Peptide conjugation at the 5'-end of oligodeoxynucleotides abrogates toll-like receptor 9-mediated immune stimulatory activity

The orientation of CpG conjugation on aluminum oxyhydroxide nanoparticles determines the immunostimulatory effects of combination adjuvants

In subunit vaccines, aluminum salts (Alum) are commonly used as adjuvants, but with limited cellular immune responses. To overcome this limitation, CpG oligodeoxynucleotides (ODNs) have been used in combination with Alum. However, current combined usage of Alum and CpG is limited to linear mixtures, and the underlying interaction mechanism between CpG and Alum is not well understood. Thus, we propose to chemically conjugate Alum nanoparticles and CpG (with 5' or 3' end exposed) to design combination adjuvants. Our study demonstrates that compared to the 3'-end exposure, the 5'-end exposure of CpG in combination adjuvants (Al-CpG-5') enhances the activation of bone-marrow derived dendritic cells (BMDCs) and promotes Th1 and Th2 cytokine secretion. We used the SARS-CoV-2 receptor binding domain (RBD) and hepatitis B surface antigen (HBsAg) as model antigens to demonstrate that Al-CpG-5' enhanced antigen-specific antibody production and upregulated cytotoxic T lymphocyte markers. Additionally, Al-CpG-5' allows for coordinated adaptive immune responses even at lower doses of both CpG ODNs and HBsAg antigens, and enhances lymph node transport of antigens and activation of dendritic cells, promoting Tfh cell differentiation and B cell activation. Our novel Alum-CPG strategy points the way towards broadening the use of nanoadjuvants for both prophylactic and therapeutic vaccines.

Clinical effect of spleen aminopeptide on improving liver function damage and immune function in children with infant hepatitis syndrome

BACKGROUND

Infant hepatitis syndrome (IHS) is a clinical syndrome in infants less than one year of age with generalized skin jaundice, abnormal liver function, and hepatomegaly due to various etiologies such as infection.

AIM

To investigate the effect of IHS patients, after treatment with arsphenamine-based peptides, on patients' liver function damage and immune function.

METHODS

Of 110 patients with IHS treated in our hospital from January 2019 to January 2021 were grouped according to the randomized residual grouping method, with 5 cases in each group shed due to transfer, etc. Ultimately, 50 cases remained in each group. The control group was treated with reduced glutathione, and the treatment group was treated with sesquiterpene peptide based on the control group. Observe and compare the differences in indicators after treatment.

RESULTS

The comparison of serum total bilirubin, direct bilirubin, and serum alanine transferase after treatment was significantly different and lower in the treatment group than in the control group (P < 0.05). The comparison of CD4+, CD3+, CD4+/CD8+ after treatment was significantly different and higher in the treatment group than in the control group, and the comparison was statistically significant (P < 0.05). The complication of the two groups showed that the rash, cough and sputum, elevated platelets, and gastrointestinal reactions in the treatment group were significantly lower than those in the control group, and the differences were statistically significant by test (P < 0.05).

CONCLUSION

The comparative study of IHS treated with arsphenamine combined with reduced glutathione is more effective.

Introduction and History of the Chemistry of Nucleic Acids Therapeutics

This introduction charts the history of the development of the major chemical modifications that have influenced the development of nucleic acids therapeutics focusing in particular on antisense oligonucleotide analogues carrying modifications in the backbone and sugar. Brief mention is made of siRNA development and other applications that have by and large utilized the same modifications. We also point out the pitfalls of the use of nucleic acids as drugs, such as their unwanted interactions with pattern recognition receptors, which can be mitigated by chemical modification or used as immunotherapeutic agents.

