Petar Lenert

University of Iowa, Iowa City, IA, United States

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Publications (28)86.06 Total impact

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    ABSTRACT: Minocycline is a synthetic tetracycline-derived antibiotic with significant anti-inflammatory properties that may benefit patients with rheumatoid arthritis. Surprisingly, chronic exposure to minocycline can also cause a breach in immunologic tolerance resulting in a variety of autoimmune syndromes such as drug-induced lupus or autoimmune hepatitis. Vasculitis, most commonly resembling cutaneous polyarteritis nodosa, has also been seen in patients taking this drug. Herein, we present a case of biopsy-proven systemic vasculitis presenting as an ANA (+) ANCA (+) polyarteritis nodosa-like syndrome in a male patient who was taking minocycline for his acne for approximately 2 years. Patient initially presented with constitutional symptoms such as profound weight loss and fatigue, along with myalgias, oligoarticular arthritis, and livedo reticularis. About 2 months later, he developed a severe left testicular pain. Biopsy showed vasculitis complicated with the infarction of the left testis. Angiography revealed microaneurysms in the renal and splenic circulation. Stopping the offending drug, along with the short course of prednisone and hydroxychloroquine, resulted in prompt resolution of his symptoms. We additionally present a comprehensive review of biopsy-proven cases of vasculitis associated with chronic minocycline treatment focusing on its pathogenesis and clinical manifestations.
    Clinical Rheumatology 04/2013; · 2.04 Impact Factor
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    ABSTRACT: Type I allergic diseases, such as allergic rhinitis and asthma, depend on allergen-induced T-helper type 2 (Th2) cells and IgE-secreting plasma cells. Fortunately, this harmful immune response can be modified by engaging Toll-like receptor (TLR)7 and TLR9, offering hopes to allergy sufferers. While clinical trials employing synthetic ligands for TLR7 or TLR9 are under way, one can wonder whether TLR7 or TLR9 engagements may trigger inadvertent autoreactivity and/or Th1-/Th17-mediated tissue pathology. To neutralize such danger, we have pioneered the development of potent TLR9 pathway antagonists, inhibitory oligonucleotides (INH-ODNs), which work in a sequence-specific manner. Interestingly, INH-ODNs also have TLR7-inhibitory properties; however, these effects appear to be sequence independent and phosphorothioate backbone dependent. In B cells, co-engagement of the B-cell receptor for antigen and TLR7 or TLR9 may influence how INH-ODNs impose their regulatory effects. INH-ODNs block TLR9 activation by competitively antagonizing ligand binding to proteolytically cleaved C-terminal TLR9 fragment. One may envision future use of INH-ODNs in systemic autoimmune diseases, DNA-mediated sepsis, or other situations in which chronic inflammation results from abnormal TLR7- and/or TLR9-mediated immune activation.
    Current Allergy and Asthma Reports 11/2011; 12(1):8-17. · 2.75 Impact Factor
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    ABSTRACT: Nucleic acid sensors of the Toll-like receptor (TLR) family play a well-established role in the pathogenesis of lupus. This is particularly true for a single-stranded RNA-sensing TLR-7 receptor, as lupus mice lacking TLR-7 show ameliorated disease. Cytosine-guanosine dinucleotide (CpG)-DNA-sensing TLR-9, conversely, has a complex regulatory role in systemic lupus erythematosus (SLE). Much less is known about whether signals through the B cell receptor for antigen (BCR) may affect the ability of B cells to respond to suboptimal TLR-7 agonists and antagonists. We studied this question in prediseased BXSB male and female B cells. We found that male B cells responded more vigorously to numerous TLR-7 ligands and this responsiveness was enhanced further upon co-engagement of the BCR. This synergy was seen primarily with the interleukin (IL)-6 secretion. A number of 32-mer inhibitory oligonucleotides (INH-ODNs) with a nuclease-resistant phosphorothioate backbone were capable of blocking TLR-7, but not BCR-induced B cell activation, with an inhibitory concentration (IC)(50) of approximately 100 nm. Surprisingly, while the presence of a single TGC motif at the 5' end of an ODN did not increase its inhibitory capacity, INH-ODNs containing multiple TGC motifs had greater inhibitory potency. When BCR and TLR-7 were co-engaged, INH-ODNs showed a differential effect on B cell activation. Whereas apoptosis protection and G1-M entry completely escaped suppression, IL-6 secretion remained sensitive to inhibition, although with a 10-fold lower potency. Our results suggest that while TLR-7 antagonists may be considered as lupus therapeutics, simultaneous co-engagement of the TLR-7 and BCR might favour autoreactive B cell survival. This hypothesis needs further experimental validation.
