CD20+inflammatory T-cells are present in blood and brain of multiple sclerosis patients and can be selectively targeted for apoptotic elimination

Evaluating the Therapeutic Potential of Ublituximab in the Treatment of MS: Design, Development and Place in Therapy

B cells are critical to the pathogenesis of multiple sclerosis (MS), an autoimmune disease of the central nervous system. B cell depletion using anti-CD20 monoclonal antibodies (mAbs) has proven to be an extremely successful treatment strategy, with profound suppression of both clinical and radiological evidence of focal inflammatory disease. Several anti-CD20 mAbs are now licensed for use in MS, with ublituximab being the latest to gain regulatory approval. The unique properties of each of the anti-CD20 mAb may result in nuanced differences in timing, duration and depth of B cell depletion, with the potential for such differences to have a clinical relevance to both drug efficacy and adverse effects. In this review, we summarize the design, development, and current place in MS therapy for ublituximab.

Effect of siponimod on lymphocyte subsets in active secondary progressive multiple sclerosis and clinical implications

BACKGROUND

Circulating immune cells play a pathogenic role in multiple sclerosis (MS). However, the role of specific lymphocyte subpopulations is not unveiled yet, especially in progressive stages. We aimed to investigate lymphocyte changes during siponimod treatment in active secondary progressive MS (aSPMS) and their associations with clinical outcomes.

METHODS

We enrolled 46 aSPMS patients starting on siponimod treatment with at least 6 months of follow-up and two visits within the scheduled timeframes and 14 sex- and age-matched healthy controls (HCs). Clinical and laboratory data were collected retrospectively at baseline, 3rd, 6th, 12th, and 24th month for MS patients, and at baseline for HCs.

RESULTS

At baseline SPMS patients presented with increased naïve regulatory T lymphocytes (p = 0.02) vs. HCs. Over time, SPMS patients showed decreased T CD4+ (coeff. range = -24/-17, 95% CI range = -31.60 to -10.40), B lymphocyte (coeff. range = -3.77/-2.54, 95% CI range = -6.02 to -0.35), memory regulatory B cells (coeff. range = -0.78/-0.57, 95% CI range = -1.24 to -0.17) and CD4/CD8 ratio (coeff. range = -4.44/-0.67, 95% CI range = -1.61 to -0.17) from month 3 thereafter vs. baseline, and reduced CD3+CD20+ lymphocytes from month 12 thereafter (coeff. range = -0.32/-0.24, 95% CI range = -0.59 to -0.03). Patients not experiencing disability progression while on siponimod treatment showed B lymphocyte reduction from month 3 (coeff. range = -4.23/-2.32, 95% CI range = -7.53 to -0.15) and CD3+CD20+ lymphocyte reduction from month 12 (coeff. range = -0.32/-0.24, 95% CI range = -0.59 to -0.03) vs. patients experiencing progression.

CONCLUSIONS

Patients treated with siponimod showed a T and B lymphocyte reduction, especially CD4+, CD3+CD20+ and naïve regulatory T cells and memory regulatory B cells. Disability progression while on siponimod treatment was associated with a less pronounced effect on B and CD3+CD20+ lymphocytes.

CD20 + T lymphocytes in isolated Hashimoto's thyroiditis and type 3 autoimmune polyendocrine syndrome: a pilot study

BACKGROUND

CD20+ T cells represent up to 5% of circulating T lymphocytes. These cells have been shown to produce higher levels of IL-17A and IFN-γ than those of CD20- T lymphocytes. Some reports described the role of CD20+ T cells in autoimmune disorders such as multiple sclerosis and rheumatoid arthritis possibly due to their ability to produce these inflammatory cytokines. This study is aimed at describing the behavior of CD20+ T lymphocytes in the most frequent autoimmune disorder, i.e., Hashimoto's thyroiditis (HT), presenting isolated or associated to further autoaggressive disorders in a frame of poly-autoimmunity.

METHODS

The study group encompasses 65 HT patients: 23 presenting in isolated form (IT) and 42 with an associated non-endocrine autoimmune disorder [16 with chronic atrophic gastritis (CAG), 15 with nonsegmental vitiligo (VIT), and 11 with celiac disease (CD)]. Twenty healthy donors act as control group (HD). Chronic use of interfering drugs, severe or chronic disorders, and pregnancy and lactation were used as exclusion criteria. Whole blood samples (100 µl) were stained with fluorescent-labeled antibodies (anti-CD45, anti-CD3, anti-CD19, anti-CD16, anti-CD56, anti-CD4, anti-CD8, anti-CD20). Red blood cells were then lysed by adding 1 ml of hypotonic buffer, and samples were acquired on a Flow Cytometer.

RESULTS

CD3+CD8+CD20+ T lymphocytes' percentages, were significantly higher in the whole group of autoimmune patients compared to healthy donors (p = 0.0145). Dividing HT patients based on the type of presentation of autoimmune thyroiditis, CAG group showed the highest percentage of these cells as compared to HD and CD (p = 0.0058). IT patients showed higher percentages of CD3+ CD8+CD20+ cells than those of HD patients although not reaching statistical significance. However, dividing IT group based on thyroid function, hypothyroid patients showed higher CD8+CD20+ cell percentages than those of HD and euthyroid patients (p = 0.0111). Moreover, in IT patients, these cells were negatively correlated with FT4 levels (p = 0.0171; r = -0.4921).

CONCLUSIONS

These preliminary findings indicate that CD8+CD20+ T cells are activated in patients with autoimmune thyroiditis and may behave differently according to the presence of poly-autoimmunity and hypothyroidism.

CD20+ T cells in monoclonal B cell lymphocytosis and chronic lymphocytic leukemia: frequency, phenotype and association with disease progression

Introduction

In monoclonal B cell lymphocytosis (MBL) and chronic lymphocytic leukemia (CLL), the expansion of malignant B cells disrupts the normal homeostasis and interactions between B cells and T cells, leading to immune dysregulation. CD20+ T cells are a subpopulation of T cells that appear to be involved in autoimmune diseases and cancer.

Methods

Here, we quantified and phenotypically characterized CD20+ T cells from MBL subjects and CLL patients using flow cytometry and correlated our findings with the B-cell receptor mutational status and other features of the disease.

Results and discussion

CD20+ T cells were more represented within the CD8+ T cell compartment and they showed a predominant memory Tc1 phenotype. CD20+ T cells were less represented in MBL and CLL patients vs healthy controls, particularly among those with unmutated IGVH gene. The expansion of malignant B cells was accompanied by phenotypic and functional changes in CD20+ T cells, including an increase in follicular helper CD4+ CD20+ T cells and CD20+ Tc1 cells, in addition to the expansion of the TCR Vβ 5.1 in CD4+ CD20+ T cells in CLL.

