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

Synthesis and hybridizing properties of P-stereodefined chimeric [PS]-{DNA:RNA} and [PS]-{DNA:(2'-OMe)-RNA} oligomers

Oxathiaphospholane derivatives of 2'-OMe-ribonucleosides and 2'-O-TBDMS-ribonucleosides (MN-OTP and TN-OTP, respectively; nucleobase protected) were synthesized and separated into pure P-diastereomers. X-ray analysis showed the R P absolute configuration of the phosphorus atom in the fast-eluting diastereomer of TA-OTP. The fast- and slow-eluting P-diastereomers of MN-OTP and TN-OTP were used in the solid-phase synthesis of phosphorothioate dinucleotides (MNPST and NPST, respectively), which were subsequently hydrolyzed with R P-selective phosphodiesterase svPDE and S P-selective nuclease P1 to determine the absolute configuration of the phosphorus atoms. P-Stereodefined phosphorothioate ([PS]) 10-mer chimeric oligomers [PS]-{DNA:(2'-OMe)-RNA} and isosequential [PS]-{DNA:RNA} containing two MNPS or NPS units were synthesized. Melting experiments performed for their complexes with Watson-Crick paired DNA matrix showed that MNPS or NPS units decrease the thermal stability of the duplexes (ΔT m = -0.5 ÷ -5.5 °C per modification) regardless of the absolute configuration of the P-atoms. When the (2'-OMe)-RNA matrix was used an increase in T m was noted in all cases (ΔT m = +1 ÷ +7 °C per modification). The changes in thermal stability of the duplexes formed by [PS]-chimeras with DNA and (2'-OMe)-RNA matrices do not correlate with the absolute configuration of the phosphorus atoms.

A Comprehensive Review on Novel Liposomal Methodologies, Commercial Formulations, Clinical Trials and Patents

Liposomes are well-recognized and essential nano-sized drug delivery systems. Liposomes are phospholipid vesicles comprised of cell membrane components and have been employed as artificial cell models to mimic structure and functions of cells and are of immense use in various biological analyses. Liposomes acquire great advantages and provide wide range of applications as useful drug carriers in pre-clinical and clinical trials. This review summarizes exclusively on scalable techniques for liposome preparation and focuses on the strengths and limitations with respect to industrial applicability. Also, this review discusses the updated recent advancements in biomedical applications with a mention of key highlights of commercially available formulations, clinical trials and patents in recent past. Furthermore, this review also provides brief information of the classification, composition and characterization of liposomes.

Mechanisms of TLR9 activation

Non-methylated CpG-motifs in bacterial or viral DNA are recognized by TLR9 as foreign. The activation of TLR9 by microbial DNA or synthetic oligonucleotides based on these motifs leads to the induction of innate immune responses. We have compared the subcellular localization of fluorescent versions of TLR9 and TLR4 and found that TLR9 is expressed in the endoplasmic reticulum while TLR4 is expressed on the plasma membrane. Fluorescently tagged bacterial DNA or CpG-DNA was observed to traffic to a tubular lysosomal compartment in human pDCs. In stimulated cells, TLR9 translocated to CpG-DNA or microbial DNA containing structures in the endosome, where TLR9 binds to DNA and initiates signaling.

Thermal stability and conformation of antiparallel duplexes formed by P-stereodefined phosphorothioate DNA/LNA chimeric oligomers with DNA and RNA matrices

3'-O-(2-Thio-4,4-pentamethylene-1,3,2-oxathiaphospholane) derivatives of LNA-type nucleosides (LNA-OTPs, 2a-d; B' = Thy, Ade(Bz), Cyt(Bz), Gua(dmf), respectively) were synthesized and separated into pure P-diastereomers. X-ray analysis allowed for assignment of the absolute configuration of the phosphorus atom in the detritylated, fast-eluting diastereomer 2a. The diastereomerically pure LNA-OTP monomers were used in solid phase synthesis of P-stereodefined chimeric PS-(DNA/LNA) 11-mers containing 2-3 LNA units. Formally, among the phosphorothioate oligomers the biggest enhancement in thermal stability of Watson-Crick paired duplexes was found for [SP-PS]-(DNA/LNA)/RNA duplexes (on average 8.2 °C per LNA nucleotide), followed by [RP-PS]-(DNA/LNA)/RNA (6.3 °C), [RP-PS]-(DNA/LNA)/DNA (3.8 °C) and [SP-PS]-(DNA/LNA)/DNA (2.4 °C per LNA nucleotide). However, detailed analysis of the thermal dissociation data showed that the thermal stability of (PS-LNA)-containing duplexes does not depend on the spatial orientation of the sulfur atoms. This conclusion received support from CD measurements.

In vitro and in vivo evaluations of human papillomavirus type 16 (HPV16)-derived peptide-loaded dendritic cells (DCs) with a CpG oligodeoxynucleotide (CpG-ODN) adjuvant as tumor vaccines for immunotherapy of cervical cancer

PURPOSE

To evaluate the immunotherapeutic potentials for human dendritic cells (DCs) loaded with different HPV16-associated antigens, including HPV16E7 (E) protein, HPV16E7 polypeptide (P), as well as CpG-oligodeoxynucleotide (ODN) 2006 as a promising immune adjuvant for vaccination against cervical carcinoma.

