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Sem 3: Viro > Virus Quantification + Virus Replication > Flashcards

Virus Quantification + Virus Replication Flashcards

1
Q

Define virus quantification

A

Counts the # of viruses in a specific volume to determine virus concentration

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2
Q

What is a virus titer measuring?

A

lowest conc. of virus that still infects cells

or infectious units per ml of sample

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3
Q

What is a biological quantification test dependent on?

A

the virus particle initiating successful replication cycle

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4
Q

What is a physical quantification test dependent on?

A
  • does NOT depend on any biological activity of the virus particle
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5
Q

What are examples of biological quantification tests?

A
  1. Plaque assay
  2. Pock assay
  3. Various end point titration methods
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6
Q

What are examples of physical quantification tests?

A
  1. Electron microscopy
  2. Hemagglutination
  3. Immuno assays (ELISA)
  4. qPCR
  5. Flow cytometry
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6
Q

What is the most direct method to determine the concentration of virus particles in a sample?

A

Transmission Electron Microscopy (TEM)

** PHYSICAL TEST

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6
Q

Give examples of a physical test that directly counts viral particles in solution

A
  1. TEM
  2. Virus counter 2100
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7
Q

What physical tests are an assessment based on antigen concentration?

A
  1. Hemagglutination assay
  2. Single radial Immunodiffusion (SRID)
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8
Q

What is a plaque?

A

circular zone of necrotic cells surrounded by viable cells in a monolayer

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8
Q

What physical tests are an assessment based on gene expression?

A

qPCR

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8
Q

Which biological test measures the number of virus particles capable of forming plaques per unit volume?

A

Monolayer plaque assay

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8
Q

If a solution has a PFU of 500 pfu/mL, what does this mean?

A

every mL of solution contains enough virus to form 500 plaques

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9
Q

What is a pock?

A

Necrotic area on chorioallantoic membrane (CAM) of embronated egg

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10
Q

Pock assay is a biological or physical test?

A

Biological

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11
Q

Which biological test is a quantitative determination of oncogenic viruses?

A

Transformation assay

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12
Q

What are the units used in a transformation assay?

A

Focus-forming units / mL

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13
Q

What is the endpoint of a quantal assay?

A

Virus dilution that affects 50% of test subjects

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14
Q

What is TCID50?

A

tissue culture infectious dose which will infect 50% of the cell monolayers

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15
Q

Which of the following is not a physical assay for quantification of viruses?

A. ELISA
B. Electron microscopy
C. Pock assay
D. qPCR

A

C. Pock assay - biological

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16
Q

What is a permissive cell?

A

A cell that allows a virus to replicate

cell machinary that supports replication

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17
Q

What is a non permissive cell?

A

A cell that lacks necessary factors for viral replication

Ex: lack of appropriate receptors

18
Q

What is MOI?

A

Multiplicity of Infection

Refers to # of virions added per cell during infection

19
Q

What is the latent period?

A

After uncoating and until just before 1st appearance of EXTRACELLULAR new virus particle

**no extracellular virions are detected at this stage

20
Q

What is eclipse period?

A

After uncoating and until just before 1st appearance of INTRACELLULAR new virus particle

21
Q

What is burst size?

A

of infectious virions released per avg cell

22
Q

What are the steps of virus replication?

A
  1. Attachment
  2. Penetration
  3. Uncoating
  4. Synthesis of viral components
  5. Assembly + maturation
  6. Release in large numbers
23
Q

True or False: Each virus has its own specific receptor(s) on specific host cells

A

TRUE - lock and key!

24
Q

What virus uses more that 1 host cell receptor for attachment?

A

HIV

25
Q

What is a co-receptor?

A

An additional surface molecule on host cells that is required for entry of viruses

26
Q

How do non-enveloped/naked viruses penetrate and the host cell?

A
  1. Receptor mediated endocytosis (most common)
  2. Pore mediated penetration
27
Q

How do enveloped viruses penetrate and uncoat in the host cell?

A

** depends on type of fusion protein

  1. Surface membrane fusion -pH independent fusion protein
  2. Receptor mediated endocytosis - pH dependent fusion protein
28
Q

What are other uncommon methods of entry for viruses?

A

Ab mediated attachment and penetration

** seen in FIP virus

29
Q

What viruses inject their genome into the host cytoplasm through creation of a pore in the host membrane?

A

Non enveloped viruses

**pore mediated penetration

30
Q

How does FIP virus infect the host cell?

A

Antibody mediated attachment and penetration

-enters host macrophage by attaching spike proteins to CD13 receptor on host cell

31
Q

At which phase in viral replication can virions no longer be detected?

A

Viral uncoating

32
Q

What are the functions of the parent virus?

A
  1. Multiple copies for new viruses
  2. Viral proteins for capsid and successful replication
33
Q

What does reverse transcriptase do?

A

Converts viral RNA to cDNA during viral replication

34
Q

How does processing of primary RNA transcript (pre-RNA) occur?

A
  1. Capping- adding 7-methylguanosine to 5’ end
  2. Adding poly-A tail to 3’ end
  3. Splicing
35
Q

What is capping?

A

Addition of 7-methylguanosine to the 5’ end of RNA

36
Q

What is RNA splicing?

A

process that REMOVES INTRONS and JOINS EXONS

37
Q

_____ are the portion of a gene that codes for AA

A

exons

38
Q

________ are the portion of the gene that does not code for AA

A

Introns

39
Q

What is constitutive splicing?

A

all introns are spliced out, all exons are spliced in

40
Q

What is alternative splicing?

A

All introns spliced out, only selected exons are spliced in

41
Q

Where does assembly and maturation of the virus occur?

A
  1. Nucleus
  2. Cytoplasm
  3. Plasma/cell membrane (most enveloped viruses)
41
Q

What types of viral mRNA are there?

A
  1. Monocistronic - mRNA that encodes 1 polypeptide
  2. Polycistronic - mRNA that encodes many polypeptides
42
Q

Where does assembly and maturation take place in most enveloped viruses?

A

Plasma membrane / cell membrane

43
Q

How do naked viruses release progeny of new virions?

A
  1. Lysis of host cell
44
Q

How do enveloped viruses release progeny of new virions?

A

Budding + exocytosis

45
Q

________ viruses can not exit the host cell by budding

A

Naked viruses

bc no envelope

46
Q

___________ integrates viral DNA into the host genome

A

Integrase

47
Q

How do viruses spread from cell to cell?

A
  1. Extracellular spread
  2. Intercellular spread
  3. Nuclear spread of virus genome
48
Q

________ results in rapid virus dissemination, evasion of immune system, and persistent infections

A

Intercellular spread of viral genome

Sem 3: Viro (17 decks)

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