T Follicular Regulatory Research Articles

T follicular regulatory cells in food allergy promote IgE via IL-4.

T follicular regulatory (TFR) cells are found in the germinal center (GC) response and, along with T follicular helper (TFH) cells, help to control the development of high-affinity antibodies (Ab). Although TFR cells are generally thought to repress GC B cells and the Ab response, we have previously shown that in a mouse food allergy model, TFR cells produce IL-10 and play an essential helper role such that in the absence of TFR cells, IgE responses are diminished. Here we show that in this food allergy response, TFR cells produced IL-4 that promotes the generation of antigen-specific IgE. We show that food allergy-primed TFR cells specifically upregulate IL-4 gene transcription and produce functional IL-4 that promoted IgE responses both in vitro and in vivo. We determined that IgE responses are dependent on a high level of IL-4 produced by follicular T cells in the GC, explaining the need for IL-4 produced by TFR cells in the food allergy response. Overall, our findings have demonstrated that in food allergy, TFR cells can produce IL-4 and regulate IgE in a manner that augments the role of TFH cells in IgE responses.

Id1 expression in CD4 T cells promotes differentiation and function of follicular helper T cells and upregulation of related functional molecules.

Although the roles of E proteins and inhibitors of DNA-binding (Id) in T follicular helper (TFH) and T follicular regulatory (TFR) cells have been previously reported, direct models demonstrating the impact of multiple E protein members have been lacking. To suppress all E proteins including E2A, HEB and E2-2, we overexpressed Id1 in CD4 cells using a CD4-Id1 mouse model, to observe any changes in TFH and TFR cell differentiation. Our objective was to gain better understanding of the roles that E proteins and Id molecules play in the differentiation of TFH and TFR cells. The CD4-Id1 transgenic (TG) mice that we constructed overexpressed Id1 in CD4 cells, inhibiting E protein function. Our results showed an increase in the proportion and absolute numbers of Treg, TFH and TFR cells in the spleen of TG mice. Additionally, the expression of surface characterisation molecules PD-1 and ICOS was significantly upregulated in TFH and TFR cells. The study also revealed a downregulation of the marginal zone B cell precursor and an increase in the activation and secretion of IgG1 in spleen B cells. Furthermore, the peripheral TFH cells of TG mice enhanced the function of assisting B cells. RNA sequencing results indicated that a variety of TFH-related functional molecules were upregulated in TFH cells of Id1 TG mice. In conclusion, E proteins play a crucial role in regulating TFH/TFR cell differentiation and function and suppressing E protein activity promotes germinal centre humoral immunity, which has important implications for immune regulation and treating related diseases.

Interactions between B cells and T follicular regulatory cells enhance susceptibility to Brucella infection independent of the anti-Brucella humoral response.

Brucellosis, caused by facultative, intracellular Brucella spp., often results in chronic and/or lifelong infection. Therefore, Brucella must employ mechanisms to subvert adaptive immunity to cause chronic infection. B lymphocytes enhance susceptibility to infection with Brucella spp. though the mechanisms remain unclear. Here we investigated the role of antibody secretion, B cell receptor (BCR) specificity, and B cell antigen presentation on susceptibility to B. melitensis. We report that mice unable to secrete antibody do not display altered resistance to Brucella. However, animals with B cells that are unable to recognize Brucella through their BCR are resistant to infection. In addition, B cell MHCII expression enhances susceptibility to infection in a CD4+ T cell-dependent manner, and we found that follicular B cells are sufficient to inhibit CD4+ T cell-mediated immunity against Brucella. B cells promote development of T follicular helper (TFH) and T follicular regulatory (TFR) cells during Brucella infection. Inhibition of B cell and CD4+ T cell interaction via CD40L blockade enhances resistance to Brucella in a B cell dependent manner concomitant with suppression of TFH and TFR differentiation. Conversely, PD-1 blockade increases Brucella burdens in a B and CD4+ T cell dependent manner while augmenting T regulatory (TReg) and TFR responses. Intriguingly, TFR deficiency enhances resistance to Brucella via a B cell dependent, but antibody independent mechanism. Collectively, these results demonstrate B cells support TFR responses that promote susceptibility to Brucella infection independent of the antibody response.

