1 Department of Medicine, Division of Rheumatology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States, 2 General Nanotherapeutics, LLC, Santa Monica, CA, United States, 3 Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States, 4 Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada, 5 Program in Infectious Diseases and Immunology in Global Health Research Institute, McGill University, Montreal, QC, Canada, 6 Department of Medicine, University of California Los Angeles, Los Angeles, CA, United States

Autoantigen-directed tolerance can be induced by certain nucleosomal histone peptide epitope/s in nanomolar dosage leading to sustained remission of disease in mice with spontaneous SLE. By contrast, lupus is accelerated by administration of intact (whole) histones, or whole nucleosomes in microparticles from apoptotic cells, or by post-translationally acetylated histone-peptides. Low-dose therapy with the histone-peptide epitopes simultaneously induces TGFβ and inhibits IL-6 production by DC in vivo , especially pDC, which then induce CD4+CD25+ Treg and CD8+ Treg cells that suppress pathogenic autoimmune response. Both types of induced Treg cells are FoxP3+ and act by producing TGFβ at close cell-to-cell range. No anaphylactic adverse reactions, or generalized immunosuppression have been detected in mice injected with the peptides, because the epitopes are derived from evolutionarily conserved histones in the chromatin; and the peptides are expressed in the thymus during ontogeny, and their native sequences have not been altered. The peptide-induced Treg cells can block severe lupus on adoptive transfer reducing inflammatory cell reaction and infiltration in the kidney. In Humans , similar potent Treg cells are generated by the histone peptide epitopes in vitro in lupus patients’ PBMC, inhibiting anti-dsDNA autoantibody and interferon production. Furthermore, the same types of Treg cells are generated in lupus patients who are in very long-term remission (2-8 years) after undergoing autologous hematopoietic stem cell transplantation. These Treg cells are not found in lupus patients treated conventionally into clinical remission (SLEDAI of 0); and consequently they still harbor pathogenic autoimmune cells, causing subclinical damage. Although antigen-specific therapy with pinpoint accuracy is suitable for straight-forward organ-specific autoimmune diseases, Systemic Lupus is much more complex. The histone peptide epitopes have unique tolerogenic properties for inhibiting Innate immune cells (DC), T cells and B cell populations that are both antigen-specifically and cross-reactively involved in the pathogenic autoimmune response in lupus. The histone peptide tolerance is a natural and non-toxic therapy suitable for treating early lupus, and also maintaining lupus patients after toxic drug therapy. The experimental steps, challenges and possible solutions for successful therapy with these peptide epitopes are discussed in this highly focused review on Systemic Lupus.

Some patients with systemic lupus erythematosus (SLE) are refractory to traditional therapies, dependent on chronic corticosteroids, have organ damage, and are at high risk of mortality. In this group of patients, we report outcome at a median of five years after autologous hematopoietic stem cell transplant (HSCT) using two different non-myeloablative regimens. Four patients received a conditioning regimen of cyclophosphamide (200 mg/kg) and alemtuzumab (60 mg), while 26 patients underwent conditioning with cyclophosphamide (200 mg/kg), rATG (Thymoglobulin) (5.5 mg/kg), and rituximab 1000 mg. Unselected peripheral blood stem cells were infused on day 0. There were no treatment related deaths. Of the four patients treated with cyclophosphamide and alemtuzumab, none entered remission. For the 26 patients treated with cyclophosphamide, rATG, and rituximab, disease remission defined as no immune suppressive drugs except hydroxychloroquine and/or 10 mg or less of prednisone a day was 92% at 6 months, 92% at one year, 81% at 2 years, 71% at 3 years, and 62% at 4 and 5 years post-HSCT. Autologous HSCT outcome is dependent on the conditioning regimen but prior organ damage may cause lingering symptoms.

We studied effects of early and late apoptotic (necroptotic) cell products, related damage associated alarmins and TLR agonists, on hematopoietic stem and progenitor cells (HSPC). Surprisingly, normal HSPC themselves produced IL-17 and IL-21 after 1½days of stimulation, and the best stimulators were TLR 7/8 agonist; HMGB1–DNA; TLR 9 agonist, and necroptotic B cells. The stimulated HSPC expressed additional cytokines/mediators, directly causing rapid expansion of IL-17+ memory CD4 T (Th17), and CD8 T (Tc17) cells, and antigen-experienced IL-17+ T cells with “naïve” phenotype. In lupus marrow, HSPC were spontaneously pre-stimulated by endogenous signals to produce IL-17 and IL-21. In contrast to HSPC, megakaryocyte progenitors (MKP) did not produce IL-17, and unlike HSPC, they could process and present particulate apoptotic autoantigens to augment autoimmune memory Th17 response. Thus abnormally stimulated primitive hematopoietic progenitors augment expansion of IL-17 producing immune and autoimmune memory T cells in the bone marrow, which may affect central tolerance.

Dendritic cells (DCs) are critical for immune homeostasis. To target DCs, we generated a mouse line with Flip deficiency in cells that express cre under the CD11c promoter (CD11c-Flip-KO). CD11c-Flip-KO mice spontaneously develop erosive, inflammatory arthritis, resembling rheumatoid arthritis, which is dramatically reduced when these mice are crossed with Rag −/ − mice. The CD8α + DC subset is significantly reduced, along with alterations in NK cells and macrophages. Autoreactive CD4 + T cells and autoantibodies specific for joint tissue are present, and arthritis severity correlates with the number of autoreactive CD4 + T cells and plasmablasts in the joint-draining lymph nodes. Reduced T regulatory cells (Tregs) inversely correlate with arthritis severity, and the transfer of Tregs ameliorates arthritis. This KO line identifies a model that will permit in depth interrogation of the pathogenesis of rheumatoid arthritis, including the role of CD8α + DCs and other cells of the immune system.

Platelets, like stromal cells, present antigen only via MHC class I, but the immune potential of their progenitors has not been explored in humans. We derived CD34(+)CD117(+)CD41(+)CD151(+) megakaryocyte progenitors (MKp) in vitro from mobilized peripheral blood hematopoietic stem and progenitor cells (HSPC) of normal subjects using culture conditions akin to bone marrow niche, or organs that support extramedullary hematopoiesis. The MKp expressed MHC Class II in contrast to platelets and functioned as professional APC before they matured further. Moreover, MKp constitutively expressed mRNA encoding mediators for human Th17 expansion, including IL-1, IL-18, IL-6, TGFβ, IL-23, BAFF, and COX2. MKp also expressed high levels of type I interferon and IRF5 mRNA. In contrast to platelets, MKp augmented the expansion of Th17, Th1, and potent Th17/Th1 double-positive cells in normal PBMC and CD4 line T cells from normal subjects or lupus patients. The Th cell augmentation involved pre-committed memory cells, and was significant although modest, because only non-cognate MKp-T cell interactions could be studied, under non-polarizing conditions. Importantly, the MKp-mediated expansion was observed in the presence or absence of direct MKp-T cell contact. Furthermore, MKp augmented Th17 responses against Candida albicans, a serious opportunistic pathogen. These results indicate an immunologic role of MKp in situations associated with extramedullary hematopoiesis and mobilization of HSPC.