CASE BASED REVIEW OF MEDICAL MICROBIOLOGY
Bordetella pertussis
Dr Tadayo Hashimoto M.D.
Professor
Department of Microbiology & Immunology
What is pertussis toxin (PT)? What is its mode of action?
- Produced by B. pertussis only when the organism is exposed to elevated temperatures (body temperature)
- Pertussis toxin (PT) is an A-B type exotoxin, consisting of 1 molecule of subunit A and 5 molecules of subunit B.
- Affects different functions in different cells. The toxin is also known as histamine-sensitizing factor, lymphocytosis-promoting factor, and islet-activating protein.
- Subunit B (S-2 and S3) of PT mediates attachment of the toxin to target cells which include ciliated cells and phagocytes.
- Subunit A (S1), once enters the susceptible cell, mediates enzymatic ADP-ribosylation of a particular class of G protein called inhibitory G protein (Gi) which regulates the inactivation of adenyl cyclase. The ADP-ribosylated Gi protein (ADPR-Gi) can no longer regulate the host cell=s ability to inactivate adenyl cyclase activity. The net result is an uncontrolled elevation of intracellular c-AMP level of affected host cells.
- In phagocytes, it reduces intracellular killing activities.
- PT increases histamine sensitivity
- Promotes lymphocytosis by hindering lymphocyte migration from small vessels
- Insulin production in response to glucose is increased
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