Febrile temperature change modulates CD4 T cell differentiation via a TRPV channel-regulated Notch-dependent pathway

Fever is a conserved and prominent response to infection. Yet, the issue of how CD4 T cell responses are modulated if they occur at fever temperatures remains poorly addressed. We have examined the priming of naive CD4 T cells in vitro at fever temperatures, and we report notable fever-mediated modulation of their cytokine commitment. When naive CD4 T cells were primed by plate-bound anti-CD3 and anti-CD28 monoclonal antibodies at moderate fever temperature (39 °C), they enhanced commitment to IL4/5/13 (Th2) and away from IFNg (Th1). This was accompanied by up-regulation of the Th2-relevant transcription factor GATA3 and reduction in the Th1-relevant transcription factor Tbet. Fever sensing by CD4 T cells involved transient receptor potential vanilloid cation channels (TRPVs) since TRPV1/TRPV4 antagonism blocked the febrile Th2 switch, while TRPV1 agonists mediated a Th2 switch at 37 °C. The febrile Th2 switch was IL4 independent, but a γ-secretase inhibitor abrogated it, and it was not found in Notch1-null CD4 T cells, identifying the Notch pathway as a major mediator. However, when naive CD4 T cells were primed via antigen and dendritic cells (DCs) at fever temperatures, the Th2 switch was abrogated via increased production of IL12 from DCs at fever temperatures. Thus, immune cells directly sense fever temperatures with likely complex physiological consequences.

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Contact-dependent delivery of IL-2 by dendritic cells to CD4 T cells in the contraction phase promotes their long-term survival

Protein & Cell ◽

10.1007/s13238-019-00662-0 ◽

2019 ◽

Vol 11 (2) ◽

pp. 108-123

Author(s):

Dan Tong ◽

Li Zhang ◽

Fei Ning ◽

Ying Xu ◽

Xiaoyu Hu ◽

...

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

T Cell Activation ◽

Cd4 T Cells ◽

Cell Activation ◽

Cd4 T Cell ◽

Immune Memory ◽

Term Survival

Abstract Common γ chain cytokines are important for immune memory formation. Among them, the role of IL-2 remains to be fully explored. It has been suggested that this cytokine is critically needed in the late phase of primary CD4 T cell activation. Lack of IL-2 at this stage sets for a diminished recall response in subsequent challenges. However, as IL-2 peak production is over at this point, the source and the exact mechanism that promotes its production remain elusive. We report here that resting, previously antigen-stimulated CD4 T cells maintain a minimalist response to dendritic cells after their peak activation in vitro. This subtle activation event may be induced by DCs without overt presence of antigen and appears to be stronger if IL-2 comes from the same dendritic cells. This encounter reactivates a miniature IL-2 production and leads a gene expression profile change in these previously activated CD4 T cells. The CD4 T cells so experienced show enhanced reactivation intensity upon secondary challenges later on. Although mostly relying on in vitro evidence, our work may implicate a subtle programing for CD4 T cell survival after primary activation in vivo.

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African Green Monkey TRIM5α Restriction in Simian Immunodeficiency Virus-Specific Rhesus Macaque Effector CD4 T Cells Enhances Their Survival and Antiviral Function

Journal of Virology ◽

10.1128/jvi.03598-14 ◽

2015 ◽

Vol 89 (8) ◽

pp. 4449-4456 ◽

Cited By ~ 4

Author(s):

Sumiti Jain ◽

Matthew T. Trivett ◽

Victor I. Ayala ◽

Claes Ohlen ◽

David E. Ott

Keyword(s):

