Scientists have hypothesized that HIV hijacks immune cells known as dendritic cells to infiltrate the immune system. Dr. Benhur Lee and colleagues at the University of California-Los Angeles (UCLA) AIDS Institute have shown that blocking HIV's access to a naturally occurring molecule on dendritic cells may decrease their ability to smuggle the virus into other immune cells.

"Dendritic cells act like sentries to alert the immune system when a foreign agent tries to infiltrate the body," Lee said. "They also produce a molecule called DC-SIGN that plays a critical role in the sexual transmission of HIV. We wanted to see what would happen if we blocked how DC-SIGN functions in its natural environment."

Dendritic cells are in the mucosal linings of the mouth, gut, genital, and urinary tracts -- sites where sexually transmitted HIV often enters the body. The UCLA team was the first to study dendritic cells in their natural setting instead of in a test tube. The researchers examined biopsies of human rectal tissues.

Using a sugar-like compound that binds to DC-SIGN and a DC-SIGN-seeking antibody, the scientists successfully blocked HIV from binding to dendritic cells.

"Our findings suggest that preventing HIV from binding to the dendritic cells may block their ability to carry HIV to other parts of the immune system," Lee said. "Our next step will be to investigate if this is true."

"We believe our findings point to a new therapeutic target for preventing HIV infection," said Dr. Peter Anton, UCLA professor of medicine. "Drugs could be developed to block the interaction between HIV and DC-SIGN, potentially reducing HIV's ability to spread infection at mucosal routes into the body."

The article, "Binding and Transfer of Human Immunodeficiency Virus by DC-SIGN+ Cells in Human Rectal Mucosa," appeared in the Journal of Virology (2005;79:5762-5773).

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