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Pathology > Virology > Flashcards

Virology Flashcards

1
Q

What percent of the human genome is retroviral DNA?

A

8-10%

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2
Q

Do host-adapted viruses cause damage?

A

No

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3
Q

Describe the difference between positive sense and negative sense strands

A

Positive sense are ready to encode

Negative sense need to be converted to positive sense to form mRNA

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4
Q

What is the purpose of glycoproteins?

A

Used to attach to cell surface of host

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5
Q

What is an envelope?

A

A membrane covering the capsid that comes from the host membrane

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6
Q

What is the most common symmetry?

A

Icosahedral or helical

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7
Q

What is a capsomere?

A

A subunit of the capsid that gives the virus its pattern

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8
Q

What two things make up the virion?

A

Genomic material and capsid

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9
Q

What is the most stable biological morphology?

A

Isocahedron

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10
Q

What forms the isocahedron?

A

Viral protein coat or capsid protein

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11
Q

What defines an isocahedron?

A

20 Equilateral triangles at its faces

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12
Q

What is T equal to in isocahedron?

A

1

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13
Q

Are most helical viruses enveloped or non-enveloped?

A

Enveloped - cannot survive in environment

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14
Q

What makes viruses highly adapatable in hosts?

A

The envelope

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15
Q

Where does transcription and translation occur?

A

Transcription - nucleus

translation - cytoplasm

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16
Q

What are 6 DNA viruses? (there is a pneumonic)

A 
HHAPPPY
Herpes
Hepadna
Adeno
Papova
Parvo
Pox
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17
Q

Which 3 DNA viruses are naked?

A

Adeno
Papova
Parvo
(APP)

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18
Q

Which one of those 6 viruses is not icosahedral?

A

Pox

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19
Q

Which one of those viruses is not dsDNA, but ssDNA?

A

Parvovirus

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20
Q

What are the 10 steps of replication for DNA viruses?

A
  1. Attachment
  2. Penetration
  3. Uncoating of virus + transport of genome to replication site
  4. Early transcription
  5. Early translation + early proteins
  6. Viral DNA synthesis
  7. Late transcription
  8. Late translation and synthesis of structural proteins
  9. Assembly
  10. Release
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21
Q

Which 3 DNA viruses are enveloped?

A

Herpes, Hepadna, Pox

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22
Q

How does attachment occur?

A

Via attachment protein on capsid (naked) or envelope attaching to complementary protein on host cell

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23
Q

What can interfere with attachment?

A

An antibody against spike protein - evolutionary pressure on spike protein to change antigenic nature

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24
Q

What happens if a virus attaches to a rbc, and what can prevent this?

A

Agglutination

Antibody against spike protein called Haemagglutination-inhibiting antibody

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25
Q

What does penetration involve? (2 options)

A

Fusion of envelope with PM of cell (mediated by specific proteins) and release of nucleocapsid into cytoplasm

OR engulfement of virus by cell by adsorptive endocytosis before viral genome released

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26
Q

What does uncoating of virus and transport of genome to site of replication involve, where does it occur?

A

Occurs in cytoplasm but for most DNA viruses happens in nucleus following migration of nucleocapsid through cytoplasm across nuclear membrane

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27
Q

How does herpes virus gain entry to the nucleus?

A

Carry protein stimulates cell to do mitosis so virus genome can go into nuclei and replicate
Some viruses can only get to nucleus during mitosis

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28
Q

What happens in early transcription, translation and early proteins?

A

Formation of mRNA from virus DNA, and formation of early viral-coded proteins

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29
Q

What do early viral-coded proteins do?

A

Enzymes for DNA synthesis

DNA dependent DNA polymerases for example

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30
Q

What enzyme allows the formation of viral mRNA from viral DNA?

A

DNA-dependent RNA polymerase

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31
Q

Which strand is transcribed?

A

Template strand

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32
Q

Where do transcriptional events happen and what virus is the exception?

A

Nucleus

Poxviruses replicate in cytoplasm

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33
Q

Where does mRNA then go to from the nucleus, and what is formed next? then where do those products go?

A

mRNA goes from nucleus -> cytoplasm where translation of coded proteins occurs to DNA dependent DNA polymerase for example

Coded proteins then go back to nucleus for late transcription

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34
Q

What happens at late transcription?

A

The viral progeny and immediate early proteins go into the late transcription phase in nucleus for formation of late proteins that form capsomeres and capsid

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35
Q

Where does the primary assembly of herpesvirus occur?

A

Nucleus

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36
Q

How does release occur?

A

By autolysis of the cell or by virus induced programmed cell death

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37
Q

What is a prion?

A

An abnormal form of normal cell protein found in PM of nerve cells

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38
Q

What does prion infection cause?

A

Spongiform encephalopathy

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39
Q

What 3 adjectives describe prion infections?

A

Infectious
Heritable
Spontaneous

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40
Q

What are 2 forms of scrapie?

A

Classical - transmitted between licking bones (not in aus)

Atypical - spontaneous mutation (in aus)

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41
Q

What lesions in the brain do prions cause?

