Activation of human B cells by phosphorothioate oligodeoxynucleotides

Heterogeneity in the human response to immunostimulatory CpG oligodeoxynucleotides

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs trigger an immune response characterized by proliferation, B-cell activation, and cytokine production. CpG ODNs show promise in animal models as vaccine adjuvants and anti-allergens and for the treatment of infectious diseases and cancer. Several different CpG motifs capable of stimulating human cells have been identified, and several CpG-containing ODNs are now in various stages of clinical trials. However, little is known of the comparative magnitude or breadth of the immune responses these CpG ODNs elicit. This work compares the proliferative, IgM, and IL-6 response of PBMCs from 100 normal donors to a panel of 11 ODNs selected as highly active from over 100 phosphorothioate ODNs. While PBMCs from every donor responded to at least one member of the ODN panel, no single ODN was optimally stimulatory in all subjects or for all responses. A mixture of ODNs with complementary activities induced significantly broader stimulation of donor PBMCs than any single ODN, providing a rational basis for proceeding into clinical trials with such a mixture.

A phase I study of the safety and immunogenicity of recombinant hepatitis B surface antigen co-administered with an immunostimulatory phosphorothioate oligonucleotide adjuvant

Certain oligodeoxynuclotides with CpG motifs provide enhanced immune response to co-delivered antigens. We performed a phase I, observer-blinded, randomized study in healthy anti-hepatitis B surface antigen (anti-HBsAg) antibody negative adults to explore safety and immunogenicity of co-injection of recombinant HBsAg combined with an immunostimulatory DNA sequence (ISS) 1018 ISS. Four ISS dosage groups (N=12 per group) were used: 300, 650, 1000 or 3000 microg. For each group, two controls received 20 microg HBsAg alone, two controls received ISS alone, and eight subjects received ISS+20 microg HBsAg. Subjects received two doses 8 weeks apart. Injection site reactions (tenderness and pain on limb movement) were more frequent at higher ISS+HBsAg doses but were mainly mild and of short duration. Higher anti-HBsAg antibody levels were associated with higher ISS doses. Four weeks after the first dose, a seroprotective titer (>or=10 mIU/ml) was noted for 0, 25, 75, and 87.5% of subjects by increasing ISS dose group (P<0.05) for those who received ISS+HBsAg; 1 month after the second dose this increased to 62.5, 100, 100, and 100%, respectively. Geometric mean anti-HBsAg antibody levels by increasing ISS+HBsAg dose were 1.22, 5.78, 24.75, and 206.5 mIU/ml after the first dose and 65.37, 877.6, 1545, and 3045 mIU/ml after the second dose. We conclude that 1018 ISS+HBsAg was well tolerated and immunogenic in this phase I study in healthy adults and may offer the potential for enhancement of hepatitis B virus (HBV) immunization and protection after one or two doses or in individuals who fail to respond to the standard vaccine regimen.

Divergent synthetic nucleotide motif recognition pattern: design and development of potent immunomodulatory oligodeoxyribonucleotide agents with distinct cytokine induction profiles

Unmethylated CpG dinucleotides present within certain specific sequence contexts in bacterial and synthetic DNA stimulate innate immune responses and induce cytokine secretion. Recently, we showed that CpG DNAs containing two 5'-ends, immunomers, are more potent in both regards. In this study, we show that an immunomer containing a synthetic CpR motif (R = 2'-deoxy-7-deazaguanosine) is a potent immunostimulatory agent. However, the profile of cytokine induction is different from that with immunomers containing a natural CpG motif. In general, a CpR immunomer induced higher interleukin (IL)-12 and lower IL-6 secretion. Compared with conventional CpG DNAs, both types of immunomers showed a rapid and enhanced activation of the transcription factor NF-kappaB in J774 cells. NF-kappaB activation by CpG DNA corresponded to degradation of IkappaBalpha in J774 cells. All three immunostimulatory oligonucleotides activated the p38 mitogen-activated protein kinase pathway as expected. Immunomers containing CpG and CpR motifs showed potent reversal of the antigen-induced Th2 immune response towards a Th1 type in antigen-sensitized mouse spleen cell cultures. Immunomers containing a CpR motif showed significant antitumor activity in nude mice bearing MCF-7 human breast cancer and U87MG glioblastoma xenografts. These studies suggest the ability for a divergent synthetic nucleotide motif recognition pattern of the receptor involved in the immunostimulatory pathway and the possibility of using synthetic nucleotides to elicit different cytokine response patterns.

The molecular basis for the lack of immunostimulatory activity of vertebrate DNA

Macrophages and B cells are activated by unmethylated CpG-containing sequences in bacterial DNA. The lack of activity of self DNA has generally been attributed to CpG suppression and methylation, although the role of methylation is in doubt. The frequency of CpG in the mouse genome is 12.5% of Escherichia coli, with unmethylated CpG occurring at approximately 3% the frequency of E. coli. This suppression of CpG alone is insufficient to explain the inactivity of self DNA; vertebrate DNA was inactive at 100 micro g/ml, 3000 times the concentration at which E. coli DNA activity was observed. We sought to resolve why self DNA does not activate macrophages. Known active CpG motifs occurred in the mouse genome at 18% of random occurrence, similar to general CpG suppression. To examine the contribution of methylation, genomic DNAs were PCR amplified. Removal of methylation from the mouse genome revealed activity that was 23-fold lower than E. coli DNA, although there is only a 7-fold lower frequency of known active CpG motifs in the mouse genome. This discrepancy may be explained by G-rich sequences such as GGAGGGG, which potently inhibited activation and are found in greater frequency in the mouse than the E. coli genome. In summary, general CpG suppression, CpG methylation, inhibitory motifs, and saturable DNA uptake combined to explain the inactivity of self DNA. The immunostimulatory activity of DNA is determined by the frequency of unmethylated stimulatory sequences within an individual DNA strand and the ratio of stimulatory to inhibitory sequences.

Oligodeoxynucleotides without CpG motifs work as adjuvant for the induction of Th2 differentiation in a sequence-independent manner

The outcomes of immune responses are regulated by various parameters including how Ags are handled by APCs. In this study, we describe the intrinsic immunomodulatory characteristics of oligodeoxynucleotides (ODNs) that improve the Ag presentation by APCs. ODNs (20-mer) containing CpG motifs induced strong Th1-skewed responses. In contrast, those without CpG motifs enhanced cytokine production by effector Th cells without particular skewing toward Th1 responses or induced the differentiation of unprimed CD4(+) T cells toward Th2 cells. These functional features were prominently envisaged when ODNs were conjugated to the Ag, and were underlain by the facilitated binding of ODN-conjugated Ag to Ia(+) cells. Despite the functional differences between ODNs with CpG motifs and those without CpG motifs, both ODNs bound to Ia(+) cells with similar affinity and kinetics. Immunoenhancing activities of the ODNs were not sequence-dependent; the characteristics, including the facilitation of Ag capture, enhancement of effector Th cell responses, and induction of Th2 cells, were shared by randomly synthesized ODNs conjugated to Ag. This is the first study suggesting that ODNs, independent of the sequences, enhance immune responses through the promoted capture of ODN-conjugated Ag by APCs.

Cycling B-CLL cells are highly susceptible to inhibition of the proteasome: involvement of p27, early D-type cyclins, Bax, and caspase-dependent and -independent pathways

OBJECTIVE

Although peripheral blood B-CLL cells are arrested in G0 phase of the cell cycle, a proliferating pool of cells in proliferation centers might be involved in disease progression. We have previously described an in vitro model of this proliferating pool of cells using B-CLL cells stimulated with immunostimulatory oligonucleotides (CpG-ODN) and interleukin-2. Lactacystin is a specific inhibitor of the proteasome and is a potent apoptosis inductor in resting peripheral B-CLL cells. In the present study, we investigated the effect of proteasome inhibition in proliferating B-CLL cells.

