Roadmap for understanding mechanisms on how Epstein-Barr virus triggers multiple sclerosis and for translating these discoveries in clinical trials

Here, we offer a roadmap for what might be studied next in understanding how EBV triggers MS. We focus on two areas: The first area concerns the molecular mechanisms underlying how clonal antibody in the CSF emanates in widespread molecular mimicry to key antigens in the nervous system including GlialCAM, a protein associated with chloride channels. A second and equally high priority in the roadmap concerns various therapeutic approaches that are related to blocking the mechanisms whereby EBV triggers MS. Therapies deserving of attention include clinical trials with antivirals and the development of 'inverse' vaccines based on nucleic acid technologies to control or to eradicate the consequences of EBV infection. High enthusiasm is given to continuation of ongoing clinical trials of cellular adoptive therapy to attack EBV-infected cells. Clinical trials of vaccines to EBV are another area deserving attention. These suggested topics involving research on mechanism, and the design, implementation and performance of well-designed trials are not intended to be an exhaustive list. We have splendid tools available to our community of medical scientists to tackle how EBV triggers MS and then to perhaps change the world with new therapies to potentially eradicate MS, as we have done with nearly complete success for poliomyelitis.

Autoantibodies against citrullinated and native proteins and prediction of rheumatoid arthritis-associated interstitial lung disease: A nested case-control study

Background

To identify fine specificity anti-citrullinated protein antibodies (ACPA) associated with incident rheumatoid arthritis-associated interstitial lung disease (RA-ILD).

Methods

This nested case-control study within the Brigham RA Sequential Study matched incident RA-ILD cases to RA-noILD controls on time of blood collection, age, sex, RA duration, and rheumatoid factor status. A multiplex assay measured ACPA and anti-native protein antibodies from stored serum prior to RA-ILD onset. Logistic regression models calculated odds ratios (OR) with 95% confidence intervals (CI) for RA-ILD, adjusting for prospectively-collected covariates. We estimated optimism-corrected area under the curves (AUC) using internal validation. Model coefficients generated a risk score for RA-ILD.

Findings

We analyzed 84 incident RA-ILD cases (mean age 67 years, 77% female, 90% White) and 233 RA-noILD controls (mean age 66 years, 80% female, 94% White). We identified six fine specificity antibodies that were associated with RA-ILD. The antibody isotypes and targeted proteins were: IgA2 to citrullinated histone 4 (OR 0.08 per log-transformed unit, 95% CI 0.03-0.22), IgA2 to citrullinated histone 2A (OR 4.03, 95% CI 2.03-8.00), IgG to cyclic citrullinated filaggrin (OR 3.47, 95% CI 1.71-7.01), IgA2 to native cyclic histone 2A (OR 5.52, 95% CI 2.38-12.78), IgA2 to native histone 2A (OR 4.60, 95% CI 2.18-9.74), and IgG to native cyclic filaggrin (OR 2.53, 95% CI 1.47-4.34). These six antibodies predicted RA-ILD risk better than all clinical factors combined (optimism-corrected AUC=0·84 versus 0·73). We developed a risk score for RA-ILD combining these antibodies with the clinical factors (smoking, disease activity, glucocorticoid use, obesity). At 50% predicted RA-ILD probability, the risk scores both without (score=2·6) and with (score=5·9) biomarkers achieved specificity ≥93% for RA-ILD.

Interpretation

Specific ACPA and anti-native protein antibodies improve RA-ILD prediction. These findings implicate synovial protein antibodies in the pathogenesis of RA-ILD and suggest clinical utility in predicting RA-ILD once validated in external studies.

Funding

National Institutes of Health.

Cytotoxic CD8+ T cells target citrullinated antigens in rheumatoid arthritis

The immune mechanisms that mediate synovitis and joint destruction in rheumatoid arthritis (RA) remain poorly defined. Although increased levels of CD8+ T cells have been described in RA, their function in pathogenesis remains unclear. Here we perform single cell transcriptome and T cell receptor (TCR) sequencing of CD8+ T cells derived from anti-citrullinated protein antibodies (ACPA)+ RA blood. We identify GZMB+CD8+ subpopulations containing large clonal lineage expansions that express cytotoxic and tissue homing transcriptional programs, while a GZMK+CD8+ memory subpopulation comprises smaller clonal expansions that express effector T cell transcriptional programs. We demonstrate RA citrullinated autoantigens presented by MHC class I activate RA blood-derived GZMB+CD8+ T cells to expand, express cytotoxic mediators, and mediate killing of target cells. We also demonstrate that these clonally expanded GZMB+CD8+ cells are present in RA synovium. These findings suggest that cytotoxic CD8+ T cells targeting citrullinated antigens contribute to synovitis and joint tissue destruction in ACPA+ RA.

