Immunomodulatory oligonucleotides containing a cytosine-phosphate-2'-deoxy-7-deazaguanosine motif as potent toll-like receptor 9 agonists

Effect of synthetic agonists of toll-like receptor 9 on canine lymphocyte proliferation and cytokine production in vitro

Synthetic agonists of TLR9 containing novel DNA structures and R'pG (wherein R=1-(2'-deoxy-beta-d-ribofuranosyl)-2-oxo-7-deaza-8-methyl-purine) motifs, referred to as immune modulatory oligonucleotides (IMOs), have been shown to stimulate T(H)-1-type-immune responses and potently reverse allergen-induced T(H)-2 responses to T(H)-1 responses in vitro and in vivo in mice. In order to investigate the immunomodulatory potential of IMOs in dogs, canine peripheral blood mononuclear cells (PBMC) from healthy dogs were stimulated with three different IMOs and a control IMO, alone or in combination with concanavalin A (ConA). Lipopolysaccharide (LPS) was used as a positive control for B lymphocyte activation. Carboxyfluorescein diacetate succinimidyl ester and phenotype staining was used to tag proliferating T and B lymphocytes (CD5(+) and CD21(+)) by flow cytometry. Real-time PCR and ELISA were processed to assay cytokine production of IFN-gamma, IL-10, TGF-beta, IL-6 and IL-10. Like LPS, IMOs alone induced neither proliferation of CD5(+) T cells nor CD21(+) B cells, but both LPS and IMO had the capacity to co-stimulate ConA and induced proliferation of B cells. In combination with ConA, one of the IMOs (IMO1) also induced proliferation of T cells. IMO1 also significantly enhanced the expression of IFN-gamma on the mRNA and protein level in canine PBMC, whereas expression of IL-10, TGF-beta and IL-4 mRNAs was not induced by any of the IMOs. These results indicate that in canine PBMC from healthy dogs, IMO1 was able to induce a T(H)-1 immune response including T- and B-cell proliferation.

2'-Deoxyimmunosine: stereoselective synthesis, base pairing and duplex stability of oligonucleotides containing 8-oxo-7-thiaguanine

Oligonucleotides containing 7-thia-8-oxoguanine represent a new class of molecules in which sulfur replaces the 7-nitrogen of a purine base. The monomeric 7-thia-8-oxoguanine 2'-deoxyribonucleoside (2'-deoxyimmunosine, 4) was prepared by nucleobase anion glycosylation in a regio- and stereoselective way employing 5-{[(di-n-butylamino)methylidene]amino}thiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione (18) and 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-d-erythro-pentofuranose (6). The nucleoside was converted into the phosphoramidite and oligonucleotides were prepared by solid-phase synthesis. Oligonucleotide duplexes containing the 4-dC base pair show a similar stability as those containing the dG-dC motif. Thus the sterically demanding sulfur and the additional 8-oxo group are well accommodated in the major groove of DNA. As expected, compound 4 does not form a Hoogsteen pair, as reported for 8-oxo-2'-deoxyguanosine. Compared to 2'-deoxyguanosine, 2'-deoxyimmunosine shows a better mismatch discrimination in Watson-Crick base pairs.

Differential expression of Toll-like receptor 2 (TLR2) and responses to TLR2 ligands between human and murine vascular endothelial cells

Toll-like receptors (TLRs) initiate and maintain host defenses and inflammation, and directly contribute to diseases such as atherosclerosis. It is not completely understood in what cell types proatherogenic TLR-induced signaling arises and, particularly, there is uncertainty regarding the potential functional role of TLR2 in endothelial cells (ECs). We determined TLR2 and TLR4 gene expression in four different human and two different murine primary ECs using gene array analysis, RT-PCR, and flow cytometry and confirmed these data by functional studies by stimulating ECs with the corresponding TLR ligands. TLR4 was expressed in all human and murine ECs and these cells responded to stimulation with LPS. Faint expression of TLR2 was observed in human ECs, whereas murine ECs express considerable amounts of TLR2 mRNA. Human ECs failed to respond to TLR2 ligands while murine ECs responded to TLR2 ligands. Furthermore, in murine ECs, TLR2 was located on the cell surface while in human ECs, TLR2 was sequestered in intracellular compartments. After IFN-gamma or IL-1beta stimulation, TLR2 translocated to the cell surface of human ECs. In conclusion, TLR2 is expressed intracellularly in human ECs and, therefore, TLR2 ligands are inaccessible to the receptor. Murine ECs express membrane TLR2 and respond to TLR2 ligands, but human ECs normally will not respond unless they are first primed with inflammatory stimulation, which appears to trigger translocation of TLR2 to the cell surface.

