BACKGROUND: More than 1 million people living in the United States are living with HIV/AIDS. Each year, more than 40,000 people will be diagnosed with it. The Centers for Disease Control reports 74 percent will be men. African Americans, who make up just 12 percent of the population, account for almost half of the HIV/AIDS cases. HIV is transmitted by a person who is HIV–infected and can be transmitted by blood, semen, vaginal secretions and breast milk. The most common ways HIV is transmitted is unprotected sex, unprotected oral sex, sharing needles and infection during pregnancy, childbirth and breastfeeding.
WHAT WORKS? More than 20 drugs are currently available for treating HIV. Because HIV genes mutate so easily and the virus reproduces so rapidly, most people who are infected have many different forms of the virus in their bodies. In some cases, mutated strains take on new properties that make them more resistant to the drugs used in antiretroviral therapy -- the primary means of treatment for HIV infection. During antiretroviral therapy that does not fully suppress the virus, a strain that develops drug resistance will grow more quickly than strains lacking such resistance, and the resistant strain will replicate to become the most prominent virus in the person's body.
A NEW TEST: Researchers at Duke University Medical Center have developed a highly sensitive test for identifying which drug-resistant strains of HIV are harbored in a patient's bloodstream. The test may provide physicians with a tool to guide patient treatment by predicting if a patient is likely to become resistant to a particular HIV drug, said one of its developers, Feng Gao, M.D., associate professor of medicine. Drug resistance is one of the most common reasons why therapy for HIV, the virus that causes AIDS, fails.
WHY IT’S DIFFERENT: The Duke test examines the genes of HIV strains for mutations at certain positions that are known to be linked to drug resistance. The researchers analyze blood samples from three different groups of HIV patients: those who had never received antiretroviral treatment, those who had received treatment but were not currently being treated and those who were receiving treatment, but the treatment was not completely successful. After processing the blood samples and isolating the genetic material in each of them, the researchers added tiny fluorescent tags designed to stick to HIV genes in particular ways. Tags designed to stick to mutated gene locations known to produce drug resistance were labeled to appear green, while tags designed to stick to the same gene locations but where the genes had not mutated were labeled to appear red. The researchers used a sophisticated computer program to count the number of molecules with green or red fluorescent tags in each sample. The test proved sensitive enough to detect a single mutated virus out of 10,000 nonmutated viruses in the patient samples.
NOT JUST HIV: The test may have a broader medical application as well. It has the potential to detect mutations that confer drug resistance in hepatitis B, hepatitis C and tuberculosis.
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