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Virology > DNA Viruses > Flashcards

DNA Viruses Flashcards

1
Q

Describe the structure of Papillomaviruses

A

-Small circular dsDNA virus, icosahedral and naked
-*It does NOT contain a viral DNA polymerase; it needs to enter the cell cycle to replicate

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2
Q

T/F: A large number of papillomavirus serotypes exist

A

True!

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3
Q

List the two main types of HPV

A

Mucosal
Cutaneous

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4
Q

What type of infection is HPV?

A

-Localized, only on the skin or mucosal surface

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5
Q

Does HPV have a viremic stage?

A

No

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6
Q

What does Cutaneous HPV form?

A

Benign warts on the skin that can persist and spread

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7
Q

What is the treatment for the warts formed by Cutaneous HPV?

A

-Removing the wart with chemicals or ‘burning’ them off the skin
-Tx usually needs to be done more than once
-Most warts will be cleared without tx

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8
Q

Can Cutaneous warts spreads?

A

Can occasionally spread to the oral or genital mucosa through autoinoculation

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9
Q

Mucosal HPV forms ______ which are the most common sexually transmitted disease in the US

A

Anogenital warts

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10
Q

What are the most common types of Anogenital warts?

A

-6 and 11 –> are low risk and are associated with 90% of genital infections
-16 and 18 –> are high risk and are associated with 70% of anogenital cancers

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11
Q

What can HPV 6 and 11 cause?

A

Recurrent respiratory papillomatosis

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12
Q

How can children acquire oral HPV? Adults?

A

-Children can acquire oral HPV at birth from their mother
-Adults can acquire it through oral sex
-Warts appear on the larynx, necessitating surgical removal

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13
Q

What is needed in order for HPV to infect the basal cell layer?

A

A break in the skin/mucosa

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14
Q

What happens once HPV infects the basal cell layer?

A

-The basal cell will then replicate to repair the wound
-The virus will establish several copies of itself in an episomal form
-Even in apparently cleared infections, sometimes the virus will stay latent in the basal cells

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15
Q

As the HPV virus containing cell moves through the different epithelial layers, it will express ________

A

different viral proteins

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16
Q

In the upper epithelial layers, how does HPV replicate?

A

The virus will prod the terminally differentiated cell to replicate so it can makes thousands of copies or viral DNA and lots of capsid protein

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17
Q

What role does the viral E7 protein play in HPV replication?

A

Binds and inactivates the cellular Rb protein, which causes the cell to go into the cell cycle

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18
Q

How does the HPV virus get released?

A

The top layer of cells slough off, the cell breaks down, releasing the virus

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19
Q

HPV cancer is caused by dysregulation of the _______ genes of HPV by integrating the viral DNA episome into the basal cells’ cellular DNA

A

E6 and E7

-Note that genome integration is NOT a normal part of HPV’s replication. This integration of the viral episome turns off a viral protein that controls the levels of E6 and E7 in the cell, leading to high levels of E6 and E7 in the basal cells

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20
Q

In the oncogenic forms of HPV, the E7 protein will bind and degrade the _____ protein causing the cell to go into the cell cycle

A

Rb

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21
Q

In oncogenic forms of HPV, the E6 protein will cause degradation of _____, allowing the cell to continue to cycle and accumulate mutations

A

p53

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22
Q

T/F: In most cases, HPV infections spontaneously regress

A

True

-Problems occur if there is a persistent infection with a high-risk type. Over many years this may result in cancer

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23
Q

T/F: Once the immune system is activated, most people are protected from reinfection from that HPV strain

A

True

-Some people might have cross-protection between different strains. However, it is possible to be infected with more than one strain, either simultaneously or sequentially

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24
Q

What cancers is HPV known to contribute to?

A

Cervical, anal, vulvar, vaginal, penile, and oropharyngeal cancers

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25
Q

HPV 16 causes….

A

-Almost all oropharyngeal cancers caused by HPV
-Having HPV 16 is just a risk factor; many who have infections do not go on to develop cancer

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26
Q

What type of vaccine is the HPV vaccine?

A

subunit vaccine with just one of the coat proteins of HPV

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27
Q

Which HPV causes most genital warts?

A

6 and 11

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28
Q

Which HPV causes most cervical cancers?

A

16 and 18

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29
Q

Why is it recommended that boys and girls ages 9-14 get vaccinated with two doses of the vaccine?

A

This age is picked because it is best to get vaccinated before any sexual contact, and this age group seems to have the most durable response to the vaccine.

30
Q

Describe the structure of Polyomavirus

A

-Small dsDNA circular, naked virus with an icosahedral capsid
-Does NOT have a viral DNA polymerase and need the cell to divide to replicate their viral DNA

31
Q

JC only causes problems in the ______

A

Immunocompromised:
-AIDS
-Transplant recipients
-People take some immunosuppressive drugs
-Hematologic malignancies

32
Q

The JC virus is more active in who?

A

The immunosuppressed, but even then, most have no problems with the virus.

33
Q

When does the JC virus become problematic?

A

When the virus mutates and becomes neurotropic, and the person is immunosuppressed

34
Q

What does the mutant JC virus infect?

