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BIO 435: Virology > Review > Flashcards

Review Flashcards

1
Q

What is a virus?

A
  • A virus is a small, infectious, obligate, intracellular parasite
    -
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2
Q

What are the steps of virus lifecycle?

A
  1. Attachment
  2. Penetration
  3. Uncoating
  4. Replication
  5. Assembly
  6. Maturation/processing
  7. Release
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3
Q

What are the methods of viral entry into a host cell?

A

direct fusion

  • virion and envelope fuse to host cell
  • nucleocapsid is released into host cell

endocytosis

  • virion enters host cell and forms vessicle
  • acidification and release of nucleocapsid
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4
Q

Where does viral replication occur?

A

Most RNA viruses replicate in cytoplasm
- except retroviruses and orthomyxoviruses (flu)

Most DNA viruses replicate in nucleus
- except poxviruses

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5
Q

What must viruses do to make proteins?

A

All viruses must express their genes as functional mRNAs early in infection in order to direct the cell’s translational machinery to make viral proteins

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6
Q

How do the different types of DNA viruses make their proteins?

A

dsDNA
- Cellular RNA polymerase => mRNA

ssDNA
- Cellular DNA polymerase => dsDNA => Cellular RNA polymerase => mRNA

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7
Q

How do the different types of RNA viruses make their proteins?

A

(+) ssRNA
- viral genome acts as mRNA

dsRNA
- viral RDRP

(-) ssRNA
- virion RDRP

Retroviruses
- Reverse Transcriptase

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8
Q

What are the two classification systems used for viruses?

A

Classical System

  • genome type: DNA or RNA
  • Capsid type
  • Naked or enveloped

Baltimore Classification System

  • DNA or RNA
  • 7 replication schemes (don’t need to know all 7) just know replication strategy determines classification
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9
Q

What are cytopathic effects?

A

visible signs of infected cells can be observed with inverted light microscopes
- rounding, shrinkage, lysis

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10
Q

What quantitative assays can be conducted for viruses?

A

plaque assay
- take sample and sequentially dilute to determine how many plaques form per volume of sample

hemagglutination assay

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11
Q

What are the Three General Approaches for Laboratory Diagnosis of Viral Infections?

A

Direct detection of viral antigen

  • rabies - bullet shaped
  • smallpox - dumbbell shaped

Virus isolation
- PCR

Serology

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12
Q

What is viral pathogenesis?

A

The mechanism by which a virus causes disease in the host

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13
Q

What are the Six steps that viruses employ to propagate and survive?

A

Enter the cell and translocate the genome to the site of replication

Replicate its genome and produce mRNA

Generate viral proteins

Assemble progeny viruses and then emerge from the cell

Evade host defenses

Disperse and persist in the environment

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14
Q

What are the preferred methods for viruses to gain entry into the host and then target specific cell types?

A 
Respiratory tract (rhinoviruses, influenza)
Gastrointestinal tract
Genital tract
Conjunctiva (eyes)
Skin
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15
Q

What are the general patterns of infection for viruses?

A

Acute Infection
- Quick viral replication and clearance

Persistent Infection
- Prolonged viral load

Latent Infection
- Viral reactivation

Slow virus infection
- HIV

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16
Q

What is the triad model of disease?

A

host

environment

viral pathogen

17
Q

What are the types of immune responses?

A

Nonspecific, innate immunity plays a role shortly after infection and is directed against any virus

Specific immunity requires days to weeks before they are induced or effective in clearing specific viruses

18
Q

What are some requirements of an effective vaccine?

A

Safe

Cost Effective

Provides immunity

19
Q

What stages in the virus lifecycle do antiviral drugs act?

A

Fusion Inhibitors

  • Attachment and entry
  • Enfuviritide

Ion Channel Blockers

  • Uncoating
  • Amantadine and Rimantidine

Polymerase Inhibitors

  • Replication
  • Acyclovir

Protease inhibitors

  • Assembly
  • Saquinavir

Neuraminidase inhibitors

  • Release
  • Zanamivir
20
Q

What is epidemiology?

A

The study of the cause, distribution, control, and prevention of disease in a population

21
Q

What is prevalence vs incidence?

A

Prevalence
- proportion of cases in a population

Incidence
- proportion of new cases

22
Q

What is Endemic, Epidemic, Pandemic?

A

Endemic - localized
Epidemic - nationwide
Pandemic - worldwide

23
Q

What is gene therapy?

A

The introduction of genes into a person’s cells to replace or compensate for defective (mutant) genes that are responsible for a specific disease or medical problem.

The therapeutic (good) genes can be delivered by a customized vector such as a virus.

Using genetically engineered viruses to selectively kill cancer cells

24
Q

What are the applications of gene therapy?

A
  1. Gene replacement/augmentation
  2. Oncolytic virotherapy
  3. Cell marking/re-population of cells
25
Q

What is Gene replacement/augmentation?

A

Especially suited to single gene defects and discrete populations of target cells
e.g., ADA deficiency, cystic fibrosis.

26
Q

What is Oncolytic virotherapy?

A

Direct oncolysis

  • efficient virus replication and lysis of tumor cells
  • ONYX-15 specific lysis of p53-/- cells
Indirect oncolysis (Suicide/toxic genes) 
 - example TK-ACV suicide therapy of tumor cells

Virotherapy + Immune stimulation
- To stimulate the host’s immune system, in particular to cancer cells e.g., HLA genes, immune stimulatory cytokines.

27
Q

What is Cell marking/re-population of cells?

A

For autologous bone marrow transplantation in cancer therapy, X-linked SCID

28
Q

What are the two main ways that viruses transform cells (1st step in cancer development)?

A
  1. By activation of cellular signal transduction cascades
    - Cell cycle overstimulated = “stepping on the gas”
  2. Interference with the cell cycle controls
    - Cell cycle not inhibited = “can’t put on brakes”
    - cell that normally would not be replicating undergoes replication
29
Q

How can we tell that a cancer cell is transformed?

A

Immortal, high saturation density, no need for GF

30
Q

Go over the classification of influenzavirus.

A

Orthomyxoviridae family

3 Types of Influenza: A, B and C

All 3 can infect and cause symptoms in humans, but pandemics caused solely by Type A

31
Q

What are the functions of influenzavirus proteins?

A

PB1, PB2, PA
- Code for RNA polymerase

HA, NA
- code for the surface proteins

M2
- M2 ion channel

32
Q

Go over the influenzavirus lifecycle.

A

Attachment to sialic acid

Endocytic entry

Uncoating and release of vRNPs into cytoplasm

Translocation of vRNPs into nucleus

Generation of mRNA and positive (+) strands and more – strand RNA genomes

Production of viral proteins

Genomes packaged into pre-assembled capsids

Budding and release of progeny virions

BIO 435: Virology (18 decks)

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