Enhanced T-cell activation and T-cell-dependent IL-2 production by CD83+, CD25high, CD43high human monocyte-derived dendritic cells

Human Cytomegalovirus pUL11, a CD45 Ligand, Disrupts CD4 T Cell Control of Viral Spread in Epithelial Cells

Human cytomegalovirus (HCMV) encodes numerous immunomodulatory genes that facilitate its persistence. Previously described mechanisms by which HCMV avoids T cell control typically involve evasion of detection by infected cells. Here, we show that the virus also inhibits T cells directly via an interaction between the pUL11 glycoprotein on infected cells and the CD45 phosphatase on T cells. The antiviral functions of CD4 T cells are impaired as a result of this interaction, largely via induced interleukin 10 (IL-10) secretion in the CD4 T cell central memory compartment, resulting in enhanced viral spread. This establishes CD45 as an inhibitory receptor that regulates antiviral T cell functions and has parallels with the manipulation of natural killer (NK) cells by HCMV. By coculturing donor T cells with HCMV-infected epithelial cells, we observed that CD4 T cells can respond to epithelial cell antigen presentation and can control HCMV spread via cytolytic and cytokine-dependent mechanisms. pUL11 impairs both mechanisms. We showed that pUL11-induced IL-10 secretion requires IL-2, mTOR, and T cell receptor signaling. This characterization of the effects of the pUL11-CD45 interaction may allow for the development of new antiviral therapies and treatments for inflammatory disorders. IMPORTANCE Human cytomegalovirus (HCMV) is adept at avoiding its host's immune defenses, both by evading detection and by directly inhibiting immune cells. This can lead to a loss of control of the infection, and dangerous disease can result, particularly in cases in which an individual's immune system is immature, weak, or suppressed. T cells form a crucial part of the response to HCMV and are used in cellular HCMV therapies. We show that an interaction between a viral glycoprotein (pUL11) and a T cell surface receptor (CD45) impairs T cell memory functions and allows for increased viral spread. This defines a new immunomodulatory strategy for the virus as well as a new T cell regulatory mechanism. These results are important, as they increase our understanding of how T cells function and how HCMV disrupts them. This will allow for the development of new antiviral therapies that restore T cell functions and indicates a new target for controlling pathological T cell disorders.

Interleukin-2 signals converge in a lymphoid-dendritic cell pathway that promotes anticancer immunity

Tumor-infiltrating dendritic cells (DCs) correlate with effective anticancer immunity and improved responsiveness to anti-PD-1 checkpoint immunotherapy. However, the drivers of DC expansion and intratumoral accumulation are ill-defined. We found that interleukin-2 (IL-2) stimulated DC formation through innate and adaptive lymphoid cells in mice and humans, and this increase in DCs improved anticancer immunity. Administration of IL-2 to humans within a clinical trial and of IL-2 receptor (IL-2R)-biased IL-2 to mice resulted in pronounced expansion of type 1 DCs, including migratory and cross-presenting subsets, and type 2 DCs, although neither DC precursors nor mature DCs had functional IL-2Rs. In mechanistic studies, IL-2 signals stimulated innate lymphoid cells, natural killer cells, and T cells to synthesize the cytokines FLT3L, CSF-2, and TNF. These cytokines redundantly caused DC expansion and activation, which resulted in improved antigen processing and correlated with favorable anticancer responses in mice and patients. Thus, IL-2 immunotherapy-mediated stimulation of DCs contributes to anticancer immunity by rendering tumors more immunogenic.

Safety and immunogenicity of HBAI20 Hepatitis B vaccine in healthy naïve and nonresponding adults