Enhanced Immunostimulatory Activity of Covalent DNA Dendrons

The present study focused on the design and synthesis of covalent DNA dendrons bearing multivalent cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs) that can stimulate the immune system through the activation of TLR9. These dendrons were synthesized using branching trebler phosphoramidite containing three identical protecting groups that enabled the simultaneous synthesis of multiple strands on a single molecule. Compared with linear ODNs, covalent DNA dendrons were found to be more resistant to nuclease degradation and were more efficiently taken up by macrophage-like RAW264.7 cells. Cellular uptake was suggested to be mediated by macrophage scavenger receptors. The covalent DNA dendrons composed of multivalent immunostimulatory branches enhanced the secretion of proinflammatory cytokines TNF-α and IL-6 from RAW264.7 cells, and 9-branched DNA dendrons showed the highest enhancement. Given their enhanced efficacy, we expect covalent DNA dendrons to be useful structures of oligonucleotide medicines.

The Evolution of Antisense Oligonucleotide Chemistry-A Personal Journey

Over the last four decades, tremendous progress has been made in use of synthetic oligonucleotides as therapeutics. This has been possible largely by introducing chemical modifications to provide drug like properties to oligonucleotides. In this article I have summarized twists and turns on use of chemical modifications and their road to success and highlight areas of future directions.

Modularly Programmable Nanoparticle Vaccine Based on Polyethyleneimine for Personalized Cancer Immunotherapy

Nanoparticles (NPs) can serve as a promising vaccine delivery platform for improving pharmacological property and codelivery of antigens and adjuvants. However, NP-based vaccines are generally associated with complex synthesis and postmodification procedures, which pose technical and manufacturing challenges for tailor-made vaccine production. Here, modularly programmed, polyethyleneimine (PEI)-based NP vaccines are reported for simple production of personalized cancer vaccines. Briefly, PEI is conjugated with neoantigens by facile coupling chemistry, followed by electrostatic assembly with CpG adjuvants, leading to the self-assembly of nontoxic, sub-50 nm PEI NPs. Importantly, PEI NPs promote activation and antigen cross-presentation of antigen-presenting cells and cross-priming of neoantigen-specific CD8+ T cells. Surprisingly, after only a single intratumoral injection, PEI NPs with optimal PEGylation elicit as high as ≈30% neoantigen-specific CD8+ T cell response in the systemic circulation and sustain elevated CD8+ T cell response over 3 weeks. PEI-based nanovaccines exert potent antitumor efficacy against pre-established local tumors as well as highly aggressive metastatic tumors. PEI engineering for modular incorporation of neoantigens and adjuvants offers a promising strategy for rapid and facile production of personalized cancer vaccines.

A trustworthy CpG nanoplatform for highly safe and efficient cancer photothermal combined immunotherapy

Palladium nanosheets (Pd NSs) have recently attracted increasing research interest in the biomedical field due to their excellent near-infrared absorption, photothermal conversion capability and biocompatibility. However, the application of Pd NSs in immunotherapy has not been reported. Here, Pd NSs were used as the carriers of immunoadjuvant CpG ODNs for not only efficient delivery of CpG but also for enhancing the immunotherapeutic effects of CpG by the Pd NS-based photothermal therapy (PTT). Pd NSs had no influence on the immune system, and the prepared Pd-CpG nanocomposites, especially Pd(5)-CpG(PS), could significantly increase the uptake of CpG by immune cells and enhance the immunostimulatory activity of CpG in vitro and in vivo. With the combination of Pd(5)-CpG(PS) mediated PTT and immunotherapy, highly efficient tumor inhibition was achieved and the survival rate of the tumor-bearing mice was greatly increased depending on Pd(5)-CpG(PS) with safe near-infrared (NIR) irradiation (808 nm laser, 0.15 W cm^-2). Importantly, the combination therapy induced tumor cell death and released tumor-associated antigens, which could be effectively taken up and presented by antigen presenting cells with the assistance of CpG, leading to increased TNF-α and IL-6 production and enhanced cytotoxic T lymphocyte (CTL) activity. This work provides a new paradigm of utilizing photothermal nanomaterials for safe and highly efficient cancer photothermal combined immunotherapy.

miR29a and miR378b Influence CpG-Stimulated Dendritic Cells and Regulate cGAS/STING Pathway

