CpG motifs in bacterial DNA and their immune effects

A candidate DNA vaccine elicits HCV specific humoral and cellular immune responses

AIM: To investigate the immunogenicity of candidate DNA vaccine against hepatitis C virus (HCV) delivered by two plasmids expressing HCV envelope protein 1 (E1) and envelope protein 2 (E2) antigens respectively and to study the effect of CpG adjuvant on this candidate vaccine.

METHODS: Recombinant plasmids expressing HCV E1 and E2 antigens respectively were used to simultaneously inoculate mice with or without CpG adjuvant. Antisera were then collected and titers of anti-HCV antibodies were analyzed by ELISA. One month after the last injection, animals were sacrificed to prepare single-cell suspension of splenocytes. These cells were subjected to HCV antigen specific proliferation assays and cytokine secretion assays to evaluate the cellular immune responses of the vaccinated animals.

RESULTS: Antibody responses to HCV E1 and E2 antigens were detected in vaccinated animals. Animals receiving CpG adjuvant had slightly lower titers of anti-HCV antibodies in the sera, while the splenocytes from these animals showed higher HCV-antigen specific proliferation. Analysis of cytokine secretion from the splenocytes was consistent with the above results. While no antigen-specific IL-4 secretion was detected for all vaccinated animals, HCV antigen-specific INF-γ secretion was detected for the splenocytes of vaccinated animals. CpG adjuvant enhanced the secretion of INF-γ but did not change the profile of IL-4 secretion.

CONCLUSION: Vaccination of mice with plasmids encoding HCV E1 and E2 antigens induces humoral and cellular immune responses. CpG adjuvant significantly enhances the cellular immune response.

Aluminium adjuvants—in retrospect and prospect

Aluminium compounds have been used as adjuvants in practical vaccination for more than 60 years to induce an early, an efficient and a long lasting protective immunity and are at present the most widely used adjuvants in both veterinary and human vaccines. Although the last two decades of systematic research into the nature of these adjuvants has contributed significantly to understanding their nature and their limitations as Th2 stimulators the more detailed mode of action of these adjuvants is still not completely understood. We have a comprehensive record of their behaviour and performance in practical vaccination, but an empirical approach to optimising their use in new vaccine formulations is still to some extent a necessity. The aim of the present review is to put the recent findings into a broader perspective to facilitate the application of these adjuvants in general and experimental vaccinology.

Human B cells express functional TRAIL/Apo-2 ligand after CpG-containing oligodeoxynucleotide stimulation

CpG-containing oligodeoxynucleotides (CpG ODN) have broad-ranging immunostimulatory effects, including the generation of antitumor immune responses. Analysis of different CpG ODN have identified two classes: CpG-A ODN, which stimulate high levels of IFN-alpha production from plasmacytoid dendritic cells and weakly activate B cells, and CpG-B ODN, which strongly activate B cells but stimulate low production of IFN-alpha from plasmacytoid dendritic cells. Previously, we observed that CpG-B ODN (2006) induces TRAIL/Apo-2 ligand (Apo-2L)-mediated killing of tumor cells by CD14(+) PBMC. In this study, we extend our investigation of CpG ODN-induced TRAIL/Apo-2L expression and activity in PBMC to include CpG-A ODN. Of the two classes, IFN-alpha production and TRAIL/Apo-2L-mediated killing of tumor cells was greatest with CpG-A ODN. Surprisingly, CD3(+), CD14(+), CD19(+), and CD56(+) PBMC expressed high levels of TRAIL/Apo-2L following CpG-A ODN stimulation. When isolated, the CD19(+) PBMC (B cells) were able to kill tumor cells in a TRAIL/Apo-2L-dependent manner. As with CD14(+) PBMC, CD19(+) sorted B cells were capable of up-regulating TRAIL/Apo-2L expression when stimulated with IFN-alpha alone. Interestingly, agonist anti-CD40 mAb further enhanced the IFN-alpha-induced TRAIL/Apo-2L expression on CD19(+) B cells. These results are the first to demonstrate human B cell-mediated killing of tumor cells in a TRAIL/Apo-2L-dependent fashion.

TLR9 is localized in the endoplasmic reticulum prior to stimulation

In mammals, 10 TLRs recognize conserved pathogen-associated molecular patterns, resulting in the induction of inflammatory innate immune responses. One of these, TLR9, is activated intracellularly by bacterial DNA and synthetic oligodeoxynucleotides (ODN), containing unmethylated CpG dinucleotides. Following treatment with CpG ODN, TLR9 is found in lysosome-associated membrane protein type 1-positive lysosomes, and we asked which intracellular compartment contains TLR9 before CpG exposure. Surprisingly, we found by microscopy and supporting biochemical evidence that both transfected and endogenously expressed human TLR9 is retained in the endoplasmic reticulum. By contrast, human TLR4 trafficked to the cell surface, indicating that endoplasmic reticulum retention is not a property common to all TLRs. Because TLR9 is observed in endocytic vesicles following exposure to CpG ODN, our data indicate that a special mechanism must exist for translocating TLR9 to the signaling compartments that contain the CpG DNA.

Interleukin-2, but not interleukin-15, is required to terminate experimentally induced clonal T-cell anergy

It has been demonstrated that T cells stimulated with nucleosome-polyomavirus T-antigen (self-nonself) complexes, but not nucleosomes, activate autoimmune nucleosome-specific T cells. As these cells may be naïve, such observations do not show that anergic T cells are reactivated. To understand the regulation of autoimmunity, this is important to assess, and this is the focus of this study. T-cell anergy was induced by antigen stimulation in the presence of antibodies to the costimulatory molecules CD80/CD86. Requirements for the reactivation of anergic T cells were analysed by the ability of antigen and interleukin-2 (IL-2) or IL-15 to increase T-cell proliferation and IL-2 transcription. Data demonstrate that stimulation of T cells with T-antigen and anti-CD80/86 antibodies promotes long-lasting clonal T-cell anergy. While T-antigen did not reactivate anergic T cells, proliferation and upregulation of IL-2 gene transcription was initiated by stimulation with antigen, costimulation and IL-2 added to the cultures. Proliferation per se was not sufficient to promote the reactivation of anergic T cells, as both IL-2 and IL-15 induced proliferation, while antigen and IL-2, but not IL-15, upregulated IL-2 mRNA levels. These data demonstrate that the innate immune system and IL-2 are central to the initiation and termination of T-cell anergy.

CpG motifs are efficient adjuvants for DNA cancer vaccines

DNA vaccines can induce impressive specific cellular immune response (IR) when taking advantage of their recognition as pathogen-associated molecular patterns (PAMP) through Toll-like receptors (TLR) expressed on/in cells of the innate immune system. Among the many types of PAMP, immunostimulatory DNA, so-called CpG motifs, was shown to interact specifically with TLR9, which is expressed in plasmacytoid dendritic cells (pDC), a key regulatory cell for the activation of innate and adaptive IR. We now report that CpG motifs, when introduced into the backbone, are a useful adjuvant for plasmid-based DNA (pDNA) vaccines to induce melanoma antigen-specific protective T cell responses in the Cloudman M3/DBA/2 model. The CpG-enriched pDNA vaccine induced protection against subsequent challenge with melanoma cells at significantly higher levels than its parental unmodified vector. Preferential induction of an antigen-specific, protective T cell response could be demonstrated by (i) induction of antigen-dependent tumor cell protection, (ii) complete loss of protection by in vivo CD4+/CD8+T cell- but not NK cell-depletion, and (iii) the detection of antigen-specific T cell responses but not of relevant NK cell activity in vitro. These results demonstrate that employing PAMP in pDNA vaccines improves the induction of protective, antigen-specific, T cell-mediated IR.

