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BMS 622 Exam 3 > Lecture 12: Viruses, Pathogenesis, Role, Diagnosis - Chap 36, 37, 38, 39 > Flashcards

Lecture 12: Viruses, Pathogenesis, Role, Diagnosis - Chap 36, 37, 38, 39 Flashcards

1
Q

Who proposed the term ‘virus’ in the 1890s?

A

Louis Pasteur.

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2
Q

What discovery did Ivanovski and Beijerinck make about viruses?

A

They found that a disease in tobacco was caused by a virus (filterable agent).

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3
Q

What is the general size range for viruses?

A

20 to 200 nm.

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4
Q

What is a nucleocapsid?

A

The capsid and nucleic acid together.

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5
Q

What term describes a fully formed virus capable of infection?

A

Virion.

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6
Q

How do enveloped viruses differ from naked viruses in terms of stability?

A

Enveloped viruses are sensitive to drying, acid, and detergents, while naked viruses are more stable.

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7
Q

What is the main function of viral spikes?

A

To attach to host cells and stimulate the immune response.

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8
Q

How do helical and icosahedral capsids differ in structure?

A

Helical capsids are spiral, while icosahedral capsids have a 20-sided structure.

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9
Q

What is a common feature of complex capsids found in bacteriophages?

A

They include tail fibers and a capsid head.

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10
Q

How are enveloped viruses typically released from host cells?

A

By budding or cell lysis.

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11
Q

What role do matrix proteins play in enveloped viruses?

A

They link the envelope to the capsid and help in virus assembly.

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12
Q

What are viral genomes primarily composed of?

A

DNA or RNA, but not both.

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13
Q

Which viruses contain single-stranded DNA as an exception?

A

Parvoviruses.

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14
Q

How do RNA viruses differ from DNA viruses in replication location?

A

RNA viruses generally replicate in the cytoplasm, DNA viruses in the nucleus.

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15
Q

What mechanism do viruses use to ensure survival in the gut environment?

A

Naked capsids, which are resistant to acid and enzymes.

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16
Q

What is the primary function of reverse transcriptase in retroviruses?

A

To convert viral RNA into DNA.

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17
Q

What is the initial step in the viral multiplication cycle?

A

Adsorption, where the virus attaches to the host cell.

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18
Q

During viral penetration, how does an enveloped virus enter a cell?

A

By fusing with the host cell membrane.

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19
Q

What is the purpose of uncoating in viral infection?

A

To release the viral genome into the host cell.

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20
Q

In which part of the host cell are most DNA viruses assembled?

A

In the nucleus.

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21
Q

How do lytic viruses damage their host cells?

A

By replicating and lysing the cell.

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22
Q

What is a latent viral infection?

A

A dormant infection where the virus is present but not actively replicating.

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23
Q

What process allows oncoviruses to transform host cells?

A

By inactivating or altering cell growth suppressors, such as p53.

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24
Q

Which viruses are commonly associated with causing human cancers?

A

HTLV-1, HBV, HCV, HPV 16/18, EBV, and HHV-8.

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25
Q

What are cytopathic effects in viral infections?

A

Visible damage to host cells, such as syncytia and inclusion bodies.

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26
Q

What is syncytia formation in viral infections?

A

Fusion of infected cells to form multinucleated cells.

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27
Q

How can viruses transmit via aerosols?

A

Through respiratory droplets.

28
Q

What type of viruses are transmitted through blood transfusion or organ transplant?

A

Hepatitis B, C, D, HIV, and HTLV-1.

29
Q

How do prions differ from viruses in structure?

A

Prions are misfolded proteins without nucleic acid.

30
Q

What laboratory method is often used to detect viral DNA or RNA?

A

PCR.

31
Q

What are the basic structural components of viruses?

A

Capsid, nucleic acid (DNA or RNA), and sometimes an envelope with spike proteins

32
Q

How does a viral capsid protect the virus?

A

Provides a rigid outer shell that protects viral genetic material and aids in host cell attachment

33
Q

What roles do spike proteins play in viral infection?

A

Aid in cell attachment, immune evasion, and sometimes enzymatic functions (e.g., neuraminidase in influenza)

34
Q

Differentiate between naked and enveloped viruses in terms of stability.

