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Y3 IWB > MICROBIOLOGY- How viruses cause disease > Flashcards

MICROBIOLOGY- How viruses cause disease Flashcards

1
Q

Who was responsible for principles of vaccination, pasteurisation and germ theory?

A

Louis pasteur

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2
Q

Who invented the electron microscope?

A

Ruska and knoll in 1931

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3
Q

What are viruses?

A

Simple micro organisms that are not cable of independent existence

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4
Q

What do viruses need to be able to exist?

A
  1. Require a host cell to survive
  2. They enter the host cell and use the host cells energy and mechanism to replicate
  3. Once they have replicated they leave the host cell progeny
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5
Q

Describe the basic viral structure

A
  1. Dna or RNA
  2. Capsid protein
  3. Lipoprotein envelope (only present in some viruses)
  4. Molecules of protein
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6
Q

What is a single virus particle referred as?

A

Virion

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7
Q

What are viruses classified by?

A
  1. The type of nucleic acid they carry (DNA vs RNA)

2. The presence or absence of an envelope

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8
Q

Give the 5 steps involved in the viruses life cycle

A
  1. Attachment
  2. Entry
  3. Replication
  4. Assembly
  5. Release
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9
Q

How can the virus enter the body?

A

Can be inhaled, ingested or injected

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10
Q

What determines if a virus can enter the host cell

A

The viral tropism determines if a virus can attach and enter

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11
Q

What does viral tropism mean?

A

It describes if the host cell is passive to the virion and allows it to enter and use its equipment

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12
Q

Which cells can HIV attach to?

A

HIV can only attach to human cells that have a CD4 receptor

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13
Q

Which cells can SARS-CoV-2 attach to?

A

SARS-CoV-2 can only attach to human cells with ACE-2 receptors

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14
Q

What do we mean when we describe a host cell as passive?

A

It contains the whole range of components required by the virus for replication to be completed

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15
Q

What step happens after attachment?

A

Entry into host cell

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16
Q

If the virus attaches does it 100% enter the cell?

A

NO

Efficiency varies from <0.1% to 50%

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17
Q

How do enveloped viruses enter a cell?

A

Enter by membrane fusion or endocytosis

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18
Q

How do non enveloped viruses enter a cell?

A

Entry by endocytosis or penetration (direct injection)

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19
Q

Talk through the basic stages of membrane of fusion

A
  1. Receptor binding
  2. Virus with host membrane fusion
  3. Release of vision content into host cytoplasm
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20
Q

Give an example of a virus that enters via membrane fusion?

A

HIV

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21
Q

After a virus enters the cell what does it need to do?

A

Replicate

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22
Q

How does the virion start the replication process?

A

Once inside the host cell the virus will remove its capsid and exposes its genomes (Nucleic acid)

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23
Q

Can the virus cell uncoat its capsid anywhere in the cell?

A

No
Site of uncoating is specific to the virus
May be cytoplasm or nuclear

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24
Q

What process in host cells to viruses hijack?

A

The process of DNA replication and protein synthesis

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25
Q

Talk through the stages of protein synthesis in humans

A
  1. Transcription of DNA into messenger RNA
  2. Translation of mRNA into Amino
  3. Translocation
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26
Q

What does the replication of viruses depend on?

A

Process depends on the type if nuclei acid the virus has

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27
Q

What is necessary to make viral protein

A

Viral mRNA

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28
Q

What does viral mRNA do?

A
  1. Viral mRNA mimics host mRNA
  2. Uses the host cell machinery to make viral proteins instead of host proteins
  3. New virions are constructed from viral proteins
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29
Q

Which type of viruses can immediately start using host cells processes to translate their protein
Why?

A

Single stranded positive sense RNA viruses
e.g. hepatitis C
This is because their genome is already mRNA

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30
Q

Describe the genome of influenza

A

Single stranded negative sense RNA viruses

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31
Q

What must influenza first make before it can start replicating?

A

Must create mRNA

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32
Q

How does influenza create mRNA?

A
  1. Carries its own enzyme (RNA dependent RNA polymerase)
  2. This enzyme is used to create positive sense RNA (mRNA) through complementary base pairing
  3. mRNA then used to translate proteins
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33
Q

Give examples of proteins needed to create new virions

A
  1. Structural proteins
  2. Enzymes (proteases) to chop up structural proteins into smaller building blocks
  3. Enzymes needed to replication when they invade new host cells
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34
Q

After replicating what does a virus do?

A

Assemble

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35
Q

What happens in the assembly stage of a virus’ life

A

All virus components are transported to a site of assembly and put together

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36
Q

Where are influenza virus proteins and new RNA assembled?

A

Assembles at the cell membrane which then forms a bud

37
Q

After assembling all its proteins what does the virus then need to do?

A

Release itself from the host cell

38
Q

State the 3 ways viruses can leave the host cell

A
  1. Lysis
  2. Exocytosis
  3. Budding
39
Q

What is lysis?

A

Cell splitting apart and dying allowing the virus to be released

40
Q

What is exocytosis

A

When the host cell’s transport system releases virions at surface

41
Q

What is budding?

A

When the virion encloses themselves into host cell membrane

42
Q

Give examples of different routes of infection a virus can take into the host cell

A
  1. Mucosal contact
  2. Parenteral (injection)
  3. Respiratort droplet/ aerosol
  4. Faecal oral
  5. Direct contact (skin)
43
Q

Give examples of viruses that spread through mucosal contact

A
  1. HIV

2. Hepatitis B

44
Q

Give examples of viruses that spread through parenteral (injection)

A
  1. HIV
  2. Hepatitis B
  3. Hepatitis C
45
Q

Give examples of viruses that spread through respiratory droplets / aerosol

A
  1. Influenza

2. COVID 19

46
Q

Give examples of viruses that spread through faecal oral

A
  1. Hepatitis A

2. Norovirus

47
Q

Give examples of viruses that spread through direct skin to skin contact

A
  1. Human papillomavirus
  2. Herpes
  3. Simplex virus
48
Q

What must be present from effective enter of a virus to occur?