T Cells ◽

T Cell ◽

Rhesus Macaque ◽

Cd4 T Cells ◽

Cd4 T Cell ◽

T Cell Clones ◽

Cell Clones ◽

Immunodeficiency Virus ◽

Antiviral Function

ABSTRACTThe expression of xenogeneic TRIM5α proteins can restrict infection in various retrovirus/host cell pairings. Previously, we have shown that African green monkey TRIM5α (AgmTRIM5α) potently restricts both human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus mac239 (SIVmac239) replication in a transformed human T-cell line (L. V. Coren, et al., Retrovirology 12:11, 2015,http://dx.doi.org/10.1186/s12977-015-0137-9). To assess AgmTRIM5α restriction in primary cells, we transduced AgmTRIM5α into primary rhesus macaque CD4 T cells and infected them with SIVmac239. Experiments with T-cell clones revealed that AgmTRIM5α could reproducibly restrict SIVmac239replication, and that this restriction synergizes with an intrinsic resistance to infection present in some CD4 T-cell clones. AgmTRIM5α transduction of virus-specific CD4 T-cell clones increased and prolonged their ability to suppress SIV spread in CD4 target cells. This increased antiviral function was strongly linked to decreased viral replication in the AgmTRIM5α-expressing effectors, consistent with restriction preventing the virus-induced cytopathogenicity that disables effector function. Taken together, our data show that AgmTRIM5α restriction, although not absolute, reduces SIV replication in primary rhesus CD4 T cells which, in turn, increases their antiviral function. These results support priorin vivodata indicating that the contribution of virus-specific CD4 T-cell effectors to viral control is limited due to infection.IMPORTANCEThe potential of effector CD4 T cells to immunologically modulate SIV/HIV infection likely is limited by their susceptibility to infection and subsequent inactivation or elimination. Here, we show that AgmTRIM5α expression inhibits SIV spread in primary effector CD4 T cellsin vitro. Importantly, protection of effector CD4 T cells by AgmTRIM5α markedly enhanced their antiviral function by delaying SIV infection, thereby extending their viability despite the presence of virus. Ourin vitrodata support priorin vivoHIV-1 studies suggesting that the antiviral CD4 effector response is impaired due to infection and subsequent cytopathogenicity. The ability of AgmTRIM5α expression to restrict SIV infection in primary rhesus effector CD4 T cells now opens an opportunity to use the SIV/rhesus macaque model to further elucidate the potential and scope of anti-AIDS virus effector CD4 T-cell function.

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Telomere and ATM Dynamics in CD4 T-Cell Depletion in Active and Virus-Suppressed HIV Infections

Journal of Virology ◽

10.1128/jvi.01061-20 ◽

2020 ◽

Vol 94 (22) ◽

Author(s):

Sushant Khanal ◽

Qiyuan Tang ◽

Dechao Cao ◽

Juan Zhao ◽

Lam Nhat Nguyen ◽

...

Keyword(s):

Dna Damage ◽

T Cells ◽

T Cell ◽

Hiv Infection ◽

Cell Apoptosis ◽

Cd4 T Cells ◽

Molecular Mechanisms ◽

Cd4 T Cell ◽

Cell Aging

ABSTRACT CD4 T-cell depletion is a hallmark of HIV/AIDS, but the underlying mechanism is still unclear. We have recently shown that ataxia-telangiectasia-mutated (ATM) deficiency in CD4 T cells accelerates DNA damage, telomere erosion, and cell apoptosis in HIV-infected individuals on antiretroviral therapy (ART). Whether these alterations in ART-treated HIV subjects occur in vitro in HIV-infected CD4 T cells remains unknown. In this study, we employed a cellular model of HIV infection to characterize the mechanisms underlying CD4 T-cell destruction by analyzing the telomeric DNA damage response (DDR) and cellular apoptosis in highly permissive SupT1 cells, followed by the validation of our observations in primary CD4 T cells with active or drug-suppressed HIV infection. Specifically, we established an in vitro HIV T-cell culture system with viral replication and raltegravir (RAL; an integrase inhibitor) suppression, mimicking active and ART-controlled HIV infection in vivo. We demonstrated that HIV-induced, telomeric DDR plays a pivotal role in triggering telomere erosion, premature T-cell aging, and CD4 T-cell apoptosis or depletion via dysregulation of the PI3K/ATM pathways. This in vitro model provides a new tool to investigate HIV pathogenesis, and our results shed new light on the molecular mechanisms of telomeric DDR and CD4 T-cell homeostasis during HIV infection. IMPORTANCE The hallmark of HIV infection is a gradual depletion of CD4 T cells, with a progressive decline of host immunity. How CD4 T cells are depleted in individuals with active and virus-suppressed HIV infection remains unclear. In this study, we employed a cellular model of HIV infection to characterize the mechanisms underlying CD4 T-cell destruction by analyzing the chromosome end (telomere) DNA damage response (DDR) and cellular apoptosis in a T-cell line (highly permissive SupT1 cells), as well as in primary CD4 T cells with active or drug-suppressed HIV infection. We demonstrated that HIV-induced telomeric DDR plays a critical role in inducing telomere loss, premature cell aging, and CD4 T-cell apoptosis or depletion via dysregulation of the PI3K/ATM pathways. This study sheds new light on the molecular mechanisms of telomeric DDR and its role in CD4 T-cell homeostasis during HIV infection.

