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Pathology > Viruses > Flashcards

Viruses Flashcards

1
Q

what type of agents are viruses

A

sub cellular & infectious

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2
Q

what type of parasites are viruses

A

obligate intracellular parasites

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3
Q

as parasites, what do viruses need to do in order to replicate

A

need to invade other (host) cells

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4
Q

what size are viruses

A

20-300nm (small)

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5
Q

what do viruses depend on to independently replicate and grow to synthesise their own nucleic acid or protein

A

a host cell

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6
Q

what of the host cell do viruses take advantage of

A

metabolic machinery to create progeny virions

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7
Q

what do a broad variety of viruses contribute to

A

human disease

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8
Q

which microscope is needed to view viruses

A

electron

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9
Q

what does the basic structure of a virus consist of

A

a capsid surrounding a viral genome

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10
Q

what is the genome and capsid together referred to as

A

nucleocapsid

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11
Q

what is the capsid

A

a protein shell composed of repeating sub units called capsomeres

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12
Q

what does the capsid enclose

A

the nucleic acid

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13
Q

what is a preferred capsid morphology

A

icosohedral symmetry (20 equalateral triangular faces)

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14
Q

what is the glycoprotein which surrounds the virus cell

A

the capsid in addition to a plasma membrane around

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15
Q

what are the glycoproteins sticking out of

A

the plasma membrane, so virus has a membrane coat as well as a protein shell

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16
Q

what is the glycoprotein made out of

A

small protein sub units

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17
Q

what alternative morphologies exist of viruses

A
  • helical nucleocapsid
  • other virus families are surrounded by a lipid envelope (derived from the host cell membrane). the envelope is studded with glycosylated transmembrane proteins
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18
Q

what are the lipid envelopes which surround some virus families derived from

A

the host cell membrane

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19
Q

what can the viral genome be composed of

A
  • DNA double strand
    or
  • RNA single strand or double strand
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20
Q

what can viruses be classified according to

A

their genome type and replication strategy

baltimore classification

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21
Q

which groups of DNA viruses usually enter the host nucleus before they can replicate

A

groups: 1, 2 & 6

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22
Q

give example of double stranded DNA viruses

A
  • adenovirus

- herpes virus

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23
Q

give an example of a single stranded DNA virus

A

parvovirus

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24
Q

give an example of a double stranded DNA reverse transcriptase (RT) virus

A

hepatitis B

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25
Q

how does the double stranded DNA reverse transcriptase virus, hepatitis B replicate

A

replicates through a single stranded RNA intermediate

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26
Q

which RNA viruses usually replicate in the cytoplasm

A

3, 4, 5 & 6

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27
Q

what can single stand RNA viruses replicate through

A
  • either a +ve sense nucleotide sequence which can access ribosomes directly
    or
  • -ve sense which must be transcribed into a readable +ve sense strand form before transcription
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28
Q

what is a -ve sense strand

A

the complementary base pairing of the messenger RNA sequence (sense strand) of a nucleotide

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29
Q

what single strand RNA viruses replicate through a DNA intermediate

A

HIV

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30
Q

what do double stranded RNA replicate via

A

+ve sense RNA

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31
Q

list the RNA viruses which infect humans

A
  • picornavirus
  • astrovirus
  • calicivirus
  • flavirus
  • togavirus
  • reovirus
  • orthomyxovirus
  • bunyavirus
  • retrovirus
  • coronavirus
  • arenavirus
  • filovirus
  • rhabdovirus
  • paramyxovirus
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32
Q

list the DNA viruses which infect humans

A
  • parvovirus
  • hepadnavirus
  • papovavirus
  • adenovirus
  • iridovirus
  • herpesvirus
  • poxvirus
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33
Q

what do RNA viruses which infect humans always have in their structure

A

always has a bit of nucleic acid in the middle, which is protected & surrounded by a protein core called a protein capsid (protein membrane)

