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BIOL2416 > Virus Introduction > Flashcards

Virus Introduction Flashcards

1
Q

Helical virus

A

Resemble long rods with hollow centre
Coil of nuclei acid coated with capsid
Rigid (rod-like) or flexible (packed)

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2
Q

Spikes (peplomers)

A

Found predominantly on enveloped viruses
Carbohydrate-protein complex
Virus specific
Mode of attachment and insertion

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3
Q

Complex virus

A

More complicated structure
Examples:
Bacteriophages (some have head, tail, legs)
Pox viruses - no real capsid more like an inner envelope

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4
Q

Fusion

A

Fusion of the virus envelope with the cell membrane, either directly at the cell surface or in a cytoplasmic vehicle
Fusion requires the presence of a fusion protein in the virus envelope which promotes joining of the cell and virus membranes, resulting in the core being deposited directly into the cytoplasm

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5
Q

Virus receptors

A

Immunoglobulin-like superfamily molecules
Membrane associated receptors
Transmembrane transporters and channels

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6
Q

Cell tropism

A

Capacity of virus to infect specific population of cells
Receptor expression on surface of cells determines the tropism of a virus
Initial stage of replication has a major influence on virus pathogenesis and determining the course of a virus infection

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7
Q

Penetration

A

Normally occurs a very short time after attachment of the virus to its receptor in the cell membrane
Energy-dependent process
Three main mechanisms involved:
Translocation, endocytosis or fusion

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8
Q

Release

A

Simple process for lyric viruses (most non-enveloped viruses)- cell breaks open
Enveloped viruses acquire a lipid membrane
Virion envelope proteins are picked up during virus particle release - budding

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9
Q

ID50

A

Infectious dose

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10
Q

Lysogenic cycle

A 
Cell remains alive
Attachment and entry
Integration into host DNA - prophage
Replicates as host divides (latent)
Changes to cell can lead to lytic cycle
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11
Q

Older system of classification:

A 
Tissue or cell type infected
Mode of transmission
Location
Discoverer or discovery
Disease caused
Host range
How disease originated - ‘dengue’ evil spirit, ‘influenza’ influence of bad air
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12
Q

Serological/immunological Tests

A 
Most common viral identification method
Haemagglutination
Haemagglutination inhibition - antiviral antibodies from serum inhibit haemagglutination
Immunostaining
ELISA
Western blot
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13
Q

Growing viruses

A

Living animals - inoculated with viruses that grow in them. Usually requires the animal to be killed
Not all viruses grow in animals
Embryonated eggs
Cell culture - looking for changes caused by viral growth ‘cytopathic effect’

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14
Q

Smallest human pathogen

A

Parvovirus B19

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15
Q

Maturation

A

Stage of the replication cycle at which the virus becomes infectious
Can involve structural changes in the virus particle

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16
Q

Baltimore classification system

A

Alternative classification system to ICTV
System describes relationship between virus and its mRNA
Groups based on requirement for all viruses to direct mRNA in order to replicate
Groups numbered as Roman numerals

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17
Q

Enveloped virus

A

Lipid bi-layer usually acquired from host during budding

Often contains more than 1 protein aiding in binding to cell receptors

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18
Q

Double stranded RNA (dsRNA)

A

Rotavirus

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19
Q

Bacteriophages

A

Viruses that infect bacteria
Grown in bacterial cultures
Replicate via two mechanisms: lyric and lysogenic cycle

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20
Q

Infectious dose/lethal does

A

Determine amount of virus needed to cause infection or death of 50% exposed host cells or organisms -virulence

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21
Q

Primary cell lines

A

Cultured directly from the origin
Requires source of host tissue
Very few generations

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22
Q

Examples of RNA viruses

A

Influenza
Poliovirus
Tobacco mosaic virus

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23
Q

Viral nuclei acid

A

Viruses only ever have DNA or RNA - never together

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24
Q

Assembly

A

Involves the collection of all components necessary for the formation of the mature virion at a particular site in the cell
The basic structure of the virus particle is formed
Site of assembly depends on site of replication and mechanism by which virus is eventually released
Assembly can occur in cytoplasm or nucleus

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25
Q

Endocytosis (pinocytosis)

A

Endocytosis of the virus into intracellular vacuoles
Most common mechanism
Does not require any specific virus proteins
Relies on formation and internalisation of coated pits at cell membrane

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26
Q

What is a Virus?

