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NURS 2228 - Microbiology > Unit 4 - Part 6 (Virus Replication & Effects) > Flashcards

Unit 4 - Part 6 (Virus Replication & Effects) Flashcards

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Biology 101 flashcards
1
Q

What are 6 main steps in a typical viral replication cycle?

A
  1. Attachment (adsorption)
  2. Penetration
  3. Uncoating
  4. Biosynthesis
  5. Assembly
  6. Release
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2
Q

What are some possible reasons that a person develops flu like symptoms days after getting the flu shot (4)?

A
  1. Infected before vaccination
  2. Not enough time to create immunity
  3. Flu-like symptoms doesn’t mean that the person has the flu
  4. Mismatch between vaccine and virus
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3
Q

Define adsorption

A

Also known as: attachment

- how VIRUSES attach to the host’s receptors cells

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4
Q

What is biosynthesis?

A

Most active stage of viral replication

  • hostile takeover
  • trigger host cell to create virus pieces for them
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5
Q

What occurs through specific interactions between their capsid proteins and the host cell membrane receptors?

A

Attachment/adsorption

of naked viruses

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6
Q

What is the adhesion molecule for rhinoviruses?

A

ICAM-1

- on host receptor cells

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7
Q

What can bind to a rhinovirus and prevents attaching to the ICAM-1?

A

Antibodies

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8
Q

What action do antibodies prevent by coating a virus?

blocking ICAM-1

A

Prevents attachment/adsorption

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9
Q

Why do ICAM-1 receptors bind so easily to the capside of the rhinovirus?

A

The structure of the capsid is highly variable

- allows for easy binding of ICAM

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10
Q

What allows an enveloped virus to attach to a host’s receptor cells?

A

Specific glycoprotein spikes on the envelope

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11
Q

What is the name of the spikes on HIV that allows for the attachment to CD4 AND CCR5 on T helper cells in humans?

A

GP 120

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12
Q

What is the mutation that creates resistance to HIV infection?

A

Mutation to CCR5 gene

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13
Q

What else happens (other than resistance to HIV) if a person has a mutation to CCR5 gene?

A

Person will not be able to effectively fight off infections

- CCR5 is a chemical messangeer - attracts leukocytes to infection

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14
Q

What are the two ways that viral penetration can occur by?

A
  1. Fusion - between the viral envelope and the host cell membrane
  2. Endocytosis (or engulfment into a vesicle)
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15
Q

Describe uncoating of a virus

A

Release of viral nuclei acid (from the protein coat)

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16
Q

Define biosynthesis

A

Synthesis of new viral nucleic acids and proteins

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17
Q

What happens during the biosynthesis process?

A
  • Replication of viral genome
  • mRNA synthesis (transcription)
  • production of viral proteins
  • These events depend to a varying degree of certain host-derived and virus-specific replication enzymes
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18
Q

What happens during viral assembly?

A

Newly synthesized viral genome and other components are incorporated into the capsid to form nucleocapsid

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19
Q

At what point in development of viruses, are naked viruses said to be mature (complete and infectious)?

A

During the viral assembly stage

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20
Q

What is the final step in viral replication cycle?

A

Release

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21
Q

True or False:

Mature naked viruses accumulate in the cell, eventually leading to cell death and are released by cell lysis

A

True

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22
Q

How are enveloped viruses released from the host cell?

A

Form nucleocapsid “buds” through the host cell membrane

- pick up phospholipids to produce a mature virus with the envelope

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23
Q

True or False:

Enveloped viruses are released from the host cells by budding/exocytosis

A

True

24
Q

True of False:

Naked viruses are released from the host cells by lysis

A

True

25
Q

What does the immune system do to abnormal cells that are infected with viruses?

A

Cells are destroyed

- tissue damage due to inflammation and immune responses

26
Q

Why don’t antibiotics work against viruses?

A

B/c they don’t interrupt specific steps in the viral replication cycle

27
Q

Why do antiviral drugs typically LACK broad-spectrum actions?

A

B/c viruses have very diverse multiplication strategies

- therefore, a drug only works against a single type of virus but not others

28
Q

What stage of viral replication do vaccines act against?

A

Target the attachment step

- immunized person makes antibodies that block viral attachment to host cells to prevent infection

29
Q

What are the possible effects of viral infections on host cells (4)?