METHODS

DCs derived from human peripheral blood and cord blood were isolated and loaded with HPV-derived protein or peptides, in combination with CpG-ODN2006 as a potential adjuvant. The IL-12 level, the allogeneic T cell-stimulatory capacity and the cytotoxicity of cytotoxic T lymphocytes (CTLs) were evaluated in vitro. Furthermore, an immune reconstitution model of human cervical carcinoma in SCID mice was used to assess the anti-tumor effects in vivo. The tumor sizes, the expression of IgG and IFN-γ, and the presence of the human CD3(+), CD4(+) and CD8(+) T cells were measured in the mice inoculated with different DCs.

RESULTS

The antigen-loaded DCs displayed obvious anti-tumor activities in vitro and in vivo, and showed no toxicity to normal cells. The level of IL-12, an important cytokine for immune response, was up-regulated in all mice inoculated with antigen-loaded DCs. Stimulation and activity of CTLs were increased after treatment with antigen-loaded DCs. Significantly, DCs loaded with HPV16E7 polypeptide (P) showed the most distinguished immunotherapeutic activities, and such effect was further enhanced when HPV16E7 polypeptide (P) was used in combination with CpG-ODN2006. Interestingly, the same results were obtained in vivo: the tumor size was decreased, and IgG and IFN-γ levels were increased after the SCID mice were inoculated with the loaded DCs.

CONCLUSIONS

HPV16E7 polypeptide combined with the immune adjuvant CpG-ODN2006 could be a suitable HPV16-associated tumor antigen. The research provides a new strategy for generating DCs vaccines for immunotherapy of cervical cancer.

CpG plus radiotherapy: a review of preclinical works leading to clinical trial

Studies performed three decades ago in our laboratory supported the hypothesis that radiation efficacy may be augmented by bacterial extracts that stimulate non-specific systemic antitumor immune responses. Application to the clinic was halted by unacceptable side effects and toxicities resulting from exposure to whole bacterial pathogens. Later scientific advances demonstrated that DNA isolated from bacteria was immunostimulatory and could be reproduced with synthetic oligodeoxynucleotides (ODNs), thus fueling the transition from bugs to drugs. Unmethylated CpG motifs within bacterial DNA induce activation of Toll-like receptor 9 and subsequently activate antigen-specific cellular immune responses. CpG ODNs have demonstrated favorable toxicity profiles in phase I clinical trials. We showed that this potent immunoadjuvant can be used in combination with radiation therapy to enhance local and systemic responses of several murine tumors. Studies demonstrated that enhanced tumor response is mediated in part by the host immune system. Antitumor efficacy was diminished in immunocompromised mice. Animals cured by combination of radiation and CpG ODN were resistant to subsequent tumor rechallenge. This body of work contributes to our understanding of the dynamic interplay between tumor irradiation and the host immune system and may facilitate translation to clinical trials.

Chimeric DNA Vaccines against ErbB2+ Carcinomas: From Mice to Humans

DNA vaccination exploits a relatively simple and flexible technique to generate an immune response against microbial and tumor-associated antigens (TAAs). Its effectiveness is enhanced by the application of an electrical shock in the area of plasmid injection (electroporation). In our studies we exploited a sophisticated electroporation device approved for clinical use (Cliniporator, IGEA, Carpi, Italy). As the target antigen is an additional factor that dramatically modulates the efficacy of a vaccine, we selected ErbB2 receptor as a target since it is an ideal oncoantigen. It is overexpressed on the cell membrane by several carcinomas for which it plays an essential role in driving their progression. Most oncoantigens are self-tolerated molecules. To circumvent immune tolerance we generated two plasmids (RHuT and HuRT) coding for chimeric rat/human ErbB2 proteins. Their immunogenicity was compared in wild type mice naturally tolerant for mouse ErbB2, and in transgenic mice that are also tolerant for rat or human ErbB2. In several of these mice, RHuT and HuRT elicited a stronger anti-tumor response than plasmids coding for fully human or fully rat ErbB2. The ability of heterologous moiety to blunt immune tolerance could be exploited to elicit a significant immune response in patients. A clinical trial to delay the recurrence of ErbB2+ carcinomas of the oral cavity, oropharynx and hypopharynx is awaiting the approval of the Italian authorities.

Immune Mechanisms and Therapeutic Potential of CpG Oligodeoxynucleotides

Unmethylated CpG motifs in bacterial DNA and synthetic oligodeoxynucleotides activate immune cells that express Toll-like Receptor 9. Activation through this receptor triggers cellular signaling that leads to production of a proinflammatory and a Th1-type, antigen-specific immune response. The immunostimulatory effects of CpG oligodeoxynucleotides confer protection against infectious disease, allergy and cancer in animal models, and clinical trials have been initiated. However, CpG oligodeoxynucleotides may exacerbate disease in some situations. We will review current concepts in the mechanisms of activating Toll-like Receptor 9 with CpG oligodeoxynucleotides and highlight opportunities for using large animal models to better determine the mechanisms of action.

CpG motifs of bacterial DNA exert protective effects in mouse models of IBD by antigen-independent tolerance induction

BACKGROUND & AIMS

Prophylactic treatment of mice with CpG motifs of bacterial DNA protects from experimental inflammatory bowel disease, at least partly via induction of inhibitory T-cells. The aim of this study was to elucidate whether these CpG-dependent protective effects require presence of bacterial flora suggesting antigen-specific regulatory activity.

