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Virology > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

How have viruses evolved

A

By different independent routes

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2
Q

What do RNA viruses proceed

A

DNA viruses

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3
Q

Why do errors accumulate rapidly with RNA

A

Not subject to proof reading

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4
Q

What are known especially in influenza viruses (2)

A
  1. Antigenic drift

2. Antoigenic shift

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5
Q

What is the reason for spontaneous mutations

A

Error rate of enzymes - in RNA dependent polymerase is much higher than that for DNA dependant polymerase

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6
Q

What are Quasispecies

A

Different isolates of the same species/serotype

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7
Q

What is FMDV known for

A

Mutations and quasispeices

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8
Q

The productions of quasi species may assist with?

A

the virus to persist in the individual host

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9
Q

What is antigenic drift?

A

Viruses will slowly accumulate point mutations

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10
Q

What can spontaneous point mutations lead to

A

Serologically detectable differences - response of the immune system

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11
Q

What is antigenic shift?

A

The dramatic changes which accompany reassortment of viruses with segmented genomes

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12
Q

What are viral mutations

A

Reassortment/antigenic shift

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13
Q

What do pigs have receptors for

A

Both Human and avian viruses

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14
Q

Where is gene reassortment important

A

Segmented viruses

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15
Q

What is recombination

A

A physical interaction of viral genomes in co-infected cells

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16
Q

When does recombination occur

A

When a host cell in infected with two parent viruses

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17
Q

When do conditional lethal mutants replicate

A

Under norma physiological environmental conditions, but not under others

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18
Q

When do temperature sensitive mutants replicate

A

Under normal physiological temperature but stop with Tm changes

19
Q

What does attenuated mutants mean

A

Lost ability to cause disease in humans/animals

20
Q

Where are attenuation and attenuated mutants used

A

In vaccines

21
Q

What is a defective virus

A

A virus will not produce the formation of live, active progeny. This type of infection is called an abortive infection and the reason for this

  • The host cell is defective
  • The virus itself that is defective and cannot replicate
22
Q

What do defective viruses do

A

Block adsorption receptors of cells for infective viruses

23
Q

What is pathogenesis

A

Mechanism of disease development - the process by which a viral infection leads to disease

24
Q

What is pathogenicity

A

The ability of microorganisms to produce disease in a host

25
Q

What is virulence

A

the degree of pathogenicity

26
Q

What are the 6 prerequisites for pathogenicity

A
  1. Gain entry to host
  2. Colonize
  3. Enter the tissues
  4. Multiply
  5. Resist or interfere with the host’s defence mechanisms
  6. Cause damage
27
Q

What is essential for viruses to enter a cell

A

Receptor attachment

28
Q

How can a virus enter (6)

A
  1. Respiratory system
  2. Conjunctiva and other mucous membranes
  3. Digestive system
  4. Urogenital system
  5. Mechanical - skin injury
  6. Transpacental
29
Q

What are cell receptors for viruses

A

Attachment sites

30
Q

What are cell transcription factors

A

Recognise viral promoters and enhancer sequences

31
Q

How is a virus released from host cell (4)

A
  1. Skin
  2. Respiratory tract
  3. Digestive tract
  4. Genital tract, urinary tract, saliva, milk and blood
32
Q

Why do viruses try to evade the host’s immune response

A

To enable them to persistently infect their host

33
Q

What does restricted gene expression mean

A

Replication only takes place in a limited population of cells

34
Q

What does viral-induced immunosuppression mean

A

Viruses destroy immunocompetent cells such as machrophages, neutrophils and lymphocytes

35
Q

What is immunological tolerance

A

In prenatal infections, the infected host may not recognise the foreign virus and therefore, antiviral antibodies are not produced

36
Q

List 5 mechanisms of viral persistence

A
  1. Restricted gene expression
  2. Viral-induced immunosupression
  3. Immunological toerange
  4. Non-immunogenicity
  5. Stimulation of the production of non-neutralising antibodies or defective cell mediated immunity
37
Q

What are 4 consequences of persistence

A
  1. Chronic viral infection
  2. Slow viral infections
  3. Oncogenic viral infections
  4. Latent viral infections
38
Q

What is a quasispecies

A

different isolates of the same species/serotype

39
Q

How does a live virus work

A

They grow the virus in a different host so it is a weaker strength.

40
Q

Where do most viruses go

A

Lymph nodes

41
Q

When will viruses leave the blood stream

A

When they reach a target organ where they do the most damage

42
Q

What is a latent infection

A

May persist in a specialised group of cells

43
Q

What is immunological tolerance

A

When the virus crosses the placenta, the virus is seen as self to the immune system so it doesn’t pick it up.

Virology (23 decks)

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