Ocrelizumab associates with reduced cerebrospinal fluid B and CD20dim CD4+ T cells in primary progressive multiple sclerosis

The anti-CD20 monoclonal antibody ocrelizumab reduces disability progression in primary progressive multiple sclerosis. CD20 is a prototypical B-cell marker; however, subpopulations of CD4+ and CD8+ T cells in peripheral blood and cerebrospinal fluid also express low levels of CD20 (CD20dim). Therefore, direct targeting and depletion of these CD20dim T-cell subpopulations may contribute to the therapeutic effect of ocrelizumab. The aim of this observational cohort study was to compare CD20+ B-cell and CD20dim T-cell distributions between peripheral blood and cerebrospinal fluid of ocrelizumab-treated or ocrelizumab-untreated people with primary progressive multiple sclerosis. Ocrelizumab treatment was associated with depletion of circulating B cells and CD20dim CD4+ and CD20dim CD8+ T cells (P < 0.0001, P = 0.0016 and P = 0.0008, respectively) but, in cerebrospinal fluid, only with lower proportions of B cells and CD20dim memory CD4+ T cells (P < 0.0001 and P = 0.0043, respectively). The proportional prevalence of cerebrospinal fluid CD20dim memory CD8+ T cells was not significantly reduced (P = 0.1333). Only in cerebrospinal fluid, the proportions of CD20dim cells within CD4+ and not CD8+ T cells positive for CCR5, CCR6 and CXCR3 were reduced in ocrelizumab-treated participants. The proportion of CD20dim CD4+ T cells and abundance of CD4+ relative to CD8+ T cells in cerebrospinal fluid correlated positively with age (R = 0.6799, P = 0.0150) and Age-Related Multiple Sclerosis Severity score (R = 0.8087, P = 0.0014), respectively. We conclude that, in contrast to cerebrospinal fluid CD20dim CD8+ T cells, B cells and CD20dim CD4+ T cells are reduced in cerebrospinal fluid of people with primary progressive multiple sclerosis with an ocrelizumab-associated depletion of circulating B cells and CD20dim T cells. Therefore, these cells are likely to contribute to the therapeutic effects of ocrelizumab in people with primary progressive multiple sclerosis.

Lymph-Node-Based CD3+ CD20+ Cells Emerge from Membrane Exchange between T Follicular Helper Cells and B Cells and Increase Their Frequency following Simian Immunodeficiency Virus Infection

CD4+ T follicular helper (TFH) cells are key targets for human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) replication and contribute to the virus reservoir under antiretroviral therapy (ART). Here, we describe a novel CD3+ CD20+ double-positive (DP) lymphocyte subset, resident in secondary lymphoid organs of humans and rhesus macaques (RMs), that appear predominantly after membrane exchange between TFH and B cells. DP lymphocytes are enriched in cells displaying a TFH phenotype (CD4+ PD1hi CXCR5hi), function (interleukin 21 positive [IL-21+]), and gene expression profile. Importantly, expression of CD40L upon brief in vitro mitogen stimulation identifies, by specific gene-expression signatures, DP cells of TFH-cell origin versus those of B-cell origin. Analysis of 56 RMs showed that DP cells (i) significantly increase following SIV infection, (ii) are reduced after 12 months of ART in comparison to pre-ART levels, and (iii) expand to a significantly higher frequency following ART interruption. Quantification of total SIV-gag DNA on sorted DP cells from chronically infected RMs showed that these cells are susceptible to SIV infection. These data reinforce earlier observations that CD20+ T cells are infected and expanded by HIV infection, while suggesting that these cells phenotypically overlap activated CD4+ TFH cells that acquire CD20 expression via trogocytosis and can be targeted as part of therapeutic strategies aimed at HIV remission. IMPORTANCE The HIV reservoir is largely composed of latently infected memory CD4+ T cells that persist during antiretroviral therapy and constitute a major barrier toward HIV eradication. In particular, CD4+ T follicular helper cells have been demonstrated as key targets for viral replication and persistence under ART. In lymph nodes from HIV-infected humans and SIV-infected rhesus macaques, we show that CD3+ CD20+ lymphocytes emerge after membrane exchange between T cells and B cells and are enriched in phenotypic, functional, and gene expression profiles found in T follicular helper cells. Furthermore, in SIV-infected rhesus macaques, these cells expand following experimental infection and after interruption of ART and harbor SIV DNA at levels similar to those found in CD4+ T cells; thus, CD3+ CD20+ lymphocytes are susceptible to SIV infection and can contribute to SIV persistence.

Aberrant pro-inflammatory responses of CD20+ T cells in experimental arthritis

CD20+ T cells comprise a highly inflammatory subset implicated in autoimmunity, including rheumatoid arthritis (RA). We sought to characterize the CD20+ T cell subset in the murine collagen-induced arthritis (CIA) model of RA and investigate the phenotype and functional relevance of CD3+CD20+ T cells in the lymph nodes and arthritic joints using flow cytometry and immunohistochemistry. We demonstrate that CD3+CD4+CD20+ and CD3+CD8+CD20+ T cells are expanded in the draining lymph nodes of CIA mice, produce increased levels of pro-inflammatory cytokines and are less susceptible to regulation by regulatory T cells. Notably, CD3+CD4+CD20+ and CD3+CD8+CD20+ T cells are enriched with CXCR5+PD-1+ T follicular helper cells and CXCR5-PD-1+ peripheral T helper cells, subsets of T cells implicated in promoting B-cell responses and antibody production within pathologically inflamed non-lymphoid tissues in RA. Our findings suggest CD20+ T cells are associated with inflammatory responses and may exacerbate pathology by promoting inflammatory B-cell responses.

Immunomodulatory effects of ocrelizumab and candidate biomarkers for monitoring treatment response in multiple sclerosis

Ocrelizumab is a humanized monoclonal antibody designed to bind to the CD20 molecule, resulting in a rapid depletion of B-cells; however, it has been shown that lymphocyte subpopulations other than B-cells are affected by the drug. To review the effects of ocrelizumab on circulating lymphocytes and identify candidate biomarkers to predict and monitor treatment response. A literature search for the most relevant articles from 2006 to 2022 was conducted in PubMed and Scopus. The effect of ocrelizumab on the peripheral immune system goes beyond B-cells; it also depletes T CD20 + lymphocytes. Further, ocrelizumab reshapes the T-cell response toward a low inflammatory profile and induces an increase in T CD8 + regulatory cell percentage. A higher Body Mass Index and higher B-cell count at baseline have been associated with early B-cell reappearance. Serum neurofilament light chain reduction has been associated with treatment response. Ocrelizumab treatment exerts a broad immunomodulatory effect and may be tailored based on patients' clinical and biological profiles.

