Background Though most patients with multiple sclerosis (MS) presented earlier on as a relapsing-remitting (RR) disease, disability progression eventually occurred. Uncovering the mechanisms underlying progression may facilitate the unmet need for developing therapies to prevent progression. Benign MS (BMS), a rare form of MS, is the opposite from secondary progressive MS (SPMS) in that it lacks disease progression defined as Expanded Disability Status Scale (EDSS) ≤3 after at least 15 years of disease onset. BMS is characterized by rare and mild relapses with complete remission of clinical symptoms (lower activity of the disease) and lack of progression. Our study aims to identify transcriptomic and immunological differences between BMS and SPMS to unravel the pathogenesis of disease progression. Methods We took multi-modal approaches with microarrays, flow cytometry, and lipidomics by three-way comparisons of patients with BMS vs. RRMS (low disease activity vs. moderate or severe activity), RRMS vs. SPMS (continued activity vs. complete transformation into progressive phase) as well as BMS vs. SPMS, matched for age and disease-duration (low disease activity and no progression vs. progression with or without activity). Results We found that patients with RRMS and SPMS have a significantly higher percentage of B cells than those with BMS. BMS shows a different transcriptomic profile than SPMS. Many of the differentially expressed genes (DEGs) are involved in B cell-mediated immune responses. Additionally, long-chain fatty acids (LCFA), which can act as inflammatory mediators, are also altered in SPMS. Overall, our data suggest a role for the dysregulation of B cell differentiation and function, humoral immunity, and iron and lipid homeostasis in the pathogenesis of MS disease progression. Conclusion BMS has a unique transcriptomic and immunological profile compared to RRMS and SPMS. These differences will allow for personalized precision medicine and may ultimately lead to the discovery of new therapeutic targets for disease progression.

Human norovirus (HNoV) is a global health and socio-economic burden, estimated to infect every individual at least five times during their lifetime. The underlying mechanism for the potential lack of long-term immune protection from HNoV infections is not understood and prompted us to investigate HNoV susceptibility of primary human B cells and its functional impact. Primary B cells isolated from whole-blood were infected with HNoV-positive stool samples and harvested 3 days post infection (dpi) to assess viral RNA yield by RT-qPCR. A 3-18 fold increase in HNoV RNA yield was observed in 50-60% donors. Infection was further confirmed in B cells derived from splenic and lymph node biopsies. Next, we characterized infection of whole-blood derived B cells by flow cytometry in specific functional B cell subsets (naïve CD27-IgD+, memory switched CD27+IgD-, memory unswitched CD27+IgD+ and double-negative CD27-IgD-). While susceptibility of subsets was similar, we observed changes in B cell subsets distribution upon infection that were recapitulated after treatment with HNoV virus-like particles and mRNA encoding for HNoV NS1-2 protein. Importantly, treatment of immortalized BJAB B cell lines with the predicted recombinant NS1 protein triggered cell proliferation, increased ATP production, and induced metabolic changes, as detected by means of CFSE/Ki67 staining, seahorse analysis and metabolomics, respectively. These data demonstrate the susceptibility of primary B cells to HNoV infection and suggest that the secreted NS1 protein affects B cell function, proliferation and metabolism in vitro , which could have implications for viral pathogenesis and immune response in vivo .Importance Human norovirus (HNoV) is the most prevalent causative agent of gastroenteritis worldwide. Infection results in a self-limiting disease that can become chronic and severe in the immunocompromised, elderly and infants. There are currently no approved therapeutic and preventative strategies to limit the health and socio-economic burden associated with HNoV infections. Moreover, HNoV does not elicit life-long immunity as repeat infections are common, presenting a challenge for vaccine development. Given the importance of B cells for humoral immunity, we investigated susceptibility and impact of HNoV infection on human B cells. We found that HNoV replicates in human primary B cells derived from blood, spleen and lymph nodes specimens and induces functional changes in B cells, mediated in part by the non-structural protein NS1. Because of the secreted nature of NS1, we put forward the hypothesis that HNoV infection can modulate bystander B cell function with potential implications in systemic immune response.

