Cell Protein Gives Monkeys Innate Immunity to H.I.V., Researchers Discover
By GINA KOLATA

Published: February 26, 2004

Scientists have discovered that monkey cells have innate protection against infection with the human AIDS virus, a clue that may help explain why some people are susceptible to certain viral infections while others are not.

The finding, reported in today's issue of the journal Nature, offers one of the first concrete examples of what researchers call an intracellular system of innate immunity and may open the door to the development of new antiviral therapies, the scientists said.

The monkeys were protected from the virus by a mechanism that resides within cells and that is independent of the antibodies and white blood cells of the immune system. The mechanism appears to have evolved to protect animals from specific viruses.

In the case of AIDS, the researchers found, the monkeys blocked the human immunodeficiency virus, or H.I.V., as soon as it slipped into cells, using a protein that prevented the virus from shedding the hard casing around its genes. The protein, called TRIM5-alpha, apparently floats inside the monkey cells, looking for H.I.V.

"This is really telling us about a system of natural immunity to viruses," said Dr. Joseph Sodroski, a professor of pathology at Harvard's Dana-Farber Cancer Institute who was the lead author of the study. He described the protective mechanism used by the cells as "very specific, very potent and very targeted to particular viruses."

Dr. Nathaniel R. Landau, an AIDS researcher at the Salk Institute in San Diego, called the study "excellent," and predicted, "I think it's going to open up a new avenue of research."