title: Formulation of a mmaA4 gene deletion mutant of Mycobacterium bovis BCG in cationic liposomes significantly enhances protection against tuberculosis.
abstract: A new vaccination strategy is urgently needed for improved control of the global tuberculosis (TB) epidemic. Using a mouse aerosol Mycobacterium tuberculosis challenge model, we investigated the protective efficacy of a mmaA4 gene deletion mutant of Mycobacterium bovis BCG (ΔmmaA4BCG) formulated in dimethyl dioctadecyl ammonium bromide (DDA) - D(+) trehalose 6,6 dibenenate (TDB) (DDA/TDB) adjuvant. In previous studies, deletion of the mmaA4 gene was shown to reduce the suppression of IL-12 production often seen after mycobacterial infections. While the non-adjuvanted ΔmmaA4BCG strain did not protect mice substantially better than conventional BCG against a tuberculous challenge in four protection experiments, the protective responses induced by the ΔmmaA4BCG vaccine formulated in DDA/TDB adjuvant was consistently increased relative to nonadjuvanted BCG controls. Furthermore, the ΔmmaA4BCG-DDA/TDB vaccine induced significantly higher frequencies of multifunctional (MFT) CD4 T cells expressing both IFNγ and TNFα (double positive) or IFNγ, TNFα and IL-2 (triple positive) than CD4 T cells derived from mice vaccinated with BCG. These MFT cells were characterized by having higher IFNγ and TNFα median fluorescence intensity (MFI) values than monofunctional CD4 T cells. Interestingly, both BCG/adjuvant and ΔmmaA4BCG/adjuvant formulations induced significantly higher frequencies of CD4 T cells expressing TNFα and IL-2 than nonadjuvanted BCG or ΔmmaA4BCG vaccines indicating that BCG/adjuvant mixtures may be more effective at inducing central memory T cells. Importantly, when either conventional BCG or the mutant were formulated in adjuvant and administered to SCID mice or immunocompromised mice depleted of IFNγ, significantly lower vaccine-derived mycobacterial CFU were detected relative to immunodeficient mice injected with non-adjuvanted BCG. Overall, these data suggest that immunization with the ΔmmaA4BCG/adjuvant formulation may be an effective, safe, and relatively inexpensive alternative to vaccination with conventional BCG.
authors.affiliation: Center for Biologics Evaluation and Research, United States Food and Drug Administration, Bethesda, Maryland, United States of America. steven.derrick@fda.hhs.gov
authors.forename: Steven C
authors.initials: SC
authors.lastname: Derrick
authors.forename: Dee
authors.initials: D
authors.lastname: Dao
authors.forename: Amy
authors.initials: A
authors.lastname: Yang
authors.forename: Kris
authors.initials: K
authors.lastname: Kolibab
authors.forename: William R
authors.initials: WR
authors.lastname: Jacobs
authors.forename: Sheldon L
authors.initials: SL
authors.lastname: Morris
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D005260:Female; D017353:Gene Deletion; D051379:Mice; D016513:Mice, SCID; D006899:Mixed Function Oxygenases; D009163:Mycobacterium bovis / Q000201:enzymology / Q000235:genetics / Q000276:immunology*; D014376:Tuberculosis / Q000235:genetics / Q000276:immunology / Q000517:prevention & control*; D032581:Tuberculosis Vaccines / Q000235:genetics / Q000276:immunology*; D014611:Vaccination; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D016207:Cytokines; D032581:Tuberculosis Vaccines; D014613:Vaccines, Attenuated; D006899:Mixed Function Oxygenases