Insulin receptor (IR) expression on the T cell surface can indicate an activated state; however, the IR is also chemotactic, enabling T cells with high IR expression to physically move toward insulin. In humans with type 1 diabetes (T1D) and the NOD mouse model, a T cell-mediated autoimmune destruction of insulin-producing pancreatic beta cells occurs. In previous work, when purified IR+ and IR- T cells were sorted from diabetic NOD mice and transferred into irradiated nondiabetic NOD mice, only those that received IR+ T cells developed insulitis and diabetes. In this study, peripheral blood samples from individuals with T1D (new onset to 14 y of duration), relatives at high-risk for T1D, defined by positivity for islet autoantibodies, and healthy controls were examined for frequency of IR+ T cells. High-risk individuals had significantly higher numbers of IR+ T cells as compared with those with T1D (p < 0.01) and controls (p < 0.001); however, the percentage of IR+ T cells in circulation did not differ significantly between T1D and control subjects. With the hypothesis that IR+ T cells traffic to the pancreas in T1D, we developed a (to our knowledge) novel mouse model exhibiting a FLAG-tagged mouse IR on T cells on the C57BL/6 background, which is not susceptible to developing T1D. Interestingly, these C57BL/6-CD3FLAGmIR/mfm mice showed evidence of increased IR+ T cell trafficking into the islets compared with C57BL/6 controls (p < 0.001). This transgenic animal model provides a (to our knowledge) novel platform for investigating the influence of IR expression on T cell trafficking and the development of insulitis.

B lymphocytes make several contributions to immune regulation including production of antibodies with regulatory properties, release of immune suppressive cytokines, and expression of death-inducing ligands. A role for Fas ligand (FasL)-expressing "killer" B cells in regulating T helper (TH) cell survival and chronic inflammation has been demonstrated in animal models of schistosome worm and other infections, asthma, autoimmune arthritis, and type 1 diabetes. FasL+ B cells were also capable of inducing immune tolerance in a male-to-female transplantation model. Interestingly, populations of B cells found in the spleen and lungs of naïve mice constitutively expresses FasL and have potent killer function against TH cells that is antigen-specific and FasL-dependent. Epstein-Barr virus-transformed human B cells constitutively express FasL and package it into exosomes that co-express MHC Class II molecules and have killer function against antigen-specific TH cells. FasL+ exosomes with markers of B-cell lineage are abundant in the spleen of naïve mice. Killer B cells therefore represent a novel target for immune modulation in many disease settings. Our laboratory has published methods of characterizing FasL+ B cells and inducing their proliferation in vitro. This updated chapter will describe methods of identifying and expanding killer B cells from mice, detecting FasL expression in B cells, extracting FasL+ exosomes from spleen and culture supernatants, and performing functional killing assays against antigen-specific TH cells.

An amendment to this paper has been published and can be accessed via the original article.

Human norovirus (HNoV) is a global health and socio-economic burden, estimated to infect every individual at least five times during their lifetime. The underlying mechanism for the potential lack of long-term immune protection from HNoV infections is not understood and prompted us to investigate HNoV susceptibility of primary human B cells and its functional impact. Primary B cells isolated from whole-blood were infected with HNoV-positive stool samples and harvested 3 days post infection (dpi) to assess viral RNA yield by RT-qPCR. A 3-18 fold increase in HNoV RNA yield was observed in 50-60% donors. Infection was further confirmed in B cells derived from splenic and lymph node biopsies. Next, we characterized infection of whole-blood derived B cells by flow cytometry in specific functional B cell subsets (naïve CD27 - IgD + , memory switched CD27 + IgD - , memory unswitched CD27 + IgD + and double-negative CD27 - IgD - ). While susceptibility of subsets was similar, we observed changes in B cell subsets distribution upon infection that were recapitulated after treatment with HNoV virus-like particles and mRNA encoding for HNoV NS1-2 protein. Importantly, treatment of immortalized BJAB B cell lines with the predicted recombinant NS1 protein triggered cell proliferation, increased ATP production, and induced metabolic changes, as detected by means of CFSE/Ki67 staining, seahorse analysis and metabolomics, respectively. These data demonstrate the susceptibility of primary B cells to HNoV infection and suggest that the secreted NS1 protein affects B cell function, proliferation and metabolism in vitro , which could have implications for viral pathogenesis and immune response in vivo . Importance Human norovirus (HNoV) is the most prevalent causative agent of gastroenteritis worldwide. Infection results in a self-limiting disease that can become chronic and severe in the immunocompromised, elderly and infants. There are currently no approved therapeutic and preventative strategies to limit the health and socio-economic burden associated with HNoV infections. Moreover, HNoV does not elicit life-long immunity as repeat infections are common, presenting a challenge for vaccine development. Given the importance of B cells for humoral immunity, we investigated susceptibility and impact of HNoV infection on human B cells. We found that HNoV replicates in human primary B cells derived from blood, spleen and lymph nodes specimens and induces functional changes in B cells, mediated in part by the non-structural protein NS1. Because of the secreted nature of NS1, we put forward the hypothesis that HNoV infection can modulate bystander B cell function with potential implications in systemic immune response.