CARD11 gain-of-function mutation drives cell-autonomous accumulation of PD-1+ ICOShigh activated T cells, T-follicular, T-regulatory and T-follicular regulatory cells.

Germline CARD11 gain-of-function (GOF) mutations cause B cell Expansion with NF-κB and T cell Anergy (BENTA) disease, whilst somatic GOF CARD11 mutations recur in diffuse large B cell lymphoma (DLBCL) and in up to 30% of the peripheral T cell lymphomas (PTCL) adult T cell leukemia/lymphoma (ATL), cutaneous T cell lymphoma (CTCL) and Sezary Syndrome. Despite their frequent acquisition by PTCL, the T cell-intrinsic effects of CARD11 GOF mutations are poorly understood. Here, we studied B and T lymphocytes in mice with a germline Nethyl-N-nitrosourea (ENU)-induced Card11M365K mutation identical to a mutation identified in DLBCL and modifying a conserved region of the CARD11 coiled-coil domain recurrently mutated in DLBCL and PTCL. Our results demonstrate that CARD11.M365K is a GOF protein that increases B and T lymphocyte activation and proliferation following antigen receptor stimulation. Germline Card11M365K mutation was insufficient alone to cause B or T-lymphoma, but increased accumulation of germinal center (GC) B cells in unimmunized and immunized mice. Card11M365K mutation caused cell-intrinsic over-accumulation of activated T cells, T regulatory (TREG), T follicular (TFH) and T follicular regulatory (TFR) cells expressing increased levels of ICOS, CTLA-4 and PD-1 checkpoint molecules. Our results reveal CARD11 as an important, cell-autonomous positive regulator of TFH, TREG and TFR cells. They highlight T cell-intrinsic effects of a GOF mutation in the CARD11 gene, which is recurrently mutated in T cell malignancies that are often aggressive and associated with variable clinical outcomes.

TFR Cells Express Functional CCR6 But It Is Dispensable for Their Development and Localization During Splenic Humoral Immune Responses.

Follicular T cells including T follicular helper (TFH) and T follicular regulatory (TFR) cells are essential in supporting and regulating the quality of antibody responses that develop in the germinal centre (GC). Follicular T cell migration during the propagation of antibody responses is largely attributed to the chemokine receptor CXCR5, however CXCR5 is reportedly redundant in migratory events prior to formation of the GC, and CXCR5-deficient TFH and TFR cells are still capable of localizing to GCs. Here we comprehensively assess chemokine receptor expression by follicular T cells during a model humoral immune response in the spleen. In addition to the known follicular T cell chemokine receptors Cxcr5 and Cxcr4, we show that follicular T cells express high levels of Ccr6, Ccr2 and Cxcr3 transcripts and we identify functional expression of CCR6 protein by both TFH and TFR cells. Notably, a greater proportion of TFR cells expressed CCR6 compared to TFH cells and gating on CCR6+CXCR5hiPD-1hi T cells strongly enriched for TFR cells. Examination of Ccr6-/- mice revealed that CCR6 is not essential for development of the GC response in the spleen, and mixed bone marrow chimera experiments found no evidence for an intrinsic requirement for CCR6 in TFR cell development or localisation during splenic humoral responses. These findings point towards multiple functionally redundant chemotactic signals regulating T cell localisation in the GC.

Development of allergen-specific IgE in a food-allergy model requires precisely timed B cell stimulation and is inhibited by Fgl2.

SUMMARYImmunoglobulin E (IgE) responses are a central feature of allergic disease. Using a well-established food-allergy model in mice, we show that two sensitizations with cognate B cell antigen (Ag) and adjuvant 7 days apart promotes optimal development of IgE+ germinal center (GC) B cells and high-affinity IgE production. Intervals of 3 or 14 days between Ag sensitizations lead to loss of IgE+ GC B cells and an undetectable IgE response. The immunosuppressive factors Fgl2 and CD39 are down-regulated in T follicular helper (TFH) cells under optimal IgE-sensitization conditions. Deletion of Fgl2 in TFH and T follicular regulatory (TFR) cells, but not from TFR cells alone, increase Ag-specific IgE levels and IgE-mediated anaphylactic responses. Overall, we find that Ag-specific IgE responses require precisely timed stimulation of IgE+ GC B cells by Ag. Furthermore, we show that Fgl2 is expressed by TFH cells and represses IgE. This work has implications for the development and treatment of food allergies.