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Age-Related Induction of CD4+ T-Cell Unresponsiveness Is Reversible and Dependant of the Host’s Environment.

Blood ◽

10.1182/blood.v106.11.3925.3925 ◽

2005 ◽

Vol 106 (11) ◽

pp. 3925-3925

Author(s):

Pedro Horna ◽

Rahul Chavan ◽

Jason Brayer ◽

Ildefonso Suarez ◽

Eduardo M. Sotomayor

Keyword(s):

T Cells ◽

T Cell ◽

Transgenic Mice ◽

Cd4 T Cells ◽

Cd4 T Cell ◽

Cell Compartment ◽

Memory Phenotype ◽

Age Related ◽

And Function

Abstract A large number of CD4+ T-cells from either aged mice or humans display surface markers associated with an activated/memory phenotype. In spite of these changes however, these T-cells have a markedly decreased ability to proliferate and produce IL-2 in response to antigen stimulation in vitro. The cellular and molecular mechanisms involved in this age-related unresponsiveness of the CD4+ T-cell compartment remain poorly understood. Utilizing a well-established experimental system in which transgenic CD4+ T cells specific for a MHC class II restricted epitope of influenza hemagglutinin (HA) are adoptively transferred into non-transgenic recipients, we have previously elucidated important mechanisms involved in the induction and maintenance of CD4+ T-cell tolerance. Our studies were however limited to the analysis of T-cell function in lymphoma bearing young mice (4 to 10 weeks old). Here, we assessed the influence of the aged microenvironment in determining the phenotype and function of antigen-specific T-cells. CD4+ T-cells from young TCR transgenic mice (2 months old) were adoptively transferred into either old (20–24 months) or young (2 months old) non-transgenic mice. Two weeks later, clonotypic and non-clonotypic CD4+ T-cells were isolated from the spleens of these animals and their phenotype and function were determined in vitro. Reminiscent of the age-related changes observed within the normal CD4+ T-cell repertoire, young transgenic T-cells transferred into aged hosts have acquired an activated/memory phenotype but displayed a significant impairment in antigen-specific proliferation and IL-2 production in response to cognate antigen in vitro. These changes were not due to homeostatic proliferation of the transferred T-cells into the relatively lymphopenic aged host. To determine whether the changes observed in “aged” T-cells were reversible or not, we adoptively transfer old T-cells back into young hosts or into control old mice. While old transgenic T-cells transferred into an old environment remained fully unresponsive, the adoptive transfer of the same old T-cells into a young host restored their ability to proliferate and produce IL-2. Surprisingly, these “old” T-cells were able to produce significantly higher levels of IFN-gamma indicative of their memory/effector phenotype. Furthermore, young animals adoptively transferred with “aged” antigen-specific T-cells were now capable of rejecting A20 B-cell lymphomas expressing HA as a model tumor antigen (A20HA). Taking together, factor(s) present in the aged microenvironment are responsible for limiting the effector function of CD4+ T-cells that seem otherwise well equipped to become fully activated if the proper environment is provided (young microenvironment). The potential role of soluble suppressive factors as well as regulatory T-cells (Tregs) in the unresponsiveness observed in the T-cell compartment of aged hosts will be discussed.