BACKGROUND. Siponimod (BAF312) is a selective sphingosine-1-phosphate receptor 1 and 5 (S1PR1, S1PR5) modulator recently approved for active secondary progressive multiple sclerosis (SPMS). The immunomodulatory effects of siponimod in SPMS have not been previously described. METHODS. We conducted a multicentered, randomized, double-blind, placebo-controlled AMSO4 mechanistic study with 36 SPMS participants enrolled in the EXPAND trial. Gene expression profiles were analyzed using RNA derived from whole blood with Affymetrix Human Gene ST 2.1 microarray technology. We performed flow cytometry-based assays to analyze the immune cell composition and microarray gene expression analysis on peripheral blood from siponimod-treated participants with SPMS relative to baseline and placebo during the first-year randomization phase. RESULTS. Microarray analysis showed that immune-associated genes involved in T and B cell activation and receptor signaling were largely decreased by siponimod, which is consistent with the reduction in CD4(+)T cells, CD8(+) T cells, and B cells. Flow cytometric analysis showed that within the remaining lymphocyte subsets there was a reduction in the frequencies of CD4(+) and CD8(+) naive T cells and central memory cells, while T effector memory cells, antiinflammatory Th2, and T regulatory cells (Tregs) were enriched. Transitional regulatory B cells (CD24(hi)CD38(hi)) and B1 cell subsets (CD43(+)CD27(+)) were enriched, shifting the balance in favor of regulatory B cells over memory B cells. The proregulatory shift driven by siponimod treatment included a higher proliferative potential of Tregs compared with non-Tregs, and upregulated expression of PD-1 on Tregs. Additionally, a positive correlation was found between Tregs and regulatory B cells in siponimod-treated participants. CONCLUSION. The shift toward an antiinflammatory and suppressive homeostatic immune system may contribute to the clinical efficacy of siponimod in SPMS.

The programmed death-1 (PD-1) axis can suppress immune surveillance against multiple myeloma (MM). We tested the safety and efficacy of pembrolizumab, an anti-PD-1 antibody, in MM after autologous hematopoietic cell transplantation (AHCT). We enrolled patients with MM who did not achieve a complete response (CR) to induction therapy. The study intervention involved a total of 9 doses of i.v. pembrolizumab, with 1 dose given every 21 days starting on day +14 post-AHCT. The primary endpoint was the rate of CR at end of treatment (EOT) in patients receiving ≥2 pembrolizumab doses. Thirty-two patients were enrolled, but 3 withdrew consent before receiving the first dose. The study was terminated early after failing to meet its interim analysis endpoint to detect a 20% difference in EOT CR rate conversion. The median patient age was 59 years. All but 1 patient received triplet induction for a median of 4 cycles (range, 2 to 7 cycles), with 69% partial response (PR) and 31% very good PR (VGPR). No grade 4/5 toxicities or graft failures occurred. Among 26 evaluable patients, 23 had an EOT evaluation, and 7 of these 23 (31%) achieved CR. Two patients had EOT serologic CR but no bone marrow confirmation (CRu), and 1 patient had no EOT evaluation. Bone marrow was minimal residual disease-negative by flow cytometry in 12 of 16 patients (75%) at day +180. With a median follow-up of 23.7 months (range, 15.1 to 33.5 months), no patient achieving EOT CR/CRu had relapsed, whereas 3 patients progressed before EOT and 1 patient progressed at 8 months after EOT VGPR. The estimated 2-year progression-free rate was 83% (95% confidence interval, 68% to 100%). Our data show that early post-AHCT pembrolizumab with lenalidomide maintenance is feasible; however, the efficacy is uncertain and requires further study. This trial was registered at ClinicalTrials.gov (NCT02331368).