    Clinical & Experimental Immunology 03/2011; 163(3):392-403. · 3.41 Impact Factor
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    ABSTRACT: Toll-like receptor (TLR)9 performs our innate response to bacterial DNA, warning us of the presence of infection. Inhibitory oligodeoxyribonucleotides (INH-ODN) have been developed that selectively block activation of mouse TLR9. Their inhibitory motif consisting of CCx(not-C)(not-C)xxGGG (x = any base) also reduces anti-DNA antibodies in lupus mice. The current study demonstrates that this motif also provides the sequences required to block TLR9 in human B cells and human embryonic kidney (HEK) cells transfected with human TLR9. However, extending the sequence by four to five bases at the 5' end enhanced activity and this enhancement was greater when a phosphorothioate (pS) backbone replaced the native phosphodiester (pO) backbone. A series of pO-backbone INH-ODN representing a 500-fold range of activity in biologic assays was shown to cover less than a 2.5-fold range of avidity for binding human TLR9-Ig fusion protein, eliminating TLR9 ectodomain binding as the explanation for sequence-specific differences in biologic activity. With few exceptions, the relative activity of INH-ODN in Namalwa cells and HEK/human TLR9 cells was similar to that seen in mouse B cells. INH-ODN activity in human peripheral blood B cells correlated significantly with the cell line data. These results favor the conclusion that although the backbone determines strength of TLR9 binding, critical recognition of the INH-ODN sequence necessary for biologic activity is performed by a molecule that is not TLR9. These studies also identify the strongest INH-ODN for human B cells, helping to guide the selection of INH-ODN sequences for therapeutics in any situation where inflammation is enhanced by TLR9.
    International Immunology 03/2011; 23(3):203-14. · 3.14 Impact Factor
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    Robert F Ashman, J Adam Goeken, Petar S Lenert
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    ABSTRACT: Toll-like receptor 9 (TLR9) is an endosomal DNA sensor that warns us of the presence of infectious danger and triggers a rapid pro-inflammatory response in dendritic cells, macrophages, and B cells. The consequences of uncontrolled TLR9 activation can be detrimental for the host, contributing to the pathogenesis of bacterial septic shock or autoimmune diseases, such as systemic lupus erythematosus. Therefore, we need to develop TLR9 antagonists. We and others have created inhibitory oligonucleotides (INH-ODN) that are capable of sequence-dependent inhibition of TLR9-induced activation in both human and mouse cells. However, it is not clear whether marked differences in INH-ODN activity related to base sequence derived from polymerization of INH-ODNs or their ability to complex with stimulatory CpG-oligonucleotides (ST-ODN). Furthermore, the 5' end of INH-ODNs may assume a particular loop configuration that may be needed for binding to a critical site on TLR9. Here, we show that 1) G-tetrads required for ODN stacking were compatible with INH-ODN activity but were not necessary; 2) there was no relationship between activity and self-association at endosomal pH; 3) there was no evidence for direct binding between ST-ODNs and INH-ODNs; 4) when a 3G sequence was disrupted, despite a preserved stem-loop formation, INH-ODN activity was abolished. These results support the conclusion that certain features of the primary linear sequence are critical for TLR9 inhibition, but changes in secondary structure or in ODN aggregation are irrelevant.
    International immunopharmacology 03/2011; 11(8):1032-7. · 2.21 Impact Factor
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    ABSTRACT: Crosslinking of Fc γ receptor II B (FcγRIIB) and the BCR by immune complexes (IC) can downregulate antigen-specific B-cell responses. Accordingly, FcγRIIB deficiencies have been associated with B-cell hyperactivity in patients with systemic lupus erythematosus and mouse models of lupus. However, we have previously shown that murine IgG2a-autoreactive AM14 B cells respond robustly to chromatin-associated IC through a mechanism dependent on both the BCR and the endosomal TLR9, despite FcγRIIB coexpression. To further evaluate the potential contribution of FcγRIIB to the regulation of autoreactive B cells, we have now compared the IC-triggered responses of FcγRIIB-deficient and FcγRIIB-sufficient AM14 B cells. We find that FcγRIIB-deficient cells respond significantly better than FcγRIIB-sufficient cells when stimulated with DNA IC that incorporate low-affinity TLR9 ligand (CG-poor dsDNA fragments). AM14 B cells also respond to RNA-associated IC through BCR/TLR7 coengagement, but such BCR/TLR7-dependent responses are normally highly dependent on IFN-α costimulation. However, we now show that AM14 FcγRIIB(-/-) B cells are very effectively activated by RNA IC without supplemental IFN-α priming. These results demonstrate that FcγRIIB can effectively modulate both BCR/TLR9 and BCR/TLR7 endosomal-dependent activation of autoreactive B cells.