Restoration of Follicular T Regulatory/Helper Cell Balance by OX40L-JAG1 Cotreatment Suppresses Lupus Nephritis in NZBWF1/j Mice.

Class-switched antinuclear autoantibodies produced by T follicular helper (TFH) cell-dependent germinal center (GC) B cell response play an essential pathogenic role in lupus nephritis (LN). The role of T follicular regulatory (TFR) cells, an effector subset of CD4+Foxp3+ T regulatory cells (Tregs), which are specialized in suppressing TFH-GC response and Ab production, remains elusive in LN. Contrasting reports have shown increased/reduced circulating TFR cells in human lupus that might not accurately reflect their presence in the GCs of relevant lymphoid organs. In this study, we report a progressive reduction in TFR cells and decreased TFR/TFH ratio despite increased Tregs in the renal lymph nodes of NZBWF1/j mice, which correlated with increased GC-B cells and proteinuria onset. Cotreatment with soluble OX40L and Jagged-1 (JAG1) proteins increased Tregs, TFR cells, and TFR/TFH ratio, with a concomitant reduction in TFH cells, GC B cells, and anti-dsDNA IgG Ab levels, and suppressed LN onset. Mechanistic studies showed attenuated TFH functions and diminished GC events such as somatic hypermutation and isotype class-switching in OX40L-JAG1-treated mice. RNA sequencing studies revealed inhibition of hypoxia-inducible factor 1-α (HIF-1a) and STAT3 signaling in T conventional cells from OX40L-JAG1-treated mice, which are critical for the glycolytic flux and differentiation into TFH cell lineage. Therefore, the increased TFR/TFH ratio seen in OX40L-JAG1-treated mice could involve both impaired differentiation of TFH cells from T conventional cells and expansion of TFR cells. We show a key role for GC-TFR/TFH imbalance in LN pathogenesis and how restoring homeostatic balance can suppress LN.

NFATc1/αA and Blimp-1 Support the Follicular and Effector Phenotype of Tregs.

CD4+CXCR5+Foxp3+ T-follicular regulatory (TFR) cells control the germinal center responses. Like T-follicular helper cells, they express high levels of Nuclear Factor of Activated T-cells c1 , predominantly its short isoform NFATc1/αA. Ablation of NFATc1 in Tregs prevents upregulation of CXCR5 and migration of TFR cells into B-cell follicles. By contrast, constitutive active NFATc1/αA defines the surface density of CXCR5, whose level determines how deep a TFR migrates into the GC and how effectively it controls antibody production. As one type of effector Treg, TFR cells express B lymphocyte-induced maturation protein-1 (Blimp-1). Blimp-1 can directly repress Cxcr5 and NFATc1/αA is necessary to overcome this Blimp-1-mediated repression. Interestingly, Blimp-1 even reinforces the recruitment of NFATc1 to Cxcr5 by protein-protein interaction and by those means cooperates with NFATc1 for Cxcr5 transactivation. On the contrary, Blimp-1 is necessary to counterbalance NFATc1/αA and preserve the Treg identity. This is because although NFATc1/αA strengthens the follicular development of Tregs, it bears the inherent risk of causing an ex-Treg phenotype.

Assessment of the Impact of Cytokines on TFH, TREG, and TFR Cell Populations After Influenza Infection.

Within the last several years, great strides have been made in understanding the molecular and cellular mechanisms that control the generation of T follicular helper (TFH), T regulatory (TREG), and T follicular regulatory (TFR) cells. As a result, it is now clear that cytokines play a critical role in regulating the development and function of these CD4+ T cell subsets. One of the critical limitations when studying the effect of individual cytokines in these populations is differentiating between the intrinsic and extrinsic effects of these cytokines in vivo. Here we describe how to utilize mixed bone marrow chimeras in combination with MHC class II tetramers to characterize the direct role played by cytokines on controlling the development, function, and maintenance of TFH, TREG, and TFR cells in vivo.

Expression of Foxp3 by T follicular helper cells in end-stage germinal centers.