The Cytosine–phosphate–guanosine (CpG) motif, which is specifically recognized intracellularly by dendritic cells (DCs), plays a crucial role in regulating the innate immune response. MicroRNAs (miRNAs) can strongly influence the antigen-presenting ability of DCs. In this study, we examine the action of miRNAs on CpG-stimulated and control DCs, as well as their effect on cyclic guanosine monophosphate-adenosine monophosphate (GMP–AMP) synthase (cGAS) and the stimulator of interferon genes (STING) signal pathway. Firstly, we selected miRNAs (miR-29a and miR-378b) based on expression in CpG-stimulated mouse bone marrow-derived dendritic cells (BMDCs). Secondly, we investigated the functions of miR-29a and miR-378b on CpG-stimulated and unstimulated BMDCs. The results showed that miR-29a and miR-378b increased expression of both the immunoregulatory DC surface markers (CD86 and CD40) and the immunosuppressive molecule CD273 by DCs. Thirdly, cytokine detection revealed that both miR-29a and miR-378b enhanced interferon-β (IFN-β) expression while suppressing tumor necrosis factor-α (TNF-α) production. Finally, our results suggest that miR-378b can bind TANK-binding kinase binding protein 1 (TBKBP1) to activate the cGAS/STING signaling pathway. By contrast, miR-29a targeted interferon regulatory factor 7 (IRF7) and promoted the expression of STING. Together, our results provide insight into the molecular mechanism of miRNA induction by CpG to regulate DC function.

Biomaterials for vaccine-based cancer immunotherapy

The development of therapeutic cancer vaccines as a means to generate immune reactivity against tumors has been explored since the early discovery of tumor-specific antigens by Georg Klein in the 1960s. However, challenges including weak immunogenicity, systemic toxicity, and off-target effects of cancer vaccines remain as barriers to their broad clinical translation. Advances in the design and implementation of biomaterials are now enabling enhanced efficacy and reduced toxicity of cancer vaccines by controlling the presentation and release of vaccine components to immune cells and their microenvironment. Here, we discuss the rational design and clinical status of several classes of cancer vaccines (including DNA, mRNA, peptide/protein, and cell-based vaccines) along with novel biomaterial-based delivery technologies that improve their safety and efficacy. Further, strategies for designing new platforms for personalized cancer vaccines are also considered.

Investigations into the efficacy of multi-component cocaine vaccines

Although cocaine addiction remains a serious health and societal problem in the United States, no FDA-approved treatment has been developed. Vaccines offer an exciting strategy for the treatment of cocaine addiction; however, vaccine formulations need to be optimized to improve efficacy. Herein, we examine the effectiveness of a tricomponent cocaine vaccine, defined as having its hapten (GNE) and adjuvant (cytosine-guanine oligodeoxynucleotide 1826, CpG ODN 1826) covalently linked via the immunogenic protein ovalbumin (OVA). The tricomponent vaccine (GNE-OVA-CpG 1826) and a vaccine of analogous, individual components (GNE-OVA+CpG ODN 1826) were found to similarly induce highly specific anticocaine antibody production in mice and block cocaine's stimulant effects in hyperlocomotor testing.

Toll-like Receptor Agonist Conjugation: A Chemical Perspective

Toll-like receptors (TLRs) are vital elements of the mammalian immune system that function by recognizing pathogen-associated molecular patterns (PAMPs), bridging innate and adaptive immunity. They have become a prominent therapeutic target for the treatment of infectious diseases, cancer, and allergies, with many TLR agonists currently in clinical trials or approved as immunostimulants. Numerous studies have shown that conjugation of TLR agonists to other molecules can beneficially influence their potency, toxicity, pharmacokinetics, or function. The functional properties of TLR agonist conjugates, however, are highly dependent on the ligation strategy employed. Here, we review the chemical structural requirements for effective functional TLR agonist conjugation. In addition, we provide similar analysis for those that have yet to be conjugated. Moreover, we discuss applications of covalent TLR agonist conjugation and their implications for clinical use.

