B-cell proliferation and differentiation in common variable immunodeficiency patients produced by an antisense oligomer to the rev gene of HIV-1

Immunoregulatory properties of cell-free DNA in plasma of celiac disease patients - A pilot study

The elevated plasma cell-free DNA (cfDNA) concentrations were repeatedly reported in association with the process of inflammation. The qualitative and quantitative characteristics of plasma cfDNA in active (newly diagnosed) celiac disease patients (CD) have not yet been studied despite the fact that cfDNA of healthy individuals is able to regulate immune response. We determined the total cfDNA concentration and relative content of telomeric sequences in plasma cfDNA in CD (n = 10) and healthy age- and sex-matched controls (HC, n = 10) by quantitative PCR. To obtain the evidence that the observed biological effects are caused solely by cfDNA molecules, we applied the treatment of paired plasma samples with DNase. Using paired samples of plasma (non-treated/native and treated by DNase), we analyzed the contribution of cfDNA to the activation of TLR9 and TNF-α mRNA expression in THP1 monocytic cell line. There were no significant differences in the quantities of plasma cfDNA and relative contents of telomeric sequences in their pools. When we compared the levels of TNF-α mRNA expression in THP1 cells achieved after stimulation with native CD and HC plasma samples, we found significantly (p = .031) higher expression after stimulation with CD samples. We documented also the ability of cfDNA contained in CD plasma samples to stimulate the production of TLR9 mRNA. The TLR9 mRNA expression levels were significantly (p = .014) lowered after cfDNA removal from CD plasma samples. The design of our experiments allowed us to study the effects of cfDNA without its isolation from plasma. cfDNA contained in CD plasma samples differs significantly in its immunoregulatory capacity from cfDNA in HC plasma. The differences are caused neither by different concentrations of cfDNA in plasma samples nor by different relative abundance of telomeric sequences. Further studies are needed to elucidate the role of plasma cfDNA in celiac disease pathogenesis.

DSP30 enhances the immunosuppressive properties of mesenchymal stromal cells and protects their suppressive potential from lipopolysaccharide effects: A potential role of adenosine

Multipotent mesenchymal stromal cells (MSC) are imbued with an immunosuppressive phenotype that extends to several immune system cells. In this study, we evaluated how distinct Toll-like receptor (TLR) agonists impact immunosuppressive properties of bone marrow (BM)-MSC and explored the potential mechanisms involved. We show that TLR4 stimulation by lipopolysaccharide (LPS) restricted the ability of MSC to suppress the proliferation of T lymphocytes, increasing the gene expression of interleukin (IL)-1β and IL-6. In contrast, stimulation of TLR9 by DSP30 induced proliferation and the suppressive potential of BM-MSC, coinciding with reducing tumor necrosis factor (TNF)-α expression, increased expression of transforming growth factor (TGF)-β1, increased percentages of BM-MSC double positive for the ectonucleotidases CD39+CD73+ and adenosine levels. Importantly, following simultaneous stimulation with LPS and DSP30, BM-MSC's ability to suppress T lymphocyte proliferation was comparable with that of non-stimulated BM-MSC levels. Moreover, stimulation of BM-MSC with LPS reduced significantly the gene expression levels, on co-cultured T lymphocyte, of IL-10 and interferon (IFN)γ, a cytokine with potential to enhance the immunosuppression mediated by MSC and ameliorate the clinical outcome of patients with graft-versus-host disease (GVHD). Altogether, our findings reiterate the harmful effects of LPS on MSC immunosuppression, besides indicating that DSP30 could provide a protective effect against LPS circulating in the blood of GVHD patients who receive BM-MSC infusions, ensuring a more predictable immunosuppressive effect. The novel effects and potential mechanisms following the stimulation of BM-MSC by DSP30 might impact their clinical use, by allowing the derivation of optimal "licensing" protocols for obtaining therapeutically efficient MSC.

The role of toll-like receptors in B-cell development and immunopathogenesis of common variable immunodeficiency

Common variable immunodeficiency (CVID) is the most frequent symptomatic primary immune deficiency and is characterized by hypogammaglobulinemia, defect in specific antibody response and increased susceptibility to recurrent infections, malignancy and autoimmunity. Patients with CVID often have defects in post-antigenic B-cell differentiation, with fewer memory B cells and impaired isotype switching. Toll-like receptors (TLRs) are expressed on various immune cells as key elements of innate and adaptive immunity. TLR signaling in B cells plays multiple roles in cell differentiation and activation, class-switch recombination and cytokine and antibody production. Moreover, recent studies have shown functional alteration of TLRs responses in CVID patients including poor cell proliferation, impaired upregulation of co-stimulatory molecules and failure in cytokine and immunoglobulin production. The purpose of the present review is to discuss the role of TLRs in B-cell development and function as well as their role in the immunopathogenesis of CVID.