METHODS

The effect of proteasome inhibition was analyzed using thymidine incorporation, annexin V assays, and TUNEL staining. Immunoblots were performed to evaluate expression of proteins involved in cell cycle and apoptosis regulation.

RESULTS

Lactacystin blocked cell cycle progression in activated B-CLL cells and inhibited degradation of p27. Upregulation of cyclin D2 and D3 in activated B-CLL cells was inhibited while the expression of cdk2, cdk4, and cyclin E remained unchanged. Activated B-CLL cells were more susceptible to apoptosis induction as compared to resting B-CLL cells. Apoptosis induction was accompanied by cleavage of Bax, procaspase 8, procaspase 9, and procaspase 3. However, a broad-spectrum caspase inhibitor (z-VAD.fmk) only partially inhibited cell death although DNA degradation was completely inhibited.

CONCLUSION

Proteasome inhibition is highly effective in proliferating B-CLL cells and induces apoptosis using a caspase-dependent and -independent pathway.

Reduced faecal excretion of F4+-E coli by the intramuscular immunisation of suckling piglets by the addition of 1alpha,25-dihydroxyvitamin D3 or CpG-oligodeoxynucleotides

In this study it was analysed whether intramuscular (IM) immunisation of piglets with F4 during the suckling period could protect against oral challenge with F4(+)-Escherichia coli and whether addition of 1alpha,25(OH)(2)D(3) or CpG-ODN could improve this protection.F4-seronegative F4-receptor positive pigs were divided into four groups of five pigs each. The pigs were intramuscularly injected with F4 fimbriae only or supplemented with 1alpha,25(OH)(2)D(3) (D(3)-group) or CpG-ODN (CpG-group). The control group received PBS in IFA. Seven days after the second immunisation, all pigs were intragastrically inoculated with 1 x 10(10) CFU of F4(+)-E. coli. All F4-injected groups, showed a reduced faecal excretion of F4(+)-E. coli. However, this reduction was only statistically significant in the D(3)-group 2 days post challenge. Pigs in the latter group showed a secondary antibody response upon challenge, indicating that F4-primed memory B-cells were present in the gut-associated lymphoid tissues at that moment.CpG-ODN, on the other hand, did not enhance the F4-specific antibody response. However, CpG-ODN significantly increased the F4-specific as well as mitogen-induced proliferation of peripheral blood monomorphonuclear cells indicating a direct or indirect overall effect on T-lymphocytes. In conclusion, supplementation with 1alpha,25(OH)(2)D(3) or CpG-ODN improved protection against an F4(+)-E. coli infection. This protection was most obvious for 1alpha,25(OH)(2)D(3) and indicates its potential use in veterinary vaccines against enteropathogens.

Immune responses to hepatitis B surface antigen following epidermal powder immunization

Langerhans cells in the epidermis of skin are potent antigen-presenting cells that trigger the immune system to respond to invading microorganisms. We have previously shown that epidermal powder immunization with a powdered inactivated influenza virus vaccine, by targeting the Langerhans cell-rich epidermis, was more efficacious than deeper tissue injection using a needle and syringe. We now report enhanced humoral and cellular immune responses to recombinant hepatitis B surface antigen following epidermal powder immunization. We observed that epidermal powder immunization with unadjuvanted hepatitis B surface antigen elicited an antibody titre equivalent to that induced by the alum-adjuvanted vaccine delivered by intramuscular injection, suggesting that epidermal powder immunization can overcome the need for adjuvantation. We demonstrated that synthetic CpG oligonucleotides (CpG DNA) could be coformulated with hepatitis B surface antigen and delivered by epidermal powder immunization to further augment the antibody response and modulate T helper cell activities. Epidermal powder immunization of hepatitis B surface antigen formulated with CpG DNA formulations resulted in 1.5-2.0 logs higher IgG antibody titres than alum-adjuvanted commercial vaccines administered by intramuscular injection. Formulation of hepatitis B surface antigen with CpG DNA elicited an augmented IgG2a antibody response and increased frequency of IFN-gamma secreting cells. In addition, CpG DNA was found to activate epidermal Langerhans cells and stimulate the production of TNF-alpha and IL-12 cytokines by epidermal cells, explaining its strong adjuvant activity following epidermal powder immunization. These results show that epidermal powder immunization is a safe and effective method to deliver hepatitis B surface antigen and the addition of new adjuvants, such as CpG DNA, may further enhance the efficacy of this vaccine.

CpG penta- and hexadeoxyribonucleotides as potent immunomodulatory agents

We demonstrate a new design for immunomodulatory CpG DNA containing two sequences each with as few as five or six-nucleotides joined together via 3(')-3(') linkers. These do not require the -PuPu(Py)CGPyPy- hexameric motif generally found essential for CpG DNA immune stimulation. These novel, short-immunomers show potent immunostimulatory activity manifested by IL-12 and IL-6 secretion in murine spleen cell and PBMC cultures and splenomegaly in vivo. Short-immunomers show strong activation of NF-kappaB and stress-activated signaling pathways and induce cytokines in J774 cell cultures. The same sequences also induce cytokines in healthy human PBMC cultures whereas conventional CpG DNA requires different optimal sequences for murine and human immune cells. Additionally, short-immunomers inhibit IL-5 secretion and induce IFN-gamma secretion in conalbumin-sensitized mouse spleen cell cultures, suggesting reversal of established Th2 responses to Th1 type responses. Short-immunomer also inhibits growth of MCF-7 human tumor xenograft in nude mice. This is the first report of activity with such short DNA sequences and also of sequences lacking hexameric motifs proposed in earlier studies.

The binding of CpG-oligodeoxynucleotides to cell-surface and its immunostimulatory activity are modulated by extracellular acidic pH

Both the binding of CpG-oligodeoxynucleotides (CpG-ODNs) to cell-surface and its immunostimulatory activity were modulated by extracellular pH in present study. At neutral pH (pH 7.4), the binding of CpG-ODN to splenocyte-surface, as well as that of non-CpG-ODN, was competitively inhibited by non-specific DNA-Herring sperm DNA in a dose dependent manner, indicating their binding sites have no specificity for CpG-motif. When the extracellular pH shifted to acidic (pH 6.4), however, their binding to cell-surface markedly increased, and only the binding of non-CpG-ODN instead of CpG-ODN was inhibited by Herring sperm DNA, implying such pH change enabled CpG-ODN bind to its specific binding-site. Consistently, lymphocytes appeared more sensitive to the stimulation of CpG-ODN at acidic pH, and Herring sperm DNA inhibited the CpG-ODN-induced TNF production from splenocytes at pH 7.4, but not at pH 6.4. These results suggest the existence of membrane receptor that specifically engages CpG-ODN with high affinity only at acidic pH, and support the hypothesis that the binding CpG-ODN to its specific membrane receptor and subsequently triggering of CpG-related signaling occurred within acidified endosomes.

