A retrovirus that causes leukemia in humans may be slipping into blood supplies undetected, claim researchers in tomorrow's issue of the Proceedings of the National Academy of Sciences. But other investigators familiar with the work counter that there's no cause for alarm.
Each pint of donated blood in the United States is checked for many viruses, including hepatitis, HIV, and human T cell lymphotropic virus type 1 (HTLV-1), which can lead to leukemia. But Dorothea Zucker-Franklin of New York University and colleagues say they have found evidence that fragments of the virus escape detection by current tests. The researchers checked blood samples from 81 former intravenous drug users. By using the polymerase chain reaction (PCR), the researchers found that 48% carried a gene from HTLV-1, but only 22% of these had the antibodies to HTLV-1 that are routinely used to screen for the virus. "I'm very concerned about it," says Zucker-Franklin, a hematologist. "I do not believe we should transfuse people with cells that have those [viral] sequences."
Although Zucker-Franklin says she has no evidence that anyone has become infected with the HTLV-1 gene, called tax, following a transfusion, she adds that confidentiality concerns have prevented her from studying people who have received tax-contaminated blood. And while there is also no evidence that anyone who harbors tax has suffered any illness from it, she notes that the gene is particularly worrisome because--at least in test tube studies--it can turn cells cancerous.
"It's a major contribution if it's true," says Institute of Human Virology head Robert Gallo, whose lab first isolated HTLV-1. Specifically, he says, it could lead researchers to probe cancerous cells for single genes such as tax. Because viruses in the same family share genes, says Gallo, the work also raises the possibility that there is yet another virus in the two-member HTLV family.
But other experts have their doubts. "I'm not convinced there's a significant prevalence of tax" in people who don't have HTLV-1 antibodies, says retrovirologist Michael Busch of the University of California, San Francisco, and that city's Irwin Memorial Blood Centers. Busch says his lab collaborated with Zucker-Franklin on an analysis of tax in HTLV-1-positive and -negative blood samples. "The results were inconsistent," he says. And in large studies with blood donors, his team has not found pieces of viruses that would evade antibody-based tests. "HTLV is the last thing I'd be concerned about," he says.