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Virology Flashcards

(103 cards)

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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
What does penetration involve? (2 options)
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
26
What does uncoating of virus and transport of genome to site of replication involve, where does it occur?
Occurs in cytoplasm but for most DNA viruses happens in nucleus following migration of nucleocapsid through cytoplasm across nuclear membrane
27
How does herpes virus gain entry to the nucleus?
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
28
What happens in early transcription, translation and early proteins?
Formation of mRNA from virus DNA, and formation of early viral-coded proteins
29
What do early viral-coded proteins do?
Enzymes for DNA synthesis | DNA dependent DNA polymerases for example
30
What enzyme allows the formation of viral mRNA from viral DNA?
DNA-dependent RNA polymerase
31
Which strand is transcribed?
Template strand
32
Where do transcriptional events happen and what virus is the exception?
Nucleus | Poxviruses replicate in cytoplasm
33
Where does mRNA then go to from the nucleus, and what is formed next? then where do those products go?
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
34
What happens at late transcription?
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
35
Where does the primary assembly of herpesvirus occur?
Nucleus
36
How does release occur?
By autolysis of the cell or by virus induced programmed cell death
37
What is a prion?
An abnormal form of normal cell protein found in PM of nerve cells
38
What does prion infection cause?
Spongiform encephalopathy
39
What 3 adjectives describe prion infections?
Infectious Heritable Spontaneous
40
What are 2 forms of scrapie?
Classical - transmitted between licking bones (not in aus) Atypical - spontaneous mutation (in aus)
41
What lesions in the brain do prions cause?
Vacuoles in brain tissue | spongey appearance
42
What steps for RNA replication are the same as DNA?
1-3 Attachment Penentration Uncoating of coat + release of viral genome
43
Name 4 positive sense RNA viruses
Picornaviridae Coronaaviridae Flaviviridae (pestivirus) Togaviridae
44
What dont ss rna positive sense viruses need for transcription and translation?
Intravirion enzymes - they are readily transcribable with mRNA that has a methyl cap and poly-A tail
45
Which type of virus bypassess the nuclei and begins translation right away in the cytoplasm and what does this cause?
Postivie sense RNA | They replicate in the cytoplasm - no nuclear inclusion bodies
46
How do capsid and enveloped viruses escape the cell?
Capsid - lysis (induction of apoptosis) Envelope - budding Some viruses can escape via cell fusion (transmitted by cell to cell contact)
47
What happens following uncoating of a positive sense RNA virus (5 steps)
Uncoating -> viral RNA translated -> RNA dependent RNA polymerase created -> transcription of mRNA -> viral capsid proteins translated
48
Where does genome replication occur in +dsRNA virus?
Within capsid - not cytoplasm Then mRNA template released and translation happens in cytoplasm
49
What type of virus forms cytoplasmic inclusion bodies?
Positive sense RNA viruses
50
Name 6 negative sense RNA viruses
Influenza viruses Always bring polymerase or fail replication ``` Arenavirus Bunyavirus Paramyxovirus Orthomyxovirus Filovirus Rabdoviruses ```
51
What is the first thing negative sense RNA viruses have to do?
Transcribe to positive sense mRNA template by a viral intravirion transcriptase
52
Once a negative sense virus has coded for +mRNA, what is produced first, and what combines to form progeny virus?
Early viral proteins (RNA polymerase) -> progeny viral (-)sense RNA Late viral proteins -> structural proteins Structural proteins + (-) sense RNA assembled to form progeny virus
53
What is cap snatching and what virus does this?
Viral RNA dependent RNA polymerase cleaves 5' capped host mRNAs to prime viral RNA synthesis Influenza A
54
How do negative sense viruses replicate?
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
What is one example of a retrovirus?
HIV
56
How do retroviruses replicate? (4 steps)
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
What is canine parvovirus dependent on to replicate in a host?
Dividing crypt cells
58
What is the incubation for parvo?
3-7d
59
What can parvo survive in?
pH 3-9 | 56-80 degrees for 1 hour
60
What kills parvo?
Formaldehyde and chloramines
61
Is parvo enveloped or non-enveloped?
Non-enveloped - can survive in environment
62
What are 4 factors affecting result of viral infection?
NUmber of particles + virulence Speed of replication and spread to target organs Degree of cellular damage Effectiveness of host defence
63
What are 3 latent infections?
Herpes zoster Chicken pox Shingles
64
Where are localised lesions limited to?
Sites of entry of virus | Skin, respiratory tract, alimentary tract
65
What is cell tropism and what are 2 examples?
Viruses having affinity for particular tissues Rabies - neurotropic BVDV - lymphoid tissues May have primary, secondary or tertiary phases of replication in other organs
66
What is an immunopathologic disease?
