Functional analysis of T-cell antigen 4-1BB in activated intestinal intra-epithelial T lymphocytes

4-1BB and cytokines trigger human NK, γδ T, and CD8+ T cell proliferation and activation, but are not required for their effector functions

INTRODUCTION

This study was designed to compare the costimulatory molecules and cytokines required to trigger the proliferation and activation of natural killer (NK), γδ T, and CD8+ T cells, and gain in-depth insight into the mechanisms shifting tolerance to immunity.

METHODS

K562-derived artificial antigen-presenting cells (aAPCs); that is, K562 forced to express CD86 and 4-1BBL costimulatory receptors, in the presence of cytokines, were used to mimic dendritic cells (DCs) and provide signals to support the proliferation and activation of NK, γδ T, and CD8+ T cells.

RESULTS

Three signals are required to trigger optimal proliferation in MART-1-specific CD8+ T cells: activation of T-cell receptors (TCRs) by the major histocompatibility complex (MHC) I/peptide complexes (signal 1); 4-1BB engagement (signal 2); and IL-15 and IL-21 receptor co-signaling (signal 3). NK and γδ T cell proliferation also require three signals, but the precise nature of signal 1 involving cell-to-cell contact was not determined. Once they become effectors, only signal 1 determines the sensitivity or resistance of the target cells to cytolysis by killer lymphocytes. When freshly purified, none had effector functions, except the NK cells, which could be activated by CD16 engagement.

CONCLUSIONS

Therefore, lymphocytes committed to kill are produced as inactive precursors, and the license to kill is delivered by three signals, allowing for extensive proliferation and effector function acquisition. This data challenges the paradigm of anergy and supports the danger signal theory originally proposed by Polly Matzinger, which states that killer cells are tolerant by default, thereby protecting the mammalian body from autoimmunity.

Characterization of clinical grade CD19 chimeric antigen receptor T cells produced using automated CliniMACS Prodigy system

BACKGROUND

Chimeric antigen receptor (CAR) T-cell therapy is highly effective for treating acute lymphoblastic leukemia and non-Hodgkin's lymphoma with high rate complete responses. However, the broad clinical application of CAR T-cell therapy has been challenging, largely due to the lack of widespread ability to produce and high cost of CAR T-cell products using traditional methods of production. Automated cell processing in a closed system has emerged as a potential method to increase the feasibility of producing CAR T cells locally at academic centers due to its minimal reliance on experienced labor, thereby making the process less expensive and more consistent than traditional methods of production.

METHOD

In this study, we describe the successful production of clinical grade CD19 CAR T cells using the Miltenyi CliniMACS Prodigy Automated Cell Processor at University of Colorado Anschutz Medical Campus in a rapid manner with a high frequent CD19 CAR expression.

RESULTS

The final CAR T-cell product is highly active, low in immune suppression, and absent in exhaustion. Full panel cytokine assays also showed elevated production of Th1 cytokines upon IL-2 stimulation when specifically killing CD19+ target cells.

CONCLUSION

These results demonstrate the feasibility of producing CAR T cells locally in a university hospital setting using automated cell processor for future clinical applications.

Involvement of Ly6C, 4-1BB, and KLRG1 in the activation of lamina propria lymphocytes in the small intestine of sanroque mice

Roquin is an E3 ligase that regulates mRNA stability. Mice with a mutation in the Rc3h1 gene and Roquin protein, referred to as Roquin^san/san or sanroque mice, develop broad-spectrum chronic inflammatory conditions and autoimmune pathologies. Our laboratory recently reported that sanroque mice also develop extensive inflammation that is localized in the small intestine but is rare in the colon. Here, we demonstrate that small intestinal intraepithelial lymphocytes (IELs) are present in the epithelium of sanroque mice but that cell recoverability is low using standard extraction techniques even though lamina propria lymphocytes (LPLs) can be recovered in normal numbers. In studies aimed at characterizing T cell costimulatory markers and activation molecules on LPLs in sanroque mice, we identified Ly6C and 4-1BB (CD137) as being expressed at elevated levels on sanroque small intestinal LPLs, and we show that both of those subsets, in conjunction with cells expressing the KLRG1 T cell activation molecule, are sources of IL-17A, IFN-γ, and TNFα. TNFα was primarily produced by 4-1BB+, KLRG1-cells, but was also made by some 4-1BB-, KLRG1-cells, and 4-1BB-, KLRG1+ cells. These findings collectively suggest that the small intestinal inflammatory response in sanroque mice is driven, at least in part, by LPL activation through Ly6C and 4-1BB signaling, and they provide further evidence in support of using the sanroque mouse as an animal model of chronic small intestinal inflammation.

