External Capsule Protects Gum Disease-Causing Bacteria From Immune Response

Article

The capsule of Porphyromonas gingivalis, the bacterium that causes gum disease, provides stealth, boosting the bacterium's virulence, according to a paper published in the November issue of Infection and Immunity. Call it a sugar coating, if you will, for in fact, the capsule is made from sugar molecules, which do not ordinarily elicit immunity. Thus it hides the bacterium's proteins within, preventing immune response.

In the study, the researchers, led by Janina P. Lewis of Virginia Commonwealth University, Richmond, compared the ability of normal, and mutant bacteria that were missing the capsule, to activate the immune system, to enter eukaryotic cells (the kind that are present in multicellular organisms), to cause disease, and to survive in mice. "The mutant bacteria activated the host to a greater extent, and thus, were more easily killed by eukaryotic cells," says Lewis. "Thus, the capsule protects the bacteria and allows them to survive unnoticed in our bodies."

Capsules also protect both bacteria and fungi, including P. gingivalis, as per this report, from being engulfed by the immune system's phagocytes (phago=eat; cyto=cell) and from being identified by dendritic cells as dangerous, thus marking them for destruction by antibodies. Conversely, in the study, mutant, non-encapsulated P. gingivalis were rapidly engorged by immune cells, and killed.

"Thus, anything that would interfere with generation of capsule, such as drugs interfering with the action of enzymes involved in synthesis of the sugar coat, could be used in treatment of periodontal disease, and importantly, could have broader implications for prevention of more serious diseases," by other encapsulated bacteria, such as pneumonia, anthrax, meningitis, endocarditis, and gastroenteritis, says Lewis.

Reference: A. Singh, T. Wyant, C. Anaya-Bergman, J. Aduse-Opoku, J. Brunner, M.L. Laine, M.A. Curtis, and J.P. Lewis, 2011. The capsule of Porphyromonas gingivalis leads to a reduction in the host inflammatory response, evasion of phagocytosis, and increase in virulence. Infect. Immun. 79:4533-4542.

Related Videos
NFID Medical Director, Robert H. Hopkins, Jr., MD  (Photo courtesy by Evoke Kyne)
Shelley Summerlin-Long, MPH, MSW, BSN, RN, senior quality improvement leader, infection prevention, UNC Medical Center, Chapel Hill, North Carolina
Infection Control Today Infection Intel: Staying Ahead with Company updates and product Innovations.
An eye instrument holding an intraocular lens for cataract surgery. How to clean and sterilize it appropriately?   (Adobe Stock 417326809By Mohammed)
Christopher Reid, PhD  (Photo courtesy of Christopher Reid, PhD)
Paper with words antimicrobial resistance (AMR) and glasses.   (Adobe Stock 126570978 by Vitalii Vodolazskyi)
3D illustration: Candida auris   (Adobe Stock 635576411 By Niamh )
 MIS-C (Adobe Stock 350657530 by Bernard Chantal)
Set of white bottles with cleaning liquids on the white background. (Adobe Stock 6338071172112 by zolnierek)
Related Content