Anthrax : Treatment and Prevention

by National Institute of Health

(Page 2 of 3)

Antibiotics

If diagnosed early, anthrax is easily treated with antibiotics. Unfortunately, infected people often confuse early symptoms with more common infections and do not seek medical help until severe symptoms appear. By that time, the destructive anthrax toxins have already risen to high levels, making treatment difficult. Antibiotics can kill the bacteria, but antibiotics have no effect on anthrax toxins.

Vaccines

An existing anthrax vaccine is licensed for limited use. The vaccine is currently used to protect members of the military and individuals most at risk for occupational exposure to the bacteria, such as slaughterhouse workers, veterinarians, laboratory workers, and livestock handlers. The vaccine does not contain the whole bacterium; rather, it is made mostly of the anthrax protective antigen protein.

Health experts currently do not recommend the vaccine for general use by the public because anthrax illness is rare and the vaccine has potential adverse side effects. Researchers have not determined the safety and efficacy of the vaccine in children, the elderly, and people with weakened immune systems. Although the results of recently conducted CDC vaccine trials indicate that three to four doses of anthrax vaccine can generate significant protective immunity, the recommended vaccination schedule is six doses given over an 18-month period. To quickly protect the public during a bioterror attack, scientists are seeking to develop a new vaccine.

NIAID Research

The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, conducts and funds research to improve our ability to prevent, diagnose, and treat anthrax. Anthrax research was under way prior to the 2001 bioterror attack, but it has expanded significantly since then. New research findings are improving our understanding of how B. anthracis causes disease and how to better prevent and treat it.

Basic research

Several biologic factors contribute to B. anthracis' ability to cause disease. NIAID researchers and grantees are uncovering the molecular pathways that enable the bacterium to form spores, survive in people, and cause illness. Scientists envision this basic research to be the underpinnings of new vaccines, drugs, and diagnostic tools.

Toxin biology

Scientists are studying anthrax toxins to learn how to block their production and action. Recently, scientists discovered the three-dimensional molecular structure of the anthrax protective antigen protein bound to one of the receptors (CMG2) it uses to enter cells. The separate structures of protective antigen and CMG2 previously had been determined, but the structure of both bound together is more valuable, much as a roadmap connecting two cities is more useful than separate maps of the cities. Using a specific fragment of the CMG2 receptor protein, researchers have been able to block the attachment of protective antigen in test-tube experiments, thereby inhibiting all anthrax toxin activity.

Previously, NIAID grantees had determined the three-dimensional structure of the lethal factor protein as it attaches to its target inside cells. Their research showed that lethal factor uses a long groove on its side to latch onto the target.

In another recent advance, NIAID and other scientists have synthesized a small cyclic molecule that blocks anthrax toxin in cell culture and in rodents. The molecule blocks the pore formed by anthrax protective antigen. Blocking the pore effectively prevents lethal factor and edema factor toxins from entering cells. The scientists anticipate that this discovery will lead to new and effective treatments for anthrax.

Anthrax bacterium genome

The instructions that dictate how a microbe works are encoded within its genes. Bacteria keep most of their genes in a chromosome, a very long stretch of DNA. Smaller circular pieces of DNA called plasmids also carry genes that bacteria may exchange with each other. Because plasmids often contain genes for toxins and antibiotic resistance, knowing the DNA sequence of such plasmids is important. Scientists have sequenced plasmids carrying the toxin genes of B. anthracis. In addition, researchers have sequenced the complete chromosomal DNA sequence of several B. anthracis strains, including one that killed a Florida man in the 2001 anthrax bioterror attack.

By comparing the DNA blueprints of different B. anthracis strains, researchers are learning why some strains are more virulent than others. Small variations among the DNA sequences of different strains may also help investigators pinpoint the origin of an anthrax outbreak. Knowing the genetic fingerprint of B. anthracis might lead to gene-based detection mechanisms that can alert scientists to the bacteria in the environment or allow rapid diagnosis of anthrax in infected people. Variations between strains might also point to differences in antibiotic susceptibility, permitting doctors to immediately determine the appropriate treatment.

Scientists are now analyzing the B. anthracis genome sequence to determine the function of each of its genes and to learn how its genes interact with each other or with host-cell components to cause disease. Genes are the instructions for making proteins, which in turn build components of the cell or carry out its biochemical processes. Knowing the sequence of B. anthracis genes will help scientists discover key bacterial proteins that can then be targeted by new drugs or vaccines.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.