FAT10 Induces cancer cell migration by stabilizing phosphorylated ABI3/NESH

The WAVE regulatory complex (WRC) is involved in various cellular processes by regulating actin polymerization. The dysregulation of WRC components is associated with cancer development. ABI family member 3 (ABI3)/new molecule including SH3 (NESH) is one of the WRC components and it has been reported that ABI3 phosphorylation can affect WRC function. Although several residues of ABI3 have been reported to be possible phosphorylation sites, it is still unclear which residues are important for the function of ABI3. Furthermore, it is unclear how the phosphorylated form of ABI3 is regulated. Here, we demonstrate that ABI3 is stabilized by its interaction with human leukocyte antigen-F adjacent transcript 10 (FAT10). Using phospho-dead or phospho-mimetic mutants of ABI3, we showed that serine 213 and 216 are important phosphorylation sites of ABI3. In particular, FAT10 has a higher affinity for the phosphorylated form of ABI3 than the non-phosphorylated form, and it stabilizes the phosphorylated form more than the non-phosphorylated form through this differential affinity. The interaction between FAT10 and the phosphorylated form of ABI3 promoted cancer cell migration. Therefore, our results suggest that FAT10 stabilizes the phosphorylated form of ABI3, which may lead to WRC activation, thereby promoting cancer cell migration.

Increased macrophage phagocytic activity with TLR9 agonist conjugation of an anti- Borrelia burgdorferi monoclonal antibody

Borrelia burgdorferi (Bb) infection causes Lyme disease, for which there is need for more effective therapies. Here, we sequenced the antibody repertoire of plasmablasts in Bb-infected humans. We expressed recombinant monoclonal antibodies (mAbs) representing the identified plasmablast clonal families, and identified their binding specificities. Our recombinant anti-Bb mAbs exhibit a range of activity in mediating macrophage phagocytosis of Bb. To determine if we could increase the macrophage phagocytosis-promoting activity of our anti-Bb mAbs, we generated a TLR9-agonist CpG-oligo-conjugated anti-BmpA mAb. We demonstrated that our CpG-conjugated anti-BmpA mAb exhibited increased peak Bb phagocytosis at 12-24 h, and sustained macrophage phagocytosis over 60+ hrs. Further, our CpG-conjugated anti-BmpA mAb induced macrophages to exhibit a sustained activation morphology. Our findings demonstrate the potential for TLR9-agonist CpG-oligo conjugates to enhance mAb-mediated clearance of Bb, and this approach might also enhance the activity of other anti-microbial mAbs.

RNA-seq characterization of histamine-releasing mast cells as potential therapeutic target of osteoarthritis

OBJECTIVE

Mast cells in the osteoarthritis (OA) synovium correlate with disease severity. This study aimed to further elucidate the role of mast cells in OA by RNA-Seq analysis and pharmacological blockade of the activity of histamine, a key mast cell mediator, in murine OA.

METHODS

We examined OA synovial tissues and fluids by flow cytometry, immunostaining, single-cell and bulk RNA-Seq, qPCR, and ELISA. Cetirizine, a histamine H1 receptor (H1R) antagonist, was used to treat the destabilization of the medial meniscus (DMM) mouse model of OA.

RESULTS

Flow cytometry and immunohistology analysis of OA synovial cells revealed KIT+ FcεRI+ and TPSAB1+ mast cells. Single-cell RNA-Seq of OA synovial cells identified the expression of prototypical mast cell markers KIT, TPSAB1, CPA3 and HDC, as well as distinctive markers HPGD, CAVIN2, IL1RL1, PRG2, and CKLF, confirmed by bulk RNA-Seq and qPCR. A mast cell prototypical marker expression score classified 40 OA patients into three synovial pathotypes: mast cell-high, -medium, and -low. Additionally, we detected mast cell mediators including histamine, tryptase AB1, CPA3, PRG2, CAVIN2, and CKLF in OA synovial fluids. Elevated H1R expression was detected in human OA synovium, and treatment of mice with the H1 receptor antagonist cetirizine reduced the severity and OA-related mediators in DMM.

CONCLUSION

Based on differential expression of prototypical and distinct mast cell markers, human OA joints can be stratified into mast cell-high, -medium, and -low synovial tissue pathotypes. Pharmacologic blockade of histamine activity holds the potential to improve OA disease outcome.

