A new human receptor called integrin alpha 4 beta 7 that helps the HIV virus in attacking the body's immune system has been identified.
Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, who headed the research team said, "It is a homing receptor for lymphocytes to get to the gut. It is the very molecule that steers lymphocytes to the gut and keeps them there."
The human immunodeficiency virus, or HIV, attacks immune system cells, or lymphocytes, known as CD4 T-cells. Earlier studies have shown that the HIV uses three main receptors, or molecular doorways, to infect cells: CD4 was identified as a HIV receptor in 1984, CCR5 and CXCR4 were identified in 1996.
A similar receptor called integrin alpha 4 beta 7 has been found by Dr. Fauci, James Arthos, Claudia Cicala, Elena Martinelli and their colleagues.
After the HIV virus enters the body, this receptor helps it to reach the gut or intestine. A protein on the virus's envelope, or outer shell, sticks to a molecule in the receptor.
Much of the body's immune response takes place in the gut, in gut-associated lymphoid tissue, or GALT. Once the HIV is in the gut, the virus begins to replicate and attack the body's immune system.
Scientists have been experimenting to identify receptors because they offer targets for the development of new classes of drugs. For example, last year the Food and Drug Administration approved for AIDS treatment a Pfizer drug, Selzentry or maraviroc, which works by blocking CCR5.
Dr. Fauci said that a number of experimental drugs that block the integrin alpha-4 beta-7 receptor are being tested for the treatment of autoimmune disorders. According to him such drugs should also be studied for making headway in AIDS treatment. For example, Tysabri (natalizumab) that is used to treat multiple sclerosis, could be explored for its potential in AIDS treatment, he said. Biogen/Elan makes Tysabri.
Dr. Warner C. Greene, an AIDS expert and the director of the Gladstone Institute of Virology and Immunology who was not involved in the research, called the findings "an important advance in the field."
"They begin to shed light on the mysterious process on why the virus preferentially grows in the gut," he said in an interview.
Some of the ways in which HIV is known to infect the body are, through sexual intercourse, blood transfusions and blood contamination of needles and syringes, There is no known cure for AIDS. More than 33 million people are infected with HIV globally and 25 million have died of AIDS. There is no vaccine to prevent AIDS.