By Neil Sherman,HealthSCOUT Reporter

FRIDAY, Sept. 1 (HealthSCOUT) -- The way the AIDS virus hitches a ride on the cells that help fight off infection may be a clue as to how the infection keeps going, scientists at the National Institute of Allergy and Infectious Diseases report for the first time.

Using newer, more sensitive technology to identify snippets of genetic material, the researchers peered at the surface of cells to show that HIV, the virus that causes AIDS, binds to B cells, the antibody factories of the immune system.

And since B cells talk to T cells -- the special class of cells vital for keeping the immune system strong -- the scientists say they believe the newly discovered vehicle may be one of the ways HIV infects T cells to keep the disease going.

"What we've discovered is one more piece of the puzzle that allows us to understand how the virus does so much damage to the immune system," says Susan Moir. She is a visiting fellow with the institute's Laboratory of Immunoregulation in Bethesda, Md. "What we are showing is that HIV binds to B cells and is totally capable of getting into T cells and replicating itself."

Other studies that showed that HIV could infect B cells in test tubes and that low levels of HIV genetic material can exist in B cells in HIV-infected patients, Moir isolated B cells from the blood of 23 patients with chronic HIV infection. Using tests that identify genetic material, Moir identified significant levels of HIV clinging to B cells in all 23 blood samples.

The findings are published in the Sept. 4 issue of the Journal of Experimental Medicine.

"What we found were spheres of full virus on the cells," Moir describes. "They are not replicating, but they make themselves available for replication, which they [then] do in T cells."

Peering closely at the surface of B cells, Moir saw exactly how a B cell interacted with the virus called CD21, a molecule that allows you to get mononucleosis. The fact that HIV binds to B cells explains why people with HIV get all those opportunistic infections, she says. "We know that B cells are abnormal in HIV. One of the reasons people with AIDS can't fight infections is because HIV knocks out the T cells by infecting them, and B cells have gone AWOL."

The fact that HIV binds to CD21 may explain why B cells go into overdrive when a person becomes infected. The virus "tickles" the B cell into producing antibodies.

"Overproduction of antibodies by B cells has been used as a marker for HIV infection," says Dr. Richard Feldman, a physician with the Callen Lord Community Health Care Center in New York City. "But whether that overproduction has any pathological significance is still unclear."

So will researchers be able to use CD21 or B cells as a way to fight AIDS?

"There is some potential to block the trapping and association between HIV and B cells," Moir says. "But as always with AIDS, we must be careful that we don't cause more harm than good." B cells are essential to the normal functioning of the immune system and must be handled with care, she adds.

What To Do

"The study certainly is another interesting piece of the puzzle. But whether it will impact day-to-day treatment of HIV remains to be seen," says Feldman.

For more information about how HIV attacks B cells, and T cells, visit the HIV/AIDS Information Center. And to learn what you can do to prevent HIV infection, check out HIV InSite.

(From HealthScout)