Synthetic agonists of Toll-like receptors 7, 8 and 9

TLRs (Toll-like receptors) are a family of innate immune receptors that induce protective immune responses against infections. Single-stranded viral RNA and bacterial DNA containing unmethylated CpG motifs are the ligands for TLR7 and TLR8 and 9 respectively. We have carried out extensive structure–activity relationship studies of DNA- and RNA-based compounds to elucidate the impact of nucleotide motifs and structures on these TLR-mediated immune responses. These studies have led us to design novel DNA- and RNA-based compounds, which act as potent agonists of TLR9 and TLR7 and 8 respectively. These novel synthetic agonists produce different immune response profiles depending on the structures and nucleotide motifs present in them. The ability to modulate TLR-mediated immune responses with these novel DNA- and RNA-based agonists in a desired fashion may allow targeting a broad range of diseases, including cancers, asthma, allergies and infections, alone or in combination with other therapeutic agents, and their use as adjuvants with vaccines. IMO-2055, our first lead candidate, is a TLR9 agonist that is currently in clinical evaluation in oncology patients. A second candidate, IMO-2125, is also a TLR9 agonist that has been shown to induce high and sustained levels of IFN (interferon) in non-human primates and is being evaluated in HepC-infected human subjects.

Agonists of Toll-like receptor 9 containing synthetic dinucleotide motifs

Oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs activate Toll-like receptor 9 (TLR9). Our previous studies have shown that ODNs containing two 5'-ends are more immunostimulatory than those with one 5'-end. In the present study, to understand the role of functional groups in TLR9 recognition and subsequent immune response, we substituted C or G of a CpG dinucleotide with 5-OH-dC, 5-propyne-dC, furano-dT, 1-(2'-deoxy-beta- d-ribofuranosyl)-2-oxo-7-deaza-8-methyl-purine, dF, 4-thio-dU, N(3)-Me-dC, N (4)-Et-dC, Psi-iso-dC, and arabinoC or 7-deaza-dG, 7-deaza-8-aza-dG, 9-deaza-dG, N(1)-Me-dG, N(2)-Me-dG, 6-Thio-dG, dI, 8-OMe-dG, 8-O-allyl-dG, and arabinoG in ODN containing two 5'-ends. Agonists of TLR9 containing cytosine or guanine modification showed activity in HEK293 cells expressing TLR9, mouse spleen, and human cell-based assays and in vivo in mice. The results presented here provide insight into which specific chemical modifications at C or G of the CpG motif are recognized by TLR9 and the ability to modulate immune responses substituting natural C or G in immune modulatory oligonucleotides.

Immune modulatory oligonucleotides in the prevention and treatment of OVA-induced eustachian tube dysfunction in rats

BACKGROUND

Otitis media with effusion (OME) is often associated with allergies. Immune modulatory oligonucleotides (IMO) mediate allergic inflammation and may therefore be efficacious in the treatment of airway inflammation.

OBJECTIVE

To evaluate the role of an IMO via transtympanic mucosal application in prevention and treatment of ovalbumin-induced OME.

DESIGN

Forty brown Norway rats were divided into control and treatment groups. Eustachian tube dysfunction was evaluated by passive opening pressures, passive closing pressures, active clearance of negative pressure, and mucociliary clearance transit time.

RESULTS

Rats who underwent IMO treatment required 50% less pressure to open and close the eustachian tube (P < 0.05) and were able to actively clear 50% more negative pressure than the ovalbumin-control rats (P < 0.001). The treatment rats' mucociliary clearance time was half that of the control group (P < 0.001).

CONCLUSION

IMO via transtympanic application can prevent and treat allergy-induced eustachian tube dysfunction in rats. IMO may offer substantial promise in the future management of OME.