METHODS

Germ-free BALB/c and IL-10(-/-) mice were treated with CpG-oligodeoxynucleotides (ODN), control-ODN, or PBS. CD4(+)CD62L(+) cells of these mice were transferred into SCID recipients. CpG-ODN-treated germ-free IL-10(-/-) mice were transferred into colitogenic environment. Monoclonal antibodies were used to neutralize TGF-beta and IFN-alpha/beta during CpG-ODN treatment. CD4(+)CD62L(+) cells of donors were evaluated for cytokine secretion and FOXP3, PD-1, and CD25 expression.

RESULTS

Compared to PBS or control-ODN treatment, CpG-ODN application to germ-free donors led to decreased intestinal inflammation as indicated by histology, decreased proinflammatory cytokines, and increased IL-10 secretion. Protection was also observed after cotransfer of cells from PBS and CpG-ODN treated donors. Anti-TGF-beta and anti-INF-alpha/beta partly reversed the protective CpG-ODN effect. CpG-ODN-treated germ-free IL-10(-/-) mice transferred into colitogenic environment developed significantly less colitis than controls but not recipients of IL-10(-/-)CD4(+)CD62L(+)cells. CD4(+)CD62L(+)cells of CpG-treated germ-free animals displayed increased expression of regulatory markers.

CONCLUSIONS

Even without pre-existence of bacterial flora CpG-ODN exposition induces tolerance, indicating that CpG-ODN-induced regulatory T-cells are not bacterial antigen specific. TGF-beta and IFN-alpha/beta play major roles in induction of regulatory cells, and although IL10-independent mechanisms play a role in CpG-ODN protection, this cytokine likely is important for the effector mechanism of CpG-ODN-induced regulatory T-cells.

Complement-induced cell death by rituximab depends on CD20 expression level and acts complementary to antibody-dependent cellular cytotoxicity

PURPOSE

The use of the CD20-specific antibody rituximab has greatly improved the response to treatment of CD20+ follicular lymphoma. Despite the success of rituximab, resistance has been reported and prognostic markers to predict individual response are lacking. The level of CD20 expression on tumors has been related to response, but results of several studies are contradictory and no clear relationship could be established. Complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) are thought to be important effector mechanisms, but the exact mechanism of rituximab-mediated cell kill is still unknown. Importantly, no data have been reported on the combined contribution of CDC and ADCC.

EXPERIMENTAL DESIGN

We have developed a system of clonally related CEM-CD20 cells by retroviral transfer of the human CD20 cDNA (n = 90). This set of cells, with the CD20 molecule as the only variable, was used to study the importance of CD20 expression level on rituximab-mediated CDC, ADCC, and the combination.

RESULTS

We show a sigmoidal correlation of CD20 expression level and rituximab-mediated killing via CDC but not ADCC. On both high and low CD20-expressing cells, all CD20 molecules were translocated into lipid rafts after rituximab binding. Furthermore, CDC and ADCC act simultaneously and CDC-resistant cells are sensitive to ADCC and vice versa.

CONCLUSIONS

These findings suggest that CDC depends on CD20 expression level and that both CDC and ADCC act complementary. These data give new insights into novel strategies to improve the efficacy of CD20-specific antibodies for the treatment of CD20+ tumors.

Comparison of d-g3139 and its enantiomer L-g3139 in melanoma cells demonstrates minimal in vitro but dramatic in vivo chiral dependency

G3139 (Genasense), an 18mer phosphorothioate antisense oligonucleotide targeted to the initiation codon region of the Bcl-2 messenger RNA (mRNA), downregulates Bcl-2 protein and mRNA expression in many cell lines. However, both the in vitro and in vivo mechanisms of action of G3139 are still uncertain. The isosequential L-deoxyribose enantiomer L-G3139, which does not downregulate Bcl-2 expression, was synthesized to study the role of the Bcl-2 protein in melanoma cells. Both D-G3139 and L-G3139 bind nonspecifically to basic fibroblast growth factor with approximately the same K(c), and cause highly effective inhibition of net formation in 518A2 melanoma cells on Matrigel. The uptakes of D-G3139 and L-G3139 in melanoma cells were also similar. However, unlike D-G3139, L-G3139 does not produce poly ADP-ribose polymerase-1 and procaspase-3 cleavage at 9.5 h after the initiation of the transfection, but can activate the intrinsic pathway of apoptosis at approximately 48 h. Furthermore, treatment of A375 melanoma human xenografts in severe combined immunodeficiency (SCID) mice demonstrates that tumor growth is not inhibited by L-G3139, whereas D-G3139 significantly inhibits the rate of tumor growth. Furthermore, the immunostimulatory properties of L-G3139 appear to be nil, which differs dramatically from those of D-G3139. In conclusion, profound differences exist between D-G3139 and L-G3139 in vivo despite their similarities in vitro.

The role of toll-like receptors in systemic lupus erythematosus

Systemic lupus erythematosus is an autoimmune disease characterized by the production of autoantibodies against a relatively limited range of nuclear antigens. These autoantibodies result in the formation of immune complexes that deposit in tissues and induce inflammation, thereby contributing to disease pathology. Growing evidence suggests that recognition of nucleic acid motifs by Toll-like receptors may play a role in both the activation of antinuclear B cells and in the subsequent disease progression after immune complex formation. The endosomal localization of the nucleic acid-sensing Toll-like receptors (TLRs), TLR3, 7, and 9, is believed to contribute to the distinction between endogenous nucleic acids and those of foreign origin. In this article we review recent work that suggests a role for the B-cell receptor and Fcgamma receptors in delivering nuclear antigens to intracellular compartments allowing TLR activation by endogenous nucleic acids. A number of in vitro studies have presented evidence supporting a role for TLRs in SLE pathology. However, recent studies that have examined the contributions of individual TLRs to SLE by using TLR-deficient mice suggest that the situation is far more complicated in vivo. These studies show that under different circumstances TLR signaling may either exacerbate or protect against SLE-associated pathology. Further understanding of the role of TLRs in pathological autoreactivity of the adaptive immune system will likely lead to important insights into the etiopathogenesis of SLE and potential targets for novel therapies.

