Cytokine key to smallpox infection

Scientists at the Australian National University (ANU) have identified the immune response that determines why some mice are infected with mousepox and others are not, a discovery that could lead to better protection for humans in a bio-terror attack.

Mice that are resistant to mousepox, a close relative of the smallpox virus, produce three regulatory proteins called cytokines that are absent in mice that become infected.

The findings raise the possibility of identifying humans vulnerable to smallpox and targeting vaccination and treatment in the event of an outbreak, said ANU immunologist Gunasegaran Karupiah, who headed the discovery team.

"This is an important step towards better protection from the threat of smallpox for health workers and the general community," he said.

Scientists know relatively little about the immune response to smallpox because the virus was eradicated decades ago after a successful worldwide vaccination programme. Smallpox was highly contagious and killed around 30 percent of those infected.

After the September 11, 2001 airliner attacks on New York and Washington there have been fears that terror groups may develop smallpox as a biological weapon.

"Smallpox was one of the biggest human scourges...yet because it was successfully eradicated no one was interested in understanding how individuals recovered, but now the interest is back because of the threat of bio-terrorism," said Karupiah.

Smallpox produces flu-like symptoms and a distinctive and disfiguring rash. It has an incubation period of around 12 days. Symptoms include tiredness, chills, fatigue and fever followed by pustules that erupt mainly on the face and limbs.