Theoretical Quantification of the Polyvalent Binding of Nanoparticles Coated with Peptide-MHC to TCR-Nanoclusters

Abstract

Nanoparticles (NPs) coated with pMHCs can reprogram a specific type of CD4+ T cells into diseasesuppressing T regulatory type 1 cells by binding to their TCRs expressed as TCR-nanoclusters (TCRnc). NP size and number of pMHCs coated on them (called valence) can be adjusted to increase their efficacy. Here we explore how this polyvalent interaction is manifested and examine if it can facilitate T cell activation. This is done by developing a multiscale biophysical model that takes into account the complexity of this interaction. Using the model, we quantify pMHC insertion probabilities, dwell time of NP binding, TCRnc carrying capacity, the distribution of covered and bound TCRs by NPs, and cooperativity in the binding of pMHCs within the contact area. Model fitting and parameter sweeping further reveal that moderate jumps between IFN{gamma} dose-response curves at low valences can occur, suggesting that the geometry of NP binding can prime T cells for activation.