    European Journal of Immunology 10/2010; 40(10):2692-8. · 4.97 Impact Factor
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    ABSTRACT: Murine dendritic cells (DC) and macrophages respond to bacterial CpG DNA through toll-like receptor 9 (TLR9). Although it is frequently assumed that bacterial DNA is a direct stimulus for B cells, published work does not reliably show responses of purified B cells. Here we show that purified splenic B cells did not respond to Escherichia coli DNA with induction of CD86, despite readily responding to single-stranded (ss) phosphodiester CpG oligodeoxynucleotides (ODN). This was due to a combination of weak responses to both long and double-stranded (ds) DNA. B-cell DNA uptake was greatly reduced with increasing DNA length. This contrasts with macrophages where DNA uptake and subsequent responses were enhanced with increasing DNA length. However, when DNA was physically linked to hen egg lysozyme (HEL), HEL-specific B cells showed efficient uptake of DNA, and limited proliferation in response to the HEL-DNA complex. We propose that, in the absence of other signals, B cells have poor uptake and responses to long dsDNA to prevent polyclonal activation. Conversely, when DNA is physically linked to a B-cell receptor (BCR) ligand, its uptake is increased, allowing TLR9-dependent B-cell activation in an antigen-specific manner. We could not generate fragments of E. coli DNA by limited DNaseI digestion that could mimic the stimulatory effect of ss CpG ODN on naïve B cells. We suggest that the frequently studied polyclonal B-cell responses to CpG ODN are relevant to therapeutic applications of phosphorothioate-modified CpG-containing ODN, but not to natural responses to foreign or host dsDNA.
    Immunology and Cell Biology 10/2010; 89(4):517-25. · 3.93 Impact Factor
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    ABSTRACT: The capacity to make secondary structures significantly affects the ability of Toll-like receptor 9 (TLR9) agonists and antagonists to either induce or block TLR9-dependent activation in B cells. However, it has a minor impact on TLR9-induced activation in interferon alpha (IFNα)-producing dendritic cells. Based on the ability of inhibitory oligodeoxynucleotides to form predictable secondary structures, we have classified TLR9-antagonists into Class R ('restricted', palindromic) and Class B ('broadly reactive', linear) oligodeoxynucleotides. In non-autoreactive B cells, Class R oligodeoxynucleotides are at least 10-fold less potent TLR9-inhibitors. We wanted to determine whether engagement of the B-cell receptor for antigen could overcome this restriction. Here we show that in non-autoreactive mouse B cells, B-cell receptor for antigen engagement increased the potency of Class R oligodeoxynucleotides for TLR9 activation at least 10-fold, making it equal in potency to linear oligodeoxynucleotides. However, this enhanced potency was selective for TLR9-induced B-cell cycling and apoptosis protection while TLR9-induced IL-6, an event that strongly depends on signaling via late endosomes, still required 10 times more Class R oligodeoxynucleotides. Thus, pathway-specific effects of Class R oligodeoxynucleotides for TLR9/B-cell receptor for antigen co-stimulated B cells may have therapeutic advantages over non-selective targeting of B cells, a strategy that may be seen as a potential therapy for human systemic lupus erythematosus.
