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

Question 1

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

Answer 1

Louis Pasteur.

Question 2

What discovery did Ivanovski and Beijerinck make about viruses?

Answer 2

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

Question 3

What is the general size range for viruses?

Answer 3

20 to 200 nm.

Question 4

What is a nucleocapsid?

Answer 4

The capsid and nucleic acid together.

Question 5

What term describes a fully formed virus capable of infection?

Answer 5

Virion.

Question 6

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

Answer 6

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

Question 7

What is the main function of viral spikes?

Answer 7

To attach to host cells and stimulate the immune response.

Question 8

How do helical and icosahedral capsids differ in structure?

Answer 8

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

Question 9

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

Answer 9

They include tail fibers and a capsid head.

Question 10

How are enveloped viruses typically released from host cells?

Answer 10

By budding or cell lysis.

Question 11

What role do matrix proteins play in enveloped viruses?

Answer 11

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

Question 12

What are viral genomes primarily composed of?

Answer 12

DNA or RNA, but not both.

Question 13

Which viruses contain single-stranded DNA as an exception?

Answer 13

Parvoviruses.

Question 14

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

Answer 14

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

Question 15

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

Answer 15

Naked capsids, which are resistant to acid and enzymes.

Question 16

What is the primary function of reverse transcriptase in retroviruses?

Answer 16

To convert viral RNA into DNA.

Question 17

What is the initial step in the viral multiplication cycle?

Answer 17

Adsorption, where the virus attaches to the host cell.

Question 18

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

Answer 18

By fusing with the host cell membrane.

Question 19

What is the purpose of uncoating in viral infection?

Answer 19

To release the viral genome into the host cell.

Question 20

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

Answer 20

In the nucleus.

Question 21

How do lytic viruses damage their host cells?

Answer 21

By replicating and lysing the cell.

Question 22

What is a latent viral infection?

Answer 22

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

Question 23

What process allows oncoviruses to transform host cells?

Answer 23

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

Question 24

Which viruses are commonly associated with causing human cancers?

Answer 24

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

Question 25

What are cytopathic effects in viral infections?

Answer 25

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

Question 26

What is syncytia formation in viral infections?

Answer 26

Fusion of infected cells to form multinucleated cells.

Question 27

How can viruses transmit via aerosols?

Answer 27

Through respiratory droplets.

Question 28

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

Answer 28

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

Question 29

How do prions differ from viruses in structure?

Answer 29

Prions are misfolded proteins without nucleic acid.

Question 30

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

Answer 30

PCR.

Question 31

What are the basic structural components of viruses?

Answer 31

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

Question 32

How does a viral capsid protect the virus?

Answer 32

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

Question 33

What roles do spike proteins play in viral infection?

Answer 33

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

Question 34

Differentiate between naked and enveloped viruses in terms of stability.

Answer 34

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

Question 35

Describe the six main stages of viral replication.

Answer 35

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

Question 36

What is adsorption in the viral replication cycle?

Answer 36

Attachment of viral spikes to specific receptors on host cell membranes

Question 37

How do viruses enter host cells?

Answer 37

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

Question 38

Define viral tropism.

Answer 38

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

Question 39

What is tissue tropism, and why is it important?

Answer 39

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

Question 40

How do lytic infections cause cellular damage?

Answer 40

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

Question 41

What is a non-lytic infection?

Answer 41

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

Question 42

Give an example of a cytopathic effect (CPE).

Answer 42

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

Question 43

How do oncogenic viruses contribute to cancer?

Answer 43

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

Question 44

What is immune-mediated damage in viral infections?

Answer 44

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

Question 45

List common viral transmission modes.

Answer 45

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

Question 46

What are common symptoms of respiratory viral infections?

Answer 46

Cough, fever, sore throat, and nasal congestion

Question 47

Describe the typical disease progression for HSV.

Answer 47

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

Question 48

How does HIV affect the immune system?

Answer 48

Infects and destroys CD4+ T cells, leading to immunodeficiency

Question 49

Which laboratory technique is commonly used to detect viral RNA?

Answer 49

PCR (Polymerase Chain Reaction)

Question 50

What is the purpose of serology in viral diagnostics?

Answer 50

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

Question 51

How is immunofluorescence used in viral diagnosis?

Answer 51

Detects viral antigens in infected tissues or cells using fluorescent antibodies

Question 52

Define the term 'viremia.'

Answer 52

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

Question 53

Describe the cytokine response in viral infections.

Answer 53

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

Question 54

What role does humoral immunity play in viral defense?

Answer 54

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

Question 55

How do viruses evade the immune system?

Answer 55

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

Question 56

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

Answer 56

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

Question 57

Name a common method for diagnosing herpesvirus infections.

Answer 57

Observation of syncytia or inclusion bodies in infected tissue samples

Question 58

How do viruses utilize host cell machinery for replication?

Answer 58

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

Question 59

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

Answer 59

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

Question 60

Describe the mechanism of viral latency.

Answer 60

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

Question 61

How does the immune system control latent viral infections?

Answer 61

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

Question 62

What is a viral oncogene?

Answer 62

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

Question 63

List viruses associated with hemorrhagic fevers.

Answer 63

Ebola, Marburg, and Dengue viruses

Question 64

Describe viral encephalitis and a common causative agent.

Answer 64

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

Question 65

What diagnostic technique is used for chronic hepatitis virus infections?

Answer 65

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