Rapamycin-induced G1 arrest in cycling B-CLL cells is associated with reduced expression of cyclin D3, cyclin E, cyclin A, and survivin

In B-cell chronic lymphocytic leukemia (B-CLL), malignant cells seem to be arrested in the G(0)/early G(1) phase of the cell cycle, and defective apoptosis might be involved in disease progression. However, increasing evidence exists that B-CLL is more than a disease consisting of slowly accumulating resting B cells: a proliferating pool of cells has been described in lymph nodes and bone marrow and might feed the accumulating pool in the blood. Rapamycin has been reported to inhibit cell cycle progression in a variety of cell types, including human B cells, and has shown activity against a broad range of human tumor cell lines. Therefore, we investigated the ability of rapamycin to block cell cycle progression in proliferating B-CLL cells. We have recently demonstrated that stimulation with CpG-oligonucleotides and interleukin-2 provides a valuable model for studying cell cycle regulation in malignant B cells. In our present study, we demonstrated that rapamycin induced cell cycle arrest in proliferating B-CLL cells and inhibited phosphorylation of p70s6 kinase (p70(s6k)). In contrast to previous reports on nonmalignant B cells, the expression of the cell cycle inhibitor p27 was not changed in rapamycin-treated leukemic cells. Treatment with rapamycin prevented retinoblastoma protein (RB) phosphorylation in B-CLL cells without affecting the expression of cyclin D2, but cyclin D3 was no longer detectable in rapamycin-treated B-CLL cells. In addition, rapamycin treatment inhibited cyclin-dependent kinase 2 activity by preventing up-regulation of cyclin E and cyclin A. Interestingly, survivin, which is expressed in the proliferation centers of B-CLL patients in vivo, is not up-regulated in rapamycin-treated cells. Therefore, rapamycin interferes with the expression of many critical molecules for cell cycle regulation in cycling B-CLL cells. We conclude from our study that rapamycin might be an attractive substance for therapy for B-CLL patients by inducing a G(1) arrest in proliferating tumor cells.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

Plasmacytoid dendritic cells: the key to CpG

The vertebrate immune system has established TLR9 to detect microbial DNA based on unmethylated CG dinucleotides within certain sequence contexts (CpG motifs). In humans, the expression of toll-like receptor 9 (TLR9) is restricted to B cells and plasmacytoid dendritic cells (PDC). The PDC is characterized by the ability to rapidly synthesize large amounts of type I IFN (IFN-alpha and IFN-beta) in response to viral infection. In contrast to other dendritic cell subsets which express a broad profile of TLRs, the TLR profile in PDC is restricted to TLR7 and TLR9. So far, CpG DNA is the only defined microbial molecule recognized by PDC. An intriguing feature of PDC is its ability to simultaneously produce the two major Th1-inducing cytokines in humans, IFN-alpha and IL-12, both at high levels. The ratio of IFN-alpha versus IL-12 and the quantity of these cytokines are regulated by T helper cell-mediated costimulation via CD40 ligation. The ratio also depends on the differentiation stage of the PDC at the time of stimulation and the type of CpG ODN used. We propose a model in which the establishment of Th1 responses in vivo is improved by appropriately stimulated PDC that otherwise - in the absence of CpG DNA--support Th2 or Th0 responses and thus have been called DC2.

Effect of suppressive DNA on CpG-induced immune activation

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs stimulate a strong innate immune response. This stimulation can be abrogated by either removing the CpG DNA or adding inhibitory/suppressive motifs. Suppression is dominant over stimulation and is specific for CpG-induced immune responses (having no effect on LPS- or Con A-induced activation). Individual cells noncompetitively internalize both stimulatory and suppressive ODN. Studies using ODN composed of both stimulatory and suppressive motifs indicate that sequence recognition proceeds in a 5'-->3' direction, and that a 5' motif can block recognition of immediately 3' sequences. These findings contribute to our understanding of the immunomodulatory activity of DNA-based products and the rules that govern immune recognition of stimulatory and suppressive motifs.

Type 1 and type 2 responses in regulation of Ig isotype expression in cattle

Regulation of humoral immune responses is multifactorial involving appropriate activation, costimulation and the presence of specific soluble factors. Polarized type 1 or type 2 humoral responses in the laboratory mouse have been linked to expression of specific cytokines and thus can be used to provide insight into the type of response generated by infection. For example, IFN-gamma has been linked to IgG2a and IgG3 production, IL-4 to IgG1 and IgE production and TGF-beta to IgA production. Unlike the laboratory mouse, generally housed under defined conditions, highly skewed isotype expression patterns generally occur in cattle in chronic infections. A few examples of polarized responses have been noted in chronic experimental or naturally occurring infections including F. hepatica, M. paratuberculosis, C. parvum and B. abortus. In vitro studies using purified bovine B cells and various forms of costimulation and cytokines have demonstrated that isotype responses can be polarized under certain experimental conditions in vitro. That is, IgG1 expression is positively regulated by IL-4 and IgG2 expression is positively regulated by IFN-gamma. Other as yet unidentified factors may play pivotal roles in regulating humoral immune responses in large ruminant species in vivo. This possibility is best exemplified by recent studies using DNA vaccines in cattle that have been demonstrated in the mouse to be generally polarizing to a type 1 response. Surprisingly, studies in cattle using plasmid DNA as vaccination material show an almost exclusive IgG1 response. Based on a number of studies using T cell clones and various biological assays, it is clear that the classical roles of many cytokines in the laboratory mouse do not extrapolate entirely or at all to cattle. Thus, the design of adjuvants and immune modulators should be based on studies done in cattle or using bovine cells. Based on studies to date, several "holes" in the cytokine repertoire exist and these roles may be assumed by unique factors or activities of other known cytokines.

Immunostimulatory sequence oligodeoxynucleotide-based vaccination and immunomodulation: two unique but complementary strategies for the treatment of allergic diseases

Despite a number of effective pharmaceutical options for the prevention and treatment of the pathophysiologic responses that occur in sensitized patients on allergen exposure, the termination of allergic hypersensitivities remains an elusive therapeutic goal. Traditional immunotherapy with allergen extracts is the only currently used intervention that has been shown to induce allergen tolerance, but it has a limited scope of efficacy. However, recent studies suggest that immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) -based interventions might offer an alternative and potentially more effective means for extinguishing T (H)2-biased hypersensitivities. Three basic ISS-ODN -based immunotherapeutic strategies have been studied to date. Immunization with allergen mixed with ISS- ODN, immunization with allergen -ISS- ODN conjugates, and immunomodulation with ISS- ODN alone all have proved efficacy in the attenuation of the allergic phenotype in mice. Preliminary results with allergen -ISS- ODN conjugate vaccines in allergic patients have also been encouraging. This article will provide our perspective on the application of ISS-ODN -based vaccination and immunomodulation to the treatment of atopic diseases and the immunologic basis for their antiallergic activities.

'Immunomers'--novel 3'-3'-linked CpG oligodeoxyribonucleotides as potent immunomodulatory agents

Oligodeoxyribonucleotides containing CpG dinucleotides (CpG DNAs) are currently being evaluated as novel immunomodulators in clinical trials. Recently, we showed that an accessible 5' end is required for immunostimulatory activity and blocking the 5' end of CpG DNA by conjugation of certain ligands abrogates immunostimulatory activity. Based on these results, we designed and synthesized 3'-3'-linked CpG DNAs that contained two or more identical CpG DNA segments, referred to here as 'immunomers'. The use of solid support bearing diDMT-glyceryl-linker permitted convenient synthesis of immunomers with both segments synthesized simultaneously, giving better yields and purity. The in vitro and in vivo studies suggest that as a result of accessibility to two 5' ends for recognition, immunomers show an enhanced immunostimulatory activity compared with linear CpG DNAs. We also studied the suitability of a number of different linkers for attaching the two segments of immunomers. A C3-linker was found to be optimal for joining the two segments of immunomers. Incorporation of multiple linkers between the two segments of immunomers resulted in different cytokine profiles depending on the nature and number of linkers incorporated. Additionally, the length of immunomer also plays a significant role in inducing immune responses. An immunomer containing 11 nt in each segment showed the highest activity and an 11mer linear CpG DNA failed to stimulate an immune response. These results suggest that immunomers have several advantages over conventional linear CpG DNAs for immunomodulatory activity studies.

Immunopharmacology of CpG DNA

Recognition of danger of infection by innate immune cells is a prerequisite to combat infections and to activate T and B cells. Pathogen-associated molecular patterns (PAMP) play a fundamental role in this process. PAMPs are sensed by at least ten different Toll-like receptors (TLR). Within the realm of PAMPs, CpG DNA that is recognized by TLR-9 has an outstanding propensity to induce a milieu that favors activation of T lymphocytes and biases Th1-dominated immune responses. Therefore CpG DNA has become a promising immuno-therapeutical candidate to assist and to direct immune responses such as in vaccination or modulation of allergic responses. As opposed to other PAMPs, CpG DNA can be synthesized with defined purity and base composition. Moreover, chemical substitutions can confer new qualities to synthetic CpG DNA.