Significant growth inhibition of orthotopic pancreatic ductal adenocarcinoma by CpG oligonucleotides in immunodeficient mice

BACKGROUND/AIMS

The high rate of local recurrence after radical resection of pancreatic ductal adenocarcinoma fosters intensive efforts to develop new approaches for adjuvant treatment. Antisense and modified oligodeoxynucleotides (ODNs) have demonstrated significant tumour growth inhibitory effects in preclinical systems. Our aim was to evaluate the possible therapeutic potential of ODNs containing unmethylated deoxycytidyl-deoxyguanosine dinucleotides (CpG motifs).

METHODOLOGY

For in vitro analysis, [(3)H]thymidine incorporation for DNA synthesis, colorimetric cell vitality assay (EZ4U assay), and DNA fragmentation assay (JAM-[(3)H]thymidine incorporation assay) to test for apoptosis were performed. In vivo testing was done on an orthotopic pancreatic xenotransplantation model using severe combined immunodeficient (SCID) beige and nude mice.

RESULTS

No significant differential effect of either control ODN or CpG-1826 ODN with regard to tumour cell proliferation or induction of apoptosis was observed in vitro. In vivo, ODN-1826 proved to have a significant inhibitory effect (up to 40% reduction of tumour weight) when compared with tumour-bearing animals treated with saline or control ODN. This was accompanied by sevenfold increase in splenomegaly and moderate hepatomegaly. The reduction of tumour weight by ODN-1826 was only slightly more pronounced in nude compared with SCID beige mice.

CONCLUSION

CpG-1826 induces significant growth-inhibitory effects on orthotopic xenotransplanted pancreatic tumours in highly immunodeficient mice, which might be explained by innate immunity mechanisms and possibly a complex interaction of tumour and stroma cells.

Progress towards in vivo use of siRNAs

RNA interference (RNAi) has become the method of choice to suppress gene expression in vitro. It is also emerging as a powerful tool for in vivo research with over 90 studies published using synthetic small interfering RNAs in mammals. These reports demonstrate the potential for use of synthetic small interfering RNAs (siRNAs) as therapeutic agents, especially in the areas of cancer and viral infection. The number of reports using siRNAs for functional genomics applications, for validation of targets for small-molecule drug development programs, and to address questions of basic biology will rapidly grow as methods and protocols for use in animals become more established. This review will first discuss aspects of RNAi biochemistry and biology that impact in vivo use, especially as relates to experimental design, and will then provide an overview of published work with a focus on methodology.

G3139 and Other CpG-Containing Immunostimulatory Phosphorothioate Oligodeoxynucleotides Are Potent Suppressors of the Growth of Human Tumor Xenografts in Nude Mice

Several phosphorothioate antisense oligodeoxynucleotides (ODN) are developed to target factors potentially involved in tumor growth and apoptosis suppression. Among them, the 18-mer G3139 (Oblimersen), which targets Bcl-2, is currently being tested in phase II and phase III clinical trials for various tumors in combination with chemotherapy. On the other hand, ODNs containing CpG dinucleotides (CpG-ODN) within specific-sequence contexts (CpG motifs) have been shown to activate rodent or primate immune cells via toll-like receptor 9 (TLR9) and have demonstrated remarkable T cell-dependent antitumor efficacy in a series of murine tumor models. However, immune cell activation by CpG-ODN is largely diminished upon C-5 methylation at CpG cytosine. As G3139 contains CpG motifs, we questioned whether the antitumor effects seen in human tumor xenografts might be abrogated by cytosine C-5 methylation of G3139, which retained the ability of G3139 to suppress Bcl-2 expression in tissue culture, or by similar derivatization of other phosphorothioate ODNs developed for the immune activation of rodent or human cells. The in vivo antitumor efficacy of the immunostimulatory H1826 and H2006 ODNs was compared with that of G3139. Bcl-2 suppression achieved by G3139 purportedly sensitizes tumor cells toward cytotoxic agents, and some of the experiments employed combinations of ODN with such drugs as cisplatin or etoposide. H1826, H2006, and G3139 all produced similar, striking, growth inhibitory effects on either H69 SCLC, A2780 ovarian carcinoma, or A549 lung adenocarcinoma human tumor xenografts at doses of 0.3 mg/kg and 1 mg/kg (H1826, H2006) or 12 mg/kg (G3139) per day. In contrast, the H2006-mC (1 mg/kg) or G3139-mC (12 mg/kg) derivatives demonstrated no significant antitumor effects. The combination of G3139 (12 mg/kg) with cisplatin produced some additive antitumor efficacy, which was not seen in combinations of G3139-mC (12 mg/kg) or H1826 (1 mg/kg) with cisplatin. G3139, at a dose of 12 mg/kg, alone induced extensive enlargement of the spleen. Immunostimulation was evaluated in vitro by flow cytometric measurements of the CD80 and CD86 activation markers found on CD19+ murine splenocytes. The CpG-ODN producing strong antitumor effects in vivo also induced these activation markers in vitro, in contrast to the in vivo inactive G3139-mC. Our data indicate a significant contribution of the immunostimulatory properties of CpG-ODN (including G3139) to the antitumor effects observed in nude mouse xenograft models. This is in contrast to previous data presented by other authors indicating that the activity of G3139 in human tumor xenografts was Bcl-2 specific. Furthermore, as nude mice are devoid of T cells, a T cell-mediated immune response apparently is not required for the potent antitumor responses observed here; innate immune responses are sufficient.