Autoimmune retinopathy (AIR) is a treatable condition that manifests in acute and progressive vision loss in patients. It has recently been determined that AIR is associated with an imbalance of TH1 versus regulatory T cell immunity toward the retinal protein, recoverin. This study describes a new murine model to understand the immunopathology of AIR and its association with T cell responses toward recoverin. Immunization of C57BL/6 mice with recoverin resulted in ocular inflammation including infiltration of CD4+ and CD8+ T lymphocytes, B cells, and CD11b+Ly6C+ inflammatory monocytes in the eyes. Production of IFN-γ and IL-17 from T cells was exacerbated in IL-10 knockout (KO) mice and kinetics of disease development was accelerated. Infiltration of T cells and inflammatory monocytes into the eyes dramatically increased in recoverin-immunized IL-10 KO mice. An immunodominant peptide of recoverin, AG-16, was capable of inducing disease in IL-10 KO mice and resulted in expansion of AG-16 tetramer-specific CD4+ T cells in lymphoid organs and eyes. Adoptive transfer of recoverin-stimulated cells into naive mice was sufficient to induce AIR, and immunization of B cell-deficient mice led to a milder form of the disease. This model supports the hypothesis that recoverin-specific T cell responses are major drivers of AIR pathogenesis and that IL-10 is an important factor in protection.

Purpose: To determine if immunological markers (1) are significantly different between autoimmune retinopathy (AIR) patients and controls and (2) correlate with disease progression in AIR patients. Methods: We enrolled patients with a possible AIR diagnosis, as well as control participants without eye disease, autoimmunity, or cancer. Immunological markers were tested in all participants. In addition, AIR patients had up to three blood draws for testing over their disease course. For AIR patients, clinical measures, including visual acuity (VA) and Goldmann visual field (GVF) area, were recorded at each draw. We used the Mann–Whitney U test to compare the immunological markers between AIR patients and controls. We used multilevel mixed-effect regression to investigate the correlation between markers and clinical parameters over time in AIR patients. Results: Seventeen patients with AIR and 14 controls were included. AIR patients had a higher percent of monocytes (Z = 3.076, P = 0.002). An increase in immunoglobulin G against recoverin was correlated with a VA decrease (β = 0.0044, P < 0.0001). An increase in monocyte proportion was correlated with a decrease in GVF area (β = −7.27, P = 0.0021). Several markers of B-cell depletion were correlated with GVF improvement. Conclusions: Monocytes may play a role in AIR pathophysiology and be a disease activity marker. B-cell depletion markers correlated with clinical parameter improvement, particularly GVF. Translational Relevance: This work elucidates immunologic markers that may improve the accuracy of diagnosis and treatment of AIR.

