We evaluated the therapeutic efficacy and mechanisms of action of both mouse and human B7-H4 Immunoglobulin fusion proteins (mB7-H4Ig; hB7-H4Ig) in treating EAE. The present data show that mB7-H4Ig both directly and indirectly (via increasing Treg function) inhibited CD4⁺ T-cell proliferation and differentiation in both Th1- and Th17-cell promoting conditions while inducing production of IL-10. B7-H4Ig treatment effectively ameliorated progression of both relapsing (R-EAE) and chronic EAE correlating with decreased numbers of activated CD4⁺ T-cells within the CNS and spleen, and a concurrent increase in number and function of Tregs. The functional requirement for Treg activation in treating EAE was demonstrated by a loss of therapeutic efficacy of hB7-H4Ig in R-EAE following inactivation of Treg function either by anti-CD25 treatment or blockade of IL-10. Significant to the eventual translation of this treatment into clinical practice, hB7-H4Ig similarly inhibited the in vitro differentiation of naïve human CD4⁺ T-cells in both Th1- and Th17-promoting conditions, while promoting the production of IL-10. B7-H4Ig thus regulates pro-inflammatory T-cell responses by a unique dual mechanism of action and demonstrates significant promise as a therapeutic for autoimmune diseases, including MS.
Keywords: Autoimmunity; B7-H4; B7-H4-Immumoglobulin fusion protein; B7-H4Ig; C-EAE; CD4(+) T-cell; CFA; CNS; CTLA-4; Costimulatory/co-inhibitory molecule; EAE; MBP; MS; OVA; PLP; R-EAE; Regulatory T-cells; T cell receptor; T1D; TCR; Type I diabetes; central nervous system; chronic experimental autoimmune encephalomyelitis; complete Freund's adjuvant; cytotoxic T lymphocyte associated antigen-4; hB7-H4Ig; human B7-H4Ig; mB7-H4Ig; mouse B7-H4Ig; multiple sclerosis; myelin basic protein; myelin proteolipid protein; ovalbumin; relapsing experimental autoimmune encephalomyelitis.
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