Ocrevus reduces TH40 cells, a biomarker of systemic inflammation, in relapsing multiple sclerosis (RMS) and in progressive multiple sclerosis (PMS)

Treating MS has been difficult. One successful drug is Ocrelizumab (anti-CD20), used for the chronic relapsing MS (RMS) and the progressive MS (PMS) forms. TH40 cells are pathogenic effector T cells that increase in percentage and numbers during chronic inflammation. Here we show that in the earliest MS course, clinically isolated syndrome (CIS), TH40 cells expand in number. In PMS TH40 cell numbers remain expanded demonstrating sustained chronic inflammation. In RMS TH40 cells were found in CSF and express CD20. Ocrelizumab reduced TH40 cells to healthy control levels in patients. During treatment inflammatory cytokine producing TH40 cells were decreased.

Antibody-mediated cell depletion therapies in multiple sclerosis

Development of disease-modifying therapies including monoclonal antibody (mAb)-based therapeutics for the treatment of multiple sclerosis (MS) has been extremely successful over the past decades. Most of the mAb-based therapies approved for MS deplete immune cell subsets and act through activation of cellular Fc-gamma receptors expressed by cytotoxic lymphocytes and phagocytes, resulting in antibody-dependent cellular cytotoxicity or by initiation of complement-mediated cytotoxicity. The therapeutic goal is to eliminate pathogenic immune cell components and to potentially foster the reconstitution of a new and healthy immune system. Ab-mediated immune cell depletion therapies include the CD52-targeting mAb alemtuzumab, CD20-specific therapeutics, and new Ab-based treatments which are currently being developed and tested in clinical trials. Here, we review recent developments in effector mechanisms and clinical applications of Ab-based cell depletion therapies, compare their immunological and clinical effects with the prototypic immune reconstitution treatment strategy, autologous hematopoietic stem cell transplantation, and discuss their potential to restore immunological tolerance and to achieve durable remission in people with MS.

CD20+ T cells: an emerging T cell subset in human pathology

Introduction

Although CD20 is classically a B cell marker, in the last three decades, dim expression has been noted on a subset of T cells as well that has been independently verified by a number of groups. Our understanding of these cells and their function is not well established.

Methods

A thorough review of original articles on CD20⁺T cells was undertaken of Pubmed by using combination of phrases including “CD20⁺”, “CD20-positive” and “T cells”. Articles in English were considered, and there was no time restriction.

Results

CD20⁺T cells express the standard T cell markers and, in comparison to CD20¯ T cells, appear to express greater inflammatory cytokines and markers of effector function. Although the ontogeny of these cells is still being established, the current theory is that CD20 may be acquired by trogocytosis from B cells. CD20⁺T cells may be found in healthy controls and in a wide range of pathologies including autoimmune diseases, haematological and non-haematological malignancies and human immunodeficiency virus (HIV) infections. One of the best studied diseases where these cells are found is multiple sclerosis (MS) where a number of therapeutic interventions, including anti-CD20 depletion, have been shown to effectively deplete these cells.

Conclusion

This review summarises the latest understanding of CD20⁺T cells, their presence in various diseases, their putative function and how they may be an ongoing target of CD20-depleting agents. Unfortunately, our understanding of these cells is still at its infancy and ongoing study in a wider range of pathologies is required.

CD20 positive CD8 T cells are a unique and transcriptionally-distinct subset of T cells with distinct transmigration properties

The presence of T cells that are dimly positive for the B cell marker CD20 is well-established in autoimmunity and correlates with disease severity in various diseases. Further, we previously identified that the level of CD20-positive T cells was three-fourfold elevated in ascites fluid of ovarian carcinoma patients, together suggesting a role in both autoimmunity and cancer. In this respect, treatment of autoimmune patients with the CD20-targeting antibody Rituximab has also been shown to target and deplete CD20-positive T cells, previously identified as IFN-gamma producing, low proliferative, CD8 cytotoxic T cells with an effector memory (EM) differentiation state. However, the exact phenotype and relevance of CD20-positive T cells remains unclear. Here, we set out to identify the transcriptomic profile of CD20-positive T cells using RNA sequencing. Further, to gain insight into potential functional properties of CD20 expression in T cells, CD20 was ectopically expressed on healthy human T cells and phenotypic, functional, migratory and adhesive properties were determined in vitro and in vivo. Together, these assays revealed a reduced transmigration and an enhanced adhesive profile combined with an enhanced activation status for CD20-positive T cells.

B cell depletion changes the immune cell profile in multiple sclerosis patients: One-year report

B cell depletion therapy has been shown to be beneficial in multiple sclerosis (MS). However, the mechanism by which B cell depletion mediates its beneficial effects in MS is still unclear. To better understand how B cell depletion may benefit patients with a disease previously thought to be primarily mediated by CD4 T cells, immune profiles were monitored in 48 patients in a phase II trial of ublituximab, a glycoengineered CD20 monoclonal antibody, at 18 time points over a year. As we previously described there was a significant shift in the percentages of T cells, NK cells, and myeloid cells following the initial dose of ublituximab, but this shift normalized within a week and these populations remained stable for the duration of the study. However, T cell subsets changed with an increase in the percentage of naïve CD4 and CD8 T cells and a decline in memory T cells. Importantly, the percentage of Th1 and CD4⁺GM-CSF⁺ T cells decreased, while the percentage of Tregs continued to increase over the year. Ublituximab not only depleted CD20⁺ B cells, but also CD20⁺ T cells. The favorable changes in the T cell subsets may contribute to the beneficial effects of B cell depletion therapy.

CD32+CD4+ T Cells Sharing B Cell Properties Increase With Simian Immunodeficiency Virus Replication in Lymphoid Tissues

CD4 T cell responses constitute an important component of adaptive immunity and are critical regulators of anti-microbial protection. CD4⁺ T cells expressing CD32a have been identified as a target for HIV. CD32a is an Fcγ receptor known to be expressed on myeloid cells, granulocytes, B cells and NK cells. Little is known about the biology of CD32⁺CD4⁺ T cells. Our goal was to understand the dynamics of CD32⁺CD4⁺ T cells in tissues. We analyzed these cells in the blood, lymph nodes, spleen, ileum, jejunum and liver of two nonhuman primate models frequently used in biomedical research: African green monkeys (AGM) and macaques. We studied them in healthy animals and during viral (SIV) infection. We performed phenotypic and transcriptomic analysis at different stages of infection. In addition, we compared CD32+CD4+ T cells in tissues with well-controlled (spleen) and not efficiently controlled (jejunum) SIV replication in AGM. The CD32⁺CD4⁺ T cells more frequently expressed markers associated with T cell activation and HIV infection (CCR5, PD-1, CXCR5, CXCR3) and had higher levels of actively transcribed SIV RNA than CD32^-CD4⁺T cells. Furthermore, CD32⁺CD4⁺ T cells from lymphoid tissues strongly expressed B-cell-related transcriptomic signatures, and displayed B cell markers at the cell surface, including immunoglobulins CD32+CD4+ T cells were rare in healthy animals and blood but increased strongly in tissues with ongoing viral replication. CD32⁺CD4⁺ T cell levels in tissues correlated with viremia. Our results suggest that the tissue environment induced by SIV replication drives the accumulation of these unusual cells with enhanced susceptibility to viral infection.

