title: Improving the Immunogenicity of the Mycobacterium bovis BCG Vaccine by Non-Genetic Bacterial Surface Decoration Using the Avidin-Biotin System.
abstract: Current strategies to improve the current BCG vaccine attempt to over-express genes encoding specific M. tuberculosis (Mtb) antigens and/or regulators of antigen presentation function, which indeed have the potential to reshape BCG in many ways. However, these approaches often face serious difficulties, in particular the efficiency and stability of gene expression via nucleic acid complementation and safety concerns associated with the introduction of exogenous DNA. As an alternative, we developed a novel non-genetic approach for rapid and efficient display of exogenous proteins on bacterial cell surface. The technology involves expression of proteins of interest in fusion with a mutant version of monomeric avidin that has the feature of reversible binding to biotin. Fusion proteins are then used to decorate the surface of biotinylated BCG. Surface coating of BCG with recombinant proteins was highly reproducible and stable. It also resisted to the freeze-drying shock routinely used in manufacturing conventional BCG. Modifications of BCG surface did not affect its growth in culture media neither its survival within the host cell. Macrophages phagocytized coated BCG bacteria, which efficiently delivered their surface cargo of avidin fusion proteins to MHC class I and class II antigen presentation compartments. Thereafter, chimeric proteins corresponding to a surrogate antigen derived from ovalbumin and the Mtb specific ESAT6 antigen were generated and tested for immunogenicity in vaccinated mice. We found that BCG displaying ovalbumin antigen induces an immune response with a magnitude similar to that induced by BCG genetically expressing the same surrogate antigen. We also found that BCG decorated with Mtb specific antigen ESAT6 successfully induces the expansion of specific T cell responses. This novel technology, therefore, represents a practical and effective alternative to DNA-based gene expression for upgrading the current BCG vaccine.
authors.affiliation: Division of Infectious Diseases, Department of Medicine and Vancouver Costal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Ting-Yu Angela
authors.initials: TY
authors.lastname: Liao
authors.affiliation: Division of Infectious Diseases, Department of Medicine and Vancouver Costal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Alice
authors.initials: A
authors.lastname: Lau
authors.affiliation: Division of Infectious Diseases, Department of Medicine and Vancouver Costal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Sunil
authors.initials: S
authors.lastname: Joseph
authors.affiliation: Institute of Biomedical Technology, University of Tampere, Tampere, Finland.
authors.forename: Vesa
authors.initials: V
authors.lastname: Hytönen
authors.affiliation: Division of Infectious Diseases, Department of Medicine and Vancouver Costal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Zakaria
authors.initials: Z
authors.lastname: Hmama
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology; D000954:Antigens, Surface / Q000235:genetics; D001360:Avidin / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001500:BCG Vaccine / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology; D001710:Biotin / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D005260:Female; D006183:H-2 Antigens / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009163:Mycobacterium bovis / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology; D010047:Ovalbumin / Q000235:genetics / Q000276:immunology; D010587:Phagocytosis; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D014614:Vaccines, Synthetic / Q000235:genetics / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001500:BCG Vaccine; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D006183:H-2 Antigens; D011993:Recombinant Fusion Proteins; D014614:Vaccines, Synthetic; D001360:Avidin; D001710:Biotin; D010047:Ovalbumin