Mouth, skin tissue can spread HIV, Chinese scientists find
Outer skin layers still separate the mast cells from the as-yet incurable virus, which is why healthy people can’t get infected from a simple handshake or hug, team says
A type of cell commonly found in skin, mouth and gut tissue may be able to “capture” the HIV virus and introduce it to other cells where it can spread much more easily, according to a new study by Chinese scientists.
This mechanism for transmitting the disease suggests oral sex could be even riskier than was previously thought in terms of spreading this as-yet incurable disease, which can lead to AIDS.
The research team confirmed for the first time that the human immunodeficiency virus can bind with mast cells, which are found in connective tissue. The team was led by Professor Wang Jianhua at the Institute Pasteur of Shanghai, which runs under the Chinese Academy of Sciences.
Mast cells are found throughout the human body, especially under the surface of the skin, inside nerves, in the respiratory system, and in the digestive and urinary tracts.
“It doesn’t mean a healthy person can get infected from direct skin contact (with an HIV carrier) such as a hug or handshake,” said Wang, whose paper was published recently in the Journal of Virology.
“The outmost layers of the skin, such as the epidermis, can effectively keep the virus away from the mast cells.”
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Regardless, the discovery has rekindled fears of how dangerous or incurable sexual diseases can be transmitted.
Mast cells tend to concentrate in the inner lining of the mouth, throat, anus and rectum. In these thin membranes, they represent the body’s first line of defence against “alien” elements such as bacteria and viruses, as there is almost no barrier separating the two.
Doctors have long known that HIV can be spread from person to person through blood, sperm or other bodily fluids. But question marks remain over how the virus penetrates the immune system and moves from one person to another during sexual intercourse.
The cells that Wang’s team used in their experiments were extracted from the large intestine of a patient suffering from rectal cancer. The initial purpose of the research was to study in greater detail the way in which HIV is transmitted among homosexual men.
The scientists were surprised by the active role the mast cells played, as they were not previously believed to figure prominently in the equation.
However, they were found to operate like renegades or even traitors, sympathising with the virus and helping it on its way.
After identifying and capturing their prey, the mast cells did not kill the viral cells but rather transmitted them to other areas of the immune system such as T cells. Here, the virus can find a comfortable home to start reproducing on a huge scale.
The latest finding suggests that some government agencies may need to reconfirm the accuracy of their public messages. For example, according to www.aids.gov, an official website run by the US Department of Health and Human Services: “Oral sex poses little to no risk of getting or transmitting HIV.”
Wang said the discovery of the new transmission mechanism will help researchers better assess the risks involved, and hopefully find better preventive measures such as vaccines or medications.