The AIDS virus has an accomplice that helps it infect the immune system cells it attacks -- other immune system cells, U.S. researchers reported on Saturday.

In fact, these other cells, known as B cells, may be key to infection, the University of Pittsburgh researchers told an international AIDS conference. "The research supports a new role for B cells in the development and spread of HIV between cells," said Dr. Charles Rinaldo, who led the study.

The findings may help find a way to block infection, and help explain why the virus can hide out in "reservoirs" inside the body for decades.

The AIDS virus is especially hard to fight because it infects the immune system. It favors cells called CD4 T-cells.

It gets into the cells using two molecular doorways, called receptors. They are CD4 and either CCR5 or CXCR4 and are found only on T-cells.

Other immune cells were thought to be uninvolved. But Rinaldo's team found that other immune cells called B cells make a protein called DC-SIGN that seems necessary for HIV to ever infect a cell.

The researchers looked at B cells from 33 healthy subjects and 20 adult patients with HIV. About 8 percent of these cells expressed, or made, DC-SIGN.

One study showed that B cells harbored viruses that could be transmitted to T cells for as long as two days. HIV had little effect on the T cells when B cells were not around.

The researchers found a compound that blocks DC-SIGN.

When they blocked DC-SIGN in B cells, and put them in with T-cells in a lab dish, the virus was unable to infect the T-cells, the researchers said in a statement to be presented more fully at the 16th International Conference on AIDS being held in Toronto.

There is no cure for the AIDS virus, which infects about 40 million people globally and has killed 25 million since it was first noted in the early 1980s. There is also no vaccine.

Drugs can help control it but the virus cannot be eradicated from the body. Understanding how it infects cells may help scientists discover how to clear it from the body or prevent infection in the first place.

(For more stories related to the International AIDS Conference, please go to http://today.reuters.com/news/globalcoverage.aspx?type=aids&src= GLOBALCOVERAGE_wire)

http://news.yahoo.com/s/nm/20060813/sc_nm/aids_accomplice_dc_1