Engineering of doubly antigenized immunoglobulins expressing T and B viral epitopes

Concomitant with the advent of molecular biology techniques and the ability of immunoglobulins (Ig) to recognize proteins, carbohydrates, lipopeptides and nucleic acids, vaccinologists have taken advantage to develop a variety of prophylactic and therapeutic vaccine prototypes. Presentation of epitopes to the immune system by Ig molecules as a carrier platform offers several advantages: (i) long exposure of the antigen to antigen processing cells (APCs) by virtue of their long half life, (ii) lack of the immune response to self Ig, focusing the immune response to protective epitopes rather than irrelevant epitopes, (iii) it takes advantage of the properties of Fc fragment of various isotypes like crossing the placenta (IgG) or homing in epithelia (IgA), and (iv) targeting various antigens by virtue of their binding specificity.

This study was aimed to genetically and enzymatically engineer immunoglobulins (Igs) able to express and to deliver concomitantly immunodominant T and B viral epitopes.

Using a genetic engineering approach we replaced the complementary determining region 3 (CDR3) and complementary determining region 2 (CDR2) of an anti-arsonate 91A3 mAb with the immunodominant HA110-120 T cell epitope and HA150-159 B cell epitope of hemagglutinin (HA) of influenza A/PR8 virus, respectively. The second doubly antigenized Ig (Ig-HA-Gal-B) was constructed on an Ig in which CDR3 was replaced with HA110-120 T cell epitope while the HA150-159 B cell epitope was enzymatically assembled through an imidic bond on the galactose (Gal) residues of the carbohydrate moiety.

Both genetically and genetically/enzymatically doubly antigenized Ig constructs (dAIg) were properly folded and they were able to activate peptide-specific T cells and to elicit anti-viral antibody response in mice. This demonstrates that the CDR loops as well as carbohydrate moieties of immunoglobulins represent permissive sites for grafting foreign epitopes without altering the structural integrity of immunoglobulins and the immunogenicity of the viral peptides.