Specific treatment of autoimmunity with recombinant invariant chains in which CLIP is replaced by self-epitopes

Abstract

The invariant chain (Ii) binds to newly synthesized MHC class II molecules with the CLIP region of Ii occupying the peptide-binding groove. Here we demonstrate that recombinant Ii proteins with the CLIP region replaced by antigenic self-epitopes are highly efficient in activating and silencing specific T cells in vitro and in vivo. The Ii proteins require endogenous processing by antigenpresenting cells for efficient T cell activation. An Ii protein encompassing the epitope myelin basic protein amino acids 84 -96 (Ii-MBP84 -96) induced the model autoimmune disease experimental allergic encephalomyelitis (EAE) with a higher severity and earlier onset than the peptide. When applied in a tolerogenic manner, Ii-MBP84 -96 abolished antigen-specific T cell proliferation and suppressed peptide-induced EAE more effectively than peptide alone. Importantly, i.v. administration of Ii proteins after EAE induction completely abrogated the disease, whereas peptides only marginally suppressed disease symptoms. Ii fusion proteins are thus more efficient than peptide in modulating CD4 ؉ T cellmediated autoimmunity, documenting their superior qualities for therapeutic antigen delivery in vivo. C D4 ϩ T cells recognize peptides presented in association withMHC class II molecules on the surface of antigen-presenting cells. Peptide loading of MHC class II molecules is regulated by the chaperone molecule invariant chain (Ii). Trimers of Ii form nonameric complexes with newly synthesized MHC class II ␣␤-heterodimers within the endoplasmic reticulum. In these complexes, the CLIP core region (amino acids 90-98 in mice) of Ii occupies the peptide-binding groove of the class II molecule irrespective of the MHC haplotype (1, 2). In addition, sequences on both sides of the CLIP core region bind to the class II molecule (3-5).Genetically modified Ii proteins, in which the CLIP core region has been replaced by a T helper epitope, can be processed and presented in vitro to T cell clones by HLA DR-expressing cell lines (6, 7). Here we show that such genetically modified Ii proteins are superior to the peptide epitopes in triggering polyclonal, antigen-specific T cell populations in vitro and in vivo and, most importantly, in modulating autoimmunity in vivo. Our model system uses the peptides MBP84-96 and PLP139-151, immunodominant epitopes of the self-antigens myelin basic protein (MBP) and myelin proteolipid protein (PLP). MBP84-96 and PLP139-151 induce experimental allergic encephalomyelitis (EAE), a CD4 ϩ T cell-mediated experimental autoimmune disease, in immunized SJL mice (8, 9). We show that Ii proteins, wherein the CLIP core region has been replaced by MBP84-96 or PLP139-151, are more potent than the peptides in activating specific T cells in vitro and in vivo. Ii-MBP84-96, but not the peptide, required endogenous antigen processing by antigen-presenting cells to stimulate MBP84-96-specific T cells. Lower amounts of the Ii proteins were sufficient to break self-tolerance and induce autoimmunity in mice. On the other hand, i.p. injection...

Analysis of Autoreactive CD4 T Cells in Experimental Autoimmune Encephalomyelitis after Primary and Secondary Challenge Using MHC Class II Tetramers

“…injections of Ags in IFA or exposure to pertussis toxin or proteins from M. tuberculosis protect mice from EAE (36,37). In the present study, mice were primed by s.c. immunization with peptide Ags emulsified in CFA, a regimen that induces strong Th1-type immune responses (24).…”

“…EAE was induced essentially as described (24), with the following modifications. A total of 50 nmol of the peptide PLP139 -151 in PBS emulsified with an equal amount of CFA containing 200 g of M. tuberculosis H37RA (Difco) was injected s.c. on the back of the foot.…”

T Cell Immunity in Connective Tissue Disease Patients Targets the RNA Binding Domain of the U1-70kDa Small Nuclear Ribonucleoprotein

“…The uptake of RNA-complexed modified Ag as dead cell fragments in the periphery (such as in the case of apoptotically or granzyme B-exposed cells) may also contribute to differential central vs peripheral tolerance induction. Finally, the proposed target of the RBD could be due to effects entirely unrelated to the binding of the RNA itself; for example, the RBD could have promiscuous binding to MHC class II molecules, similar to that described for superantigen or the HLA class II-associated invariant chain-derived peptide (40,41).…”

A Structurally Available Encephalitogenic Epitope of Myelin Oligodendrocyte Glycoprotein Specifically Induces a Diversified Pathogenic Autoimmune Response

“…Immunizations and EAE induction were performed essentially as described (12), with the following modifications. For immunizations, the indicated amount of peptide Ag in PBS was mixed with an equal amount of CFA containing 4 mg/ml Mycobacterium tuberculosis H37RA (Difco/BD, Alphen aan den Rijn, The Netherlands).…”