Human immunodeficiency virus, once considered a slow if stealthy invader, actually works incredibly fast at disarming key immune fighters in the body, scientists at Duke University and UNC-Chapel Hill reported Monday.

What's more, HIV strikes an army of immune cells that scientists previously believed were less vulnerable early on.

The findings, reported in the online journal PloS Medicine, provide a better understanding of how to develop a vaccine to protect against the virus that causes AIDS. It newly infects an estimated 56,300 people a year in the United States.
"It's very helpful to us to know exactly what's going on" with the immune system, said Dr. Barton Haynes, who is an immunologist at Duke, director of the Center for HIV/AIDS Vaccine Immunology and the senior author of the study.

The insight was gained using technology pioneered at UNC-Chapel Hill that detects the virus within days of infection, rather than months. North Carolina began using the early detection methods at public health clinics, and a group of newly diagnosed patients agreed to participate in a study of how the immune system is affected at early stages.

Findings from these patients showed that three lines of attack by the immune system are quickly neutralized by HIV.

First, the virus wipes out the nurturing centers of the gut that harbor so-called B cells, infection fighters that originate in the bone marrow and congregate in areas of the small intestine.

In addition, HIV triggers a sort of smoke screen that provides it cover while the B cells spring into action, armed to fight every threat imaginable but unable to effectively target the real danger.

Finally, the virus also wipes out helper B cells, which are necessary for an effective response.

"To everyone's surprise, they found all this damage and cell death," said Dr. David Margolis, an AIDS researcher at UNC-CH and one of the study authors. He said the surprise was both in the timing of the onslaught, and in the target.

For years, HIV researchers focused on a different immune fighter -- T cells, killer cells formed not in the bone marrow, but in the thymus gland. HIV was known to take over T cells, destroying their ability to fight infections. But even with the new insights, Haynes said, scientists have a formidable task developing a vaccine.

"It would have to be different than any other vaccine made," Haynes said.