Stabilized immune modulatory RNA compounds as agonists of Toll-like receptors 7 and 8

Viral and synthetic single-stranded RNAs are the ligands for Toll-like receptor (TLR)7 and TLR8. However, single-stranded RNA is rapidly degraded by ubiquitous RNases, and the studies reported to date have used RNA with lipid carriers. To overcome nuclease susceptibility of RNA, we have synthesized several RNAs incorporating a range of chemical modifications. The present study describes one pool of RNA compounds, referred to as stabilized immune modulatory RNA (SIMRA) compounds, in which two RNA segments are attached through their 3' ends. SIMRA compounds showed greater stability in human serum compared with linear RNA and activated human TLR8, but not TLR7, in HEK293 cells without using lipid carriers. Interestingly, another set of SIMRA compounds containing 7-deazaguanosine substituted for natural guanosine activated human TLR7 and TLR8. Additionally, TLR7- and TLR8-activating compounds, but not the compounds that activated only TLR8, stimulated mouse immune cells in vitro and in vivo and produced dose-dependent T helper 1-type cytokines. Both types of compounds activated human peripheral blood mononuclear cells, but only TLR7- and TLR8-activating compounds activated plasmacytoid dendritic cells and produced high levels of IFN-alpha. In monkeys, s.c. administration of both types of SIMRA compounds induced transient changes in peripheral blood monocytes and neutrophils, and activated T lymphocytes, monocytes, and NK cells. Both types of compounds induced IFN-gamma-inducible protein 10, but only the 7-deazaguanosine-containing compound that activated both TLR7 and TLR8 induced IFN-alpha in monkeys. This is a comprehensive study of RNA-based compounds containing structures and synthetic stimulatory motifs in mouse, monkey, and human systems without using lipid carriers.

TLR9 agonist acts by different mechanisms synergizing with bevacizumab in sensitive and cetuximab-resistant colon cancer xenografts

Synthetic agonists of Toll-like receptor 9 (TLR9), a class of agents that induce specific immune response, exhibit antitumor activity and are currently being investigated in cancer patients. Intriguingly, their mechanisms of action on tumor growth and angiogenesis are still incompletely understood. We recently discovered that a synthetic agonist of TLR9, immune modulatory oligonucleotide (IMO), acts by impairing epidermal growth factor receptor (EGFR) signaling and potently synergizes with anti-EGFR antibody cetuximab in GEO human colon cancer xenografts, whereas it is ineffective in VEGF-overexpressing cetuximab-resistant GEO cetuximab-resistant (GEO-CR) tumors. VEGF is activated by EGFR, and its overexpression causes resistance to EGFR inhibitors. Therefore, we used IMO and the anti-VEGF antibody bevacizumab as tools to study IMO's role on EGFR and angiogenesis and to explore its therapeutic potential in GEO, LS174T, and GEO-CR cancer xenografts. We found that IMO enhances the antibody-dependent cell-mediated cytotoxicity (ADCC) activity of cetuximab, that bevacizumab has no ADCC, and IMO is unable to enhance it. Nevertheless, the IMO-plus-bevacizumab combination synergistically inhibits the growth of GEO and LS174T as well as of GEO-CR tumors, preceded by inhibition of signaling protein expression, microvessel formation, and human, but not murine, VEGF secretion. Moreover, IMO inhibited the growth, adhesion, migration, and capillary formation of VEGF-stimulated endothelial cells. The antitumor activity was irrespective of the TLR9 expression on tumor cells. These studies demonstrate that synthetic agonists of TLR9 interfere with growth and angiogenesis also by EGFR- and ADCC-independent mechanisms affecting endothelial cell functions and provide a strong rationale to combine IMO with bevacizumab and EGFR inhibitory drugs in colon cancer patients.

Oral administration of a synthetic agonist of Toll-like receptor 9 potently modulates peanut-induced allergy in mice

BACKGROUND

Agonists of Toll-like receptor 9 have been shown to induce potent T(H)1-type immune responses and prevent and reverse ovalbumin-induced T(H)2-dominant allergic asthma in mice.

OBJECTIVE

We examined oral administration of a synthetic agonist of Toll-like receptor 9 (immune modulatory oligonucleotide [IMO]) to modulate peanut-induced allergy in mice.

METHODS

In the prevention model mice were sensitized 3 times by means of oral administration of peanut in the presence or absence of IMO. In a treatment protocol mice were sensitized orally with peanut on days 0 and 14 and treated 4 times with oral administration of IMO starting on day 21.