Clonal IgA and IgG autoantibodies from individuals at risk for rheumatoid arthritis identify an arthritogenic strain of Subdoligranulum

The mucosal origins hypothesis of rheumatoid arthritis (RA) proposes a central role for mucosal immune responses in the initiation or perpetuation of the systemic autoimmunity that occurs with disease. However, the connection between the mucosa and systemic autoimmunity in RA remains unclear. Using dual immunoglobulin A (IgA) and IgG family plasmablast-derived monoclonal autoantibodies obtained from peripheral blood of individuals at risk for RA, we identified cross-reactivity between RA-relevant autoantigens and bacterial taxa in the closely related families Lachnospiraceae and Ruminococcaceae. After generating bacterial isolates within the Lachnospiraceae/Ruminococcaceae genus Subdoligranulum from the feces of an individual, we confirmed monoclonal antibody binding and CD4⁺ T cell activation in individuals with RA compared to control individuals. In addition, when Subdoligranulum isolate 7 but not isolate 1 colonized germ-free mice, it stimulated T_H17 cell expansion, serum RA-relevant IgG autoantibodies, and joint swelling reminiscent of early RA, with histopathology characterized by antibody deposition and complement activation. Systemic immune responses were likely due to mucosal invasion along with the generation of colon-isolated lymphoid follicles driving increased fecal and serum IgA by isolate 7, because B and CD4⁺ T cell depletion not only halted intestinal immune responses but also eliminated detectable clinical disease. In aggregate, these findings demonstrate a mechanism of RA pathogenesis through which a specific intestinal strain of bacteria can drive systemic autoantibody generation and joint-centered antibody deposition and immune activation.

Clonal IgA and IgG autoantibodies from individuals at risk for rheumatoid arthritis identify an arthritogenic strain of Subdoligranulum

The mucosal origins hypothesis of rheumatoid arthritis (RA) proposes a central role for mucosal immune responses in the initiation or perpetuation of the systemic autoimmunity that occurs with disease. However, the connection between the mucosa and systemic autoimmunity in RA remains unclear. Using dual immunoglobulin A (IgA) and IgG family plasmablast-derived monoclonal autoantibodies obtained from peripheral blood of individuals at risk for RA, we identified cross-reactivity between RA-relevant autoantigens and bacterial taxa in the closely related families Lachnospiraceae and Ruminococcaceae. After generating bacterial isolates within the Lachnospiraceae/Ruminococcaceae genus Subdoligranulum from the feces of an individual, we confirmed monoclonal antibody binding and CD4⁺ T cell activation in individuals with RA compared to control individuals. In addition, when Subdoligranulum isolate 7 but not isolate 1 colonized germ-free mice, it stimulated T_H17 cell expansion, serum RA-relevant IgG autoantibodies, and joint swelling reminiscent of early RA, with histopathology characterized by antibody deposition and complement activation. Systemic immune responses were likely due to mucosal invasion along with the generation of colon-isolated lymphoid follicles driving increased fecal and serum IgA by isolate 7, because B and CD4⁺ T cell depletion not only halted intestinal immune responses but also eliminated detectable clinical disease. In aggregate, these findings demonstrate a mechanism of RA pathogenesis through which a specific intestinal strain of bacteria can drive systemic autoantibody generation and joint-centered antibody deposition and immune activation.

Mechanism-driven strategies for prevention of rheumatoid arthritis

In seropositive rheumatoid arthritis (RA), the onset of clinically apparent inflammatory arthritis (IA) is typically preceded by a prolonged period of autoimmunity manifest by the presence of circulating autoantibodies that can include antibodies to citrullinated protein antigens (ACPA) and rheumatoid factor (RF). This period prior to clinical IA can be designated preclinical RA in those individuals who have progressed to a clinical diagnosis of RA, and an 'at-risk' status in those who have not developed IA but exhibit predictive biomarkers of future clinical RA. With the goal of developing RA prevention strategies, studies have characterized immune phenotypes of preclinical RA/at-risk states. From these studies, a model has emerged wherein mucosal inflammation and dysbiosis may lead first to local autoantibody production that should normally be transient, but instead is followed by systemic spread of the autoimmunity as manifest by serum autoantibody elevations, and ultimately drives the development of clinically identified joint inflammation. This model can be envisioned as the progression of disease development through serial 'checkpoints' that in principle should constrain or resolve autoimmunity; however, instead the checkpoints 'fail' and clinical RA develops. Herein we review the immune processes that are likely to be present at each step and the potential therapeutic strategies that could be envisioned to delay, diminish, halt or even reverse the progression to clinical RA. Notably, these prevention strategies could utilize existing therapies approved for clinical RA, therapies approved for other diseases that target relevant pathways in the preclinical/at-risk state, or approaches that target novel pathways.