Toll-like receptor signaling in primary immune deficiencies

Toll-like receptors (TLRs) recognize common microbial or host-derived macromolecules and have important roles in early activation of the immune system. Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins to the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are specific for susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Dampening of TLR responses is seen for TLRs 2 and 4 in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome, and for most TLRs in adenosine deaminase deficiency.

Toll-like receptor function in primary B cell defects

Primary immunodeficiency diseases include more than 150 different genetic defects, classified on the basis of the mutations or physiological defects involved. The first immune defects to be well recognized were those of adaptive immunity affecting B cell function and resulting in hypogammaglobulinemia and defects of specific antibody production; more recently, novel defects of innate immunity have been described, some involving Toll-like receptors (TLRs) and their signaling pathways. Furthermore, it is increasingly evident that the innate and adaptive pathways intersect and reinforce each other. B cells express a number of TLRs, which when activated lead to cell activation, up-regulation of co-stimulatory molecules, secretion of cytokines, up-regulation of recombination enzymes, isotype switch and immune globulin production. TLR activation of antigen presenting cells leads to heightened cytokine production, providing additional stimuli for B cell development and maturation. Recent studies have demonstrated that patients with common variable immunodeficiency (CVID) and X-linked agammaglobulinemia (XLA) have altered TLR responsiveness. We review TLR defects in these disorders of B cell development, and discuss how B cell gene defects may modulate TLR signaling.

Role of B cells in common variable immune deficiency

Common variable immune deficiency is a heterogeneous immune deficiency characterized by reduced serum immunoglobulins and a lack of antibodies. As the name implies, B-cell defects are variably defective. In particular, peripheral blood isotype-switched CD27(+) memory B cells are reduced in number and have been the basis of several classification schemes. A lack of these B cells has been associated with selected clinical conditions, including immune cytopenias, splenomegaly, granulomatous disease and lymphadenopathy. Genetic defects in ICOS, CD19 and TACI have been described. In addition to defects in the production or survival of memory B cells, in most subjects, B cells have defects in Toll-like receptor signaling.

Update in understanding common variable immunodeficiency disorders (CVIDs) and the management of patients with these conditions

The common variable immunodeficiency disorders are a mixed group of heterogeneous conditions linked by lack of immunoglobulin production and primary antibody failure. This variability results in difficulty in making coherent sense of either immunopathogenesis or the role of various genetic abnormalities reported in the literature. The recent attempt to collate the varied complications in these conditions and to define particular clinical phenotypes has improved our understanding of these diseases. Once refined and confirmed by other studies, these definitions will facilitate improved accuracy of prognosis and better management of clinical complication. They may also provide a method of analysing outcomes as related to new immunopathological and genetic findings.

Common variable immune deficiency: reviews, continued puzzles, and a new registry

BACKGROUND

Common variable immune deficiency (CVID) is a clinically and immunologically heterogenous primary immune deficiency first described more than 50 years ago. The main features are hypogammaglobulinemia, recurrent infections, and other complications. While CVID is considered as a genetic immune defect, and several genes have been reported as leading to the CVID phenotype, one of the most puzzling features of CVID is the sporadic inheritance pattern and the relatively late onset. In most cases, no other family members have any immune defect. The mean age at diagnosis is between 25 and 45 years of age. These features suggest the interplay between either several or numerous genes with or without potential environmental factors.

Blood serum DNA in patients with rheumatoid arthritis is considerably enriched with fragments of ribosomal repeats containing immunostimulatory CpG-motifs

We previously hypothesized that the sequence of transcribed region of human ribosomal repeats is selectively accumulated in circulating extracellular DNA due to its increased resistance to double-strand breaks caused by accumulation of single-chain breaks produced by nucleases. The contents of rDNA in blood serum DNA and in DNA from leukocytic nuclei both in healthy donors and in patients with rheumatoid arthritis were compared using dot hybridization method. By the content of non-methylated CpG-repeats, transcribed region of rDNA is identical to bacterial DNA, which is characterized by potent immunostimulatory effect. The transcribed region of rDNA (13.3 kb) contains more than 200 CpG-motifs capable of interacting with TLR9 receptors, which are the mediators of the cell immune response to the action of CpG-rich DNA fragments. The data suggest that DNA from dead cells circulating in the peripheral blood is enriched with sequences possessing potent immunostimulatory properties.