Enhancement of the host immune responses in cutaneous T-cell lymphoma by CpG oligodeoxynucleotides and IL-15

Patients with advanced cutaneous T-cell lymphoma (CTCL) exhibit profound defects in cell-mediated immunity. Host immune functions appear to play an integral role in mediating disease-controlling responses in CTCL, therefore we investigated the effects of synthetic oligode-oxynucleotides with CpG motifs (CpG ODN), which have been recognized as immune stimulatory by virtue of activation of dendritic cells (DCs) following binding to Toll-like receptor (TLR) 9. Peripheral blood mononuclear cells (PBMCs) from patients with advanced CTCL (erythroderma with circulating malignant T cells) and healthy volunteers were cultured with either CpG-A or CpG-B ODN. Patients' PBMCs exhibited marked induction of interferon-alpha (IFN-alpha) release following culture with CpG-A. Similarly significant activation of NK cells and CD8 T cells occurred as assessed by up-modulation of CD69 expression and by natural killer lytic activity. Nevertheless, the PBMCs of patients exhibited blunted responses to CpG-A compared to healthy volunteers. In such cases, IL-15 was capable of producing levels of NK activation that were superior to CpG-A, while the combined effects of CpG-A plus IL-15 induced maximal activation of NK cells and further enhanced activation of CD8 T cells. These findings have important implications for the potential enhancement of antitumor immunity among patients with advanced CTCL.

Immunostimulatory CpG oligodeoxynucleotide confers protection in a murine model of infection with Burkholderia pseudomallei

Although CpG oligodeoxynucleotides (CpG ODNs) are known to enhance resistance against infection in a number of animal models, little is known about the CpG-induced protection against acute fatal sepsis such as that associated with the highly virulent bacterium Burkholderia pseudomallei. We previously demonstrated in an in vitro study that immunostimulatory CpG ODN 1826 enhances phagocytosis of B. pseudomallei and induces nitric oxide synthase and nitric oxide production by mouse macrophages. In the present study, CpG ODN 1826 given intramuscularly to BALB/c mice 2 to 10 days prior to B. pseudomallei challenge conferred better than 90% protection. CpG ODN 1826 given 2 days before the bacterial challenge rapidly enhanced the innate immunity of these animals, judging from the elevated serum levels of interleukin-12 (IL-12)p70 and gamma interferon (IFN-gamma) over the baseline values. No bacteremia was detected on day 2 in 85 to 90% of the CpG-treated animals, whereas more than 80% of the untreated animals exhibited heavy bacterial loads. Although marked elevation of IFN-gamma was found consistently in the infected animals 2 days after the bacterial challenge, it was ameliorated by the CpG ODN 1826 pretreatment (P = 0.0002). Taken together, the kinetics of bacteremia and cytokine profiles presented are compatible with the possibility that protection by CpG ODN 1826 against acute fatal septicemic melioidosis in this animal model is associated with a reduction of bacterial load and interference with the potential detrimental effect of the robust production of proinflammatory cytokines associated with B. pseudomallei multiplication.

Minimal toxicity of stabilized compacted DNA nanoparticles in the murine lung

Nanoparticles containing DNA compacted with poly-l-lysine modified on an N-terminal cysteine with polyethylene glycol can effectively transfect cells of the airway epithelium when applied by the luminal route. To evaluate the toxicity of these nanoparticles, we administered 10 and 100 microg DNA compacted into nanoparticles suspended in normal saline by the intranasal route to mice and determined the pulmonary and systemic responses to this challenge, compared to administration of saline alone, and in some experiments, compared to administration of naked DNA, Escherichia coli genomic DNA, or lipofectin-complexed naked DNA. There was no systemic response to either dose of nanoparticles in serum chemistries, hematologic parameters, serum complement, IL-6, or MIP-2 levels or in the activity, growth, and grooming of the mice. Nanoparticles containing 10 microg DNA induced responses comparable to saline in all measures, including BAL cell counts and differentials and cytokine levels and histology. However, mice dosed with 100 microg DNA in nanoparticles had modest increases in BAL neutrophils 48 and 72 h after dosing, modest increases in BAL IL-6 and KC beginning 24 and 48 h, respectively, after dosing, and, on histology of the lung, a trace to 1+ mononuclear cell infiltrates about the pulmonary veins at 48 h, which were markedly reduced by 10 days and gone by 28 days after dosing. BAL neutrophil and cytokine responses were no greater than those entrained by naked DNA for up to 24 h. However, compared to administration of only 10 microg E. coli genomic DNA, the response to compacted DNA was much less. A low dose of lipofectin-complexed DNA (5 microg DNA) induced the same response as 20-fold higher doses of DNA nanoparticles. These data indicate that DNA nanoparticles have no measurable toxic effect at a dose of 10 microg and a very modest effect, which is not limiting, at a dose of 100 microg, which gives maximal gene expression. This favorable toxicity profile encourages development of stabilized compacted DNA for airway administration.

IL-18 gene therapy develops Th1-type immune responses in Leishmania major-infected BALB/c mice: is the effect mediated by the CpG signaling TLR9?

IL-18 regulates either Th1 or Th2 responses depending on the cytokine microenvironment. Administration of recombinant IL-18 (rIL-18) alone does not promote Th1 response, but rather induces Th2 response and exacerbates Leishmania major infection in susceptible BALB/c mice. Here, we treated BALB/c mice with an IL-18-expressing plasmid by using a gene gun weekly after L. major infection. This gene therapy resulted in improved pathogenic process and preferential induction of Th1 responses by inducing the expression of IL-12 p40, but treatment with rIL-18 did not. Notably, simultaneous administration of rIL-18 with an empty plasmid vector rendered BALB/c mice resistant to the infection, despite the fact that treatment with either rIL-18 alone or the plasmid vector alone did not influence the susceptibility. The synergistic role of the vector with rIL-18 was found to depend on CpG motifs, which enhanced expression of proinflammatory cytokines, especially IL-12, from APCs through Toll-like receptor (TLR) 9 ligation. Treatment with methylated plasmid vector in which CpG was disrupted could no longer prevent the disease development in coadministration with rIL-18. Taken together, IL-18 gene therapy was shown to develop Th1-type protective immunity in L. major-infected BALB/c mice without the requirement of exogenous IL-12, probably via CpG-TLR9 signaling pathway.

