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Repro Micro > HSV 1 and 2 > Flashcards

HSV 1 and 2 Flashcards

1
Q

Describe the structure of the herpesvirus family.

A

Large, ds-DNA viruses with icosahedral capsids that are surrounded by lipid envelopes

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2
Q

Why is the complexity of herpesviruses also their downfall?

A

Several effective anti-herpetic drugs have been developed because of all of the targets unique to the virus (limiting toxicity to humans too)

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3
Q

What is hallmark to herpesviruses?

A

They can establish latent infections in which the genome, but not progeny, is maintained in a quiescent state for the remainder of the hosts’s life; Patients infected are subject to recurrent infections when the latent virus reactivates

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4
Q

What happens once HSV attaches?

A

HSV directly fuses with the plasma membrane in a pH-independent manner and the released nucleocapsid migrates to the cells nucleus and releases the genome

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5
Q

What does initial transcription/translation of HSV (“immediate early” expression) produce?

A

Proteins that act as transcriptional regulators that modify host RNA polymerase so that it preferentially transcribes viral genes over host genes = production of early proteins

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6
Q

What is the role of the early proteins of HSV?

A

They replicate the virus genome to produce progeny genomes

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7
Q

What are the prominent members of the early protein class of HSV?

A

A thymidine kinase and components of a virally-encoded DNA polymerase

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8
Q

Why is the thymidine kinase of HSV important clinically?

A

It is required to phosphorylate (and activate) acyclovir and derivatives (DOCs for most HSV infections). Next, mutations are a problem because their spontaneous occurrence renders HSV resistant to ACV (problem in AIDS patients)

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9
Q

Once progeny genomes are synthesized for HSV, what happens?

A

The late proteins are produced

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10
Q

What late proteins are encoded in HSV?

A

Capsomeres, envelope glycoproteins, and other structural proteins

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11
Q

Where does virus assembly of HSV occur?

A

In the nucleus and the virus buds from the plasma membrane during release

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12
Q

Because the same viral glycoproteins responsible for the initial fusion are also present in the plasma membrane of infected cells late in infection, what does that mean?

A

That infected cells may fuse with adjacent, uninfected cells which can lead to the format of syncitia: giant cells with more than one nucleus = HSV spread without release of virus progeny

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13
Q

Virus assembly in the nucleus and syncitium formation are the basis of what test for HSV?

A

Tzanck smear, in which smears of cells taken from ulcers are viewed, if Tzanck shows multinucleated giant cells with nuclear inclusion bodies the infection is caused by HSV

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14
Q

After the primary infection of HSV in epidermal cells happens, what happens?

A

HSV establishes latency in peripheral sensory neurons

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15
Q

Where is the genome of HSV maintained?

A

Extrachromosomally

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16
Q

What is the only HSV gene expressed during latency? What does it produce?

A

LAT, whose product is an RNA species that silences a subset of cellular genes to prevent apoptosis of the infected neuron

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17
Q

What does LAT only being expressed mean?

A

No virus particles are produced, but a decline in cell-mediated immunity allows the virus to reactivate

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18
Q

What does reactivation of HSV lead to?

A

Recurrent infection in epithelial cells innervated by the latently-infected neurons (reactivation can kill the neuron = numbness)

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19
Q

What diseases does HSV 1 cause?

A

Herpes labialis (fever blister), Keratitis, Encephalitis

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20
Q

What diseases does HSV 2 cause?

A

Cervicitis, Vulvular vesicles, Penile Vesicles, Meningitis

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21
Q

Are most HSV infections self limiting?

A

Yes

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22
Q

HSV 1 and 2 can cause what kinds of infections?

A

Skin, ocular, and urogenital (HSV 1 is not only above the belt, and HSV2 is not only below the belt)

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23
Q

What is disseminated dz a problem in in regards to HSV?

A

Immunocompromised patients; neonates especially at risk, and infections can be fatal or severe

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24
Q

What are the symptoms of HSV?

A

Most asymptomatic, but when symptomatic multiple blisters form on the infected skin about two weeks following infections; blisters will rupture and produce severely painful open vesicles that can take 2 weeks to heal during a primary infection

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25
Q

When do recurrent HSV infections happen?

A

During lapses in immunity; resulting cold sore or genital lesion are limited in size and duration due to presence of neutralizing antibody

26
Q

What are the symptoms of the oral infections caused by HSV 1 and 2?

A

Primary: gingivostomatitis, vescicles on lips, tongue, and facial skin around mouth
Recurrent: classical fever blisters
Primary and recurrent: low grade fever/headache

27
Q

What are the primary symptoms of genital infections caused by HSV 1 and 2?

A

In males: vesicles anywhere on penis

In females: vesicles can be external or internal and can be difficult to detect even when present

28
Q

What are the recurrent symptoms of genital infections caused by HSV 1 and 2? (This question is more asking how do you tell the difference between the two?)

A

Difficult to distinguish primary from secondary genital infections w/o knowing hx; generally fewer and heal quicker; HSV 2 genital infections recur more frequently than HSV 1

29
Q

Can virus shedding occur without a recurrent genital lesion?

A

Yes

30
Q

What are the symptoms of both recurrent and primary genital infections?

