INTRODUCTION





All is Fair in Love and Warts

He proclaimed she had given him warts
Of the most ignominious sorts
Said that her papilloma
Had entered his soma
And the issue was clearer than quartz

She denies having given him warts
Says that "His allegation distorts.
It's incredibly plain
That they differ by strain
As shown in my doctor's reports."


And despite his assertion of torts
On the issue of giving him warts,
She was quickly acquitted
Of having transmitted
(And upheld in the lowest of courts).


Robert D. Siegel
November 16, 1993



The Papovaviridae family is comprised of two genera: papillomaviruses and polyomaviruses. The family name is derived from the names of three prototypical members: rabbit papilloma virus, mouse polyoma virus, and simian virus 40 (SV40), originally called vacuolating virus. The family has several general features in common:

Genome:

It consists of single molecules of supercoiled, circular (covalently closed), double-stranded DNA that are replicated in the nucleus and bound to histones H2a, H2b, H3, and H4. Genome lengths vary slightly by genus; polyoma viruses are 5 kilobases, while papilloma viruses are 8 kilobases. The virions are spherical in shape and have non-enveloped, icosahedral capsids with a triangulation number, T=7. The genome does not encode a viral polymerase; instead, it uses the host's polymerase during replication. The virally encoded T antigen acts to direct the host DNA polymerase to the viral genome. Interestingly, while the reading frames of papillomaviruses are encoded on a single strand of DNA, for polyomaviruses both DNA strands encode functional proteins. (see Replication).

Other facts:

  • Most of the species have a narrow host range.
  • Replication and assembly occur in the nucleus.
  • Virions are released via cell destruction.
  • Some infections are characterized by oncogenesis or host cell transformation.
  • Transmission usually occurs through direct contact, including sexual contact.
  • The family is resistant to inactivation by heat or formalin.
  • The viruses encode 5-7 structural proteins and 3 capsid proteins (VP1-3).

    Representative Papovaviruses:

    Genus Papillomavirus:
  • Human papillomaviruses (HPV 1-62)
  • Shope papilloma virus of rabbits
    Genus Polyomavirus
  • Polyoma virus of mice
  • Simian virus 40 (SV40)
  • JC and BK viruses

    These two genera differ in several aspects:
    1) capsid size (Polyoma = 40 nm, Papilloma = 55 nm)
    2) length of genome (Polyoma = 5 kb, Papilloma = 8 kb)
    3) genomic organization
    4) clinical features

    Significant Diseases


  • Warts (papilloma), including condyloma acuminata (genital warts)
  • Progressive Multifocal Leukoencephalopathy (PML)
  • Cervical carcinoma (HPV 16, 18, 31, 33)
  • Squamous cell carcinoma
  • Epidermodysplasia verruciformis

    Researchers:


  • Richard Edwin Shope -discovery of a virally transmitted cancer of mammals, 1933.
  • William Fliers (and coworkers) -DNA sequencing of SV40, the first eukaryotic entity, 1977.
  • Paul Berg (Stanford Medical School Professor) -development of SV40 as a eukaryotic cloning vector; Nobel Prize, 1980.