Gram Negative Coccobacilli
Acellular pertusis vaccine contains (AIIMS Nov 2011)
|A||Pertactin, fimbrial hemagglutinin, cytotoxin, endotoxin|
|B||Pertactin, fimbrial hemagglutinin, fimbriae, pertussis toxin|
|C||Pertactin, cytotoxin, fimbriae, pertactin|
|D||Cytotoxin, fimbrial hemagglutinin, pertussis toxin|
Ananthanarayan and Paniker’s
a. B.pertussis produces a number of biologically active substances that are postulated to play a role in disease. These include surface components such as filamentous haemagglutinin (FHA), pertactin and fimbriae; toxins such as pertussis toxin (PT), adenylate cyclase toxin (ACT), tracheal cytotoxin(TCT) and dermonecrotoxin (DNT).
b. Roles for these factors can be considered in the context of a generic sequence of events for an infectious disease: entry and attachment to a specific target tissue, production of local damage, and development of systemic disease.
c. FHA, pertactin, surface agglutinogens on fimbriae and possibly PT participate in attachment of B.pertussis to the respiratory epithelium. Ciliostasis and damage to the epithelium by TCT and DNT disturb mucociliary clearance, the first line of defense.
d. The inhibition of function of phagocytes by ACT and PT represent an acute but reversible disruption of the protection conferred by immune effector cells.
e. Specific immunization with killed B.pertussis has been found very effective, usually administered as an alum adsorbed vaccine combined with diphtheria and tetanus toxoid. A major limitation to whole-cell vaccine has been the associated reactogenicity.
f. When compared with DT and TT, DPT vaccines produce significantly more local and systemic reactions such as pain, swelling, fever, anorexia, vomiting, convulsions, hypotonic-hyporesponsive episodes and encephalopathy with permanent neurological sequelae. These adverse effects are more often when given to older children and hence routine pertussis vaccination is not advisable in chidren over the age of 7 yrs.
g. Acellular pertussis vaccine containing two or more protective components (FHA, PT, pertactin, Fimbiael agglutinins) are now used in several countries as they cause fewer reactions especially when give to older children.