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Pathophysiology > Basic Props Of Viruses > Flashcards

Basic Props Of Viruses Flashcards

1
Q

What does viruses infect?

A

Infect all forms of life:

bacteria>> bacteriophage
Plants 
Fungi 
Insects 
Fishes 
Reptiles 
Birds 
Mammals
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2
Q

What is the name of the virus infecting bacteria?

A

Bacteriophage

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3
Q

What is type of viruses

A
  1. Obligate Intracellular Parasites : show living capacity only inside the cell ( host cell ) / must live within the cell

Can infect pro/eukaryotes

  1. Outside a host cell—> inert, no enzyme or other activity.
  2. Inside the host cell —> viral NA takes over the cell and directs it to produce new viruses —> replication
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4
Q

Does viruses have nucleic acids?

A

Yes could be DNA or RNA ( not in the same time )

If it goes inside the host cell it takes up the effective cell machineray of the host cell to produce its own proteins and # —> perform replication —> new virus

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5
Q

What is virion?

A

Basic virus particle that is capable of infecting the host

Intact and infective virus particle

A fully assembled infectious virus with NA and PROTEIN

• At least two components:
Genome
• DNA or RNA

Capsid
• Protective protein coat

Total —> VIRION

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6
Q

What is the size of viruses?

A

Viruses are small in size

E.coli 2 um

Human cell 6-8 um ( 3 - 4 times larger than E.coli )
Viruses are smaller 20 nm - 400 nm —> ( 100 - 1000 times smaller than what they infect ) —> seen by electron microscope ( submicroscopic particles : not seen with light microscope ) —> can’t be removed by filtered sterilization ( remove bacterial particles only but not the viral particles )

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7
Q

What is the largest size of a virus and what is its name ?

A

Smallpox (poxvirus, 400 nm) a large virus is at the limit of resolution of the light microscope

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8
Q

What is Armstrong?

A

10 to the power of - 10

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9
Q

What is the limit of filter sterilization?

A

200 nm is the filter action limit

> 200 nm will be removed by sterilization

<200nm cannot be removed by filter sterilization

Most of the viruses are beyond the limit —> if filtered —> mostly will monotonous be removed —> go in the filtrate

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10
Q

What is the genetic material of viruses

A
  1. DNA or RNA
  2. Single-stranded or double-stranded
  3. Linear or circular
    • ( sense strand ) or - ( non-sense strand )
  5. Single or multiple pieces
  6. Few genes : 3 - 100’s —> don’t have genes for energy production
  7. Small genome size examples in diff organisms:
    A. Parvovirus : 5 kB
    B. Poxvirus : 250 kB
    C. E.coli: 5 MB
    D. Humans : 3.2 Bb
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11
Q

What are the 3 types of DNA viruses ?

A
  1. ssDNA, linear: Parvovirus
  2. dsDNA, circular: Papovavirus
  3. dsDNA, linear: Adenovirus, Herpes virus, Poxvirus, Hepadnavirus
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12
Q

What are the 4 types of RNA viruses ?

A

•1. ssRNA, sense (+) strand: picornavirus, calicivirus,
togavirus, coronavirus

  1. ssRNA, antisense (_) strand: bunyavirus, orthomyxovirus,
    arenavirus, filovirus, rhabdovirus, paramyxovirus
  2. ssRNA 2 copies: Retrovirus
  3. dsRNA, 10-12 segments: Reovirus
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13
Q

What are the types of viruses depending on structure ?

A 
1. Naked (Non-enveloped): e.g. 
Hepatitis A
virus (HAV), 
Hepatitis E virus (HEV),
Norovirus, 
Parvovirus, etc. 
( genome + capsid but NO envelope )
2. Enveloped: e.g. 
Human immunodeficiency virus (HIV), 
Herpes simplex virus (HSV),
Hepatitis B virus (HBV),  
Influenza
viruses, etc.
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14
Q

What are the simplest viruses?

A

Naked viruses —> naked nucleocapsid —> ( to remember —> the VIRION is the virus that can infect host cells and contains NA + capsid )

  1. Capsid —> protein coat —> protectects the genome against nucleases that can digest RNA and DNA
  2. NA —> genetic material inside the capsid
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15
Q

What is the capsid formed of?

A
  1. Protein in nature

2. Many identical protein subunits —> capsomere

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16
Q

How does capsid determine the viral shape?

A
  1. Isometric / icosahedral
  2. Helical
  3. Some more complex —> helical and isometric together —> most bacteriophages are complex viruses
17
Q

How can naked viruses attach?