CpG-PEG Conjugates and their Immune Modulating Effects after Systemic Administration

PURPOSE

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs were found to be able to target cells that express Toll-like receptor 9 to modulate innate and adaptive immune reactions. But their in vivo application in immunotherapy against cancer has not been successful. We attempted in this study to examine polyethylene-glycol (PEG) conjugated CpG ODNs and investigated their mechanism of immune modulation in anti-cancer therapy.

METHODS

CpG-PEG conjugates with different PEG lengths were synthesized. In vitro activity as well as in vivo pharmacokinetics and pharmacodynamics properties were evaluated.

RESULTS

CpG-PEG20Ks were found to be able to persist longer in circulation and activate various downstream effector cells. After intravenous injection, they resulted in higher levels of IL-12p70 in the circulation and lower M-MDSC infiltrates in the tumor microenvironment. Such activities were different from those of CpG ODNs without PEGylation, suggesting different PK-PD profiles systemically and locally.

CONCLUSIONS

Our data support the development of CpG-PEGs as a new therapeutic agent that can be systemically administered to modulate immune responses and the microenvironment in tumor tissues.

Albumin/vaccine nanocomplexes that assemble in vivo for combination cancer immunotherapy

Subunit vaccines have been investigated in over 1000 clinical trials of cancer immunotherapy, but have shown limited efficacy. Nanovaccines may improve efficacy but have rarely been clinically translated. By conjugating molecular vaccines with Evans blue (EB) into albumin-binding vaccines (AlbiVax), here we develop clinically promising albumin/AlbiVax nanocomplexes that self-assemble in vivo from AlbiVax and endogenous albumin for efficient vaccine delivery and potent cancer immunotherapy. PET pharmacoimaging, super-resolution microscopies, and flow cytometry reveal almost 100-fold more efficient co-delivery of CpG and antigens (Ags) to lymph nodes (LNs) by albumin/AlbiVax than benchmark incomplete Freund's adjuvant (IFA). Albumin/AlbiVax elicits ~10 times more frequent peripheral antigen-specific CD8⁺ cytotoxic T lymphocytes with immune memory than IFA-emulsifying vaccines. Albumin/AlbiVax specifically inhibits progression of established primary or metastatic EG7.OVA, B16F10, and MC38 tumors; combination with anti-PD-1 and/or Abraxane further potentiates immunotherapy and eradicates most MC38 tumors. Albumin/AlbiVax nanocomplexes are thus a robust platform for combination cancer immunotherapy.

Immunostimulatory Properties of Lipid Modified CpG Oligonucleotides

Innate immune responses recognizing pathogen associated molecular patterns play important roles in adaptive immunity. As such, ligands which mimic the conserved products of microbial and activate innate immunity are widely used as adjuvants for vaccines. Synthetic single strand oligodeoxynucleotides (ODNs) containing unmethylated cytosine-guanine (CpG) motifs which bind Toll-like receptor 9 (TLR9) are powerful molecular adjuvants, potentiating both humoral and cellular responses. However, CpG ODN's in vitro potency has not been translated to in vivo settings primarily due to issues associated with delivery and toxicity. A major challenge in clinical application of CpG ODN is the efficient delivery to lymph nodes, the anatomic sites where all the immune responses are initiated. Targeting CpG to the key antigen presenting cells (APC) is essential for its application as a vaccine adjuvant, as it not only enhances CpG's efficacy, but also greatly reduces the systemic toxicity. We recently discovered an "albumin-hitchhiking" approach by which CpG ODNs were conjugated to a lipophilic lipid tail and follow subcutaneous injection, accumulated in lymph nodes by binding and transporting with endogenous albumin. This molecular approach targets CpG to antigen presenting cells in the draining lymph nodes via an endogenous albumin-mediated mechanism and simultaneously improves both the efficacy and safety of CpG as a vaccine adjuvant. Since CpG ODNs can be divided into structurally distinct classes, and each class of CpG ODN activates different types of immune cells and triggers different types of immunostimulatory activities, it is important to thoroughly evaluate the efficacy of this "albumin-hitchhiking" strategy in each class of CpG. Here we compare the immunostimulatory activities of three classes of lipid conjugated CpG ODNs in vitro and in vivo. Three representative sequences of lipid modified CpG ODNs were synthesized and their stimulatory effects as a vaccine adjuvant were evaluated. Our results showed that in vitro, lipid modified class A CpG exhibited enhanced stimulatory activities toward TLR transfected reporter cells or bone-marrow derived dendritic cells, whereas lipid-modification of class B or C CpG reduces the activation of TLR9 by 2-3 fold, as compared with unmodified class B and class C CpG, respectively. However, in vivo coadministration of ovalbumin (OVA) protein antigen mixed with lipid-conjugated class B or C CpG ODNs, but not class A CpGs induced dramatically increased OVA-specific humoral and cytotoxic CD8⁺ T cells responses compared with OVA mixed with unmodified CpGs. Further, lipid-modification greatly reduces the toxicity associated with CpG by minimizing the systemic dissemination. Taken together, these results demonstrated that amphiphilic modification of three classes of CpG motifs differentially affected and modulated the immunostimulatory activities in vitro and in vivo. Our study highlights the importance of in vivo lymph node targeting of CpG ODNs in fulfilling their use as vaccine adjuvants, providing implications for the rational design of molecular adjuvant for subunit vaccines.

