DNA Viruses 2

Question 0

Herpes virus lifecycle

Answer 0

Similar to adenovirus
DNA genome enters nucleus via microtubules for mRNA transcription
Viral gene expression: immediate early, early, late phases
Replication by viral polymerase and assessory factors
Egress by exocytosis but does not lyse like adenovirus
Latency: genome present in cell but no infectious virions, in variety of cell types, maintained for life, asymptomatic shedding

Question 1

Herpes viruses

Answer 1

Not only an STD, causes variety of human infections like chickenpox, mono, birth defects, cancer

Tegument proteins

Restricted to humans

Question 2

Herpes simplex type 1 and 2 (HSV)

Answer 2

Diagnosis/treatment: serology/PCR, antiviral therapy, antiviral prophylaxis, acyclovir

Prevention: safe sex, avoid contact with cold sores, chemoprophylaxis

Question 3

HSV-1

Answer 3

Primary:
Spread by close contact with active lesions or asymptomatic shedding
Gingivostomatitus (sore/swelling gums and mouth during childhood), lesions on mouth, face, nose, eyes
Latency in neurons causes meningitis

Recurrent:
Tingling/itching, lesions
Triggers are fever, sunlight, hormones, stress, physical trauma
Cause fever, neurological symptoms

Question 4

HSV-2

Answer 4

Primary:
Close contact between mucous membranes (genital)
Adulthood, latency in neurons
Lesions, pain, itching, fever, malaise, headache

Recurrent:
Lesions but shedding/transmission can occur without symptoms

Question 5

Varicella-zoster virus (VZV)

Answer 5

Diagnosis: clinical signs, PCR, antigen, serology

Treatment: antiviral drugs, acyclovir and derivatives

Vaccines: Varivax, Zostavax

Question 6

Primary VZV

Answer 6

Varicella (chickenpox)

Aerosol transmission, latency in dorsal root ganglia neurons

Rash (dewdrops on rose petals)

Complications: hepatitis, encephalitis, pneumonitis, bacterial infections

Question 7

VZV reoccurrence

Answer 7

Herpes Zoster (shingles)

More common in elderly, immunocompromised

Burning, itching, tingling, follows nerves (one side)

Herpes zoster ophthalmicus affects face and eyes

Question 8

Epstein-Barr virus disease

Answer 8

By saliva, infects oral epithelial cells and B cells in tonsils, mono

Reoccurrences: latent in small fraction of B cells, immunosuppression causes, infects more than 90% of people by adulthood but childhood infections are asymtomatic

Diagnosis/treatment: serology, blood smear, treat symptoms, alleviate immunosuppression, oncotherapy

Question 9

Cytomegalovirus (CMV)

Answer 9

Primary infection usually asymptomatic

Like mono but no sore throat

Congenital CMV: pregnant woman has primary infection

Affects AIDS patients, transplant recipients

Treatment: toxic antiviral drugs

Question 10

Roseola infantum

Answer 10

HHV6b and HHV7 infect CD4+ T cells

Saliva transmitted, three-day high fever followed by faint rash

No treatment, don’t give antibiotics