A Novel Approach to Deep Profiling the T Cell Response to Tuberculosis
Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is a disease that can exist in a latent or active stage and is responsible for millions of deaths globally each year. Upon infection of Mtb in the human lungs, an adaptive immune response from CD4+ T cells is evoked. CD4+ T cells are activated when T-cell receptors (TCRs) recognize and bind to Mtb antigens, which are processed and presented on the surface of major histocompatibility complexes (MHCs). We hypothesize that a simultaneous 2-dimensional view of T cell antigen-specificity and T cell phenotype will be necessary to determine a protective immune state against Mtb that can be applied to the stage-specific profiling of TB patients and development of a more effective TB vaccine. We used 10X single cell sequencing to generate such a view. Peripheral blood mononuclear (PMBC) cells from a patient with latent Tuberculosis disease were cultured for 10 days with 24 Mtb peptides previously discovered in the lab to bind strongly to HLA type 15:03 (an allele commonly found in TB-affected populations) using PepSeq analysis. We then applied single cell sequencing to pair the cellular phenotype and TCR sequence of >1000 T cells. We found evidence of two major clonotype, sets of T cells with conserved TCR sequences, clusters that appeared to have expanded in response to the 24 peptide-MHC multimers. These clonotype clusters were determined to have adopted Th1 and Th17 phenotypes, respectively. These results suggest that both Th1 and Th17 states emerge during the immune defense against TB. Additionally, we found the method of culturing TB cells with peptide-MHC multimers and sequencing these cells with 10X is an efficient method of identifying and phenotyping TB-reactive cells, with the potential to expand to other antigens of interest
