HIV may well be the most studied virus of all time, but the steps between its introduction into the body through sexual intercourse and an established infection remains mysterious . Now, researchers reported intriguing evidence that a poorly understood protein may allow the virus to sneak behind the defenses of the body. In addition to clarifying the mechanism of the sexual transmission of HIV, the findings identify new targets for vaccines against AIDS.
The new work, presented in two articles in the cell on March 3 , was born studies of dendritic cells, the sentinels that alert the immune system when the violent invading the borders of the body . The researchers reported that a protein called DC-SIGN carries HIV dendritic cells in the mucosa of the cervix or rectum to distant lymph nodes. There, the DC-SIGN hands HIV in CD4 + T cells, immune cells that the virus easily infects and destroys, eventually leading to AIDS.
The team, led by Yvette van Kooyk, a tumor immunologist at the Medical Center of the St. Radboud University in Nijmegen, the Netherlands, conducted test tube experiments to learn how HIV interacts with DC-SIGN. The protein binds tightly to the virus, they report, stabilize during the trip of the lining to lymph nodes. This stabilization makes a huge difference: No DC-SIGN, HIV has lost its infectivity in less than a day. Protected by the protein, however, the virus could infect CD4 cells after 4 days.
On a practical level, the results can inform vaccine design. To date, many HIV vaccine designers aim to elicit antibodies that disrupt HIV fusion with CD4 its targets. Now, one might seek to induce antibodies that block the binding of DC-SIGN to HIV. "It is a very elegant work," said AIDS researcher Douglas Richman of the University of California, San Diego.
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