Toll-like receptor 9 signaling activates NF-kappaB through IFN regulatory factor-8/IFN consensus sequence binding protein in dendritic cells

Unmethylated CpG DNA binds to the Toll-like receptor 9 (TLR9) and activates NF-kappaB to induce cytokine genes in dendritic cells (DCs). IFN regulatory factor (IRF)-8/IFN consensus sequence binding protein is a transcription factor important for development and activation of DCs. We found that DCs from IRF-8(-/-) mice were unresponsive to CpG and failed to induce TNF-alpha and IL-6, targets of NF-kappaB. Revealing a signaling defect selective for CpG, these cytokines were robustly induced in IRF-8(-/-) DCs in response to LPS that signals through TLR4. IRF-8(-/-) DCs expressed TLR9, adaptor myeloid differentiation factor 88, and other signaling molecules, but CpG failed to activate NF-kappaB in -/- cells. This was due to the selective inability of -/- DCs to activate I-kappaB kinase alphabeta, the kinases required for NF-kappaB in response to CpG. IRF-8 reintroduction fully restored CpG activation of NF-kappaB and cytokine induction in -/- DCs. Together, TLR signals that activate NF-kappaB are diverse among different TLRs, and TLR9 signaling uniquely depends on IRF-8 in DCs.

Transcriptional Regulation of the Human TLR9 Gene

To clarify the molecular basis of human TLR9 (hTLR9) gene expression, the activity of the hTLR9 gene promoter was characterized using the human myeloma cell line RPMI 8226. Reporter gene analysis and EMSA demonstrated that hTLR9 gene transcription was regulated via four cis-acting elements, cAMP response element, 5'-PU box, 3'-PU box, and a C/EBP site, that interacted with the CREB1, Ets2, Elf1, Elk1, and C/EBPalpha transcription factors. Other members of the C/EBP family, such as C/EBPbeta, C/EBPdelta, and C/EBPepsilon, were also important for TLR9 gene transcription. CpG DNA-mediated suppression of TLR9 gene transcription led to decreased binding of the trans-acting factors to their corresponding cis-acting elements. It appeared that suppression was mediated via c-Jun and NF-kappaB p65 and that cooperation among CREB1, Ets2, Elf1, Elk1, and C/EBPalpha culminated in maximal transcription of the TLR9 gene. These findings will help to elucidate the mechanism of TLR9 gene regulation and to provide insight into the process by which TLR9 evolved in the mammalian immune system.

Flt-3 ligand reverses late allergic response and airway hyper-responsiveness in a mouse model of allergic inflammation

Flt3 ligand (Flt3-L) is a growth factor for dendritic cells and induces type 1 T cell responses. We recently reported that Flt3-L prevented OVA-induced allergic airway inflammation and suppressed late allergic response and airway hyper-responsiveness (AHR). In the present study we examined whether Flt3-L reversed allergic airway inflammation in an established model of asthma. BALB/c mice were sensitized and challenged with OVA, and AHR to methacholine was established. Then mice with AHR were randomized and treated with PBS or 6 microg of Flt3-L i.p. for 10 days. Pulmonary functions and AHR to methacholine were examined after rechallenge with OVA. Treatment with Flt3-L of presensitized mice significantly suppressed (p < 0.001) the late allergic response, AHR, bronchoalveolar lavage fluid total cellularity, absolute eosinophil counts, and inflammation in the lung tissue. There was a significant decrease in proinflammatory cytokines (TNF-alpha, IL-4, and IL-5) in bronchoalveolar lavage fluid, with a significant increase in serum IL-12 and a decrease in serum IL-5 levels. There was no significant effect of Flt3-L treatment on serum IL-4 and serum total IgE levels. Sensitization with OVA significantly increased CD11b(+)CD11c(+) cells in the lung, and this phenomenon was not significantly affected by Flt3-L treatment. These data suggest that Flt3-L can reverse allergic airway inflammation and associated changes in pulmonary functions in murine asthma model.

Approaches for the sequence-specific knockdown of mRNA

Over the past 25 years there have been thousands of published reports describing applications of antisense nucleic acid derivatives for targeted inhibition of gene function. The major classes of antisense agents currently used by investigators for sequence-specific mRNA knockdowns are antisense oligonucleotides (ODNs), ribozymes, DNAzymes and RNA interference (RNAi). Whatever the method, the problems for effective application are remarkably similar: efficient delivery, enhanced stability, minimization of off-target effects and identification of sensitive sites in the target RNAs. These challenges have been in existence from the first attempts to use antisense research tools, and need to be met before any antisense molecule can become widely accepted as a therapeutic agent.

The potential of immunostimulatory CpG DNA for inducing immunity against genital herpes: opportunities and challenges

Herpes simplex virus type 2 (HSV-2) invades human genital tract mucosa and following local replications can be rapidly transmitted via peripheral nerve axons to the sacral ganglia where it can establish latency. Reactivation of the latent viral reservoir results in recurrent ulcers in the genital region. Innate immunity, the first line of defence during both primary and recurrent genital herpes infections, is crucial during the period of acute infection to limit early virus replication and to facilitate the development of an appropriate specific acquired immunity. Recent developments in immunology reveal that the mammalian innate immune systems use Toll-like receptor (TLR) to specifically sense evolutionary conserved molecules such as bacterial DNA in pathogens. Recently, local-vaginal delivery of CpG containing oligodeoxynucleotide (ODN), a synthetic mimic of bacterial DNA, holds substantial promise as a strong inducer of innate immunity against genital herpes infections in the animal models of the disease. These preclinical observations provide a scientific ground work for introduction of this novel intervention strategy to clinic. This review aims to highlight recent developments and future challenges in use of immunostimulatory CpG ODN for inducing immunity against genital herpes infection and disease.

Epicutaneous application of CpG oligodeoxynucleotides with peptide or protein antigen promotes the generation of CTL

Immunostimulatory oligodeoxynucleotides (ODN) are effective adjuvants in the induction of humoral and cellular immune responses when administered parenterally with antigen. The skin has recently become a target organ for the design of non-invasive vaccine technologies. Using ovalbumin (OVA) as a model antigen, we demonstrate that the application of ODN sequences to tape-stripped skin promotes the induction of potent cytotoxic T lymphocyte (CTL) responses to co-administered peptide. Induction of peptide-specific CTL required the presence of CpG motifs within the ODN. CTL afforded tumor protection against a tumor expressing an immunodominant OVA CTL epitope. CTL could also be induced to whole protein administered onto the skin. Differential CpG sequence activity was noted with respect to the induction of CTL to epicutaneous protein with an ODN sequence containing a poly-G motif having an optimal effect. Peptide-specific CTL could be detected in the peripheral blood as early as 6 d after a single immunization. These results highlight the potential of the bare skin as a route for vaccine development and indicate an important role for immunostimulatory ODN as adjuvants to generate functional CTL with the help of the skin immune system.

CpG and double-stranded RNA trigger human NK cells by Toll-like receptors: induction of cytokine release and cytotoxicity against tumors and dendritic cells

Toll-like receptors (TLRs) are pattern-recognition receptors responsible for triggering cells of innate immunity. In this study we investigated the expression and function of TLRs 3 and 9 in human natural killer (NK) cells. In the presence of IL-12, freshly isolated NK cells responded to double-stranded RNA or unmethylated CpG DNA and expressed CD69 and CD25 activation markers. Because both markers were expressed by virtually all NK cells, this would suggest that most of them can be triggered by TLRs. Remarkably, NK cell stimulation also resulted in the induction of their functional program as revealed by IFN-gamma and tumor necrosis factor-alpha release and by up-regulation of cytolytic activity against tumor cells. IL-8 could efficiently substitute IL-12 in supporting NK cell responses to TLR-mediated stimulation. Importantly, freshly isolated NK cells acquired the ability to lyse immature dendritic cells after stimulation with double-stranded RNA and IL-12. However, responses to these stimuli were not restricted to fresh NK cells, because significant responses were also detected in polyclonal NK cells cultured in the presence of exogenous IL-2 for several weeks. The analysis of NK cell clones revealed some degree of heterogeneity in the ability to respond to TLR stimulation also among NK clones derived from a single donor. These data suggest that stimuli acting on TLR not only activate immature dendritic cells to release IL-12 but also render NK cells capable of receiving triggering signals from pathogen-associated molecules, thus exerting a regulatory control on the early steps of innate immune responses against infectious agents.

