Human Biology 115A
Robert Siegel, instructor
The Papovavirus Family is one of the many virus families associated with human disease. The Papovavirus is divided into two subfamilies or genera, Polyomavirus and Papillomavirus. However, the family name is more indicative of the history of the virus, than of its component subsets. Papova is derived not from the combination of the subfamilies, but from the first described viruses used to define the family:
Rabbit PApilloma virus
Mouse POlyoma virus
Simian VAcuolating virus
For centuries,it had been suspected that warts were caused by some infectious agent. The transmissibility of the condition from person to person had long been recognized. But it wasn't until 1933 that the first papillomavirus was scientifically described. The Shope papillomavirus of the rabbit soon became the first specific experimental example of viral association with warts.
In the late 1950s, a poliovirus vaccine prepared in monkey cultures was contaminated with an oncogenic polyomavirus of Asian macaques, later termed Simian Virus 40 (SV40). This vaccine was administered to millions of U.S. residents. No apparent disease was induced, but the incident unsurprisingly sparked major research on the nature and pathogenesis of polyomaviruses.
The biology of papovavirus has shown to be truly fascinating. Relatively speaking, it is a small, unenveloped virus with an icosahedral capsid and a triangulation number of 7. All papovaviruses contain double-stranded DNA and replicate in the nucleus.
Perhaps the most perplexing aspect of papova biology is its gene expression. The genomes of papovaviruses such as SV40 employ differential splicing, overlapping and nested gene organizations. And to make matters even more complex, varying reading frames are used to transcribe sets of genes and "early genes" and "late genes" which insure the initial activation of the more crucial viral processes and developments.
Of the several dozen members of the papovavirus family, only a handful are associated with human disease. These viruses are human papillomavirus (HPV), and two members of the polyoma subgroup JC virus and BK virus. In recent years, HPV, in particular, has become a major source of concern as it has been consistently linked to genital cancer. Also, HPVs recent prevalence and epidemic status poses additional questions regarding future medical implications and impact. Primarily, the concern surrounds the fact that there is a continuing prevalence among adolescents and young adults despite widespread condom use, and there is uncertainty as to the existence and magnitude of a future rise or epidemic of genital cancers.
Created: February 1, 1998
Last modified: January 20, 1999