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34
Q

list the different types of respiratory viruses

A
  • adenovirus (respiratory tract infections)
  • parainfluenza virus (pharyngitis/sore throat)
  • rhinovirus (tonsilitis and sinus infection)
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35
Q

name a type of retrovirus

A

HIV (AIDS)

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36
Q

what is the virus of warts called

A

papovirus

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37
Q

give an example of pox virus

A

small pox

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38
Q

give an example of a hepatitis virus

A

hepatitis A-E (liver dysfunction)

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39
Q

how does a retrovirus get incorporated into a cell geno

A

it starts off in RNA virus and contains an enzyme called reverse transcriptase which converts RNA into DNA which can get incorporated into the cell geno

40
Q

list the viruses which are childhood diseases

A
  • rubella
  • rubeola (measles)
  • mumps
41
Q

what is the herpes virus in children known as

A

chicken pox

42
Q

what is herpes virus in adults known as

A

shingles

43
Q

list the different types of herpes virus

A
  • HSV-1
  • HSV-2
  • CMV
  • EBV
  • VZV
44
Q

what comes under the VZV herpes virus

A
  • cold sores
  • gladular fever
  • lymphomas
  • shingles
  • acute CNS infections
45
Q

what does the first stage of viral infection involve and what are the different strategies

A

entry into the cell via:

  • attachement
  • translocation
  • genome insertion (naked virus)
  • membrane fusion (enveloped virus)
  • endocytosis and endosome formation (enveloped virus)
46
Q

how does translocation occur, as a strategy of the virus entering into the cell

A

virus binds to cell membrane and remains the same

47
Q

how does genome insertion (naked virus) occur, as a strategy of the virus entering into the cell

A

capsid merges with the cell and releases its geno inside the cell

48
Q

how does membrane fusion (enveloped virus) occur, as a strategy of the virus entering into the cell

A

virus already has a lipid coat on the outside & blends with the lipid coat of the host cell and then passes on its capsid and nucleic acid inside the host cell

49
Q

what is the viral genome transcribed to form

A

new virions

50
Q

what does translation use

A

host cell machinery

51
Q

during translation which uses the host cell machinery, what are the first proteins to generally be synthesised

A

DNA or RNA polymerases

52
Q

during translation which uses the host cell machinery, where does DNA replication occur

A

in the nucleus

53
Q

during translation which uses the host cell machinery, where does RNA replication occur

A

in the cytoplasm

54
Q

describe the way in which DNA viruses invade a cell and cause an infection to propagate

A
  • virus enters the cell and gets dissociated, where the capsid has dissipated and is destroyed leaving behind the viral DNA
  • which is incorporated into the host cell geno
  • so it goes to the nucleus and gets translocated by the nucleus and is entered into the host cell DNA which instructs cells to produce the various components of the virus
  • so it will direct the synthesis of viral proteins
  • so there are capsids of the viral protein coat and will direct the process of replicating DNA of the viral DNA and they become assembled into the cytoplasm of the host cell
  • and through exocytosis the viral cells are dissipated and leave the cell where they go on to infect other cells
55
Q

what do retroviruses e.g. HIV which are RNA viruses convert their ssRNA into

A

dsDNA

56
Q

where can viral assembly occur within a host cell

A

nucleus or cytoplasm

57
Q

what can viral-induced pathology be a result of

A

direct viral action leading to host cell death

58
Q

how can damage of virus occur

A

due to immune response to viral antigens, where antibodies bind with the virus and stop them from invading the host cell

59
Q

what do natural killer cells on host cells provide

A

an antiviral property

60
Q

how does the T cell surveillance system mechanism work

A
  • cytotoxic T cells can lock onto one of our body cells and have the ability o differentiate normal cells from virally infected cells
61
Q

why can we have a T cell surveillance system

A 
because we have MHC proteins which present antigens to T cells and all of our cells have class one MHC cells on the surface of proteins which function as antigen presentation, which periodically samples proteins from within its cytoplasm and shows them on the surface of the cell and then the T cytotoxic cell comes along and locks onto the MHC complex and is able to differentiate between normal proteins and viral proteins 
so it its a normal protein, it will leave the cell and move along, is its a virally infected cell, it can trigger the destruction of that cell through apoptosis, which is a standard mechanism that all our cells have
62
Q