    Lupus 10/2010; 19(11):1290-301. · 2.78 Impact Factor
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    P Lenert
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    ABSTRACT: Double-stranded (ds) DNA, DNA- or RNA-associated nucleoproteins are the primary autoimmune targets in SLE, yet their relative inability to trigger similar autoimmune responses in experimental animals has fascinated scientists for decades. While many cellular proteins bind non-specifically negatively charged nucleic acids, it was discovered only recently that several intracellular proteins are involved directly in innate recognition of exogenous DNA or RNA, or cytosol-residing DNA or RNA viruses. Thus, endosomal Toll-like receptors (TLR) mediate responses to double-stranded RNA (TLR-3), single-stranded RNA (TLR-7/8) or unmethylated bacterial cytosine (phosphodiester) guanine (CpG)-DNA (TLR-9), while DNA-dependent activator of IRFs/Z-DNA binding protein 1 (DAI/ZBP1), haematopoietic IFN-inducible nuclear protein-200 (p202), absent in melanoma 2 (AIM2), RNA polymerase III, retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) mediate responses to cytosolic dsDNA or dsRNA, respectively. TLR-induced responses are more robust than those induced by cytosolic DNA- or RNA- sensors, the later usually being limited to interferon regulatory factor 3 (IRF3)-dependent type I interferon (IFN) induction and nuclear factor (NF)-kappaB activation. Interestingly, AIM2 is not capable of inducing type I IFN, but rather plays a role in caspase I activation. DNA- or RNA-like synthetic inhibitory oligonucleotides (INH-ODN) have been developed that antagonize TLR-7- and/or TLR-9-induced activation in autoimmune B cells and in type I IFN-producing dendritic cells at low nanomolar concentrations. It is not known whether these INH-ODNs have any agonistic or antagonistic effects on cytosolic DNA or RNA sensors. While this remains to be determined in the future, in vivo studies have already shown their potential for preventing spontaneous lupus in various animal models of lupus. Several groups are exploring the possibility of translating these INH-ODNs into human therapeutics for treating SLE and bacterial DNA-induced sepsis.
    Clinical & Experimental Immunology 05/2010; 161(2):208-22. · 3.41 Impact Factor
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    Petar S Lenert
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    ABSTRACT: Our immune defense depends on two specialized armed forces. The innate force acts as an alarm mechanism that senses changes in the microenvironment through the recognition of common microbial patterns by Toll-like receptors (TLR) and NOD proteins. It rapidly generates an inflammatory response aimed at neutralizing the intruder at the mucosal checkpoint. The innate arm also communicates this message with more specialized adaptive forces represented by pathogen-specific B cells and T cells. Interestingly, B cells also express some innate sensors, like TLR7 and TLR9, and may respond to bacterial hypomethylated CpG motifs and single-stranded RNA viruses. Intracellular nucleic acid sensing TLRs play an important role in the pathogenesis of Systemic Lupus Erythematosus (SLE). In this review, we describe recent achievements in the development of oligonucleotide-(ODN)-based inhibitors of TLR9 and/or TLR7 signaling. We categorize these novel therapeutics into Classes G, R, and B based on their cellular and molecular targets. Several short ODNs have already shown promise as pathway-specific therapeutics for animal lupus. We envision their future use in human SLE, microbial DNA-dependent sepsis, and in other autoinflammatory diseases.
    Mediators of Inflammation 01/2010; 2010:986596. · 3.88 Impact Factor
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    ABSTRACT: INTRODUCTION: B cells have many different roles in systemic lupus erythematosus (SLE), ranging from autoantigen recognition and processing to effector functions (for example, autoantibody and cytokine secretion). Recent studies have shown that intracellular nucleic acid-sensing receptors, Toll-like receptor (TLR) 7 and TLR9, play an important role in the pathogenesis of SLE. Dual engagement of rheumatoid factor-specific AM14 B cells through the B-cell receptor (BCR) and TLR7/9 results in marked proliferation of autoimmune B cells. Thus, strategies to preferentially block innate activation through TLRs in autoimmune B cells may be preferred over non-selective B-cell depletion. METHODS: We have developed a new generation of DNA-like compounds named class R inhibitory oligonucleotides (INH-ODNs). We tested their effectiveness in autoimmune B cells and interferon-alpha-producing dendritic cells in vitro and in lupus-prone MRL-Faslpr/lpr mice in vivo. RESULTS: Class R INH-ODNs have 10- to 30-fold higher inhibitory potency when autoreactive B cells are synergistically activated through the BCR and associated TLR7 or 9 than when stimulation occurs via non-BCR-engaged TLR7/9. Inhibition of TLR9 requires the presence of both CCT and GGG triplets in an INH-ODN, whereas the inhibition of the TLR7 pathway appears to be sequence-independent but dependent on the phosphorothioate backbone. This difference was also observed in the MRL-Faslpr/lpr mice in vivo, where the prototypic class R INH-ODN was more effective in curtailing abnormal autoantibody secretion and prolonging survival. CONCLUSIONS: The increased potency of class R INH-ODNs for autoreactive B cells and dendritic cells may be beneficial for lupus patients by providing pathway-specific inhibition yet allowing them to generate protective immune response when needed.
    Arthritis research & therapy 01/2009; 11(3). · 4.27 Impact Factor
  • Robert Ashman, Adam Goeken, Petar Lenert
    Clinical Immunology - CLIN IMMUNOL. 01/2008; 127.