A
  1. Cytopathic effects
  2. Cell death
  3. Persistent infection
  4. Transformation into tumor cells
30
Q

What are two types of infection that can result from viral infections?

A
  1. Chronic infection

2. Latent infection (can be reactivated = recurrence)

31
Q

What are cytopathic effects (CPE)?

A

Changes seen in infected cells under the microscope

- could be useful in aiding diagnosis

32
Q

What are inclusion bodies?

A

Vacuoles in the cytoplasm and/or nucleus of infected cells filled with new viruses and viral components

33
Q

What is the name of characteristic inclusion bodies seen in infected nerve cells caused by rabies virus?

A

Negri bodies

34
Q

What is an example of a cytopathic effect seen in cells?

A 
Inclusion bodies
Giant cell (or Syncytium)
35
Q

What are giant cells (or syncytium)?

A

Infected cells fuse with neighbouring cells forming a syncytium to facilitate their spread

36
Q

True or False:

Giant cells have the appearance of a multi-nucleated cells

A

True

37
Q

True or False:

Lysis of virus infected cells does not have serious consequences

A

False

- lysis of infected cells could have serious consequences

38
Q

How does the polio virus destroy the nerve cells known as motor neurons

A

Lysis

Lytic infection

39
Q

What are the serious consequences of polio virus (that is related to lytic infection and muscles)?

A
  • nerve cell damage (cannot be regenerated)
  • affected muscle cells no longer function
  • irreversible and extensive paralysis involving the trunk, muscles of the chest and abdomen
  • resulting in possibly quadriplegia and death
40
Q

What is the main indication of a chronic infection?

A

Mature infectious viruses are produced and can be detected in the body at ALL times
- chronic hepatitis C

41
Q

How can a chronic infection be spread?

A

By contact with blood and items contaminated with blood

42
Q

What is the main characteristic of a latent infection?

A

Viruses “hide” inside a specific body site

  • virus is NOT detected
  • shed in body fluids at all times
43
Q

What are two examples of viruses where the causative virus remains latent inside the trigeminal nerve ganglia (not contagious) until reactivation?

A
  1. Varicella Zoster (VZV or chickenpox)

2. Herpes simplex virus

44
Q

What can viral genomes do during latency?

A
  1. May be carried extra-chromosomally

2. May integrate into the host cell chromosome as proviruses or proviral DNAs

45
Q

True or False:

HIV has features of both chronic and latent infections

A

True

46
Q

Depending on the virus, what can reactivate a latent virus (5)?

A
  1. Immunosuppression
  2. Aging
  3. Malnutrition
  4. Stress
  5. Exposure to UV light or sunlight
47
Q

What can the reactivation of the HSV (herpes simplex virus) infection lead to (2)?

A
  1. Appearance of new blisters (contagious)

2. Asymptomatic viral shedding (contagious)

48
Q

What happens during transformation?

A

Normal cells infected with certain viruses can be transformed into tumor cells due to expression or activation of viral oncogenes (oncogenic viruses)

49
Q

What is an example of an oncogenic virus?

A

HPV

- human papillomavirus

50
Q

True or False:

Transformation cannot result in integration of viral genes or genomes into the host cell chromosome

A

FALSE

- transformation CAN result in integration of viral genes or genomes into the host cell chromosome

51
Q

Are normal cells tumorigenic or non-tumorigenic?

A

Non-tumorigenic

52
Q

Are transformed cells tumorigenic or non-tumorigenic?

A

Tumorigenic

53
Q

True or False:

Normal cells are immortal

A

False

- normal cells have a finite life span

54
Q

True or False:

Transformed cells are immortal

A

True

55
Q

What are the 5 properties of transformed cells?

A
  1. Tumorgenic
  2. Immortal
  3. Loss of contact inhibition
  4. Anchorage independent
  5. Growth factor independent
56
Q

What are the 5 properties of normal cells?

A
  1. Non-tumorgenic
  2. Finite life span
  3. Density dependent growth (contact inhibition)
  4. Anchorage dependent
  5. Growth factor dependent
57
Q

What are some examples of viruses that lead to cancers (7)?

A
  1. Hep B virus
  2. Epstein Barr virus
  3. Herpes simplex
  4. Human herpes B virus
  5. HPV
  6. Hep C Virus
  7. Human T cell leukemia virus

NURS 2228 - Microbiology (9 decks)

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