POLYADHESINS: AN ARMORY OF GRAM--NEGATIVE PATHOGENS FOR PENETRATION THROUGH THE IMMUNE SHIELD

The rapid emergence of treatment-resistant bacterial pathogens has become a major threat to public health. The outbreak of new Shiga-toxin?producing Escherichia coli O104H4 infection occured in Germany in 2011 illustrates this problem. To colonize host tissues, pathogenic bacteria express surface adhesive organelles. The German strain uses aggregative adherence fimbriae I (AAF/I) to anchor to the intestinal mucosa and induce inflammation. AAF/I belong to the family of chaperone/usher assembled fimbrial polyadhesins. Polyadhesins are functioning as an armory for penetration through the host immune shield. The polyadhesin-binding to the target cells triggers subversive signal by aggregation of host cell receptors that allow pathogens to mislead and evade immune defense. Their binding is orchestrated with the type III secretion system, which is extremally important for bacterial virulency. Polyadhesins also are involved in biofilm formation making bacteria more resistant to immune response. Because of this, the polyadhesins are potential targets for immune countermeasures against bacterial infections, in particular for anti-adhesion therapy with antibodies to polyadhesins as one of alternatives to antibiotic therapy.