Extracellular histones aggravate autoimmune arthritis by lytic cell death

Although recent studies have demonstrated a proinflammatory effect of extracellular histones in sepsis via endothelial cytotoxicity, little is known about their contribution to autoimmune arthritis. Therefore, we investigated the role of extracellular histones in autoimmune arthritis and their cytotoxic effect on synoviocytes and macrophages. We measured histones in the synovial fluid of patients with rheumatoid arthritis (RA) and evaluated arthritis severity in a serum-transfer arthritis (STA) mouse model with intraperitoneal histone injection. Histone-induced cytotoxicity was measured using SYTOX green staining in the synoviocyte cell line MH7A and macrophages differentiated from the monocytic cell line THP-1, and the production of damage-associated molecular patterns (DAMPs) was measured by HMGB1 and ATP. Furthermore, we performed RNA-seq analysis of THP-1 cells stimulated with H2B-α1 peptide or with its citrullinated form. The levels of histones were elevated in RA synovial fluid, and histones aggravated arthritis in the STA model. Histones induced cytotoxicity and DAMP production in synoviocytes and macrophages. Chondroitin sulfate reduced histone-induced cytotoxicity, while lipopolysaccharides aggravated cytotoxicity. Moreover, the cytotoxicity decreased when the arginines in H2B-α1 were replaced with citrullines, which demonstrated its electrostatic nature. In transcriptome analysis, H2B-α1 changed the gene expression pattern of THP-1 cells involving chemokines, interleukin-1, -4, -10, -13, and toll-like receptor (TLR) signaling pathways. Extracellular histones were increased in RA synovial fluid and aggravated synovitis in STA. They induced lytic cell death through electrostatic interaction with synoviocytes and macrophages, leading to the secretion of DAMPs. These findings suggest that histones play a central role in autoimmune arthritis.

Mobilization of innate and adaptive antitumor immune responses by the RNP-targeting antibody ATRC-101

Immunotherapy approaches focusing on T cells have provided breakthroughs in treating solid tumors. However, there remains an opportunity to drive anticancer immune responses via other cell types, particularly myeloid cells. ATRC-101 was identified via a target-agnostic process evaluating antibodies produced by the plasmablast population of B cells in a patient with non-small cell lung cancer experiencing an antitumor immune response during treatment with checkpoint inhibitor therapy. Here, we describe the target, antitumor activity in preclinical models, and data supporting a mechanism of action of ATRC-101. Immunohistochemistry studies demonstrated tumor-selective binding of ATRC-101 to multiple nonautologous tumor tissues. In biochemical analyses, ATRC-101 appears to target an extracellular, tumor-specific ribonucleoprotein (RNP) complex. In syngeneic murine models, ATRC-101 demonstrated robust antitumor activity and evidence of immune memory following rechallenge of cured mice with fresh tumor cells. ATRC-101 increased the relative abundance of conventional dendritic cell (cDC) type 1 cells in the blood within 24 h of dosing, increased CD8+ T cells and natural killer cells in blood and tumor over time, decreased cDC type 2 cells in the blood, and decreased monocytic myeloid-derived suppressor cells in the tumor. Cellular stress, including that induced by chemotherapy, increased the amount of ATRC-101 target in tumor cells, and ATRC-101 combined with doxorubicin enhanced efficacy compared with either agent alone. Taken together, these data demonstrate that ATRC-101 drives tumor destruction in preclinical models by targeting a tumor-specific RNP complex leading to activation of innate and adaptive immune responses.

The monocyte cell surface as a novel site of autoantigen generation in Rheumatoid Arthritis

Citrullination is recognized as a key pathogenic process in rheumatoid arthritis (RA), as evidenced by the formation of anti-citrullinated protein antibodies (APCAs) in the majority of patients; however, the mechanisms that result in citrullinated autoantigen generation are not fully understood. Although the citrullinating enzyme peptidylarginine deiminase IV (PAD4) is predominantly expressed by neutrophils and monocytes, the contribution of monocytes to the citrullinated autoantigen pool has been underexplored. In this study, we utilized multiple complementary methods including flow cytometry, immunofluorescence, and transmission electron microscopy, which revealed a predominantly extranuclear localization of PAD4 in monocytes with a fraction present on the cell surface. Surface PAD4 was enzymatically active and citrullinated both extracellular fibrinogen and endogenous surface proteins in a calcium dose–dependent manner. In addition, human monoclonal ACPAs cloned from patients with RA recognized fibrinogen citrullinated by monocyte-surface PAD4. Mass spectrometry analysis of citrullinated proteins from the cell surface fraction revealed CD11b to be a novel PAD4 substrate. Citrullinated CD11b was recognized by autoantibodies in 60% of ACPA+ RA patients compared to 6% of healthy controls (p=0.0021) and 0% of ACPA− RA patients (p≤0.001). Taken together, our study demonstrates that PAD4 is expressed on the surface of monocytes in an enzymatically active state that renders the monocyte surface a novel site of citrullinated autoantigen generation in RA.