A

Vacuoles in brain tissue

spongey appearance

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42
Q

What steps for RNA replication are the same as DNA?

A

1-3
Attachment
Penentration
Uncoating of coat + release of viral genome

43
Q

Name 4 positive sense RNA viruses

A

Picornaviridae
Coronaaviridae
Flaviviridae (pestivirus)
Togaviridae

44
Q

What dont ss rna positive sense viruses need for transcription and translation?

A

Intravirion enzymes - they are readily transcribable with mRNA that has a methyl cap and poly-A tail

45
Q

Which type of virus bypassess the nuclei and begins translation right away in the cytoplasm and what does this cause?

A

Postivie sense RNA

They replicate in the cytoplasm - no nuclear inclusion bodies

46
Q

How do capsid and enveloped viruses escape the cell?

A

Capsid - lysis (induction of apoptosis)
Envelope - budding

Some viruses can escape via cell fusion (transmitted by cell to cell contact)

47
Q

What happens following uncoating of a positive sense RNA virus (5 steps)

A

Uncoating -> viral RNA translated -> RNA dependent RNA polymerase created -> transcription of mRNA -> viral capsid proteins translated

48
Q

Where does genome replication occur in +dsRNA virus?

A

Within capsid - not cytoplasm

Then mRNA template released and translation happens in cytoplasm

49
Q

What type of virus forms cytoplasmic inclusion bodies?

A

Positive sense RNA viruses

50
Q

Name 6 negative sense RNA viruses

A

Influenza viruses

Always bring polymerase or fail replication

Arenavirus
Bunyavirus
Paramyxovirus
Orthomyxovirus
Filovirus
Rabdoviruses
51
Q

What is the first thing negative sense RNA viruses have to do?

A

Transcribe to positive sense mRNA template by a viral intravirion transcriptase

52
Q

Once a negative sense virus has coded for +mRNA, what is produced first, and what combines to form progeny virus?

A

Early viral proteins (RNA polymerase) -> progeny viral (-)sense RNA

Late viral proteins -> structural proteins

Structural proteins + (-) sense RNA assembled to form progeny virus

53
Q

What is cap snatching and what virus does this?

A

Viral RNA dependent RNA polymerase cleaves 5’ capped host mRNAs to prime viral RNA synthesis

Influenza A

54
Q

How do negative sense viruses replicate?

A

Virus enters by endocytosis and uncoats

viral mRNA transcribed from neg sense genome -> template for translation

Viral proteins accumulate in cytoplasm + associate with viral RNAs to form nucleocapsids

Virions assembled and released from cell

55
Q

What is one example of a retrovirus?

A

HIV

56
Q

How do retroviruses replicate? (4 steps)

A
  1. Reverse transcriptase converts viral RNA to ssDNA, then to dsDNA
  2. dsDNA enters nucleus via integration complex + integrates into cell DNA
  3. Host cell transcriptase forms early and late phase mRNA, and progeny viral RNA
  4. Viral proteins and progeny viral RNA combine to form progeny virus
57
Q

What is canine parvovirus dependent on to replicate in a host?

A

Dividing crypt cells

58
Q

What is the incubation for parvo?

A

3-7d

59
Q

What can parvo survive in?

A

pH 3-9

56-80 degrees for 1 hour

60
Q

What kills parvo?

A

Formaldehyde and chloramines

61
Q

Is parvo enveloped or non-enveloped?

A

Non-enveloped - can survive in environment

62
Q

What are 4 factors affecting result of viral infection?

A

NUmber of particles + virulence
Speed of replication and spread to target organs
Degree of cellular damage
Effectiveness of host defence

63
Q

What are 3 latent infections?

A

Herpes zoster
Chicken pox
Shingles

64
Q

Where are localised lesions limited to?

A

Sites of entry of virus

Skin, respiratory tract, alimentary tract

65
Q

What is cell tropism and what are 2 examples?

A

Viruses having affinity for particular tissues
Rabies - neurotropic
BVDV - lymphoid tissues

May have primary, secondary or tertiary phases of replication in other organs

66
Q

What is an immunopathologic disease?

A

Antibodies or lymphocytes aggravate viral infections by contributing to destruction

Equine infectious anaemia

67
Q

What happens the second time of infection with dengue haemorrhagic fever?

A

Cytokine storm

Antibody dependent enhancement of viral infection - helps virus bind to Fc receptors on monocyte

68
Q

What is a self-associated molecular pattern?

A

A “dont eat me” pattern the virus makes to protect against phagocytosis

BVDV E2 protein - allows infected cells to be recognised as self

69
Q

What are 3 examples of slow infections?

A

Rabies
Caprine arthritis encephalitis virus
Feline leukaemia

These are all retroviruses

70
Q

What is rabies, what does it do and how many types are there?

A

Enveloped retrovirus transmitted by bites

follows retrograde nerve sheaths to CNS inside sensory axons - long incubation period

11 types of rabies - we dont have classical type

71
Q

What does canine arthritis encephalitis virus cause?