Effect of Ocrelizumab in Blood Leukocytes of Patients With Primary Progressive MS

OBJECTIVE

To analyze the changes induced by ocrelizumab in blood immune cells of patients with primary progressive MS (PPMS).

METHODS

In this multicenter prospective study including 53 patients with PPMS who initiated ocrelizumab treatment, we determined effector, memory, and regulatory cells by flow cytometry at baseline and after 6 months of therapy. Wilcoxon matched paired tests were used to assess differences between baseline and 6 months' results. p Values were corrected using the Bonferroni test.

RESULTS

Ocrelizumab reduced the numbers of naive and memory B cells (p < 0.0001) and those of B cells producing interleukin (IL)-6, IL-10, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNFα) (p < 0.0001 in all cases). By contrast, the proportions of plasmablasts and B cells producing GM-CSF and TNFα increased significantly, suggesting the need for treatment continuation. We also observed a decrease in CD20+ T-cell numbers (p < 0.0001) and percentages (p < 0.0001), and a clear remodeling of the T-cell compartment characterized by relative increases of the naive/effector ratios in CD4+ (p = 0.002) and CD8+ (p = 0.002) T cells and relative decreases of CD4+ (p = 0.03) and CD8+ (p = 0.004) T cells producing interferon-gamma. Total monocyte numbers increased (p = 0.002), but no changes were observed in those producing inflammatory cytokines. The immunologic variations were associated with a reduction of serum neurofilament light chain (sNfL) levels (p = 0.008). The reduction was observed in patients with Gd-enhanced lesions at baseline and in Gd- patients with baseline sNfL >10 pg/mL.

CONCLUSIONS

In PPMS, effector B-cell depletion changed T-cell response toward a low inflammatory profile, resulting in decreased sNfL levels.

Rituximab Induces Complete Remission of Proteinuria in a Patient With Minimal Change Disease and No Detectable B Cells

Minimal change disease (MCD) is a common cause of nephrotic syndrome. Treatment with steroids is usually effective, but frequent relapses are therapeutic challenges. The anti-CD20 antibody rituximab has shown promising results for treatment of steroid-sensitive nephrotic syndrome. Since predictive biomarkers for treatment efficacy and the accurate rituximab dosage for effective induction of remission are unknown, measurement of CD19+ B cells in blood is often used as marker of successful B cell depletion and treatment efficacy. A male patient with relapsing MCD was successfully treated with rituximab, but developed relapse of proteinuria 1 year later, although no B cells were detectable in his blood. B and T cell populations in the patient's blood were analyzed before and after treatment with rituximab using FACS analysis. Rituximab binding to B and T cells were measured using Alexa Fluor 647 conjugated rituximab. We identified a population of CD20+ CD19- cells in the patient's blood, which consisted mostly of CD20+ CD3+ T cells. Despite the absence of B cells in the blood, the patient was again treated with rituximab. He developed complete remission of proteinuria and depletion of CD20+ T cells. In a control patient with relapsing MCD initial treatment with rituximab led to depletion of both CD20+ B and T cells. Rituximab induces remission of proteinuria in patients with MCD even if circulating B cells are absent. CD20+ T cells may play a role in the pathogenesis of MCD and might be a promising treatment target in patients with MCD.

White matter lesions in multiple sclerosis are enriched for CD20dim CD8+ tissue-resident memory T cells

Brain CD8⁺ CD69⁺ tissue-resident memory T (T_RM ) cells comprise a CD20^dim subset, which is proportionally larger in CD103-negative T_RM cells. In multiple sclerosis (MS) lesions, CD20^dim T_RM -cell proportions are increased. CD20-expression is associated with higher levels of CXCR6, Ki-67, and granzyme B, supporting CD20^dim T_RM cells as a relevant subset in MS.

Adverse event profile differences between rituximab and ocrelizumab: Findings from the FDA Adverse Event Reporting Database

BACKGROUND

Rituximab and ocrelizumab are anti-CD20 monoclonal antibodies that have shown a marked reduction in multiple sclerosis (MS) inflammatory activity. However, their real-world safety profile has not been adequately compared.

OBJECTIVE

To investigate the adverse event (AE) profile of rituximab and ocrelizumab reported to the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

The FAERS database was filtered by indication (MS) and drug (rituximab or ocrelizumab). Disproportionality analyses including but not limited to reporting odds ratio (ROR) were conducted to identify drug-AE associations. A signal was detected if the lower limit of the 95% confidence interval of ROR (ROR₀₂₅) exceeded 1.

RESULTS

There were 623 and 7948 reports for rituximab and ocrelizumab, respectively. The most frequent AEs with rituximab and ocrelizumab were infusion-related reaction (4.82%) and urinary tract infection (10.52%), respectively. The strongest drug-AE association for rituximab and ocrelizumab were ear pruritus (ROR₀₂₅: 47.53) and oral herpes (ROR₀₂₅: 38.99), respectively. Ocrelizumab was associated with an almost two times higher frequency of infections than rituximab (21.93% vs 11.05%, respectively).

CONCLUSION

This study revealed differences in reporting AEs between rituximab and ocrelizumab. Infections were reported more frequently with ocrelizumab. Although speculative, a potentially different or more extensive B-cell depletion by ocrelizumab might explain these findings. Additional pharmacovigilance studies need to be performed to better characterize differences in the AE profile in B-cell-depleting therapies.

