Ribosomes as carriers for antigenic determinants of the surface of micro-organisms.

Over the past twenty-five years, many authors have reported evidence of the immunoprotective capacity of ribosomes isolated from bacteria, fungi and parasites. Since 1971 we have explored the protective capacity of ribosomes isolated from a large variety of micro-organisms responsible for human and animal diseases. Accurate biochemical characterization of ribosomes always reveals trace amounts of non-ribosomal components such as short polysaccharides strongly linked to ribosomal RNA after phenol extraction even under denaturing conditions. rRNA-antigen complexes have been purified from Klebsiella pneumoniae ribosomes inducing high level of protection against homologous experimental infection in mice. Monoclonal antibodies raised against ribosomes and then selected for their ability to confer passive immunity to mice have been used to study the mechanism of the protection induced by ribosomes and to characterize their "immunogenic principle". These investigations have clearly shown the presence on ribosomes of epitopes corresponding to antigens normally exposed on the membrane of the bacteria. In the original concept of "ribosomal immunotherapy" that we have developed, ribosomes can be considered as natural carriers for cell surface epitopes, presenting them to the immune system in a highly immunogenic configuration.