06/22/09

CANADA; UNITED STATES:  Researchers Discover New Weapon in HIV Fight

Study Shows Targeted Chemotherapy Has Potential to Kill Disease 'Forever'

A new study raises hopes that researchers may be closer to solving the mystery of why HIV persists in the body even when antiretroviral therapy (ART) is successful.

"For 15 years, we haven't had a clue," said Dr. Rafick-Pierre Sekaly, a University of Montreal professor, director of the Vaccine and Gene Therapy Institute in Port St. Lucie, Fla., and corresponding author of the new study. "But now we do. Now there's a whole new perspective on how to get rid of HIV."

Despite the advances achieved through ART since the mid-1990s, scientists know that HIV lingers in the body; it is never eliminated. "The minute the patient stops taking the therapy, the virus is reborn," said Dr. Jean-Pierre Routy, associate professor of hematology at McGill University-Montreal and a study co-author. "Then the immune system is destroyed and the patient becomes sick again." Viral reservoirs within the body act to re-infect the patient's system when ART is interrupted. Routy cited a recent US study that confirmed increasing the dosing and potency of antiretrovirals does not affect the level of virus hiding in these reservoirs.

In the new study, however, the researchers determined that the reservoir virus is not like typical HIV: It is dormant, and thus impermeable to known therapies. "So, if the cell lives, the virus lives," said Sekaly. "But if you zap the reservoir with a chemo, there is no more virus to allow it to come back."

The success of the new treatment approach will depend upon the patient's ability to control HIV using ART. If the patient responds favorably to ART, the new treatment can target infected cells, wiping out the last ones, and "the patient will remain virus-free for a long time or forever," Routy said. He added that 85 percent of HIV patients in Canadian hospitals and clinics are managing their HIV through ART and would be good candidates for eradication treatment. However, it is unlikely that patients not responding to ART would achieve significant results from the chemotherapy approach.

The study, "HIV Reservoir Size and Persistence Are Driven by T Cell Survival and Homeostatic Proliferation," was published in Nature Medicine (06.21.09; doi: 10.1038/nm.1972).

Source: Ottawa Citizen:: Amy Minksy, Canwest News Service; Courtesy of the CDC National Center for HIV, STD, and TB Prevention