Potent CpG oligonucleotides containing phosphodiester linkages: in vitro and in vivo immunostimulatory properties

Bacterial and synthetic DNAs, containing CpG dinucleotides in specific sequence contexts, activate the vertebrate immune system. Unlike phosphorothioate (PS) CpG DNAs, phosphodiester (PO) CpG DNAs require either palindromic sequences and/or poly(dG) sequences at the 3(')-end for activity. Here, we report 'PO-immunomers' having two PO-CpG DNA molecules joined through their 3(')-ends. These PO-imunomers permitted us, for the first time, to assess immunostimulatory properties of PO-CpG DNAs in vitro and in vivo without the need for palindromic and/or poly(dG) sequences. In medium containing 10% fetal bovine serum, PO-immunomers were more resistant than PO-CpG DNAs to nucleases. Compared to PS-CpG DNA in BALB/c and C3H/HeJ mice spleen cell culture assays, PO-immunomers showed increased IL-12 secretion and minimal amounts of IL-6 secretion. PO-immunomers activated NF-kappa B and induced cytokine secretion in J774 cell cultures. In addition, PO-immunomers showed antitumor activity in nude mice bearing human breast (MCF-7) and prostate (DU145) cancer xenografts.

Distinct response of human B cell subpopulations in recognition of an innate immune signal, CpG DNA

Innate immunity has recently gained renewed interest in its ability to regulate adaptive immunity. Among the innate immune signals, CpG DNA has revealed its potential as a vaccine adjuvant. However, the cellular mechanism for the effect of CpG DNA on the humoral immune response is not well understood. Here, we investigated the effects of CpG DNA on human B cell differentiation using highly purified B cell subsets: naive, germinal center (GC), and memory B cells. In the in vitro culture system that mimics the primary or secondary immune response in vivo, CpG DNA markedly augmented the proliferation and generation of plasma cells from naive and memory B cells. CpG DNA dramatically increased plasma cell generation from GC B cells. However, CpG DNA did not have effect on memory B cell generation from GC B cells. These results suggest that CpG DNA potentiates the B cell adaptive immune response by enhancing terminal differentiation, but does not affect the generation of memory B cells.

CpG motifs in bacterial DNA and their immune effects

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.

Highly immunostimulatory CpG-free oligodeoxynucleotides for activation of human leukocytes

Synthetic oligodeoxynucleotides (ODNs) bearing CpG dinucleotides can mimic the immunostimulatory effects of bacterial DNA in vertebrates. Besides the known CpG motifs, no other sequence motif has been shown to have independent immunostimulatory effects. Several past investigators have demonstrated that the nucleotide content or the phosphorothioate (PS) backbone may have effects independently of the sequence. However, the effect of both nucleotide content and PS backbone to stimulate human leukocytes is not well understood. We investigated the immunostimulatory activity of 34 PS-ODNs with different nucleotide contents, lengths, and methylation status on human leukocytes. The thymidine content showed strong CpG-independent contribution to immunostimulation. In contrast, ODNs rich in other nucleotides (guanosine, cytosine, or adenosine) induced no or much lower levels of immunostimulation. The observed effects were highly dependent on the PS backbone chemistry. In addition to the base content and the backbone chemistry, the length of the PS-ODN was directly related to the magnitude of its stimulatory effects, especially on B cells. In addition, methylation of CpG dinucleotides did not always cause an abrogation of the immunostimulation. Immunostimulatory effects could be observed with methylated CpG ODNs, specifically as the ODN length was increased from 18 to 24 or more nucleotides (nt). In contrast, PS-ODNs with inverted CpG dinucleotides showed some but only weak immunostimulation. Our results demonstrate that non-CpG ODNs rich in thymidine or ODNs with methylated CpG motifs have length-dependent immunostimulatory effects. Such ODNs can induce effects similar to those seen with CpG ODNs but are much less efficient in stimulating human immune cells.

CpG-oligodinucleotides as an effective adjuvant in pigs for intramuscular immunizations

In this study, the effect of two oligodeoxynucleotide (ODN) sequences 5'GCT-AGA-CGT-TAG-CGT-3' (CpG-ODN) and 5'-GCT-AGA-GCT-TAG-GCT-3' (GpC-ODN) on the antigen-specific antibody and cellular immune response after intramuscular immunizations with OVA was analyzed in pigs. Pigs immunized with OVA supplemented with these ODNs showed a significantly enhanced primary antibody response in comparison with the control group which received OVA without ODN. This enhanced primary antibody response appeared ODN-sequence-independent as similar effects were seen in both ODN-groups. The OVA-specific antibody titers obtained after a single injection of antigen combined with either of both ODNs were as high as the titers in the control group after two injections. Furthermore, the ODN-supplemented animals showed significantly higher OVA-specific IgA antibodies in their saliva and nasal secretions at some time points after the first immunization. Proliferation assays showed that CpG- as well as GpC-ODN significantly enhanced the antigen-specific as well as the mitogen-induced proliferation in different lymphoid tissues. Furthermore, 48h after the third immunization the CpG-group showed a significantly decreased IL-6 mRNA expression in cells of the local draining lymph node but no significant difference in TGF-beta (Th3-like) and IL-10 (Th2-like). The ODN injected animals showed the tendency to have higher IFN-gamma (Th1-like) mRNA-expression in comparison with the control group. To our knowledge, these are the first in vivo studies in pigs, which demonstrate the appropriateness of CpG-ODN as immunostimulating adjuvants in vaccines for farm animals.

Phosphodiester CpG oligonucleotides as adjuvants: polyguanosine runs enhance cellular uptake and improve immunostimulative activity of phosphodiester CpG oligonucleotides in vitro and in vivo

Bacterial DNA and oligonucleotides (ODN) containing CpG-motifs strongly activate cells of the immune system. Accordingly CpG-DNA is a powerful adjuvant in vaccination protocols for B-cell as well as for cytotoxic T-cell responses. A decisive propensity of CpG-DNA is its capacity to induce preferentially T helper type 1 (Th1)-dominated immune responses. To exert its function CpG-DNA has to be taken up by responsive cells, e.g. antigen-presenting cells (APC). The rate of uptake is influenced by the DNA's backbone modification and critically determines activity of CpG-DNA. CpG ODN with a phosphothioate backbone (PTO) are currently used for most in vivo and in vitro studies, since PTO modification protects ODN from the attack of nucleases. However, after administration of PTO-modified CpG-ODN long-lasting effects including lymphadenopathy as well as sustained local interferon-gamma (IFN-gamma) and interleukin-12 (IL-12) production have been reported. To circumvent these restrictions we investigated the effects of DNA sequence as well as DNA backbone modification on cellular uptake and resulting immunostimulation. We show here that uptake of phosphodiester (PO)-CpG-ODN can be strongly enhanced by poly guanosine runs added at the 3' end of the ODN. In addition these ODN showed an improved immunostimulatory activity in vivo and in vitro. This included protection of mice against lethal Th2-dependent leishmaniasis as well as priming of antigen specific Th1 responses. More importantly, guanosine-rich PO-CpG-ODN neither induced lymphadenopathy nor prolonged cytokine production after local administration. Since these improved PO ODN are efficient in vitro and in vivo and lack long lasting undesired effects they could be used preferably as adjuvants in vaccination protocols.