Approximately 5% of the healthy adult population respond inadequately to the commercial recombinant hepatitis B vaccines. As the recombinant vaccines all have an aluminium-based adjuvant, we tried to enhance the immune response by adding a cytokine-based adjuvant. This new adjuvant AI20, containing 20 μg recombinant human IL-2 attached to 20 μg aluminium hydroxide, was added to HBVaxPro©-10 μg (HBAI20). In a double-blind randomized controlled trial (RCT), 24 naïve subjects were randomized to receive either HBAI20 or commercial HBVaxPro©-10 μg vaccine. In an open-label study, 10 nonresponders received HBAI20 vaccine. All participants received 3 vaccinations (0, 1 and 6 months). In the RCT, the occurrence of any adverse events or severe events was similar between the trial arms. At month 7, all naïve participants were seroprotected; moreover, 92% in the HBAI20 group had protective antibodies 10 days after the second vaccination vs 58% in the HBVaxPro©-10 μg group, P = .16. In the open-label study, no serious adverse events were noted. The HBAI20 vaccine was able to elicit protective anti-HBs titres in 90% of nonresponders, 1 month after the third vaccination. According to these results, the new HBAI20 vaccine seems safe, well-tolerated and may promote more rapid protection against hepatitis B infection.

IL-10-Modulated Human Dendritic Cells for Clinical Use: Identification of a Stable and Migratory Subset with Improved Tolerogenic Activity

Dendritic cells (DCs) are key regulators of protective immune responses and tolerance to (self-)Ags. Therefore, the scientific rationale for the use of tolerogenic DC therapy in the fields of allergies, autoimmunity, and transplantation medicine is strong. In this study, we analyzed the tolerogenic capacity of IL-10-modulated DC (IL-10DC) subpopulations to identify a DC subset that combines potent immunosuppressive activities with valuable immune properties for clinical implementation. IL-10DCs consist of two phenotypically distinct subpopulations: CD83highCCR7+ IL-10DCs and CD83lowCCR7- IL-10DCs. Suppressor assays with activated effector T cells revealed that CD4+ regulatory T cells generated by CD83high IL-10DCs (iTreg+) exhibited a significantly higher suppressive capacity compared with CD4+ regulatory T cells generated by CD83low IL-10DCs (iTreg-). In this context, iTreg+ displayed a more activated phenotype (proliferation, cytokine production) compared with iTreg- In contrast to CD83low IL-10DCs, CD83high IL-10DCs exerted a strong migratory capacity toward the secondary lymphoid organ chemokine CCL21 and retained a functionally stable phenotype under inflammatory conditions. In addition, CD83high IL-10DCs expressed significantly higher levels of surface and soluble CD25. Functional analysis demonstrated that IL-10DC-related soluble CD25 efficiently inhibited the proliferation of activated T cells and that blockade of CD25 function abolished the induction of regulatory T cells by IL-10DCs, indicating a critical role for IL-10DC-related CD25 in shifting the immune response toward an iTreg- controlled tolerance reaction. In conclusion, the selective use of the CD83high IL-10DC subset may result in a higher efficacy of tolerance induction in vivo and may support the development of novel DC vaccination strategies for transplantations, as well as for allergic and autoimmune diseases.

Unexpected impairment of TNF-α-induced maturation of human dendritic cells in vitro by IL-4

Background

An efficient strategy for programing dendritic cells (DCs) for cancer immunotherapy is the optimization of their maturation so that they can efficiently stimulate cancer-specific T cell responses. Interleukin (IL)-4 has appeared as an essential cytokine, widely used in vitro with granulocyte macrophage-colony stimulating factor (GM-CSF) to differentiate monocytes into immature DCs (iDC) and to prevent macrophage formation. Conflicting data have been published regarding the effect of IL-4 on functional DC maturation. To further understand IL-4’s effects on DC maturation and function in vitro, we choose the most commonly used maturation factor tumor necrosis factor (TNF)-α.

Methods

Human monocyte-derived iDC were treated for 48 h with GM-CSF and TNF-α in the presence (IL-4⁺-DC) or absence (IL-4⁻-DC) of IL-4 and functions of both DC populations were compared.

Results

On mixed lymphocyte reaction assay, IL-4⁺-DC were less potent than IL-4⁻-DC at inducing the proliferation of allogeneic CD4⁺ T cells and the proportion of activated T cells expressing CD69 and/or CD25 was smaller. Interleukin-4 reduced the cell-surface expression of TNF-α-induced DC maturation markers CD83, CD86, HLA-DR and CD25 and generated a heterogeneous population of DCs. IL-4⁺-DC secreted less IL-12 and more IL-10 than IL-4⁻-DC following activation by soluble CD40L, and IL-4⁺-DC-activated T cells secreted lesser amounts of T helper (Th) 1 cytokines (IL-2 and interferon-γ). Importantly, IL-4 impaired the in vitro migratory capacity of DCs in response to CCL21 and CCL19 chemokines. This effect was related to reduced expression of CCR7 at both mRNA and protein levels.