list the routes from which viruses can be spread

A
  • respiratory droplets (cold/flus, inhaled)
  • faecal-oral (not wash hands and then transferred)
  • parenteral - sharing infected needles, can transfer HIV or hepatitis
  • sexual activity
63
Q

what can be established after a primary infection with some viruses

A

a latent infection

64
Q

give an example of a latent infection

A

herpes virus
when a coldsore goes away, the virus does not go away.
it enters one of the sensory nerves and tracks back to the trigeminal ganglia & sits there in its latent form, to be subsequently activated, so once you acquire that infection, your stuck with it in its latent form and you keep getting secondary infections

65
Q

when can you develop cold sores

A

when you don’t feel well

66
Q

how long does acquiring HIV from the beginning to the end (aids) last

A

10 years

67
Q

what type of symptoms are present during acute stage of HIV

A

flu like symptoms in first 10-16 weeks, virus is at its peak and detectable

68
Q

what occurs during 2-10 years if HIV

A

antibody positive, no clinical symptoms, virus fallen down to base line but is still detectable because the immune system is still functioning normal and able to suppress levels of virus, px may not know they have the disease

69
Q

what occurs 2-3 years after the asymptomatic stage of HIV

A

symptomatic
lymphadenopathy (enlarged lymph nodes), fever, weight loss
CD4+ cells go down & px is susceptible to illnesses as viral levels increase

70
Q

what happens 2+ years after the asymptomatic stage of HIV

A

AIDS

die from opportunistic infections

71
Q

what does the HIV virus only target within the body

A

the T helper cells = CD4+

which help orchestrate the whole of the immune system

72
Q

what happens when CD4+ T helper cells are knocked out

A

we will have a massive immunosuppression

73
Q

what is in vitro propagation in cultured cells

A

cells can be fixed and screened for infection

74
Q

what can serological tests screen for

A

anti-viral antibodies

75
Q

what can be used for molecular diagnosis

A

PCR and hybridisation techniques

76
Q

what does diagnostic virology do

A

checks antibodies in blood

77
Q

give an example of an antiviral agent

A

virucides e.g. detergents, chloroform uv light

78
Q

what can anti viral agents target

A

specific components of the viral life cycle e.g.

  • attachment
  • penetration of virus into cell
  • inhibition of replication of virus
79
Q

how do most HIV drugs work

A

inhibition of replication of virus

80
Q

what does the drug interferon do as an antiviral agent

A

stimulate the host immune response

81
Q

what anti viral agent can increase long term protection from viruses, and how

A

MMR

active immunisation with subunit or live attenuated viruses

82
Q

how can passive immunity be achieved

A

using high dose antiviral antibodies

83
Q

give an example of a high dose antiviral antibody

A

Varicella zoster

84
Q

what does chlamydia do

A

obligate intracellular pathogens

85
Q

what category does chlamydia fall into

A

is its own category

86
Q

what is chlamydia similar to

A

bacteria

87
Q

how is chlamydia different to bacteria

A

cannot replicate on its own, must penetrate into a cell

88
Q

what are the 3 species of chlamydia which causes human disease

A
  • chlamydia trachomatis
  • chlamydia pneumoniae
  • chlamydia psittaci
89
Q

which species of chlamydia causes, sinusitis, bronchitis and pneumonia

A

chlamydia pneumoniae

90
Q

which species of chlamydia can also cause pneumonia

A

chlamydia psittaci

91
Q

which species of chlamydia causes, urogenital infection, conjunctivitis and trachoma

A

chlamydia trachomatis

92
Q

how can you diagnose chlamydia disease

A

by scraping off and staining the cells to detect the disease

93
Q

what is the infectious agent of chlamydia

A

the elementary body which binds to receptors on host cells

94
Q

what is chlamydia unable to synthesise

A

ATP

95
Q

what is chlamydia responsive to

A

antibiotics

Pathology (20 decks)

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