Infection by Anthrax Spores Requires a Host Membrane Protein

The emergence of anthrax as a major bio-terror weapon has stimulated molecular microbiologists to search for the key to understanding how the bacteria invade host cells.

The inert spore of Bacillus anthracis is the infectious form of the organism that first contacts the potential host, therefore interaction between the host and spore exosporium is vital to the initiation of disease. Investigators at the University of Alabama (Birmingham, USA) worked with both cell cultures and well-documented strains of laboratory-bred mice to study their interaction with a strain of anthrax often used in research.

They reported in the January 23, 2008, online version of the journal Proceedings of the [U.S.] National Academy of Sciences (PNAS) that the host's integrin (integral membrane protein) Mac-1 was essential for the recognition of the major exosporium protein BclA by phagocytic cells. Results showed that the Mac-1/BclA interaction played a major role in B. anthracis pathogenesis by promoting spore uptake by phagocytes and subsequent access to a favorable niche for transport, germination, and outgrowth in lymphoid tissues.

"We know anthrax infection can occur in wild and domestic animals, but in humans this disease is extremely rare and very dangerous,” said senior author Dr. John Kearney, professor of microbiology at the University of Alabama. "This study reveals the biological paradigm that makes the anthrax spore clever enough to target the Mac-1 receptor and use this entry point to boost its lethality.”


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