Supported by funds received from Bristol-Myers Squibb. 

Characterization of pathological IgE-mediated mast cell activation in Lyme disease

Lyme disease, caused by the bacteria Borrelia burgdorferi, is the most common and rapidly growing vector-borne infectious disease in the United States and Europe. High variability in disease burden among Lyme patients suggests that individual immune responses may be key drivers of clinical presentation and patient outcomes. Use of high resolution flow-based immunosorbent profiling revealed that a subset of Lyme patients with persistent symptoms were producing high concentrations of IgE specific to B. burgdorferi. Comparing C57B/6 mice, which are tolerant to B. burgdorferi, and C3H/HeJ mice, which are susceptible to disease, we find high levels of IgE specific for B. burgdorferi in C3H/HeJ but not C57B/6 mice. Furthermore, IgE was found to target Borrelia peptidoglycan in both acute and chronic infection models. Histologic analysis of mouse Lyme arthritic ankle tissue showed mast cells, which release highly immunogenic effectors upon activation by bound IgE, degranulating at significantly higher rates compared to uninfected controls. Forced mast cell degranulation exacerbated Lyme arthritis in infected mice. This data suggests that a subset of Lyme patients with persistent symptoms may have developed an allergic response to conserved bacterial antigens from a B. burgdorferi infection, as opposed to an autoimmune type response. Inclusion of IgE reactivity in diagnostic testing and examination of pathological immune responses to bacterial antigens could assist clinicians in patient care and effective treatments.

Research reported in this publication was supported by the Fairbairn family foundation; Bay Area Lyme Foundation; the Younger family foundation; the Robert J. Kleberg, Jr., and Helen C. Kleberg Foundation; the Virginia and D. K. Ludwig Fund for Cancer Research; M.C.T. was supported by Stanford Immunology training grant 5T32AI007290, and the NIH NRSA 1 F32 AI124558-01 award. L.B.T.D. was supported by a Stanford Diversifying Academia Recruiting Excellence fellowship. S.D.G was supported by the California Institute for Regenerative Medicine Bridges 2.0 Training Program grant EDUC2-08397. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Human KIR+ CD8+ T cells target pathogenic T cells in Celiac disease and are active in autoimmune diseases and COVID-19

Previous reports show a small subset of CD8+ T cells expressing Ly49 proteins in mice can suppress autoimmunity in a model of demyelinating disease. Here we find a markedly increased frequency of CD8+ T cells expressing inhibitory Killer cell Immunoglobulin like Receptors (KIR), the human equivalent of the Ly49 family, in the blood and inflamed tissues of various human autoimmune diseases. Increased KIR+ CD8+ T cells in the gut also correlate with disease activity in Celiac disease (CeD) patients. Moreover, KIR+ CD8+ T cells can efficiently eliminate pathogenic gliadin-specific CD4+ T cells from CeD patients’ leukocytes in vitro. Together with gene expression data, this shows that these cells are the likely equivalent of the mouse Ly49+ CD8+ T cells. Furthermore, we observe elevated levels of KIR+ CD8+ T cells, but not CD4+ regulatory T cells, in COVID-19 and influenza-infected patients, and this correlates with disease severity and vasculitis in COVID-19. Single-cell RNA and parallelized TCR sequencing reveals that expanded KIR+ CD8+ T cells from these different diseases and healthy subjects display shared phenotypes and similar T cell receptor sequences. Selective ablation of the murine counterpart in virus-infected mice leads to exacerbated autoimmunity developed after infection. These results characterize a regulatory CD8+ T cell subset in humans which we hypothesize functions to control pathogenic cells in autoimmune and infectious diseases, with important implications for the cellular dynamics and possible therapeutic approaches to suppress unwanted autoimmunity.