Comparative Study of 5'- and 3'-Linked CpG-Antigen Conjugates for the Induction of Cellular Immune Responses

Conjugation of CpG to an antigen induces a stronger immune response compared to that of the mixture. This study compares the in vitro immunostimulatory activity of CpG conjugated via either its 5' or 3' end to the model antigen ovalbumin (OVA). CpG modified with an amine at either the 5' or 3' end was conjugated to OVA via a stable bis-aryl hydrazone bond. Similar levels of CpG conjugation to OVA were observed for both conjugates on the basis of the absorbance at 360 nm for the formation of the bis-aryl hydrazone bond, which determined 2.8 ± 0.3 CpGs linked per OVA. Both the 5' and 3' CpG-OVA conjugates had similar size-exclusion chromatography elution profiles. The immunostimulatory properties of the conjugates were determined by dendritic cells (DCs) and T-cells isolated from mice. The activation of DCs was determined by the upregulation of activation markers CD86 and CD40. T-cells were co-cultured with stimulated DCs, and the immunogenicity was determined by measuring T-cell proliferation and interferon γ production. Both the CpG 5'- and 3'-linked conjugates induced the same level (p > 0.5) of DC activation markers, which were significantly higher than those of the untreated control. Similarly, T-cell assays showed no significant difference (p > 0.5) between the 5' and 3' conjugates with respect to T-cell proliferation and interferon γ production. The 5' and 3' conjugates induced T-cell activation significantly higher than the mixture of CpG and OVA. This study showed that the end at which CpG is conjugated to an antigen has no influence on the generation of a T-cell-based immune response in vitro.

On-Resin Conjugation of Diene-Polyamides and Maleimides via Diels-Alder Cycloaddition

The reaction between maleimides and resin-linked diene-polyamides allows the latter to be used in the preparation of conjugates. Conjugation takes place by reacting the insoluble, hydrophobic diene component either with water-soluble dienophiles or with dienophiles requiring mixtures of water and organic solvents. Experimental conditions can be adjusted to furnish the target conjugate in good yield with no need of adding large excesses of soluble reagent. In case protected maleimides are used, maleimide deprotection and Diels-Alder cycloaddition can be simultaneously carried out to render conjugates with different linking positions. On-resin conjugation is followed by an acidic treatment that removes the polyamide protecting groups with no harm to the cycloadduct, in contrast with the unreacted diene that is indeed degraded under these conditions. Cycloadducts incorporating suitable functional groups can undergo subsequent additional conjugation reactions in solution to furnish double conjugates.

Strategy for Designing a Synthetic Tumor Vaccine: Multi-Component, Multivalency and Antigen Modification

Synthetic tumor vaccines have been proven to be promising for cancer immunotherapy. However, the limitation of the specificity and efficiency of the synthetic tumor vaccines need further improvements. To overcome these difficulties, additional tumor-associated targets need to be identified, and optimized structural designs of vaccines need to be elaborated. In this review, we summarized the main strategies pursued in the design of synthetic tumor vaccines, such as multi-component, multivalency, antigen modification and other possible ways to improve the efficiency of synthetic tumor vaccines.