Impact of modifications of heterocyclic bases in CpG dinucleotides on their immune-modulatory activity

Synthetic phosphorothioate oligodeoxynucleotides (ODN) bearing unmethylated CpG motifs can mimic the immune-stimulatory effects of bacterial DNA and are recognized by Toll-like receptor 9 (TLR9). Past studies have demonstrated that nucleotide modifications at positions at or near the CpG dinucleotides can severely affect immune modulation. However, the effect of nucleotide modifications to stimulate human leukocytes and the mechanism by which chemically modified CpG ODN induce this stimulation are not well understood. We investigated the effects of CpG deoxyguanosine substitutions on the signaling mediated by human TLR9 transfected into nonresponsive cells. ODN incorporating most of these substitutions stimulated detectable TLR9-dependent signaling, but this was markedly weaker than that induced by an unmodified CpG ODN. One of the most active ODN tested contained deoxyinosine for deoxyguanosine substitutions (CpI ODN), but its relative activity to induce cytokine secretion on mouse cells was much weaker than on human cells. The activity was dependent on TLR9, as splenocytes from mice genetically deficient in TLR9 did not respond to CpI ODN stimulation. It is surprising that CpI ODN were nearly as strong as CpG ODN for induction of human B cell stimulation but were inferior to CpG ODN in their ability to induce T helper cell type 1 effects. These data indicate that certain deoxyguanosine substitutions in CpG dinucleotides are tolerated to stimulate a TLR9-mediated immune response, but this response is insufficient to induce optimal interferon-alpha-mediated effects, which depend on the presence of an unmodified CpG dinucleotide. These studies provide a structure-activity relationship for TLR9 agonist compounds with diverse immune effects.

Combination of a CpG-oligodeoxynucleotide and a topoisomerase I inhibitor in the therapy of human tumour xenografts

The study was conducted to investigate the effects of a novel therapeutic approach, i.e. the combination of chemotherapy and immunotherapy, against a human prostate carcinoma xenograft. A topoisomerase I inhibitor, topotecan, and CpG-containing oligodeoxynucleotides (CpG-ODN) were combined. Athymic mice bearing the PC-3 human prostate carcinoma were treated with the maximum tolerated dose (MTD) of topotecan (3 weekly treatments) and with repeated treatments of CpG-ODN (40 and 20 microg/mouse); tumour growth and lethal toxicity were monitored. Topotecan effect on CpG-ODN-induced production of interleukin (IL) 12, interferon (IFN)-gamma and tumour necrosis factor-alpha was also assessed. Since topotecan pretreatment differentially influenced CpG-ODN-induced production of IL-12 and IFN-gamma, the antitumour effects of the two therapies were investigated in a sequential (full topotecan regimen followed by CpG-ODN) or in an alternating sequence (starting with CpG-ODN). Topotecan inhibited PC-3 tumour growth, inducing 95% tumour volume inhibition. All combined treatments resulted in a significant delay in tumour growth, compared to the effects in topotecan-treated mice (P<0.01, by analysis of tumour growth curves). The combination regimens were well tolerated, except for the alternating sequence of 40 microg CpG-ODN and topotecan, which resulted in three out of eight toxic deaths. This alternating sequence was highly toxic even when another cytotoxic drug (doxorubicin) was used in healthy mice. In conclusion, the combination of topotecan and CpG-ODN increased antitumour effects over chemotherapy alone in the growth of a human prostate carcinoma xenograft. Administration sequence was critical to the combination toxicity: the complete regimen of the cytotoxic drug followed by repeated administrations of the immunomodulator seemed the most promising for further investigations.

Cutting edge: activation of Toll-like receptor 2 induces a Th2 immune response and promotes experimental asthma

Recognition of microbial components by APCs and their activation through Toll-like receptors (TLR) leads to the induction of adaptive immune responses. In this study, we show that activation of TLR2 by its synthetic ligand Pam3Cys, in contrast to activation of TLR9 by immunostimulatory DNA (ISS-ODN), induces a prominent Th2-biased immune response. Activation of APCs by Pam3Cys resulted in the induction of Th2-associated effector molecules like IL-13, and IL-1beta, GM-CSF and up-regulation of B7RP-1, but low levels of Th1-associated cytokines (IL-12, IFNalpha, IL-18, IL-27). Accordingly, TLR2 ligands aggravated experimental asthma. These data indicate that the type of TLR stimulation during the initial phase of immune activation determines the polarization of the adaptive immune response and may play a role in the initiation of Th2-mediated immune disorders, such as asthma.

The RNA helicase RIG-I has an essential function in double-stranded RNA-induced innate antiviral responses

Intracellular double-stranded RNA (dsRNA) is a chief sign of replication for many viruses. Host mechanisms detect the dsRNA and initiate antiviral responses. In this report, we identify retinoic acid inducible gene I (RIG-I), which encodes a DExD/H box RNA helicase that contains a caspase recruitment domain, as an essential regulator for dsRNA-induced signaling, as assessed by functional screening and assays. A helicase domain with intact ATPase activity was responsible for the dsRNA-mediated signaling. The caspase recruitment domain transmitted 'downstream' signals, resulting in the activation of transcription factors NF-kappaB and IRF-3. Subsequent gene activation by these factors induced antiviral functions, including type I interferon production. Thus, RIG-I is key in the detection and subsequent eradication of the replicating viral genomes.

Toll-like receptor 9-dependent and -independent dendritic cell activation by chromatin-immunoglobulin G complexes

Dendritic cell (DC) activation by nucleic acid-containing immunoglobulin (Ig)G complexes has been implicated in systemic lupus erythematosus (SLE) pathogenesis. However, the mechanisms responsible for activation and subsequent disease induction are not completely understood. Here we show that murine DCs are much more effectively activated by immune complexes that contain IgG bound to chromatin than by immune complexes that contain foreign protein. Activation by these chromatin immune complexes occurs by two distinct pathways. One pathway involves dual engagement of the Fc receptor FcgammaRIII and Toll-like receptor (TLR)9, whereas the other is TLR9 independent. Furthermore, there is a characteristic cytokine profile elicited by the chromatin immune complexes that distinguishes this response from that of conventional TLR ligands, notably the induction of BAFF and the lack of induction of interleukin 12. The data establish a critical role for self-antigen in DC activation and explain how the innate immune system might drive the adaptive immune response in SLE.

