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

Unit 4 - Part 6 (Virus Replication & Effects) 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

24
Q

True of False:

Naked viruses are released from the host cells by lysis

25
What does the immune system do to abnormal cells that are infected with viruses?
Cells are destroyed | - tissue damage due to inflammation and immune responses
26
Why don't antibiotics work against viruses?
B/c they don't interrupt specific steps in the viral replication cycle
27
Why do antiviral drugs typically LACK broad-spectrum actions?
B/c viruses have very diverse multiplication strategies | - therefore, a drug only works against a single type of virus but not others
28
What stage of viral replication do vaccines act against?
Target the attachment step | - immunized person makes antibodies that block viral attachment to host cells to prevent infection
29
What are the possible effects of viral infections on host cells (4)?
1. Cytopathic effects 2. Cell death 3. Persistent infection 4. Transformation into tumor cells
30
What are two types of infection that can result from viral infections?
1. Chronic infection | 2. Latent infection (can be reactivated = recurrence)
31
What are cytopathic effects (CPE)?
Changes seen in infected cells under the microscope | - could be useful in aiding diagnosis
32
What are inclusion bodies?
Vacuoles in the cytoplasm and/or nucleus of infected cells filled with new viruses and viral components
33
What is the name of characteristic inclusion bodies seen in infected nerve cells caused by rabies virus?
Negri bodies
34
What is an example of a cytopathic effect seen in cells?
``` Inclusion bodies Giant cell (or Syncytium) ```
35
What are giant cells (or syncytium)?
Infected cells fuse with neighbouring cells forming a syncytium to facilitate their spread
36
True or False: | Giant cells have the appearance of a multi-nucleated cells
True
37
True or False: | Lysis of virus infected cells does not have serious consequences
False | - lysis of infected cells could have serious consequences
38
How does the polio virus destroy the nerve cells known as motor neurons
Lysis | Lytic infection
39
What are the serious consequences of polio virus (that is related to lytic infection and muscles)?
- 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
What is the main indication of a chronic infection?
Mature infectious viruses are produced and can be detected in the body at ALL times - chronic hepatitis C
41
How can a chronic infection be spread?
By contact with blood and items contaminated with blood
42
What is the main characteristic of a latent infection?
Viruses "hide" inside a specific body site - virus is NOT detected - shed in body fluids at all times
43
What are two examples of viruses where the causative virus remains latent inside the trigeminal nerve ganglia (not contagious) until reactivation?
1. Varicella Zoster (VZV or chickenpox) | 2. Herpes simplex virus
44
What can viral genomes do during latency?
1. May be carried extra-chromosomally | 2. May integrate into the host cell chromosome as proviruses or proviral DNAs
45
True or False: | HIV has features of both chronic and latent infections
True
46
Depending on the virus, what can reactivate a latent virus (5)?
1. Immunosuppression 2. Aging 3. Malnutrition 4. Stress 5. Exposure to UV light or sunlight
47
What can the reactivation of the HSV (herpes simplex virus) infection lead to (2)?
1. Appearance of new blisters (contagious) | 2. Asymptomatic viral shedding (contagious)
48
What happens during transformation?
Normal cells infected with certain viruses can be transformed into tumor cells due to expression or activation of viral oncogenes (oncogenic viruses)
49
What is an example of an oncogenic virus?
HPV | - human papillomavirus
50
True or False: | Transformation cannot result in integration of viral genes or genomes into the host cell chromosome
FALSE | - transformation CAN result in integration of viral genes or genomes into the host cell chromosome
51
Are normal cells tumorigenic or non-tumorigenic?
Non-tumorigenic
52
Are transformed cells tumorigenic or non-tumorigenic?
Tumorigenic
53
True or False: | Normal cells are immortal
False | - normal cells have a finite life span
54
True or False: | Transformed cells are immortal
True
55
What are the 5 properties of transformed cells?
1. Tumorgenic 2. Immortal 3. Loss of contact inhibition 4. Anchorage independent 5. Growth factor independent
56
What are the 5 properties of normal cells?
1. Non-tumorgenic 2. Finite life span 3. Density dependent growth (contact inhibition) 4. Anchorage dependent 5. Growth factor dependent
57
What are some examples of viruses that lead to cancers (7)?
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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