Conclusion

Interleukin-4 used with GM-CSF and TNF-α during the maturation of DCs in vitro impaired DC functions and disturbed the maturation effect of TNF-α. Finally, our study reinforces the view that the quality of the DC maturation stimulus, which regulates DC migration and cytokine production, may be a decisive feature of the immunogenicity of DCs.

CD83 is required for the induction of protective immunity by a DNA vaccine in a teleost model

In mammals, CD83 is a surface marker on mature dendritic cells and vital to lymphocyte activation. In teleost, studies on the function of CD83 are very limited. In this study, we examined the potential involvement of turbot (Scophthalmus maximus) CD83, SmCD83, in vaccine-induced immunity. For this purpose, turbot were immunized with pORF75, a DNA vaccine against megalocytivirus, in the presence or absence of pSmCD83, a plasmid that constitutively expresses SmCD83. Immune response and protection analysis showed that the presence of pSmCD83 significantly (i) enhanced the activation of head kidney macrophages (HKM) and immune gene expression, (ii) inhibited viral replication in fish tissues following megalocytivirus challenge and increased the survival of the vaccinated fish, and (iii) stimulated production of specific serum antibody and the cytotoxicity of peripheral blood leukocytes. To further examine the effect of SmCD83, pORF75 was administered into turbot in which SmCD83 was knocked down. Subsequent analysis showed that in fish with SmCD83 knockdown, vaccine-induced HKM activation and antibody production were severely reduced, and, consistently, the protectivity of pORF75 was drastically decreased. Taken together, these results indicate for the first time that teleost CD83 is required for the induction of protective immune response by DNA vaccine.

Triggering of NF-κB in cytokine-matured human DCs generates superior DCs for T-cell priming in cancer immunotherapy

Understanding the signaling that governs the immunogenicity of human dendritic cells (DCs) is a prerequisite for improving DC-based therapeutic vaccination strategies, in which the ability of DCs to induce robust and lasting Ag-specific CTL responses is of critical importance. Cytokine-matured DCs are regularly used, but to induce memory-type CTLs, they require additional activation stimuli, such as CD4+ T-cell help or TLR activation. One common denominator of these stimuli is the activation of NF-κB. Here, we show that human monocyte-derived, cytokine cocktail-matured DCs transfected with constitutively active mutants of IκB kinases (caIKKs) by mRNA electroporation, further upregulated maturation markers, and secreted enhanced amounts of cytokines, including IL-12p70, which was produced for more than 48 h after transfection. Most importantly, cytotoxic T cells induced by caIKK-transfected DCs combined high CD27 expression, indicating a more memory-like phenotype, and a markedly enhanced secondary expandability with a high lytic capacity. In contrast, CTLs primed and expanded with unmodified cytokine cocktail-matured DCs did not maintain their proliferative capacity upon repetitive stimulations. We hypothesize that "designer" DCs expressing constitutively active IκB kinases will prove highly immunogenic also in vivo and possibly emerge as a new strategy to improve the clinical efficacy of therapeutic vaccinations against cancer and other chronic diseases.

Two functionally distinct subsets of mast cells discriminated By IL-2-independent CD25 activities

We identified two mast cell subsets characterized by the differential expression of surface CD25 (IL-2Rα) and by different abilities to produce cytokines and to proliferate, both in vitro and in vivo. CD25 can be expressed on the surface of immune cells in the absence of the other chains of the IL-2R, which are indispensable for IL-2 signaling. We show that functional differences between the two mast cell populations were dependent on CD25 itself, which directly modulated proliferation and cytokine responses. These effects were completely independent from IL-2 or the expression of the other chains of the high-affinity IL-2R, indicating an autonomous and previously unappreciated role for CD25 in regulating cell functions. Cells genetically ablated for CD25 completely recapitulated the CD25-negative phenotype and never acquired the properties characteristic of CD25-positive mast cells. Finally, adoptive transfer experiments in the mouse demonstrated a different impact of these populations in models of anaphylaxis and contact sensitivity. Our findings indicate a general role for CD25 in contexts where IL-2 signaling is not involved, and may have important implications for all mast cell-related diseases, as well as in all cell types expressing CD25 independently of its IL-2-related functions.