Nonviral DNA vectors for immunization and therapy: design and methods for their obtention

The use of plasmid DNA for vaccination and therapy is a relatively novel technology, with advantages and limitations as with other gene transfer techniques. The technology is based on DNA vectors designed for administering genes coding for relevant proteins into a given organism, fulfilling requirements of the regulatory agencies that once properly formulated and delivered the desired vaccine/therapeutic effect can be achieved. Starting from conventional plasmid DNA vectors currently tested in clinical trials, improvement resulted in bacterial element-less vectors, increasing the complexity of the developmental process. The present review focuses on systems described for generating these nonviral DNA vectors for immunization and therapy from bacterial hosts (conventional and conditionally replicating plasmids, nonreplicating minicircles, and linear dumbbell-shaped expression cassettes) in vivo or in vitro. Additionally, nontherapeutic genetic sequences with a negative or positive effect according to the specific application are described, bringing a better comprehension of the technology's state of the art.

DNA fusion gene vaccines against cancer: from the laboratory to the clinic

Vaccination against target antigens expressed by cancer cells has now become a realistic goal. DNA vaccines provide a direct link between identification of genetic markers in tumors and vaccine formulation. Simplicity of manufacture facilitates construction of vaccines against disease subsets or even for individual patients. To engage an immune system that exists to fight pathogens, we have developed fusion gene vaccines encoding tumor antigens fused to pathogen-derived sequences. This strategy activates high levels of T-cell help, the key to induction and maintenance of effective immunity. We have dissected the immunogenic tetanus toxin to obtain specific sequences able to activate antibody, CD4+, or CD8+ T cells to attack selected fused tumor antigens. Principles established in preclinical models are now being tested in patients. So far, objective immune responses against idiotypic antigen of neoplastic B cells have been observed in patients with B-cell malignancies and in normal transplant donors. These responses provide a platform for testing physical methods to improve DNA delivery and strategies to boost responses. For cancer, demands are high, because vaccines have to activate powerful immunity against weak antigens, often in a setting of immune damage or tolerance. Vaccination strategies against cancer and against microbes are sharing knowledge and technology for mutual benefit.

CpG oligodeoxynucleotides improve the survival of pregnant and fetal mice following Listeria monocytogenes infection

Listeria infection during pregnancy can cause the death of both mother and fetus. Previous studies established that immunostimulatory CpG oligodeoxynucleotides (ODN) increase the resistance of healthy adult mice to many infectious pathogens, including Listeria monocytogenes. This study examines whether the innate immune response elicited by CpG ODN can reduce the susceptibility of pregnant mice to lethal listeria challenge. The results indicate that CpG ODN treatment significantly improves maternal survival and reduces pathogen transmission to offspring. CpG ODN administered during pregnancy did not induce abortion, birth defects, or reduce the size or health of litters. These findings suggest that CpG ODN may provide a safe and effective means of improving the health of mothers and fetuses during pregnancy.

Polymyxin B enhances ISS-mediated immune responses across multiple species

The immunostimulatory effects of bacterial DNA on mammalian cells have been localized to unmethylated CpG motifs, and synthetic CpG-containing oligodeoxynucleotides that mimic these effects are known as immunostimulatory sequences (ISS). We have found that the polycationic antibiotic, polymyxin B (PMXB), associates with ISS and serum albumin in vitro and forms microparticles that greatly increase the activity of ISS on plasmacytoid dendritic cells (PDCs). Specifically, ISS/PMXB greatly enhanced IFN-alpha production from PDCs and other activities downstream of IFN-alpha, including IFN-gamma secretion, NK lytic activity, and the expression of genes dependent upon IFN-alpha/IFN-gamma. This amplification was specific for the IFN-alpha pathway since other ISS activities, including B cell proliferation, B cell IL-6 secretion, and PDC maturation, were not affected by PMXB. Both the polycationic peptide and lipophilic fatty acid side chain domains of PMXB, as well as the presence of a third party stabilizing agent such as albumin or Tween 85, were required for particle formation and enhanced ISS activity. The ISS-enhancing activity of PMXB was observed across multiple species (human, primate, and mouse) and in vivo (primate, mouse). These data illustrate the usefulness of formulating ISS with a cationic lipopeptide such as PMXB, which focuses and greatly amplifies the ISS-induced pathway of IFN-alpha-mediated responses.

Transcutaneous immunization induces mucosal CTLs and protective immunity by migration of primed skin dendritic cells

Transcutaneous immunization (TCI), the application of vaccines on the skin, induces robust systemic and mucosal antibodies in animal models and in humans. The means by which mucosal immune responses to vaccine antigens are elicited by TCI has not been well characterized. We examined the effect of TCI with an HIV peptide vaccine on the induction of mucosal and systemic CTL responses and protective immunity against mucosal challenge with live virus in mice. Robust HIV-specific CTL responses in the spleen and in the gut mucosa were detected after TCI. The responses were dependent upon the addition of an adjuvant and resulted in protection against mucosal challenge with recombinant vaccinia virus encoding HIV gp160. Although it is clear that adjuvant-activated DCs migrated mainly to draining lymph nodes, coculture with specific T cells and flow cytometry studies with DCs isolated from Peyer's patches after TCI suggested that activated DCs carrying skin-derived antigen also migrated from the skin to immune-inductive sites in gut mucosa and presented antigen directly to resident lymphocytes. These results and previous clinical trial results support the observation that TCI is a safe and effective strategy for inducing strong mucosal antibody and CTL responses.

Codon optimization and mRNA amplification effectively enhances the immunogenicity of the hepatitis C virus nonstructural 3/4A gene

We have recently shown that the NS3-based genetic immunogens should contain also hepatitis C virus (HCV) nonstructural (NS) 4A to utilize fully the immunogenicity of NS3. The next step was to try to enhance immunogenicity by modifying translation or mRNA synthesis. To enhance translation efficiency, a synthetic NS3/4A-based DNA (coNS3/4A-DNA) vaccine was generated in which the codon usage was optimized (co) for human cells. In a second approach, expression of the wild-type (wt) NS3/4A gene was enhanced by mRNA amplification using the Semliki forest virus (SFV) replicon (wtNS3/4A-SFV). Transient tranfections of human HepG2 cells showed that the coNS3/4A gene gave 11-fold higher levels of NS3 as compared to the wtNS3/4A gene when using the CMV promoter. We have previously shown that the presence of NS4A enhances the expression by SFV. Both codon optimization and mRNA amplification resulted in an improved immunogenicity as evidenced by higher levels of NS3-specific antibodies. This improved immunogenicity also resulted in a more rapid priming of cytotoxic T lymphocytes (CTLs). Since HCV is a noncytolytic virus, the functionality of the primed CTL responses was evaluated by an in vivo challenge with NS3/4A-expressing syngeneic tumor cells. The priming of a tumor protective immunity required an endogenous production of the immunogen and CD8+ CTLs, but was independent of B and CD4+ T cells. This model confirmed the more rapid in vivo activation of an NS3/4A-specific tumor-inhibiting immunity by codon optimization and mRNA amplification. Finally, therapeutic vaccination with the coNS3/4A gene using gene gun 6-12 days after injection of tumors significantly reduced the tumor growth in vivo. Codon optimization and mRNA amplification effectively enhances the overall immunogenicity of NS3/4A. Thus, either, or both, of these approaches should be utilized in an NS3/4A-based HCV genetic vaccine.