A

PI in monocyte lineage
monocytes carry genome, replicate after they leave circulation and mature into macrophages
Replication in mammary gland and lung

72
Q

What 3 viruses cause proliferative lesions and what do they attack?

A

Papillomavirus
Poxvirus
Herpesvirus

Target G0/G1 or G2/M checkpoints

73
Q

What causes viral induced neoplasia?

A

Papillomaviruses
Retroviruses
Herpesviruses
Cervical cancer

74
Q

What do papillomaviruses cause?

A

No cell death, inflammation or viremia

Supress type I interferon to bypass immune system

75
Q

How to papilloma viruses infect?

A

Get to BM in skin
Basal cells produce virus + replicate in low concentration
Avoid recognition
Produce viral protein e6 (activate p53 gene) and e7 to cause uncontrolled replication

76
Q

What are 5 factors affecting transfer and persistence of virus infections?

A 
Resistence to environment
Mode of transmission 
Mutations 
Multiple hosts
Persistent Infection
77
Q

What are 3 characteristics of a non-enveloped virus?

A

More resistant to environment
Transmission less dependent on close contact
Smaller populations needed to maintain infection

78
Q

what are 3 characteristics of enveloped virus?

A

Inactivated outside animal host
Survival depends on close contact
Transmission best in density

79
Q

How does west nile virus spread?

A

Mosquito vectors

80
Q

How does akabane virus spread?

A

Culicoides species
potent teratogen in cattle, sheep and goats
Causes target areas to be neuron deficient

81
Q

When does akabane virus cause lesions?

A

<70d -> resorption or normal calf
76-104d - absence of cerebral hemispheres
103-174d - loss of ventral horn neurons
Perinatal - encephalomyelitis

82
Q

How does antigenic shift occur?

A

Poymerases make mistakes in viruses causing small mutations

Can eventually make new strains with different genome

83
Q

What type of virus causes intranuclear inclusion bodies?

A

dsDNA enveloped virus

84
Q

What is inclusion body rhinitis?

A

Caused by cytomegalovirus (dsDNA enveloped) - damages respiratory epithelium causing ulceration and inflammation
nuclear inclusion bodies - replicate in nucleus

85
Q

What are 6 ways we can demonstrate characterisitc lesions?

A 
Inclusion bodies 
Virus isolation
PCR
Demonsrating viral antigen
Immunofluorescence
Latex agglutination
86
Q

How do we PCR RNA viruses?

A

Convert to DNA first

87
Q

How do we demonstrate viral antigens?

A

Within lesions - transmission electronmicroscopy or immunohistochemistry (RAT)

Polycloncal antibodies
Monoclonal antibodies - targets one epitope of virion

88
Q

How does latex agglutination work?

A

Coloured latex spehres coated with viral antibodies to detect antigens (or other way around)

89
Q

What are 4 serology methods?

A

Agar-gel immuno-diffusion (not sensitive)
Haemagglutination
Doubling dilutions
Haemagglutination inhibition

90
Q

What is an ELISA?

A

Enzyme linked immunosorbant assay
antibody onto plate, antigen attaches
Colour change occurs

91
Q

What are 4 types of vaccines?

A
  1. Live
  2. Inactivated
  3. Subunit virus vaccines
  4. DNA virus vaccines
92
Q

What are 4 types of live vaccines?

A
  1. Live pathogenic
  2. Live attenuated
  3. Heterologous
  4. Recombinant
93
Q

How do heterologous vaccines work?

A

They are of a closely related virus species of lesser virulence that provides immunity (cross reacts) with the one we want
Canine adenovirus 2 used to provide immunity for CA1

94
Q

What is a live recombinant virus?

A

Gene for immunogenic protein from one pathogenic virus inserted into another non-pathogenic virus

95
Q

3 advantages of live vaccines

A

Good immune response that is long lived
1 dose required
cheap

96
Q

3 disadcanages of live vaccines

A

Danger of reversion to virulence
Severe disease risk in immunocompromised
vaccine must remain alive (storage hard)

97
Q

How are inactivated vaccines prepared?

A

Virus grown in vitro and inactivated with chemicals (formaldehyde or B-propiolactone)

Mixed with oil for slow release and long lasting immunity

98
Q

Disadvantages of killed vaccines

A

Need booster
Expesive to prepare
More antigen needed than attenuated
Local reactions at site due to adjuvants used
Limited cell mediated response, okay humoral

99
Q

Advantages of killed vaccines

A

Cant cause disease

Easier to store

100
Q

What are 3 examples of adjuvants

A

Aluminium salts (good antibody, poor CMI response)
Liposomes and immunostimulating complexes
Complete freunds adjuvant

101
Q

List 4 types of innovative vaccines

A

DNA vaccine
mRNA vaccine
Subunit vaccine
Virus vector vaccine

All code for antigens

102
Q

How are subunit virus vaccines made?

A

By fractionation of whole virus preparations

Antigens produced using recombinant DNA technology

103
Q

How do DNA virus vaccines work?

A

Plasmid DNA encoding antigenic protein injected (intramuscular or intradermal) that is expressed in host

Antibody, T cell activation, cytotoxic T cells produced

Pathology (6 decks)

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