Supported by National Institutes of Health U19-AI057229 Howard Hughes Medical Institute Stanford Diabetes Research Center (P30DK116074)

KIR+CD8+ T cells suppress pathogenic T cells and are active in autoimmune diseases and COVID-19

In this work, we find that CD8+ T cells expressing inhibitory killer cell immunoglobulin-like receptors (KIRs) are the human equivalent of Ly49+CD8+ regulatory T cells in mice and are increased in the blood and inflamed tissues of patients with a variety of autoimmune diseases. Moreover, these CD8+ T cells efficiently eliminated pathogenic gliadin-specific CD4+ T cells from the leukocytes of celiac disease patients in vitro. We also find elevated levels of KIR+CD8+ T cells, but not CD4+ regulatory T cells, in COVID-19 patients, correlating with disease severity and vasculitis. Selective ablation of Ly49+CD8+ T cells in virus-infected mice led to autoimmunity after infection. Our results indicate that in both species, these regulatory CD8+ T cells act specifically to suppress pathogenic T cells in autoimmune and infectious diseases.

Limited Neutralization of Omicron by Antibodies from the BNT162b2 Vaccination against SARS-CoV-2

Since early December 2021, the omicron variant has posed additional challenges to the world-wide management of the SARS-CoV-2 pandemic. Immune evasion is a key factor for its increased transmissibility. While serological studies have measured levels of neutralizing antibodies in response to vaccines, our understanding of the humoral immune response to omicron on a single-antibody level is limited. Here, we characterize a set of BNT162b2 vaccine-derived antibodies for neutralization of omicron pseudovirus. We show that approximately 50% of neutralizing anti-RBD antibodies cross-neutralize omicron, albeit with lower potency than the original Wuhan-Hu1 strain. All investigated neutralizing anti-S2 antibodies cross-neutralize omicron, however all of them are less potent than anti-RBD antibodies. While additional booster immunizations of the current vaccine generate increased antibody levels and better protection, we anticipate that the second generation of vaccines will yield more high-affinity antibodies against omicron.

Differential Changes in ACPA Fine Specificity and Gene Expression in a Randomized Trial of Abatacept and Adalimumab in Rheumatoid Arthritis

INTRODUCTION

The biologics abatacept and adalimumab have different mechanisms of action (MoAs). We analyzed data from patients with rheumatoid arthritis treated in AMPLE (NCT00929864) to explore the pharmacodynamic effects of abatacept or adalimumab on anti-citrullinated protein antibodies (ACPAs) and gene expression.

METHODS

AMPLE was a phase IIIb, 2-year, randomized, head-to-head trial of abatacept versus adalimumab. Post hoc analyses of baseline anti-cyclic citrullinated peptide-2 (anti-CCP2, an ACPA surrogate) positive (+) status and ACPA fine-specificity profiles over time, as well as transcriptional profiling (peripheral whole blood), were performed.

RESULTS

Of 646 patients treated (abatacept, n = 318; adalimumab, n = 328), ACPA and gene expression data were available from 508 and 566 patients, respectively. In anti-CCP2+ patients (n = 388), baseline fine specificities for most ACPAs were highly correlated; over 2 years, levels decreased with abatacept but not adalimumab. By year 2, expression of genes associated with T cell co-stimulation and antibody production was lower for abatacept versus adalimumab; expression of genes associated with proinflammatory signaling was lower for adalimumab versus abatacept. Treatment modulated the expression of T- and B-cell gene signatures, with differences in CD8+ T cells, activated T cells, plasma cells, B cells, natural killer cells (all lower with abatacept versus adalimumab), and polymorphonuclear leukocytes (higher with abatacept versus adalimumab).

CONCLUSIONS

In AMPLE, despite similar clinical outcomes, data showed that pharmacodynamic/genetic changes after 2 years of abatacept or adalimumab were consistent with drug MoAs. Further assessment of the relationship between such changes and clinical outcomes, including prediction of response, is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT00929864.

Clonally expanded B cells in multiple sclerosis bind EBV EBNA1 and GlialCAM

Multiple sclerosis (MS) is a heterogenous autoimmune disease in which autoreactive lymphocytes attack the myelin sheath of the central nervous system. B lymphocytes in the cerebrospinal fluid (CSF) of patients with MS contribute to inflammation and secrete oligoclonal immunoglobulins^1,2. Epstein-Barr virus (EBV) infection has been epidemiologically linked to MS, but its pathological role remains unclear³. Here we demonstrate high-affinity molecular mimicry between the EBV transcription factor EBV nuclear antigen 1 (EBNA1) and the central nervous system protein glial cell adhesion molecule (GlialCAM) and provide structural and in vivo functional evidence for its relevance. A cross-reactive CSF-derived antibody was initially identified by single-cell sequencing of the paired-chain B cell repertoire of MS blood and CSF, followed by protein microarray-based testing of recombinantly expressed CSF-derived antibodies against MS-associated viruses. Sequence analysis, affinity measurements and the crystal structure of the EBNA1-peptide epitope in complex with the autoreactive Fab fragment enabled tracking of the development of the naive EBNA1-restricted antibody to a mature EBNA1-GlialCAM cross-reactive antibody. Molecular mimicry is facilitated by a post-translational modification of GlialCAM. EBNA1 immunization exacerbates disease in a mouse model of MS, and anti-EBNA1 and anti-GlialCAM antibodies are prevalent in patients with MS. Our results provide a mechanistic link for the association between MS and EBV and could guide the development of new MS therapies.