The role of TH17 cells in multiple sclerosis: Therapeutic implications

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) where immunopathology is thought to be mediated by myelin-reactive CD4⁺ T helper (TH) cells. The TH cells most commonly implicated in the pathogenesis of the disease are of TH1 and TH17 lineage, which are defined by the production of interferon-γ and interleukin-17, respectively. Moreover, there is emerging evidence for the involvement of TH17.1 cells, which share the hallmarks of TH1 and TH17 subsets. In this review, we summarise current knowledge about the potential role of TH17 subsets in the initiation and progression of the disease and put a focus on their response to approved immunomodulatory MS drugs. In this regard, TH17 cells are abundant in peripheral blood, cerebrospinal fluid and brain lesions of MS patients, and their counts and inflammatory mediators are further increased during relapses. Fingolimod and alemtuzumab induce a paramount decrease in central memory T cells, which harbour the majority of peripheral TH17 cells, while the efficacy of natalizumab, dimethyl fumarate and importantly hematopoietic stem cell therapy correlates with TH17.1 cell inhibition. Interestingly, also CD20 antibodies target highly inflammatory TH cells and hamper TH17 differentiation by IL-6 reductions. Moreover, recovery rates of TH cells best correlate with long-term efficacy after therapeutical immunodepletion. We conclude that central memory TH17.1 cells play a pivotal role in MS pathogenesis and they represent a major target of MS therapeutics.

Mitigating alemtuzumab-associated autoimmunity in MS: A "whack-a-mole" B-cell depletion strategy

Objective

To determine whether the punctuated administration of low-dose rituximab, temporally linked to B-cell hyperrepopulation (defined when the return of CD19⁺ B cells approximates 40%–50% of baseline levels as measured before alemtuzumab treatment inception), can mitigate alemtuzumab-associated secondary autoimmunity.

Methods

In this hypothesis-driven pilot study, 10 patients received low-dose rituximab (50–150 mg/m²), a chimeric anti-CD20 monoclonal antibody, after either their first or second cycles of alemtuzumab. These patients were then routinely assessed for the development of autoimmune disorders and safety signals related to the use of dual monoclonal antibody therapy.

Results

Five patients received at least 1 IV infusion of low-dose rituximab, following alemtuzumab therapy, with a mean follow-up of 41 months. None of the 5 patients developed secondary autoimmune disorders. An additional 5 patients with follow-up over less than 24 months received at least 1 infusion of low-dose rituximab treatment following alemtuzumab treatment. No secondary autoimmune diseases were observed.

Conclusions

An anti-CD20 “whack-a-mole” B-cell depletion strategy may serve to mitigate alemtuzumab-associated secondary autoimmunity in MS by reducing the imbalance in B- and T-cell regulatory networks during immune reconstitution. We believe that these observations warrant further investigation.

Classification of evidence

This study provides Class IV evidence that for people with MS, low-dose rituximab following alemtuzumab treatment decreases the risk of alemtuzumab-associated secondary autoimmune diseases.

Engagement of people with multiple sclerosis to enhance research into the physiological effect of hyperbaric oxygen therapy

BACKGROUND

Thousands of people with multiple sclerosis (MS) have used self-administered oxygen therapy in the UK. Clinical trials have been performed, with scant evidence that people with MS have been consulted to explore how they benefit from or how to optimize this treatment. The conventional MS disease disability scores used in trials seldom reflect the effects individuals report when using oxygen therapy to treat their symptoms.

METHODS

Three people with MS and the manager of an MS Centre formed a public involvement group and collaborated with clinicians and scientists to inform a lab-based study to investigate the physiological effects of oxygen therapy on microvascular brain endothelial cells.

RESULTS

People with MS often use oxygen therapy at a later stage when their symptoms worsen and only after using other treatments. The frequency of oxygen therapy sessions and hyperbaric pressure is individualized and varies for people with MS. Despite direct comparisons of efficacy proving difficult, most individuals are exposed to 100% O₂ at 1.5 atmosphere absolute (ATA; 1140 mmHg absolute) for 60 min. In a laboratory-based study human brain endothelial cells were exposed in vitro to 152 mmHg O₂ for 60 min with and without pressure, as this equates to 20% O₂ achievable via hyperbarics, which was then replicated at atmospheric pressure. A significant reduction in endothelial cells ICAM-1 (CD54) implicated in inflammatory cell margination across the blood brain barrier was observed under oxygen treatment.

CONCLUSIONS

By collaborating with people living with MS, we were able to design laboratory-based experimental protocols that replicate their treatment regimens to advance our understanding of the physiological effects of hyperbaric oxygen treatment on brain cells and their role in neuroinflammation.

Natural killer cells in multiple sclerosis: A review

As the most common non-traumatic disabling disease among adolescents, multiple sclerosis (MS) is a devastating neurological inflammatory disease of the central nervous system. Research has not yet fully elucidated its pathogenesis, but it has shown MS to be a complex, multifactorial disease with many interplaying factors. One of these factors, natural killer (NK) cells, lymphocytes of the innate immune system, have recently gained attention due to the effects of daclizumab therapy, causing an expansion of the immunoregulatory subset of NK cells. Since then, NK cells and their relation to MS have been the focus of research, with many new findings being published in the last decade. In this review, NK cells are pictured as potent cytotoxic killers, as well as unique immune-regulators. Additionally, an overview of our current knowledge regarding NK cells in MS is given. The role of NK cells in MS is reviewed in the context of well-established environmental factors and current disease modifying therapies to gain further understanding of the pathogenesis and treatment options in MS.

T Helper Cells: The Modulators of Inflammation in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neurodegenerative disease characterized by the progressive loss of axonal myelin in several areas of the central nervous system (CNS) that is responsible for clinical symptoms such as muscle spasms, optic neuritis, and paralysis. The progress made in more than one decade of research in animal models of MS for clarifying the pathophysiology of MS disease validated the concept that MS is an autoimmune inflammatory disorder caused by the recruitment in the CNS of self-reactive lymphocytes, mainly CD4⁺ T cells. Indeed, high levels of T helper (Th) cells and related cytokines and chemokines have been found in CNS lesions and in cerebrospinal fluid (CSF) of MS patients, thus contributing to the breakdown of the blood-brain barrier (BBB), the activation of resident astrocytes and microglia, and finally the outcome of neuroinflammation. To date, several types of Th cells have been discovered and designated according to the secreted lineage-defining cytokines. Interestingly, Th1, Th17, Th1-like Th17, Th9, and Th22 have been associated with MS. In this review, we discuss the role and interplay of different Th cell subpopulations and their lineage-defining cytokines in modulating the inflammatory responses in MS and the approved as well as the novel therapeutic approaches targeting T lymphocytes in the treatment of the disease.

Anti-CD20 therapy depletes activated myelin-specific CD8+ T cells in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. CD8⁺ T cells have been strongly implicated in MS pathogenesis, but it is unclear whether myelin is a CD8⁺ T cell autoantigenic target in MS. This study demonstrated that while myelin-specific CD8⁺ T cells are present at similar frequencies in untreated MS patients and healthy subjects, the proportion of memory and CD20-expressing myelin-specific CD8⁺ T cells was increased in MS patients, suggesting prior antigen encounter. This activated phenotype was reversible as the memory and CD20-expressing populations of certain myelin-specific CD8⁺ T cells were reduced following anti-CD20 treatment.

