Therapeutic potential of affinity enhanced pMHCII-4E reagents

Project Summary (Abstract): This project will employ a recent innovation that we made in peptide:MHCII (pMHCII) tetramer design. Fluorescently labeled pMHCII tetramers have been used to detect CD4+ T cells of known specificity, aiding the study of these populations. However, pMHCII tetramers do not detect CD4+ T cells with TCRs at the low end of the biologically relevant affinity spectrum. The affinity of CD4 for MHCII is below the limit of detection. We used directed evolution to strengthen the interaction between MHCII and CD4, thereby stabilizing TCR-pMHCII interactions while still retaining the cognate specificity. pMHCII tetramers engineered for enhanced CD4 binding outperformed conventional tetramers in detecting cognate T cells, including the ones with low affinity TCRs. The overall goal of this project is to exploit this enhanced binding by high affinity 4E reagents in immunotherapies. The premise underlying this project is that recruitment of all antigen-specific CD4 T cells including the ones with low affinity TCRs will improve responses generated by vaccines, whereas deletion of these T cells could treat autoimmunity. The goal here is to use the high affinity 4E reagents to activate or inactivate T cells based on the clinical need. In Aim 1 we will assess the efficacy of pMHCII-4E reagents to specifically deplete auto-reactive CD4 T cells in a murine model of multiple sclerosis, Experimental Autoimmune Encephalomyelitis (EAE). Both in-vitro and in-vivo depletion followed by EAE induction will be attempted. In Aim 2 we will assess the efficacy of pMHCII-4E reagents to induce better immune responses and aid in bacterial clearance in acute or chronic / persistent bacterial infections.