A

Infectious agent - but do not necessarily cause a specific disease
Living but not living
Produced by assembling pre-formed components
Do not grow or divide
Do not generate energy
Do not synthesise proteins on their own
Obligate intracellular pathogens

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27
Q

Virion

A 
Complete infections virus particle
Nuclei acid (core) and protein coat
28
Q

Largest genome

A

Pandoravirus

29
Q

Human virus vectors

A

Bats (lyssavirus)
Dogs (rabies)
Mosquitoes - yellow fever, dengue, zika, chikungunya

30
Q

Icosahedral virus

A

20 sided
12 corners
Nuclei acid contained within

31
Q

Largest virus

A

Pithovirus

32
Q

Double stranded DNA (dsDNA)

A

Poxvirus
Adenovirus
Herpesvirus
Hepadnaviruses

33
Q

Attachment

A

Consists of specific binding of a virus-attachment protein (or antireceptor) to a a cellular receptor molecule
No energy required
Target receptor molecules may be proteins or carbohydrates

34
Q

LD50

A

Lethal dose

35
Q

Single stranded DNA (ssDNA)

A

Parvovirus

36
Q

Cytoplasm assembly

A

Picornavirus

Poxvirus

37
Q

Virus pathogenesis

A

Ability for one organism or agent to cause disease in another
Symptoms are due to side effects of immune repsonse

38
Q

Uncoating

A

General term for events that occur after penetration
Least studies stage of replication
The product of uncoating depends on the structure of the virus nucleocapsid

39
Q

PCR

A

Oligonucleotide ‘primers’ and raw ingredients to create short sections of DNA
RNA viruses require reverse transcriptase to create complementary DNA (cDNA)
Needs little starting template
Detection - hybridisation probes
Now real-time PCR

40
Q

Viral proteins

A

Most viruses encode for very few proteins - those required for virion assembly
Most viruses contain few enzymes - reliant on host cell mechanisms for replication
Some viruses encode for more proteins - generally non-structural

41
Q

Three stages of viral replication

A

Initiation of infection
Replication and expression of the genome
Release of mature virions from the infected cell

42
Q

Plant viruses

A

Predominantly transmitted by vectors
Aphids
Whiteflies
Leafhoppers

43
Q

Circular DNA

A

Papilomavirus

44
Q

Naked virus

A

Always encased in protein (capsid)
Capsid made up of capsomeres
Spikes (peplomers) can be found

45
Q

Smallest virus

A

Circoviruses

46
Q

Plaque assays

A

Dilutions of virus preparation made and plated in lawn/monolayer of host cells
Number of plaques counted
Results expressed as plaque-forming units
Can be used for:
Animal viruses and bacteriophages

47
Q

Zoonotic reservoirs

A 
Where the source of virus is animals - not to be confused with vectors
Rodents (hantavirus, lasso virus)
Birds (influenza, West Nile virus)
Pigs (influenza)
Bats (Hendra, Nipah viruses)
48
Q

Immortal cell lines

A 
Cells that have acquired immortality through transformation
Can be passages indefinitely
Example HeLa cells
Great for laboratory based research
Not great for vaccine use
49
Q

Detection and diagnosis

A 
Electron microscopy
Virus assays
Cell culture
Serological/immunological test
Nuclei acid tests
50
Q

Anti-sense

A

Negative sense strands

51
Q

Lytic cycle

A

Ends in cell lysis and death
Follows replication similar to all other viruses
Clearing (plaques)

52
Q

TCID50

A

Tissue culture ID

53
Q

Examples of DNA viruses

A

Herpesvirus
Parvovirus B19
hepatitis B virus (hepadnavirus)

54
Q

Ambi-sense

A

Mixture of positive and negative sense

55
Q

Segmented DNA

A

Influenzavirus

56
Q

Three aspects to consider in virus pathogenesis

A

Direct cell damage
Immune activation or suppression damage
Cell transformation

57
Q

Nucleus assembly

A

Adenovirus

Papoviruses

58
Q

Hybridisation analysis

A

Highly specific
Southern (DNA) and northern (RNA) blots
Target NA digested using restriction enzymes
Products separated with electrophoresis
Hybridised with labelled probes specific to target
Probes can be radioactive, fluorescent, colorimetric

59
Q

Biosynthesis

A

Genome replication and expression

Occurs according to the type of virus

60
Q

Modes of transmission

A

Shedding (aerosols, body fluids, contact surfaces, liquids and foods)
Injection (including vectors)
Horizontal: host-host
Vertical: one generation to another

61
Q

Cell transformation

A

Process where cell acquires properties of cancer
Cell transformation is a single-hit process
All or part of the virus genome persists in the transformed cell
Virus genomes found in transformed cells are frequently replication defective
Usually accompanied by continued expression of a limited repertoire of virus genes, rarely by productive infection
Transformation is mediated by proteins encoded by oncogenes

62
Q

Sense

A

Positive sense strands

63
Q

Linear DNA

A

Poliovirus

64
Q

Viruses and cancer

A

First cancer associated with virus - rous sarcoma virus (retroviridae)
Oncogenic viruses

65
Q

Classical system - international committee on taxonomy of viruses

A

Morphology of virus
Nuclei acid in the virion
Enveloped or non-enveloped
Genome architecture

66
Q

Single stranded RNA (ssRNA)

A 
Lyssavirus
Picornaviruses
Togaviruses
Orthomyoxovirus
Rhabdoviruses
Retrovirus
67
Q

Translocation

A

Translocation of entire virus particle across cytoplasmic membrane of the cell
Mediated by proteins in the virus capsid and specific membrane receptors

BIOL2416 (5 decks)

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