CD8⁺ T cells are believed to play an important role in multiple sclerosis (MS), yet their role in MS pathogenesis remains poorly defined. Although myelin proteins are considered potential autoantigenic targets, prior studies of myelin-reactive CD8⁺ T cells in MS have relied on in vitro stimulation, thereby limiting accurate measurement of their ex vivo precursor frequencies and phenotypes. Peptide:MHC I tetramers were used to identify and validate 5 myelin CD8⁺ T cell epitopes, including 2 newly described determinants in humans. The validated tetramers were used to measure the ex vivo precursor frequencies and phenotypes of myelin-specific CD8⁺ T cells in the peripheral blood of untreated MS patients and HLA allele-matched healthy controls. In parallel, CD8⁺ T cell responses against immunodominant influenza epitopes were also measured. There were no differences in ex vivo frequencies of tetramer-positive myelin-specific CD8⁺ T cells between MS patients and control subjects. An increased proportion of myelin-specific CD8⁺ T cells in MS patients exhibited a memory phenotype and expressed CD20 compared to control subjects, while there were no phenotypic differences observed among influenza-specific CD8⁺ T cells. Longitudinal assessments were also measured in a subset of MS patients subsequently treated with anti-CD20 monoclonal antibody therapy. The proportion of memory and CD20⁺ CD8⁺ T cells specific for certain myelin but not influenza epitopes was significantly reduced following anti-CD20 treatment. This study, representing a characterization of unmanipulated myelin-reactive CD8⁺ T cells in MS, indicates these cells may be attractive targets in MS therapy.

CD3+CD20+ T cells and their roles in human diseases

CD3⁺CD20⁺ T cells are a population of CD3⁺ T cells co-expressing CD20 that make up to ∼3-5% of the CD3⁺ T-cell compartment in the peripheral blood of human beings. In healthy individuals, CD3⁺CD20⁺ T cells are heterogeneous for containing a lower proportion of CD4⁺ cells, but produce higher levels of IL-17A and/or IFN-γ than those of CD3⁺CD20^- T cells. Recently, emerging studies have shown a pathogenic behavior of CD3⁺CD20⁺ T cells in autoimmune diseases and CD20⁺ T-cell malignancies, and patients with the diseases may benefit from anti-CD20 immunotherapy to deplete these cells. However, CD3⁺CD20⁺ T cells may also play a protective role in ovarian cancer and HIV infection for their strong propensity to IFN-γ production. In this review, we will describe the current knowledge about CD3⁺CD20⁺ T-cell biology, and discuss their functional roles in autoimmune diseases as well as cancer and infectious diseases.

Ocrelizumab Depletes CD20⁺ T Cells in Multiple Sclerosis Patients

Ocrelizumab, a humanized monoclonal anti-CD20 antibody, has shown pronounced effects in reduction of disease activity in multiple sclerosis (MS) patients and has recently been approved for the treatment of patients with relapsing MS (RMS) and primary progressive MS (PPMS). CD20 is mainly expressed by B cells, but a subset of T cells (CD3⁺CD20⁺ T cells) also expresses CD20, and these CD20⁺ T cells are known to be a highly activated cell population. The blood of MS patients was analyzed with multicolor flow cytometry before and two weeks after treatment with ocrelizumab regarding the phenotype of peripheral blood mononuclear cells. CD20-expressing CD3⁺ T cells were found in blood samples of all MS patients, accounted for 2.4% of CD45⁺ lymphocytes, and constituted a significant proportion (18.4%) of all CD20⁺ cells. CD3⁺CD20⁺ T cells and CD19⁺CD20⁺ B cells were effectively depleted two weeks after a single administration of 300 mg ocrelizumab. Our results demonstrate that treatment with ocrelizumab does not exclusively target B cells, but also CD20⁺ T cells, which account for a substantial amount of CD20-expressing cells. Thus, we speculate that the efficacy of ocrelizumab might also be mediated by the depletion of CD20-expressing T cells.

B cell-based therapies in CNS autoimmunity: differentiating CD19 and CD20 as therapeutic targets

Increasing recognition of the role of B cells in the adaptive immune response makes B cells an important therapeutic target in autoimmunity. Numerous current and developmental immunotherapies target B cells for elimination through recognition of cell-surface proteins expressed specifically on B cells, in particular CD19 and CD20. Similarities and differences in the function and expression of these two molecules predict some shared, and some distinct, pharmacological effects of agents targeting CD19 versus CD20, potentially leading to differences in the clinical safety and efficacy of such agents. Here, we review current knowledge of CD19 and CD20 function and biology, survey current and developmental therapies that target these molecules, and discuss potential differences in elimination of B cells by drugs that target CD19 versus CD20, with particular focus on the central nervous system autoimmune diseases multiple sclerosis and neuromyelitis optica. The principles and mechanisms herein discussed might also be relevant to a variety of other nervous system autoimmune disorders, including NMDA (N-methyl-D-aspartate) receptor encephalitis, transverse myelitis and myasthenia gravis.

Dissection of a circulating CD3+ CD20+ T cell subpopulation in patients with psoriasis

CD3⁺ CD20⁺ T cells are a population of CD3⁺ T cells that express CD20 and identified in healthy donors and autoimmune diseases. However, the nature and role of these cells in patients with psoriasis remain unclear. In this study, we aimed to investigate the level, phenotype, functional and clinical relevance of CD3⁺ CD20⁺ T cells in the peripheral blood of patients with psoriasis. We found that a small subset of CD3⁺ T cells expressed CD20 molecule in the peripheral blood of patients with psoriasis, and their levels were similar to those in healthy donors. Circulating CD3⁺ CD20⁺ T cells in patients with psoriasis were enriched in CD4⁺ cells and displayed an activated effector phenotype, as these cells contained fewer CD45RA⁺ -naive and CCR7⁺ cells with increased activity than those of CD3⁺ T cells lacking CD20. In addition, compared with healthy donors, circulating CD3⁺ CD20⁺ T cells in patients with psoriasis produced more cytokines, interleukin (IL)-17A, tumour necrosis factor (TNF)-α and IL-21, but not IL-4 and IFN-γ. Furthermore, a significantly positive correlation was found between the levels of IL-17A, TNF-α and IL-21-production CD3⁺ CD20⁺ T cells with Psoriasis Area and Severity Index scores. Our findings suggest that CD3⁺ CD20⁺ T cells may play a role in the pathogenesis of psoriasis.

