Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbiology > patterns of viral infection > Flashcards

patterns of viral infection Flashcards

1
Q

Iatrogenic

A

Illness caused by medical procedures e.g. infected needles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is tropism?

A

the preference of viruses to infect certain tissues but not others

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is tropism based on?

A
  • accessibility: to reach tissue
  • permissivity: ability to use host cell to replicate
  • susceptibility: receptor interactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Example of tropism - HIV

A

some people have a mutation in CCR5 so they are resistant to HIV. Tropism switch can occur during replication so they can bind to different receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the virus disease depend on?

A

Balance between virulence and host response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are examples of viruses whose tropisms are determined by receptors?

A

measles and HIV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How can viruses enter the body?

A
  1. Through the epithelial layers; respiratory tract, GI tract, genital tract
  2. Directly into the blood through a bite or needle
  3. Through the skin, often following abrasion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the steps for viral dissemination from the site of entry?

A
  1. Local Infection
  2. Primary Viraemia
  3. Amplification
  4. Secondary Viraemia
  5. Target Organ
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does viraemia mean?

A

viruses in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the routes of viral transmission?

A
  • respiratory e.g. influenza
  • faecal-oral e.g. adenovirus
  • contact e.g. rhinovirus
  • zoonoses e.g. rabies
  • blood e.g. HIV
  • sexual e.g. HIV
  • Maternal to neonatal e.g. rubella
  • germ line e.g. HIV
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is germline transmission?

A

The viral genome is integrated into the host DNA and transmitted via gametes to offspring.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What may dissemination depend on?

A

The polarization of the epithelial cell- some bud on the apical side, some on the basal side of the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can viruses cause rashes?

A
  • If you have a systemic infection - blood can enter the skin and cause a rash
  • Can happen when virus leaves the blood and enters the skin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Varicella - entry, infection, when do symptoms appear and incubation period?

A
  1. Virus enters the body through the respiratory route
  2. VZV can infect many cell types including peripheral blood mononuclear cells (PMBCs) and skin cells
  3. From the skin site it can infect sensory neurones where it remains latent
  4. Virus can be reactivated when cellular immunity is impaired causing a painful rash at nerve endings - SHINGLES
    • You only get symptoms after secondary viraemia
    • Incubation Period: 14 days
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the patterns of viral infection?

A
  • Acute - followed by viral clearance
  • Persistent - latent, slow, transforming
  • Long incubations
  • Oncogenesis - affect the way our cells control themselves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Give examples of acute infection followed by clearance/death

A

Acute infection and clearance
• Colds and influenza

Acute infection and death
• Smallpox and Dengue

17
Q

Acute infection with accidental pathogenesis

A

• Polio - infects motor neurones and can cause paralysis
• Rubella - has strong tropism for dividing neuronal tissue
Leads to classic triad:
o Deafness
o Eye abnormalities (cataracts)
o Congenital heart disease

18
Q

Persistent Viral Infections

A

• Chronic - low level replication in tissues which regenerate
(E.g. papillomaviruses in warts)
• Latent - viral genomes are maintained but no virus is seen until episodes of reactivation at times at which you are immunocompromised.
(E.g. herpes viruses)

19
Q

Strategies of Viral Persistence

A
  • Evading immune surveillance: MHC Downregulation
  • CTL escape by mutation
  • Infecting tissues with reduced immune surveillance e.g. CNS
20
Q

Latency - example herpes simple virus

A

•Neurones don’t divide and they live till you die
• So if then nerve gets infected it may contain lots of copies of viral genome and every now and then it will get reactivated
e.g. herpes simplex virus
• The virus first enters through the skin
• It gets into the nerve and sits there in a latent state
• When you get reactivation of the virus, it begins to make new copies of itself and travels back to the end of the nerve and replicates through the skin (forming a cold sore)

21
Q

Oncogenesis

A
  • May encode an oncogene
  • By making the host cell into a cancer cell, the virus can replicate more and keep moving onto new cells.

EXAMPLES:

  • Papilloviruses encode inhibitors of tumour suppressor p53, E6 and E7 genes - forces cells into S phase
  • HTLV-1 causes adult leukaemia
  • Hep B/C cause hepatocellular carcinoma
22
Q

HBV and HCV

A
  • HBV is a hepadnavirus (has a DNA genome) but it uses reverse transcriptase during a stage in its life cycle
  • Transmitted through blood and semen
  • There is a vaccine
  • HCV is a blood borne virus
  • 4% of people with HCV will go on to get hepatocellular carcinoma
23
Q

EBV

A
  • 95% of us are infected with Epstein-Barr Virus
  • Some people infected with EBV will go on to develop cancer:
    Burkitt’s Lymphoma
    Hodgkin’s Lymphoma
    Nasopharyngeal Carcinoma
24
Q

What does the outcome of infection depend on?

A
  • Viral sequence
  • Virus load
  • Host immune response/status
  • Host co-morbidity
  • Co-infections
  • Other medications
  • Host genetics
  • Host age/gender
25
Q

Give examples of predisposing co-morbidities and conditions for viral infection

A
  • Asthmatics and respiratory viruses
  • Obesity
  • Immunosuppression
  • Immunodeficiency
  • Elderly
  • Diabetes Mellitus
  • Pregnancy
26
Q

What is the significance of viral load?

A
  • The first child in a family to contract chicken pox often has a milder illness
  • This may be because the second child is in closer contact to an infected individual and hence gets infected by a higher dose
27
Q

What is the significance of co infections, give example?

A
  • HHV8 causes Kaposi Sarcoma in HIV infected individuals
  • Hepatitis Delta Virus (a small defective RNA virus) only infects people with HBV infection - it causes severe liver disease with rapid progression to cirrhosis and hepatic decompensation
28
Q

Viral sequence

A
  • Two strains of polio virus may vary in virulence
  • One mutations may turn it into a live attenuated virus
  • Another mutation may make it invade the motor neurone and cause paralysis
29
Q

Influenza and its tropism

A
  • Influenza is enveloped in haemagglutinin (HA)
  • HA helps influenza latch onto the surface of cells
  • It does this by HA binding sialic acid
  • Sialic acid is everywhere so in theory influenza can enter any cell of your body
  • Influenza only tends to affect the respiratory route
  • Once bound onto sialic acid, it enters the cell via the endosome
  • Low endosomal pH allows a massive conformational change - this is essential for the virus to fuse with the endosome membrane and uncoat
  • Fusion with the membrane and uncoating can only happen if the protein of the virus has been snipped in two at a particular point
  • This requirement of cutting the protein into two pieces is what determines the tropism of the virus
  • It is only in the fluid that lines our lungs that the right proteases are present.
30
Q

How can influenza tropism be extended?

A
  • Some chicken viruses have mutated the region where the protease cleaves
  • This allows it to be cleaved by different proteases found in other areas of the body
  • Infected chickens can allow virus replication in every organ of the body
31
Q

What is influenza tropism determined by?

A

Influenza tropism is determined by availability of host proteases not receptors

32
Q

Measles virus - receptor use, tropism and transmission

A

• Has H receptor (hemagglutinin) which binds to:
SLAM (CD155) - when entering for the first time
Nectin 4 - to leave the host

• Viruses replicate in airway epithelial cells and burst out into the airspace to spread via the respiratory route

Microbiology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions