BIOTERRORISM: Researchers Tout Combination Anthrax-Smallpox Vaccine

Oct. 8, 2010
By Chris Schneidmiller
WASHINGTON -- A team of U.S. researchers has developed a single vaccine that appears to provide protection against both anthrax and smallpox, two lethal diseases that top the list of potential bioterrorism agents
The new countermeasure proved more effective than existing vaccines in protecting animal test subjects exposed to the diseases, according to the National Cancer Institute. It also could resolve drawbacks identified in licensed products, such as treatment of patients with suppressed immune systems, the federal agency said in a press release.
"We believe our dual vaccine ... which is effective against two of the most deadly pathogens, will help consolidate and simplify our national bioterror counterefforts by streamlining the manufacture, stockpiling, and swift deployment of such vaccines should the need arise," the authors said in a research article, published this week in the Proceedings of the National Academy of Sciences.
Fears of a bioterrorist event increased drastically in the wake of the Sept. 11 attacks and the anthrax mailings that followed just weeks later. A panel of experts led by former Senators Jim Talent (R-Mo.) and Bob Graham (D-Fla.) declared in 2008 there was a significant potential for a WMD event within five years, with bioterrorism being more likely than a nuclear strike due to the availability of disease materials (see GSN, Jan. 26).
The United States has directed billions of dollars toward promoting development of countermeasures for pathogens that could be exploited by extremists. It maintains stocks of vaccines for both anthrax and smallpox, ready for rapid shipment to any location within the United States.
The research article, though, points the way to what its contributors believe would be a notable improvement to U.S. biological defenses.
Scientists from the National Cancer Institute and other research institutions created the new treatment by combining the existing licensed smallpox vaccine with a chemical that augments immunity and genes for the protective antigen for anthrax.
The researchers treated a group of nine rabbits with the combination vaccine and an equal-sized selection with BioThrax, the only anthrax vaccine licensed for use in the United States. After 28 days, serum samples from animals that received the dual treatment showed significantly higher levels of disease-fighting antibodies than their counterparts, according to the article. Similar results were found 21 days after the rabbits received secondary booster shots.
At that point the rabbits from both groups were exposed to inhalation anthrax. All animals that received the hybrid treatment tested negative for infection after six days, while one of the other test subjects tested positive for the presence of anthrax bacteria in the blood.
Testing on mice also showed that the dual vaccine offered similar protection levels to BioThrax, both 21 days after the animals received a booster shot and six months after vaccination. However, the experimental treatment appeared to provide defense more rapidly -- roughly 33 percent of mice survived exposure in one test three days after receiving a single dose, while only 10 percent of mice lived after receiving BioThrax under those conditions. The scientists reported similar results in mice exposed to anthrax six days after vaccination.
Though the study does not offer details, the National Cancer Institute release says the new vaccine also demonstrated greater effectiveness than the licensed ACAM2000 smallpox vaccine in safeguarding mice and monkeys against the disease.
More than 8.5 million doses of BioThrax have been delivered to the U.S. Strategic National Stockpile of emergency medical countermeasures, according to Maryland-based manufacturer Emergent BioSolutions. The biopharmaceutical company produces roughly 8 million doses each year.
"While certainly interesting science, its vital to note this research is still in the very earliest of stages," Emergent spokeswoman Tracey Schmitt said by e-mail. "What this study does underscore is that the threat of anthrax remains, unfortunately very real. Emergent is proud to have the government's trust and commitment to our FDA-approved anthrax vaccine."
Roughly 200 million doses of ACAM2000 have been produced for the U.S. stockpile. "We applaud the U.S. government for working on the development of a dual vaccine," manufacturer Sanofi Pasteur said in a statement today.
The U.S. Centers for Disease Control and Prevention, which manages the Strategic National Stockpile, referred questions about the relative efficacies of the vaccines back to the cancer institute, a branch of the National Institutes of Health.
"It is important to emphasize that the vaccinia-based dual vaccine ... not only is superior in immunogenicity and efficacy in comparison with the currently licensed vaccines against smallpox and anthrax, but also remedies the inadequacies associated with such licensed vaccines," the researchers said in the new article.
Smallpox vaccination can produce side rashes, fever and other effects in some recipients and might prove dangerous to people suffering from weakened immune systems or eczema. The dual vaccine, though, was less dangerous to "immune deficient" mice, suggesting it would perform similarly in afflicted humans, according to the NCI release.
Sanofi Pasteur countered that the "current, licensed vaccine is the same one that was used to eradicate smallpox" in nature. "The frequency of the side effects ... are rare to very rare."
National Cancer Institute staff scientist Linyange Perera, one of the article's authors, told Global Security Newswire that the experimental vaccine does not contain biologically active anthrax toxin, which is generally believed to be connected to "adverse effects seen following the administration of BioThrax."
The new treatment can also be freeze dried, avoiding potential troubles in keeping the material at the correct temperature and making it more easily stored and shipped in the event of a bioterror incident, the institute said.
"We believe that these features make [the dual vaccine] a preferred choice for integrating into our national biodefense preparedness agenda to protect the nation by enhancing the capabilities of rapidly responding to and recovering from a devastating attack involving these bioweapons of mass destruction," the researchers said.
The next step in the project is testing the vaccine's ability to protect nonhuman primates against inhalation anthrax and intravenous monkeypox -- a disease similar to smallpox, Perera said by e-mail. That would be followed by testing in human volunteers of the product's safe capability to produce an immune response.
Talks are under way with vaccine manufacturers and licensing and production could begin in two to three years, the scientist said.
http://www.globalsecuritynewswire.org/gsn/nw_20101008_9204.php