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Virus Introduction Flashcards

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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
Endocytosis (pinocytosis)
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
26
What is a Virus?
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
27
Virion
``` Complete infections virus particle Nuclei acid (core) and protein coat ```
28
Largest genome
Pandoravirus
29
Human virus vectors
Bats (lyssavirus) Dogs (rabies) Mosquitoes - yellow fever, dengue, zika, chikungunya
30
Icosahedral virus
20 sided 12 corners Nuclei acid contained within
31
Largest virus
Pithovirus
32
Double stranded DNA (dsDNA)
Poxvirus Adenovirus Herpesvirus Hepadnaviruses
33
Attachment
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
LD50
Lethal dose
35
Single stranded DNA (ssDNA)
Parvovirus
36
Cytoplasm assembly
Picornavirus | Poxvirus
37
Virus pathogenesis
Ability for one organism or agent to cause disease in another Symptoms are due to side effects of immune repsonse
38
Uncoating
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
PCR
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
Viral proteins
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
Three stages of viral replication
Initiation of infection Replication and expression of the genome Release of mature virions from the infected cell
42
Plant viruses
Predominantly transmitted by vectors Aphids Whiteflies Leafhoppers
43
Circular DNA
Papilomavirus
44
Naked virus
Always encased in protein (capsid) Capsid made up of capsomeres Spikes (peplomers) can be found
45
Smallest virus
Circoviruses
46
Plaque assays
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
Zoonotic reservoirs
``` 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
Immortal cell lines
``` 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
Detection and diagnosis
``` Electron microscopy Virus assays Cell culture Serological/immunological test Nuclei acid tests ```
50
Anti-sense
Negative sense strands
51
Lytic cycle
Ends in cell lysis and death Follows replication similar to all other viruses Clearing (plaques)
52
TCID50
Tissue culture ID
53
Examples of DNA viruses
Herpesvirus Parvovirus B19 hepatitis B virus (hepadnavirus)
54
Ambi-sense
Mixture of positive and negative sense
55
Segmented DNA
Influenzavirus
56
Three aspects to consider in virus pathogenesis
Direct cell damage Immune activation or suppression damage Cell transformation
57
Nucleus assembly
Adenovirus | Papoviruses
58
Hybridisation analysis
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
Biosynthesis
Genome replication and expression | Occurs according to the type of virus
60
Modes of transmission
Shedding (aerosols, body fluids, contact surfaces, liquids and foods) Injection (including vectors) Horizontal: host-host Vertical: one generation to another
61
Cell transformation
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
Sense
Positive sense strands
63
Linear DNA
Poliovirus
64
Viruses and cancer
First cancer associated with virus - rous sarcoma virus (retroviridae) Oncogenic viruses
65
Classical system - international committee on taxonomy of viruses
Morphology of virus Nuclei acid in the virion Enveloped or non-enveloped Genome architecture
66
Single stranded RNA (ssRNA)
``` Lyssavirus Picornaviruses Togaviruses Orthomyoxovirus Rhabdoviruses Retrovirus ```
67
Translocation
Translocation of entire virus particle across cytoplasmic membrane of the cell Mediated by proteins in the virus capsid and specific membrane receptors

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