Confocal electron micrograph of Bacillus anthracis. CDC / Dr. Sherif Zaki / Dr. Kathi Tatti / Elizabeth White.

Disease control specialists in the US have embarked on a major initiative to prepare anthrax anti-toxin for emergency use in infected patients, today announced Nina Marano, co-ordinator of the Anthrax Vaccine Research Program at the Centers for Disease Control and Prevention (CDC).

The anthrax threat is greater than ever, says Marano. "We're in the eye of the storm; we haven't caught the perpetrator and we should be prepared for a much larger event."

This latest initiative will involve preparing serum from donors who have been vaccinated against anthrax. The donors enlisted so far are 400 vaccinees involved in a separate project with the US Army Medical Research Institute for Infectious Diseases (USAMRIID) at Fort Detrick outside Washington DC. They need to be vaccinated for occupational reasons, notes Marano.

Donor numbers are expected to grow with the re-institution of an anthrax vaccination program in the US military, says Marano. The program stalled after the US company that made the vaccine, BioPort in Lansing, Michigan, lost its licence in 2000. The licence was restored, to provide for a full-scale military vaccination program of 2.4 million service members, at the end of January this year. Some level of military vaccination program is expected to re-start this summer.

"You could have access, theoretically, to thousands of military vaccinees," Marano told BioMedNet News. "We're still waiting for Secretary Rumsfeld [US Secretary of Defense] to make the decision on when and how far the military program will spread."

With the 400 donors currently available, Marano anticipates she will have sufficient plasma, hundreds of liters, to approach a manufacturer with the capacity to purify immunoglobulins from such large volumes. Some plasma will also be set aside for use in emergencies; even unpurified plasma should contain sufficient specific immunoglobulin to protect patients who do not respond to antibiotics, she says.

"In terms of preparedness for the next event we are planning on saving stocks of fresh frozen plasma, which could be used immediately," said Marano. "We'll have to use it under informed consent," she added.

Animal research shows that immunoglobulin-G (IgG) against the anthrax toxin Protective Antigen (PA) is protective. Vaccinated individuals make anti-PA antibodies, and Marano predicts that administrating purified anti-PA antibodies to patients who have already been infected with anthrax could confer protection.

"Initially it would be used in patients who have failed antibiotic therapy," said Marano. "If we determine it is efficacious we would bump that up to use it ideally at the onset; as soon as an outbreak was detected."

The antibody could even be used as a prophylactic, she suggests. "One proposed use of it, this is kind of Star Wars stuff, is to put it into an inhaler and let a soldier use it in battle." If an anthrax attack was suspected, soldiers could inhale the spray to passively transfer antibodies mucosally.

Before that, though, studies must be carried out on animals, and then on ill patients. Studies on a rodent model are about to start, looking at the effect of different crude fractions of plasma from vaccinated individuals. Once a fraction that shows most efficacy has been found, this will be further investigated in the rhesus macaque.