IL-2 phosphorylates STAT5 to drive IFN-γ production and activation of human dendritic cells

Human dendritic cells (hDCs) produce IL-2 and express IL-2R α-chain (CD25), but the role of IL-2 in DC functions is not well defined. A recent study suggested that the main function of CD25 on hDCs was to transpresent IL-2 to activate T lymphocytes. Our results demonstrate the expression of the three chains of the IL-2R on hDCs and that IL-2 induces STAT5 phosphorylation. Interestingly, use of inhibitors of p-STAT5 revealed that IL-2 increases LPS-induced IFN-γ through STAT5 phosphorylation. Finally, we report that IL-2 increases the ability of hDCs to activate helpless CD8(+) T cells, most likely because of IL-2-triggered IFN-γ synthesis, as we previously described. For the first time, to our knowledge, we disclose that IL-2 induces monocyte-derived hDC's functional maturation and activation through IL-2R binding. Interestingly, our study suggests a direct effect of anti-CD25 mAbs on hDCs that may contribute to their clinical efficacy.

Norm- and hypo-fractionated radiotherapy is capable of activating human dendritic cells

Despite the transient immunosuppressive properties of local radiotherapy (RT), this classical treatment modality of solid tumors is capable of inducing immunostimulatory forms of tumor-cell death. The resulting 'immunotoxicity' in the tumor, but not in healthy tissues, may finally lead to immune-mediated destruction of the tumor. However, little is known about the best irradiation scheme in this setting. This study examines the immunological effects of differently irradiated human colorectal tumor cells on human monocyte-derived dendritic cells (DC). Human SW480 tumor cells were irradiated with a norm-fractionation scheme (5 × 2 Gy), a hypo-fractionated protocol (3 × 5 Gy), and with a high single irradiation dose (radiosurgery; 1 × 15 Gy). Subsequently, human immature DC (iDC) were co-incubated with supernatants (SN) of these differently treated tumor cells. Afterwards, DC were analyzed regarding the expression of maturation markers, the release of cytokines, and the potential to stimulate CD4(+) T-cells. The co-incubation of iDC with SN of tumor cells exposed to norm- or hypo-fractionated RT resulted in a significantly increased secretion of the immune activating cytokines IL-12p70, IL-8, IL-6, and TNFα, compared to iDC co-incubated with SN of tumor cells that received a high single irradiation dose or were not irradiated. In addition, DC-maturation markers CD80, CD83, and CD25 were also exclusively elevated after co-incubation with the SN of fractionated irradiated tumor cells. Furthermore, the SN of tumor cells that were irradiated with norm- or hypo-fractionated RT triggered iDC to stimulate CD4(+) T-cells not only in an allogenic, but also in an antigen-specific manner like mature DC. Collectively, these results demonstrate that norm- and hypo-fractionated RT induces a fast human colorectal tumor-cell death with immunogenic potential that can trigger DC maturation and activation in vitro. Such findings may contribute to the improvement of irradiation protocols for the most beneficial induction of anti-tumor immunity.

Priming of T follicular helper cells by dendritic cells

T follicular helper cells (Tfh) are required to generate long-lived antibody responses, which confer long-term protection to pathogens following vaccination or infection. Despite significant advances in the field, however, little is known about the early steps that drive Tfh cell differentiation. In this review, we will discuss the mechanisms by which dendritic cells promote the initial commitment of activated CD4(+) T cells to the Tfh cell differentiation pathway.