TLR9 activation is defective in common variable immune deficiency

Common variable immune deficiency (CVID) is a primary immune deficiency characterized by low levels of serum immune globulins, lack of Ab, and reduced numbers of CD27+ memory B cells. Although T, B, and dendritic cell defects have been described, for the great majority, genetic causes have not been identified. In these experiments, we investigated B cell and plasmacytoid dendritic cell activation induced via TLR9, an intracellular recognition receptor that detects DNA-containing CpG motifs from viruses and bacteria. CpG-DNA activates normal B cells by the constitutively expressed TLR9, resulting in cytokine secretion, IgG class switch, immune globulin production, and potentially, the preservation of long-lived memory B cells. We found that CpG-DNA did not up-regulate expression of CD86 on CVID B cells, even when costimulated by the BCR, or induce production of IL-6 or IL-10 as it does for normal B cells. TLR9, found intracytoplasmically and on the surface of oligodeoxynucleotide-activated normal B cells, was deficient in CVID B cells, as was TLR9 mRNA. TLR9 B cell defects were not related to proportions of CD27+ memory B cells. CpG-activated CVID plasmacytoid dendritic cells did not produce IFN-alpha in normal amounts, even though these cells contained abundant intracytoplasmic TLR9. No mutations or polymorphisms of TLR9 were found. These data show that there are broad TLR9 activation defects in CVID which would prevent CpG-DNA-initiated innate immune responses; these defects may lead to impaired responses of plasmacytoid dendritic cells and loss of B cell function.

Deficient IL-12 and dendritic cell function in common variable immune deficiency

Patients with common variable immune deficiency have reduced serum IgG, IgA, and/or IgM, defective antibody production, and many have cellular abnormalities, including proliferative defects, accelerated T cell apoptosis, and insufficient production of IL-2 and IL-10. Excess monocyte intracellular IL-12 leading to a polarized Th-1-type response which could prevent antibody production has been suggested. Here we found that dendritic cells (DCs) of CVID subjects have a significantly reduced capacity to secrete IL-12, as compared to DCs of normal subjects when cultured with physiologic simulators: LPS (P = 0.0005), TNF-alpha (P = 0.006), or CD40-L fusion protein (P = 0.0004). CVID TNF-alpha or CD40-Ligand matured DCs were also significantly impaired in antigen presentation in mixed lymphocyte culture. Deficient IL-12 production was closely correlated to lymphocyte functions in vitro and to the absolute numbers of CD4 T cells in peripheral blood. While CVID DCs appear morphologically similar to DCs of normal subjects, the lack of IL-12 production and defective antigen presentation demonstrate functional defects. Deficient DC function could lead to attenuated T cell activation and defective immunization, features characteristic of CVID.

Stimulation of peripheral blood and intestinal mucosa cells by synthetic CpG oligodeoxynucleotides

The breakdown of tolerance to autologous bacterial flora has been implicated as a major factor contributing to the initiation and perpetuation of chronic inflammation in inflammatory bowel diseases (IBD). To test whether bacterial DNA is at the origin of inflammation in IBD, we have examined the response of lamina propria (LPMC) or peripheral mononuclear cells (PBMC) and purified T cells from IBD patients and control patients to stimulations with a set of oligodeoxynucleotides (ODNs) characterized by the presence or absence of cytosine-guanosine dinucleotides (CpG) and/or 3' poly-guanosine (poly-G) extension. Furthermore we have evaluated the costimulatory activities of these ODNs on T cells activated via CD2 or CD3 pathway. We demonstrated that CpG ODNs induce higher proliferation of LPMC from inflammatory intestinal mucosa compared to healthy mucosa. We confirmed that CpG ODNs do not directly costimulate peripheral blood T cells activated by CD3 pathway. Finally, we revealed that CpG or non-CpG ODNs with 3' poly-G extension inhibit completely CD2 activation of purified PB or LP T-cells whereas only CpG ODNs without poly-G extension enhance proliferation and IFN-gamma production of PB T cells stimulated by CD2 pathway only in presence of NK and NK T cells. Our data suggest that NK T cells may be the primary target of ODNs and play a crucial role in indirect T-cell activation by ODN.

