University of Texas Southwestern researchers have established a link between human non-Hodgkin's lymphomas and a monkey virus carried by some people.

The study was published in the March 2002 edition of the British medical journal The Lancet. Researchers examined nearly 400 tumors and

control tissues and found the viral footprint for simian virus 40 (SV40) in the tumors of 43 percent of patients with non-Hodgkin lymphoma. The virus, predominantly of the B-cell type, was present in 9 percent of Hodgkin's lymphoma cases, a significantly lower rate. The percentage of SV40-positive findings among healthy subjects and patients with other types of adult and pediatric cancers, other than bone tumors, was zero to 6 percent.

Approximately 287,000 new non-Hodgkin's lymphoma cases are diagnosed worldwide every year.

SV40 was first transmitted to humans between 1955 and 1963 in contaminated batches of polio vaccine. As many as 30 million people may have been vaccinated with the tainted serum. Persons born after 1963 also have been found to carry the virus, but scientists are uncertain how the virus was transmitted to them. Estimates for the number of carriers range between 2 percent and 13 percent of the population, although large population-based studies are needed.

Dr. Adi Gazdar, professor in the Hamon Center for Therapeutic Oncology Research and the Department of Pathology and principal investigator on the study, said the findings fully confirm earlier research on hamsters that associated SV40 with brain and bone tumors, mesotheliomas (tumors in the lining of the lungs and other organs) and B-cell lymphomas. SV40 had been associated in humans with brain and bone cancer and mesothelioma, but the human lymphoma connection is new. The rates of virus detection in HIV-positive and HIV-negative subjects with lymphoma were similar, a fact that came as a surprise to the researchers.

Dr. John Minna, director of the Hamon Center for Therapeutic Oncology Research, said that it is known that SV40 activates a protein that interacts with and deactivates the proteins that control the normal cellular life cycle, creating immortal malignant cells.