Citrullination of Linear and Cyclic Altered Peptide Ligands from Myelin Basic Protein (MBP₈₇₋₉₉) Epitope Elicits a Th1 Polarized Response by T Cells Isolated from Multiple Sclerosis Patients: Implications in Triggering Disease

Abstract

Derangement of cellular immunity is central in the pathophysiology of multiple sclerosis (MS) and is often manifested by abnormal cytokine production. We investigated cytokine secretion in peripheral blood mononuclear cells (PBMC) of 18 MS patients and 15 controls and correlated cytokine polarization with the nature of antigenic stimulus. We synthesized two novel citrullinated peptides, linear [Cit(91), Ala(96), Cit(97)]MBP(87-99) and cyclo(87-99)[Cit(91), Ala(96), Cit(97)]MBP(87-99) that resulted from citrullination of 91,97 Arg residues in antagonists, linear [Arg(91), Ala(96)]MBP(87-99) and cyclo(87-99)[Arg(91), Ala(96)]MBP(87-99) peptides. PBMC from MS patients and controls were cultured with citrullinated peptides, and both peptides caused a Th1 polarization in all MS patients studied. In contrast, culture with noncitrullinated MBP peptides resulted in heterogeneous cytokine secretion that differed between individual patients. Thus, citrullination of self-antigens may potentially trigger disease in susceptible individuals. This finding may open new avenues in drug design of new substances that inhibit citrullination and arrest epitope spreading and worsening of MS.

Contribution of Myelin Autoantigen Citrullination to T Cell Autoaggression in the Central Nervous System

“…Intriguing evidence that peripheral blood T cell responses from MS patients are more robust when challenged with a citrullinated form of an immunodominant MBP peptide than the noncitrullinated form have lent some support to this view (57). Lewis rats have been reported to develop EAE after active immunization with a citrullinated form of MBP (21).…”

Remitting–relapsing multiple sclerosis patient refractory to conventional treatments and bone marrow transplantation who responded to natalizumab

“…Although a direct comparison cannot be made between patient A, who has a history of BMT, and typical RR-MS patients who are refractory to conventional treatments and are put on natalizumab, a possible explanation is that the peptide we used for the Treg functional assays is a citrullinated myelin basic protein peptide. It is becoming increasingly apparent that citrullination of self-antigens is a major mechanism in triggering autoimmune/inflammatory diseases such as MS 6,13,24. Future work with RR-MS patients treated with natalizumab, in comparison to other types of treatment, will clarify whether natalizumab treatment results in the generation of functional Tregs in RR-MS patients in general.…”

“…The cells were cultured O/N in RPMI1640 medium (GIBCO BRL, Gaithersburg, MD), containing 10% fetal bovine serum and 1% penicillin/streptomycin at a concentration of 10 6 cells/mL, in the presence or absence of peptide cP7 at a concentration 10 pg/mL/10 6 cells. Peptide cP7 (Figure 1) is a modified myelin basic protein antigenic epitope that elicits a very strong Th1 response by peripheral blood effector T cells of RR-MS patients in the acute phase of the disease before treatment or under continuous prophylactic therapy with IFN-β 13…”

Unnatural amino acids improve affinity and modulate immunogenicity: Developing peptides to treat MHC type II autoimmune disorders

“…In another study, the cyclic and linear MBP 87–99[Ala96] was citrullinated, replacing Arg 91 and Arg 97 post‐synthetically using isolated PAD enzyme (see Scheme above) . Citrullination has been implicated in other MHC type II autoimmune disorders such as RA as described above: citrullinated peptides appear to be generally highly antigenic .…”