Orthogonal protection of peptides and peptoids for cyclization by the thiol-ene reaction and conjugation

Cyclic peptides and peptoids were prepared using the thiol-ene Michael-type reaction. The linear precursors were provided with additional functional groups allowing for subsequent conjugation: an orthogonally protected thiol, a protected maleimide, or an alkyne. The functional group for conjugation was placed either within the cycle or in an external position. The click reactions employed for conjugation with suitably derivatized nucleoside or oligonucleotides were either cycloadditions (Diels-Alder, Cu(I)-catalyzed azide-alkyne) or the same Michael-type reaction as for cyclization.

DNA-polymer conjugates for immune stimulation through Toll-like receptor 9 mediated pathways

Oligodeoxynucleotides (ODNs) containing unmethylated CpG dinucleotide motifs are agonists of Toll-like receptor 9 and are currently being investigated for use as vaccine adjuvants through the promotion of type I immunity. Several classes of ODN have been developed which differ in their propensity to aggregate, which in turn alters cytokine profiles and cellular subsets activated. Although aggregation state is correlated with the change in cytokine response, it is unknown if this results from a change in the number of ODNs available for binding and/or the possible engagement of multiple TLR9 molecules. Here, we examined the role of ligand valency on the activation of TLR9 through the synthesis of ODN-poly(acrylic acid) (PAA) conjugates. The compositions and size of the conjugates were characterized by UV-vis spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography and dynamic light scattering. Enzyme-linked immunosorbent assays of cytokine secretion by murine-like macrophages indicate that these ODN-PAA polymer conjugates show enhanced immunostimulation at 100-fold lower concentrations than those required for ODN alone, for both TNF-α and IL-6 release, and are more potent than any other previously reported multivalent ODN constructs. Increasing valency was shown to significantly enhance cytokine expression, particularly for IL-6. Knockdown by siRNA demonstrates that these polymer conjugates are specific to TLR9. Our results define valency as a critical design parameter and polymer conjugation as an advantageous strategy for producing ODN immunomodulatory agents.

Nanoparticle conjugation of CpG enhances adjuvancy for cellular immunity and memory recall at low dose

In subunit vaccines, strong CD8(+) T-cell responses are desired, yet they are elusive at reasonable adjuvant doses. We show that targeting adjuvant to the lymph node (LN) via ultrasmall polymeric nanoparticles (NPs), which rapidly drain to the LN after intradermal injection, greatly enhances adjuvant efficacy at low doses. Coupling CpG-B or CpG-C oligonucleotides to NPs led to better dual-targeting of adjuvant and antigen (codelivered on separate NPs) in cross-presenting dendritic cells compared with free adjuvant. This led to enhanced dendritic cell maturation and T helper 1 (Th1)-cytokine secretion, in turn driving stronger effector CD8(+) T-cell activation with enhanced cytolytic profiles and, importantly, more powerful memory recall. With only 4 μg CpG, NP-CpG-B could substantially protect mice from syngeneic tumor challenge, even after 4 mo of vaccination, compared with free CpG-B. Together, these results show that nanocarriers can enhance vaccine efficacy at a low adjuvant dose for inducing potent and long-lived cellular immunity.