CpG methylation changes within the IL2RA promoter in type 1 diabetes of childhood onset

None of the polymorphic variants of the IL2RA gene found associated with Type 1 Diabetes (T1D) was shown to have a functional effect. To test if the epigenetic variation could play a role at this locus, we studied the methylation of 6 CpGs located within the proximal promoter of IL2RA gene in 252 T1D patients compared with 286 age-matched controls. We found that DNA methylation at CpGs -373 and -456 was slightly but significantly higher in patients than in controls (40.4 ± 4.6 vs 38.3 ± 5.4, p=1.4E4; 91.4 ± 2.8 vs 89.5 ± 5.3, p=1.8E-6), while other CpG showed a strictly comparable methylation. Among 106 single nucleotide polymorphisms (SNPs) located in the neighboring 180 kb region, we found that 28 SNPs were associated with DNA methylation at CpG -373. Sixteen of these SNPs were known to be associated with T1D. Our findings suggest that the effect of IL2RA risk alleles on T1D may be partially mediated through epigenetic changes.

Postthymic expansion in human CD4 naive T cells defined by expression of functional high-affinity IL-2 receptors

As the thymus involutes with age, the maintenance of peripheral naive T cells in humans becomes strongly dependent on peripheral cell division. However, mechanisms that orchestrate homeostatic division remain unclear. In this study we present evidence that the frequency of naive CD4 T cells that express CD25 (IL-2 receptor α-chain) increases with age on subsets of both CD31(+) and CD31(-) naive CD4 T cells. Analyses of TCR excision circles from sorted subsets indicate that CD25(+) naive CD4 T cells have undergone more rounds of homeostatic proliferation than their CD25(-) counterparts in both the CD31(+) and CD31(-) subsets, indicating that CD25 is a marker of naive CD4 T cells that have preferentially responded to survival signals from self-Ags or cytokines. CD25 expression on CD25(-) naive CD4 T cells can be induced by IL-7 in vitro in the absence of TCR activation. Although CD25(+) naive T cells respond to lower concentrations of IL-2 as compared with their CD25(-) counterparts, IL-2 responsiveness is further increased in CD31(-) naive T cells by their expression of the signaling IL-2 receptor β-chain CD122, forming with common γ-chain functional high-affinity IL-2 receptors. CD25 plays a role during activation: CD25(+) naive T cells stimulated in an APC-dependent manner were shown to produce increased levels of IL-2 as compared with their CD25(-) counterparts. This study establishes CD25(+) naive CD4 T cells, which are further delineated by CD31 expression, as a major functionally distinct immune cell subset in humans that warrants further characterization in health and disease.

CD25 Is Expressed by Canine Cutaneous Mast Cell Tumors but not by Cutaneous Connective Tissue Mast Cells

Canine cutaneous mast cell tumors (MCT) of different histological grades have distinct biological behaviors. However, little is known about underlying molecular mechanisms that lead to tumor development and increasing malignancy with higher tumor grade. Recent studies have identified the interleukin-2 receptor (IL-2R) subunits CD25 and CD2 as markers that distinguish nonneoplastic from neoplastic mast cells in human systemic mastocytosis. In this study, their potential as a marker for canine MCT and their possible impact on MCT carcinogenesis were evaluated. mRNA expression levels of both genes were compared between grade 1 ( n = 12) and grade 3 ( n = 8) MCT, and protein expression levels of CD25 were compared in 90 MCT of different tumor grades. mRNA expression levels of both CD25 and CD2 were upregulated in grade 3 MCT. In contrast, CD25 protein was expressed by fewer tumor cells and at decreased levels in grade 3 tumors, while most grade 1 MCT had strong CD25 protein expression. Moreover, CD25 was not expressed by nonneoplastic, resting cutaneous mast cells, while few presumably activated mast cells in tissue samples from dogs with allergic dermatitis had weak CD25 expression. Taken together, these findings suggest that CD25 may play a critical role in early MCT development and may be a stimulatory factor in grade 1 MCT, while grade 3 MCT seem to be less dependent on CD25. Because of the low number of CD25-positive tumor cells in high-grade tumors, the usefulness of CD25 as a tumor marker is, however, questionable.

The role of interleukin-2 during homeostasis and activation of the immune system

Interleukin-2 (IL-2) signals influence various lymphocyte subsets during differentiation, immune responses and homeostasis. As discussed in this Review, stimulation with IL-2 is crucial for the maintenance of regulatory T (T(Reg)) cells and for the differentiation of CD4(+) T cells into defined effector T cell subsets following antigen-mediated activation. For CD8(+) T cells, IL-2 signals optimize both effector T cell generation and differentiation into memory cells. IL-2 is presented in soluble form or bound to dendritic cells and the extracellular matrix. Use of IL-2 - either alone or in complex with particular neutralizing IL-2-specific antibodies - can amplify CD8(+) T cell responses or induce the expansion of the T(Reg) cell population, thus favouring either immune stimulation or suppression.