RESULTS

In the prevention study mice that received the combination of IMO/peanut showed decreased IgE and increased IgG2a levels in the serum and intestinal tissue compared with mice sensitized with peanut only. In spleen cell recall experiments, production of IL-5 and IL-13 was inhibited and production of IFN-gamma was increased in mice immunized with the peanut/IMO combination compared with those sensitized with peanut only. In the treatment model IMO-treated mice showed decreased IgE, IL-5, and IL-13 levels and increased IgG2a and IFN-gamma levels in the serum, intestines, and spleen cells compared with PBS-treated mice. A reduction in local inflammation and restoration of normal structure in the intestines was found in the mice that received IMO in both models.

CONCLUSION

These results indicate that IMOs can switch peanut-induced T(H)2 immune responses toward T(H)1 responses accompanied by reduced inflammation in the gastrointestinal tract and anaphylaxis in both the prevention and treatment models.

CLINICAL IMPLICATIONS

IMOs might be suitable candidates for the management of peanut-induced allergy.

Current and future drugs targeting one class of innate immunity receptors: the Toll-like receptors

Innate immunity receptors are germline-encoded receptors that can sense molecular signatures of pathogens and cancer cells. Recent advances in immunology demonstrate the key role of these receptors in inflammation and initiation of subsequent immune responses, including adaptive immunity. Pharmaceutical interest in this field has grown with the retrospective demonstration that some marketed drugs targeting cancer or infectious diseases act via those receptors. In this review, I present an update on the scientific rationale for targeting one class of innate immunity receptor, the Toll-like receptors, and an update on the development status of corresponding drug candidates in infectious diseases, cancer, allergy and vaccines.

Bacterial proteins and CpG-rich extrachromosomal DNA in potential cancer therapy

Bacterial proteins such as azurin and Laz have recently been shown to enter preferentially to cancer cells and kill them by multiple mechanisms. Historically, bacterial DNA, particularly the unmethylated CpG dinucleotides, have been shown to trigger activation of specific Toll-like receptors (TLRs) in immune cells, leading to various cytokine and chemokine production that allows cancer cell death and their regression. However, the enhanced release of specific protein or extrachromosomal DNA by bacteria in response to exposure to cancer cells has not been previously demonstrated. In this review, we discuss how an opportunistic, extracellular pathogenic bacterium, Pseudomonas aeruginosa, senses the presence of cancer cells and releases a specific protein or extrachromosomal DNA with antitumor activity for inhibition of cancer cell growth.

Immunomodulatory oligonucleotides as novel therapy for breast cancer: pharmacokinetics, in vitro and in vivo anticancer activity, and potentiation of antibody therapy

Oligonucleotides containing CpG motifs and immunomodulatory oligonucleotides (IMO) containing a synthetic immunostimulatory dinucleotide and a novel DNA structure have been suggested to have potential for the treatment of various human diseases. In the present study, a newly designed IMO was evaluated in several models of human (MCF-7 and BT474 xenograft) and murine (4T1 syngeneic) breast cancer. Pharmacokinetics studies of the IMO administered by s.c., i.v., p.o., or i.p. routes were also accomplished. The IMO was widely distributed to various tissues by all four routes, with s.c. administration yielding the highest concentration in tumor tissue. The IMO inhibited the growth of tumors in all three models of breast cancer, with the lowest dose of the IMO inhibiting MCF-7 xenograft tumor growth by >40%. Combining the IMO with the anticancer antibody, Herceptin, led to potent antitumor effects, resulting in >96% inhibition of tumor growth. The IMO also exerted in vitro antitumor activity, as measured by cell growth, apoptosis, and proliferation assays in the presence of Lipofectin. This is the first report of the pharmacokinetics of this agent in normal and tumor-bearing mice. Based on the present results, we believe that the IMO is a good candidate for clinical development for breast cancer therapy used either alone or in combination with conventional cancer therapeutic agents.

