Molecule That Directs Immune Cells to Intestines Also Serves as Receptor for HIV, Study Finds
A molecule called integrin alpha-4 beta-7 that naturally directs immune cells to the intestines also serves as a receptor for HIV, according to a study conducted by NIH's National Institute of Allergy and Infectious Diseases and published Sunday in the journal Nature Immunology, the New York Times reports. The study's findings have identified a new human receptor for the virus, according to the Times.
HIV rapidly infects the lymph nodes and lymph tissue found in the intestines, which become the primary location where the virus replicates, the Times reports. After HIV replicates in the intestines, the virus depletes the lymph tissue of CD4+ T cells. This situation occurs in all HIV-positive people regardless of the mode of transmission, the Times reports.
For the study, NIAID director Anthony Fauci and colleagues showed that a protein on the outer shell of HIV attaches itself to a molecule in the receptor that is linked to the way T cells find the digestive tract. The study also found that the binding of HIV to the molecule stimulates activation of another molecule, LFA-1, which helps spread the virus from one cell to another. These actions ultimately lead to the destruction of lymph tissue, according to the Times.
Fauci in an interview said the study "took nearly two years, and there's little doubt that what we have found is a new receptor" (Altman, New York Times, 2/11). He added, "It is the very molecule that steers lymphocytes to the gut and keeps them there." According to Fauci, "It is not only important in that it is a homing receptor to the gut. But it also can play a role in enhancing the ability of HIV to spread in the body." Elena Martinelli, a researcher involved in the study, said, "The gut is where the virus really takes hold." She added, "We found that integrin alpha-4 beta-7, whose natural function is to direct T cells to the GALT, is also a receptor for HIV. It is very unlikely that this is a coincidence" (Fox, Reuters, 2/10).
Warner Greene -- director of the Gladstone Institute of Virology and Immunology who was not involved in the study -- said the findings are "an important advance in the field." He added, "They begin to shed light on the mysterious process on why the virus preferentially grows in the gut." Fauci said he hopes the results will encourage other scientists from different disciplines to explore new ways to attack HIV, adding that drugs aimed at blocking the molecule also should be studied for their potential benefit in HIV/AIDS treatment (New York Times, 2/11).
The study abstract is available online.