CpG DNA-mediated immune response in pulmonary endothelial cells

Although the CpG DNA immune response mediated by Toll-like receptor 9 (TLR9) has been extensively studied in a number of immune cells, the response to CpG DNA in endothelial cells (EC) is not well understood. In this study, we show that both mouse and rat lung EC display constitutive expression of TLR9 mRNA. Exposure to CpG DNA induced a potent proinflammatory response as manifested by an increased expression of IL-8 and ICAM-1 in mouse pulmonary EC. The proinflammatory response was sensitive to chloroquine, consistent with a role of endosomal contribution. A role for p38 MAPK and NF-kappaB pathway was apparent as the response was sensitive to inhibitors of p38 MAPK and NF-kappaB but was not affected by inhibitors of ERK1/2. A synergistic effect of CpG DNA and LPS on the inflammatory response is consistent with multiple TLR interaction in EC. This study suggests a possible role for CpG DNA-mediated EC immune response in the host defense system. It also has important implications in plasmid DNA-mediated pulmonary endothelium gene transfer.

CpG oligodeoxynucleotides activate HIV replication in latently infected human T cells

CpG oligodeoxynucleotides (CpG ODNs) stimulate immune cells via the Toll-like receptor 9 (TLR9). In this study, we have investigated the effects of CpG ODNs on latent human immunodeficiency virus (HIV) infection in human T cells. Treatment of the latently infected T cell line ACH-2 with CpG ODNs 2006 or 2040 stimulated HIV replication, whereas no effects were evident when ODNs without the CpG motif were used. CpG-induced virus reactivation was blocked by chloroquine, indicating the involvement of TLR9. In contrast to the responsiveness of ACH-2 cells, CpG ODNs failed to activate HIV provirus in the latently infected Jurkat clone J1.1. We also studied the effects of CpG ODNs on productive HIV infection and found enhancement of viral replication in A3.01 T cells, whereas again no stimulating effects were observed in Jurkat T cells. CpG ODN treatment activated NF-kappaB in ACH-2 cells, which was similarly triggered in uninfected A3.01 T cells following exposure to CpG ODNs, indicating that TLR9-induced signal transduction was not dependent on proviral infection. Our study demonstrates that CpG ODNs directly trigger the activation of NF-kappaB and reactivation of latent HIV in human T cells. Our results point to a novel role for CpG ODNs as stimulators of HIV replication and open new avenues to eradicate the latent viral reservoirs in HIV-infected patients treated with antiretroviral therapy.

CpG oligodeoxynucleotide induction of antiviral effector molecules in sheep

Immunostimulatory CpG oligodeoxynucleotide (ODN) can protect mice against infection by many pathogens but the mechanisms mediating disease protection are not well defined. Furthermore, the mechanisms of CpG ODN induced disease protection in vivo have not been investigated in other species. We investigated the induction of antiviral effector molecules in sheep treated with a class B CpG ODN (2007). Subcutaneous injection of ODN 2007 induced a dose-dependent increase in serum levels of the antiviral effector molecule, 2'5'-A synthetase. Peak levels of enzyme were observed 4 days following ODN injection and enzyme levels remained elevated for the following 3-5 days. Repeated ODN injections induced a more sustained elevation of serum 2'5'-A synthetase activity. Finally, formulation of ODN 2007 in emulsigen increased the level of serum 2'5'-A synthetase activity and this response was CpG-specific. Elevated serum 2'5'-A synthetase activity suggested that CpG ODN acted through the induction of either interferon (IFN)-alpha or IFN-gamma. ODN 2007 did not induce detectable levels of IFN-alpha or IFN-gamma when incubated with peripheral blood mononuclear cells, but both IFN-alpha and IFN-gamma were detected following stimulation of lymph node cells with ODN 2007. CpG ODN induction of 2'5'-A synthetase in vitro correlated with the secretion of both IFN-alpha and IFN-gamma. Furthermore, immunohistochemical staining of skin revealed a marked cellular infiltration at the site of ODN 2007 injection. This cellular infiltration was CpG-specific and consisted of primarily CD172(+) myeloid cells. Many of the cells recruited to the site of ODN 2007 injection expressed IFN-alpha and some IFN-gamma. These observations support the conclusion that localized cell recruitment and activation contribute to CpG ODN induction of antiviral effector molecules, such as interferon and 2'5'-A synthetase.

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) use in the treatment of bladder cancer was first reported in 1976, but the mechanism of the induced antitumor activity has still not been fully explained. BCG is a potent immunostimulant, normally producing a Th1 cytokine response, including IFN. Recent studies have shown CpG oligodeoxynucleotide induce tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression via IFN production. Given that Mycobacterial DNA contains high amounts of CpG motifs, we hypothesized that BCG's antitumor properties are akin to CpG oligodeoxynucleotide, where the cytokine response to BCG induces TRAIL up-regulation. Using ELISA, urine IFN-gamma, and TRAIL levels were initially undetectable in BCG therapy patients but were high after later induction treatments. More importantly, patients that responded to BCG therapy had significantly higher urine TRAIL levels, which killed bladder tumor cells in vitro versus nonresponders. Flow cytometry of fresh urine revealed TRAIL-expressing neutrophils. Given these data, we propose TRAIL plays a role in BCG-induced antitumor effects.

CCL17 and IL-10 as effectors that enable alternatively activated macrophages to inhibit the generation of classically activated macrophages

Classically activated macrophages (CAMphi) have been described as a major effector cell on the host's innate immunities. However, CAMphi are not generated in immunocompromised hosts whose alternatively activated macrophages (AAMphi) predominate. In this study, the mechanism by which AAMphi suppress the ability of resident macrophages (RMphi) to generate CAMphi was investigated. AAMphi were isolated from peritoneal exudates of mice 2 days after third-degree thermal injuries affecting 15% total body surface area. CAMphi were generated from RMphi (peritoneal Mphi from normal mice) through stimulation with CpG DNA, a typical CAMphi inducer. RMphi did not polarize to CAMphi when they were cultured with AAMphi in a dual-chamber Transwell even when supplemented with CpG DNA. In addition, RMphi stimulated with CpG DNA did not convert to CAMphi when they were cultured with the culture fluids of AAMphi (AAMphi Culture-Sup). AAMphi Culture-Sup contained IL-6, IL-10, CCL17, PGE(2), and TGF-beta. Among these, CCL17 and IL-10 inhibited CAMphi generation. The ability of AAMphi Culture-Sup to inhibit CAMphi generation was eliminated when the Culture-Sup was treated with a mixture of mAbs directed against CCL17 and IL-10. These results indicate that CCL17 and IL-10 released from AAMphi inhibit CAMphi generation from RMphi stimulated with CpG DNA.

CpG-DNA aided cross-priming by cross-presenting B cells

Covalent linkage of immunostimulatory CpG-DNA to OVA (CpG-OVA complex) results in CpG-DNA-aided cross-presentation of OVA by dendritic cells (DCs). In this study, we analyzed the thesis that CpG-OVA complexes may be cross-presented by B cells to route internalized Ag into the class I MHC presentation pathway. First, we describe that conjugation of CpG-DNA to OVA enhances up to 40-fold internalization of OVA by B cells, which in turn generate the CD8 T cell epitope SIINFEKL complexed to MHC class I, albeit less efficiently than DCs. Furthermore, upon internalization, CpG-DNA conjugated to OVA stimulates B cells to up-regulate costimulatory molecules and cytokines including IL-12. Adoptive transfer of CpG-OVA complex-loaded wild-type B cells cross-primes naive CD8 T cells both in wild-type mice and in MyD88-deficient mice. Overall, these findings disclose attributes of B cells, including cross-presentation of exogenous Ag and cross-priming of naive CD8 T cells that hitherto have been considered as hallmarks restricted to DCs.

