Anthrax bacteria (Bacillus anthracis), stained

Photo courtesy Public Health Image Library

What Happens When it Enters the Body?

When viewed at the cellular level, an anthrax bacterium looks like a jointed bamboo rod. When it enters the body and finds the environment it needs, it moves to the lymph nodes. From there it begins to multiply and produce a toxin that attacks human cells resulting in hemorrhaging, swelling, a drop in blood pressure and ultimately death.

The way it attacks the cells and exactly what it does was in question for many years. Research that began in the mid 1980s has revealed some interesting facts about the behavior of the anthrax bacterium when it finds a host.

Researchers found that there are three proteins that are created by the anthrax bacteria. These proteins are harmless individually, but together can be deadly. These proteins are referred to as:

  • Protective antigen (PA)
  • Edema factor (EF)
  • Lethal factor (LF)

When these proteins are released, the protective antigen binds to the cell surface and forms a type of channel in the cell membrane that allows the edema factor and lethal factor to enter the cell. The edema factor, when combined with the protective antigen, forms a toxin known as the edema toxin. The lethal factor, when combined with the protective antigen, forms a toxin known as the lethal toxin. It is the lethal toxin that does the most damage within the cell.

Research in 1998, by George Vande Woude at the National Cancer Institute in Frederick, MD, revealed clues to what the lethal toxin does to the cells. He found that the lethal factor cuts enzymes in two -- the enzymes that are responsible for transmitting signals within the cells. He also identified the enzyme in question. He was studying the mitogen-activated protein kinase (MAPK) pathway, which helps control cell growth, embryonic development and the way oocytes (eggs) mature. He was specifically looking for information about what the pathway actually did in the oocyte maturation cycle, so he searched for compounds that blocked the activity of the MAPK. A database search lead him to the lethal factor.

It is still not completely understood why disrupting the signal transmission within the cell results in the symptoms anthrax generates, but research continues. Research is also being done to find ways to alter the protective antigen to disable its ability to allow the entry of the lethal and edema toxins into cells.