Immunomodulation and protection induced by DNA-hsp65 vaccination in an animal model of arthritis

We described a prophylactic and therapeutic effect of a DNA vaccine encoding the Mycobacterium leprae 65-kDa heat shock protein (DNA-hsp65) in experimental murine tuberculosis. However, high homology of the vaccine to the corresponding mammalian hsp60, together with the CpG motifs in the plasmidial vector, could trigger or exacerbate an autoimmune disease. In the present study, we evaluate the potential of DNA-hsp65 vaccination to induce or modulate arthritis in mice genetically selected for acute inflammatory reaction (AIR), either maximal (AIRmax) or minimal (AIRmin). Mice immunized with DNA-hsp65 or injected with the corresponding DNA vector (DNAv) developed no arthritis, whereas pristane injection resulted in arthritis in 62% of AIRmax mice and 7.3% of AIRmin mice. Administered after pristane, DNA-hsp65 downregulated arthritis induction in AIRmax animals. Levels of interleukin (IL)-12 were significantly lower in mice receiving pristane plus DNA-hsp65 or DNAv than in mice receiving pristane alone. However, when mice previously injected with pristane were inoculated with DNA-hsp65 or DNAv, the protective effect was significantly correlated with lower IL-6 and IL-12 levels and higher IL-10 levels. Our results strongly suggest that DNA-hsp65 has no arthritogenic potential and is actually protective against experimentally induced arthritis in mice.

Influence of orally administered CpG-ODNs on the humoral response to bovine serum albumin (BSA) in chickens

Synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODNs) have been reported to be effective mucosal adjuvants in mice when given orally. Studies on their effectiveness in chickens are currently very limited. This study investigated whether CpG-ODNs could adjuvant the immune response to BSA when given orally to a commercial line of SCWL chickens. In two experiments, performed over time, chickens were given selected concentrations of CpG-ODNs with BSA followed by 6 consecutive days of ad libitum access to drinking water containing 1.4 mg/ml BSA. Serum responses, and in some cases intestinal specific antibodies, were measured out to 33 days post-immunization. Birds receiving a single dose of CpG-ODN had consistently higher IgG, IgM, and IgA titers in the serum, dependent upon dose, and in specific areas of the intestine when compared to the non-immunized and BSA only groups. These findings suggest that a single oral CpG-ODN administration can accelerate the kinetics of antigen specific antibodies of all three isotypes in commercial-strain chickens immunized via the drinking water using common protein antigen.

A Toll for lupus

Toll-like receptor (TLR)-9 recognizes CpG motifs in microbial DNA. TLR9 signalling stimulates innate antimicrobial immunity and modulates adaptive immune responses including autoimmunity against chromatin, e.g., in systemic lupus erythematosus (SLE). This review summarizes the available data for a role of TLR9 signalling in lupus and discusses the following questions that arise from these observations: 1) Is CpG-DNA/TLR9 interaction involved in infection-induced disease activity of lupus? 2) What are the risks of CpG motifs in vaccine adjuvants for lupus patients? 3) Is TLR9 signalling involved in the pathogenesis of lupus by recognizing self DNA?

Molecular mechanisms of autoimmunity triggered by microbial infection

Autoimmunity can be triggered by microbial infection. In this context, the discovery of Toll-like receptors (TLRs) provides new insights and research perspectives. TLRs induce innate and adaptive antimicrobial immune responses upon exposure to common pathogen-associated molecules, including lipopeptides, lipopolysaccharides, and nucleic acids. They also have the potential, however, to trigger autoimmune disease, as has been revealed by an increasing number of experimental reports. This review summarizes important facts about TLR biology, available data on their role in autoimmunity, and potential consequences for the management of patients with autoimmune disease.

CpG-independent synergistic induction of beta-chemokines and a dendritic cell phenotype by orthophosphorothioate oligodeoxynucleotides and granulocyte-macrophage colony-stimulating factor in elutriated human primary monocytes

Chemokines attract leukocytes bearing the relevant chemokine receptors and regulate innate immune responses. CpG oligodeoxynucleotides (ODN) and GM-CSF are potent vaccine adjuvants and in combination induce enhanced Th1 responses by mechanisms yet to be determined. We have examined combinations of CpG- or non-CpG-ODN and GM-CSF for effects on the production of chemokines and the differentiation of monocytes to dendritic cells. High levels of the Th1-attracting, HIV-1-inhibitory chemokines, CCL3/MIP-1alpha and CCL4/MIP-1beta, were induced in human primary monocytes when CpG- or non-CpG-ODN was combined with GM-CSF, but not with IL-4 or IFN-gamma. The synergistic induction of beta-chemokines by non-CpG-ODN was phosphorothioate (PS) chemistry dependent and inhibited by blocking endosome maturation/acidification and ERK1/2 activation. Chemokine and TLR9 mRNAs were induced by PS-ODN. Cells treated with non-CpG PS-ODN and GM-CSF expressed dendritic cell marker CD83 and high levels of HLA-DR and costimulatory molecules, and were CD14(-) or CD14(dim), consistent with monocyte differentiation into a dendritic cell phenotype. The induction of CD83 and beta-chemokines was tyrosine phosphorylation dependent. Secreted CCL3 and CCL4 were detected as a heterodimer. Our results indicate the CpG-independent synergy between PS-ODN and GM-CSF mediated through chemokine and dendritic cell induction. In addition, our observations suggest that PS-ODN plus GM-CSF may be useful as potent ex vivo dendritic cell differentiation/maturation agents for dendritic cell therapy and as vaccine adjuvants for tumor and infectious microorganisms, including HIV-1.