Germinal centers (GCs) are the site of immunoglobulin somatic hypermutation and affinity maturation, processes essential to an effective antibody response. The formation of GCs has been studied in detail, but less is known about what leads to their regression and eventual termination, factors that ultimately limit the extent to which antibodies mature within a single reaction. We show that contraction of immunization-induced GCs is immediately preceded by an acute surge in GC-resident Foxp3+ T cells, attributed at least partly to up-regulation of the transcription factor Foxp3 by T follicular helper (TFH) cells. Ectopic expression of Foxp3 in TFH cells is sufficient to decrease GC size, implicating the natural up-regulation of Foxp3 by TFH cells as a potential regulator of GC lifetimes.

Regulating germinal center contraction

Immunology Germinal centers (GCs) in secondary lymphoid organs are where mature B cells expand and differentiate. Although GC formation is well studied, the control of GC duration and contraction is less well understood. Using intravital imaging of mouse GCs and single-cell RNA sequencing, Jacobsen et al. report that T follicular helper (TFH) cells are a critical player in this process. They found that some late-GC TFH cells upregulate the transcription factor FOXP3 and acquire a regulatory T cell–like phenotype. These cells are distinct from T follicular regulatory (TFR) cells and, unlike TFR cells, are needed to shut down the GC reaction. Tweaking this process may be key to extending GC lifetimes and enhancing antibody responses in the context of vaccination. Science , abe5146, this issue p. [eabe5146][1] [1]: /lookup/doi/10.1126/science.abe5146

T Follicular Regulatory (TFR) Cell Deficiency during Chronic Graft-Versus-Host Disease Is Improved By Low-Dose IL-2 Therapy

Background: Chronic Graft versus Host Disease (cGVHD) reflects the inability to achieve immune tolerance after allogeneic stem cell transplantation (allo-SCT) resulting in the persistence of allo and auto-reactive T cells and B cells. We previously showed that regulatory T cells (Treg) are decreased in patients with cGVHD and may be rescued by low dose IL-2 therapy resulting in improved Treg number and survival and clinical improvement of cGVHD symptoms. More recently, we showed that circulating T follicular helper cells (cTFH) have increased function during cGVHD, thus stimulating B cells to produce auto and allo-antibodies involved in cGVHD. T follicular regulatory cells (TFR) regulate the germinal center (GC) reaction and suppress B cell differentiation and immunoglobulin secretion. TFR reside primarily in lymphoid tissues but also circulate in small numbers. In the present study we characterized the numbers and function of blood CD3+CD4+CD45RA-CD25hiFoxP3+CXCR5+ TFR in healthy donors (HD; N=18) and allo-SCT patients (N=64).Results: Patients undergoing allo-SCT showed a significant reduction of circulating TFR (cTFR) compared to HD (median: 0.08% vs 0.34% of CD4+T respectively, p<10-4). Moreover, patients with active cGVHD (N=37) had significantly lower cTFR frequency compared to patients with no cGVHD (N=15) (median: 0.034 vs 0.18% of CD4+, p=0.0012) and resolved cGVHD (N=12) (median: 0.034 vs 0.14, p=0.02). Interestingly, cTFR values tended to be negatively associated with cGVHD grade (median cTFR %: 0.11 vs 0.029, p=0.004 for mild vs moderate; 0.11 vs 0.012, p=0.005 for mild vs severe; 0.029 vs 0.012, p=0.2 for moderate vs severe). The numeric reduction of cTFR in cGVHD patients appears to be a consequence of decreased survival as attested by lower BCL-2 expression (median: 1831 vs 1939, p=0.037 in active cGVHD and without cGVHD, respectively). This favors the survival of TFH effector cells (CD4+CD45RA-CXCR5+ excluding CD25hiFoxP3+) as measured by the ratio of expression of BCL-2 in effectors/regulators in active compared to no cGVHD (BCL-2 E/R ratio: 1.26 vs 1.14, p=0.0013 respectively). Similar to tonsil TFR, blood TFR exhibit suppressive functions in in vitro assays. Purified TFR were co-cultured with TFH and memory B cells at different ratios. The addition of TFR was associated with a significant reduction of plasmablast (PB) generation (CD27hiCD38hiCD19+ cells) (Figure 1A, t-test: p=0.0087) and IgG production (Figure 1B, t-test: p=0.0087). Human cTFR in vivo display similar suppressive function toward B cells, as analysis of active cGVHD patients revealed an inverse correlation between TFR and PB frequency in the peripheral blood (Spearman test: r = -0.49, p=0.003) (Figure 1C). As IL-2 has been shown to enhance regulatory T cells, we assessed its impact on the GC reaction in vitro . Purified TFH and memory B cells from HD were co-cultured at different doses of IL-2 from 0 to 100 IU/mL, simulating a germinal center reaction in vitro . Low dose IL-2 starting at 10 IU/mL was associated with a suppressive effect on PB generation and IgG production that peaked at 50 IU/mL reflecting the high expression level of IL-2 high affinity receptor (CD25). We also evaluated the capacity of IL-2 to restore in vivo cTFR:cTFH ratio using mass cytometry (CyTOF) in a cohort of patients receiving IL-2 (1x106 IU/M2/day) for 12 weeks as previously described (Koreth et al, Blood 2016). We observed an improvement of blood cTFR:cTFH ratio over the course of IL-2 therapy, with a maximum ratio observed at 2 weeks, and subsequently decreasing to reach baseline values after stopping IL-2 (Figure 2).Conclusion: Our results confirm that blood TFR exert a suppressive function as evidence by an inverse correlation with PB and in vitro suppression of memory B cell Ig production. This suppressive subset is deficient in patients with cGVHD due to altered TFR survival, thus favoring imbalance toward TFH effectors which may promote a GC reaction in vivo resulting in PB and memory B cell pathogenic Ig production. By enhancing TFR, low-dose IL-2 therapy promotes effective control of the GC reaction. [Display omitted] DisclosuresForcade:Neovii: Other: Travel grant. Koreth:Millennium Pharmaceuticals: Research Funding; Amgen Inc.: Consultancy; Prometheus Labs: Research Funding; Kadmon Corp: Membership on an entity's Board of Directors or advisory committees; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Nikiforow:Kite Therapeutics: Membership on an entity's Board of Directors or advisory committees. Armand:Roche: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Sequenta/Adaptive: Research Funding; Affimed: Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Sigma Tau: Research Funding; Otsuka: Research Funding; Pfizer: Consultancy, Research Funding; Infinity: Consultancy; Tensha: Research Funding; Genmab: Consultancy. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Reconstructing TFR cell development