A role for interleukin-2 trans-presentation in dendritic cell-mediated T cell activation in humans, as revealed by daclizumab therapy

Although previous studies have described CD25 expression and production of interleukin-2 (IL-2) by mature dendritic cells (mDCs), it remains unclear how these molecules participate in the activation of T cells. In search of the mechanisms by which daclizumab, a humanized monoclonal antibody against CD25, inhibits brain inflammation in multiple sclerosis, we observed that although the drug has limited effects on polyclonal T cell activation, it potently inhibits activation of antigen-specific T cells by mDCs. We show that mDCs (and antigen-experienced T cells) secrete IL-2 toward the mDC-T cell interface in an antigen-specific manner, and mDCs 'lend' their CD25 to primed T cells in trans to facilitate early high-affinity IL-2 signaling, which is crucial for subsequent T cell expansion and development of antigen-specific effectors. Our data reveal a previously unknown mechanism for the IL-2 receptor system in DC-mediated activation of T cells.

IL-2 and its high-affinity receptor: genetic control of immunoregulation and autoimmunity

Type 1 diabetes (T1D) is an organ-specific autoimmune disease featured by destruction of the insulin producing beta-cells of the pancreas by autoreactive T-lymphocytes. Putative environmental triggers conspire with a constellation of genetic elements scattered throughout the genome to elicit a multifactorial autoimmune response involving virtually every cell type of the immune system against pancreatic beta-cells. Recent highly powered genome-wide association studies have confirmed and identified fifteen chromosomal regions harboring several candidate T1D-associated gene loci. Here, we summarize what we know about the genetics of T1D with an emphasis on the contributions of mouse Il2 and human IL2RA polymorphisms and the IL-2-IL-2R pathway to autoimmunity and, more specifically, Treg development and function.

In vitro differentiation of human monocytes into dendritic cells by peptic-tryptic digest of gliadin is independent of genetic predisposition and the presence of celiac disease

INTRODUCTION

This study was done to further reveal the role of the innate immune system in celiac disease.

METHODS

Dendritic cells were matured from venous blood of patients with active or treated celiac disease and DQ2-DQ8-positive or negative controls. Dendritic cells were treated with a peptic-tryptic digest of gliadin (500 microg/ml) and their activation was analyzed by fluorescent-activated cell sorting analysis, cytokine secretion, and their ability to elicit T cell proliferation.

RESULTS AND DISCUSSION

Gliadin upregulated interleukin (IL)-6, IL-8, and IL-12 (p40) secretion in dendritic cells and induced strong expression of the maturation markers human leukocyte antigen (HLA)-DR, CD25, CD83, and CD86 of all subjects irrespective of their genotype or the presence of disease, whereas the digest of bovine serum albumin showed no effect. However, gliadin-stimulated dendritic cells from active celiac showed enhanced stimulation of autologous T cells compared to the other groups.

CONCLUSION

Further research should be aimed at identifying the mechanisms that control inflammation in healthy individuals.

CD25 as an immune regulatory molecule expressed on myeloid dendritic cells

CD25 (alpha-chain of IL-2 receptor) on dendritic cells (DC) has been previously regarded as an activation marker. DC that concomitantly express surface CD25 and co-stimulatory molecules were considered to be fully mature. While both murine and human DC can express CD25, they do not express the beta-chain of the IL-2 receptor, which is indispensable for the execution of IL-2 signaling. The biological function of CD25 during the DC maturation therefore still remains undefined. In this review we focus on recent findings, describing CD25 expression and secretion by human myeloid regulatory DC. These DC co-express CD25 and the immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO) and inhibit T-cell function. CD25, expressed and secreted by such DC may capture IL-2 and thereby suppress T-cell proliferation, by this means providing an accessory mechanism of DC-mediated immune suppression. We also discuss the implication of DC-derived CD25 for human disease in both cancer and chronic infection.