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Genetic Regulation of Commitment to Interleukin 4 Production by a CD4+ T Cell–intrinsic Mechanism

Journal of Experimental Medicine ◽

10.1084/jem.188.12.2289 ◽

1998 ◽

Vol 188 (12) ◽

pp. 2289-2299 ◽

Cited By ~ 78

Author(s):

Mark Bix ◽

Zhi-En Wang ◽

Bonnie Thiel ◽

Nicholas J. Schork ◽

Richard M. Locksley

Keyword(s):

T Cells ◽

T Cell ◽

Cd4 T Cells ◽

Polymorphic Locus ◽

Cd4 T Cell ◽

Interleukin 4 ◽

Naive T Cells ◽

Naïve T Cells ◽

Intrinsic Mechanism

The dysregulated expression of interleukin 4 (IL-4) can have deleterious effects on the outcome of infectious and allergic diseases. Despite this, the mechanisms by which naive T cells commit to IL-4 expression during differentiation into mature effector cells remain incompletely defined. As compared to cells from most strains of mice, activated CD4+ T cells from BALB mice show a bias towards IL-4 production and T helper 2 commitment in vitro and in vivo. Here, we show that this bias arises not from an increase in the amount of IL-4 produced per cell, but rather from an increase in the proportion of CD4+ T cells that commit to IL-4 expression. This strain-specific difference in commitment was independent of signals mediated via the IL-4 receptor and hence occurred upstream of potential autoregulatory effects of IL-4. Segregation analysis of the phenotype in an experimental backcross cohort implicated a polymorphic locus on chromosome 16. Consistent with a role in differentiation, expression of the phenotype was CD4+ T cell intrinsic and was evident as early as 16 h after the activation of naive T cells. Probabilistic gene activation is proposed as a T cell–intrinsic mechanism capable of modulating the proportion of naive T cells that commit to IL-4 production.

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Trans-Ned 19-Mediated Antagonism of Nicotinic Acid Adenine Nucleotide—Mediated Calcium Signaling Regulates Th17 Cell Plasticity in Mice

Cells ◽

10.3390/cells10113039 ◽

2021 ◽

Vol 10 (11) ◽

pp. 3039

Author(s):

Mikołaj Nawrocki ◽

Niels Lory ◽

Tanja Bedke ◽

Friederike Stumme ◽

Björn-Phillip Diercks ◽

...

Keyword(s):

T Cells ◽

Cell Differentiation ◽

T Cell ◽

Mouse Model ◽

Nicotinic Acid ◽

Cd4 T Cells ◽

Th17 Cells ◽

T Cell Differentiation ◽

Cd4 T Cell

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca2+ mobilizing agent and its inhibition proved to inhibit T-cell activation. However, the impact of the NAADP signaling on CD4+ T-cell differentiation and plasticity and on the inflammation in tissues other than the central nervous system remains unclear. In this study, we used an antagonist of NAADP signaling, trans-Ned 19, to study the role of NAADP in CD4+ T-cell differentiation and effector function. Partial blockade of NAADP signaling in naïve CD4+ T cells in vitro promoted the differentiation of Th17 cells. Interestingly, trans-Ned 19 also promoted the production of IL-10, co-expression of LAG-3 and CD49b and increased the suppressive capacity of Th17 cells. Moreover, using an IL-17A fate mapping mouse model, we showed that NAADP inhibition promotes conversion of Th17 cells into regulatory T cells in vitro and in vivo. In line with the results, we found that inhibiting NAADP ameliorates disease in a mouse model of intestinal inflammation. Thus, these results reveal a novel function of NAADP in controlling the differentiation and plasticity of CD4+ T cells.

