SV40
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| Simian virus 40
Template:Taxobox begin placement virus Template:Taxobox group i entry | |
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| Family: | Polyomaviridae |
| Genus: | Polyomavirus |
| Species: | Simian virus 40 |
|} SV40 is an abbreviation for Simian vacuolating virus 40 or Simian virus 40, a polyomavirus that is found in both monkeys and humans. Like other polyomaviruses, SV40 is a DNA virus that has the potential to cause tumors, but most often persists as a latent infection.
The virus was first identified in 1959 in cultures of rhesus monkey kidney cells that were being used to produce polio vaccine. It was named for the effect it produced on infected green monkey cells, which developed an unusual number of vacuoles. The virus is dormant and shows no visible effects in Rhesus monkeys. The virus has been found in many macaque populations in the wild, where it rarely causes disease. However, in monkeys that are immunodeficient—due to, for example, infection with Simian immunodeficiency virus—SV40 acts much like the human JC and BK polyomaviruses, producing kidney disease and sometimes a demyelinating disease similar to PML. In other species, particularly hamsters, SV40 causes a variety of tumors, generally sarcomas.
The molecular mechanisms by which the virus reproduces and alters cell function were previously unknown, and research into SV40 vastly increased biologists' understanding of gene expression and the regulation of cell growth.
SV40 has not been proven to cause disease in humans, but several studies have suggested a link to cancer based on the presence of relatively large amounts of what may be SV40 DNA fragments in some tumor tissues, particularly mesotheliomas and non-Hodgkin's lymphoma. There is as yet no consensus on the meaning of these findings.
Polio vaccine contamination
There is strong suspicion that polio vaccines produced between 1955 and 1962 were contaminated with SV40, because the kidney cells the vaccine virus was grown in came from infected monkeys. Both the Sabin vaccine (oral, live virus) and the Salk vaccine (injectable, killed virus) were affected; the technique used to inactivate the polio virus in the Salk vaccine, by means of formaldehyde, did not reliably kill SV40.
It was difficult to detect small quantities of virus until the advent of PCR testing; since then, stored samples of vaccine made after 1962 have tested negative for SV40, but no samples prior to 1962 could be found. Thus, although over 10 million people received the potentially contaminated batches of vaccine, there is no way to know whether they were exposed to the virus, and if so, whether it was in a quantity and by a route that would cause infection. It is also unknown how widespread the virus was among humans before the 1950s, though one study found that 12% of a sample of German medical students in 1952 had SV40 antibodies. It is not known whether the virus can be transmitted between humans.
An analysis presented at the Vaccine Cell Substrate Conference in 2004 [1] (http://www.newscientist.com/news/news.jsp?id=ns99996116) suggested that vaccines used in the former Soviet bloc countries, China, Japan, and Africa, could have been contaminated up to 1980, meaning that hundreds of millions more could have been exposed to the virus.
External links
- CDC fact sheet on SV40 and vaccine concerns (http://www.cdc.gov/nip/vacsafe/concerns/cancer/default.htm)
- Transcript of 1997 NIH conference on SV40 in humans: part 1 (http://www.fda.gov/cber/minutes/sv40012797-1.htm), part 2 (http://www.fda.gov/cber/minutes/sv40012797-2.htm), part 3 (http://www.fda.gov/cber/minutes/sv40012897.htm)pl:SV40