Impact of Glatiramer Acetate on B Cell-Mediated Pathogenesis of Multiple Sclerosis

Growing evidence indicates that B cells play a key role in the pathogenesis of multiple sclerosis (MS). B cells occupy distinct central nervous system (CNS) compartments in MS, including the cerebrospinal fluid and white matter lesions. Also, it is now known that, in addition to entering the CNS, B cells can circulate into the periphery via a functional lymphatic system. Data suggest that the role of B cells in MS mainly involves their in situ activation in demyelinating lesions, leading to altered pro- and anti-inflammatory cytokine secretion, and a highly effective antigen-presenting cell function, resulting in activation of memory or naïve T cells. Clinically, B cell-depleting agents show significant efficacy in MS. In addition, many disease-modifying therapies (DMTs) traditionally understood to target T cells are now known to influence B cell number and function. One of the earliest DMTs to be developed, glatiramer acetate (GA), has been shown to reduce the total frequency of B cells, plasmablasts, and memory B cells. It also appears to promote a shift toward reduced inflammation by increasing anti-inflammatory cytokine release and/or reducing pro-inflammatory cytokine release by B cells. In the authors' opinion, this may be mediated by cross-reactivity of B cell receptors for GA with antigen (possibly myelin basic protein) expressed in the MS lesion. More research is required to further characterize the role of B cells and their bidirectional trafficking in the pathogenesis of MS. This may uncover novel targets for MS treatments and facilitate the development of B cell biomarkers of drug response.

New horizons for multiple sclerosis therapeutics: milestones in the development of ocrelizumab

Multiple Sclerosis (MS) is an inflammatory and neurodegenerative disease of the central nervous system, and both T and B cells are involved in its pathogenesis. The vast majority of disease-modifying drugs used for MS act on the inflammatory component of the disease and are approved for use in relapsing-remitting (RR) patients. Ocrelizumab (OCR) is the only MS drug that has been approved by the US Food and Drug Administration (FDA) not only for patients with RRMS but also for patients with primary progressive (PP) MS. OCR is a humanized anti-CD20 monoclonal antibody that can deplete the targeted B cells through antibody-dependent cellular cytotoxicity. Treatment involves administration by intravenous infusion every 6 months. OCR can cause long-lasting B-cell depletion and change the pool of reconstituted B cells. Phase III clinical trials have confirmed the results of previous Phase II studies. In particular, OPERA I and II trials, which were performed in patients with RRMS, showed a reduction in the annualized relapse rate, the risk of disability progression, and the number of new/enlarging T2 lesions and enhancing lesions measured using brain magnetic resonance. The ORATORIO trial, performed in PP subjects, showed that OCR can reduce disability progression, improve performance on the timed 25-foot walk, and decrease the total volume of T2 lesions and the mean number of new or enlarging T2 lesions. The most frequent adverse events were the infusion-related reactions and infections. Infections were mostly nasopharyngitis, as well as upper respiratory and urinary tract infections. OCR gives no indication for severe or opportunistic infections. There is not a clear increased risk of malignancies. Nevertheless, it could not be excluded. Real-life registries will provide more information about the long-term safety, the risk of exposure during pregnancy, and the risk of rare adverse events. In this review, we analyze the evidence regarding the efficacy and the safety of OCR.

B-cell Therapy for Multiple Sclerosis: Entering an era

Monoclonal antibodies that target CD20 expressing B cells represent an important new treatment option for patients with multiple sclerosis (MS). B-cell-depleting therapy is highly effective against relapsing forms of the disease and is also the first treatment approach proven to protect against disability worsening in primary progressive MS. Moreover, evolving clinical experience with B-cell therapy, combined with a more sophisticated understanding of humoral immunity in preclinical models and in patients with MS, has led to major progress in deciphering the immune pathogenesis of MS. Here, we review the nuanced roles of B cells in MS autoimmunity, the clinical data supporting use of ocrelizumab and other anti-CD20 therapies in the treatment of MS, as well as safety and practical considerations for prescribing. Last, we summarize remaining unanswered questions regarding the proper role of anti-CD20 therapy in MS, its limitations, and the future landscape of B-cell-based approaches to treatment. Ann Neurol 2018;83:13-26.

Deciphering the Role of B Cells in Multiple Sclerosis-Towards Specific Targeting of Pathogenic Function

B cells, plasma cells and antibodies may play a key role in the pathogenesis of multiple sclerosis (MS). This notion is supported by various immunological changes observed in MS patients, such as activation and pro-inflammatory differentiation of peripheral blood B cells, the persistence of clonally expanded plasma cells producing immunoglobulins in the cerebrospinal fluid, as well as the composition of inflammatory central nervous system lesions frequently containing co-localizing antibody depositions and activated complement. In recent years, the perception of a respective pathophysiological B cell involvement was vividly promoted by the empirical success of anti-CD20-mediated B cell depletion in clinical trials; based on these findings, the first monoclonal anti-CD20 antibody—ocrelizumab—is currently in the process of being approved for treatment of MS. In this review, we summarize the current knowledge on the role of B cells, plasma cells and antibodies in MS and elucidate how approved and future treatments, first and foremost anti-CD20 antibodies, therapeutically modify these B cell components. We will furthermore describe regulatory functions of B cells in MS and discuss how the evolving knowledge of these therapeutically desirable B cell properties can be harnessed to improve future safety and efficacy of B cell-directed therapy in MS.

Rituximab in Minimal Change Disease: Mechanisms of Action and Hypotheses for Future Studies

Treatment with rituximab, a monoclonal antibody against the B-lymphocyte surface protein CD20, leads to the depletion of B cells. Recently, rituximab was reported to effectively prevent relapses of glucocorticoid-dependent or frequently relapsing minimal change disease (MCD). MCD is thought to be T-cell mediated; how rituximab controls MCD is not understood. In this review, we summarize key clinical studies demonstrating the efficacy of rituximab in idiopathic nephrotic syndrome, mainly MCD. We then discuss immunological features of this disease and potential mechanisms of action of rituximab in its treatment based on what is known about the therapeutic action of rituximab in other immune-mediated disorders. We believe that studies aimed at understanding the mechanisms of action of rituximab in MCD will provide a novel approach to resolve the elusive immune pathophysiology of MCD.

Rab32 connects ER stress to mitochondrial defects in multiple sclerosis

BACKGROUND

Endoplasmic reticulum (ER) stress is a hallmark of neurodegenerative diseases such as multiple sclerosis (MS). However, this physiological mechanism has multiple manifestations that range from impaired clearance of unfolded proteins to altered mitochondrial dynamics and apoptosis. While connections between the triggering of the unfolded protein response (UPR) and downstream mitochondrial dysfunction are poorly understood, the membranous contacts between the ER and mitochondria, called the mitochondria-associated membrane (MAM), could provide a functional link between these two mechanisms. Therefore, we investigated whether the guanosine triphosphatase (GTPase) Rab32, a known regulator of the MAM, mitochondrial dynamics, and apoptosis, could be associated with ER stress as well as mitochondrial dysfunction.