Cell surface signaling molecules in the control of immune responses: a tide model

A large numbers of cell surface signaling molecules (CSSMs) have been molecularly identified and functionally characterized in recent years and, via these studies, our knowledge in the control of immune response has increased exponentially. Two major lines of evidence emerge. First, the majority of immune cells rely on one or few CSSMs to deliver a primary triggering signal to sense their environment, leading to initiation of an immune response. Second, both costimulatory CSSMs that promote the response, and coinhibitory CSSMs that inhibit the response, are required to control direction and magnitude of a given immune response. With such tight feedback, immune responses are tuned and returned to baseline. These findings extend well beyond our previous observation in the requirement for lymphocyte activation and argue a revisit of the traditional "two-signal model" for activation and tolerance of lymphocytes. Here we propose a "tide" model to accommodate and interpret current experimental findings.

T-cell activation in the intestinal mucosa

The vast majority of peripheral T cells exist as resting lymphocytes until a signal for activation has been received. In response to antigen, this activation involves ligation of the T-cell receptor (TCR) and signal transmission through the CD3 complex, which then initiates a cascade of intracellular events that lead to the expression of genes used in T-cell activation. T-cell activation also requires soluble mediators in the form of cytokines and chemokines that regulate the process in both positive and negative ways, and costimulatory signals received in conjunction with TCR/CD3 signaling are important in the activation of T cells. Unlike T cells in other peripheral immune compartments, small and large intestinal intraepithelial lymphocytes (IELs) bear some but not all properties of activated T cells, suggesting that they constitute a large population of 'partially activated' effector cells. Thus, regulation of the IEL activation process must be held in tight check, yet it must be ready to respond to foreign antigen rapidly and effectively. We discuss how costimulatory molecules may hold the key to controlling IEL activation through a multiphase process beginning with cells that have already entered into the early stage of activation.

Exploiting 4-1BB Costimulation for Enhancing Antiviral Vaccination

4-1BB, a member of the tumor necrosis factor receptor (TNFR) superfamily, is emerging as an important costimulatory molecule, particularly in the regulation of CD8(+) T cell responses. Costimulation through 4-1BB, such as by utilizing agonistic anti-4-1BB monoclonal antibodies, has been well studied in various tumor models. However, 4-1BB is also an important regulator of antiviral CD8(+) T cell responses. This review summarizes these findings and describes how 4-1BB is beginning to be exploited in terms of boosting antiviral vaccine responses.

CD70+ antigen-presenting cells control the proliferation and differentiation of T cells in the intestinal mucosa

One unresolved issue in gut immunity is how mucosal T lymphocytes are activated and which antigen-presenting cell (APC) is critical for the regulation of this process. We have identified a unique population of APCs that is exclusively localized in the lamina propria. These APCs constitutively expressed the costimulatory molecule CD70 and had antigen-presenting functions. After oral infection of mice with Listeria monocytogenes, proliferation and differentiation of antigen-specific T cells occurred in the gut mucosa in situ and blockade of CD70 costimulation abrogated the mucosal T cell proliferation and effector functions. Thus, a potent CD70-dependent stimulation via specialized tissue-specific APCs is required for the proliferation and differentiation of gut mucosal T cells after oral infection.