T Cells Antibody responses, including those against self-antigens, are tightly controlled within germinal centers by balancing the activity of T follicular regulatory (TFR) and T follicular helper (TFH) cells. Kumar et al. reconstructed the developmental trajectory of TFR cells using flow cytometry–indexed single-cell transcriptomics of follicular T cells isolated from human peripheral blood, lymph nodes, and tonsils. They used transcriptomics to support a model in which mature germinal center TFR cells arise from regulatory T cells, with circulating TFR cells representing a separate developmental pathway. These results suggest that mature TFR cells primarily arise independently from their less mature counterparts in peripheral blood, providing further insight into how human TFR cells develop. Sci. Immunol. 6 , eabd8411 (2021).

Modulating T Follicular Cells In Vivo Enhances Antigen-Specific Humoral Immunity.

Generation of high-affinity IgG is essential for defense against infections and cancer, which is the intended consequence of many vaccines, but can cause autoimmune and inflammatory diseases when inappropriately directed against self. The interplay of T follicular helper (TFH) cells and T follicular regulatory (TFR) cells is critical for the production of high-affinity IgG of a specific subclass. In this study, we sought to improve Ag-specific IgG responses with two interventions intended to transiently diminish TFR cell influence. First, adult mice were administered an antibiotic mixture (ABX) for an extended period to deplete the immunoregulatory intestinal microbiota. This intriguingly increased TFH cell and reduced TFR cell numbers. 2,4,6-Trinitrophenyl hapten conjugated to keyhole limpet hemocyanin immunization resulted in higher affinity 2,4,6-trinitrophenyl hapten-specific IgG1 in ABX mice compared with controls. In a model of IgG-driven inflammatory nephritis, ABX mice had significantly worse nephritis accompanied by higher affinity Ag-specific IgG2b and enriched TFH cells compared with controls. Second, we sought to functionally manipulate TFH and TFR cells, which both express the checkpoint inhibitory molecule, PD-1, by administration of anti-PD-1 during immunization. This intervention enhanced the affinity of Ag-specific IgG of the appropriate subclass and increased in TFH cells following 2,4,6-trinitrophenyl hapten conjugated to keyhole limpet hemocyanin immunization and nephritis induction. These results suggest that altering TFH and TFR cell ratios during immunization is an appealing strategy to qualitatively improve Ag- and subclass-specific IgG responses.