Cell cycle progression of chronic lymphocytic leukemia cells is controlled by cyclin D2, cyclin D3, cyclin-dependent kinase (cdk) 4 and the cdk inhibitor p27

B-CLL cells are arrested in G0/early G1 phase of the cell cycle and are characterized by a marked hyporesponsiveness towards a variety of polyclonal B cell activators. We have previously demonstrated that costimulation with CpG-ODN and IL-2 can overcome this proliferative defect. Cyclin D3 is the principal D-type cyclin which mediates G1 progression in normal B cells, but in B-CLL cells both cyclin D2 and cyclin D3, were strongly upregulated upon stimulation. Both cyclins were associated with cdk4 but not with cdk6, which is the catalytic partner of D-type cyclins in normal B cells. Moreover, immune complexes consisting of cyclin D2 and cdk4 or cyclin D3 and cdk4 were both functional and phosphorylated the RB protein in vitro. The cell cycle inhibitor p27 plays a pivotal role in cell cycle progression of B lymphocytes and has been shown to be overexpressed in B-CLL cells. P27 was rapidly downregulated in B-CLL cells even when stimulated with a non-CpG-ODN or IL-2 alone, while only moderate regulation could be observed in normal B cells. Taken together, our findings demonstrate that regulation of early cell cycle progression differs between B-CLL cells and normal B cells. These findings do not only contribute to the understanding of B-CLL pathophysiology, but might ultimately lead to the identification of new therapeutic targets.

Amb a 1-linked CpG oligodeoxynucleotides reverse established airway hyperresponsiveness in a murine model of asthma

BACKGROUND

Recently, it has been demonstrated that immunostimulatory DNA sequences (ISS) containing CpG motifs prevent the development of allergic airway responses in murine models of disease. However, few studies have addressed the issue of whether these agents will reverse established Tm(H)2-driven allergic airway responses.

OBJECTIVE

The aim of this study was to determine whether intradermal delivery of an immunogenic protein of ragweed pollen linked to an immunostimulatory DNA sequence could reverse an established allergic response in the mouse lung.

METHODS

Mice sensitized and challenged with ragweed pollen extract were treated intradermally twice at 1-week intervals with an ISS chemically linked to Amb a 1 (Amb a 1-ISS). One week after the Amb a 1-ISS treatment, mice were rechallenged intratracheally with ragweed extract, and airway responses were assessed.

RESULTS

Amb a 1-ISS treatment of ragweed-sensitized and ragweed-challenged mice significantly reversed allergen-induced airway hyperresponsiveness and suppressed the total number of eosinophils in bronchoalveolar lavage fluid. The inhibitory effect of Amb a 1-ISS was associated with a marked increase in IFN-gamma levels by Amb a 1-stimulated splenocytes and a shift in the antibody profile from a T(H)2-directed IgG1 response to a T(H)1-directed IgG2a response. Interestingly, the inhibitory effect of Amb a 1-ISS on allergen-driven airway hyperresponsiveness was independent of suppression of T(H)2 cytokine production.

CONCLUSION

These results demonstrate that intradermal delivery of allergen-specific DNA conjugates can reverse established allergic responses in the murine lung, supporting their potential use in the treatment of human asthma.

Sensitization of B-cell chronic lymphocytic leukemia cells to recombinant immunotoxin by immunostimulatory phosphorothioate oligodeoxynucleotides

A recombinant anti-CD25 immunotoxin, LMB-2, has shown clinical efficacy in hairy cell leukemia and T-cell neoplasms. Its activity in B-cell chronic lymphocytic leukemia (B-CLL) is inferior but might be improved if B-CLL cells expressed higher numbers of CD25 binding sites. It was recently reported that DSP30, a phosphorothioate CpG-oligodeoxynucleotide (CpG-ODN) induces immunogenicity of B-CLL cells by up-regulation of CD25 and other antigens. The present study investigated the antitumor activity of LMB-2 in the presence of DSP30. To this end, B-CLL cells from peripheral blood of patients were isolated immunomagnetically to more than 98% purity. Incubation with DSP30 for 48 hours augmented CD25 expression in 14 of 15 B-CLL samples, as assessed by flow cytometry. DSP30 increased LMB-2 cytotoxicity dose dependently whereas a control ODN with no CpG motif did not. LMB-2 displayed no antitumor cell activity in the absence of CpG-ODN as determined colorimetrically with an (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. In contrast, B-CLL growth was inhibited in 12 of 13 samples with 50% inhibition concentrations (IC50) in the range of LMB-2 plasma levels achieved in clinical studies. Two samples were not evaluable because of spontaneous B-CLL cell death in the presence of DSP30. Control experiments with an immunotoxin that does not recognize hematopoietic cells, and an anti-CD22 immunotoxin, confirmed that sensitization to LMB-2 was specifically due to up-regulation of CD25. LMB-2 was much less toxic to normal B and T lymphocytes compared with B-CLL cells. In summary, immunostimulatory CpG-ODNs efficiently sensitize B-CLL cells to a recombinant immunotoxin by modulation of its target. This new treatment strategy deserves further attention.

Monocytes are required for optimum in vitro stimulation of bovine peripheral blood mononuclear cells by non-methylated CpG motifs

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs within certain flanking base pairs are recognized as a danger signal by the innate immune system of vertebrates. Using lymphocyte proliferative response (LPR) and IFN-gamma secretion assays, a panel of 38 ODN was screened for immunostimulatory activity on bovine peripheral blood mononuclear cells. ODN composed of a nuclease resistant phosphorothioate backbone and a leading 5'-TCGTCGTT-3' motif with two 5'-GTCGTT-3' motifs were highly stimulatory in both assays. Flow cytometric analysis and cell-specific surface marker labeling determined that B-cells (surface IgM(+)) were the primary cell population responding in the LPR assay. Depletion of T cells (CD3(+)) from the PBMC population did not affect IFN-gamma secretion or B-cell proliferation when cultured with CpG-ODN. However, depletion of monocytes (DH59B(+)) completely abrogated the ability of CpG-ODN to stimulate IFN-gamma secretion, and significantly reduced the B-cell proliferative response. These data establish the identity of an optimal immunostimulatory CpG motif for cattle and demonstrate that monocytes play a pivotal role in the ability of cell populations to respond to CpG-ODN. These data provide insight for future studies investigating the mechanism of CpG-ODN bioactivity and its application in novel vaccine formulations and immunotherapy.

Characterization of the cysteine-rich secretory protein 3 gene as an early-transcribed gene with a putative role in the pathophysiology of Sjögren's syndrome

OBJECTIVE

To identify genes that may participate in the pathophysiology of Sjögren's syndrome (SS), the technique of differential display was applied to labial minor salivary gland (MSG) biopsy samples.

METHODS

Total RNA was isolated from MSG biopsy samples from a woman with primary SS and a control subject, and the differential display protocol with 8 different random oligonucleotide primers was performed. One particular differentially expressed fragment showed 98% homology with the cysteine-rich secretory protein 3 (CRISP-3) gene. The result was verified by reverse transcription-polymerase chain reaction (RT-PCR) with messenger RNA (mRNA) samples from MSG biopsy tissues obtained from 4 women with primary SS. A CRISP-3 RNA probe was synthesized for in situ hybridization of 7 MSG biopsy samples from patients with primary SS. In an attempt to interpret the expression of CRISP-3, normal peripheral blood lymphocytes (PBLs) were activated in vitro at different time points and assayed for CRISP-3 expression. Finally, B cells were transfected with the coding region of CRISP-3 and monitored for the up-regulation of different B cell activation markers.

RESULTS

The CRISP-3 gene was detected by RT-PCR in all SS patients tested. Mainly the mononuclear cells infiltrating the MSGs of patients expressed CRISP-3 mRNA. In addition, CRISP-3 was detected by RT-PCR between 30 minutes and 6 hours in phorbol myristate acetate-activated normal PBLs, while staurosporine inhibited this expression. CRISP-3-transfected B cells exhibited an up-regulation in CD25 surface expression.

