Simian virus 40
Simian Virus 40 (SV40) is a polyomavirus belonging to the Papovaviridae family, primarily found in various species of monkeys, particularly macaques. Initially discovered in 1960, SV40 was identified in rhesus macaque kidney cells that were used in the production of the original Salk and Sabin polio vaccines. There is ongoing investigation into how humans may have been exposed to SV40, with speculation suggesting that millions of Americans were potentially exposed between 1955 and 1963 during mass vaccinations. The virus has been linked to several types of cancers, including mesothelioma, osteosarcoma, and non-Hodgkin lymphoma, though definitive causal relationships remain unclear.
The mechanisms by which SV40 may contribute to cancer involve the inactivation of critical tumor suppressor proteins. While earlier studies did not show heightened cancer risks among those exposed to SV40, more recent research is revealing potential associations. Notably, polymerase chain reaction (PCR) testing has detected SV40 in a notable percentage of malignant tumors, prompting further examination of the virus's role in oncogenesis. Despite these findings, challenges such as lab contamination and the need for standardized testing methods persist in clarifying SV40's impact on human health. The exploration of SV40's implications continues to be a prominent area of scientific research.
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Subject Terms
Simian virus 40
ALSO KNOWN AS: Simian vacuolating virus 40, SV40
RELATED CANCERS: mesothelioma, osteosarcoma, choroid plexus tumors, ependymomas, non-Hodgkin lymphoma
DEFINITION: Simian virus 40 is a polyomavirus of the family Papovaviridae and is found in several species of monkeys.
Exposure routes: The actual route of exposure of simian virus 40 in humans is under investigation. There is speculation that millions of Americans were exposed to the virus between 1955 and 1963 during the mass immunizations with the original Salk (injectable) and Sabin (oral) polio vaccines. However, some people too young to have received the original polio vaccines have tested positive for exposure to the virus. Therefore, other routes of exposure, such as person to person, may be possible.
Where found: As a latent infection in several species of macaque monkeys; also in biomedical research labs to transform human cells or be inoculated into laboratory animals for oncology studies
At risk: People who were vaccinated with the Sabin and Salk polio vaccines between 1955 and 1963; about one hundred army camp men who were inoculated with adenovirus vaccines contaminated with simian virus 40 in the 1950s and 1960s; lab researchers working with the virus
ETIOLOGY AND SYMPTOMS OF ASSOCIATED CANCERS: Carcinogenesis may be induced by the inactivation of cellular tumor-suppressor proteins (TP53 and RB1).
History: The virus was discovered in 1960 in the rhesus macaque kidney cells used to amplify the poliovirus for the original Salk and Sabin polio vaccines. In 1961, after learning that inoculated simian virus 40 caused cancer in laboratory animals, the US federal government required that new stocks of polio vaccine be free of the virus. Since then, the Salk and Sabin vaccine stocks have been produced using human or African green monkey cell lines extensively screened for viral contaminants.
Evidence has slowly emerged to show some connection between Simian virus 40 and cancer. The National Cancer Institute previously reported that a half-century of epidemiological studies in the United States and Europe did not appear to show increased cancer risk in people who may have been exposed to simian virus 40. However, as the twenty-first century progressed, studies began to show links between the virus and cancer. In animal testing, the virus was shown to cause brain and bone cancer, as well as malignant mesothelioma and lymphomas. An analysis of over 1,500 cancer patients also showed a significant association between the virus and these diseases in humans as well. Polymerase chain reaction (PCR) testing has revealed traces of simian virus 40 in many malignant mesothelioma tumors and (in one study) 42 percent of non-Hodgkin lymphomas, among others. However, association does not mean causation, and PCR testing techniques for simian virus 40 have not been standardized. Lab contamination could also be a problem. The linkage between simian virus 40 exposure and cancer in humans is still being actively investigated.
Bibliography
Durie, Brian G. M. Patient Handbook: Multiple Myeloma, Cancer of the Bone Marrow. N. Hollywood: Intl. Myeloma Foundation, 2012–2013.
Qi, Fang, et al. "Simian Virus 40 Transformation, Malignant Mesothelioma and Brain Tumors." Expert Review of Respiratory Medicine, vol. 5, no. 5, 2011, p. 683, doi.org/10.1586/ers.11.51. Accessed 16 June 2024.
Vilchez, Regis A., and Janet S. Butel. "Emergent Human Pathogen Simian Virus 40 and Its Role in Cancer." Clinical Microbiology Reviews, vol. 17, no. 3, 2004, pp. 495-508, doi.org/10.1128/CMR.17.3.495-508.2004. Accessed 16 June 2024.
“Viruses that Can Lead to Cancer.” American Cancer Society, www.cancer.org/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/viruses.html. Accessed 16 June 2024.