNA, –Single-stranded RNA, –
strand, multiple RNA strandsstrand, multiple RNA strands

104.  LentivirusLentivirus (HIV)(HIV)
 Oncogenic virusesOncogenic viruses
 Use reverseUse reverse
transcriptasetranscriptase
to produceto produce
DNA from viralDNA from viral
genomegenome
 Includes allIncludes all
RNA tumorRNA tumor
virusesviruses
Single-stranded RNA, two RNA strands,Single-stranded RNA, two RNA strands,
produce DNAproduce DNA

105. Double-stranded RNA,Double-stranded RNA,
nonenvelopednonenveloped
 ReovirusReovirus
(Respiratory(Respiratory
Enteric Orphan)Enteric Orphan)
 RotavirusRotavirus
 Mild respiratoryMild respiratory
infections andinfections and
gastroenteritisgastroenteritis
 Colorado tickColorado tick
feverfever