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Tracking The World's Oldest Human Retrovirus

August 22, 2002

Heather Heilman
Phone: 865-5714

Ever heard of the human T-lymphotropic virus, or HTLV? If you haven't, you're not alone. HTLV, the oldest human retrovirus, is relatively rare and produces no symptoms in the majority of cases. But it's spread the same way as HIV, and therein lies the problem.

In some places--New Orleans is one of them--a significant number of HIV patients are also infected with HTLV. The two viruses actually infect the same cells within the body, but not much is known about how they affect each other. But Mark Beilke is working on that. Beilke, an associate professor of medicine who specializes in infectious diseases, recently received a five-year National Institutes of Health grant for a unique study of the long-term effects of co-infection with HIV and HTLV.

Almost 10 percent of the patients at New Orleans' HIV Outpatient Clinic also are infected with HTLV. That rate is high for the United States, where co-infection is most prevalent among those who acquired the viruses through intravenous drug use. But in places where HTLV is more common, such as areas of South America and the Caribbean, the rate of co-infection may be as high as 20 percent.

"HTLV is a much older, much more genetically conserved retro-virus than HIV," Beilke said. "It's very well adapted to its host, which is why many people are asymptomatic carriers. It's probably infected indigenous populations for thousands of years."

There are two strains of HTLV. HTLV-1 can cause leukemia or lymphoma in from 1 to 2 percent of those infected. HTLV-2, which is spreading in near-epidemic proportions among intravenous drug users, can also cause tropical spastic paraparesis, a disease with symptoms similar to those of multiple sclerosis, as well as leukemia and neurological complications. Symptoms typically emerge years or even decades after infection.

"We don't know what's going to happen to people who are infected with both viruses," Beilke said. "We don't know if the drug cocktails we use to treat HIV will also treat HTLV. We don't know how the viruses affect each other, but we think that HIV accelerates the ability of HTLV to induce some fairly unusual clinical occurrences."

He began pilot studies with the clinic population in 1993, and has noticed a high incidence of lymphoma among those who are co-infected. They also seem to have a higher-than-expected rate of neurological complications. The current study will show whether those observations can be substantiated over time.

Beilke hopes to enroll between 200 and 250 co-infected patients. Beilke has enlisted nurse Jane Walls to help with the study.

"Jane has been a godsend to me because of her extensive nursing experience with substance-abusing populations," Beilke said. "Educating the patients is going to take a little work." HTLV is not well understood even in the medical community. "HTLV is a very misunderstood virus, and it's not one that we can treat," Beilke said. "I want to have more answers so we can help patients."

A virologist, however, needs patience. While the current grant will allow Beilke to follow his subjects for five years, it will likely take longer than that for all the effects of co-infection to become apparent.

Heather Heilman may be reached at hheilma@tulane.edu.

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