CONCLUSION

The CRISP-3 gene is identified as a novel early response gene that may participate in the pathophysiology of the autoimmune lesions of SS.

The role of surface ig binding in the activation of human B cells by phosphorothioate oligodeoxynucleotides

Phosphorothioate oligodeoxynucleotides (sODNs) can induce T-cell-independent polyclonal activation of human B cells by a mechanism that depends on both sequence and back-bone structure. Because matrix-bound as well as soluble sODNs are mitogenic, this stimulation may result from the engagement of surface receptor(s). In order to investigate whether surface immunoglobin (Ig) could be a receptor for sODNs, the interaction of sODNs-fluorescein isothiocyanate (FITC) with Ig-coated beads was examined. sODNs specifically bound to human IgM and IgG. Moreover, binding of sODN to human B cells induced temperature-dependent capping of bound receptors and colocalization of FITC-sODN and IgM into aggregated caps on the surface of human B cells. A role of surface Ig was furthermore shown by observations that antibody-mediated capping of B-cell surface IgM or IgD inhibited subsequent binding of sODNs and that the capacity of sODN to stimulate human B cells was blocked by excess IgM or IgG, by nonstimulatory antibodies to sIgM, as well as by a variety of negatively charged molecules. Together, these results indicate that sODNs engage surface Ig by charge-charge interactions that lead to activation of human B cells.

Molecular approaches to elucidating innate and acquired immune responses to Babesia bovis, a protozoan parasite that causes persistent infection

For many vector-transmitted protozoal parasites, immunological control of acute infection leads to a state of persistent infection during which parasitemias may cycle unnoticed in infected but otherwise clinically healthy animals. Achieving persistent infection is a strategy that favors parasitism, since both host and, therefore, parasite survive, and endemically infected animal populations provide a reservoir of parasites continually available for subsequent transmission. Examples of the major economically important protozoan pathogens that cause persistent infection in mammals include the related Theileria and Babesia parasites as well as Trypanosoma species. Control of acute infection and maintenance of clinical immunity against subsequent infection are determined by the interplay of innate and acquired immune responses. This review will focus on approaches taken to gain an understanding of the molecular basis for innate and acquired immunity against the hemoprotozoan parasite of cattle, Babesia bovis. Knowledge of mechanisms used by the parasite to survive within infected cattle from acute to persistent infection combined with definition of the correlates of protective immunity in cattle should be applicable to designing effective vaccines.

Divergent therapeutic and immunologic effects of oligodeoxynucleotides with distinct CpG motifs

Immune stimulatory oligodeoxynucleotides (ODN) with unmethylated CpG motifs are potent inducers of both innate and adaptive immunity. It initially appeared that a single type of optimal CpG motif would work in all applications. We now report that specific motifs of CpG ODN can vary dramatically in their ability to induce individual immune effects and that these differences impact on their antitumor activity in different tumor models. In particular, a distinct type of CpG motif, which has a chimeric backbone in combination with poly(G) tails, is a potent inducer of NK lytic activity but has little effect on cytokine secretion or B cell proliferation. One such NK-optimized CpG ODN (1585) can induce regression of established melanomas in mice. Surprisingly, no such therapeutic effects were seen with CpG ODN optimized for activation of B cells and Th1-like cytokine expression (ODN 1826). The therapeutic effects of CpG 1585 in melanoma required the presence of NK but not T or B cells and were not associated with the induction of a tumor-specific memory response. In contrast, CpG 1826, but not CpG 1585, was effective at inducing regression of the EL4 murine lymphoma; this rejection was associated with the induction of a memory response and although NK cells were necessary, they were not sufficient. These results demonstrate that selection of optimal CpG ODN for cancer immunotherapy depends upon a careful analysis of the cellular specificities of various CpG motifs and an understanding of the cellular mechanisms responsible for the antitumor activity in a particular tumor.

Induction of interleukin-6 and interleukin-12 in bovine B lymphocytes, monocytes, and macrophages by a CpG oligodeoxynucleotide (ODN 2059) containing the GTCGTT motif

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) that contain unmethylated CpG dinucleotides flanked by certain bases (CpG ODN) have been shown to activate murine and human B cells and to induce proinflammatory cytokines by monocytes/macrophages and dendritic cells (DC). However, the CpG ODN sequences optimal for mice and humans are different. In the current study, the effects of CpG ODN, which were defined to stimulate strong responses in either mouse or human leukocytes, were compared for stimulation of bovine B lymphocyte proliferation and macrophage cytokine mRNA expression. The optimal CpG ODN was then tested for induction of cytokines in peripheral blood mononuclear cells (PBMC) and purified B lymphocytes, monocytes, and macrophages. At a high ODN concentration (40 microM), all but two CpG ODN tested stimulated B cell proliferation, which was dependent on unmethylated CpG motifs. CpG ODN 2059 containing the GTCGTT motif shown to activate human leukocytes also promoted the highest level of bovine B cell proliferation at a lower concentration (10 microM) when compared with CpG ODN containing AACGTT or GACGTT motifs active for murine leukocytes. Furthermore, ODN 2059 induced interleukin-6 (IL-6) production by B lymphocytes and IL-6 and IL-12 production by PBMC, monocytes, and macrophages. In contrast, IL-1beta and tumor necrosis factor-alpha (TNF-alpha) production was either very low or undetectable. Consistent with increased IL-12 production, ODN 2059 also stimulated interferon-gamma (IFN-gamma) production by PBMC. Importantly, the levels of cytokines induced by ODN 2059 were comparable to those generated in response to Escherichia coli DNA. The weak TNF-alpha response combined with the vigorous IL-6 and IL-12 response to ODN 2059 indicate the potential use of this CpG ODN as an adjuvant to enhance both antibody-mediated and IFN-gamma-mediated macrophage activation, which are important for protection against disease caused by intracellular pathogens of cattle.

Cutting edge: Role of Toll-like receptor 9 in CpG DNA-induced activation of human cells

Unmethylated CpG motifs present in bacterial DNA stimulate a rapid and robust innate immune response. Human cell lines and PBMC that recognize CpG DNA express membrane-bound human Toll-like receptor 9 (hTLR9). Cells that are not responsive to CpG DNA become responsive when transfected with hTLR9. Expression of hTLR9 dramatically increases uptake of CpG (but not control) DNA into endocytic vesicles. Upon cell stimulation, hTLR9 and CpG DNA are found in the same endocytic vesicles. Cells expressing hTLR9 are stimulated by CpG motifs that are active in primates but not rodents, suggesting that evolutionary divergence between TLR9 molecules underlies species-specific differences in the recognition of bacterial DNA. These findings indicate that hTLR9 plays a critical role in the CpG DNA-mediated activation of human cells.

A novel function of phosphorothioate oligodeoxynucleotides as chemoattractants for primary macrophages

Phosphorothioate cytosine-guanine oligodeoxynucleotides (CpG PS-ODNs) has been reported to induce Th1 immune responses against coadministered Ags more efficiently than phosphodiester CpG ODNs (CpG PO-ODNs). Here, we demonstrated that PS-ODNs, but not PO-ODNs, have a chemotactic effect on primary macrophages, which is independent of the CpG motif. In addition, the conjugation of a hexameric dG run (dG(6) run) at the 3' terminus reduced the concentration required for the optimal chemotactic activity of PS-ODNs by approximately 10-fold. Endosomal maturation blockers, such as monensin and chloroquine, inhibited the chemotactic effect of PS-ODNs. The inhibition of the activities of p38 mitogen-activated protein (MAP) kinase, and extracellular signal-related kinases (ERKs) as well as phosphoinositide 3-kinase with their specific inhibitors also resulted in suppressing the chemotaxis of primary macrophages induced by PS-ODNs. These results indicate that the PS-ODN-mediated chemotaxis requires the activation of ERKs, p38 MAP kinase, and phosphoinositide 3-kinase as well as endosomal maturation. In addition, the phosphorylations of the p38 MAP kinase, ERKs, and protein kinase B, Akt, were induced by PS-ODN, which were further enhanced by the presence of both a dG(6) run and CpG motifs. Our findings suggest that the chemotactic activity of PS-ODNs may be one of the mechanisms by which PS-ODNs exhibit stronger immunomodulatory activities than PO-ODNs in vivo.

