A simple assay to quantify mycobacterial lipid antigen-specific T cell receptors in human tissues and blood

• Published in: PLoS neglected tropical diseases Vol. 15; no. 12; p. e0010018
• Main Authors: Zhou, Angela X., Scriba, Thomas J., Day, Cheryl L., Hagge, Deanna A., Seshadri, Chetan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.12.2021; Public Library of Science (PLoS)
• Subjects: Antigen receptors, T cell; Antigens; Antigens, CD1 - genetics; Antigens, CD1 - immunology; Assaying; Biology and Life Sciences; Biopsy; Blood; Blood lipids; Cell lines; Cell Wall - genetics; Cell Wall - immunology; Cell walls; Cells; Cloning; Cohort Studies; Cohorts; Consent; Diagnosis; Disease; Feasibility; Feasibility studies; Health aspects; Human tissues; Humans; Infections; Laboratories; Leprosy; Leprosy - blood; Leprosy - diagnosis; Leprosy - immunology; Leprosy - microbiology; Lipids; Lipids - immunology; Lymphocytes; Lymphocytes T; Major histocompatibility complex; Measurement; Medicine and Health Sciences; Methods; Molecular diagnostic techniques; Molecular Diagnostic Techniques - methods; Molecules; Mycobacterial infections; Mycobacterium - genetics; Mycobacterium - immunology; Mycobacterium - isolation & purification; Nepal; Normalizing; Nucleotide sequence; Nucleotides; PCR; Peptides; Plasmids; Polymerase Chain Reaction; Receptors; Receptors, Antigen, T-Cell, alpha-beta - blood; Receptors, Antigen, T-Cell, alpha-beta - genetics; Receptors, Antigen, T-Cell, alpha-beta - immunology; Severe acute respiratory syndrome coronavirus 2; Skin; South Africa; T cell receptors; T cells; T-cell receptor; T-Lymphocytes - immunology; T-Lymphocytes - microbiology; Teenagers; Tissue; Tissues; Tropical diseases; Tuberculin; Tuberculosis; Tuberculosis - blood; Tuberculosis - diagnosis; Tuberculosis - immunology; Tuberculosis - microbiology; South Africa; Nepal; Germany
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0010018

T cell receptors (TCRs) encode the history of antigenic challenge within an individual and have the potential to serve as molecular markers of infection. In addition to peptide antigens bound to highly polymorphic MHC molecules, T cells have also evolved to recognize bacterial lipids when bound to non-polymorphic CD1 molecules. One such subset, germline-encoded, mycolyl lipid-reactive (GEM) T cells, recognizes mycobacterial cell wall lipids and expresses a conserved TCR-ɑ chain that is shared among genetically unrelated individuals. We developed a quantitative PCR assay to determine expression of the GEM TCR-ɑ nucleotide sequence in human tissues and blood. This assay was validated on plasmids and T cell lines. We tested blood samples from South African subjects with or without tuberculin reactivity or with active tuberculosis disease. We were able to detect GEM TCR-ɑ above the limit of detection in 92% of donors but found no difference in GEM TCR-ɑ expression among the three groups after normalizing for total TCR-ɑ expression. In a cohort of leprosy patients from Nepal, we successfully detected GEM TCR-ɑ in 100% of skin biopsies with histologically confirmed tuberculoid and lepromatous leprosy. Thus, GEM T cells constitute part of the T cell repertoire in the skin. However, GEM TCR-ɑ expression was not different between leprosy patients and control subjects after normalization. Further, these results reveal the feasibility of developing a simple, field deployable molecular diagnostic based on mycobacterial lipid antigen-specific TCR sequences that are readily detectable in human tissues and blood independent of genetic background.