SATB1 Expression Governs Follicular Helper T-cell-Triggered Tertiary Lymphoid Structure Assembly

Tertiary Lymphoid Structures (TLS) are commonly identified in human tumors with improved outcome, but how they are orchestrated remains elusive. We show that ablation of the genomic organizer SATB1 triggers the polarization of CD4+ T-cells into antigen-specific T Follicular Helper (TFH) cells. In contrast, SATB1 expression is required for conversion of CD4+ T-cells into induced regulatory T-cells (Treg), including T Follicular Regulatory (TFR) cells. Paradoxically, Tgf-β-driven Satb1 silencing causes Icos de-repression and prevents TFR differentiation, driving TFH polarization and increased isotype-switched B cell responses. Tumors in mice carrying Satb1-deficient CD4+ T-cells accumulate more tumor antigen-specific, Light/Cxcl13/Il-21-producing TFH cells, causing germinal center formation and spontaneous TLS assembly, which antagonizes tumor growth. Accordingly, TFH cell transfer induces large TLS within orthotopic ovarian tumors. Therefore, SATB1 repression in CD4+ T-cells licenses TFH cell differentiation while preventing Treg conversion, a central mechanism during TLS assembly that can be exploited to boost anti-tumor immunity.

Altered chromatin landscape in circulating T follicular helper and regulatory cells following grass pollen subcutaneous and sublingual immunotherapy

Allergen-specific immunotherapy is a disease-modifying treatment that induces long-term T-cell tolerance. We sought to evaluate the role of circulating CXCR5+PD-1+ T follicular helper (cTFH) and T follicular regulatory (TFR) cells following grass pollen subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) and the accompanying changes in their chromatin landscape. Phenotype and function of cTFH cells were initially evaluated in the grass pollen-allergic (GPA) group (n= 28) and nonatopic healthy controls (NAC, n= 13) by mathematical algorithms developed to manage high-dimensional data and cell culture, respectively. cTFH and TFR cells were further enumerated in NAC (n= 12), GPA (n= 14), SCIT- (n= 10), and SLIT- (n= 8) treated groups. Chromatin accessibility in cTFH and TFR cells was assessed by assay for transposase-accessible chromatin sequencing (ATAC-seq) to investigate epigenetic mechanisms underlying the differences between NAC, GPA, SCIT, and SLIT groups. cTFH cells were shown to be distinct from TH2- and TH2A-cell subsets, capable of secreting IL-4 and IL-21. Both cytokines synergistically promoted B-cell class switching to IgE and plasma cell differentiation. Grass pollen allergen induced cTFH-cell proliferation in the GPA group but not in the NAC group (P< .05). cTFH cells were higher in the GPA group compared with the NAC group and were lower in the SCIT and SLIT groups (P< .01). Time-dependent induction of IL-4, IL-21, and IL-6 was observed in nasal mucosa following intranasal allergen challenge in the GPA group but not in SCIT and SLIT groups. TFR and IL-10+ cTFH cells were induced in SCIT and SLIT groups (all, P< .01). ATAC-seq analyses revealed differentially accessible chromatin regions in all groups. For the first time, we showed dysregulation of cTFH cells in the GPA group compared to NAC, SCIT, and SLIT groups and induction of TFR and IL-10+ cTFH cells following SCIT and SLIT. Changes in the chromatin landscape were observed following allergen-specific immunotherapy in cTFH and TFR cells.

Harnessing Activin A Adjuvanticity to Promote Antibody Responses to BG505 HIV Envelope Trimers.

