title: Exposure to Mycobacterium avium can modulate established immunity against Mycobacterium tuberculosis infection generated by Mycobacterium bovis BCG vaccination.
abstract: Mycobacterium bovis bacille Calmette Guerin (BCG), the current vaccine against infection with Mycobacterium tuberculosis, offers a variable, protective efficacy in man. It has been suggested that exposure to environmental mycobacteria can interfere with the generation of BCG-specific immunity. We hypothesized that exposure to environmental mycobacteria following BCG vaccination would interfere with established BCG immunity and reduce protective efficacy, thus modeling the guidelines for BCG vaccination within the first year of life. Mice were vaccinated with BCG and subsequently given repeated oral doses of live Mycobacterium avium to model exposure to environmental mycobacteria. The protective efficacy of BCG with and without subsequent exposure to M. avium was determined following an aerogenic challenge with M. tuberculosis. Exposure of BCG-vaccinated mice to M. avium led to a persistent increase in the number of activated T cells within the brachial lymph nodes but similar T cell activation profiles in the lungs following infection with M. tuberculosis. The capacity of BCG-vaccinated mice to reduce the bacterial load following infection with M. tuberculosis was impaired in mice that had been exposed to M. avium. Our data suggest that exposure to environmental mycobacteria can negatively impact the protection afforded by BCG. These findings are relevant for the development of a vaccine administered in regions with elevated levels of environmental mycobacteria.
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases, Center for Microbial Interface Biology, 420 West 12th Avenue, Columbus, OH 43210, USA.
authors.forename: David K
authors.initials: DK
authors.lastname: Flaherty
authors.forename: Bridget
authors.initials: B
authors.lastname: Vesosky
authors.forename: Gillian L
authors.initials: GL
authors.lastname: Beamer
authors.forename: Paul
authors.initials: P
authors.lastname: Stromberg
authors.forename: Joanne
authors.initials: J
authors.lastname: Turner
mesh_terms: D000818:Animals; D001500:BCG Vaccine / Q000276:immunology* / Q000494:pharmacology; D001980:Bronchi / Q000276:immunology / Q000382:microbiology; D005260:Female; D006801:Humans; D007223:Infant; D008198:Lymph Nodes / Q000276:immunology / Q000382:microbiology; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D009162:Mycobacterium avium / Q000276:immunology*; D009163:Mycobacterium bovis / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014397:Tuberculosis, Pulmonary / Q000276:immunology* / Q000517:prevention & control / Q000662:veterinary
chemical_list: D001500:BCG Vaccine