In the last half century, there has been an enormous increase in the incidence of lymphomas and mesotheliomas. A link between SV40 and mesothelioma was established when the tumors were found to develop in hamsters injected intrapleurally, intracardially, and intra-peritoneally with simian virus 40 (SV40). In addition, through polymerase chain reaction (PCR) analysis, RNA in situ hybridization, Western blotting, and immunohisto-chemistry, the majority of human mesotheliomas were found to contain and express SV40. canadian health&care mall
Aside from mesothelioma, SV40 has been found to cause specific tumor types, mainly lymphomas, and also osteosarcomas, ependymomas, and choroid plexus tumors when injected into hamsters. Weanling hamsters injected IV with the virus were found to develop lymphomas, lymphocytic leukemias, and osteosarcomas at sites distant from the point of injection. In addition, intracardiac injection of wild-type SV40 caused lymphomas and osteosarcomas in 33% and 10% of hamsters, respectively (the remaining 60% developed mesothelioma). Of interest, the deletion of the SV40 small t antigen, which removes the ability of SV40 to inhibit the activity of cellular PP2A, leads to a mutated SV40 (SV40 small t mutant), which caused lymphomas in 100% of the injected hamsters. Similarly to mesothelioma, several studies demonstrated that human ependymomas, choroid plexus tumors, and osteosarcomas contain and express the SV40 genome. The prevalence of SV40 in human lymphomas, however, has not been thoroughly investigated.
In immunodeficient rhesus monkeys, the natural host of the virus, SV40 infection results in a variety of diseases, including encephalomyelitis, pneumonia, and astrocyto-mas. In a recent study of rhesus monkeys, simian immunodeficiency virus-positive primates were found to exhibit SV40-induced lesions and SV40 sequences in their kidneys and brains, while lesions associated with SV40 or the presence of SV40 sequences were not found in simian immunodeficiency virus-negative monkeys. These data suggested that immunosuppressed individuals might also be at higher risk for SV40 infection.