‘Natural Killer’ Cells Unaffected by Antiretroviral Treatment, Serve as a Reservoir for HIV, Study Says
HIV is able to infect and hide in "natural killer," or NK, cells -- white blood cells that serve as the immune system's "first-line defense" against viruses and cancer cells -- possibly leading to a "permanent reservoir" of the virus in the body of those infected, according to a study by researchers from the National Cancer Institute published in today's Proceedings of the National Academy of Sciences, the Wall Street Journal reports. Researchers have long known that HIV can hide in CD4+ T cells, immune cells that coordinate immune system response, and monocyte macrophage cells, which destroy infected cells. Now they have discovered that the virus also infects NK cells, and that antiretroviral therapy seems to have little effect on lowering viral levels in the NK cells. "It's yet another reservoir we need to contend with," Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said, adding that the discovery "underscores the complexity of HIV, and its ability to persist in hosts despite therapy" (Chase, Wall Street Journal, 5/14). Dr. George Pavlakis and colleagues studied the effects of "aggressive" combination antiretroviral therapy in 10 treatment-naive patients with HIV. Although the treatment lowered HIV levels in the blood to undetectable levels in most patients, it did not rid CD4+ T cells or NK cells of the virus. Pavlakis said researchers will "be able to use this new information for good," noting that scientists "may be able to tailor future treatment methods to suppress or purge the virus from these cells." His team is already experimenting with different drugs to determine which, if any, will have an effect on the cells. Nucleoside reverse transcriptase inhibitors, a class of drugs that includes zidovudine and lamivudine, so far show the most promise (Stenson, Reuters Health, 5/13). Pavlakis stressed that the results were only preliminary and urged patients not to alter their treatment regimens on the basis of the findings (Wall Street Journal, 5/14).
Link Between HIV and Polio Vaccine Refuted
A separate study in today's Proceedings of the National Academy of Sciences "heaps doubt" on the theory that a tainted oral polio vaccine used in Africa half a century ago gave rise to the HIV/AIDS pandemic, USA Today reports. The polio vaccine theory, most recently put forth in the 1999 book "The River" by Edward Hooper, was supported by the fact that the earliest AIDS cases in Central Africa appeared at sites where the vaccine was administered in the 1950s. Supporters of the theory also noted that the vaccine was grown using the kidneys of non-human primates. They theorized that these kidneys came from chimpanzees infected with simian immunodeficiency virus -- the suspected precursor to HIV -- but they were never able to prove that chimp organs had been used in manufacturing the polio vaccine. The study published today confirms previous findings that the vaccine was cultured using organs from Rhesus macaque monkeys and not chimpanzees. The distinction is important because Rhesus macaques do not carry SIV (Sternberg, USA Today, 5/14). Researchers from the Pasteur Institute in Paris examined nuclear mitochondrial sequences -- DNA fragments also known as numts -- in the vaccine and found that the DNA "were derived uniquely from macaque genomes." The same team last year found that the mitochondria in the vaccine was macaque in origin. In the process of searching for the mitochondria they also located the numts and sought to further confirm that they were macaque in origin (Reuters Health, 5/13). "This issue is resolved," co-author Simon Wain-Hobson said (USA Today, 5/14).