GM-CSF-neuroantigen fusion proteins inhibit experimental autoimmune encephalomyelitis upon injection into lymphatics primed by encephalitogenic peptide and complete Freund’s adjuvant. (THER3P.878)

Single-chain fusion proteins comprised of GM-CSF and a myelin neuroantigen (NAg) epitope are potent, NAg-specific inhibitors of rat and mouse models of experimental autoimmune encephalomyelitis (EAE). This study provided evidence that GMCSF-MOG (myelin oligodendrocyte glycoprotein 35-55 peptide) inhibited EAE when co-injected adjacent to the encephalitogenic MOG35-55/ complete Freund’s adjuvant (CFA) emulsion. Furthermore, GMCSF-MOG had tolerogenic activity in the C57BL/6 model of chronic EAE when directly incorporated with MOG35-55 in the CFA emulsion. Likewise, GMCSF-PLP (proteolipid protein 139-151 peptide) inhibited relapsing-remitting EAE in SJL mice when mixed with PLP139-151 in the CFA emulsion. In vitro studies revealed that GMCSF-MOG stimulated the growth and differentiation of inflammatory dendritic cells (DC) and targeted the MOG35-55 domain for potentiated antigen presentation. However, presentation of MOG35-55 by these inflammatory DC was inhibitory, and the inhibitory mechanism in part depended upon the elaboration of nitric oxide. In conclusion, GMCSF-NAg was tolerogenic in CFA-primed lymphatics by a mechanism associated with inflammatory DC, targeted NAg presentation, and nitric oxide production. The inhibitory activity of GMCSF-NAg in CFA-primed lymphatics distinguished GMCSF-NAg fusion proteins as inflammation-dependent tolerogens mechanistically distinct from peptide or protein-based tolerogens.