Antibodies or lymphocytes aggravate viral infections by contributing to destruction Equine infectious anaemia
67
What happens the second time of infection with dengue haemorrhagic fever?
Cytokine storm | Antibody dependent enhancement of viral infection - helps virus bind to Fc receptors on monocyte
68
What is a self-associated molecular pattern?
A "dont eat me" pattern the virus makes to protect against phagocytosis BVDV E2 protein - allows infected cells to be recognised as self
69
What are 3 examples of slow infections?
Rabies Caprine arthritis encephalitis virus Feline leukaemia These are all retroviruses
70
What is rabies, what does it do and how many types are there?
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
What does canine arthritis encephalitis virus cause?
PI in monocyte lineage monocytes carry genome, replicate after they leave circulation and mature into macrophages Replication in mammary gland and lung
72
What 3 viruses cause proliferative lesions and what do they attack?
Papillomavirus Poxvirus Herpesvirus Target G0/G1 or G2/M checkpoints
73
What causes viral induced neoplasia?
Papillomaviruses Retroviruses Herpesviruses Cervical cancer
74
What do papillomaviruses cause?
No cell death, inflammation or viremia | Supress type I interferon to bypass immune system
75
How to papilloma viruses infect?
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
What are 5 factors affecting transfer and persistence of virus infections?
``` Resistence to environment Mode of transmission Mutations Multiple hosts Persistent Infection ```
77
What are 3 characteristics of a non-enveloped virus?
More resistant to environment Transmission less dependent on close contact Smaller populations needed to maintain infection
78
what are 3 characteristics of enveloped virus?
Inactivated outside animal host Survival depends on close contact Transmission best in density
79
How does west nile virus spread?
Mosquito vectors
80
How does akabane virus spread?
Culicoides species potent teratogen in cattle, sheep and goats Causes target areas to be neuron deficient
81
When does akabane virus cause lesions?
<70d -> resorption or normal calf 76-104d - absence of cerebral hemispheres 103-174d - loss of ventral horn neurons Perinatal - encephalomyelitis
82
How does antigenic shift occur?
Poymerases make mistakes in viruses causing small mutations Can eventually make new strains with different genome
83
What type of virus causes intranuclear inclusion bodies?
dsDNA enveloped virus
84
What is inclusion body rhinitis?
Caused by cytomegalovirus (dsDNA enveloped) - damages respiratory epithelium causing ulceration and inflammation nuclear inclusion bodies - replicate in nucleus
85
What are 6 ways we can demonstrate characterisitc lesions?
``` Inclusion bodies Virus isolation PCR Demonsrating viral antigen Immunofluorescence Latex agglutination ```
86
How do we PCR RNA viruses?
Convert to DNA first
87
How do we demonstrate viral antigens?
Within lesions - transmission electronmicroscopy or immunohistochemistry (RAT) Polycloncal antibodies Monoclonal antibodies - targets one epitope of virion
88
How does latex agglutination work?
Coloured latex spehres coated with viral antibodies to detect antigens (or other way around)
89
What are 4 serology methods?
Agar-gel immuno-diffusion (not sensitive) Haemagglutination Doubling dilutions Haemagglutination inhibition
90
What is an ELISA?
Enzyme linked immunosorbant assay antibody onto plate, antigen attaches Colour change occurs
91
What are 4 types of vaccines?
1. Live 2. Inactivated 3. Subunit virus vaccines 4. DNA virus vaccines
92
What are 4 types of live vaccines?
1. Live pathogenic 2. Live attenuated 3. Heterologous 4. Recombinant
93
How do heterologous vaccines work?
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
What is a live recombinant virus?
Gene for immunogenic protein from one pathogenic virus inserted into another non-pathogenic virus
95
3 advantages of live vaccines
Good immune response that is long lived 1 dose required cheap
96
3 disadcanages of live vaccines
Danger of reversion to virulence Severe disease risk in immunocompromised vaccine must remain alive (storage hard)
97
How are inactivated vaccines prepared?
Virus grown in vitro and inactivated with chemicals (formaldehyde or B-propiolactone) Mixed with oil for slow release and long lasting immunity
98
Disadvantages of killed vaccines
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
Advantages of killed vaccines
Cant cause disease | Easier to store
100
What are 3 examples of adjuvants
Aluminium salts (good antibody, poor CMI response) Liposomes and immunostimulating complexes Complete freunds adjuvant
101
List 4 types of innovative vaccines
DNA vaccine mRNA vaccine Subunit vaccine Virus vector vaccine All code for antigens
102
How are subunit virus vaccines made?
By fractionation of whole virus preparations | Antigens produced using recombinant DNA technology
103
How do DNA virus vaccines work?
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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