A

Infects and kills oligodendrocytes causes CNS demyelination and the condition PML (Progressive Multifocal Leukoencephalopathy)

35
Q

Who is infected with JC?

A

-A large majority of people have been infected with the JC virus by adulthood.
-Many people are latently infected and sporadically shed the virus in their urine

36
Q

What is the treatment against the JC virus?

A

-The treatment is to stop the immunosuppressive agent or start HIV therapy to make the immune system more active in fighting the infection
-Unfortunately, there can be lasting damage from the PML

37
Q

Describe the structure of Parvovirus

A

-Small ssDNA linear, naked virus with an icosahedral capsid
-It has NO DNA polymerase and cannot stimulate the cell to grow (like polyomavirus or papillomavirus).
-To replicate, the virus needs to infect actively dividing cells

38
Q

____ causes Erythema infectiosum-fifth disease, a generalized infection

A

B19

39
Q

What characterizes B19 infections?

A

The “slapped cheek rash”

40
Q

What do Parvovirus B19 symptoms start as?

A

Fever, runny nose and headache. This is when the infection spreads by respiratory secretions

41
Q

When is a person with parvovirus B19 no longer contagious?

A

A rash develops because of the immune response and the person is no longer contagious

42
Q

What is the problem with parvovirus B19?

A

The virus needs to infect actively dividing cells and preferentially infects erythroid precursor cells, killing those cells. This can cause transient anemia if infected

43
Q

For people who already have an increase in RBC turnover due to hemoglobin disorders like sickle cells or chemotherapy, B19 infection can cause ________

A

a transient aplastic crisis

-This can cause a severe drop in RBC

44
Q

What happens when infected with B19 during pregnancy?

A

-If infected during the first trimester, there’s a chance of miscarriage
-B19 infection anytime during pregnancy has a chance of causing hydrops fetalis

45
Q

Describe the structure of Poxvirus

A

complex DNA virus with an envelop and ds linear DNA

46
Q

Where do Poxviruses replicate?

A

-Solely in the cytoplasm
-The virus brings into the cell a DNA-dependent RNA polymerase so that it can make messenger RNA. This way, it doesn’t have to enter the nucleus

47
Q

What is Molluscum contagiosum? How is it spread?

A

A local skin infection and is spread by close personal contact or autoinoculation

48
Q

What are the symptoms of Molluscum contagiosum?

A

Raised lesions on the skin that appear smooth with a dimple in the middle (these lesions are secreting virus)

49
Q

What type of infection is Molluscum contagiosum?

A

Local infection of the skin (no viremic stage)

50
Q

How long does Molluscum contagiosum last?

A

Usually disappears without intervention by 2 to 12 months without scarring and affects children more than adults

51
Q

List the Orthopoxviruses

A

Variola
Cowpox
Mpox
Vaccinia

52
Q

Orthopoxviruses are similar enough that there is _________

A

cross-protection

This means that infection with one orthopox protects against infection with other orthopoxviruses

53
Q

The _____ route transmitted smallpox, but lesions were also contagious

A

respiratory

54
Q

A person with smallpox is still contagious until when?

A

All scabs fall off the body. Scabs contain infectious virus

55
Q

Smallpox is ______

A

eradicated

56
Q

______ vaccination within 3 days of exposure to smallpox can prevent or substantially lessen disease

A

Prophylactic

57
Q

If smallpox is spread from germ warfare, the CDC favors what kind of treatment?

A

Ring vaccination over mass vaccination and isolation of the infected.

58
Q

This is the virus contained in the vaccine for smallpox. It is an attenuated virus in humans.

A

Vaccinia virus

59
Q

Is the virus in the vaccine now, vaccinia virus, cowpox?

A

No

Although the vaccine started with cowpox, the virus in the vaccine now, vaccinia virus, is not cowpox.

60
Q

Are there risks with the vaccinia vaccination?

A

Yes, there are some risks

61
Q

What does the more inactivated for of the vaccine (vaccinia virus) require?

A

Two shots 4 weeks apart and is protective after the 6th week

62
Q

______ looks very much like smallpox

A

Mypox

63
Q

Where is Mpox found?

A

-Is endemic in some African countries with spodic outbreaks

64
Q

What is the animal reservoir for mpox?

A

It is unknown

-Monkeys are not the natural reservoir, but it can be found in several rodents

65
Q

What was the 2003 mpox outbreak in the US caused by?

A

Imported rodents from Africa

66
Q

What vaccine is effective at preventing mpox?

A

-Live vaccinia virus
-Non-replicating attenuated vaccina virus vaccine
-An antiviral can also be used to treat mpox

67
Q

There is currently an outbreak of mpox. How is this strain appearing to be spread?

A

-Appears to be efficiently spread through sex/close personal contact as well as respiratory and has spread to at least 104 non-endemic countries.
-It can present non-traditionally with lesions at the site of contact before systemic symptoms or without systemic symptoms

68
Q

What type of infections are smallpox and mpox?

A

Generalized infections

69
Q

_____, if given on the arm, can be a local infections

A

Vaccinia

However, vaccinia can, in some cases, become generalized; there is where the adverse effects of the vaccine are seen

70
Q

Remember, vaccinia is the name of the virus in the ________

A

smallpox/mpox vaccine

Virology (17 decks)

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