DNA from probiotic bacteria modulates murine and human epithelial and immune function

BACKGROUND & AIMS

The intestinal epithelium must discriminate between pathogenic and nonpathogenic bacteria and respond accordingly. The aim of this study was to examine whether bacterial DNA can serve as the molecular basis for bacterial recognition.

METHODS

HT-29 monolayers were treated with various bacterial DNA and interleukin (IL)-8 secretion measured by enzyme-linked immunosorbent assay, nuclear factor kappaB activation by electrophoretic mobility shift assay and reporter assays, and IkappaB levels by Western blotting. Cytokine secretion in response to bacterial DNA was measured in murine colonic segments and splenocytes. IL-10-deficient mice were fed DNA from VSL probiotic compound daily for 2 weeks. Colons were removed and analyzed for cytokine production and inflammation.

RESULTS

HT-29 cells responded with IL-8 secretion to bacterial DNA in a differential manner. In the presence of proinflammatory stimuli, VSL3 DNA inhibited IL-8 secretion, reduced p38 mitogen-activated protein kinase activation, delayed nuclear factor kappaB activation, stabilized levels of IkappaB, and inhibited proteasome function. VSL3 DNA inhibited colonic interferon (IFN)-gamma secretion in mouse colons and also attenuated a Bacteroides vulgatus-induced IFN-gamma release from murine splenocytes. In mice, VSL3 DNA attenuated a systemic release of tumor necrosis factor alpha in response to Escherichia coli DNA injection. Treatment of IL-10-deficient mice with oral VSL3 DNA resulted in a reduction in mucosal secretion of tumor necrosis factor alpha and IFN-gamma and an improvement in histologic disease.

CONCLUSIONS

DNA from probiotic bacteria can limit epithelial proinflammatory responses in vivo and in vitro. Systemic and oral administration of VSL3 DNA ameliorates inflammatory responses.

CpG oligodeoxynucleotides improve the response to hepatitis B immunization in healthy and SIV-infected rhesus macaques

OBJECTIVE

The development of an immunogenic vaccine against hepatitis B virus (HBV) is particularly important for HIV-infected patients since shared epidemiological risks result in HIV-infected subjects having a high incidence of HBV, and coinfection with HBV increases the occurrence of hepatotoxicity with antiretroviral therapy. Although HBV vaccination is recommended to all HIV-positive patients, its efficacy in these patients is reduced.

METHODS

Healthy (n = 15) and SIV-infected (n = 17) rhesus macaques were immunized with Engerix B alone or combined with type D or type K CpG ODN. SIV plasma RNA levels were determined by a real time reverse transcriptase polymerase chain reaction and antibody titers to HBV surface antigen (HbsAg) were measured by enzyme-linked immunosorbent assay every 2 weeks.

RESULTS

In healthy macaques, adding D or K ODN to Engerix B accelerated and boosted the titer of the anti-HbsAg response. In SIV-infected macaques, Engerix B alone elicited no detectable antibody response but a significant response was seen when it was combined with K or D ODN. The antibody titer induced by vaccinating HIV-infected macaques was inversely correlated with their initial viral load, with animals having > 10(7) copies/ml being unable to mount a significant response. No adverse events or changes in SIV viral load were evident during the study.

CONCLUSIONS

These findings support the development of clinical studies to assess the use of CpG ODN as an adjuvant for HBV vaccination in healthy and immunocompromised HIV-infected subjects.

NF-kappaB- and c-Jun-dependent regulation of human cytomegalovirus immediate-early gene enhancer/promoter in response to lipopolysaccharide and bacterial CpG-oligodeoxynucleotides in macrophage cell line RAW 264.7

The cytomegalovirus immediate-early (CMV IE) gene enhancer/promoter regulates the expression of immediate-early gene products and initiation of CMV replication. TNF-alpha and lipopolysaccharide (LPS) strongly activate the promoter, possibly involving NF-kappaB. CpG-oligodeoxynucleotides (CpG-ODNs), which contain unmethylated CpG dinucleotides in the context of particular base sequences, have gained attention because of their stimulating effects, via NF-kappaB, which have a strong innate immune response. To study the effects of LPS and CpG-ODNs, as well as the mechanisms of their actions regarding CMV IE enhancer/promoter activation, we used a macrophage cell line, RAW 264.7. Stimulation of the cells with LPS or CpG-ODNs resulted in the activation of the CMV IE enhancer/promoter. We examined the involvement of NF-kappaB and c-Jun transcription factors by promoter deletion/site-specific mutation analysis and ectopic expression, and found them to have additive effects. Involvement of myeloid differentiation protein, an upstream regulator of NF-kappaB and c-Jun, was also investigated. Experimental results indicate that both LPS-induced and CpG-ODN-induced activations of CMV IE enhancer/promoter are mediated by Toll-like receptor signaling molecules. Several lines of evidence suggest the potential contribution of bacterial infection in CMV reactivation along with the potential application of CpG-ODNs in gene therapy as a stimulator for the optimal expression of target genes under the control of the CMV IE enhancer/promoter.

IL-12p70-dependent Th1 induction by human B cells requires combined activation with CD40 ligand and CpG DNA

The detection of microbial molecules via Toll-like receptors (TLR) in B cells is not well characterized. In this study, we found that both naive and memory B cells lack TLR4 (receptor for LPS) but express TLR9 (receptor for CpG motifs) and produce IL-6, TNF-alpha, and IL-10 upon stimulation with CpG oligonucleotides (ODN), synthetic mimics of microbial DNA. Consistent with the lack of TLR4, purified B cells failed to respond to LPS. Similar to CpG ODN, CD40 ligand (CD40L) alone induced IL-6, TNF-alpha, and IL-10. Production of these cytokines as well as IgM synthesis was synergistically increased when both CpG ODN and CD40L were combined. Unlike IL-6, TNF-alpha, and IL-10, the Th1 cytokine IL-12p70 was detected only when both CpG ODN and CD40L were present, and its induction was independent of B cell receptor cross-linking. CpG ODN did not increase the capacity of CD40L-activated B cells to induce proliferation of naive T cells. However, B cells activated with CpG ODN and CD40L strongly enhanced IFN-gamma production in developing CD4 T cells via IL-12. Together, these results demonstrate that IL-12p70 production in human B cells is under the dual control of microbial stimulation and T cell help. Our findings provide a molecular basis for the potent adjuvant activity of CpG ODN to support humoral immune responses observed in vivo, and for the limited value of LPS.

