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PoD > Viruses > Flashcards

Viruses Flashcards

1
Q

Virus, size and 3 structures

A
  • Small 20-400nm
  • Non-cellular
  • Icosahedral (20 faces)
  • Helical: protein binds around DNA/RNA in a helical fashion
  • Complex: neither icosahedral or helical
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2
Q

Define obligate intracellular pathogens

A
  • Need a host to survive
  • Can only replicate inside host cell
  • Need a specific host range and only infect host cell types
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3
Q

Taxonomy of viruses

A

Order
Family
Genus
Species

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4
Q

Classification of virus families

A

Virion shape/symmetry
Presence/absence of envelope
Genome Structure
Mode of replication

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5
Q

Blood-borne viruses

A

HIV
Hep B
Hep C

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6
Q

Sexually transmitted virsuses

A

HIV
Hep B
Hep C increasingly

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7
Q

Vertically transmitted viruses

A

HIV

Hep B

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8
Q

Faecal-oral route viruses

A

Hep A
Hep E
Polio

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9
Q

Droplet viruses example and definition

A
  • Large particles and fall within a short distance of a person
  • Influenza, Respirtory Syncytial Virus
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10
Q

Airborne example and definition

A
  • Aerosolised, can travel much further in the environmment
  • Measles
  • Chickenpox
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11
Q

Close contact transmitted viruses

A

Herpes simplex
CMV (Cytomegalovirus)
EBV - Glandular fever

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12
Q

Vector-borne viruses

A

Dengue
Yellow fever
Chikungunya

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13
Q

Zoonotic viruses

A

Rabies
MERS
Ebola

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14
Q

Host range

A

Some viruses may only infect humans e.g. smallpox, measles
Some may also infect other animals which can result in transmission of a novel virus to humans or coninfection where human and animal strains may recombine to generate a new strain

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15
Q

Consequences of viral infections

A
  • Clearance (with no, short or long term immunity)
  • Chronic infection
  • Latent infection
  • Transformation (long term infection with altered cellular gene expression)
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16
Q

Latent infection life cycle

A
  • How you get cold sores or shingles
  • Virus lies dormant after 1ary infection
  • Full viral genome is retained in the host cell but it’s expression is restricted, a few viral antigens and no viral particles are produced
  • Reactivation of viral replication can occur
  • More likely to occur and more severe in immunocompromised
17
Q

Viruses and cancer, mechanisms

A
  • Viruses can lead to cancer but often need another event to also occur
    Mechanisms:
  • Modulation of cell cycle control, drives cell proliferation
  • Modulation of apoptosis, prevention of programmed cell death
  • Reactive oxygen species mediated damage, some viral infections cause inflammatory processes which lead to cancer via reactive oxygen species
18
Q

Viruses and cancer examples

A

EBV - Glandular fever:
Burkitt’s lymphoma, Hodgkin’s lymphoma, nasopharyngeal carcinoma
Human herpes virus: Kaposi’s sarcoma, primary effusion lymphoma
Human T-cell Lymphotropic virus: Adult T-cell leukaemia/lymphoma
Human Papillomavirus: cervical, anus, oropharyngeal cancers
Hepatitis B and C: hepatocellular carcinoma

19
Q

Principles of viral culture

A

You can either detect the whole organism or part of the organism

20
Q

Whole organism detection method

A
  • Electron microscopy, see the shape and match it
  • Culture
    but neither are really done anymore
21
Q

Part of organism detection method

A
  • Antigen detection: you have a specimen coated in antibodies and you look for a reaction with fluoresence
  • DNA/RNA detection
  • Extraction of genetic material from sample
  • Amplification of region of target organism genome: PCR, look for amplification curve that matches the virus
  • Immune response to pathogen: look for a sign that they’ve been exposed, opposite of antibody test. Can determine acute/recent infection or prior infection/response to vaccination
22
Q

Antiviral therapy

A
  • All antiviral agents are virustatic
  • 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 an uncommon side effect
  • Only used in the minority of viral infections as there aren’t many available
23
Q

When you might use an antiviral

A
  • Prophylaxis (preventing infection)
  • Pre-emptive therapy, if there’s evidence of infection, replication but no apparent symptoms. Especially in HIV
  • Overt disease
  • Suppressive therapy, keep viral replication rate low to prevent tissue damage
24
Q

Prevention of viral infection

A
  • Immunisation: vaccination, passive immunisation with immunoglobulin
  • Prophylactic treatment post exposure
  • Infection prevention and control measures. Isolate symptomatic patients, PPE, safe use and disposal of sharps
  • Blood/tissue/organ screening
  • Antenatal screening
25
Q

What do you need to eradicate a virus?

A
  • No animal reservoir or ability to amplify in the environment
  • Clearly identifiable, with accurate diagnostic tool
  • No chronic carrier state
  • Efficient and practical intervention e.g. vaccination
  • Political and social support

PoD (33 decks)

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