Virus Linked to Leukemia Found to Be Prevalent

A type of virus possibly linked to leukemia and identified previously in only a handful of cases appears to be widespread among intravenous drug users in New Orleans, raising the possibility of learning more about the mysterious infective agent.

Researchers from the UCLA School of Medicine and Abbott Laboratories of North Chicago stumbled across the surprising findings while examining the effectiveness of a test for human T-cell leukemia virus type 1, known as HTLV-1.

They found that 27% of 121 drug users they tested turned out to be infected with either HTLV-1 or the lesser-known virus, HTLV-2. Of those who were infected, a surprising 91% were infected with HTLV-2.

“We did know that there were a few people with HTLV-2 around but not that it was so predominant,” said Helen Lee, a research and development scientist with Abbott and co-author of a report on the finding published today in the journal Science.

“I think that intravenous drug abuse is a bit like the bellows that stokes the slow fire of the virus,” Lee said in a telephone interview. “With this finding and identification of a cohort, we should be able to study the virus.”

Both viruses are of the same family of retroviruses as the human immunodeficiency virus, which causes AIDS. All are believed to be spread through sexual contact and intermingling of blood, and by infected mothers to their babies during delivery.

HTLV-1 is believed to cause hairy cell leukemia, perhaps decades after initial infection. It is not uncommon in regions of Japan, the Caribbean, Africa and the southeastern United States. But HTLV-2 was thought to be much rarer.

Blood Analyses

The researchers performed sophisticated analyses of the blood of 121 intravenous drug users from one narcotics treatment center in New Orleans.

Lee said little is known about the epidemiology of HTLV-2 infection and what diseases it might cause. Because of the lack of an effective screening tool, she said, only about a dozen cases had been identified and extensively studied in the past.

The screening test usually used to detect antibodies to HTLV-1 also reacts to antibodies for HTLV-2. The researchers used newly developed “gene amplification” techniques to directly detect the two types of virus and to differentiate between them.

Lee and Jerome Zack, a UCLA post-doctoral researcher and co-author, said they hoped that identifying a relatively large group of HTLV-2 infected people would help researchers better understand the health impact of such infection. “Right now, nobody knows exactly what this thing causes,” Zack said.