Therapeutic strategies in common variable immunodeficiency

The treatment of common variable immunodeficiency (CVID) is currently based on the early recognition of the condition and replacement immunoglobulin combined with prompt treatment of infections and complications. The route of administration, dose and frequency of administration of immunoglobulin still vary between centres and countries. Other interventions aimed at overcoming the immunological defects in CVID such as interleukin-2 therapy are being studied but there is as yet insufficient evidence to support their routine use. The treatment of complications such as suppurative lung disease uses principles broadly similar to those used for cystic fibrosis, whereas the granulomatous complications involving the lungs and other organ systems are in need of much more research to define optimum therapies.

Responses of human B cells to DNA and phosphorothioate oligodeoxynucleotides

Emerging information has documented that certain DNA and sODNs can be both immunogenic and immunostimulatory. sODNs, but not DNA, induce T-cell-independent polyclonal activation of human B cells by engaging cell-surface receptors. Manifestations of sODN-induced human B-cell activation include expression of activation markers, proliferation, Ig production and anti-DNA antibody production. IL-2 and intact T cells enhanced B-cell responses to sODNs but were not required. Monocytes also provided a modest enhancement of human B-cell responses induced by sODNs. The chemical nature of sODNs capable of stimulating human B cells and the specific cell-surface receptors involved have not been completely delineated. Further studies will be necessary to elucidate the potential role of stimulatory sODNs in disease pathogenesis and to develop a means to employ ODNs as therapeutic agents in humans.

Delineation of a CpG phosphorothioate oligodeoxynucleotide for activating primate immune responses in vitro and in vivo

Oligodeoxynucleotides (ODN) containing unmethylated CpG dinucleotides within specific sequence contexts (CpG motifs) are detected, like bacterial or viral DNA, as a danger signal by the vertebrate immune system. CpG ODN synthesized with a nuclease-resistant phosphorothioate backbone have been shown to be potent Th1-directed adjuvants in mice, but these motifs have been relatively inactive on primate leukocytes in vitro. Moreover, in vitro assays that predict in vivo adjuvant activity for primates have not been reported. In the present study we tested a panel of CpG ODN for their in vitro and in vivo immune effects in mice and identified in vitro activation of B and NK cells as excellent predictors of in vivo adjuvant activity. Therefore, we tested >250 phosphorothioate ODN for their capacity to stimulate proliferation and CD86 expression of human B cells and to induce lytic activity and CD69 expression of human NK cells. These studies revealed that the sequence, number, and spacing of individual CpG motifs contribute to the immunostimulatory activity of a CpG phosphorothioate ODN. An ODN with a TpC dinucleotide at the 5' end followed by three 6 mer CpG motifs (5'-GTCGTT-3') separated by TpT dinucleotides consistently showed the highest activity for human, chimpanzee, and rhesus monkey leukocytes. Chimpanzees or monkeys vaccinated once against hepatitis B with this CpG ODN adjuvant developed 15 times higher anti-hepatitis B Ab titers than those receiving vaccine alone. In conclusion, we report an optimal human CpG motif for phosphorothioate ODN that is a candidate human vaccine adjuvant.

Mechanism and function of a newly identified CpG DNA motif in human primary B cells

The vertebrate immune system recognizes bacterial DNA based on the presence of unmethylated CpG-dinucleotides in particular base contexts ("CpG motifs"). In contrast to mice, knowledge about CpG-mediated effects on human B cells is poor. In the present study we identify and determine an optimal human CpG motif. A phosphodiester oligonucleotide containing this motif strongly stimulated CD86, CD40, CD54, and MHC class II expression, IL-6 synthesis, and proliferation of primary human B cells. These effects required internalization of the oligonucleotide and endosomal maturation. The molecular mechanism of action of this CpG motif was associated with the sustained induction of the NF-kappaB p50/p65 heterodimer and of the transcription-factor complex AP-1. Transcription-factor activation by CpG DNA was preceded by increased phosphorylation of the stress kinases c-Jun N-terminal kinase and p38, and of activating transcription factor-2. In contrast to CpG, signaling through the B cell receptor led to activation of extracellular receptor kinase and to phosphorylation of a different isoform of c-Jun N-terminal kinase. These studies define the structure of a highly active human CpG motif and characterize its molecular mechanism of action in primary human B cells.

