ESAT-6 and HspX improve the effectiveness of BCG to induce human dendritic cells-dependent Th1 and NK cells activation

• Published in: PloS one 2013-10, Vol.8 (10), p.e75684-e75684
• Main Authors: Marongiu, Laura, Donini, Marta, Toffali, Lara, Zenaro, Elena, Dusi, Stefano
• Format: Article
• Language: English
• Subjects: Analysis; Antigens; Antigens, Bacterial - pharmacology; Antigens, CD - metabolism; Antigens, Differentiation, T-Lymphocyte - metabolism; Antitubercular agents; Bacillus Calmette-Guerin vaccine; Bacterial infections; Bacterial Proteins - pharmacology; BCG; BCG Vaccine - immunology; Blocking antibodies; CD4 antigen; CD4-Positive T-Lymphocytes; CD69 antigen; Cell activation; Cells, Cultured; Cytokines; Cytokines - metabolism; Dendritic cells; Dendritic Cells - drug effects; Dendritic Cells - immunology; Dendritic Cells - metabolism; Enzyme-Linked Immunosorbent Assay; ESAT-6 antigen; Flow Cytometry; Humans; Immune response (cell-mediated); Immune system; Immunogenicity; Immunoglobulins; Immunologic factors; Interferon-gamma - metabolism; Interleukin 12; Interleukin-12 - metabolism; Killer cells; Killer Cells, Natural - drug effects; Killer Cells, Natural - immunology; Killer Cells, Natural - metabolism; Lectins, C-Type - metabolism; Lymphocytes; Lymphocytes T; Maturation; Memory cells; Mycobacterium tuberculosis; Natural killer cells; Pathology; Phenotypes; Product enhancement; Proteins; T cell receptors; T cells; TLR2 protein; Toll-like receptors; Tuberculosis; Tuberculosis vaccines; Vaccination; Vaccines; γ-Interferon
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0075684

The limited efficacy of the BCG vaccine against tuberculosis is partly due to the missing expression of immunogenic proteins. We analyzed whether the addition to BCG of ESAT-6 and HspX, two Mycobacterium tuberculosis (Mtb) antigens, could enhance its capacity to activate human dendritic cells (DCs). BCG showed a weak ability to induce DC maturation, cytokine release, and CD4(+) lymphocytes and NK cells activation. The addition of ESAT-6 or HspX alone to BCG-stimulated DC did not improve these processes, whereas their simultaneous addition enhanced BCG-dependent DC maturation and cytokine release, as well as the ability of BCG-treated DCs to stimulate IFN-γ release and CD69 expression by CD4(+) lymphocytes and NK cells. Addition of TLR2-blocking antibody decreased IL-12 release by BCG-stimulated DCs incubated with ESAT-6 and HspX, as well as IFN-γ secretion by CD4(+) lymphocytes co-cultured with these cells. Moreover, HspX and ESAT-6 improved the capacity of BCG-treated DCs to induce the expression of memory phenotype marker CD45RO in naïve CD4(+) T cells. Our results indicate that ESAT-6 and HspX cooperation enables BCG-treated human DCs to induce T lymphocyte and NK cell-mediated immune responses through TLR2-dependent IL-12 secretion. Therefore ESAT-6 and HspX represent good candidates for improving the effectiveness of BCG vaccination.