The influence of CD4+ CD25+ Foxp3+ regulatory T cells on the immune response to rotavirus infection

Rotavirus (RV) infection of the intestine is the major cause of severe dehydrating diarrhea in infants around the world. Although protective immunity against RV, especially acquired B and T-cell responses, has been extensively studied, our understanding of RV immunity remains incomplete. In addition, the interaction between various protective immune mechanisms in the gut and specific enteric immune suppressor systems that normally exert a regulatory function on mucosal immunity has not been extensively investigated. Among the candidate suppressor systems, we hypothesized that CD4+ CD25+ Foxp3+ regulatory T (Treg) cells may play a role in modulating RV immunity since such cells are naturally present in large numbers in the intestine and function nonspecifically. Here we demonstrate that neonatal murine RV (EC) infection induces an expansion of the Treg cell population and the magnitude of the T cell mediated immune response is modulated by Treg cells. Accordingly, when natural Treg cells in neonatal mice were depleted before virus infection, both CD4+ and CD8+ T-cell responses to RV, such as proliferation and IFN-gamma secretion, were enhanced in mesenteric lymph nodes (MLNs) and the spleen. Interestingly, increased proliferation of CD19+ B cells from Treg cell depleted animals was also observed. Finally, we analyzed the in vivo effect of the Treg cell depletion on diarrheal disease, virus shedding and IgA RV-specific response. Treg cell depletion did not affect these functions. Our studies of immune modulatory Treg cells in the RV infection model may promote a better understanding of the basis for RV immunity as well as providing valuable clues for the development of more immunogenic RV vaccines.

Gene profiling analysis of ALVAC infected human monocyte derived dendritic cells

The recombinant canarypox virus ALVAC is being extensively studied as vaccine vector for the development of new vaccine strategies against chronic infectious diseases and cancer. However, the mechanisms by which ALVAC initiates the immune response have not been completely elucidated. In order to determine the type of innate immunity triggered by ALVAC, we characterized the gene expression profile of human monocyte derived dendritic cells (MDDCs) upon ALVAC infection. These cells are permissive to poxvirus infection and play a key role in the initiation of immune responses. The majority of the genes that were up-regulated by ALVAC belong to the type I interferon signaling pathway including IRF7, STAT1, RIG-1, and MDA-5. Genes involved in the NF-κB pathway were not up-regulated. The gene encoding for the chemokine CXCL10, a direct target of the transcription factor IRF3 was among those up-regulated and DC secretion of CXCL10 following exposure to ALVAC was confirmed by ELISA. Many downstream type I interferon activated genes with anti-viral activity (PKR, Mx, ISG15 and OAS among others) were also up-regulated in response to ALVAC. Among these, ISG15 expression in its unconjugated form by Western blot analysis was demonstrated. In view of these results we propose that ALVAC induces type I interferon anti-viral innate immunity via a cytosolic pattern-recognition-receptor (PRR) sensing double-stranded DNA, through activation of IRF3 and IRF7. These findings may aid in the design of more effective ALVAC-vectored vaccines.

Regulation of STAT pathways and IRF1 during human dendritic cell maturation by TNF-alpha and PGE2

Maturation of dendritic cells (DCs) by TLR ligands induces expression of IFN-beta and autocrine activation of IFN-inducible Stat1-dependent genes important for DC function. In this study, we analyzed the regulation of STAT signaling during maturation of human DCs by TNF-alpha and PGE2, which induced maturation of human DCs comparably with LPS but did not induce detectable IFN-beta production or Stat1 tyrosine phosphorylation. Consistent with these results, TNF-alpha and PGE2 did not induce Stat1 DNA binding to a standard Stat1-binding oligonucleotide. Instead, TNF-alpha and PGE2 increased Stat1 serine phosphorylation and Stat4 tyrosine phosphorylation and activated expression of the NF-kappaB and Stat1 target gene IFN regulatory factor 1 (IRF1), which contributes to IFN responses. TNF-alpha and PGE2 induced a complex that bound an oligonucleotide derived from the IRF1 promoter that contains a STAT-binding sequence embedded in a larger palindromic sequence, and this complex was recognized by Stat1 antibodies. These results suggest that TNF-alpha and PGE2 activate STAT-mediated components of human DC maturation by alternative pathways to the IFN-beta-mediated autocrine loop used by TLRs.