A

By attaching proteins —> proteins that help the virus infect the cell —> Spikes

18
Q

What is nucleocapsid?

A

NA + CAPSID

19
Q

What are the enveloped virus characteristics?

A

A. Genetic material

B. Protein coat

C. Envelope:

  1. Phospholipid bilayer
  2. External to nucleocapsid
  3. Attach through spikes to the host cell

D. Matrix protein between envelope and nucleocapsid —> maintain Virion structure

20
Q

What are the additional comp in some viruses?

A

They are Enzymes:

  1. Present in some viruses
  2. Coded by the virus NA
  3. Required for viral life cycle
  4. Not available in the host

Examples:
Have integrase —> attach viral genome to host genome

RNA dependent RNA polymerase —> make new RNA

RNA dependent DNA polymerase —> ( reverse transcriptase ) —> form DNA from RNA

21
Q

Why viruses cannot reproduce themselves without

assistance?

A
  1. Lack machinery for energy harvesting, protein
    synthesis, etc.
  2. Must “borrow” this machinery from host cells

—> Obligate intracellular parasites” —> cannot survive on their own

22
Q

What does viral reproduction require?

A
  1. Infection of the host cell
  2. Genetic material introduced into the host cell
  3. Host cell:
    A. Reprogrammed
    B. Produce many copies of the infecting virus
23
Q

How does the viruse replicate ( steps )

A
  1. Attachment (Adsorption)
  2. Entry (Penetration)
  3. Replication —> divides inside
  4. Assembly & Maturation
  5. Release —> cell burst and virus relaxed
24
Q

How does step 1 ( attachment / adsorption ) and step 2 happen ?

A

ATTACHMENT OR ADSORPTION

Spikes attach to specific receptors on the host cell surface
—>diff viruses req diff receptors
—> so cant infect all types of cells
—> some liver cells and some neurons bcz diff types of cells possess diff receptors

ENTRY OR PENETRATION —> viral genetic material enters the cell

  1. VIRION affixed to plasma mem ( mem fusion )
  2. Nucleocapsid released to the cytoplasm
  3. If there is envelope remain attached to the membrane
25
Q

Lytic vs lyso genie

A

Lytic life cycle
DNA —> mRNA —> protein —> lysis

Lysogenic
Injected DNA inserted into host chromosome —> provirus or prophage —> most virus genes not expressed —> phases are not produced —> prophage replicates with host

26
Q

How to determine the no of infectious particles in a viral suspension ?

A
  1. Bring a layer of susceptible host cells growing on the surface of the plate
  2. Add dilute susp of virus
  3. Cover with agar
  4. Incubate
  5. Each plaque ( clear part ) represents cell lysis
27
Q

What are the disease mechanism of viruses ?

A

A. By damaging or killing cells —> CYTOPATHIC

B. Inducing immunopathology

C. By transforming cells —> CANCER

28
Q

Give examples on damaging or killing the cells

A
  1. Poliomyelitis —> polio virus —> cytolytic virus that destroys motor neurons in the spinal cord and causes paralysis
  2. Immunodeficiency —> HIV —> kills CD4+ T cells
29
Q

Examples of immunopathology

A

The patient’s T cells attack and destroy virus-infected cells —> Inflammation and cell death

  1. Jaundice in people with hepatitis virus bcz Of bilirubin bcz it kills the liver cells and they are not able to remove the bilirubin so it leaks to the blood
  2. With some non-cytopathic virus infections, such as HCV and HBV, destruction of infected cells by CD8+ T cells is the main cause of damage to the liver —> ex : jaundice
  3. In response to virus infected cells, CD4+ T cells release proinflammatory cytokines leading to to tissue damage.
  4. Most often, the CD4 + T cell subsets involved are T helper 1 (TH1) cells, but TH17 cells may contribute to inflammatory responses during HIV, HCV and influenza virus infections.
30
Q

Examples of viruses transforming cells —> cancer

A

When a virus infects a cell, it expresses proteins that cause the cell to proliferate and/or block apoptosis.

Cancer is multi-factorial: Oncogenic or tumor viruses are very common, only a small % ( 15% ) of people infected actually get cancer.

31
Q

What are the cancers viruses are involved in?

A
  1. Cancer of the cervix: human papilloma virus (HPV)
  2. Cancer of the liver: hepatitis B or C virus (HBV or HCV)
  3. Certain leukaemias (human T-cell leukaemia virus type 1, HTLV-1) & lymphomas (Epstein-Barr virus, EBV),
  4. Kaposi’s sarcoma (human herpesvirus 8, HHV8)

Pathophysiology (6 decks)

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