Abstract P2-01-11: Single-cell sequencing of the blood T cell repertoire before and after trastuzumab treatment in early stage HER2+ breast cancer

Background: Human epidermal growth factor receptor 2 (HER2) positivity in breast cancer portends an aggressive tumor behavior and poor prognosis and is associated with a positive response to trastuzumab treatment. Prior immunohistochemistry and RNA sequencing of breast tumor tissues suggest that trastuzumab may recruit and activate anti-tumor T cells. Tumor infiltrating lymphocytes have been associated with improved response in patients with HER2+ early breast cancer treated with neoadjuvant trastuzumab plus chemotherapy. However, these cells have not previously been characterized at the single cell level in tumor tissue or in the periphery. Assessing the T cell component in the peripheral blood via single-cell sequencing enables high sensitivity detection of rare cells, may identify T cell antigen receptors (TCR) involved in the anti-tumor response, and could lead to a non-invasive means of monitoring trastuzumab-mediated immune activity. Here we perform single cell sequencing of the blood T cell repertoire in breast cancer patients pre- and post-trastuzumab treatment. Methods: To characterize T cell response in trastuzumab plus chemotherapy treated patients, we profiled peripheral CD3+ T cells using 10x Genomics VDJ single-cell sequencing in paired samples from five patients with HER2+ breast cancer. Patients had stage IIA (n=2), stage IIIC (n=2) or stage IV (n=1) breast cancer and were treated with preoperative docetaxel, carboplatin, trastuzumab, pertuzumab (TCHP). Two patients had a pathological complete response (pCR), and three patients had partial clinical response with residual disease at surgery. Peripheral blood mononuclear cells (PMBCs) were collected at a C1D1 pre-treatment and day 1 of cycles 3, 4, or 5. Results: Eleven T cell subpopulations, including naïve and memory CD4+ and CD8+ T cells, activated CD4+ and CD8+ T effector cells, activated CD4+ T regulatory cells, were characterized in the five patients’ peripheral blood based on their transcriptional profiles. T cell subpopulation distribution and clonal expansion profiles were similar in pre- and post- treatment samples in all five donors. Large T cell clonal expansions were detected in the peripheral blood of the two patients who had a pCR, but were not detected in the three patients who had residual disease at surgery. The patients who had a pCR exhibited large expansions in activated CD8+ terminal effector memory/effector memory (TEM/EM) cells followed by expansions in activated CD4+ TEM/EM cells. A minor increasing trend in activated CD4+ Treg cells was observed across all patients upon treatment with TCHP. Conclusions: Single-cell sequencing enables high-resolution characterization of immune cell subsets and represents a promising approach to assess the immune response to trastuzumab and other cancer therapeutics. In this study, single-cell sequencing of peripheral CD3+ T cells identified clonal expansions in activated CD8+ and CD4+ T cells in HER2+ breast cancer patients who had a pCR with preoperative TCHP treatment. These data are consistent with the model that T cells play a key role in trastuzumab-mediated tumor control, and warrant further investigation in a larger sample population.

Citation Format: John Vivian, Kimberly Walter, Elliott Drabek, Nicole Haaser, Maren K. Levin, Esther San Roman Rodriguez, Kendra Peck, Ngan Nguyen, Carl Millward, Jonathan Benjamin, William H. Robinson, Joyce A. O'Shaughnessy. Single-cell sequencing of the blood T cell repertoire before and after trastuzumab treatment in early stage HER2+ breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-01-11.

Epstein-Barr virus and multiple sclerosis

[Figure: see text].

Neutralizing anti-IL-1 receptor antagonist autoantibodies induce inflammatory and fibrotic mediators in IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD) is a fibroinflammatory condition involving loss of B-cell tolerance and production of autoantibodies. However, the relevant targets and role of these aberrant humoral immune responses are not defined.

OBJECTIVE

Our aim was to identify novel autoantibodies and autoantigen targets that promote pathogenic responses in IgG4-RD.

METHODS

We sequenced plasmablast antibody repertoires in patients with IgG4-RD. Representative mAbs were expressed and their specificities characterized by using cytokine microarrays. The role of anti-IL-1 receptor antagonist (IL-1RA) autoantibodies was investigated by using in vitro assays.