Incorporation of CpG oligodeoxynucleotide fails to enhance the protective efficacy of a subunit vaccine against Mycobacterium tuberculosis

Vaccines which offer better protection than BCG are now badly needed for controlling tuberculosis infection throughout the world. Immunological adjuvants capable of inducing a TH1 type of protective response are necessary to augment the immune response, particularly in the case of subunit vaccines. It is now well established that oligodeoxynucleotides (ODN) containing cytidine phosphate guanosine (CpG) motifs enhance cell-mediated responses in vivo by increasing the production of the TH1 cytokines IL-12 and interferon gamma (IFNgamma). To determine if this would improve subunit vaccination of mice CpG ODN were added to a subunit vaccine consisting of the culture filtrate proteins (CFP) of Mycobacterium tuberculosis H37Rv. It was observed that although adding CpG ODN to the vaccines promoted substantially increased IFNgamma production by lymph node cells draining sites of inoculation, this failed to translate after aerosol challenge into any degree of enhancement of bacterial clearance in the lungs, influx of IFN-positive T cells, or changes in histopathology. These data suggest that the vaccine enhancing effects of CpG ODN are relatively transient.

Immunobiology of mucosal HIV infection and the basis for development of a new generation of mucosal AIDS vaccines

Mucosal tissues are the primary site of natural HIV transmission and a major reservoir for HIV replication. Targeting immune responses to the mucosal entry site before viral dissemination could protect and also clear viral reservoirs. Recent understanding of mucosal HIV transmission and of chemokines and integrins in mucosal trafficking can aid design of new strategies to enhance AIDS vaccine efficacy.

Association of DNA quadruplexes through G:C:G:C tetrads. Solution structure of d(GCGGTGGAT)

The structure formed by the DNA sequence d(GCGGTGGAT) in a 100 mM Na(+) solution has been determined using molecular dynamics calculations constrained by distance and dihedral restraints derived from NMR experiments performed at isotopic natural abundance. The sequence folds into a dimer of dimers. Each symmetry-related half contains two parallel stranded G:G:G:G tetrads flanked by an A:A mismatch and by four-stranded G:C:G:C tetrads. Each of the two juxtaposed G:C:G:C tetrads is composed of alternating antiparallel strands from the two halves of the dimer. For each single strand, a thymine intersperses a double chain reversal connecting the juxtaposed G:G:G:G tetrads. This architecture has potential implications in genetic recombination. It suggests a pathway for oligomerization involving association of quadruplex entities through GpC steps.

Plasma cell differentiation and multiple myeloma

Microarray analyses and gene targeting have recently enhanced the understanding of factors involved in normal plasma cells and multiple myeloma. Plasma cells develop from marginal zone or germinal center B cells following stimulation by antigen, microbial products, TNF family signals and cytokines. Transcription factors, B-lymphocyte-induced maturation protein 1 (Blimp-1) and X-box binding protein 1 (XBP-1) are required for plasma cell development. They regulate sets of genes that induce immunoglobulin secretion, halt proliferation and block alternative B-cell fates. In multiple myeloma, transforming events lead to proliferation and survival, but programs for plasma cell differentiation and the inhibition of B-cell genes appear to be largely intact.

Innate immunity and toll-like receptors: clinical implications of basic science research

Humans are constantly exposed to a wide variety of microorganisms that can cause infection. In self-defense, the human host has evolved complex protective mechanisms, and Toll-like receptors (TLRs) have emerged as a central point in defense. These receptors bind molecular structures that are expressed by microbes but are not expressed by the human host, eg, lipopolysaccharides (LPS) or double-stranded RNA (dsRNA). Activation of these receptors initiates an inflammatory cascade that attempts to clear the offending pathogen and set in motion a specific adaptive immune response. Defects in sensing of pathogens may predispose the host to recurrent infections. The relative rarity of these syndromes of defective innate immunity, however, speaks to the redundancy in sensing of pathogens by the innate immune system. More common, polymorphisms in TLR4 are associated with increased predisposition to severe and recurrent infections but protection against atherosclerotic disease due to diminished inflammation. Toll-like receptor signaling may also contribute to the pathophysiology of disease and injure the host by activating a deleterious immune response such as in sepsis or inflammatory bowel disease (IBD). The focus of this article is to describe the role of TLRs in the innate immune response in health and disease.

Antitumor applications of stimulating toll-like receptor 9 with CpG oligodeoxynucleotides

Tumor immunotherapy has evolved from the use of crude bacterial extracts to chemically synthesized ligands for specific immune receptors, such as Toll-like receptors (TLRs). One of the most promising targets for therapeutic immune activation is TLR9, which detects unmethylated CpG dinucleotides present in viral and prokaryotic genomes, which are generally methylated in host DNA. This review describes the immune effects of synthetic CpG oligonucleotides as TLR9 ligands and their applications in cancer immunotherapy.

Enhancement of both cellular and humoral responses to genetic immunization by co-administration of an antigen-expressing plasmid and a plasmid encoding the pro-apoptotic protein Bax

BACKGROUND

Transfecting cells with plasmid DNA encoding the protein Bax causes programmed cell death (apoptosis) and results in the formation of cell fragments (apoptotic bodies). It has been known for some time that when dendritic cells phagocytose apoptotic bodies derived from tumor cells, an immune response to tumor antigens can be generated.

METHODS

Gene expression in the skin was evaluated after intradermal injection with plasmids encoding fluorescent proteins. Plasmids encoding foreign antigens were co-injected intradermally with Bax-encoding plasmids or control plasmids to elicit both humoral and cytotoxic immunity. Immune responses to the antigens were assessed by ELISA and cytotoxicity assays.

RESULTS

We demonstrate here that injection of a mixture of reporter gene plasmids into the skin results in the expression of both plasmids in the large majority of the transfected cells. It is known that immune responses to multiple antigens can be elicited by co-injection of separate individual plasmids. When mice were injected with equal quantities of two antigenic plasmids and either the Bax plasmid or a noncoding control plasmid, antibody responses were increased 4-8-fold in the Bax group. Similarly, cytotoxic T lymphocyte (CTL) responses in the Bax group showed an 80% increase in the number of lytic units per million cells.

CONCLUSIONS

This data shows that simply including the apoptosis-inducing Bax plasmid along with antigen-expressing plasmids may provide a significant enhancement of immune responses to DNA vaccines. Published in 2004 by John Wiley & Sons, Ltd.

BACTERIAL DNA AND RNA INDUCE RAT CARDIAC MYOCYTE CONTRACTION DEPRESSION IN VITRO

Sepsis and septic shock, the systemic immunologic and pathophysiologic response to overwhelming infection, are associated with perturbation of a variety of metabolic cell pathways and with multiple organ failure (MOF) including cardiac depression. This depression has been attributed to the effect of several circulating and locally produced proinflammatory mediators. Recent data suggest that bacterial nucleic acids can produce profound systemic inflammatory responses characterized by circulatory shock in intact animals. In this study, bacterial DNA and RNA derived from pathogenic clinical S. aureus and E. coli isolates are shown to induce early concentration-dependent depression of maximum extent and peak velocity of contraction of electrically paced neonatal rat ventricular myocytes in culture. Significant but more modest depression was generated by a nonpathogenic E. coli isolate. Pretreatment with a DNase or RNase abrogated this effect. Further, synthetic, double-stranded RNA (dsRNA) also induced concentration-dependent depression of myocyte contraction, with the effect also being prevented by pretreatment with RNase. These data suggest that bacterial DNA and RNA may contribute to myocardial depression during bacterial sepsis and septic shock.