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Aberrant Cathepsin S Induces a Supportive Immune Microenvironment in Follicular Lymphoma

Blood ◽

10.1182/blood-2019-122663 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 657-657

Author(s):

Johannes Adrian Hildebrand ◽

Deepak Bararia ◽

Sebastian Stolz ◽

Sarah Haebe ◽

Stefan Alig ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Cd4 T Cells ◽

Research Funding ◽

Clinical Course ◽

Cd4 T Cell ◽

Immune Microenvironment ◽

Mhc Ii ◽

Autocatalytic Cleavage

The highly variable clinical course of follicular lymphoma (FL) is determined by the molecular heterogeneity of the tumor cells and complex interactions with the microenvironment. Here, we provide biochemical, structural, functional and clinical evidence that aberrant Cathepsin S (CTSS) activity induces a supportive immune microenvironment in FL. By targeted DNA sequencing of 305 diagnostic FL biopsies, we identified somatic mutations of CTSS in 8% of cases (24/305), mostly clustered at Y132 (19/24) converting Y to D (16/19). A subset of CTSS Y132 mutations (N=5) occurred at lower variant allele frequencies (5-10%), indicating subclonality. Another 13% of FL had CTSS amplifications (37/286). CTSS Y132 mutations and CTSS amplifications were mutually exclusive. In a cohort of 51 FL, CTSS amplifications were associated with higher CTSS expression (P=0.05). Of note, a subset of FL without CTSS amplifications also had higher CTSS expression, suggesting additional mechanisms of transcriptional dysregulation. CTSS is a cysteine protease that is highly expressed in endolysosomes of antigen presenting cells and malignant B-cells. CTSS is involved in proteolytical processing of antigenic peptides for presentation on MHC-II to be recognized by antigen specific CD4+ T-cells. CTSS is synthesized as an inactive zymogen, which is converted to its active form by autocatalytic cleavage of the autoinhibitory propeptide (pro-CTSS). We used CRISPR/Cas9 to introduce CTSS Y132D into Karpas422, a B-cell lymphoma cell line that harbors the FL hallmark translocation t(14;18). Single-cell derived Y132D mutant clones showed >3-fold higher ratios of active CTSS to pro-CTSS (N=4, P=0.0003). Immunoprecipitated CTSS Y132D had >3-fold higher in vitro substrate cleavage activity compared to CTSS wild type (WT) (N=6, P=0.001). We purified pro-CTSS WT and Y132D and assayed their in vitro autocatalytic cleavage over time. The time required to convert 50% of pro-CTSS decreased from 17 minutes for WT to 11 minutes for Y132D (N=3, P=0.04). In contrast, purified active CTSS WT and Y132 had similar in vitro cleavage activities. Molecular dynamics simulations showed that the Y132D mutation shortens the distances by ~2Å between the catalytic triad of active CTSS (C139, H278, N298) and a stretch of amino acids from the proform (L80, G81, D82, S94), which may facilitate intramolecular cleavage. By mass spectrometry we could indeed detect novel intermediate-sized CTSS fragments. Thus, Y132D does not increase the activity of the mature enzyme but is a gain-of-function mutation by accelerating the conversion from pro-CTSS to catalytically active CTSS. CD74 (invariant chain) is a physiologic CTSS substrate that plays critical roles in the assembly, trafficking and stabilization of peptide-free MHC-II. CTSS cleaves CD74, thereby allowing binding and presentation of antigens on MHC-II to antigen specific CD4+ T-cells. We could show that CTSS Y132D enhanced CD74 cleavage in Karpas422 cells. We then tested the impact of CTSS on antigen specific CD4+ T-cell activation in co-culture assays. CTSS knock-out lymphoma cells were broadly incapable of activating CD4+ T-cells. Overexpression of CTSS WT activated CD4+ T-cells more efficiently compared to empty vector control. CTSS Y132 had the highest capacity to stimulate antigen specific CD4+ T-cell responses. Furthermore, in primary FL biopsies (N=51) CTSS Y132 mutations had gene expression profiles linked with antigen-processing and chemokine perturbation, including CXCL13, a B-cell chemoattractant produced by activated CD4+ T-follicular helper cells. Lastly, we aimed to correlate CTSS aberrations with clinical outcome in patients who received standard immunochemotherapy (R-CHOP) for advanced FL (N=51 with available CTSS mutation and gene expression data). Compared to all other patients (N=34), patients with CTSS Y132 mutations or CTSS overexpression (N=17) had longer failure free survival (P=0.012) and overall survival (P=0.041). In summary, we propose that aberrant CTSS activity - even if only present in a FL subclone - can elicit a CD4+ T-cell driven tumor-promoting immune response, which could be amplified within the microenvironment via pro-inflammatory and chemotactic cytokines and substantially impact the biology and clinical course of the disease. Thus, aberrant CTSS activity is a promising biomarker and therapeutic target in FL and potentially also other tumors. Disclosures Klapper: Roche, Takeda, Amgen, Regeneron: Honoraria, Research Funding. Hiddemann:Bayer: Research Funding; Roche: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Vector Therapeutics: Consultancy, Honoraria. Steidl:Juno Therapeutics: Consultancy; Bristol-Myers Squibb: Research Funding; Nanostring: Patents & Royalties: Filed patent on behalf of BC Cancer; Roche: Consultancy; Tioma: Research Funding; Seattle Genetics: Consultancy; Bayer: Consultancy. Kridel:Gilead Sciences: Research Funding. Weinstock:Celgene: Research Funding; Verastem Oncology: Research Funding. Weigert:Novartis: Research Funding; Roche: Research Funding.

