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| health > AIDS > story page |         |
Scientists discover a curveball in treating HIV infectionNovember 11, 1999
By Rochelle Jones (WebMD) -- A new study suggests that the human immunodeficiency virus (HIV) may be more difficult to eradicate than scientists previously thought. According to the research, published in this week's issue of the journal Science, HIV may have the capability to invade not only activated T4 cells, the virus' primary target, but ones at rest as well, creating a small but resistant population of infected cells.
Anti-retroviral medications -- developed to treat HIV infection -- can fight the virus in activated cells. But the infected resting cells are affected little by the medication and can continue to harbor the virus, said Ashley Haase, M.D., head of University of Minnesota's microbiology department in Minneapolis and co-author of the study. "This means that current drug therapy is not effective against long-lived cells that are infected with the virus," Haase said, referring to the resting cells. We "are going to need some new therapeutic approaches altogether if we are going to talk about eradication." Referring to the research as a "good scientific study," Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Disease, said the results show that developing a vaccine may be more challenging than previously supposed. "It implies that any strategy against AIDS has to keep in mind these pools of resting cells," Fauci said. Almost 700,000 cases of AIDS in the United States have been reported to the Centers for Disease Control and Prevention since the epidemic began in the early 1980s, he said. More than 40,000 new cases of HIV infection are diagnosed every year; about one-half of those infected are under the age of 25, and most were infected through sexual activity. Researchers in the study simulated sexual transmission in 14 female rhesus monkeys by inoculating them in the vagina with the simian immunodeficiency virus, the form of HIV that affects monkeys. Then the researchers checked the monkeys every three or four days to identify the types of cells that the virus had invaded. They found that the virus could invade T4 cells immediately after sexual transmission -- contradicting the prevailing theory that the virus first infects other cells, which later pass the infection on to T4 cells. The research also suggests that anti-retroviral medications may not affect the resting cells -- which are latent and chronically infected -- despite persistent treatment. The result underscores the limitations of current medication therapies, said Haase, and the challenges of developing a vaccine to eliminate the virus entirely. The use of anti-retroviral drugs has contributed to a 47 percent decline in AIDS deaths between 1996 and 1997, Fauci says, referring to CDC figures. But many people infected with HIV don't respond to the therapy, can't tolerate the side effects or have difficulty following the complicated treatment regimens. Mario Stevenson, Ph.D., professor of microbiology at the University of Massachusetts Medical School, said the study may eventually lead to new approaches to HIV treatment because the results challenge long-held assumptions about the virus and its effect on cells. "It may sound like good news, but it's actually bad news ... our therapies may be less effective than we have thought," Stevenson said. "This changes the playing field."
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