Comparison of alpha-Type-1 polarizing and standard dendritic cell cytokine cocktail for maturation of therapeutic monocyte-derived dendritic cell preparations from cancer patients

The current "gold standard" for generation of dendritic cell (DC) used in DC-based cancer vaccine studies is maturation of monocyte-derived DCs with tumor necrosis factor-alpha (TNF-alpha)/IL-1beta/IL-6 and prostaglandin E(2) (PGE(2)). Recently, a protocol for producing so-called alpha-Type-1 polarized dendritic cells (alphaDC1) in serum-free medium was published based on maturation of monocyte-derived DCs with TNF-alpha/IL-1-beta/polyinosinic:polycytidylic acid (poly-I:C)/interferon (IFN)-alpha and IFN-gamma. This DC maturation cocktail was described to fulfill the criteria for optimal DC generation and to be superior to the standard DC (sDC) cocktail as it induced fully mature DCs with potent IL-12p70 secretion together with CCR7 expression which is necessary for priming of a TH1 response and for migration to the draining lymph node, respectively. In this study, we tested the adaptation of alphaDC1 maturation cocktail to a protocol for clinical grade DC generation from cancer patients performed in X-VIVO 15 medium. We showed that alphaDC1 in this protocol induce lower up-regulation of CD83 and several other maturation markers, co-stimulatory molecules and CCR7 together with higher up-regulation of inhibitory molecules such as PD-L1, ILT2, ILT3 as compared to sDC. Although alphaDC1 matured DCs secreted more IL-12p70 and IL-23 these DCs had lower or similar stimulatory capacity compared to sDCs when used as stimulating cells in mixed lymphocyte reaction (MLR) or for induction of autologous influenza antigen specific T lymphocytes. Thus, our observations underline that alphaDC1 maturation cannot be directly adapted to alternative protocols for DC generation. Also, this study indicates the necessity for further investigation of correlation between in vitro DC parameters and their in vivo efficacy in clinical vaccination trials.

In-vitro activation of cytotoxic T lymphocytes by fusion of mouse hepatocellular carcinoma cells and lymphotactin gene-modified dendritic cells

AIM

To investigate the in-vitro activation of cytotoxic T lymphocytes (CTLs) by fusion of mouse hepatocellular carcinoma (HCC) cells and lymphotactin gene-modified dendritic cells (DCs).

METHODS

Lymphotactin gene modified DCs (DCLptn) were prepared by lymphotactin recombinant adenovirus transduction of mature DCs which differentiated from mouse bone marrow cells by stimulation with granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4) and tumor necrosis factor alpha (TNF-alpha). DCLptn and H22 fusion was prepared using 50% PEG. Lymphotactin gene and protein expression levels were measured by RT-PCR and ELISA, respectively. Lymphotactin chemotactic responses were examined by in-vitro chemotaxis assay. In-vitro activation of CTLs by DCLptn/H22 fusion was measured by detecting CD25 expression and cytokine production after autologous T cell stimulation. Cytotoxic function of activated T lymphocytes stimulated with DCLptn/H22 cells was determined by LDH cytotoxicity assay.

RESULTS

Lymphotactin gene could be efficiently transduced to DCs by adenovirus vector and showed an effective biological activity. After fusion, the hybrid DCLptn/H22 cells acquired the phenotypes of both DCLptn and H22 cells. In T cell proliferation assay, flow cytometry showed a very high CD25 expression, and cytokine release assay showed a significantly higher concentration of IFN-gamma and IL-2 in DCLptn/H22 group than in DCLptn, DCLptn+H22, DC/H22 or H22 groups. Cytotoxicity assay revealed that T cells derived from DCLptn/H22 group had much higher anti-tumor activity than those derived from DCLptn, H22, DCLptn+H22, DC/H22 groups.

CONCLUSION

Lymphotactin gene-modified dendritoma induces T-cell proliferation and strong CTL reaction against allogenic HCC cells. Immunization-engineered fusion hybrid vaccine is an attractive strategy in prevention and treatment of HCC metastases.