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Regulatory dendritic cells program generation of interleukin-4–producing alternative memory CD4 T cells with suppressive activity

Blood ◽

10.1182/blood-2010-05-285494 ◽

2011 ◽

Vol 117 (4) ◽

pp. 1218-1227 ◽

Cited By ~ 11

Author(s):

Xiongfei Xu ◽

Zhenhong Guo ◽

Xueyu Jiang ◽

Yushi Yao ◽

Qiangguo Gao ◽

...

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Cd4 T Cells ◽

Cd4 T Cell ◽

Interleukin 4 ◽

Delayed Type Hypersensitivity ◽

Regulatory Function

Abstract The heterogeneity and mechanisms for the generation of CD4 memory T (CD4 Tm) cells remain elusive. Distinct subsets of dendritic cells (DCs) have been found to regulate a distinct T-helper (Th)–cell subset differentiation by influencing cytokine cues around CD4 T cells; however, whether and how the regulatory DC subset can regulate Tm-cell differentiation remains unknown. Further, there is no ideal in vitro experimental system with which to mimic the 3 phases of the CD4 T-cell immune response (expansion, contraction, memory generation) and/or to culture CD4 Tm cells for more than a month. By analyzing CD4 T cells programmed by long-term coculture with regulatory DCs, we identified a population of long-lived CD4 T cells with a CD44hiCD62L−CCR7− effector memory phenotype and rapid, preferential secretion of the Th2 cytokines interleukin-4 (IL-4), IL-5, IL-10, and IL-13 after antigenic stimulation. These regulatory DC-programmed Tm cells suppress CD4 T-cell activation and proliferation in vitro via IL-10 and inhibit the delayed-type hypersensitivity response once infused in vivo. We also identify their natural counterpart, which is up-regulated by regulatory DC transfusion and negatively regulates the recall response in vivo. Different from interferon-γ–producing conventional Tm cells, these IL-4–producing CD4 Tm cells act as alternative Tm cells with a regulatory function, suggesting a new way of negative immune regulation by memory T cells.

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Two Novel WT-1 Derived Peptides Induce CD4+ peptide–specific T Cell Proliferation in Patients with Myelodysplastic Syndrome (MDS)

Blood ◽

10.1182/blood.v112.11.5432.5432 ◽

2008 ◽

Vol 112 (11) ◽

pp. 5432-5432

Author(s):

Monica Bocchia ◽

Micaela Ippoliti ◽

Marzia Defina ◽

Rosaria Crupi ◽

Maristella Tassi ◽

...

