HIV-2: a less virulent cousin of HIV-1.A new report confirms the milder nature of HIV-2, a close cousin of HIV-1. Both HIV-1 and HIV-2 cause AIDS, a disease that decimates the immune system immune system Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. and causes death. Researchers first demonstrated the existence of HIV-2 in a 1985 study conducted in the West African West Africa A region of western Africa between the Sahara Desert and the Gulf of Guinea. It was largely controlled by colonial powers until the 20th century. West African adj. & n. country of Senegal. Since that time, virologists have shown that HIV-2 is more prevalent in West Africa West Africa A region of western Africa between the Sahara Desert and the Gulf of Guinea. It was largely controlled by colonial powers until the 20th century. West African adj. & n. than HIV-1. And preliminary reports indicated that this virus is less virulent than HIV-1, which is responsible for the vast majority of AIDS cases in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. . Now, a study of 574 prostitutes in Dakar, Senegal's capital, quantifies more precisely the characteristics of HIV-2. U.S. and African AIDS researchers started their study by monitoring prostitutes who were registered by the Senegalese government and therefore were tested frequently for sexually transmitted diseases Sexually transmitted diseases Infections that are acquired and transmitted by sexual contact. Although virtually any infection may be transmitted during intimate contact, the term sexually transmitted disease is restricted to conditions that are largely , such as AIDS. The researchers discovered dramatic differences when they compared women who became infected with HIV-1 during the study to those infected with HIV-2. Five years after infection, one-third of the women infected with HIV-1 had progressed to AIDS. In contrast, none of the HIV-2-infected women had developed the disease. Another key indicator of HIV-2's less vicious nature showed up in a laboratory test of the immune system. Each year, about 10 percent of the women infected with HIV-1 showed an abnormally low number of CD4 T lymphocytes, a type of white blood cell destroyed during the disease process. People with decimated CD4 T lymphocytes often develop the opportunistic infections Opportunistic infections Infections that cause a disease only when the host's immune system is impaired. The classic opportunistic infection never leads to disease in the normal host. that lead to death. Annually, just 1 percent of the HIV-2-infected prostitutes experienced such a plunge in CD4 counts. The study appears in the Sept. 9 Science. For people infected with HIV-2, long-term survival without developing severe illness or AIDS may prove the rule rather than the exception, says lead author Richard Marlink of the Harvard School of Public Health The Harvard School of Public Health is (colloquially, HSPH) is one of the professional graduate schools of Harvard University. Located in Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill, next to Harvard Medical School and Cambridge, Massachusetts, in Boston. Additional studies of the differences between the two viruses may provide clues about how to fight HIV-1, he adds. |
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