IgA antibodies and mucosal immune protection

Secretory IgA (S-IgA) antibodies are well adapted to provide specific immune protection at musosal surfaces. Activities include neutralization of biochemically active macromolecules and viruses, inhibition of adherence and uptake of microbes and environmental antigens, and they possess anti- inflammatory properties that are important in the maintenance of the integrity of the mucosal barrier. The generation of S-IgA antibodies in secretions is most effectively accomplished by stimulating the common mucosal immune system, through the specialized inductive sites of the intestinal and respiratory tracts. Novel strategies for enhancing the efficiency of this process include the use of delivery systems based on cholera toxin (CT) B subunit. Bacterial protein antigens, such as the surface adhesin AgI/II of Streptococcus mutans, have been genetically coupled to the A2 subunit od CT and coexpressed with CTB to form chimeric immunogens which induce longlasting mucosal IgA and serum IgG antibodies after intragastric or intranasal administration. The chimeric protein-CTA2/B can also be expressed in avirulent strains of Salmonella to serve as a live carrier. In addition, CTB can serve as an adjuvant for intranasal administration of bacterial protein immunogens that can induce protective immunity against nasopharyngeal colonization with Streptococcus pneumoniae.