Deep sequencing of T-cells specific for a mycobacterial glycolipid reveals canonical T-cell receptor motifs that can be used as biomarkers in population-based studies — ASN Events
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Deep sequencing of T-cells specific for a mycobacterial glycolipid reveals canonical T-cell receptor motifs that can be used as biomarkers in population-based studies (#47)

Ryan Emerson 1 , Krystle Quan 2 , William DeWitt 1 , Anna Sherwood 1 , Thomas Scriba 3 , Harlan Robins 1 , Chetan Seshadri 2
  1. Adaptive Biotechnologies, Seattle, USA
  2. Department of Medicine, University of Washington, Seattle, USA
  3. South African Tuberculosis Vaccine Initiative, University of Cape Town, Cape Town, South Africa

The complementarity determining region 3 (CDR3) of the T-cell receptor (TCR) heavy chains determine antigen-specificity of T cells, so CDR3 sequences are potential biomarkers of antigen-specific T-cell responses.  However, the highly polymorphic nature of major histocompatibility complex genes makes it unlikely that most humans will generate antigen-specific T cells with the same CDR3 sequence.  We hypothesized that a non-polymorphic antigen-presenting molecule might provide the structural constraint required for a common CDR3 motif to be shared within a population.  To test this hypothesis, we used CD1b tetramers loaded with glucose monomycolate to isolate lipid antigen-specific T-cells from four South African adults infected with Mycobacterium tuberculosis. We used a multiplex PCR to fully characterize the CDR3 sequences from approximately 70,000 in-vitro expanded and re-sorted tetramer-positive T-cells.  We defined a motif as a set of TCR sequences with common CDR3 length, common V and J family usage, and composed of representatives from all donors.  Within the TCR-α chain, we identified a highly stereotyped 13 amino acid motif (CAVRNTGGFKTIF) consistent with the recently published TRAV1-2_TRAJ9 germline rearrangement present in mycolyl lipid-reactive (GEM) T-cells.  We also identified a stereotyped 14 amino acid motif (CASSPRLGGDEQYF) within the TCR-β chain that is the result of TRBV06_TRBJ02 rearrangement.  In the absence of in-vitro expansion, both motifs were significantly enriched (52-fold for TCR-α and 132-fold for TCR-β) in approximately 4,000 tetramer-positive T-cells sorted directly from peripheral blood mononuclear cells compared to 1.2 million tetramer-negative T-cells from these same four donors. Among 587 healthy bone marrow donors at low risk for M. tuberculosis infection, the TCR-β motif was present at a frequency similar to that of tetramer-negative samples. The relative absence of a lipid-antigen specific TCR-β motif in T-cells from healthy donors suggest that it could be used as a specific marker of mycobacterial infection in population-based studies.