METHODS

We assessed Rab32 expression in MS patient and experimental autoimmune encephalomyelitis (EAE) tissue, via observation of mitochondria in primary neurons and via monitoring of survival of neuronal cells upon increased Rab32 expression.

RESULTS

We found that the induction of Rab32 and other MAM proteins correlates with ER stress proteins in MS brain, as well as in EAE, and occurs in multiple central nervous system (CNS) cell types. We identify Rab32, known to increase in response to acute brain inflammation, as a novel unfolded protein response (UPR) target. High Rab32 expression shortens neurite length, alters mitochondria morphology, and accelerates apoptosis/necroptosis of human primary neurons and cell lines.

CONCLUSIONS

ER stress is strongly associated with Rab32 upregulation in the progression of MS, leading to mitochondrial dysfunction and neuronal death.

CD20 therapies in multiple sclerosis and experimental autoimmune encephalomyelitis - Targeting T or B cells?

MS is widely considered to be a T cell-mediated disease although T cell immunotherapy has consistently failed, demonstrating distinct differences with experimental autoimmune encephalomyelitis (EAE), an animal model of MS in which T cell therapies are effective. Accumulating evidence has highlighted that B cells also play key role in MS pathogenesis. The high frequency of oligoclonal antibodies in the CSF, the localization of immunoglobulin in brain lesions and pathogenicity of antibodies originally pointed to the pathogenic role of B cells as autoantibody producing plasma cells. However, emerging evidence reveal that B cells also act as antigen presenting cells, T cell activators and cytokine producers suggesting that the strong efficacy of anti-CD20 antibody therapy observed in people with MS may reduce disease progression by several different mechanisms. Here we review the evidence and mechanisms by which B cells contribute to disease in MS compared to findings in the EAE model.

Mutation analysis of the MS4A and TREM gene clusters in a case-control Alzheimer's disease data set

Genome wide association studies have identified an association between Alzheimer's disease (AD) and common polymorphisms in the MS4A and TREM loci (each containing a cluster of homologous genes) and should be thoroughly investigated for the presence of potentially functional variations. We conducted a mutation analysis by next generation sequencing of 15 genes within the MS4A and TREM gene clusters; and catalogued rare coding variants detected in a North American data set of 210 cases and 233 controls. Investigation of the 5 homologues genes in the TREM locus revealed potentially damaging rare variants in TREM2, TREML1, TREML2, and TREML4. In agreement with a previous report, we observed a significant enrichment of TREM2-damaging missense substitutions in cases (N = 9; 4.2%) compared with controls (N=2; 0.9%; p = 0.010; after Yates' correction p = 0.022). Among known AD-associated TREM2 substitutions, we detected p.R47H, p.D87N, and p.H157Y affecting both TREM2 isoforms (NM_018965 and NM_001271821). In addition, we identified 2 cases with novel TREM2 variants (p.L205P and p.G219C), which mapped only to the isoform NM_001271821 at the C-terminus. Investigation of the MS4A gene cluster revealed that potentially damaging missense substitutions and loss-of-function variants were twice as frequent in controls (N = 19; 8.2%) than cases (N = 9; 4.3%), generating a nominally significant result (p = 0.047; after Yates' correction p = 0.07). Validation of our observation in large data sets might address the question whether such variants could contribute to the protective effect of the minor alleles of Genome wide association study-significant single nucleotide polymorphisms at the MS4A locus.

Increases in NKG2C Expression on T Cells and Higher Levels of Circulating CD8+ B Cells Are Associated with Sterilizing Immunity Provided by a Live Attenuated SIV Vaccine

Vaccines based on live attenuated viruses are highly effective immunogens in the simian immunodeficiency virus (SIV)/rhesus macaque animal model and offer the possibility of studying correlates of protection against infection with virulent virus. We utilized a tether system for studying, in naive macaques and animals vaccinated with a live-attenuated vaccine, the acute events after challenge with pathogenic SIV. This approach allowed for the frequent sampling of small blood volumes without sedation or restraining of the animals, thus reducing the confounding effect of sampling stress. Before challenge, vaccinated animals presented significantly higher levels of proliferating and activated B cells than naive macaques, which were manifested by high expression of CD8 on B cells. After SIV challenge, the only changes observed in protected vaccinated macaques were significant increases in expression of the NK marker NKG2C on CD4 and CD8 T cells. We also identified that infection of naive macaques with SIV resulted in a transient peak of expression of CD20 on CD8 T cells and a constant rise in the number of B cells expressing CD8. Finally, analysis of a larger cohort of vaccinated animals identified that, even when circulating levels of vaccine virus are below the limit of detection, live attenuated vaccines induce systemic increases of IP-10 and perforin. These studies indicate that components of both the innate and adaptive immune systems of animals inoculated with a live-attenuated SIV vaccine respond to and control infection with virulent virus. Persistence of the vaccine virus in tissues may explain the elevated cytokine and B-cell activation levels. In addition, our report underpins the utility of the tether system for the intensive study of acute immune responses to viral infections.

CD20+ T cells have a predominantly Tc1 effector memory phenotype and are expanded in the ascites of patients with ovarian cancer

Recently, a small subset of T cells that expresses the B cell marker CD20 has been identified in healthy volunteers and in patients with rheumatoid arthritis and multiple sclerosis. The origin of these CD20-positive T cells as well as their relevance in human disease remains unclear. Here, we identified that after functional B cell/T cell interaction CD20 molecules are transferred to the cell surface of T cells by trogocytosis together with the established trogocytosis marker HLA-DR. Further, the presence of CD20 on isolated CD20⁺ T cells remained stable for up to 48h of ex vivo culture. These CD20⁺ T cells almost exclusively produced IFNγ (∼70% vs. ∼20% in the CD20^- T cell population) and were predominantly (CD8⁺) effector memory T cells (∼60-70%). This IFNγ producing and effector memory phenotype was also determined for CD20⁺ T cells as detected in the peripheral blood and ascitic fluids of ovarian cancer (OC) patients. In the latter, the percentage of CD20⁺ T cells was further strongly increased (from ∼6% in peripheral blood to 23% in ascitic fluid). Taken together, the data presented here indicate that CD20 is transferred to T cells upon intimate T cell/B cell interaction. Further, CD20⁺ T cells are of memory and IFNγ producing phenotype and are present in increased amounts in ascitic fluid of OC patients.