title: Induction of Unconventional T Cells by a Mutant Mycobacterium bovis BCG Strain Formulated in Cationic Liposomes Correlates with Protection against Mycobacterium tuberculosis Infections of Immunocompromised Mice.
abstract: Earlier studies aimed at defining protective immunity induced by Mycobacterium bovis BCG immunization have largely focused on the induction of antituberculosis CD4(+) and CD8(+) T cell responses. Here we describe a vaccine consisting of a BCGΔmmaA4 deletion mutant formulated in dimethyl dioctadecyl-ammonium bromide (DDA) with d-(+)-trehalose 6,6'-dibehenate (TDB) (DDA/TDB) adjuvant (A4/Adj) that protected TCRδ(-/-) mice depleted of CD4(+), CD8(+), and NK1.1(+) T cells against an aerosol challenge with M. tuberculosis These mice were significantly protected relative to mice immunized with a nonadjuvanted BCGΔmmaA4 (BCG-A4) mutant and nonvaccinated controls at 2 months and 9 months postvaccination. In the absence of all T cells following treatment with anti-Thy1.2 antibody, the immunized mice lost the ability to control the infection. These results indicate that an unconventional T cell population was mediating protection in the absence of CD4(+), CD8(+), NK1.1(+), and TCRγδ T cells and could exhibit memory. Focusing on CD4(-) CD8(-) double-negative (DN) T cells, we found that these cells accumulated in the lungs postchallenge significantly more in A4/Adj-immunized mice and induced significantly greater frequencies of pulmonary gamma interferon (IFN-γ)-producing cells than were seen in the nonvaccinated or nonadjuvanted BCG control groups. Moreover, pulmonary DN T cells from the A4/Adj group exhibited significantly higher IFN-γ integrated median fluorescence intensity (iMFI) values than were seen in the control groups. We also showed that enriched DN T cells from mice immunized with A4/Adj could control mycobacterial growth in vitro significantly better than naive whole-spleen cells. These results suggest that formulating BCG in DDA/TDB adjuvant confers superior protection in immunocompromised mice and likely involves the induction of long-lived memory DN T cells.
authors.affiliation: Center for Biologics Evaluation and Research, United States Food and Drug Administration, Silver Spring, Maryland, USA steven.derrick@fda.hhs.gov.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Derrick
authors.affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Idalia
authors.initials: I
authors.lastname: Yabe
authors.affiliation: Center for Biologics Evaluation and Research, United States Food and Drug Administration, Silver Spring, Maryland, USA.
authors.forename: Sheldon
authors.initials: S
authors.lastname: Morris
authors.affiliation: Center for Biologics Evaluation and Research, United States Food and Drug Administration, Silver Spring, Maryland, USA.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Cowley
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D001500:BCG Vaccine / Q000276:immunology*; D015169:Colony Count, Microbial; D016867:Immunocompromised Host; D016130:Immunophenotyping; D008081:Liposomes / Q000008:administration & dosage*; D008168:Lung / Q000382:microbiology / Q000473:pathology; D008810:Mice, Inbred C57BL; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D014397:Tuberculosis, Pulmonary / Q000517:prevention & control*
chemical_list: D000276:Adjuvants, Immunologic; D001500:BCG Vaccine; D008081:Liposomes