A

Naked viruses are more stable, surviving acidic conditions and drying; enveloped viruses are labile, sensitive to drying and detergents

35
Q

Describe the six main stages of viral replication.

A

1) Adsorption, 2) Penetration, 3) Uncoating, 4) Synthesis, 5) Assembly, 6) Release

36
Q

What is adsorption in the viral replication cycle?

A

Attachment of viral spikes to specific receptors on host cell membranes

37
Q

How do viruses enter host cells?

A

By fusion (for enveloped viruses) or endocytosis (for both naked and enveloped viruses)

38
Q

Define viral tropism.

A

The specificity of a virus for a particular host cell type, determined by receptor binding

39
Q

What is tissue tropism, and why is it important?

A

Refers to the preference of viruses for certain tissues or organs, impacting disease severity and symptoms

40
Q

How do lytic infections cause cellular damage?

A

By replicating within and lysing the host cell, releasing new virions

41
Q

What is a non-lytic infection?

A

Infection where viruses replicate without killing the host cell, often releasing virions through budding

42
Q

Give an example of a cytopathic effect (CPE).

A

Syncytia formation in RSV infection, where infected cells fuse into large multinucleated cells

43
Q

How do oncogenic viruses contribute to cancer?

A

By altering host cell genes related to growth (e.g., HPV affecting p53 and RB proteins)

44
Q

What is immune-mediated damage in viral infections?

A

Tissue damage resulting from immune response, such as inflammation from cytokine release

45
Q

List common viral transmission modes.

A

Respiratory droplets, fecal-oral route, bloodborne, and direct contact

46
Q

What are common symptoms of respiratory viral infections?

A

Cough, fever, sore throat, and nasal congestion

47
Q

Describe the typical disease progression for HSV.

A

Starts with skin or mucosal lesions (cold sores), can progress to encephalitis in severe cases

48
Q

How does HIV affect the immune system?

A

Infects and destroys CD4+ T cells, leading to immunodeficiency

49
Q

Which laboratory technique is commonly used to detect viral RNA?

A

PCR (Polymerase Chain Reaction)

50
Q

What is the purpose of serology in viral diagnostics?

A

To detect antibodies against specific viruses, indicating current or past infection

51
Q

How is immunofluorescence used in viral diagnosis?

A

Detects viral antigens in infected tissues or cells using fluorescent antibodies

52
Q

Define the term ‘viremia.’

A

Presence of viruses in the bloodstream, often spreading infection to secondary sites

53
Q

Describe the cytokine response in viral infections.

A

Release of cytokines like TNF and IL-1, which induce fever and inflammatory symptoms

54
Q

What role does humoral immunity play in viral defense?

A

Production of antibodies that neutralize viruses and mark them for destruction by phagocytes

55
Q

How do viruses evade the immune system?

A

Through methods like antigenic variation, hiding in host cells, or producing immune-modulating proteins

56
Q

What is a cytokine storm, and how does it relate to viral infections?

A

An excessive immune response that causes tissue damage, seen in severe viral infections like SARS

57
Q

Name a common method for diagnosing herpesvirus infections.

A

Observation of syncytia or inclusion bodies in infected tissue samples

58
Q

How do viruses utilize host cell machinery for replication?

A

By redirecting host enzymes and ribosomes to synthesize viral proteins and genomes

59
Q

What is antigenic drift, and in which viruses is it common?

A

Minor mutations in viral genes over time, common in influenza viruses, causing seasonal variation

60
Q

Describe the mechanism of viral latency.

A

Virus remains dormant in host cells, reactivating under certain conditions without immediate symptoms

61
Q

How does the immune system control latent viral infections?

A

Through cytotoxic T cells and memory B cells that target reactivated viruses

62
Q

What is a viral oncogene?

A

A viral gene that can transform host cells and promote uncontrolled cell growth

63
Q

List viruses associated with hemorrhagic fevers.

A

Ebola, Marburg, and Dengue viruses

64
Q

Describe viral encephalitis and a common causative agent.

A

Brain inflammation caused by viruses like HSV-1, leading to fever, headache, and seizures

65
Q

What diagnostic technique is used for chronic hepatitis virus infections?

A

Serology for hepatitis B surface antigen (HBsAg) and hepatitis C antibodies (anti-HCV)

BMS 622 Exam 3 (12 decks)

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