Challenges and Opportunities for Biomarkers of Clinical Response to AHSCT in Autoimmunity

Dynamics of T cell repertoire renewal following autologous hematopoietic stem cell transplantation in multiple sclerosis

Autologous hematopoietic stem cell transplantation (aHSCT) is a highly effective treatment of multiple sclerosis (MS). It depletes autoreactive cells and subsequently renews adaptive immune cells. The possible proinflammatory potential of surviving T cells early after aHSCT has not been studied. Here, we examined the dynamics of new and surviving T cells in 27 patients after aHSCT by multidimensional flow cytometry, T cell receptor (TCR) sequencing, specificity testing, telomere length profiling, and HLA genotyping. Early after aHSCT, naïve T cells are barely detectable, whereas effector memory (EM) T cells quickly reconstitute to pre-aHSCT values. EM CD4+T cells early after aHSCT have shorter telomeres, have higher expression of senescence and exhaustion markers, and proliferate less than those before aHSCT. We find a median TCR repertoire overlap of 26% between the early post-aHSCT EM CD4+T cells and pre-aHSCT, indicating persistence of EM CD4+T cells early after transplantation. The EM CD4+TCR repertoire overlap declines to 15% at 12 months after aHSCT, whereas the naïve TCR repertoire entirely renews. HLA-DR–associated EM CD4+T cell reactivity toward MS-related antigens decreased after aHSCT, whereas reactivity toward EBV increased. Our data show substantial survival of pre-aHSCT EM CD4+T cells early after transplantation but complete renewal of the T cell repertoire by nascent T cells later.

B-Cell Reconstitution After Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Autologous hematopoietic stem cell transplantation (aHSCT) is increasingly used to treat aggressive forms of multiple sclerosis (MS). This procedure is believed to result in an immune reset and restoration of a self-tolerant immune system. Immune reconstitution has been extensively studied for T cells, but only to a limited extent for B cells. As increasing evidence suggests an important role of B cells in MS pathogenesis, we sought here to better understand reconstitution and the extent of renewal of the B-cell system after aHSCT in MS.

METHODS

Using longitudinal multidimensional flow cytometry and immunoglobulin heavy chain (IgH) repertoire sequencing following aHSCT with BCNU + Etoposide + Ara-C + Melphalan anti-thymocyte globulin, we analyzed the B-cell compartment in a cohort of 20 patients with MS in defined intervals before and up to 1 year after aHSCT and compared these findings with data from healthy controls.

RESULTS

Total B-cell numbers recovered within 3 months and increased above normal levels 1 year after transplantation, successively shifting from a predominantly transitional to a naive immune phenotype. Memory subpopulations recovered slowly and remained below normal levels with reduced repertoire diversity 1 year after transplantation. Isotype subclass analysis revealed a proportional shift toward IgG1-expressing cells and a reduction in IgG2 cells. Mutation analysis of IgH sequences showed that highly mutated memory B cells and plasma cells may transiently survive conditioning while the analysis of sequence cluster overlap, variable (IGHV) and joining (IGHJ) gene usage and repertoire diversity suggested a renewal of the late posttransplant repertoire. In patients with early cytomegalovirus reactivation, reconstitution of naive and memory B cells was delayed.

DISCUSSION

Our detailed characterization of B-cell reconstitution after aHSCT in MS indicates a reduced reactivation potential of memory B cells up to 1 year after transplantation, which may leave patients susceptible to infection, but may also be an important aspect of its mechanism of action.

Enzyme-Activated, Chemiluminescent Siderophore-Dioxetane Probes Enable the Selective and Highly Sensitive Detection of Bacterial Pathogens

The sensitive detection of bacterial infections is a prerequisite for their successful treatment. The use of a chemiluminescent readout was so far hampered by an insufficient probe enrichment at the pathogens. We coupled siderophore moieties, that harness the unique iron transport system of bacteria, with enzyme‐activatable dioxetanes and obtained seven trifunctional probes with high signal‐to‐background ratios (S/B=426‐859). Conjugates with efficient iron transport capability into bacteria were identified through a growth recovery assay. All ESKAPE pathogens were labelled brightly by desferrioxamine conjugates, while catechols were weaker due to self‐quenching. Bacteria could also be detected inside lung epithelial cells. The best probe 8 detected 9.1×10³ CFU mL⁻¹ of S. aureus and 5.0×10⁴ CFU mL⁻¹ of P. aeruginosa, while the analogous fluorescent probe 10 was 205–305fold less sensitive. This qualifies siderophore dioxetane probes for the selective and sensitive detection of bacteria.

