title: The Ag85B protein of the BCG vaccine facilitates macrophage uptake but is dispensable for protection against aerosol Mycobacterium tuberculosis infection.
abstract: Defining the function and protective capacity of mycobacterial antigens is crucial for progression of tuberculosis (TB) vaccine candidates to clinical trials. The Ag85B protein is expressed by all pathogenic mycobacteria and is a component of multiple TB vaccines under evaluation in humans. In this report we examined the role of the BCG Ag85B protein in host cell interaction and vaccine-induced protection against virulent Mycobacterium tuberculosis infection. Ag85B was required for macrophage infection in vitro, as BCG deficient in Ag85B expression (BCG:(Δ85B)) was less able to infect RAW 264.7 macrophages compared to parental BCG, while an Ag85B-overexpressing BCG strain (BCG:(oex85B)) demonstrated improved uptake. A similar pattern was observed in vivo after intradermal delivery to mice, with significantly less BCG:(Δ85B) present in CD64(hi)CD11b(hi) macrophages compared to BCG or BCG:(oex85B). After vaccination of mice with BCG:(Δ85B) or parental BCG and subsequent aerosol M. tuberculosis challenge, similar numbers of activated CD4(+) and CD8(+) T cells were detected in the lungs of infected mice for both groups, suggesting the reduced macrophage uptake observed by BCG:(Δ85B) did not alter host immunity. Further, vaccination with both BCG:(Δ85B) and parental BCG resulted in a comparable reduction in pulmonary M. tuberculosis load. These data reveal an unappreciated role for Ag85B in the interaction of mycobacteria with host cells and indicates that single protective antigens are dispensable for protective immunity induced by BCG.
authors.affiliation: Microbial Pathogenesis and Immunity Group, Discipline of Infectious Diseases and Immunology, University of Sydney, Sydney, NSW, Australia; Mycobacterial Research Group, Centenary Institute of Cancer Medicine and Cell Biology, Sydney, NSW, Australia.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Prendergast
authors.affiliation: Microbial Pathogenesis and Immunity Group, Discipline of Infectious Diseases and Immunology, University of Sydney, Sydney, NSW, Australia; Mycobacterial Research Group, Centenary Institute of Cancer Medicine and Cell Biology, Sydney, NSW, Australia.
authors.forename: Claudio
authors.initials: C
authors.lastname: Counoupas
authors.affiliation: Microbial Pathogenesis and Immunity Group, Discipline of Infectious Diseases and Immunology, University of Sydney, Sydney, NSW, Australia; Mycobacterial Research Group, Centenary Institute of Cancer Medicine and Cell Biology, Sydney, NSW, Australia.
authors.forename: Lisa
authors.initials: L
authors.lastname: Leotta
authors.affiliation: Microbial Pathogenesis and Immunity Group, Discipline of Infectious Diseases and Immunology, University of Sydney, Sydney, NSW, Australia.
authors.forename: Carolina
authors.initials: C
authors.lastname: Eto
authors.affiliation: Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Wilbert
authors.initials: W
authors.lastname: Bitter
authors.affiliation: INRA, Université de Tours, UMR 1282, Infectiologie et Santé Publique, 37380 Nouzilly, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Winter
authors.affiliation: Microbial Pathogenesis and Immunity Group, Discipline of Infectious Diseases and Immunology, University of Sydney, Sydney, NSW, Australia; Mycobacterial Research Group, Centenary Institute of Cancer Medicine and Cell Biology, Sydney, NSW, Australia. Electronic address: Jamie.triccas@sydney.edu.au.
authors.forename: James A
authors.initials: JA
authors.lastname: Triccas
mesh_terms: D000217:Acyltransferases / Q000276:immunology*; D019264:Adoptive Transfer; D000336:Aerosols; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001500:BCG Vaccine / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology*; D005260:Female; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009169:Mycobacterium tuberculosis; D000067996:RAW 264.7 Cells; D014376:Tuberculosis / Q000517:prevention & control*
chemical_list: D000336:Aerosols; D000942:Antigens, Bacterial; D001500:BCG Vaccine; D001426:Bacterial Proteins; D000217:Acyltransferases; C121433:antigen 85B, Mycobacterium tuberculosis
keywords: Ag85B; BCG; Macrophages; Tuberculosis; Vaccine