Mutants of type II heat-labile enterotoxin LT-IIa with altered ganglioside-binding activities and diminished toxicity are potent mucosal adjuvants

The structure and function LT-IIa, a type II heat-labile enterotoxin of Escherichia coli, are closely related to the structures and functions of cholera toxin and LT-I, the type I heat-labile enterotoxins of Vibrio cholerae and enterotoxigenic Escherichia coli, respectively. While LT-IIa is a potent systemic and mucosal adjuvant, recent studies demonstrated that mutant LT-IIa(T34I), which exhibits no detectable binding activity as determined by an enzyme-linked immunosorbent assay, with gangliosides GD1b, GD1a, and GM1 is a very poor adjuvant. To evaluate whether other mutant LT-IIa enterotoxins that also exhibit diminished ganglioside-binding activities have greater adjuvant activities, BALB/c mice were immunized by the intranasal route with the surface adhesin protein AgI/II of Streptococcus mutans alone or in combination with LT-IIa, LT-IIa(T14S), LT-IIa(T14I), or LT-IIa(T14D). All three mutant enterotoxins potentiated strong mucosal immune responses that were equivalent to the response promulgated by wt LT-IIa. All three mutant enterotoxins augmented the systemic immune responses that correlated with their ganglioside-binding activities. Only LT-IIa and LT-IIa(T14S), however, enhanced expression of major histocompatibility complex class II and the costimulatory molecules CD40, CD80, and CD86 on splenic dendritic cells. LT-IIa(T14I) and LT-IIa(T14D) had extremely diminished toxicities in a mouse Y1 adrenal cell bioassay and reduced abilities to induce the accumulation of intracellular cyclic AMP in a macrophage cell line.

Experimental therapy of prostate cancer with an immunomodulatory oligonucleotide: effects on tumor growth, apoptosis, proliferation, and potentiation of chemotherapy

BACKGROUND

The present study was designed to demonstrate the therapeutic efficacy of a novel immunomodulatory oligonucleotide (IMO) for prostate cancer.

METHODS

We evaluated the effects of the IMO in xenograft (PC-3) and syngeneic (TRAMP C1) models of prostate cancer, and in prostate cancer cells. The IMO was also evaluated in combination with chemotherapy, and the in vitro expression of TLR9 was examined.

RESULTS

The IMO had significant anti-tumor activity in both prostate cancer models and almost complete tumor regression was observed when the IMO was combined with taxotere or gemcitabine. TLR9 mRNA and protein were both expressed in prostate cancer cells. The IMO also induced apoptosis and decreased proliferation and survival of PC-3 cells in vitro in the presence of Lipofectin.

CONCLUSIONS

The IMO inhibits prostate cancer growth in vivo and in vitro, and potentiates the effects of conventional chemotherapeutic agents. This is the first report of TLR9 expression in prostate cancer cells.

Structure-activity relationship studies on the immune stimulatory effects of base-modified CpG toll-like receptor 9 agonists

Synthetic oligodeoxynucleotides containing unmethylated deoxycytidylyl-deoxyguanosine dinucleotide (CpG) motifs are able to stimulate potent immune responses through a signaling pathway involving Toll-like receptor 9 (TLR9). We have investigated the structure-activity relationship (SAR) of base-modified CpG oligonucleotides with TLR9 by measuring TLR9 activation by 20-mer oligonucleotides having just a single human recognition motif (5'-GTCGTT-3') in functional cell-based TLR9 assays. Substitution of guanine by hypoxanthine and 6-thioguanine resulted in activity similar to the unmodified parent molecule, whereas purine, 2-aminopurine, 2,6-diaminopurine, and 8-oxo-7,8-dihydroguanine substitution resulted in approximately 40-60 % reduction in activity, and 7-deazaguanine substitution led to the strongest (80 %) reduction in TLR9 stimulation. Furthermore, none of the investigated modifications at C5 and N4 of cytosine were well tolerated with respect to human TLR9 stimulation. Our results are compatible with a SAR model in which guanine is recognized by the Hoogsteen site, and C5 is most critical for recognition of cytosine. In addition, we found significant species-specific differences between human and murine TLR9 recognition, which demonstrates the importance of choosing appropriate assay systems for SAR studies.

Chemotherapy and chemosensitization of non-small cell lung cancer with a novel immunomodulatory oligonucleotide targeting Toll-like receptor 9