  • Robert F Ashman, Petar Lenert
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    ABSTRACT: Synthetic oligodeoxyribonucleotides (ODN) bearing certain sequence characteristics mimic bacterial DNA by activating B cells and dendritic cells through Toll-like receptor (TLR) 9, an event that potentiates both humoral and cell-mediated immunity. ODN sharing some of the sequence characteristics of strong stimulatory (ST-) ODN, but substituting GGG for CGTT, competitively inhibit ST-ODN-driven events. An ODN with the same length and base composition as a strong ST-ODN, but lacking both ST- and IN-sequence requirements, has neither ST- nor IN-activity. Whereas, certain sequence changes strongly influence ST-ODN activity in human cells relative to mouse cells and B cells relative to non B cells, the strongest IN-ODN appear to work well in both species and multiple cell types. Converting from the natural phosphodiester backbone to a nuclease-resistant phosphorothioate backbone increases the sensitivity to ST-ODN about 2 logs and to IN-ODN 3 logs, while increasing the impact of critical base changes in ST-ODN and diminishing it in IN-ODN. Examples where IN-ODN have been used in vivo to interrupt autoimmune and other TLR-9-induced inflammatory states are described.
    Immunologic Research 02/2007; 39(1-3):4-14. · 3.53 Impact Factor
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    ABSTRACT: Mouse follicular B cells express TLR9 and respond vigorously to stimulation with single-stranded CpG-oligodeoxynucleotides (ODN). Surprisingly, follicular B cells do not respond to direct stimulation with other TLR9 ligands, such as bacterial DNA or class A(D) CpG-ODN capable of forming higher-order structures, unless other cell types are present. Here, we show that priming with interferons or with B cell-activating factor, or simultaneous co-engagement of the B cell receptor for antigen (BCR), can overcome this unresponsiveness. The effect of interferons occurs at the transcriptional level and is mediated through an autocrine/paracrine loop, which is dependent on IRF-1, IL-6 and IL-12 p40. We hypothesize that the lack of bystander activation of follicular B cells with more complex CpG ligands may be an important safety mechanism for avoiding autoimmunity. This will prevent resting B cells from responding to foreign or self-derived hypomethylated double-stranded CpG ligands unless these ligands are either delivered through the B cell receptor or under conditions where B cells are simultaneously co-engaged by activated plasmacytoid dendritic cells or TH1 cells. A corollary is that the heightened responsiveness of lupus B cells to TLR9-induced stimulation cannot be ascribed to unprimed follicular B cells, but is rather mediated by hypersensitive marginal zone B cells.
    European Journal of Immunology 08/2006; 36(7):1951-62. · 4.97 Impact Factor
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    ABSTRACT: The intracellular Toll-like receptor 9 (TLR9) is unique in its ability to recognize single-stranded DNA unmethylated at CpG motifs. Work from this laboratory showed that plasmid DNA is spontaneously internalized in B lymphocytes. This event is followed by the upregulation of costimulatory molecules and the acquisition of antigen presenting function by these cells. However, it is not known whether this phenomenon depends on TLR9. Because of the relevant role played by DNA-based drugs in immunotherapy and vaccination, and the central role of TLR9 signaling by CpG motifs, we decided to investigate whether signaling through TLR9 is a prerequisite for spontaneous transgenesis of lymphocytes. Here we found that transgene expression and upregulation of CD40 and CD86 costimulatory molecules was not inhibited by chloroquine treatment. Spontaneous transgenesis also occurred in B lymphocytes from TLR9-/- mice, and the injection of TLR9-/- transgenic B lymphocytes in C57Bl/6 mice induced both CD4 and CD8 T cell responses comparable to those induced by wild-type B lymphocytes. Collectively, these results suggest that plasmid DNA activates mammalian B lymphocytes through a TLR9 independent pathway.
    DNA and Cell Biology 06/2006; 25(5):253-61. · 2.34 Impact Factor
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    ABSTRACT: Synthetic type B phosphorothioate oligodeoxyribonucleotides (ODN) activate mouse B cells via Toll-like receptor 9 (TLR9). Starting with closely related 15-mer prototype ODN, the sequence requirements for stimulatory (ST-) and inhibitory (IN-) activity were contrasted, by measuring apoptosis protection, G(1) entry and interleukin-6 secretion. ST-ODN and IN-ODN differ in that (1) ST-ODN require a 5' T, (2) the central CG is obligatory, (3) CG must be flanked 3' specifically by TT at the position where IN-ODN have GG, and (4) IN-ODN tolerate truncation of the 3' end better than ST-ODN. Features shared by ST-ODN and IN-ODN include (1) requiring CC adjacent to the 5' end, and (2) avoiding CC immediately 5' to the CG. This pattern is used to create a model of how ST-ODN binding might function to aggregate TLR9 so as to initiate the signal, and how the 5' ends of ST-ODN and IN-ODN compete for binding. Further justification for considering TLR9 to be the ODN receptor was provided by a demonstration that in HEK293 cells transfected with TLR9, the potency of a panel of ODN for activating NF-kappaB roughly parallels that seen in the biological assays in mouse B cells.