Immunostimulatory DNA inhibits IL-4-dependent IgE synthesis by human B cells

BACKGROUND

Immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) is a potent antiallergic immunomodulating agent in mice. However, few studies have addressed its antiallergic potential in human subjects.

OBJECTIVE

We sought to determine whether a phosphoro-thioate ISS-ODN could inhibit IL-4-dependent IgE synthesis by human B cells.

METHODS

Initially, nonatopic- and atopic-donor PBMCs were incubated with ISS-ODN or mutated oligodeoxynucleotide, and cytokine production and B-cell expression of IFN-gamma receptor and IL-4 receptor were measured by using ELISA and flow cytometry, respectively. In subsequent studies atopic-donor PBMCs were incubated with IL-4 alone or with ISS-ODN or mutated oligodeoxynucleotide. After 14 days, IgE production and IgM, IgG, and IgA production were determined by using ELISA. In select IgE studies cytokines were neutralized with mAbs.

RESULTS

ISS-ODN induced IL-12, IFN-alpha, IFN-gamma, IL-10, and IL-6 production from both nonatopic- and atopic-donor PBMCs. ISS-ODN also increased IFN-gamma receptor and inhibited IL-4 receptor expression on B cells from both donor populations. Furthermore, ISS-ODN inhibited IL-4-dependent IgE production by atopic-donor PBMCs. Neutralization of IL-12, IFN-alpha, IFN-gamma, and IL-10, but not IL-6, attenuated the inhibitory activity of ISS-ODN on IgE production. In contrast to its inhibition of IgE synthesis, ISS-ODN stimulated the production of IgM, IgG, and IgA.

CONCLUSION

These in vitro studies demonstrate that phos-phorothioate ISS-ODN elicits an innate immune response by PBMCs, which inhibits IL-4-dependent IgE synthesis. In addition, these results provide further support for consideration of ISS-ODN therapy for the treatment of allergic disease in clinical practice.

Role of the heat shock protein 90 in immune response stimulation by bacterial DNA and synthetic oligonucleotides

To elucidate the mechanisms of immunostimulation by bacterial DNA and synthetic oligonucleotides, the effects of heat shock protein 90 (Hsp90) inhibitors on the activation of murine spleen cells and macrophages by these molecules were investigated. Murine spleen cells and J774 and RAW264.7 macrophages responded to a CpG-containing oligodeoxynucleotide (CpG ODN) and Escherichia coli DNA by increased production of interleukin 6 (IL-6), IL-12, tumor necrosis factor alpha, and nitric oxide (NO). Pretreatment with any of the three Hsp90 inhibitors geldanamycin, radicicol, and herbimycin A resulted in a dose-dependent suppression of cytokine production from the spleen cells and macrophages and of NO from macrophages stimulated with CpG ODN or E. coli DNA. These Hsp90 inhibitors, however, had no effect on Staphylococcus aureus Cowan strain 1-induced IL-12 production from either the murine spleen cells or macrophages. CpG ODN and E. coli DNA induced increased intracellular levels of phosphorylated extracellular signal-regulated kinases (ERK1 and -2), which are members of the mitogen-activated protein (MAP) kinase family, while geldanamycin and radicicol blocked the phosphorylation of ERK1 and -2 in J774 and RAW264.7 cells. These data indicate that DNA-induced activation of murine spleen cells and macrophages is mediated by Hsp90 and that Hsp90 inhibitor suppression of DNA-induced macrophage activation is associated with disruption of the MAP kinase signaling pathway. Our findings suggest that Hsp90 inhibitors may provide a useful means of elucidating the mechanisms of immunostimulation by bacterial DNA and CpG ODN as well as a strategy for preventing adverse effects of bacterial DNA as well as lipopolysaccharide.

Immunostimulatory sequence DNA linked to the Amb a 1 allergen promotes T(H)1 cytokine expression while downregulating T(H)2 cytokine expression in PBMCs from human patients with ragweed allergy

BACKGROUND

Recent studies have demonstrated that bacterially derived immunostimulatory sequences (ISSs) of DNA can activate the mammalian innate immune system and promote the development of T(H)1 cells. Promotion of T(H)1 immunity by means of immunotherapy in allergic patients has led to the alleviation of symptoms that result from allergen-specific T(H)2 responses.

OBJECTIVE

Our purpose was to investigate whether the T(H)1-enhancing properties of ISSs could be used to alter the T(H)2-dominated immune response of allergic PBMCs in vitro.

METHODS

Ragweed protein-linked ISS (PLI) was generated from a specific, highly active 22-base ISS and Amb a 1, the immunodominant allergen in ragweed pollen, to combine the T(H)1-enhancing properties of ISSs with allergen selectivity, and its activity was investigated in PBMC cultures from subjects with ragweed allergy.

RESULTS

PLI was markedly successful at reversing the dominant allergen-induced T(H)2 profile while greatly enhancing IFN-gamma production. Delivering ISSs in a linked form proved to be much more effective at modulating the resulting cytokine profile than delivering free ISSs in a mixture with unlinked Amb a 1. PLI also demonstrated cytokine-modulating properties, even when used to stimulate cells that had already been primed for 6 days with Amb a 1. The antigen specificity of the action of PLI was confirmed by the observations that PLI enhances Amb a 1--specific T-cell proliferation.

CONCLUSION

These data indicate that delivery of ISSs within an antigen-specific context exhibits potent cytokine-modulating activity and, combined with its reduced allergenicity, makes this molecule a strong candidate for use in improved immunotherapy applications.

Effect of immunostimulatory CpG-oligonucleotides in chronic lymphocytic leukemia B cells

Bacterial DNA and phosphothioate oligonucleotides containing a CpG motif (CpG-ODN) can activate cells of the immune system such as monocytes, dendritic cells and B cells. Protective immune responses against pathogens and tumor cells were observed in murine models when mice were treated with CpG-ODN. Recent results have demonstrated strong activation of human immune cells as well. Apart from stimulating cells of the immune system, CpG ODN have many direct effects on B-CLL cells such as upregulation of costimulatory molecules, cell cycle entry and upregulation of potential target antigens for antibody therapy. Therefore, CpG-ODN appear to be attractive compounds to be included into new therapeutic strategies like tumor cell vaccination and adoptive T cell transfer or therapy with monoclonal antibodies. In this review, the effects of CpG-ODN on B-CLL cells are summarized and potential therapeutic applications of CpG-ODN in chronic lymphocytic leukemia are discussed.

CpG-DNA derived from sera in systemic lupus erythematosus enhances ICAM-1 expression on endothelial cells

OBJECTIVE

To examine the effect of transfection of oligodeoxynucleotides (ODNs) containing a CpG motif (CpG-ODN), of which the sequence was derived from circulating DNA in the sera of patients with systemic lupus erythematosus (SLE), on the expression of intercellular adhesion molecule-1 (ICAM-1) and synthesis of mRNA for proinflammatory cytokines and ICAM-1 in human umbilical vein endothelial cells (EC).

METHODS

A CpG-ODN or a control analogue, GpC-ODN, was transfected into EC. ICAM-1 expression was examined by flow cytometry, and expression of mRNA in EC encoding interleukin 1 (IL1), IL6, IL8, tumour necrosis factor alpha (TNFalpha), interferon gamma (IFNgamma), and ICAM-1 was examined by semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

The CpG-ODN augmented the expression of ICAM-1 on EC determined by flow cytometry and increased mRNA levels of IL6, IL8, TNFalpha, IFNgamma, and ICAM-1, but the GpC-ODN did not.