Lung cancer is a leading cause of death world-wide and the long-term survival rate for lung cancer patients is one of the lowest for any cancer. New therapies are urgently needed. The present study was designed to evaluate an immunomodulatory oligonucleotide as a novel type of therapy for lung cancer. The in vivo effects of the immunomodulatory oligonucleotides were determined in four tumor models derived from human non-small cell lung cancer (NSCLC) cell lines (A549, H1299, H358, and H520), administered alone or in combination with conventional chemotherapeutic agents used to treat lung cancer. The in vitro effects of the immunomodulatory oligonucleotide on the growth, apoptosis, and proliferation of NSCLC cells were also determined. We also examined NSCLC cells for expression of Toll-like receptor 9 (TLR9), the receptor for the immunomodulatory oligonucleotide. We showed several important findings: (a) treatment with the immunomodulatory oligonucleotide led to potent antitumor effects, inhibiting tumor growth by at least 60% in all four in vivo models; (b) combination with the immunomodulatory oligonucleotide led to enhanced effects following treatment with gemcitabine or Alimta; (c) the immunomodulatory oligonucleotide increased apoptosis, decreased proliferation, and decreased survival in A549 cells in vitro; and (d) both TLR9 mRNA and protein were expressed in NSCLC cells. The immunomodulatory oligonucleotide has potent antitumor effects as monotherapy and in combination with conventional chemotherapeutic agents, and may act directly on NSCLC cells via TLR9. The present study provides a rationale for developing the immunomodulatory oligonucleotide for lung cancer therapy.

TLR9 in health and disease

Toll-like receptor 9 (TLR9) is specialized for the recognition of pathogenic nucleic acids. TLR9 is expressed in intracellular compartments where it responds specifically to pathogen DNA. Several factors contribute to the ability of TLR9 to discriminate between self and foreign DNA. Regulatory mechanisms of the innate and adaptive immune system exist that balance the immune responses mediated by TLR9. Short synthetic CpG oligodeoxynucleotides are used to induce controlled and directed TLR9-dependent stimulation and are effective immune modulators in preclinical and clinical studies. This review will summarize the interplay between TLR9-dependent opposing stimulatory and regulatory effects in innate and adaptive immunity.

Immunostimulatory combinations: designing the next generation of vaccine adjuvants

Agents that activate dendritic cells are essential components for vaccines and can be conceptualized as molecular adjuvants. Other molecular adjuvants affect downstream factors that shape the resulting immune response. This review provides a compendium of recently studied molecular adjuvants, focusing on CD8+ T cell responses, which have important roles in HIV vaccines. Reference is also made to CD8+ T cell antitumor responses, where parallel studies of molecular adjuvants are being pursued. Molecular adjuvants can be considered in the following groups: TNF superfamily molecules such as CD40 ligand; agonists for TLRs; agonists for NAIP, CIITA, HET-E, TP-1-leucine-rich repeat pathway receptors, such as nucleotide-binding and oligomerization domain (NOD)1, NOD2, and cryopyrin; chemokines; ILs; CSFs; IFNs; alarmins; and purinergic P2X7 receptor agonists. Complementing these positively acting agents are strategies to reduce the immunosuppressive effects of CD4+CD25+ regulatory T cells and negatively acting factors such as TGF-beta, IL-10, suppressor of cytokine signaling 1, and programmed cell death-1 using neutralizing antibodies, antisense, and small interfering RNA. Especially effective are combinations of molecular adjuvants, which can elicit a massive expansion of antigen-specific CD8+ T cells and show unprecedented efficacy in vaccine and tumor models. Taken together, these new approaches provide significant incremental progress in the development of vaccines to elicit cell-mediated immunity against HIV and other pathogens.

Novel oligodeoxynucleotide agonists of TLR9 containing N3-Me-dC or N1-Me-dG modifications

Synthetic oligodeoxynucleotides containing unmethylated CpG motifs activate Toll-Like Receptor 9 (TLR9). Our previous studies have shown the role of hydrogen-bond donor and acceptor groups of cytosine and guanine in the CpG motif and identified synthetic immunostimulatory motifs. In the present study to elucidate the significance of N3-position of cytosine and N1-position of guanine in the CpG motif, we substituted C or G of a CpG dinucleotide with N3-Me-cytosine or N1-Me-guanine, respectively, in immunomodulatory oligodeoxynucleotides (IMOs). IMOs containing N-Me-cytosine or N-Me-guanine in C- or G-position, respectively, of the CpG dinucleotide showed activation of HEK293 cells expressing TLR9, but not TLR3, 7 or 8. IMOs containing N-Me-cytosine or N-Me-guanine modification showed activity in mouse spleen cell cultures, in vivo in mice, and in human cell cultures. In addition, IMOs containing N-Me-substitutions reversed antigen-induced Th2 immune responses towards a Th1-type in OVA-sensitized mouse spleen cell cultures. These studies suggest that TLR9 tolerates a methyl group at N1-position of G and a methyl group at N3-position of C may interfere with TLR9 activation to some extent. These are the first studies elucidating the role of N3-position of cytosine and N1-position of guanine in a CpG motif for TLR9 activation and immune stimulation.

