Single cell methods allow phenotypic and clonotypic analysis of Treponema pallidum-specific CD4 T cells 4723

Abstract Description Syphilis is a major public health threat, but we have limited understanding of what constitutes protective immune responses in humans. Treponema pallidum (Tp)-specific CD4 T cell responses are likely important to heal syphilis lesions and are detectable and persistent in blood and in the skin rash of secondary syphilis. We sought to define the Tp-specific CD4 T cell phenotypes that may contribute to Tp clearance. After stimulating PBMC with Tp sonicate, individual Activation Induced Marker positive CD4 T cells were isolated and expanded as candidate Tp-specific T cell clones (TCC). From these TCC we obtained confirmation of pathogen specificity, paired TCRα/β sequences, and multiplexed cytokine analysis (IFNγ, IL10, IL13, IL17A, IL21, and IL5). We detected CD4 T cell responses to Tp from PBMC of participants with recently treated secondary syphilis, active early latent syphilis and remotely treated early latent syphilis. Initial TCR analysis from 53 of 136 Tp-reactive CD4 TCC revealed clusters of sequence-related TCRs suggesting an immunodominance hierarchy of clonotypes within individuals. We were further able to identify peptide epitopes for three TCC with unique TCR sequences. Functionally, most TCC were TH1-like with few examples of TH2, Treg, Tfh and rare TH17 phenotypes. We have defined Tp-specific CD4 phenotypes, refining our current understanding of CD4 T cell function during and after Tp infection, to inform vaccine design. Funding Sources Supported by NIH T32 AI07140, U19 AI144133, UM1 AI148684, K08 AI180375 Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)