Florida researchers discover how anthrax shuts down immune system

From the annals of anthrax: researchers at the University of Florida have made an interesting breakthrough in understanding how inhaled anthrax paralyzes the body’s defenses and prevents immune cells from reaching the site of infection. Those infected typically feel flu symptoms for weeks, but once the first symptom appears, the disease progresses rapidly and patients often die from shock before they realize they have more than a common cold. Early diagnosis is key in the aftermath of a known terrorist attack, but the current method of detecting anthrax relies on lab cultures that can take days to complete. “We’re looking for approaches to detect anthrax earlier in the blood,” said professor Russell During. “We’re trying to develop a test that would allow detection within two or three hours of the bugs entering the blood and secreting toxins.”

Once inhaled, anthrax releases a lethal toxin that immobilizes the white blood cells that normally seek and destroy invading bacteria. Just traces of the toxin can slow movement of these cells, known as neutrophils, by 50 percent, UF researchers discovered. “Neutrophils have to get to the infection to kill anything. If you paralyze them so they don’t move, they can’t protect you,” said Dr. Fred Southwick. But exactly how the anthrax toxin wards off neutrophils has puzzled scientists for years. Immune cells rely on rod-shaped filaments called actin to propel them toward an infection. In a previous study, Southwick found that the toxin prevents actin assembly, leaving neutrophils stuck in the mud. “Actin is important because it’s the motor that causes neutrophils to move,” said Southwick. “So it’s like cutting the gas to the motor.” The toxin works like a pair of scissors, snipping off the ends of a key protein and preventing the transmission of messages within the cell. As a result, immune cells never receive the green light to assemble the actin motor, the researchers found.