Unique toxicities and resistance mechanisms associated with monoclonal antibody therapy

Anti-CD20 therapy has had a truly dramatic impact on treatment and outcome of patients with follicular lymphoma. Unfortunately, the majority of responses to single-agent rituximab are incomplete, and all patients with follicular lymphoma will experience disease progression at some point following rituximab therapy. Rituximab has multiple mechanisms of inducing in vivo cytotoxicity, including antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity, direct apoptotic signaling, and possible vaccinal effects. The cellular microenvironment within follicular lymphoma has a profound impact on which mechanism is dominant, and confers resistance in many situations. Both tumor-associated and host-associated factors also contribute to rituximab resistance. There are multiple potential approaches to overcoming rituximab resistance, including rational biologic combination immunotherapy, engineered antibodies, and radioimmunoconjugates. Improved ability to overcome resistance will require further elucidation of critical signaling pathways involved in rituximab induced cytotoxicity and a comprehensive understanding of interactions between its multiple mechanisms of action.

Immune stimulation in the silkworm, Bombyx mori L., by CpG oligodeoxynucleotides

Synthetic ODNs containing unmethylated CpG dinucleotides are known to stimulate immune responses in vertebrates, but so far the effect has not been studied in insects. In this report, we describe an induction of immune response following injection of oligodeoxynucleotides (ODNs) into the insect hemocoel. The fifth instar silkworm (Bombyx mori L.) larvae were injected with several synthetic ODNs containing variable number of unmethylated CpG motifs, heat-denatured genomic DNA of B. mori itself, or intact genomic DNA to observe a new induction pattern in the insect immune mechanism. When the induction of immune response was examined based on the expression rates of genes for antibacterial peptides such as attacin and cecropin, we could confirm that it was triggered upon injection of ODNs. The expression was, however, neither dependent on numbers of CpG motifs nor methylation of CpGs in ODNs. Furthermore, it was confirmed that the presence of CpG in ODN was not involved in the induction pattern of insect immunity caused by ODNs, although it has been reported that vertebrates respond in a specific manner against invading ODNs containing CpG dinucleotides. In addition, insect immunity was not stimulated by injection of intact DNA from host. In contrast, the injection of denatured genomic DNA provoked the host immune reaction. Taken together, our data suggest that foreignness of ODNs or DNA might be a key factor in the induction of insect immunity.

Contrasting activity of cytosin-guanosin dinucleotide oligonucleotides in mice with experimental colitis

Intestinal inflammation in inflammatory bowel disease (IBD) and experimental models of colitis is characterized by a dysregulated intestinal immune response with elevated levels of Th1 cytokines. The luminal flora has been implicated as a major factor contributing to the initiation and perpetuation of inflammation in experimental colitis by mechanisms not known. Bacterial DNA contains unmethylated cytosin-guanosin dinucleotides (CpG) which strongly activate Th1-mediated immune responses. To test whether these CpG-motifs modulate intestinal inflammation we treated mice with dextran sulphate sodium (DSS)-induced colitis with CpG-containing oligodeoxynucleotides (CpG-ODN). CpG-ODN given after the onset of DSS colitis aggravated the disease, as indicated by a significantly increased loss of body weight and a 30% increase of the histological score. Further, we found a severe increase of proinflammatory cytokines (interleukin (IL)-6: 40-fold; interferon (IFN)-gamma: 11-fold). In a pretreatment setting CpG-ODN reduced weight loss significantly and reduced intestinal inflammation by 45%. Colonic IFN-gamma and IL-6 mRNA levels were reduced by 75%, and IL-10 was elevated by 400% compared to controls. The prophylactic CpG-effect was not imitated by IL-12 because IL-12 pretreatment was not protective. In time-course experiments, CpG-ODN pretreatment over 5 days resulted in a tolerance effect concerning its IFN-gamma-inducing quality, and during the following days of colitis induction IL-10 secretion from mesenterial lymph node cells was elevated compared to controls. Therefore, the prophylactic effect of CpG-ODN might be explained by its tolerizing effect and/or the increased ability for IL-10 production during the consecutive intestinal inflammation.

Canine rabies DNA vaccination: a single-dose intradermal injection into ear pinnae elicits elevated and persistent levels of neutralizing antibody

Rabid dog exposures cause >99% of human rabies deaths world-wide. In developing countries, where dogs are the viral reservoir, the 30-50% vaccination coverage of dog populations is insufficient to break the disease transmission cycle. In addition, many vaccines currently used in developing countries fail to maintain detectable levels of neutralizing antibody. The poor vaccination coverage with inadequate vaccines, in addition to the difficulty in locating dogs for booster vaccinations, suggest that an inexpensive vaccine that elicits long-term immunity after a single-dose vaccination could improve control of canine rabies in developing countries. One solution could be a DNA vaccine. This study was designed to evaluate in dogs the ability of different methods of a single-dose DNA vaccination to elicit enhanced levels of neutralizing antibody. Intradermal (i.d.) vaccination into ear pinnae elicited elevated and long-lasting levels of neutralizing antibody. Minimal or undetectable levels of neutralizing antibody were detected after vaccination into quadriceps muscle, gene gun vaccination into ear pinnae or i.d. vaccination into the neck. Intramuscular (i.m.) or gene gun vaccinations did not "immunologically prime" a majority of dogs vaccinated by these routes. The passive transfer of sera from dogs that had been vaccinated i.d. in ear pinnae protected mice against rabies virus challenge. A single-dose i.d. rabies DNA vaccination into ear pinnae could aid in the control of canine rabies in developing countries.

