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2. Foundations of Medicine PoD > Intro to Viruses > Flashcards

Intro to Viruses Flashcards

1
Q

What is a virus

A

Non-cellular, genetic element that cannot replicate independently of a living (host) cell

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2
Q

Virology

A

the study of viruses

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3
Q

What is a virion

A

extracellular form of a virus:
* exists outside host and facilitates transmission from one host cell to another
* contains nucleic acid genome surrounded by a protein coat and, in some cases, other layers of material

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4
Q

What can viruses only do wigh regards to replication

A

Only replicate inside host cells: obligate intracellular pathogens

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5
Q

Structure of virus cells

3

A
  • icosahedral: 20 faces, each an equilateral triangle
  • helical: protein binds around DNA/RNA in a helical fashion
  • complex: neither icosahedral or helical
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6
Q

tissue tropism

A

Most viruses have a specific host range and only infect specific host cell types

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7
Q

what can virus families be classified according to

A
  • Virion shape / symmetry
  • Presence / absence of envelope
  • Genome structure
  • Mode of replication
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8
Q

Name some structures of a viron

A

lipid envelope, protein capsid, virion associated polymerase, nucleic acid (DNA or RNA), spike projections

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9
Q

Give steps of viral infection/replication

Not sure if need to know?

A
  1. Attachment
  2. Uncoating
  3. Replication of genomic nucleic acid
  4. mRNA sythnthesis, protein synthesis, genomic and nucleic acid synthesis
  5. Viron assembly
  6. Insertion of virus proteins into membrane
  7. Budding and release
  8. Maturation
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10
Q

capsid

A

protein coating, virion wraps virus in capsid for transmission. The capsid is the infective form. You can also sometimes get a lipid coating derived from the host cell

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11
Q

examples of viruses transmitted by blood-borne route

A

HIV, Hepatitis B, Hepatitis C

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12
Q

examples of viruses transmitted by sexual route

A

HIV, Hepatitis B

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13
Q

examples of viruses transmitted by vertical route (parents to offspring)

A

HIV, Hepatitis B

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14
Q

examples of viruses transmitted by faecal-oral route

A

Hepatitis A, Hepatitis E, Polio

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15
Q

examples of viruses transmitted by droplet route

A

Influenza, RSV

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16
Q

examples of viruses transmitted by airborne route

A

Measles, Chickenpox

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17
Q

examples of viruses transmitted by close contact route

A

Herpes Simplex, CMV, EBV

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18
Q

examples of viruses transmitted by vector borne route

A

Dengue, Yellow Fever, Chikungunya

19
Q

examples of viruses transmitted by zoonotic route

A

Rabies, MERS, Ebola

20
Q

Host range

A
  • Some viruses may only infect humans, e.g. smallpox, measles
  • Some may also infect other animals / birds:
  • Transmission of a novel virus to humans
  • Coinfection of human and animal or bird strains in one organism may lead to recombination and generation of a new strain
21
Q

examples of respiratory syndromes

A

Influenza, Measles, Chickenpox

22
Q

examples of neurological syndromes

A

Enteroviruses, Polio, Rabies, HSV, VZV

23
Q

examples of gastroenteritis syndromes

A

Norovirus, Rotavirus, Adenovirus

24
Q

examples of hepatitis syndromes

A

Hepatitis ABCDE, CMV, EBV, Yellow Fever

25
Q

examples of skin infections

A

HSV, Enteroviruses

26
Q

examples of eye infections

A

HSV, VZV, Adenovirus

27
Q

examples of congenital abnormalities syndromes

A

CMV, Rubella, VZV, Parvovirus

28
Q

examples of arthralgia syndromes

A

Dengue, Chikungunya, Rubella, Parvovirus

29
Q

examples of lymphadenopathy syndromes

A

HIV, CMV, EBV

30
Q

consequences of viral infection

with examples

A
  • Clearance of virus (with no, short or long term immunity)- measles (long term immunity)
  • Chronic infection- HIV, hepatitis B, hepatitis C
  • Latent infection: Herpes Virus
  • Transformation (long term infection with altered cellular gene expression)- Epstein-Barr Virus, Human Papillomavirus
31
Q

Explain viral latency

A
  • Following primary infection, some viruses lie dormant in the cell
  • The full viral genome is retained in the host cell, but its expression is restricted, such that few viral antigen and no viral particles are produced
  • Reactivation of viral replication can occur
  • Reactivations may or may not cause apparent disease
  • Reactivation more likely to occur and more severe in immunocompromised
32
Q

Examples of viral latancy

A
  • Herpes simplex virus
  • Varicella zoster virus
33
Q

What can viral infections lead to

A

cancer

34
Q

What is the mechanism of viral infection causing cancer

A
  • modulation of cell cycle control (driving cell proliferation)
  • modulation of apoptosis (prevention of programmed cell death)
  • reactive oxygen species mediated damage (some persistent viral infections can cause persistent inflammatory processes which lead to cancer via reactive oxygen species)
35
Q

Methods to detect viruses

A
  • Whole organism
  • Part of organism - e.g. antigen, nucleic acid
  • Immune respone of host to pathogen - e.g. antibodies
36
Q

Detection method - whole organism

A
  • Microscopy - not suitbale for diagnosis as not specific (can’t identify virus type)
  • Culture: unifected vs infected cells
37
Q

Detection method - part of organism

A
  • Antigen detection
  • DNA/RNA detection, extraction of genetic material from sample, amplification of region of target organism genome (if organism present in sample) - PCR
38
Q

Detection Methods: immune response

A
  • similar methods as those used for antigen detection
  • may be used to determine acute (IgM)/ recent infection, prior infection / response to vaccination - IgG
39
Q

What is antiviral therapy

A
  • All antiviral agents are virustatic, none are virucidal
  • As viruses utilise host cell enzymes in order to replicate, there are limited viral proteins that are potential targets for antiviral drugs
  • Toxicity to the host cell is not uncommon: side effects
  • Only used in a minority of viral infections
40
Q

In what situations may antivirals be used

A
  • Prophylaxis (to prevent infection)
  • Pre-emptive therapy (when evidence of infection/replication detected, but before symptoms are apparent)
  • Overt disease
  • Suppressive therapy (to keep viral replication below the rate that causes tissue damage in an asymptomatic infected patient)
41
Q

What are some ways we can prevent viral infection

A
  • Immunisation (vaccination(slow)/passive immunisation with immunoglobulin (quick))
  • {rophylactic treatment post exposure
  • Infection prevention and control measures (isolate symptomatic pationt, PPE, safe use and disposal of sharps)
  • Blood/tissue/organ screening
  • Antenatal screening
42
Q

What properties can viruses have which may lead to their irradication

A
  • No anima resivour or ability to amplify in environment
  • Clearly identifiable
  • No chronic carrier state
  • Efficient and practical intervention (e.g. vaccination)
  • Political/social support
43
Q

give examples of eradicated viruses

3

A
  • Smallpox
  • Measles
  • Polio

2. Foundations of Medicine PoD (28 decks)

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