The role of regulatory B cells (Bregs) in modulating immune responses and maintaining tolerance are well established. However, how cytokines present during immune responses affect Breg growth and function are not as well defined. Previously, our laboratory reported IL-5- and mCD40L-expressing fibroblast (mCD40L-Fb) stimulation induced IL-10 production from murine B cells. The current study investigated the phenotype and functional relevance of IL-10 producing B cells from this culture. We found IL-5/mCD40L-Fb stimulation induced IL-10 production exclusively from CD5(+) splenic B cells of naive mice. After stimulation, the resulting IL-10(+) B cells displayed markers of multiple reported Breg phenotypes. Interestingly, when investigating effects of IL-4 (a critical T(H)2 cytokine) on IL-5/mCD40L-Fb induced IL-10 production, we found IL-4 inhibited IL-10 production in a STAT6-dependent manner. Upon adoptive transfer, CD5(+) B cells previously stimulated with IL-5/mCD40L-Fb were able to reduce development of OVA-induced allergic airway disease in mice. Using B cells from IL-10 mutant mice differentiated by IL-5/mCD40L-Fb, we found protection from allergic airway disease development was dependent on the IL-10 production from the transferred B cells. Bregs have been shown to play crucial roles in the immune tolerance network, and understanding stimuli that modulate their growth and function may be key in development of future treatments for diseases of immune dysregulation.

Autoimmune retinopathy (AIR) was often mistaken for retinitis pigmentosa (RP), due to an overlap of clinical findings, but increasingly has been recognized as a unique entity in the last decade. AIR has distinctive features: sudden onset of photopsias and scotomata in patients with no family history of RP, followed by visual field and central vision loss. Initially, retina exams are normal with no sign of pigment deposits or retinal degeneration. A family history of autoimmune diseases (all types) occurs in 60% of patients. One hallmark of AIR has been the presence of anti-retinal autoimmune antibodies (ARAs) in patients' sera, but patients can continue to have ARAs even when the disease has been quiescent for years. The accumulation of ARAs represents a breakdown of retinal immune tolerance with many different immunoreactive bands found at different reference weights in AIR patients. We began investigating cellular immunity using flow cytometry and found abnormal distributions (>2 StDev) of increased memory lymphocytes and NK cells and decreased regulatory B cell subsets in many AIR patients compared to normal controls. Culture of patient lymphocytes with small amounts (25 μg) of recoverin protein for 6 days led to significant elevations of interferon gamma (IFNγ) and in some cases tumor necrosis factor alpha (TNFα) production. We found the IFNγ/IL-10 ratio in response to recoverin was elevated in patients with more active disease (defined by visual field contraction between visits), but in some patients, there also appeared to be independent factors influencing severity, suggesting other autoimmune mechanisms were at play. These cellular immune parameters may provide improved markers for active AIR.

Autoimmune retinopathy (AIR) causes rapidly progressive vision loss that is treatable but often is confused with other forms of retinal degeneration including retinitis pigmentosa (RP). Measurement of anti-retinal antibodies (ARA) by Western blot is a commonly used laboratory assay that supports the diagnosis yet does not reflect current disease activity. To search for better diagnostic indicators, this study was designed to compare immune biomarkers and responses toward the retinal protein, recoverin, between newly diagnosed AIR patients, slow progressing RP patients and healthy controls. All individuals had measurable anti-recoverin IgG and IgM antibodies by ELISA regardless of disease status or Western blot results. Many AIR patients had elevated anti-recoverin IgG1 levels and a strong cellular response toward recoverin dominated by IFNγ. RP patients and controls responded to recoverin with a lower IFNγ response that was balanced by IL-10 production. Both AIR and RP patients displayed lower levels of total peripheral blood mononuclear cells that were due to reductions of CD4+ TH cells. A comparison of messenger RNA (mRNA) for immune-related genes in whole blood of AIR patients versus RP patients or controls indicated lower expression of ATG5 and PTPN22 and higher expression of several genes involved in TH cell signaling/transcription and adhesion. These data indicate that an immune response toward recoverin is normal in humans, but that in AIR patients the balance shifts dramatically toward higher IFNγ production and cellular activation.