A
  1. There must be enough virus present (high infective dose)
  2. Host cell must be accessible, susceptible and permissive
  3. Host immune system must be inadequate or absent
49
Q

How can viruses disrupt the host cells they infect

A
  1. Disruptive cell fusion
  2. Some inhibit host cell protein manufacture
  3. Soem form inclusion bodies inside the cell
50
Q

How does the respiratory syncytial virus disrupt the host cell

A

Produces multinucleate giant cells (called syncytia) which surround host cells and stick together

51
Q

How can inhibition of host cell protein function harm host cells?

A

Causes reduced cell function and cell death

52
Q

How can the formation of inclusion bodies inside the cell harm host cells?

A

Leads to the accumulation of protein / metabolites that damage the cell

53
Q

How do we describe the extent of an infection?

A
  1. Localised

2. Generalised

54
Q

Describe localised infections

A
  1. Typically shorter incubation period
  2. Viruses remain at site of entry
  3. May form focal lesions (eg warts)
  4. May effect large areas of the same mucous membranes
55
Q

Describe generalised infections

A
  1. Longer incubation period
  2. Initial phase of local replication near the site of entry
  3. Generalised through the blood to lymph nodes or via nerves
56
Q

How can generalised infections spread through the body?

A
  1. Through blood to lymph nodes
  2. Via nerves

This allows the virus to reach distant organs

57
Q

List some target organs viruses can affect

A
  1. Skin- rashes
  2. Respiratory tract
  3. Liver
  4. Central nervous system
58
Q

How can the skin be affected by a viral infection?

A

Viral replication can occur in the skin causing rashes

59
Q

Which cells do hepatitis viruses affect

A

Hepatitis viruses have a tropism for hepatocytes (liver cells)

60
Q

How do we describe illness duration

A
  1. Acute

2. Chronic

61
Q

Describe acute infections

A
  1. Present quickly
  2. Can be either mild with spontaneous recovery OR lead to rapid decline and death
  3. Have to be easily transmitted or very infectious
62
Q

What can acute illnesses result in?

A
  1. Mild spontaneous recovery
    OR
  2. Rapid decline and death
63
Q

Why do acute viruses need to be easily transmitted or very infectious?

A

As there shedding time is short

64
Q

Describe chronic illness

A
  1. Infection persists for long period time
  2. The host immune system is unable to fully control the virus
  3. Ongoing viral replication alongside immune response progressively damages host cells over time
65
Q

What is latency

A

When the virus is existing but has not yet replicated or made progeny

66
Q

How is a virus maintained during its latency period?

A

Maintained throughout normal host cell devisions and periodically reactivates

67
Q

Give examples of viruses that have a latency period

A
  1. herpes simplex (cold sores)

2. varicella zoster (shingles

68
Q

How do latent viruses establish latency

A

Establish latency in neurones of the Dorsal root ganglia

69
Q

Some viruses have the potential to induce M______ C______

A

Malignant change

70
Q

How do some viruses induce malignant change

A

They disrupt the normal expression of host cell genes

71
Q

What is Epstein Barr virus associated with?

A

Burkitts lymphoma

72
Q

What malignant consequences can HPV have

A

Oral, cervical and penile cancer

73
Q

What is HHV-8 associated with

A

Kaposis sarcoma in the immunosuppressed

74
Q

List the 4 clinical stages of a virus infection

A
  1. Incubation period
  2. Prodromal period
  3. Specific illness period
  4. Recovery period
75
Q

Describe the incubation period of a virus

A
  1. Asymptomatic

2. Virus attaches and undergoing non production stages of life cycle

76
Q

Describe the Prodromal period of a virus infection

A
  1. Non specific manifestation
  2. Non specific illnesss arises due to virus disseminating through the body
  3. Leads to easy host immune response
77
Q

Describe the specific illness period

A
  1. Specific effects of the virus on target cells

2. Host immune systems immunogenic attack

78
Q

What can we use to treat viruses?

A

Anti virals

79
Q

How do antivirals work

A

They work by blocking different stages of a viruses lifestyle eg penetration, attachment , nucleic acid synthesis etc

80
Q

Which antiviral affect viral attachment and entry

A

Blocked by:

  1. Enfuviritide
  2. Maraviroc
  3. Docosonal
  4. Palivizumab
81
Q

Which antiviral affects virus penetration

A

Interferon alfa

82
Q

Which antiviral affects viral uncoating

A

Blocked by amantadine

rimantadine

83
Q

Which antiviral affects nucleic acid synthesis

A

Blocked by:

  1. NRTIs
  2. NNRTIs
  3. Acyclovir
  4. Fosamet
84
Q

Which antiviral affects late protein synths and processing

A

Protease inhibitors

85
Q

Which antiviral affects viral release

A

Blocked by neuraminidase inhibitors

86
Q

Why is it important to study viruses in dentistry

A
  1. Transmission from patient to dentist

2. Virus may be underlying cause of the pathology toy see in a patient

87
Q

How can viruses transmit from patient to dentist (and vice versa)

A
  1. Respiratory transmission
  2. Percutaneous injuries and blood splashes
  3. Skin to mouth
  4. Aerosal generating producing using high speed devices
88
Q

Give some viruses that may be the underlying cause of the pathology you see in the patient

A
  1. Herpes simplex
  2. Measles
  3. Oral cancer (HPV)
  4. Kaposis sarcoma (HIV)

Y3 IWB (31 decks)

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