T follicular helper (TFH) cells are powerful regulators of affinity matured long-lived plasma cells. Eliciting protective, long-lasting antibody responses to achieve persistent immunity is the goal of most successful vaccines. Thus, there is potential in manipulating TFH cell responses. Herein, we describe an HIV vaccine development approach exploiting the cytokine activin A to improve antibody responses against recombinant HIV Envelope (Env) trimers in non-human primates. Administration of activin A improved the magnitude of Env-specific antibodies over time and promoted a significant increase in Env-specific plasma cells in the bone marrow. The boost in antibody responses was associated with reduced frequencies of T follicular regulatory (TFR) cells and increased germinal center T follicular helper (GC-TFH) to TFR cell ratios. Overall, these findings suggest that adjuvants inducing activin A production could potentially be incorporated in future rational design vaccine strategies aimed at improving germinal centers, long-lived plasma cells, and sustained antibody responses.

T &lt;sub&gt;FR&lt;/sub&gt; Cells Inhibit Anti-Tumor Immunity and are Responsive to Immune Checkpoint Blockade

Immune checkpoint blockade (ICB) has shown remarkable clinical success in boosting anti-tumor immunity. However, the breadth of its cellular targets and specific mode of action remain elusive. We find that T follicular regulatory (TFR) cells are present in high numbers in multiple tumors, inhibit anti-tumor immunity and are responsive to ICB. TCR-seq data, trajectory analyses and adoptive transfer studies indicate intratumoral TREG to TFR cell conversion. When compared to TREG cells, TFR cells exhibited enhanced suppressive capacity. In syngeneic tumor models, anti-PD-1 treatment increased the number of tumor-infiltrating TFR cells. Conditional knockout of TFR cells or depletion of TFR cells with anti-CTLA-4 antibody prior to anti-PD-1 treatment, improved tumor control in mice. Notably, in a cohort of melanoma patients, treatment with anti-CTLA-4 followed by anti-PD-1 at progression was associated with better long-term survival outcomes than anti-PD-1 or anti-CTLA-4 monotherapy, anti-PD-1 followed by anti CTLA-4 at progression or concomitant combination therapy.

Satb1 deficiency licenses TFH-differentiation and Tertiary Lymphoid Structure formation in cancer

Abstract Tertiary Lymphoid Structures (TLS) are commonly identified in human tumors with improved outcome, but how they are orchestrated remains elusive. Here we show that silencing of the master genomic organizer Satb1 results in enhanced antigen-specific T Follicular Helper (TFH) differentiation. Increased TFH thereby promoted antigen-specific intra-tumoral CD19+B220+ B cell responses and spontaneous TLS assembly upon ovarian tumor challenge. Mechanistically, Satb1 deficiency drives increased TFH formation through de-repression of ICOS and PD-1. Accordingly, TGF-β1-driven downregulation of Satb1 licenses activated human CD4+ T-cells for enhanced antigen-specific T Follicular Helper (TFH) differentiation. Furthermore, Satb1 deficiency abrogates the generation of PD-1highCXCR5+Foxp3+ T Follicular Regulatory (TFR) cells during the TFH differentiation process. Importantly, functional TFH cell accumulation, in the absence of Satb1 specifically in CD4+ T cells, resulted in corresponding isotype-switched B cell responses and spontaneous formation of TLS, while B cell depletion accelerated malignant progression. Our results indicate that the formation of TLS in cancer depends on enhanced B cell responses driven by TFH cells generated through Satb1 down-regulation.

Expansion of T Helper Cell Subsets in Chronic Lymphocytic Leukemia Cell Co-Cultures with Nurselike Cells