Hierarchical recognition of CpG motifs expressed by immunostimulatory oligodeoxynucleotides

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs trigger human PBMC to proliferate and secrete Ig, cytokines and chemokines. CpG ODN have entered clinical trials, and show promise as vaccine adjuvants, antiallergens, and for the treatment of infectious diseases and cancer. ODNs under consideration for human use vary in the sequence, number and location of the CpG motifs they contain. Yet little is known of the magnitude of the immune response elicited by these diverse ODNs, or the rules governing their interaction with immune cells. This work compares the proliferative, IgM, IL-6 and IP-10 response of PBMC from normal donors to a diverse panel of CpG ODNs. Results indicate that ODNs expressing 3-4 different CpG motifs are strongly stimulatory. The location of these motifs is important, with those at the 5' end exerting the greatest influence on ODN activity. These findings provide a basis for the rational design of ODNs optimized for clinical use.

Single dose of a vaccine based on DNA encoding mycobacterial hsp65 protein plus TDM-loaded PLGA microspheres protects mice against a virulent strain of Mycobacterium tuberculosis

The high incidence of tuberculosis around the world and the inability of BCG to protect certain populations clearly indicate that an improved vaccine against tuberculosis is needed. A single antigen, the mycobacterial heat shock protein hsp65, is sufficient to protect BALB/c mice against challenge infection when administered as DNA vaccine in a three-dose-based schedule. In order to simplify the vaccination schedule, we coencapsulated hsp65-DNA and trehalose dimicolate (TDM) into biodegradable poly(DL-lactide-co-glycolide) (PLGA) microspheres. BALB/c mice immunized with a single dose of DNA-hsp65/TDM-loaded microspheres produced high levels of IgG2a subtype antibody and high amounts of IFN-gamma in the supernatant of spleen cell cultures. DNA-hsp65/TDM-loaded microspheres were also able to induce high IFN-gamma production in bulk lung cells from challenged mice and confer protection as effective as that attained after three doses of naked DNA administration. This new formulation also allowed a ten-fold reduction in the DNA dose when compared to naked DNA. Thus, this combination of DNA vaccine and adjuvants with immunomodulatory and carrier properties holds the potential for an improved vaccine against tuberculosis.

The antisense approach in amyloid light chain amyloidosis: identification of monoclonal Ig and inhibition of its production by antisense oligonucleotides in in vitro and in vivo models

Primary amyloid L chain (AL) amyloidosis is a plasma cell disorder in which depositions of AL cause progressive organ failure. The lack of effective therapies for this fatal disease prompts exploration of newer treatment avenues. We have investigated the application of antisense oligonucleotides (AS) for the inhibition of monoclonal Ig production. The monoclonal L chain was identified by using primers designed for amplifying the human lambda Ig V (Vlambda) region. We demonstrated that AS against L chain complementarity-determining regions inhibited the production of L chain in vitro. RPMI 8226 myeloma cells injected in SCID mice developed s.c. tumors. RT-PCR analysis showed Vlambda mRNA expression in the tumors. In addition, the presence of human Ig in the sera of mice given injection of RPMI 8226 cells was confirmed by ELISA. Administration of AS inhibited the expression of Vlambda mRNA in the s.c. tumors and decreased the concentration of L chain in serum. Therefore, we have shown that it is possible to determine the sequence of Vlambda mRNA and design specific complementary oligonucleotides, suggesting that treatment with Vlambda antisense could represent a rational novel approach to improve treatment outcome in AL amyloidosis.

Treatment of established asthma in a murine model using CpG oligodeoxynucleotides

Allergen immunotherapy is an effective but underutilized treatment for atopic asthma. We have previously demonstrated that CpG oligodeoxynucleotides (CpG ODN) can prevent the development of a murine model of asthma. In the current study, we evaluated the role of CpG ODN in the treatment of established eosinophilic airway inflammation and bronchial hyperreactivity in a murine model of asthma. In this model, mice with established ovalbumin (OVA)-induced airway disease were given a course of immunotherapy (using low doses of OVA) in the presence or absence of CpG ODN. All mice then were rechallenged with experimental allergen. Untreated mice developed marked airway eosinophilia and bronchial hyperresponsiveness, which were significantly reduced by treatment with OVA and CpG. CpG ODN leads to induction of antigen-induced Th1 cytokine responses; successful therapy was associated with induction of the chemokines interferon-gamma-inducible protein-10 and RANTES and suppression of eotaxin. Unlike previous studies, these data demonstrate that the combination of CpG ODN and allergen can effectively reverse established atopic eosinophilic airway disease, at least partially through redirecting a Th2 to a Th1 response.