A

FLS’s in addition to itching or burning skin in infected areas; muscle aches of the legs and buttocks (prodrome)

31
Q

What are the symptoms of ocular HSV infections?

A

Primary: Blepharitis and conjunctivitis seen in children
Recurrent: Keratitis can result in significant corneal scarring

32
Q

What are the symptoms of Encephalitis due to HSV?

A

It is the result of recurrent HSV 1 in adults but primary HSV 2 in neonates; presents as headache and fever –> confusion and seizures in adults; reactivation from trigeminal which then involves temporal lobes (70% mortality if untreated and 20-25 if treated early)

33
Q

What are the symptoms of meningitis due to HSV?

A

Occurs in 10% of primary HSV2; headache, stiff neck, vomiting (1 week resolution)

34
Q

What are the symptoms of neonatal HSV infections?

A

Usually the 1st - 2nd week postpartum, some are limited to skin, eyes, and mouth (they have the outcome, zoster like rash); others involve the CNS and are disseminated, 3/4 die or have significant sequelae

35
Q

How are HSV 1 and 2 transmitted?

A

Sexually; HSV2 is the more frequent genital infection

36
Q

What is the “above/below” the belt a reflection of?

A

The preferred tropism and the route of transmission of each organism

37
Q

How is Oral herpes transmitted to children?

A

Often from their parents; estimated 60% of US adults have HSV 1

38
Q

When are most HSV 2 infections dx’ed?

A

Between 20-29; 10% in males, 20% in females and 10% in young adults

39
Q

Is Herpes encephalitis rare?

A

Yes, 3/100000 adults; NOT more common in immunocompromised hosts; recurrence due to HSV 1
In neonate form it is from primary HSV 2 and about 25/100000 births

40
Q

How many neonatal infections of HSV are transplacental, with the rest occurring at time of birth?

A

5%

41
Q

If the mother current has a primary HSV infection what is the risk of transmission to the child? recurrent?

A

30%; 2-3% (maternal ab’s protective)

42
Q

What should be done if the mother has lesions at time of deliver?

A

C-section

43
Q

What is the diagnosis of genital herpes done by?

A

Culturing virus from lesions (3-10 days depending on the cytopathic effect)
Fluorescent antibody screening of virus grown in cell culture
PCR screening from vesicle swabs
Serology; can distinguish HSV 1 vs 2 but only indicates past infection
Tzanck smear

44
Q

What is the dx of herpes meningitis done by?

A

Mainly aimed at ruling out bacterial source; CSF is cultured to look for CPE to indicate viral origin = self limiting

45
Q

What is the dx of herpes encephalitis done by?

A

Cultures of CSF rarely positive here, serology also too late here, normal EEG rules OUT herpes encephalitis
Confirmation achieved by PCR of genome fragments from CSF then used in a southern blot (result in 24 hrs)

46
Q

What is dx of neonatal herpes done by?

A

Dx as for other disease, in addition check liver enzymes for disseminated disease evidence

47
Q

What is the DOC of herpes treatment?

A

ACV

48
Q

What are ACV drugs?

A

Deoxyguanosine analogs that prevent viral genome replication by inhibiting the viral DNA polymerase

49
Q

Are ACV drugs prodrugs?

A

Yes, they require three phosphate groups to become activated

50
Q

What adds the phosphate groups to ACV?

A

First by a viral kinase (HSV thymidine kinase), then 2 by cellular kinases

51
Q

Will cellular kinases add the first phosphate?

A

No, so ACV is never made into active form in a non-infected cell

52
Q

What is significant about mutations in thymidine kinase?

A

Render ACV inactive; problem in AIDS patients

53
Q

What are the ADEs of ACV tx?

A

Nausea, skin rash, diarrhea, renal failure, seizures, disorientation (last 3 in high dose therapy)

54
Q

What are Vidarabine and Trifluoride

A

DNA analogs that inhibit viral DNA polymerase

55
Q

What is foscarnet?

A

Pryophosphate analog that blocks the pyrophosphate-exchange site preferential on the viral DNA polymerase (blocks viral DNA replication)

56
Q

Does Foscarnet require phosphorylation?

A

No, so it is not affected by thymidine kinase mutations and is a backup to ACV if it fails

57
Q

What is Docosanol?

A

An OTC med for cold sores, can lessen the extent

58
Q

What does Docosonol do?

A

Modifies host cell membrane so that the virus envelope cannot fuse with the plasma membrane

59
Q

What is the specific Tx for genital herpes?

A

Low dose ACV from first sign of outbreak until completed, A single day, high dose of Famciclovir is FDA-approved if taken w/in first 6 hrs of sx
Daily suppressive therapy of low dose ACV reduces freq + length of virus shedding/spread (expectant mothers)
Educate to recognize symptoms to reduce spread

60
Q

What is the specific Tx for herpes encephalitis?

A

IV, High dose ACV for 10 days - 3 weeks at first sign of illness

61
Q

What is the specific Tx for neonatal/congenital herpes?

A

IV, high dose ACV for 14 days in skin, eye, mouth infections and for 21 days in CNS infections

62
Q

Is there an HSV vaccine?

A

No

Repro Micro (6 decks)

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