Bacterial Toxins as Novel Antigen Delivery Sysems

With the elucidation of the properties and modes of action of a wide range of bacterial protein toxins has come the realisation that with appropriate adaptation, these molecules can be used to deliver other moieties to the immune system and thereby enhance immunogenicity, Given the diversity of bacterial toxins as a group of proteins, this objective can be contemplated from several perspectives, Many toxins possess the ability to bind to receptors at the surface of mammalian cells. Depending upon the fate of the toxin-receptor complex, this may provide a route for enhancing the uptake of antigen into endocytic pathways which ultimately result in presentation to the immune system, The ability of staphylococcal enterotoxins to interact with MHC class II may allow targeting of attached sequences specifically to those cells capable of processing and presenting antigen, As it becomes clearer which vesicular trafficking pathways are followed by those bacterial toxins which are taken up by cells, it may be possible to manipulate events such that attached materials are released specifically in those cellular compartments where antigen processing and/or the loading of MHC class II molecules with peptides occurs with greatest efficiency. Since several toxins have the ability to translocate from acidic endosomal or lysosomal compartments to the cell cytoplasm, this or the ability to traffic to the endoplasmic reticulum, may offer a mechanism with which to stimulate MHC class I-restricted responses against defined moieties borne by the toxin.