Discovery and development of respirable antisense therapeutics for asthma

Respirable antisense oligonucleotides (RASONs) represent a novel class of respiratory therapeutic molecules with the potential to specifically address the challenges posed by the successes of the Human Genome Program, namely, the need to rapidly identify the critical pulmonary disease-relevant drugable targets from the vast pool of 30,000-40,000 human genes and to discover and develop drugs that specifically attack these targets. We have shown that EPI-2010, a RASON targeting the adenosine A1 receptor, a G-protein coupled receptor that has been implicated in the regulation of three major determinants of asthma, can be delivered directly to the target disease tissue as an aerosol formulation. In vivo efficacy, absorption, distribution, metabolism, and excretion (ADME), and safety studies of inhaled EPI-2010 employing animal models of human asthma suggest that the RASON approach enables the specific delivery of efficacious, safe, and long-acting doses of phosphorothioate oligonucleotides to the respiratory tract. Moreover, these data indicate that RASONs truly have the potential to address the respiratory drug discovery bottleneck of the postgenomic era, that is, the ability to rapidly validate disease targets and develop pulmonary disease therapeutics for these validated targets.

Hammerhead ribozymes for target validation

Expensive failures in the pharmaceutical industry might be avoided by target validation at an early stage. Often, the full consequences of inhibiting a chosen drug target do not emerge until late in the development process. One option is to use hammerhead ribozymes as highly specific ribonucleases targeted exclusively at the mRNA encoding the target protein. The first part of this review is concerned with the mechanism and design of hammerhead ribozymes. This includes the chemistry of their action, specificity of cleavage and ability to discriminate between different mRNAs and selection of suitable cleavage sites. In considering their use for target validation, hammerhead ribozymes are divided into two categories. Endogenous ribozymes are transcribed inside the cell where they act whilst exogenous are introduced into the cell from outside. Exogenous ribozymes are synthesised chemically and must be protected against cellular nucleases. Information is provided on transfection methods and vectors that have been used with endogenous ribozymes as well as synthesis and chemical modification of exogenous ribozymes. Of proteins inhibited in cells or whole organisms, those in animal experiments are emphasised. Comparisons are made with other approaches, especially the use of antisense oligonucleotides or RNA.

CpG oligodeoxynucleotides as vaccine adjuvants in primates

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs act as immune adjuvants in mice, boosting the humoral and cellular response to coadministered Ags. CpG ODN that stimulate human PBMC are only weakly active in mice. Thus, alternative animal models are needed to monitor the activity and safety of "human" CpG ODN in vivo. This work demonstrates that rhesus macaques recognize and respond to the same CpG motifs that trigger human immune cells. Coadministering CpG ODN with heat-killed Leishmania vaccine provided significantly increased protection of macaques against cutaneous Leishmania infection. These findings indicate that rhesus macaques provide a useful model for studying the in vivo activity of human CpG motifs, and that ODN expressing these motifs act as strong immune adjuvants.

In vivo pro-apoptotic and antitumor efficacy of a c-Raf antisense phosphorothioate oligonucleotide: relationship to tumor size

Previously, we have shown that a phosphorothioate antisense oligonucleotide (ODN) targeted against c-raf RNA (ISIS5132; cRaf-AS) induces apoptosis in human tumor cells. We now show that the same ODN also efficiently triggers apoptosis in human tumor xenografts in nu/nu mice. Although cRaf-AS showed a clearly inhibitory effect on the growth of established tumors (approximately 150 mm3) compared to a mismatched control ODN (MM), tumor progression was not prevented. This correlated with a partial refractoriness of the tumor to cRaf-AS-induced cell killing, which seemed to be due to an inhomogeneous and inefficient penetration of the ODN into the tumor tissue rather than cellular resistance. In agreement with this conclusion, we found that growth of small tumors (<50 mm3) was completely inhibited concomitantly with an accumulation of the ODN throughout the tumor. These data show that the cRaf-AS is a highly efficacious antitumor agent, provided accessibility into the tumor tissue is warranted, and suggest that PS-AS-ODN treatment may be particularly useful in an adjuvant setting.

Phosphodiester oligonucleotides inhibit mitosis and trigger apoptosis by a non-antisense, p53-mediated mechanism

Oligodeoxyribonucleotides (ODNs) are currently employed to switch-off genes selectively routinely in the laboratory practice. The drawback of ODN application is that they have been often reported to elicit non-antisense effects by different mechanisms. Recently, it has been shown that double-stranded DNA oligonucleotides (30-mers) with protruding ends activate p53 in a cell-free system. In a previous work, we described that simple addition to the culture medium of heterogeneous DNA combined with cationic lipids culminated in inhibition of mitosis and induction of apoptosis. Here, we report that the same effects are achieved by lipotransfecting cultured cells with phosphorodiester ODNs (30-mers). Such effects of ODN were mediated by a non-antisense mechanism that required the wild-type form of the p53 oncosuppressor protein and was dependent on ODN concentration. Mitosis inhibition and apoptosis induction appeared to be determined by the 3' and 5' free ends of ODNs, which activated p53 independently from their sequence. Most probably, this mechanism is analogous to that evoked by genotoxic agent-induced DNA damage or by lipotransfecting cells with heterogeneous DNA.

Oligonucleotide-based strategies to reduce gene expression

Research on embryonic development and differentiation provides a sensitive, but challenging opportunity to use a variety of techniques designed to modulate gene expression. Changes in the expression of a single gene can alter levels of other genes and provide information on developmentally regulated gene expression pathways. The morphological consequences of altered gene expression can link gene expression to developmental fate. Oligonucleotide-based approaches offer a variety of means to potentially disrupt normal gene expression. The basis for some of these approaches is presented in this review.