Sven Klaschik

CpG oligonucleotides as adjuvants for vaccines targeting infectious diseases

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs act as immune adjuvants, accelerating and boosting antigen-specific immune responses. CpG motifs promote the induction of Th1 and pro-inflammatory cytokines and support the maturation/activation of professional antigen presenting cells (particularly plasmacytoid dendritic cells). These effects are optimized by maintaining close physical contact between the CpG ODN and the immunogen. Co-administering CpG ODN with a variety of vaccines has improved the resultant humoral and/or cellular immune responses, culminating in enhanced protective immunity in rodent and primate challenge models. Ongoing clinical studies indicate that CpG ODN are safe and well-tolerated when administered as adjuvants to humans, and that they can support increased vaccine-specific immune responses.

Real-time PCR for detection and differentiation of gram-positive and gram-negative bacteria.

ABSTRACT We developed a consensus real-time PCR protocol that enables us to detect spiked bacterial 16S DNA from specimens such as water, urine, plasma, and sputum. The technique allows an exact Gram stain classification of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes. All tested bacteria were identified correctly, and none gave a false-positive signal with the opposite Gram probe.

Induction of Bim and Bid gene expression during accelerated apoptosis in severe sepsis

IntroductionIn transgenic animal models of sepsis, members of the Bcl-2 family of proteins regulate lymphocyte apoptosis and survival of sepsis. This study investigates the gene regulation of pro-apoptotic and anti-apoptotic members of the Bcl-2 family of proteins in patients with early stage severe sepsis.MethodsIn this prospective case-control study, patients were recruited from three intensive care units (ICUs) in a university hospital. Sixteen patients were enrolled when they fulfilled the criteria of severe sepsis. Ten critically ill but non-septic patients and 11 healthy volunteers served as controls. Blood samples were immediately obtained at inclusion. To confirm the presence of accelerated apoptosis in the patient groups, caspase-3 activation and phosphatidylserine externalisation in CD4+, CD8+ and CD19+ lymphocyte subsets were assessed using flow cytometry. Specific mRNAs of Bcl-2 family members were quantified from whole blood by real-time PCR. To test for statistical significance, Kruskal-Wallis testing with Dunns multiple comparison test for post hoc analysis was performed.ResultsIn all lymphocyte populations caspase-3 (p < 0.05) was activated, which was reflected in an increased phosphatidylserine externalisation (p < 0.05). Accordingly, lymphocyte counts were decreased in early severe sepsis. In CD4+ T-cells (p < 0.05) and B-cells (p < 0.001) the Bcl-2 protein was decreased in severe sepsis. Gene expression of the BH3-only Bim was massively upregulated as compared with critically ill patients (p < 0.001) and 51.6-fold as compared with healthy controls (p < 0.05). Bid was increased 12.9-fold compared with critically ill patients (p < 0.001). In the group of mitochondrial apoptosis inducers, Bak was upregulated 5.6-fold, while the expression of Bax showed no significant variations. By contrast, the pro-survival members Bcl-2 and Bcl-xl were both downregulated in severe sepsis (p < 0.001 and p < 0.05, respectively).ConclusionsIn early severe sepsis a gene expression pattern with induction of the pro-apoptotic Bcl-2 family members Bim, Bid and Bak and a downregulation of the anti-apoptotic Bcl-2 and Bcl-xl proteins was observed in peripheral blood. This constellation may affect cellular susceptibility to apoptosis and complex immune dysfunction in sepsis.

Synthetic oligonucleotides as modulators of inflammation

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs mimic the immunostimulatory activity of bacterial DNA. CpG ODN directly stimulate human B cells and plasmacytoid dendritic cells, promote the production of Th1 and proinflammatory cytokines, and trigger the maturation/activation of professional APC. CpG ODN are finding use in the treatment of cancer, allergy, and infection. In contrast, ODN containing multiple TTAGGG motifs mimic the immunosuppressive activity of self‐DNA, down‐regulating the production of proinflammatory and Th1 cytokines. Preclinical studies suggest that “suppressive” ODN may slow or prevent diseases characterized by pathologic immune stimulation, including autoimmunity and septic shock. Extensive studies in animal models suggest that the therapeutic value of CpG and TTAGGG ODN may be optimized by early administration.

Short- and long-term changes in gene expression mediated by the activation of TLR9.

