The daily, deadly duel that pits U.S. forces against foes in Iraq sees no end in sight. Meanwhile, a no less dangerous power took the lives of five Americans in the closing months of 2001. Instead of bombs and guns, this implacable invisible terror weapon used envelopes charged with pathogenic bacterial spores.

Those spores may eventuate in inhalational pulmonary anthrax, the direst fatal version of the bacillus, which presumably took the lives of those five Americans. Initial symptoms of inhalational anthrax tend to resemble the flu, followed by cyanosis (skin and lips turning blue marking oxygen starvation). Then toxic shock, coma and death ensue.

"If you are infected with anthrax," observed biochemist and immunologist Julia Wang at Harvard-affiliated Brigham & Women's Hospital in Boston, "Bacillus anthracis can replicate in your body without being attacked by your immune system. Which means your immune defenses are not capable of eliminating the life-threatening bacilli. The reason? Because the B. anthracis pathogen's membranous surface is coated with a capsule made of poly-gamma-D-glutamic acid [PGA]. Just picture the capsule hiding the bacterium from the human host's immune system - allowing it to replicate unchallenged. Thus the immune system wouldn't be able to recognize this as a dangerous pathogen."

Wang is senior author of a paper released online the first week of September in the Proceedings of the National Academy of Sciences (PNAS). It's titled "A dually active anthrax vaccine that confers protection against both bacilli and toxins."

"Our overall finding in this article," Wang told BioWorld Today, "is toward developing a much safer and more effective vaccine based on a defined molecular component target. Existing vaccines," she pointed out, "primarily target the anthrax toxins, whereas our new vaccine targets both toxins and infectious bacteria. That is, it has two components. One would raise protective antibodies against B. anthracis toxins, while the other would be making antibodies against the bacilli itself. Anthrax disease is involved in both components. One is infection inflicted by the bacilli. The other is poisoning by the anthrax toxins.

"An important point," she added: "This is a new vaccine, and we predict it will be more effective than the present ones in use today. We expect ours will be able to stop infections at an earlier stage than antitoxic treatment alone. So hopefully ours will target this infection at the infectious stage."

Defeating Infection Now, Toxins Later

"The current vaccines target the toxin stage," Wang pointed out, "which means that the infectious stage has already taken place before a lot of toxins are secreted and then targeted. Because anthrax has two components we identify two targets - one for infection caused by the bacilli replication; the other factor is the toxic shock. So we thought in order to stop the disease, or cure it completely, our new vaccine must arrest both targets. Just neutralizing toxin, as the current vaccines do, is not going to be enough. To start with, we had to find targets in both. One of these target toxins in the existing vaccine is PA, short for protective antigen' - a protein component of anthrax toxin.

"Anthrax toxin consists of three proteins," Wang explained. "The central part is PA. The other two proteins are called lethal factor [LF] and edema factor [EF]. So PAs can bind to either LF or EF. By raising antibodies that can bind to PA we would be able to prevent the formation of toxins. This is true because if we have the PA surface capsule coated by this antibody the LF or EF would not be able to bind to PA any more. Even if the toxin is formed, it wouldn't be able to bind to the host cells if there is a toxic effect.

"Since the immune system is not able to kill the bacilli," Wang continued, "the bacilli can keep growing and growing. So in our vaccines we are trying - unlike antibiotics such as the CIPRO antibacterial - to raise antibodies to kill bacilli. We derive PA from cloning recombinant Escherichia coli. And the PGA we isolate from another bacillus, namely Bacillus licheniformis - a molecular look-alike to B. anthracis. B. licheniformis is a harmless nonpathogen, which means it's safe to use in quantity as a pinch-hitter in our in vivo experiments.

"Proteins of the complement system do the actual killing," Wang noted. "For this we have antibodies. They can bind to toxins or to phagocytes. Without antibodies, the immune system is not very efficient at killing a lot of pathogens. Mice are very susceptible to anthrax, but we couldn't use real live anthrax organisms in our experiments. Therefore we tested both functions of the vaccine separately against toxins, so we could give the mice infection or toxicity. And the animals that were not vaccinated but generated antibodies survived. To test that against Bacilli licheniformis vs. the PA, we challenged those mice by combining LF and PA. Those are two discrete proteins. By themselves they're not toxic. Only when we mix them do they become deadly. So we isolated those proteins separately and injected this toxic mixture into the mouse tail veins. The animals had no means of protection and all of them died in a day."

Mice That Make Antibodies Make Do

"Our ongoing work now is trying to make this project into a vaccine product," Wang said. "To get there we need access, to find a collaborator who can test all the vaccines in a real disease scenario; challenge the animals with anthrax spores to see how effective our vaccine is against real spore challenge. And we also want to test the formulation of the structure for the vaccine. And seek answers to questions on their immunogenic profile: What's the optimum dose? Optimum vaccine? Vaccination schedule? How many vaccine shots are necessary, at what intervals? How long will the immune memory last?

"The university and hospital filed patent applications in March or April," Wang allowed. "I am the principal inventor. I designed the vaccine, developed the experiments, and am also the major licensee. Now," she concluded, "I'm looking for industrial partners to develop our new vaccine into a real product."