Herpesviruses Flashcards Preview

Micro/Immuno Part 2 > Herpesviruses > Flashcards

Flashcards in Herpesviruses Deck (28):
1

more than an STD

-variety of human infections
-chicken pox
-mono
-birth defects
-cancer
-8 different species
-most people infected with over 3
-infection is lifelong

2

Herpesvirus life cycle

-HVs are highly restricted to humans (not HSV)
-each HV prefers a different cell type
-DNA genome enters nucleus for mRNA transcription
-viral gene expression occurs in immediate early, early, and late phases
-genome replication by viral DNA pol
-egress by exocytosis-through nuclear pore and again through ER

3

phases of gene expression

-immediate early-proteins to help with more transcription
-early-proteins to help with replication
-late-structural proteins for virion assembly

4

herpesvirus latency

-definition of HV latency-the genome is present in a cell but infectious virions are absent
-establish latency in a variety of cell types before symptoms or virus replication are apparent
-the genomes are maintained for the life of the infected person
-major barrier to vaccines

-HSV1 in neuron
-HCMV in HSCs
-EBV in B cell

5

flow chart of virus

-exposure and transmission can cause primary infection and then latency which can eventually lead to reactivation and recurrent disease
-primary infection in children and recurrence in adults can lead to primary infection of new person
-virus is shed through latency periods-can also infect a new person

6

HSV1 primary disease

-spread by close contact with active lesions or asymptomatic shedding
-gingivostomatitis usually occurs in childhood
-lesions on mouth, face, nose, eyes
-usually above waist, can be genital
-latency established in neurons

7

HSV1 recurrent disease

-tingling and itching (prodrome) may precede outbreak
-lesions on lips or inside mouth
-other sites are eyes, genitals, fingers
-triggers are fever, sunlight, hormones, stress, physical trauma, etc
-lesions are contagious

8

HSV in brain

-HSV1 (2) primary infections often cause meningitis
-stiff neck and headache
-recurrent HSV infections occasionally cause encephalitis by going back into brain
-fever and neuro symptoms
-HSV targets temporal lobe

9

HSV 2 primary disease

-spread by close contact between mucous membranes (genital and/or oral)
-acquired in adulthood
-symptoms-many lesions, pain, itching, fever, malaise, headache
-usually but not always below the waist
-latency established in neurons
-double infections with 1 and 2 are common

10

HSV2 recurrent disaese

-prodrome-itching, tingling at lesion site the day before outbreak
-vesicular lesions appear on labia, penis, anus, mouth, eyes, etc
-lesions are contagious
-shedding and transmission can occur without symptoms
-frequency of recurrences is highly individual, ranges from never to monthly

11

HSV diagnosis and treatment

-serology or PCR to distinguish between 1 and 2
-antiviral therapy can shorten infections and reduce transmission
-antiviral prophylaxis is advised for people with frequent outbreaks
-acyclovir is parent drug-zovirax
-valtrex-valaciclovir
-penciclovir-famvir

12

HSV prevention

-safe sex
-avoid contact with cold sores-don't kiss a baby when you have an outbreak!
-chemoprophylaxis-valtrex and famvir approved for daily use to prevent outbreaks
-no vaccines- trials failed

13

VZV diseases

varicella-chicken pox is primary infection
-zoster-shingles is recurrence

14

primary VZV-varicella

-aerosol transmission-highly contagious
-latency in dorsal root ganglia neuron
-latency established before rash appears
-distinctive rash-dew drops on rose petals
-few to hundreds on face and trunck
-complications-hepatitis, encephalitis, pneumonitis, bacterial infection of lesions (MRSA, strep)

15

VZV recurrence

-herpes zoster-shingles
-more common in elderly and immunocompromised
-prodrome-burning, itching, tingling
-outbreak occurs along a single dermatome
-lesions are extremely painful and itchy
-lesions are contagious and spread varicella to children
-complications-bells palsy, postherpetic neuralgia, retinitis

16

HZO

-herpes zoster ophthalmicus
-approx 30% of zoster outbreaks affect the face
-all tissues of the eye can be infected and damaged
-zoster in the eye can destroy the retina and rapidly lead to blindness
-long lasting pain is common

17

VZV diagnosis and treatment

-diagnosis-clinical signs, PCR, antigen, serology
-treatment-not required for uncomplicated VZV
-zoster treatment only effective during first 3 days of outbreak
-antiviral drugs-acyclovir and derivatives are marginally effected
-foscarnet is second line therapy

18

VZV vaccine

-live attenuated virus
-varivax to prevent varicella, ages 1-50-80-90% effective after 2 doses
-zostavax to prevent zoster-ages >50. 50% effective for zoster, 90% effective for post herpetic neuralgia

19

EBV disease

-transmission by saliva
-EBV infects oral epithelial cells and B cells in tonsils-latency in B cells
-EBV infects >90% of people by adulthood
-childhood infections are often asymptomatic
-older teens often have mono
-170,000 cases of infectious mononucleosis per year, 15% hospitalized

20

EBV recurrences

-EBV is latent in a small fraction of B cells
-immune surveillance suppresses EBV in healthy people
-recurrences linked to immunosuppression
-malignancies
-hodgkin, AIDS non hodgkin, post transplant lymphoproliferative disease, burkitt, nasopharyngeal lymphoma
-oral hairy leukoplakia

21

EBV diagnosis and treatment

-mono-clinical signs, serology for heterophile antibodies, blood smear for elevated WBCs and atypical lymphocytes
-malignancies-treat symptoms, alleviate immunosuppression, oncotherapy
-no antivirals or prevention

22

cytomegalovirus

-affects everything
-primary usually asymptomatic-50-95% ppl infected by adulthood
-syndrome like mono-fever, lassitude, diffuse lymphadenopathy-no sore throat

23

congenital CMV

-risk high when pregnant woman has primary infections
-hearing loss
-death
-2% of pregnant women seroconvert to CMV+
-~10,000 cases of symptomatic congenital CMV disease each year

24

CMV and immunosuppresion

-AIDS patients prior to anti-retroviral therapy-CMV retinitis, gastroenteritis, pneumonitis, encephalitis, etc. caused tremendous morbidity and mortality

-transplant recipients-recipient and donor routinely tested for CMV
-CMV disease frequent cause of transplant failure and death
-pre-emptive screening and prophylactic antiviral therapy standard of care

25

CMV diagnosis and treatment

-serology, culture, PCR
-antiviral drugs-ganciclovir, foscarnet, cidofovir
-no prevention
-live attenuated virus was ineffective
-vaccine is highest priority in institute of medicine

26

Roseola infantum=exanthem subitum

-HHV6b and HHV7 infect CD4 cells, site of latency
-transmitted in saliva
-3 day illness of high fever, followed by faint rash on the trunk
-peak incidence at 7-13 months
-occurs throughout the year

27

roseola diagnosis and treatment

-clinical manifestations
-rule out drug allergy
-no treatment-supportive care for fever-avoid antibiotics
-no prevention-normal hygiene

28

final thoughts

-infections are nearly universal, inevitable, and last a lifetime
-most people live happily with their viruses
-asymptomatic shedding is the norm, not the exception
-antiviral therapy is helpful but not a cure all
-immunosuppression is a risk for all HVs to reactivate or cause malignancy
-all fields encounter