Large and Complex for a Virus

Herpesviridae

3/22/13

Large and complex for a virus

DS DNA-largest genomes

Enveloped (glycoproteins)and capsid-requires direct transfer

Tegumentary proteins-head start on replication

Reproduction-

Tegumentary proteins involved in DNA binding

Immediate early proteins are Transcriptional in nature

Host proteins also involved

Late genes are capsid

Concatamerization via rolling circle (eventually) and single copies are cleaved during packaging

Alpha Herpes viruses

HSV 1 and 2 genome -120-180 kb

Very similar

Epidemiology-oral was almost exclusively type 1 now 90%

Genital was almost exclusively 2, now 90%

Pathology-

Infects epithelium and causes lesions

Result of cell lysis (halts macromolecule production) and also immunopathology

Latency in trigeminal nerve ganglia

Transmission-casual contact during activation

Cross transmission (see above)

Treatment-acyclavir and derivatives are most common

VZV-varicella-zoster virus (HHV3)

Smallest genome 120-130 kb

Chickenpox-shingles

Pathology-

Infects respiratory epithelium

Migrates to reticuloendothelium

10-14 days viremia-spreads to skin

Can remain latent in cranial nerve

Shingles-reactivation later in life

Stress or Immunocompromised

Painful-cannot cause shingles in others

May cause chickenpox

May result in Post-herpetic neuralgia

Sharp pain at site of rash that persists after rash is gone

May last months or years

May also develop allodynia-sensitivity to “background” sensation

Beta herpesviridae

Cytomegalovirus (HHV5)

Largest genome-235kb

Very frequent 50% in adults

Problem in immunocompromised and in utero if active infection

Latency in leukocytes and kidney cells

Replicates in epithelium and fibroblasts

-common in ductal cells-tear ducts, mammary ducts etc

Roseoloviruses (HHV6, HHV7)

Cause roleola in children

Mild exanthem (complications in immunocompromised)

Sometimes called “sixth disease”

Gamma herpesviridae genomes 170 kb

Epstein-Barr (HHV4)-mononucleosis

Transmitted by saliva

Infect oropharynx

Migrate to B-cells in lymphatic tissue

Immortalize B cells

Leads to activation and proliferation of T cells

Diagnosis of mono

Without T cell response B cell proliferation -B cell lymphoma

Early symptoms are similar to strept throat-pharyngitis, fever, malaise etc.

HHV 8

Causes Kaposi's sarcoma-purple skin lesions

Also causes B-cell lymphoma in AIDS patients

Similar to EBV but not entirely understood

Difficult to culture and perform in vitro infections