RESULTS

We identified strong reactivity against human IL-1RA by using a clonally expanded plasmablast-derived mAb from a patient with IgG4-RD. Plasma from patients with IgG4-RD exhibited elevated levels of reactivity against IL-1RA compared with plasma from the controls and neutralized IL-1RA activity, resulting in inflammatory and fibrotic mediator production in vitro. IL-1RA was detected in lesional tissues from patients with IgG4-RD. Patients with anti-IL-1RA autoantibodies of the IgG4 subclass had greater numbers of organs affected than did those without anti-IL-1RA autoantibodies. Peptide analyses identified IL-1RA epitopes targeted by anti-IL-1RA antibodies at sites near the IL-1RA/IL-1R interface. Serum from patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) also had elevated levels of anti-IL-1RA autoantibodies compared with those of the controls.

CONCLUSION

A subset of patients with IgG4-RD have anti-IL-1RA autoantibodies, which promote proinflammatory and profibrotic meditator production via IL-1RA neutralization. These findings support a novel immunologic mechanism underlying the pathogenesis of IgG4-RD. Anti-IL-1RA autoantibodies are also present in a subset of patients with SLE and RA, suggesting a potential common pathway in multiple autoimmune diseases.

Human KIR + CD8 + T cells target pathogenic T cells in Celiac disease and are active in autoimmune diseases and COVID-19

Previous reports show that Ly49 ⁺ CD8 ⁺ T cells can suppress autoimmunity in mouse models of autoimmune diseases. Here we find a markedly increased frequency of CD8 ⁺ T cells expressing inhibitory Killer cell Immunoglobulin like Receptors (KIR), the human equivalent of the Ly49 family, in the blood and inflamed tissues of various autoimmune diseases. Moreover, KIR ⁺ CD8 ⁺ T cells can efficiently eliminate pathogenic gliadin-specific CD4 ⁺ T cells from Celiac disease (CeD) patients' leukocytes in vitro . Furthermore, we observe elevated levels of KIR ⁺ CD8 ⁺ T cells, but not CD4 ⁺ regulatory T cells, in COVID-19 and influenza-infected patients, and this correlates with disease severity and vasculitis in COVID-19. Expanded KIR ⁺ CD8 ⁺ T cells from these different diseases display shared phenotypes and similar T cell receptor sequences. These results characterize a regulatory CD8 ⁺ T cell subset in humans, broadly active in both autoimmune and infectious diseases, which we hypothesize functions to control self-reactive or otherwise pathogenic T cells.

ONE-SENTENCE SUMMARY

Here we identified KIR ⁺ CD8 ⁺ T cells as a regulatory CD8 ⁺ T cell subset in humans that suppresses self-reactive or otherwise pathogenic CD4 ⁺ T cells.

Antibody Responses to Epstein-Barr Virus in the Preclinical Period of Rheumatoid Arthritis Suggest the Presence of Increased Viral Reactivation Cycles

OBJECTIVE

Patients with established rheumatoid arthritis (RA) demonstrate altered immune responses to Epstein-Barr virus (EBV), but the presence and role(s) of EBV have not been fully explored in the preclinical period. We hypothesized that EBV infection, as evidenced by an altered anti-EBV antibody response, could either play an important role in driving the development or be a result of expanded RA-related autoimmunity.

METHODS

83 subjects with RA based on 1987 ACR criteria and 83 matched controls were evaluated. Subject and matched control sera from the pre and post- RA diagnosis periods were tested for 5 anti-EBV antibodies (EBNA-1-IgG, VCA-IgG, EA-IgG, VCA-IgA, and EA-IgA), 7 RA-related autoantibodies (RF-neph, RF-IgA, RF-IgM, RF-IgG, CCP2, CCP3, CCP3.1), 22 cytokine/chemokine, 36 individual APCAs, and CMV-IgG antibodies. Random forest classification, mixed and joint mixed modelling were used to determine differences in anti-EBV antibodies between RA cases and controls.

RESULTS

Random Forest analysis identified preclinical EBV antibodies that differentiate RA subjects from controls. Specifically, EA-IgG antibody levels are higher in RA cases (0.82 ± 0.72) compared to controls (0.49 ± 0.28). Elevations in EA-IgG levels significantly correlated with increasing RF-IgM levels in future RA cases (p = 0.007) but not in controls (p = 0.150). CMV-IgG antibody levels did not differ between groups.

CONCLUSION

Subjects who eventually develop classified RA demonstrate elevated EA-IgG antibody levels in the preclinical period, which suggests the presence of increased EBV re-activation cycles. A combination of RF and EBV reactivation may play an important role in the development of RA.