Controlling immune response and demyelination using highly potent bifunctional peptide inhibitors in the suppression of experimental autoimmune encephalomyelitis

In this study, we investigated the efficacy of new bifunctional peptide inhibitors (BPIs) in suppressing experimental autoimmune encephalomyelitis (EAE) in an animal model. BPI [e.g. proteolipid proteincyclo(1,8)-CPRGGSVC-NH2 (PLP-cIBR)] is a conjugate between the PLP139151 peptide derived from proteolipid protein (PLP) and the cIBR7 peptide derived from domain-1 (D1) of intercellular adhesion molecule-1 (ICAM-1). PLPcIBR is designed to bind to major histocompatibility complex (MHC)-II and leucocyte function-associated antigen-1 (LFA-1) simultaneously to inhibit the formation of the immunological synapse and alter the differentiation and activation of a subpopulation of T cells, thus inducing immunotolerance. The results show that PLPcIBR is highly potent in ameliorating EAE, even at low concentrations and less frequent injections. Mice treated with PLPcIBR had a higher secretion of cytokines related to regulatory and/or suppressor cells compared to phosphate-buffered saline (PBS)-treated mice. In contrast, T helper type 1 (Th1) cytokines were higher in mice treated with PBS compared to PLPcIBR, suggesting that it suppressed Th1 proliferation. Also, we observed significantly less demyelination in PLP-cIBR-treated mice compared to the control, further indicating that PLPcIBR promoted protection against demyelination.