CpG DNA binds to Toll-like receptor 9 to stimulate a strong innate immune response. The magnitude, duration and scope of CpG-induced changes in gene expression are incompletely understood despite extensive studies of TLR9 mediated signal transduction pathways. In particular, the prolonged effects of CpG DNA on gene activation have not been investigated despite evidence that a single dose of CpG DNA alters immune reactivity for several weeks. This study used gene expression analysis to monitor changes in mRNA levels for 14 days, and identified the genes, pathways and functional groups triggered in vivo following CpG DNA administration. Two discrete peaks of gene activation (at 3h and 5 days) were observed after CpG injection. Both the behavior and function of genes activated during the second peak differed from those triggered shortly after CpG administration. Initial gene up-regulation corresponded to a period when TLR9 ligation stimulated genes functionally associated with the generation of innate and adaptive immune responses (e.g. the NF-kappaB and B-cell receptor pathways). The second peak reflected processes associated with cell division (e.g. cell cycle and DNA replication and repair). The complex bimodal pattern of gene expression elicited by CpG DNA administration provides novel insights into the long-term effects of TLR9 engagement on genes associated with immunity and cell proliferation.

Detection and Differentiation of In Vitro-Spiked Bacteria by Real-Time PCR and Melting-Curve Analysis

ABSTRACT We introduce a consensus real-time PCR protocol for the detection of bacterial DNA from laboratory-prepared specimens such as water, urine, and plasma. This prototype detection system enables an exact Gram stain classification and, in particular, screening for specific species of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes and melting-curve analysis in a one-run experiment. One strain of every species was tested at a final density of 106 CFU/ml. All bacteria examined except Staphylococcus aureus and Staphylococcus epidermidis could be differentiated successfully; S. aureus and S. epidermidis could only be classified as “Staphylococcus species.” The hands-on time for preparation of the DNA, performance of the PCR, and evaluation of the PCR results was less than 4 h. Nevertheless, this prototype detection system requires more clinical validation.

Therapeutic Potential of Oligonucleotides Expressing Immunosuppressive TTAGGG Motifs

Synthetic oligodeoxynucleotides (ODNs) expressing immunosuppressive TTAGGG motifs downregulate the production of proinflammatory and Th1 cytokines. The ability of these “suppressive ODNs” to slow or prevent the development of diseases characterized by over‐exuberant immune stimulation was examined. Suppressive ODNs significantly reduced disease severity in murine models of arthritis, lupus, and LPS‐induced toxic shock. These beneficial effects were accompanied by a significant reduction in serum autoantibody and cytokine levels. Underlying these protective effects was the ability of suppressive ODNs to bind to and prevent the phosphorylation of STAT1 and STAT4, thereby blocking the signaling cascade central to the initiation and/or perpetuation of these disease states. These findings suggest that suppressive ODNs might find use in the treatment of acute and chronic diseases characterized by excessive immune stimulation.

Global changes in gene expression and synergistic interactions induced by TLR9 and TLR3

The innate immune system is triggered when pathogen-associated molecular patterns (PAMPs) expressed by infectious microorganisms interact with toll-like receptors (TLR) present on immune cells. Individual TLRs signal through distinct molecular pathways. For example, TLR9 interacts with unmethylated CpG motifs expressed by bacterial DNA and triggers via a MyD88 dependent pathway whereas TLR3 recognizes viral RNA through a MyD88-independent pathway. Bioinformatic analysis of microarray data was used to identify the regulatory patterns underlying changes in gene expression induced when RAW 264.7 macrophages were stimulated via TLR9 by CpG oligonucleotides (ODN) and/or via TLR3 by poly (I:C). While the genes activated by each ligand mediated similar functions, poly (I:C) elicited a larger and more diverse change in gene expression. Co-stimulation with both ligands accelerated gene expression and synergistically activated genes primarily associated with immune function. This is the first work to compare global changes in gene regulation triggered by distinct TLR pathways and clarify their impact on gene expression.

Therapeutic Applications and Mechanisms Underlying the Activity of Immunosuppressive Oligonucleotides

Synthetic oligodeoxynucleotides (ODN) capable of “neutralizing” or “inhibiting” immune responses have been described. This review will focus on the properties of phosphorothioate ODN that mimic the immunosuppressive activity of the repetitive TTAGGG motifs present in mammalian telomeres. These TTAGGG multimers block the production of pro‐inflammatory and T helper type 1 cytokines elicited when immune cells are activated by a wide variety of Toll‐like receptor ligands, polyclonal activators, and antigens. Several mechanisms contribute to the suppressive activity of such ODN. Ongoing microarray studies indicate that suppressive ODN interfere with the phosphorylation of signal transducer and activator of transcription 1 (STAT1) and STAT4, thereby blocking the inflammation mediated by STAT‐associated signaling cascades. In animal models, suppressive ODN can be used to prevent or treat diseases characterized by persistent immune activation, including collagen‐induced arthritis, inflammatory arthritis, systemic lupus erythematosus, silicosis, and toxic shock. These findings suggest that TTAGGG multimers may find broad use in the treatment of diseases characterized by over‐exuberant/persistent immune activation.

Real-time polymerase chain-reaction detection of pathogens is feasible to supplement the diagnostic sequence for urinary tract infections.

To evaluate, in a prospective pilot study, the feasibility of identifying pathogens in urine using real‐time polymerase chain reaction (PCR), and to compare the results with the conventional urine culture‐based procedures.