T-cell activation in the curious world of the intestinal intraepithelial lymphocyte

In conventional terms, when T cells encounter appropriate stimuli, they are induced to undergo molecular and physical changes that confer upon them a state of activation. Once initiated, activation generally results in a state of full T-cell responsiveness in an all-or-none manner. Uniquely, however, the intestinal intraepithelial lymphocytes (IELs) bear features that are decidedly different from those of T cells located throughout other immunological compartments in that they exhibit some but not all properties of activated T cells, yet they can be induced to move further into activation provided appropriate costimulatory signals have been received. IEL costimulatory molecules some of which are constitutively expressed, whereas others are upregulated following T-cell receptor (TCR)/CD3 stimulation appear to hold the key to determining the nature and magnitude of the activational process. A system of activation such as this in the intestine would be expected to have great immunological protective value for the host because it would provide an untrammeled process of T-cell activation at a barrier site where the level of antigen exposure is consistently high. Clearly, however, mechanisms must be in place to insure that the IEL activation process is not inadvertently breached. These and other issues central to the operational workings of the intestinal immune system are elaborated in this article, and a model is presented in which IEL activation can be viewed as a layered, three-stage activational process.

4-1BB and OX40 stimulation enhance CD8 and CD4 T-cell responses to a DNA prime, poxvirus boost vaccine

4-1BB (CD137) is a tumour necrosis factor receptor (TNFR) family member, expressed primarily on CD8 T cells after activation. Signalling through 4-1BB has been reported to enhance CD8 T-cell expansion and to protect activated CD8 T cells from death, resulting in an enlarged memory population. Although stimulating 4-1BB has been shown to significantly improve the immune response to weak immunogens such as tumours, little is known about its effect on the CD8 T-cell response to a powerful viral vector such as vaccinia. To test 4-1BB's ability to improve the murine CD8 T cell response to a DNA prime, poxvirus boost vaccine, similar to those used for human immunodeficiency virus and simian immunodeficiency virus vaccines, we administered 4-1BB agonist antibody at the time of the poxvirus boost. 4-1BB stimulation increased the number of functional memory CD8 T cells by two- to fourfold. However, we saw a similar enhancement at the peak of the response and in the memory phase, thus we found no evidence in the context of virus infection that 4-1BB stimulation could increase the percentage of CD8 T cells that survive the acute activation phase to become memory cells. OX40 (CD134) is an analogous TNFR family member expressed primarily on activated CD4 T cells. OX40 stimulation increased the number of antigen-specific CD4 T cells approximately threefold. Stimulating both 4-1BB and OX40 enhanced the CD8 T-cell response more than 4-1BB alone. Thus stimulating these receptors can improve the response to a powerful virus vector, and may be useful in vaccine development.

Relative abilities of 4-1BB (CD137) and CD28 to co-stimulate the response of cytokine deflected Th1 and Th2 cells

In this report we show that allo-stimulated naïve CD4+ cells when cultured in IL-2, IFN-gamma, IL-12 and anti-IL-4 differentiated into Th1 cells expressing very low amounts of 4-1BB molecule, but high amounts of CD28. By contrast, allo-stimulated naive CD4+ cells cultured in the presence of exogenous IL-2, IL-10, IL-4 and anti-INF-gamma evolved into Th2 expressing high amounts of both 4-1BB and CD28. Various Th1/Th2 clones derived from limiting dilution also exhibited similar expression pattern. This differential expression of co-stimulatory molecules on Th subsets account for the ability of 4-1BB to trigger both the proliferation and production of IL-4 by Th2 cells only and for the ability of CD28 to trigger proliferation and typical secretion in both Th1 and Th2 cells.

Differential expression and costimulatory effect of 4-1BB (CD137) and CD28 molecules on cytokine-induced murine CD8(+) Tc1 and Tc2 cells