We have previously shown that mouse B lymphocytes can express Fas ligand (FasL) on their cell surfaces and can kill peptide antigen-specific T helper cells. In humans, FasL protein produced by human B cells was exclusively found intracellularly on the surface of exosomes. In the current study we determined that mouse B cells are a major source of FasL+ exosomes, as well as contributing significantly to the Granzme B+ exosome pool. The major B cell subsets in the spleen and lungs that produced FasL and Granzyme B were marked by CD9 and/or CD107a expression. We tested a panel of toll-like receptor ligands in combination with anti-IgM and CD40 ligand for their ability to activate killer function in purified mouse B cells. The TLR2 ligand Pam3CSK4 was a potent inducer of surface FasL expression and FasL+ exosome release from B cells. Using a mouse model of OVA-specific allergic airways disease, we showed that transfer of Pam3CSK4-induced B cell-derived exosomes diminished total numbers of eosinophils and CD4+ T cells in the bronchoalveolar lavage fluid (BAL). Lung TH cell apoptosis was higher in the mice that received exosome transfer. Lung cells produced less IL-4 and IL-5 upon restimulation with OVA in the exosome-treated mice. Effects of Pam3CSK4-induced exosomes on BAL cell infiltration, TH cell apoptosis and cytokine production were all diminished when exosomes were derived from mice with a functional mutation of the FasL gene. These data indicate a potential role for B cell-derived killer exosomes in control of allergic airways disease.

Autoimmune retinopathy (AIR) causes acute and progressive vision loss in patients. We have established a murine model using the retinal autoantigen, recoverin, to better understand the immunopathology of AIR. Immunization of C57BL6 mice with recombinant mouse recoverin resulted in systemic recoverin-specific Th1 and Th17 cell responses and infiltration of CD4+ and CD8+ T lymphocytes, B lymphocytes, and CD11b+Ly6C+ inflammatory monocytes into the eyes. Treatment of mice with rapamycin at the time of immunization suppressed the induction of recoverin immunity and reduced inflammation in the eyes compared to the untreated group. Rapamycin dampened Th1 and Th17 T cell responses in draining lymph nodes and lowered serum antibody titers toward recoverin. There was a significant decrease in the number of CD4+ T cells and CD11b+Ly6C+ inflammatory monocytes infiltrating the eyes of rapamycin-treated mice. A higher number of CD103+CD8+ tissue resident memory T cells were present in the eyes of rapamycin treated mice. Treatment resulted in a significant decrease in the frequency of CD122+CD69−PD-1−CD8+ and the total number of CD44+CD62L+ memory T cells in lymphoid organs. While adoptive transfer of T cells from recoverin-immunized mice into naïve mice led to pathological changes in the eye, adoptive transfer of T cells from a rapamycin treated group did not result in eye pathology in the recipient. Treatment of mice with rapamycin at later time points after disease induction did not prevent disease, however, transfer of recoverin-specific T cells from those mice into recipient mice failed to induce disease. Our findings indicate rapamycin may be an effective drug for suppression of autoimmune retinopathy in some circumstances.

Autoimmune retinopathy (AIR) is a condition that manifests in acute and progressive vision loss in humans. Antibodies against the retinal protein recoverin are frequently detected in AIR patients. We have established a murine model to better understand the immunopathology of AIR. Mice were immunized subcutaneously with recombinant mouse recoverin (100–200 μg) emulsified in complete Freund’s adjuvant (CFA) and intraperitoneally with pertussis toxin (400 ng). After three weeks, the immunized mice were scanned with optical coherence tomography (OCT) for detection of pathological changes in the eyes. Cells from spleen and draining lymph nodes were restimulated with recoverin (5 μg/ml) for 4 days. Immunization of C57BL/6 and BALB/c mice with mouse recoverin resulted in recoverin-specific T cell responses. Production of IFN-γ and IL-17 were observed in cells harvested from draining lymph nodes and spleen of the immunized mice upon restimulation in vitro with recoverin. Immunization also led to production of high titers of recoverin-specific antibodies (1/400) in the immunized mice. The recoverin-specific Th1 and Th17 cell response was augmented in IL-10 KO mice, whereas humoral response was unaffected. More importantly, the number of lymphocytes infiltrated into the eyes dramatically increased in IL-10 KO mice upon immunization with recoverin. Immunization of Fas ligand deficient GLD mice with recoverin antigen led to a predominant Th17 cell response toward recoverin. These new insights regarding the anti-recoverin immune response have led us to hypothesize that skewing of recoverin-specific T cell response toward inflammatory Th1 and/or Th17 responses can drive the pathogenesis of AIR.