Haematopoietic Stem Cell Transplantation Results in Extensive Remodelling of the Clonal T Cell Repertoire in Multiple Sclerosis

Autologous haematopoietic stem cell transplantation (AHSCT) is a vital therapeutic option for patients with highly active multiple sclerosis (MS). Rates of remission suggest AHSCT is the most effective form of immunotherapy in controlling the disease. Despite an evolving understanding of the biology of immune reconstitution following AHSCT, the mechanism by which AHSCT enables sustained disease remission beyond the period of lymphopenia remains to be elucidated. Auto-reactive T cells are considered central to MS pathogenesis. Here, we analyse T cell reconstitution for 36 months following AHSCT in a cohort of highly active MS patients. Through longitudinal analysis of sorted naïve and memory T cell clones, we establish that AHSCT induces profound changes in the dominant T cell landscape of both CD4+ and CD8+ memory T cell clones. Lymphopenia induced homeostatic proliferation is followed by clonal attrition; with only 19% of dominant CD4 (p <0.025) and 13% of dominant CD8 (p <0.005) clones from the pre-transplant repertoire detected at 36 months. Recovery of a thymically-derived CD4 naïve T cell repertoire occurs at 12 months and is ongoing at 36 months, however diversity of the naïve populations is not increased from baseline suggesting the principal mechanism of durable remission from MS after AHSCT relates to depletion of putative auto-reactive clones. In a cohort of MS patients expressing the MS risk allele HLA DRB1*15:01, public clones are probed as potential biomarkers of disease. AHSCT appears to induce sustained periods of disease remission with dynamic changes in the clonal T cell repertoire out to 36 months post-transplant.

Immunological consequences of "immune reconstitution therapy" in multiple sclerosis: A systematic review

Immune reconstitution therapy (IRT) is an emerging concept for the treatment of multiple sclerosis (MS) that is given intermittently and can induce long-term remission of MS that is sustained in treatment-free periods. A systematic literature review was performed to identify and summarize current knowledge regarding the short- and long-term immunological consequences of different IRTs and CD20 depleting therapies on the cellular level in patients with MS. A total of 586 articles published between January 2010 and September 2019 were identified and screened; 44 studies met inclusion criteria for the review. All the treatments considered appeared to produce both qualitative and quantitative changes in the immune cell populations of patients with MS that resulted in a more anti-inflammatory immune profile. Autologous hematopoietic stem cell transplantation produced the longest-lasting and greatest effects on a wide range of immune cells. Many patients achieved prolonged depletion of the adaptive immune system when alemtuzumab and cladribine tablets were administered as short courses of therapy; however, a proportion of patients required retreatment to maintain these effects. Alemtuzumab may produce greater depletion of both CD4+ and CD8+ T cells than cladribine tablets, although both treatments similarly deplete B cells. Recovery of B cells before T cell recovery and hyperpopulation of B cells after alemtuzumab may contribute to secondary autoimmunity. Cladribine tablets had a greater effect on B cells than T cells, and no hyperpopulation of B cells was observed after treatment with cladribine tablets. Ocrelizumab and rituximab require regular repeated treatment every 6 months to maintain depletion of B and T cells. Effects of the drug treatments on the innate immune system were minor compared with those on the adaptive immune system. Additional characterization of the cellular changes occurring during IRT and CD20 depletion may lead to further improvement in the understanding of the pathogenesis of MS and the future development of therapies with even longer lasting effects. Although the treatments considered in this review improve quality of life and outcomes for patients with MS, a cure for this debilitating disease is not yet in sight.

Extensive intrathecal T cell renewal following hematopoietic transplantation for multiple sclerosis

A recent study of autologous hematopoietic stem cell transplantation (AHSCT) for active relapsing-remitting multiple sclerosis (RRMS) showed efficacy in preventing disease worsening. However, the immunologic basis for efficacy remains poorly defined. Multiple sclerosis pathology is known to be driven by inflammatory T cells that infiltrate the CNS. Therefore, we hypothesized that the preexisting T cell repertoire in the intrathecal compartment of active RRMS participants was ablated and replaced with new clones following AHSCT. T cell repertoires were assessed using high-throughput TCRβ chain sequencing in paired cerebrospinal fluid (CSF) and peripheral blood CD4+ and CD8+ T cells from participants that underwent AHSCT, before and up to 4 years following transplantation. More than 90% of the preexisting CSF repertoire in participants with active RRMS was removed following AHSCT and replaced with clonotypes predominantly generated from engrafted autologous stem cells. Of the preexisting clones in CSF, approximately 60% were also detected in blood before therapy, and concordant treatment effects were observed for clonotypes in both compartments following AHSCT. These results indicate that replacement of the preexisting TCR repertoire in active RRMS is a mechanism for AHSCT efficacy and suggest that peripheral blood could serve as a surrogate for CSF to define mechanisms associated with efficacy in future studies of AHSCT.

Bidirectional Role of β2-Adrenergic Receptor in Autoimmune Diseases

Disorder of the sympathetic nervous system (SNS) is closely related to the pathogenesis of various autoimmune diseases (ADs). Catecholamine triggered beta2-adrenergic receptor (β2-AR) signaling is important in creating a bidirectional response in the progression of ADs due to factors including diverse expression patterns, single nucleotide polymorphisms (SNPs), biased signals, and desensitization of β2-AR, as well as different subtypes of Gα binding to β2-AR. In this review, we summarize the actions of β2-AR signaling in regulating the functions of immunocytes and in the pathogenesis of ADs, and the application of β2-AR agonists or antagonists in treating major types of ADs is also discussed. We suggest that restoring the immune balance via a soft regulation of the expression or activation of β2-AR is one of the promising therapeutic strategies for systematic ADs.