DNA activates human immune cells through a CpG sequence-dependent manner

While bacterial DNA and cytosine-guanosine-dinucleotide-containing oligonucleotides (CpG ODN) are well described activators of murine immune cells, their effect on human cells is inconclusive. We investigated their properties on human peripheral blood mononuclear cells (PBMC) and subsets thereof, such as purified monocytes, T and B cells. Here we demonstrate that bacterial DNA and CpG ODN induce proliferation of B cells, while other subpopulations, such as monocytes and T cells, did not proliferate. PBMC mixed cell cultures, as well as purified monocytes, produced interleukin-6 (IL-6), IL-12 and tumour necrosis factor-alpha upon stimulation with bacterial DNA; however, only IL-6 and IL-12 secretion became induced upon CpG ODN stimulation. We conclude that monocytes, but not B or T cells, represent the prime source of cytokines. Monocytes up-regulated expression of antigen-presenting, major histocompatibility complex class I and class II molecules in response to CpG DNA. In addition, both monocytes and B cells up-regulate costimulatory CD86 and CD40 molecules. The activation by CpG ODN depended on sequence motifs containing the core dinucleotide CG since destruction of the motif strongly reduced immunostimulatory potential.

CpG DNA and LPS induce distinct patterns of activation in human monocytes

A specific set of immune functions is switched on in response to DNA containing unmethylated CpG dinucleotides in particular base contexts ('CpG motifs'). Plasmids, viral vectors and antisense oligodeoxynucleotides used for DNA vaccination, gene replacement or gene blockade contain immunostimulatory CpG motifs which may have independent biological activity. Although the immune stimulatory effects of CpG motifs on murine cells are well established, the evaluation of their possible effects on human cells is complicated by the higher LPS sensitivity of human leukocytes compared with those in mice. To address this issue, we analyzed CpG- and LPS-mediated immune activation of human PBMC. The biologic activity of LPS could be detected within 4 h using intracellular TNF staining of monocytes with flow cytometry at concentrations just one-twentieth (0.0014 Eu/ml) of the lower detection limit for the routinely used LAL assay (0.03 EU/ml). In contrast to the rapid LPS response, CpG DNA-stimulated TNF and IL-6 synthesis in human monocytes was not detectable until 18 h. E. coli DNA induced IL-6 synthesis in a concentration-dependent manner (30 micrograms/ml E. coli DNA; 409 pg/ml +/- 75 pg/ml, n = 7, IL-6 ELISA), but calf thymus DNA did not (< 10 pg/ml). Likewise, the CpG oligodeoxynucleotides 1760 (phosphorothioate) and 2059 (unmodified) induced IL-6 synthesis, but the corresponding control oligonucleotides 1908 and 2077 did not CpG DNA and LPS enhanced IL-6 synthesis synergistically. ICAM-1-expression of monocytes was increased 4.6-fold by E. coli DNA, 3.5-fold by 1760 and three-fold by 2059, compared with 3.6-fold by a maximal LPS stimulus and no change with non-CpG DNA. In conclusion, CpG-motifs induce TNF, IL-6 and ICAM-1 expression in human monocytes, but the kinetics of this differ from that induced by LPS, which makes it possible to distinguish immune activation by these agents. These results have important implications for the clinical development of therapeutic DNA in humans.

Amplification of antibody production by phosphorothioate oligodeoxynucleotides

A phosphorothioate oligodeoxynucleotide that is complementary (antisense) to the initiation region of the rev gene of HIV-1 causes hypergammaglobulinemia and splenomegaly in mice, and it induces B cell proliferation and differentiation in mouse spleen mononuclear cells (SMNCs) and human peripheral blood mononuclear cells in vitro. The current studies were performed to investigate the specificity of these immunomodulatory effects. Both the sense and antisense rev oligomers stimulated tritiated thymidine incorporation and secretion of immunoglobulin M (IgM) and immunoglobulin G (IgG) by mouse SMNCs in a concentration-dependent fashion, but the antisense oligomer produced greater immune effects. Studies comparing phosphorothioate oligomers (anti-rev, c-myc, and c-myb) either methylated or unmethylated at CpG dinucleotides showed that methylation effectively abrogated the proliferative effect and tended to reduce the immunoglobulin secretory activity, but the latter was not statistically significant except in the case of IgG in anti-rev oligomer-treated cultures. Mice were injected with the sense or antisense rev oligomers singly or in combination. The animals then were immunized with tetanus toxoid and received a booster 21 days later. Oligodeoxynucleotide-treated mice had significantly higher levels of IgM antibodies on days 28 and 35 and of IgG antibodies on days 14 and 35 as compared with mice that were immunized but received vehicle alone. There was no evidence for additive, synergistic, or antagonistic interactions of the sense and antisense rev oligomers. These results indicate that the unmethylated anti-rev oligomer is the most potent of the phosphorothioate oligomers tested at activating lymphocyte proliferation and differentiation and that a single intravenous injection of this oligodeoxynucleotide augments antibody production to a specific antigen as long as 35 days later.