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August 25, 2008
Study: Lymph nodes may hold key for new strategy to fight viruses

By Quinn Eastman

Seeing disease-fighting white blood cells vanish from the blood usually signals a weakened immune system. But preventing white blood cells’ circulation by trapping them in the lymph nodes can help mice get rid of a chronic viral infection, Emory vaccine researchers have found.

Their findings, published Aug. 14 in Nature, suggest a new strategy for fighting chronic viral infections that could apply to the treatment of human diseases such as hepatitis C and HIV/AIDS.

The team’s discoveries grew out of their study of two varieties of a virus that causes meningitis in mice, said immunologist John Altman, who is based at Yerkes National Primate Research Center.

Mice can fight off infection by the Armstrong strain of lymphocytic choriomeningitis virus, but are vulnerable to chronic infection by a variant called clone 13.

Altman, postdoctoral fellow Mary Premenko-Lanier and co-workers found that infecting mice with the Armstrong strain sequesters white blood cells in the lymph nodes, while clone 13 does so less stringently.
“Our hypothesis was that if we could artificially induce conditions like those produced by the Armstrong strain, it would help the immune system clear an infection by clone 13,” Altman says.

His team turned to an experimental drug called FTY720, which prevents white blood cells from leaving lymph nodes and was previously thought of as an immunosuppressant. While not approved for sale by the FDA, doctors have tested it for the treatment of multiple sclerosis and preventing kidney transplant rejection.

Even if mice have a chronic clone 13 infection, treatment with FTY720 can still improve their immune response enough to have them rid it from their systems, the authors found.

Altman and his co-workers are planning to test FTY720’s effects in animals with other viruses such as relatives of HIV, Epstein Barr virus, and polyoma virus.