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MIC 430 > Lec 9: Herpesviruses & Other dsDNA Viruses > Flashcards

Lec 9: Herpesviruses & Other dsDNA Viruses Flashcards

1
Q

The herpesviruses derive their name from the Greek word_____, meaning to ____.

A

herpein

to creep

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2
Q

how many herpesviruses have been isolated from a range of hosts including mammals, birds, fish, reptiles, amphibians and molluscs?

A

> 100

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3
Q

of herpesviruses are human viruses?

A

8

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4
Q

most people in the world are

A

persistently infected with herpesviruses

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5
Q

8 Human Herpesviruses:

A
  1. ) Herpes simplex viruses 1 and (HSV-1 and HSV-2)
  2. ) Varicella-Zoster virus
  3. ) Epstein-Barr virus (EBV)
  4. ) Cytomegalovirus
  5. ) Herpesvirus 6A and 6B
  6. ) Herpesvirus 7
  7. ) Kaposi’s Sarcoma-associated Herpesvirus
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6
Q

Once herpesviruses have infected a host, they often remain as…
& Often…

A

…persistent infections for the lifetime of the host

…latent infections, which can be reactivated from time to time, especially if the host becomes immunocompromised

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7
Q

Both primary and reactivated herpesvirus infections can either be…
& The outcome depends on the…

A

…asymptomatic or can result in disease of varying severity

…interplay between the particular virus and its host, and especially on the immune status of the host.

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8
Q

Herpes simplex viruses 1 and 2 aka

A

(HSV-1 and HSV-2)

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9
Q

Both HSV-1 and HSV-2 infections are

A

lifelong

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10
Q

Estimated HSV-1 infection globally:

A

3.7 billion people under age 50

= (67%)

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11
Q

Estimated worldwide HSV-2 infection:

A

417 million people aged 15-49

= (11%)

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12
Q

(HSV-1 and HSV-2)

which is more prevalent?

A

HSV-1 (67%)
HSV-2 (11%)

…HSV-1 more prevalent

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13
Q

(HSV-1 and HSV-2)
initially infect…
& may enter…

A

…epithelial cells of the oral or genital mucosa, the skin or the cornea.
…neurons and may be transported to their nuclei, where they may establish latent infections.

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14
Q

2 modes of Latent infections:

A
  1. ) Virus DNA integrated into a cell chromosome. (After infection of the cell the virus genome is integrated into the genome of the host cell) (ex: retroviruses)
  2. ) Virus DNA present as multiple copies of circular molecules.
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15
Q

HSV-1 commonly infects via the…
A latent infection may be reactivated if…
Reactivation results in…

A

…lips or the nose between the ages of 6 and 18 months
…the host becomes stressed or immunosuppressed
…the production of virions, (which in about 20–40% of cases the virions are transported within the neuron to the initial site of infection, where they cause productive infection in epithelial cells, resulting in a cold sore)

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16
Q

HSV-2 usually causes…

A

genital herpes, which is a sexually transmitted disease.

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17
Q

Usually, HSV-1 infects..
& HSV-2 infects…
However, there are increasing numbers of cases where…

A

…face (lips),
…genitals
…HSV-1 infects the genitals and HSV-2 infects the face (backwards)

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18
Q

The majority of genital herpes infections (HSV-2?) produce either…

A

atypical or no symptoms.

Only a minority of cases are recognized

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19
Q 
(Varicella-zoster virus) 
Infection usually occurs in... 
and causes...
But, It may also spread to...
and causes...
A

…childhood
…varicella (chickenpox).
…nerve cells, where it may establish a latent infection
…shingles

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20
Q

(Varicella-zoster virus) dna in host =

A

Extrachromosomal circular DNA

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21
Q

(Varicella-zoster virus)
After one got chickenpox, the virus…
Shingles occurs after…

A

…remains inactive (becomes dormant) in certain nerves in the body.
…the virus is re-activated in these nerves years later.

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22
Q

(Varicella-zoster virus) aka

A

“VZV”

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23
Q

How VZV is transmitted? (2)

A
  • little is known, because the virus is difficult to culture in lab, and the lack of suitable animal model.
  • Most likely, via skin lesions and airborne.
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24
Q

what detects VZV in air surrounding patients?

A

PCR

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25
Q

The reason VZV suddenly becomes active again =

Often…

A

= not clear

…often only one attack occurs.

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26
Q

(VZV)

Shingles may develop in ___ ___ ____, but you are more likely to develop the condition if: (3)

A

any age group

  1. ) age >60
  2. ) You had chickenpox before age 1
  3. ) immune system is weakened by medications/disease
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27
Q

Epstein-Barr virus aka

28
Q

Epstein-Barr virus (EBV) is transmitted in

29
Q

Epstein-Barr virus (EBV)
whats infected first?
then…

A

epithelial cells

…then infection spreads to B cells (main host cell for EBV)

30
Q

main host cell type for EBV =

31
Q

Usually, more than __% of people become infected with ___ during the first years of life, results in…

A

90%
EBV
…few or no symptoms

32
Q

Epstein-Barr virus (EBV)

In developed countries some individuals…

A

…do not become infected until adolescence or adulthood.

