MICROBIOLOGY

• JC virus (JCV) is a DNA polyomavirus discovered in 1971, isolated from patient John Cunningham.
  • Other polyoma viruses:
    • JCV is genetically closely related to BK and SV40 viruses.
    • Other members of the human polyoma virus group include:
      
      • Trichodysplasia spinulosa virus: associated with skin disease
      • Merkel cell polyoma virus: associated with a rare form of skin cancer called Merkle cell cancer
      • KI, WU, MW, human polyoma 6, 7, and 9 viruses: Found in human specimen, but no clear disease associations
  • Oncogenic potential:
    • Member of this DNA tumor virus family are well-known to cause tumors in rodents; however, except for Merkle cell cancer, oncologic potential in humans less certain.
    • Some studies have linked virus to human colorectal cancer, but this concept remains controversial.
  • Structure and composition: All polyoma viruses (including JCV) are non-enveloped and contain double-stranded DNA
  • JCV and tissues:
    • Tissue specificity: kidney epithelial cells, tonsillar stromal cells, bone marrow-derived cell lineages, oligodendrocytes, and astrocytes
    • JCV in Kidney and bone marrow derived cell: Low level viral persistence (latency)
    • JCV in the CNS: rapid viral replication in oligodendrocytes with resultant demyelinating disease
    • Uncertain if reactivation or new infection of cells. Controversy exists regarding pathogenesis of viral latency, source of latent virus and reactivation in PML.