New clues on how HIV enters the body
New clues on how HIV enters the body
People sexually exposed to HIV-1 receive two types of the virus, known as M-tropic and T-tropic, government scientists have discovered. They also have found that only the M-tropic type seems able to establish infection after sexual contact.
The finding is curious because the immune cells that first encounter HIV-1 on genital surfaces, called Langerhans cells, should be susceptible to infection from both forms of the virus. Yet, previous work has shown that after sexual transmission, the T-tropic virus stays locked out of Langerhans cells.
Researchers would like to know why this happens, saying the answer could provide important new clues for vaccine development or other HIV treatments. In the December issue of Nature Medicine, a team of scientists report they now have an answer. They say that while in the skin a site that closely reflects what happens on genital surfaces Langerhans cells fail to produce a surface protein that the T-tropic virus needs to chemically unlock the cell membrane and come inside.
Just as significantly, they found that Langerhans cells produce adequate levels of another surface protein that the M-tropic virus uses, like a key in a lock, to enter these immune cells and infect them.
"We hypothesized that this might be the case, but there was no direct evidence to support this hypothesis," said Andrew Blauvelt, MD, an author of the paper and a scientist in the Dermatology Branch at the National Cancer Institute. "We now have that direct evidence." t
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