Abstract

γ9δ2 T cells provide a natural bridge between innate and adaptive immunity and are prominently induced by both tuberculosis (TB) infection and bacillus Calmette Guérin (BCG) vaccination. Mycobacteria-expanded γ9δ2 T cells represent only a subset of the simple phosphoantigen (IPP and HMBPP)-responsive γ9δ2 T cells, this subset expresses a more oligoclonal set of TCR sequences, and only this subset efficiently recognizes and inhibits intracellular BCG/Mtb. We have been searching for new mycobacterial antigens capable of inducing the unique subset of γ9δ2 T cells that can recognize mycobacteria-infected macrophages and mediate protective effects inhibiting intracellular mycobacterial growth. We first ruled out protein, nucleic acid and apolar lipids with basic separations and enzymatic digestions. Acid hydrolysis, which digests complex carbohydrate structures, had the largest effect on eliminating Mtb fraction specific activity. Organic extractions resulted in sub-fractions with >100 fold enriched specific activity. A combination of MS, NMR, TLC indicate that methyl-glucose lipopolysaccharides (mGLP) are predominant components of the most active fractions. We are currently attempting to use synthetic techniques to confirm the specific activity of mGLP for induction of protective γ9δ2 T cells. These results have important implications for the development of new immunotherapeutic approaches for prevention/treatment of TB.

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