Background: In secondary lymphatic organs (SLO), chronic lymphocytic leukemia (CLL) cells form characteristic pseudo-follicles, also called proliferation centers, in which proliferating CLL cells are in intimate contact with CD4+ T helper cells. Despite evidence for a co-evolution of CLL cells and counterpart T helper cells, the prevalence and dynamics of T cell subsets, such as T follicular helper cells (TFH), T regulatory helper cells (TRegs) and IL-17-producing T helper cells (Th17) has not been characterized in detail. The CLL nurselike cell (NLC) model recapitulates key cellular and molecular interactions between CLL cells and the microenvironment in SLO, based on functional and gene expression studies, and represents a valid in vitro model for the SLO microenvironment in CLL. To gain insight into the potential role of T cells in CLL SLO, we utilized the NLC model to characterize T helper cell subsets and their dynamics in NLC co-cultures. Methods and Results: First, we quantified CD4+ and CD8+ T cell subsets in fresh peripheral blood mononuclear cell (PBMC) samples from 14 patients and then placed 1x107 PBMCs/ml in culture to establish NLC. We rechecked the relative proportion of CD4+ and CD8+ T cells, as well as absolute T cell counts, and their viability after 3, 6, 9, 12 and 14 days in NLC co-culture conditions. Interestingly, throughout the 14 days of culture, the number of T helper cells remained stable when compared to baseline samples. Next, we characterized T helper cell subsets in 25 different CLL samples, comparing CD4+ T cell subsets in freshly isolated CLL PBMC with matched samples harvested after 14 days of NLC culture. Samples were stained with subset-specific fluorescence-labeled antibody combinations, and analyzed by flow cytometry. NLC co-culture resulted in a significant expansion of TFH and TReg cells. TFH absolute cell counts assessed by flow cytometry using counting beads, increased from 9.4±2.2/μl at baseline to 29.0±5.9/μl in NLC co-cultures (n=14, p=0.001) and TReg from 17.0±3.3/μl to 51.0±15.0/μl (n=14, p=0.027). In contrast, Th17 absolute cell counts declined after 14 days of culture from 113.0±21.0/μl to 68.0±13.0/μl (n=14, p=0.001). Moreover, TH2 cells declined from 42.0±7.4/μl to 30.0±8.2/μl (n=14, p=0.005). Next, we analyzed for changes in TFH subsets (TFH1, TFH2 and TFH17). When compared to TFH cells from CLL PBMC, NLC culture resulted in a relative increase in TFH2 from 17.0±2.4% to 26.0±1.7% (n=25, p=0.013), and in TFH17 from 12.0±1.6% to 21.0±2.7% (n=25, p=0.006) In contrast, TFH1 frequency decreased after 14 days of culture (54.0±3.5% versus 34.0±2.9%, n=25, p=0.001). T follicular regulatory (TFr) cells also increase under co-culture conditions from undetectable to 4.8±1.9% (n=25, p=0.025)(Figure1). Looking at the maturity of CD4+ cells we noted a relative increase of central memory cells from 42.0±3.2% to 50.0±3.2% (n=25, p=0.023), whereas effector memory cells decreased from 34.0±3.4% to 26.0±2.7% (n=25, p=0.009), the fraction of naïve CD4+ cells remained unchanged. Next, we assessed the activation status of co-inhibitory receptors on CD3+CD4+ cells. We found a significant relative increase in CD4+ T cells expressing PD1 and CTLA-4 after 14 days of culture. Additionally, the TFH and TReg subsets demonstrated a significantly higher CTLA-4 expression after culture while TReg cells also addressed an increase in PD1 frequency. Furthermore, we observed a significantly higher CD28 expression on TFH and TReg subsets after 14 days of co-culture. Following, to address the residence and migration capacity of T cells in NLC co-cultures, we analyzed the CD69 and CD62L expression. Our results revealed significantly higher expression of CD69 in NLC co-cultures, whereas CD62L levels remained unchanged. Conclusion: The expansion of TFH and TReg cells in NLC co-cultures suggests the selection and clonal expansion of T cells that may support and engage in crosstalk with CLL cells. Additionally, the expansion of TFr and TFH17 cells could reflect a milieu of immune tolerance establishing in NLC co-cultures. Ongoing TCR sequencing of serial CD4+ T cell samples (baseline versus 14 days under NLC conditions) will characterize changes of clonal architecture in the T helper cell compartment, and will further improve our understanding of co-evolution of CLL and T helper cells. Disclosures Wierda: Gilead Sciences: Research Funding; Juno Therapeutics: Research Funding; KITE pharma: Research Funding; Sunesis: Research Funding; Miragen: Research Funding; Janssen: Research Funding; Xencor: Research Funding; Acerta Pharma Inc: Research Funding; Pharmacyclics LLC: Research Funding; Genentech: Research Funding; AbbVie: Research Funding; GSK/Novartis: Research Funding; Oncternal Therapeutics Inc.: Research Funding; Cyclcel: Research Funding; Loxo Oncology Inc.: Research Funding. Burger:Aptose Biosciences, Inc: Research Funding; BeiGene: Research Funding; Gilead Sciences: Research Funding; AstraZeneca: Honoraria; Janssen Pharmaceuticals: Consultancy, Honoraria; Pharmacyclics, an AbbVie company: Research Funding.