Novel toll-like receptor 9 agonist induces epidermal growth factor receptor (EGFR) inhibition and synergistic antitumor activity with EGFR inhibitors

PURPOSE

Immunostimulating Toll-like receptor 9 (TLR9) agonists cause antitumor activity interfering also with cancer proliferation and angiogenesis by mechanisms still incompletely understood. We hypothesized that modified TLR9 agonists could impair epidermal growth factor receptor (EGFR) signaling and, by this means, greatly enhance EGFR inhibitors effect, acting on both the receptor targeting and the immunologic arm.

EXPERIMENTAL DESIGN

We used a novel second-generation, modified, immunomodulatory TLR9 agonist (IMO), alone and in combination with the anti-EGFR monoclonal antibody cetuximab or tyrosine kinase inhibitor gefitinib, on the growth of GEO and cetuximab-resistant derivatives GEO-CR colon cancer xenografts. We have also evaluated the expression of several proteins critical for cell proliferation, apoptosis, and angiogenesis, including EGFR, mitogen-activated protein kinase, Akt, bcl-2, cyclooxygenase-2, vascular endothelial growth factor, and nuclear factor-kappaB.

RESULTS

IMO inhibited GEO growth and signaling by EGFR and the other proteins critical for cell proliferation and angiogenesis. IMO plus the anti-EGFR antibody cetuximab synergistically inhibited tumor growth, signaling proteins, and microvessel formation. EGFR signaling inhibition by IMO is relevant because IMO cooperated also with EGFR tyrosine kinase inhibitor gefitinib in GEO tumors, while it was inactive against GEO-CR xenografts. On the other hand, IMO boosted the non-EGFR-dependent cetuximab activity, causing a cooperative antitumor effect in GEO-CR cells. Finally, combination of IMO, cetuximab and chemotherapeutic irinotecan eradicated the tumors in 90% of mice.

CONCLUSION

IMO interferes with EGFR-related signaling and angiogenesis and has a synergistic antitumor effect with EGFR inhibitors, especially with cetuximab, boosting both the EGFR dependent and independent activity of this agent. Moreover, this therapeutic strategy could be translated in patients affected by colorectal cancer.

Toward a Unified Theory of Renal Progression

Various disciplines within nephrology investigate the mechanisms by which kidneys fail. Progress in the areas of glomerular hemodynamics, proteinuria, tubular biology, interstitial nephritis, fibroblast formation, and fibrosis have added kernels of information that together support a unified theory of renal progression. Prevention of progression to end-stage disease has largely focused on control of systemic and glomerular hypertension. Current success in delaying a decline in glomerular filtration rate underlines the promise of a more comprehensive approach. New knowledge about the cell biology of progression also suggests that other adjunctive therapies may be possible. We describe the progress and highlight those spheres where new-targeted interventions may arise.

Innate immunity for biodefense: a strategy whose time has come

Defense against biothreat agents requires a broad-spectrum approach. Modulation of the innate immune system might fulfill this requirement. Hackett's previous review of innate immune activation as a broad-spectrum biodefense strategy identified several unresolved questions. The current article is a systematic approach to answering those questions with the focused participation of research groups developing this technology. Our team of academic and industry participants reviewed the promising agents and came to the following conclusions. It is feasible to construct a biodefense platform combining synergistic agents that activate the innate immune system against a broad range of pathogens on the basis of conserved microbial components by using a nasal spray for immune activation in the respiratory and gastrointestinal tracts because these are the most likely routes of attack. It might also be possible to include agents that inhibit molecular events leading to septic shock. Innate immune-activating agents designed to activate Toll-like and other receptors will probably provide protection against the biothreat pathogen spectrum for periods ranging from 2 to 14 days for IFNs up to 26 weeks for immunomodulatory oligonucleotides. Initial treatment is proposed on the first index case or biosensor alert. Boost doses would be required. Harmful inflammation is possible, but thus far, only transient fever has been observed. Autoimmune reaction and retroviral activation have not been seen thus far in preclinical and human trials of many of these compounds. Toll-like receptor agonists caused cytokine production in all subjects tested, but genetic polymorphism reduced the response to IFN in African American subjects.