Graduate Student University of Maryland- College Park Hyattsville, Maryland, United States
Disclosure(s):
Christopher Bridgeman, MS: No financial relationships to disclose
Introduction/Rationale: Multiple sclerosis (MS) occurs when immune cells attack myelin, causing neurodegeneration. Current therapies cannot selectively target myelin-reactive cells. An emerging strategy is to engineer myelin-specific regulatory T cells (TREGs) for selective vaccine-like tolerance. Here, we co-deliver myelin peptide (MOG) with rapamycin (rapa) in polymer microparticles (M/R-MPs) directly to lymph nodes (LN) via intra-LN injection (iLN). We have shown these tissue-retained depots expand MOG-specific TREG and reverse paralysis in a preclinical MS model (EAE). However, how these cues synergize to program long-lasting, highly suppressive TREG remains unknown.
Methods: Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaged potassiated rapamycin (952 m/z) in LN cryo-sections 0.1 and 48 hours after iLN treatment. MOG TCR specific CD4+ T cells were transferred into iLN-treated mice to test if M/R-MPs promote markers linked to long-lasting T cell responses. Transferred cells from treated LNs were analyzed at 7 days for TREG, early persistence markers including memory cytokine signaling (CD127), and central memory phenotype (CD44, CD62L). Finally, TREG from treated LNs were tested in a suppression assay for their ability to restrain MOG-specific effector T cells (Teff).
Results: MALDI imaging of rapa revealed that MPs increased the duration and distribution of conditioned LN T cells. M/R co-encapsulation was required for expansion of MOG-specific TREG. These TREG exhibited increased central-memory phenotypes (CD44⁺CD62L⁺) and elevated CD127 expression, consistent with enhanced persistence. TREG isolated from M/R-MP treated LNs significantly suppressed MOG-Teff thus demonstrating the importance of synergistic delivery of peptide and rapa.
Conclusion: M/R-MPs regulate the duration and combination of immunomodulatory cues to condition suppressive antigen-specific TREG. These findings define mechanisms for engineering long-lasting potent TREG in the pursuit of disease-specific therapies for MS.
