Mesothelioma and Simian Virus 40

The relationship between mesothelioma and Simian Virus 40 has long been contested. Some evidence shows that a Simian Virus 40 infection causes mesothelioma, while other evidence rejects this claim.

More research is needed to come to a final consensus regarding the relationship between mesothelioma and Simian Virus 40. 

What Is Simian Virus 40? 

Simian Virus 40 was discovered in rhesus monkey kidney cells in 1960. At the time, polio vaccines were made from these cells and given to the public for mass immunization.

It is estimated that 10 to 30 million people in the US were exposed to Simian Virus 40 between 1955 and 1963 due to the polio immunization program. 

This exposure was so serious that most researchers predict that 80% to 90% of US children were exposed to potentially contaminated polio vaccination during those years. 

In 1961, reports found that Simian Virus 40 caused tumors in hamsters. These findings forced the US government to screen polio vaccines that were not free of the virus. Still, any vaccines made before this regulation were not withdrawn from the program. This allowed children to potentially be exposed to the virus until 1963. 

Evidence for a Causal Relationship 

As we already mentioned, the first evidence that Simian Virus 40 could lead to cancer was found in the early 1960s. In 1994, a new discovery was made that mesothelioma includes Simian Virus 40-like DNA sequences. Since then, researchers have continued to look at the relationship between the virus and pleural mesothelioma. 

In some animal testing, all animals injected with the virus into their pleura developed mesothelioma in under a year. Another study found that 60% of US mesothelioma cases contained Simian Virus 40. Yet another study differs in finding that 80% of the cases contained said virus.

More so, some studies find mesothelial cells to be susceptible to Simian Virus 40. This finding suggests that asbestos and the virus in question act as co-carcinogens. To date, the virus has been found in more than 40 different laboratories, some of which claiming to have found the virus in mesothelioma tumors.  

Conflicting Evidence 

Confusingly, there is equal amount of evidence opposing the claim that there is a causal relationship between mesothelioma and Simian Virus 40. Most notably, there is no increase of cancer between children vaccinated before 1963 and those vaccinated after. 

Another study found that exposure to Simian Virus 40 is not enough to cause cancer in humans. Instead, it may contribute to the cancer’s development so long as the person has other carcinogen exposure, such as asbestos. 

Studies by the National Cancer Institute have even shown a lack of evidence supporting the causal relationship between cancer and Simian Virus 40. 

What Does this Mean? 

These conflicting results show that more research must be done to determine the relationship between mesothelioma and Simian Virus 40. Today, there is just as much evidence to support its causal relationship as there is to refute it. Future investigation hopes to come to a final conclusion regarding their relationship.