CONCLUSION

Synthesised DNA, with a sequence corresponding to that of the fragment containing the CpG motif, in sera of patients with SLE was found to enhance ICAM-1 expression on EC, suggesting the participation of circulating DNA fragments in the pathogenesis of vasculitis in SLE.

From bugs to drugs: therapeutic immunomodulation with oligodeoxynucleotides containing CpG sequences from bacterial DNA

Several types of immune cells possess pattern recognition receptors (PRR) that can distinguish prokaryotic DNA from vertebrate DNA by detecting unmethylated CpG dinucleotides in particular base contexts (CpG motifs). Bacterial DNA or synthetic oligodeoxynucleotides containing these CpG motifs activate both innate and acquired immune responses that have evolved to protect against intracellular infections. These T helper 1 (Th1)-like immune responses include activation of B cells, dendritic cells, macrophages, and natural killer (NK) cells. CpG DNA-induced immune activation can protect against infection either alone or in combination with a vaccine and is effective in the immunotherapy of allergic diseases and cancer. Human clinical trials using such CpG DNA are currently underway.

The bare skin and the nose as non-invasive routes for administering peptide vaccines

Among the different technologies currently tested for the development of novel vaccines, synthetic peptides represent a promising option, since they are chemically pure and induce immune responses of predetermined specificity. Furthermore, they can be replaced with pseudopeptides or peptide mimetics that contain changes in the amide bond, resulting in more stable and immunogenic molecules. Administration of peptide vaccines via non-invasive routes, such as the nose or the bare skin, allows the efficient uptake of antigen by antigen-presenting cells, which are abundant in the associated lymphoid tissues, ensuring the induction of effective systemic and mucosal immune responses. Using non-invasive routes could be advantageous for vaccination programs in third-world countries, since vaccine administration is simple, painless and economical. In this review, we discuss and present some preliminary data on the advantages of synthetic peptides and peptidomimetics as candidate vaccines, and their potential for administration via the skin and the nose.

Oligodeoxynucleotides containing CpG motifs induce low levels of TNF-alpha in human B lymphocytes: possible adjuvants for Th1 responses

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) represent potential adjuvants for specific immunotherapy of type I allergies because they foster Th1-like immune responses. However, previous work has shown that CpG-ODN induce systemically active levels of TNF-alpha in murine macrophages. The goal of the present study was to evaluate the release of TNF-alpha in human cells by a CpG-ODN proven to induce Th1 immune responses in cells from atopic individuals and in mice. CpG-ODN induced TNF-alpha in cells from atopic and healthy individuals. However, the amounts were low, as determined by comparison with commonly used Ags. Intracellular cytokine staining of PBMC revealed that CpG-ODN-induced TNF-alpha derived exclusively from B lymphocytes. TNF-alpha contributed to the CpG-ODN-augmented proliferation and Ig synthesis in PBMC, but was not involved in IFN-gamma synthesis. In conclusion, our findings indicate that certain CpG-ODN induce low amounts of TNF-alpha in human B lymphocytes and may therefore be used to modulate Th2-biased immune responses in allergic patients.

Response of porcine peripheral blood mononuclear cells to CpG-containing oligodeoxynucleotides

Exposure to bacterial DNA generates a "danger signal" that stimulates cellular elements of the mammalian immune system to proliferate and/or secrete cytokines. Stimulation is critically dependent on hexameric motifs that contain an unmethylated CpG dinucleotide: these are commonly found in bacterial but not vertebrate DNA. Different motifs are optimally stimulatory in different species. This work examines whether oligodeoxynucleotides (ODNs) containing CpG motifs stimulate peripheral blood mononuclear cells from pigs. Results show that pigs respond to CpG ODN by proliferating and secreting IL-6, IL-12 and TNF-alpha. By screening a large panel (>100) of ODNs, the palindromic hexamer 'ATCGAT' was identified as being optimally active in all animals examined (N=10). These findings are the first to establish the immunostimulatory activity of CpG ODN in pigs, and suggest that the therapeutic uses envisioned for these ODNs (as vaccine adjuvants and immunoprotective agents) may be applicable to husbandry animals.

Human peripheral blood cells differentially recognize and respond to two distinct CPG motifs

Oligodeoxynucleotides (ODN) that contain unmethylated CpG dinucleotides trigger a strong innate immune response in vertebrates. CpG ODN show promise as vaccine adjuvants, anti-allergens, and immunoprotective agents in animal models. Their transition to clinical use requires the identification of motifs that are optimally stimulatory in humans. Analysis of hundreds of novel ODN resulted in the identification and characterization of two structurally distinct "clusters" of immunostimulatory CpG ODN. One cluster ("D") preferentially stimulates IFN-gamma production by NK cells, whereas the other ("K") stimulates cell proliferation and the production of IL-6 and IgM by monocytes and B cells. The distinct immunostimulatory properties of K and D ODN can improve the design of CpG-based products to achieve specific therapeutic goals.

Non-specific antiviral activity of antisense molecules targeted to the E1 region of human papillomavirus

Antisense phosphorothioate oligonucleotides (ODN1 0x5 OMe) directed against the E1 start region of human papillomavirus 11 (HPV11) can inhibit papillomavirus induced growth of implanted human foreskin in a mouse xenograft model. Administration of a mismatch control oligonucleotide (ODN9 0x5 OMe), in which guanine was replaced with adenine in the same model, had no effect on papilloma induced growth. However, the apparent antiviral activity of ODN1 0x5 OMe was also shown in a lethal mouse cytomegalovirus (CMV) model, in which the oligonucleotides are not expected to have antisense activity. To understand the mechanisms of action of these oligonucleotides, a mismatch oligonucleotide (ODN61 0x5 OMe) was prepared which retained the CpG motifs of ODN1 0x5 OMe. This was tested in the mouse xenograft model and shown to have moderate inhibitory activity. As a definitive experiment, a comparison was made between the efficacy of the active oligonucleotide ODN1 0x5 OMe against two papilloma viruses HPV11 and HPV40. Both these viruses cause benign genital warts, but differ by four bases in their E1 sequence that was the target for ODN1 0x5 OMe. Papillomavirus induced growth in the mouse xenograft model was inhibited by ODN1 0x5 OMe in both cases, suggesting that oligonucleotide molecules have a non-specific antiviral activity that is not directly related to their antisense sequence.

Phosphorothioate backbone modification modulates macrophage activation by CpG DNA

Macrophages respond to unmethylated CpG motifs present in nonmammalian DNA. Stabilized phosphorothioate-modified oligodeoxynucleotides (PS-ODN) containing CpG motifs form the basis of immunotherapeutic agents. In this study, we show that PS-ODN do not perfectly mimic native DNA in activation of macrophages. CpG-containing PS-ODN were active at 10- to 100-fold lower concentrations than corresponding phosphodiester ODN in maintenance of cell viability in the absence of CSF-1, in induction of NO production, and in activation of the IL-12 promoter. These enhancing effects are attributable to both increased stability and rate of uptake of the PS-ODN. By contrast, PS-ODN were almost inactive in down-modulation of the CSF-1R from primary macrophages and activation of the HIV-1 LTR. Delayed or poor activation of signaling components may contribute to this, as PS-ODN were slower and less effective at inducing phosphorylation of the extracellular signal-related kinases 1 and 2. In addition, at high concentrations, non-CpG PS-ODN specifically inhibited responses to CpG DNA, whereas nonstimulatory phosphodiester ODN had no such effect. Although nonstimulatory PS-ODN caused some inhibition of ODN uptake, this did not adequately explain the levels of inhibition of activity. The results demonstrate that the phosphorothioate backbone has both enhancing and inhibitory effects on macrophage responses to CpG DNA.