Keyword(s):

Cell Proliferation ◽

T Cells ◽

T Cell ◽

T Lymphocytes ◽

Cytotoxic Activity ◽

Cd4 T Cells ◽

Cd4 T Cell ◽

T Cell Proliferation ◽

Wt1 Protein

Abstract The Wilms tumor gene WT1 is overexpressed in hematopoietic malignancies such as Myelodysplastic syndromes and leukemias and the WT1 protein was demonstrated to be an attractive target antigen for an immunotherapeutic approach to these diseases. Most of the efforts have been focused to the search for immunogenic peptides suitable for inducing cytotoxic T lymphocytes (CTLs) and to less extent for CD4+ T lymphocytes with potential cytotoxic activity. On this matter, in our previous experience with a p210-derived peptide vaccine developed for chronic myeloid leukemia patients with minimal residual disease, the main immune and therapeutic effect observed after vaccinations appeared to be mediated by peptide-specific CD4+ T cells induced by the longest peptide (25 mer) included in our vaccine. CML-peptide specific T cells were found to be either CD4+/perforin+ or CD4+/CD25+/Foxp3+ and we recently showed their direct cytotoxicity against a CML cell line. Thus to pursue a vaccine strategy mainly devoted to a similar CD4+ T cell immune response, we screened WT1 protein through Syfpeithi database to identify original peptides with a suitable length (23–25 amino acids) to be processed by several HLA class II molecules and to induce a strong CD4+ T cell stimulation. Additionally, in order to maximize the immunogenic potential of the novel peptides, we focused our attention on areas of the protein with known CTLs/CD4 T cells immunogenic epitopes. We identified two peptides that fulfilled these requirements: SEPQQMGSDVRDLNALLPAVPSLGG (WT1-iso5 64–88) which includes 5 amino acid from the alternative splicing derived isoform 5 of WT1 and the first 20 aa of “canonical” WT1 sequence and RPFMCAYPGCNKRYFKLSHLQMHSR (WT1321–345). Both 25mer peptides showed strong HLA binding properties for HLA-DRB1*0101, HLADRB1* 0401, HLA-DRB1*0701, HLA-DRB1*1101, HLA-DRB1*1501 and HLADRB1* 0301( DR17). We first tested them in vitro for their capability to induce peptide-specific CD4+ T cells. Briefly, CD4+ T cells freshly isolated from PBMC were cultured for 21 days in 5% AB human serum media while undergoing to 3 rounds of stimulation with autologous CD14+ cells and both WT1-iso5 64–88 and WT1 321–345 peptides at 20μg/ml in the presence of IL-15. This in vitro stimulation was performed in 3 normal subjects and in 3 MDS patients with high levels of bone marrow WT1 transcript (2 patients presenting a low-International Prognostic Scoring System (IPSS) refractory anemia (RA) and 1 with intermediate IPSS RA). In all 3 healthy donors tested, both peptides were able to induce peptide specific CD4+ T cell proliferation as measured by standard 3HThymidine assay, with a stimulation index (SI) ranging from 2.0 to 2.5 regardless of their HLA-DR phenotype ( SI= cpm CD4+ T cells plus test peptides/CD4+ T cell alone or CD4+ T cells plus control peptides; peptide-specific T cell proliferation was considered positive for SI≥2). Similar results were obtained in all 3 MDS patients in which WT1-iso5 64–88 and WT1 321–345 induced peptide-specific CD4+ T cell proliferation with a SI value of 2.5, 2.9 and 3.0 respectively. In conclusion the present study identified 2 novel WT1-derived 25 mer peptides which were able to easily induce in vitro a peptide-specific CD4+ T cell response in MDS patients. WT1-specific CD4+ T cells proliferated with similar SI values in normal donors and in WT1 positive MDS patients, the latter being highly exposed to this antigen and thus potentially tolerant to it. A possible cytotoxic activity of these WT1-specific CD4+ T cells is under evaluation and in vivo vaccinations of low-intermediate IPSS MDS patients with these peptides are planned.

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