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Microbiology > 4- Viral pathogens: classification, biology, diseases - II > Flashcards

4- Viral pathogens: classification, biology, diseases - II Flashcards

1
Q

How is the viral load determined?

A

➝ RT-PCR

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2
Q

What leads to AIDS?

A

➝ inexorable depletion of CD4 cells

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3
Q

What has HIV been adapted to do?

A

➝ give a very long period of infection

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4
Q

What is the viral load set point?

A

minimum number of HIV particles you can have without the immune system detecting it but the virus still replicating

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5
Q

How do HIV+ people die?

A

➝opportunistic infections

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6
Q

What must viruses do to survive?

A

➝ evade immune responses

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7
Q

How do viruses avoid being killed by immune cells?

A

➝ they replicate inside the immune cells whose function is to recognise and kill infected cells

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8
Q

What is the advantage for a virus to replicate inside immune cells?

A

➝ hides virus from immune cells

➝ inhibits immune cell function

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9
Q

What does inhibition of immune cell function allow?

A

➝ allows other pathogens to replicate in the virus infected hosts
➝ so disease occurs

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10
Q

What are permissive T cells?

A

➝ have CD4 on cell surface

➝T cells in which the virus can replicate

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11
Q

What % of T cells are permissive and non-permissive?

A

➝ 95% non-permissive

➝ 5% permissive

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12
Q

Describe what happens when HIV enters a non-permissive CD4 cell?

A

➝ the virus enters but doesn’t replicate
➝ accumulation of incomplete reverse transcripts
➝ detection by IFI16 DNA sensor
➝ IFI16 activates the innate antiviral and inflammatory responses
➝ IFI16 inflammasome assembly
➝ Inflammasome response which activates caspase-1 and pyroptosis occurs
➝ cell death and excretion of all the inflammatory factors
➝ this warns other cells that there is some type of infection

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13
Q

What happens in a permissive CD4 T-cell?

A 
➝ the virus enters the cell and replicates
➝ processive reverse transcription
➝ Evading host detection
➝ double stranded DNA
➝ infection of CD4 T cell
➝ Activates caspase-2 
➝apoptosis occurs
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14
Q

What three viral proteins are involved in evading the immune response to virus replication?

A

➝ VPR
➝ VIF
➝ NEF

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15
Q

In permissive cells what is activated when there is foreign DNA in the cell?

A

➝ caspase-3 is activated which is a mediator of apoptosis

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16
Q

Describe how the cycle of immune exhaustion occurs?

A

1) HIV infection
2) CD4 T cell death via pyroptosis and the release of pro-inflammatory cytokines and cellular contents occur
3) Inflammation occurs which is good for the virus because it brings more healthy CD4 cells that allows the virus to infect new cells- recruitment of health CD4T cells
4) the inflammatory state hyper charges the immune system so much that there is migration of the immune neutrophils and monocytes into the infected area
5) more inflammation occurs and the exhaustion of the immune system occurs- cell death and release of pro-inflammatory cytokines and cellular contents

17
Q

What are 2 viruses associated with HIV?

A

➝ Herpes simplex virus (HSV)

➝ Kaposi’s sarcoma herpesvirus (KSHV)

18
Q

What are 2 bacteria associated with HIV?

A

➝ mycobacterium tuberculosis

➝ salmonella

19
Q

What are 2 fungi associated with HIV?

A

➝ candida

➝ cryptococcus neoformans

20
Q

What are 2 parasites associated with HIV?

A

➝ cryptosporidium

➝ toxoplasma gondii

21
Q

What are the two possible routes of opportunistic infection in HIV?

A

➝ primary infection

➝ reactivation from latency

22
Q

What is a primary opportunistic infection in HIV?

A

➝ the infection is resolved by immune suppression and infection moves to the sites in the host that the immune system does not access
➝in these sites the virus resides without replication: latency

23
Q

When does reactivation from latency occur?

A

➝ upon immunodeficiency

24
Q

Describe how reactivation from latency occurs with HSV?

A

➝ HIV sufferers are exposed via the skin to HSV
➝ the virus replicates
➝ the virus gets into the infected host and moves into the nervous system
➝ there isn’t immune surveillance in the nervous system because the immune system can’t access the blood brain barrier
➝ the virus moves along the neurites into the dendrites
➝ The immune system is constantly surveilling so the immune system trying to interact with the cells is sending a constant message
➝ if the immune system is removed (HIV) the virus does not get the message so it is freed and goes back to the zone of infection
➝ the virus senses the lack of immune response

25
Q

Describe how reactivation from latency occurs with KSHV?

A

➝The virus enters and you get KS progenitor cells
➝They become de novo infections
➝De novo infection leads to latent infection of the immune cells (B cells)
➝KSHV gets into B cells and the immune system can’t see it
➝Latent infection -virus replicates at a low level
➝A cellular cue occurs - without the constant interaction between B cell and T cell the virus has no signal to reactivate
➝In a HIV sufferer there are no T cells so there is no constant signal between T and B cells which provides a reactivation signal to the virus

26
Q

Describe how KSHV can become carcinogenic?

A

➝There is infection of cells KS progenitors
➝De novo infections occur which turn into latent infections
➝There is some intra or extracellular cue which reactivates the virus
➝Such as inflammatory cytokines from pyroptosis
➝These cytokines may be the cues which reactivate the virus from latency
➝This leads to lytic or productive infections
A few of these cells become oncogenic and undergo uncontrolled replication
➝During oncogenesis there is also an inflammatory response

27
Q

What therapy stops HIV replication?

A

➝ ART (antiretroviral therapy)

28
Q

What is ganciclovir?

A

➝ Direct acting antiviral drug which prevents KSHV replication within B cells

29
Q

What are the 7 viruses that cause cancer?

A 
➝ HPV - Human papilloma viruses 
➝ EBV - Epstein-Barr virus 
➝ HBV - hepatitis B virus
➝ HCV - hepatitis C virus
➝ HHV-8 - human herpes virus 8
➝ HTLV-1 - human T lymphotropic virus-1
➝ MCV - Merkel cell polyoma virus
30
Q

What type of a virus is HPV and what cancer does it cause?

A

➝ papilloma virus
➝ circular dsDNA
➝ skin cancer

31
Q

What type of a virus is EBV and what cancer does it cause?

A

➝ Herpes virus
➝ linear dsDNA
➝ lymphoma

32
Q

What type of a virus is Hepatitis B virus and what cancer does it cause?

A

➝ Hepadnavirus
➝ circular dsDNA
➝ carcinoma

33
Q

What type of a virus is Hepatitis C virus and what cancer does it cause?

A

➝ Flavivirus
➝ ssRNA
➝ carcinoma

34
Q

What type of a virus is HHV-8 and what cancer does it cause?

A

➝ Herpes virus
➝ linear dsDNA
➝ lymphoma

35
Q

What type of a virus is HTLV-1 and what cancer does it cause?

A

➝ retrovirus
➝ RNA-DNA
➝ leukemia/lymphoma

36
Q

What type of a virus is MCV and what cancer does it cause?

A

➝ Polyomavirus
➝ dsDNA
➝ carcinoma

Microbiology (11 decks)

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