    Immunology 05/2006; 117(4):474-81. · 3.71 Impact Factor
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    Petar S Lenert
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    ABSTRACT: This review focuses on the role of Toll-like receptors (TLRs) in lupus and on possibilities to treat lupus using TLR modulating inhibitory oligodeoxynucleotides (INH-ODNs). TLRs bridge innate and adaptive immune responses and may play an important role in the pathogenesis of systemic lupus erythematosus. Of particular interest are TLR3, -7, -8, and -9, which are localized intracellularly. These TLRs recognize single-stranded or double-stranded RNA or hypomethylated CpG-DNA. Exposure to higher order CpG-DNA ligands or to immune complexed self-RNA triggers activation of autoreactive B cells and plasmacytoid dendritic cells. INH-ODNs were recently developed that block all downstream signaling events in TLR9-responsive cells. Some of these INH-ODNs can also target TLR7 signaling pathways. Based on their preferential cell reactivity, we classify INH-ODNs into class B and class R. Class B ('broadly reactive') INH-ODNs target a broad range of TLR-expressing cells. Class R ('restricted') INH-ODNs easily form DNA duplexes or higher order structures, and are preferentially recognized by autoreactive B cells and plasmacytoid dendritic cells, rather than by non-DNA specific follicular B cells. Both classes of INH-ODNs can block animal lupus. Hence, therapeutic application of these novel INH-ODNs in human lupus, particularly class R INH-ODNs, may result in more selective and disease-specific immunosuppression.
    Arthritis research & therapy 02/2006; 8(1):203. · 4.27 Impact Factor
  • Robert Ashman, Petar Lenert, Adam Goeken
    Clinical Immunology - CLIN IMMUNOL. 01/2006; 119.
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    ABSTRACT: Inhibitory oligonucleotides (IN-ODN) differing from stimulatory CpG ODN (ST-ODN) by as few as two bases can block ST-ODN-induced proliferation, apoptosis protection and IL-6 secretion in B lymphocytes and the production of IL-12p40 by non-B cells. The main objective of this study was to determine the ODN sequence requirements for inhibition in mice. Starting with a strongly inhibitory 15-mer prototype phosphorothioate sequence, we tested the 60 sequences that differed from the prototype by one base, revealing the three areas that are critical for activity. Between these areas were the spacer sequences where base composition mattered little, but the number of bases was important. Truncation of three bases at the 3' end of the 15-mer and one at the 5' end was tolerated with minimal loss of activity. This approach yielded an 'optimal' sequence of 5' CC x notC notC xxGGGx or CC x notC notC xGGGxx 3', where x is any base. The sequence requirements for optimal inhibition of B cell responses to Type B (K) ODN and mixed splenocyte IL-12p40 responses to Type A (D) ODN were strikingly similar. Inhibition of ST-ODN by IN-ODN was competitive. A hypothetical model of the ODN-binding site is proposed. Synthetic IN-ODN with the sequence characteristics defined here should provide antidotes for excessive innate reactions to DNA.
    International Immunology 05/2005; 17(4):411-20. · 3.14 Impact Factor
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    P Lenert
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    ABSTRACT: Recent studies have shed new light on a possible link between the innate activation of plasmocytoid dendritic cells and marginal zone B cells and the pathogenesis of systemic lupus erythematosus. Animal studies have identified that this response requires the Toll-like receptor 9 (TLR9). Engagement of the TLR9 by various ligands, including non-canonical CpG-motifs, can cause or aggravate pathogenic autoantibody production and cytokine secretion in lupus. Attempts to neutralize this activity either by blocking the acidification of the endosomal compartment with chloroquine and related compounds, or by preventing the interaction between the CpG-DNA sequences and TLR9 using inhibitory oligonucleotides could be a promising therapeutic option for lupus.
    Clinical & Experimental Immunology 05/2005; 140(1):1-10. · 3.41 Impact Factor