In this study we report that the relative expression of 4-1BB (CD137) and CD28 molecules can differentially be modulated on CD8(+) T cells by combinations of various cytokines and anti-cytokine antibodies. During allostimulation of naive CD8(+) T cells in the presence of IL-2, IFN-gamma, IL-12, and anti-IL-4, they evolved into IL-2, IFN-gamma-producing Tc1 cells and showed inability to upregulate 4-1BB expression but not CD28. On the other hand, the Tc2 cells, generated in the presence of allogeneic APCs, IL-2, IL-10, IL-4, and anti-IFN-gamma, demonstrated intact and elevated 4-1BB and CD28 molecules. Activation of Tc1 and Tc2 cells with anti-CD3 and plate-bound anti-4-1BB and anti-CD28 mAbs revealed differential proliferative and cytokine secretory patterns. The 4-1BB signaling in the context of anti-CD3 as first signal led to the increased secretion of IL-4 by the Tc2 cells and not by Tc1 cells, while CD28 triggering produced IL-4 from Tc2 and IL-2 and IFN-gamma from Tc1 cells. Flow cytometric analysis of cell surface expression on Tc1 and Tc2 cells strengthened our observation that 4-1BB expression but not CD28 is poorly expressed on Tc1 cells. Both of the polarized CD8(+) T cell subsets exhibited comparable cytotoxic abilities and perforin and granzyme expression. The regeneration of 4-1BB expression is possible on Tc1 cells when back cultured in a Tc2 cytokine environment, but its expression could not be significantly altered on the Tc2 population unless IL-12 was included in the system.

Antibodies to TR2 (Herpesvirus Entry Mediator), a New Member of the TNF Receptor Superfamily, Block T Cell Proliferation, Expression of Activation Markers, and Production of Cytokines

TR2 (TNFR-related 2) is a recently identified member of the TNFR family with homology to TNFRII. We have demonstrated previously that TR2 mRNA is expressed in resting and activated human T cells and that TR2-Ig partially inhibits an allogeneic mixed leukocyte proliferation response. We now characterize TR2 further by the use of specific mAbs. Flow-cytometry analysis using TR2 mAbs confirmed that resting PBL express high levels of cell surface TR2, and that TR2 is widely expressed on all freshly isolated lymphocyte subpopulations. However, stimulation of purified T cells with either PHA or PHA plus PMA resulted in decreased surface expression within 48 h of activation before returning to resting levels at 72 h. TR2 mAbs inhibited CD4+ T cell proliferation in response to stimulation by immobilized CD3 or CD3 plus CD28 mAbs. Assay of culture supernatants by ELISA showed inhibition of TNF-α, IFN-γ, IL-2, and IL-4 production, which, for IL-2 and TNF-α was also confirmed by intracellular cytokine staining. Furthermore, expression of activation markers on CD4+ T cells, including CD25, CD30, CD69, CD71, and OX40 (CD134), was inhibited. TR2 mAbs inhibited proliferation in a three-way MLR, and a response to soluble recall Ag, tetanus toxoid. In conclusion, these results suggest that TR2 is involved in the activation cascade of T cell responses and TR2 mAbs prevent optimal T cell proliferation, cytokine production, and expression of activation markers.

Characterization of human homologue of 4-1BB and its ligand

The human homologue of 4-1BB (H4-1BB) cDNA was isolated from PMA plus ionomycin-treated human peripheral T-cell cDNA libraries. The amino acid sequence deduced from the nucleotide sequence showed that the protein is composed of 255 amino acids with 2 potential N-linked glycosylation sites. The molecular weight of its protein backbone is calculated to be 27 kDa. The H4-1BB contains features such as signal sequence and transmembrane domain, indicating that it is a receptor protein. This protein showed 60% identity of amino acid sequence to mouse 4-1BB. In the cytoplasmic domain there are 5 regions of amino acid sequences conserved from mouse to human, indicating that these residues might be important in the 4-1BB function. H4-1BB mRNA was detected in unstimulated peripheral blood T cells and was inducible in T-cell lines such as Jurkat and CEM. H4-1BB-AP, a fusion protein between the H4-1BB extracellular domain and alkaline phosphatase, was used to identify the ligand for the H4-1BB. Although the H4-1BB ligand was detected in both T and B cells of human peripheral blood, the ligand was preferentially expressed in primary B cells and B-cell lines. Daudi, a B-cell lymphoma, was one of the B-cell lines that carried a higher number of ligands. Scatchard analysis showed that the Kd = 1.4 x 10(9) M and the number of ligands in Daudi cell was 4.2 x 10(3).