33
Q

Epstein-Barr virus (EBV)

Some adults develop…

A 
infectious mononucleosis (glandular fever)
aka the "kissing disease"
34
Q

EBV is associated with

A

a number of tumors in humans

35
Q

(Cytomegalovirus)

most infections show

A

no/mild symptoms

36
Q

(Cytomegalovirus)

To a pregnant woman, the virus can infect…

A

the placenta and then the fetus, causing serious consequences.

37
Q

(Cytomegalovirus)
In the US about __% of babies are born infected with the virus
~7% of these show evidence of…
For the other individuals, damage develops…

A

1%
…virus-induced damage at birth (small brain size and liver/spleen enlargement)
…at a later stage (hearing loss and mental retardation)

38
Q

(Cytomegalovirus) transmission method =

A

sexually transmitted

39
Q

Human Herpesvirus 6A/6B aka

A

HHV-6A

HHV-6B

40
Q

Infection of a child with HHV-6B can cause

A

a fever and the sudden appearance of a rash.

41
Q

(Human herpesvirus 7)

was first isolated from

A

a culture of CD4 T cells in lab

42
Q

(Kaposi’s Aarcoma-associated Herpesvirus)

was discovered in ____ and is named after…

A

1994

…the tumor with which the virus is associated

43
Q

(Herpesvirus Virion)
are relatively…
and composed of… (3)

A

…complex

…a large number of protein species organized into 3 distinct structures: capsid, tegument, envelope

44
Q

Herpesvirus genome =

A

linear dsDNA

45
Q

Herpesvirus capsid =

A

icosahedral surrounded by tegument

46
Q

Herpesvirus tegument aka

Herpesvirus tegument =

A

“viral matrix”

= a cluster of proteins that lines the space between the envelope and nucleocapsid of all herpesviruses

47
Q

Herpesvirus envelope contains

A

a large number of spikes

48
Q

Most of viral structural proteins are commonly named

A

VP (virus protein)

49
Q

In HSV-1 the most abundant proteins in the capsid and the tegument are

A

VP5 and VP16

50
Q

In the herpesvirus envelope there are at least…

A

…12 species of glycoprotein, each of which is prefixed ‘g’

ex: gB, gC and gD

51
Q

(HSV-1 genome organization)

The genome consists of…

A

2 unique sequences each flanked by repeat sequences

52
Q

(HSV-1 replication)

Although HSV-1 infects only humans in nature, …

A

…a variety of animal species and cell cultures can be infected in the laboratory

53
Q

(HSV-1 replication)

Entry Steps: (6)

A
  1. ) HSV-1 virion binds initially to heparan sulphate, then to main receptor
  2. ) virion envelope fuses with plasma membrane. (Infection may also occur by endocytosis, followed by fusion between the virion envelope and the endosome membrane)
  3. ) nucleocapsid and tegument proteins released into cytoplasm
  4. ) nucleocapsid transported to nucleus (where virus replication takes place)
  5. ) nucleocapsid rapidly transported along microtubules to the vicinity of a nuclear pore.
  6. ) virus DNA is released into nucleus (where the linear DNA molecule is converted into a covalently closed circular/complimentrary DNA molecule “cccDNA”)
54
Q

(HSV-1 Tegument Proteins)
Are transported to…
Roles include…

A

…several sites in the cell

…a variety (down-regulation of host DNA, RNA/Protein synth)

55
Q

(HSV-1 Tegument Proteins)
One tegument protein known as…
Other tegument proteins are involved in…

A

…virion host shutoff (vhs) protein degrades cell mRNA.

…the activation of virus genes

56
Q

Herpesvirus genes are expressed in 3 phases:

A

immediate early (IE)
early (E)
late (L)

57
Q

immediate early (IE) proteins # and role:

A

5 IE proteins and all are transcription factors with roles in switching on E and L genes.

58
Q

early (E) proteins role:

A

Some of the E proteins have roles in virus DNA replication.

59
Q

late (L) proteins role:

A

Most of the L proteins are the virus structural proteins.

60
Q

Protein roles:
IE =
E =
L =

A 
IE = transcription factors / E and L gene on switch
E = virus DNA replication
L = virus structure
61
Q

(Herpesvirus assembly & exit) =

A

dsDNA is packed into procapsid in nucleus

empty shell

62
Q

(Latent herpesvirus infection)

multiple genome is switched ___ during latency, but a few regions are…

A

off

…transcribed and a few RNAs are synthesized; some viruses also synthesize a few proteins

63
Q

(Latent herpesvirus infection)

No virus proteins are required to maintain…

A

…latency in cells that do not divide, so none are produced in neurones latently infected with HSV-1

64
Q

Virus RNAs synthesized during latency are known as

A

latency associated transcripts

LATs

65
Q

LATs undergo…
and at least one of them plays a role in…
thereby ensuring…

A

…splicing
..inhibiting apoptosis
…the survival of the neuron with its latent HSV-1 infection.

66
Q

increased immunocompromised =

A

increased likelihood of reactivation

MIC 430 (22 decks)

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