A Subset of Protective γ9δ2 T Cells Is Activated by Novel Mycobacterial Glycolipid Components.
γ9δ2 T cells provide a natural bridge between innate and adaptive immunity, rapidly and potently respond to pathogen infection in mucosal tissues, and are prominently induced by both tuberculosis (TB) infection and bacillus Calmette Guérin (BCG) vaccination. Mycobacterium-expanded γ9δ2 T cells represent only a subset of the phosphoantigen {isopentenyl pyrophosphate [IPP] and (E)-4-hydroxy-3-methyl-but-2-enylpyrophosphate [HMBPP]}-responsive γ9δ2 T cells, expressing an oligoclonal set of T cell receptor (TCR) sequences which more efficiently recognize and inhibit intracellular Mycobacterium tuberculosis infection. Based on this premise, we have been searching for M. tuberculosis antigens specifically capable of inducing a unique subset of mycobacterium-protective γ9δ2 T cells. Our screening strategy includes the identification of M. tuberculosis fractions that expand γ9δ2 T cells with biological functions capable of inhibiting intracellular mycobacterial replication. Chemical treatments of M. tuberculosis whole-cell lysates (MtbWL) ruled out protein, nucleic acid, and nonpolar lipids as the M. tuberculosis antigens inducing protective γ9δ2 T cells. Mild acid hydrolysis, which transforms complex carbohydrate to monomeric residues, abrogated the specific activity of M. tuberculosis whole-cell lysates, suggesting that a polysaccharide was required for biological activity. Extraction of MtbWL with chloroform-methanol-water (10:10:3) resulted in a polar lipid fraction with highly enriched specific activity; this activity was further enriched by silica gel chromatography. A combination of mass spectrometry and nuclear magnetic resonance analysis of bioactive fractions indicated that 6-O-methylglucose-containing lipopolysaccharides (mGLP) are predominant components present in this active fraction. These results have important implications for the development of new immunotherapeutic approaches for prevention and treatment of TB.
Division of Infectious Diseases, Allergy & Immunology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
Mei
M
Xia
Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
Danny C
DC
Hesser
Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
Prithwiraj
P
De
Division of Infectious Diseases, Allergy & Immunology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
Isaac G
IG
Sakala
Division of Infectious Diseases, Allergy & Immunology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
Charles T
CT
Spencer
Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, Colorado, USA.
Jay S
JS
Kirkwood
Division of Infectious Diseases, Allergy & Immunology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
Getahun
G
Abate
Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
Delphi
D
Chatterjee
Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA Karen.Dobos@colostate.edu hoftdf@slu.edu.
Karen M
KM
Dobos
Division of Infectious Diseases, Allergy & Immunology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, Missouri, USA Karen.Dobos@colostate.edu hoftdf@slu.edu.
Daniel F
DF
Hoft
D056704:Adaptive Immunity / Q000276:immunology; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D006017:Glycolipids / Q000276:immunology*; D045782:Hemiterpenes / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D008757:Methylglucosides / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D009943:Organophosphorus Compounds / Q000276:immunology; D011134:Polysaccharides / Q000276:immunology; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000382:microbiology; D014376:Tuberculosis / Q000276:immunology* / Q000382:microbiology
D000942:Antigens, Bacterial; D006017:Glycolipids; D045782:Hemiterpenes; D008757:Methylglucosides; D009943:Organophosphorus Compounds; D011134:Polysaccharides; D016692:Receptors, Antigen, T-Cell, gamma-delta; C072681:Mycobacterium tuberculosis antigens; C033884:6-O-methylglucose; C004809:isopentenyl pyrophosphate