Daring Experiment Points Way for Vaccine to Treat HIV

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Feb. 2, 2000 (San Francisco) -- Four patients whovolunteered to stop taking HIV drugs after receiving an experimental AIDSvaccine are giving researchers a peek into the future of AIDS therapy.According to a report at an HIV conference here, two of the patients mayhave significantly altered the course of their HIV infections.

"This provides us with hope for the eventualuse of therapeutic vaccination," says Xia Jin, MD, PhD, of New York'sAaron Diamond AIDS Research Center (ADARC). A therapeutic vaccine is onethat will stop the disease once a person has been infected. He warned,however, that the study findings are verypreliminary. "We are not trying to draw sweeping conclusions,"he says. "The [sample] size is small."

The four patients received highly active antiretroviraltherapy (HAART) very soon -- an average of 60 days -- after firstbecoming infected with HIV. These days, HAART is considered thestandard therapy for those with HIV. The four patients' viruslevels remained undetectable in their blood for an average oftwo-and-one-half years, at which time they received the experimentalHIV vaccine. One week after their fourth and final vaccination-- the series took 180 days to complete -- the subjects volunteeredto stop taking their anti-HIV drugs.

Two of the subjects saw the amount of virus in theblood increase 13 and 23 days after stopping medication -- a ratenearly identical to that seen in non-vaccinated peoplewho stop taking HAART. But the other two patients had a much slowerrate of increase, with the virus in their blood becoming detectableat 85 and 68 days after stopping HAART, a phenomenon called delayedrebound.

Jin tells WebMD that those with delayed rebound haveyet to have the virus increase back to the levels they had beforetreatment. The two patients who responded to the vaccination thusfar have a viral load (a measurement of virus in the blood) 100times lower than before beginning HAART.

Twelve patients are enrolled in the study, Jin says,and six already have completed vaccination. It is up to them,of course, to decide whether to stop taking their anti-HIV medications.

"We have to be careful drawing conclusions,"David Ho, MD, and director of ADARC, tells WebMD. "This isearly data. ... Other vaccine strategies are going to be testedin this context."

Gary Nabel, MD, PhD, the newly named head of thenew vaccine center at the NIH, tells WebMD that the study mayhelp answer important questions about how HIV affects the immunesystem and if a vaccine will ever work to prevent or slow thedisease.

The vaccine is now in early clinical trials to seeif it will also prevent HIV before infection takes place.

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