Immune-Stimulatory Dinucleotide at the 5'-End of Oligodeoxynucleotides Is Critical for TLR9-Mediated Immune Responses

Oligodeoxynucleotides (ODNs) containing a CpG or certain synthetic dinucleotides, referred to as immune-stimulatory dinucleotides, induce Toll-like receptor 9 (TLR9)-mediated immune responses. Chemical modifications such as 2'-O-methylribonucleotides incorporated adjacent to the immune-stimulatory dinucleotide on the 5'-side abrogate TLR9-mediated immune responses. In this study, we evaluated the effect of the location of immune-stimulatory dinucleotides in ODNs on TLR9-mediated immune responses. We designed and synthesized ODNs with two immune-stimulatory dinucleotides, one placed toward the 5'-end region and the other toward the 3'-end region, incorporated 2'-O-methylribonucleotides selectively preceding the 5'- or 3'-immune-stimulatory dinucleotide or both, and studied TLR9-mediated immune responses of these compounds in cell-based assays and in vivo in mice. These studies showed that an immune-stimulatory dinucleotide located closer to the 5'-end is critical for and dictates TLR9-mediated immune responses. These studies provide insights for the use of ODNs when employed as TLR9 agonists and antagonists or antisense agents.

Design, synthesis and biological evaluation of novel antagonist compounds of Toll-like receptors 7, 8 and 9

Oligonucleotides containing an immune-stimulatory motif and an immune-regulatory motif act as antagonists of Toll-like receptor (TLR)7 and TLR9. In the present study, we designed and synthesized oligonucleotide-based antagonists of TLR7, 8 and 9 containing a 7-deaza-dG or arabino-G modification in the immune-stimulatory motif and 2′-O-methylribonucleotides as the immune-regulatory motif. We evaluated the biological properties of these novel synthetic oligoribonucleotides as antagonists of TLRs 7, 8 and 9 in murine and human cell-based assays and in vivo in mice and non-human primates. In HEK293, mouse and human cell-based assays, the antagonist compounds inhibited signaling pathways and production of a broad range of cytokines, including tumour necrosis factor alpha (TNF-α), interleukin (IL)-12, IL-6, interferon (IFN)-α, IL-1β and interferon gamma-induced protein (IP)-10, mediated by TLR7, 8 and 9. In vivo in mice, the antagonist compounds inhibited TLR7- and TLR9-mediated cytokine induction in a dose- and time-dependent fashion. Peripheral blood mononuclear cells (PBMCs) obtained from antagonist compound-treated monkeys secreted lower levels of TLR7-, 8- and 9-mediated cytokines than did PBMCs taken before antagonist administration. The antagonist compounds described herein provide novel agents for the potential treatment of autoimmune and inflammatory diseases.

Easy introduction of maleimides at different positions of oligonucleotide chains for conjugation purposes

[2,5-Dimethylfuran]-protected maleimides were placed at both internal positions and the 3'-end of oligonucleotides making use of solid-phase synthesis procedures. A new phosphoramidite derivative and a new solid support incorporating the protected maleimide moiety were prepared for this purpose. In all cases maleimide deprotection (retro-Diels-Alder reaction) followed by reaction with thiol-containing compounds afforded the target conjugate.

Conjugation reactions involving maleimides and phosphorothioate oligonucleotides

Phosphorothioate diester oligonucleotides proved to be fully compatible with maleimides in the context of two different conjugation reactions: (a) reaction of (5')diene-[phosphorothioate oligonucleotides] with maleimido-containing compounds to afford the Diels-Alder cycloadduct; (b) conjugation of (5')maleimido-[phosphorothioate oligonucleotides] with thiol-containing compounds. No evidence of reaction between phosphorothioate diesters and maleimides was found in any of these processes. Importantly, in the preparation of (5')maleimido-[phosphorothioate oligonucleotides] from [protected maleimido]-[phosphorothioate oligonucleotides], which requires the maleimide to be deprotected by retro-Diels-Alder reaction (heating for 3-4 h in toluene at 90 °C), no addition of phosphorothioate diester to the maleimide was found either. Finally, maleimide-[phosphorothioate monoester] conjugation was also explored for comparison purposes.

Targeted delivery of CpG ODN to CD32 on human and monkey plasmacytoid dendritic cells augments IFNα secretion

Atopic diseases are characterized by the presence of Th2 cells. Recent studies, in mice and man, demonstrated that allergen-specific Th2 responses can be shifted to Th0/Th1 responses. Plasmacytoid dendritic cells (pDCs) produce large amounts of type I interferons (IFNs) after stimulation of Toll Like Receptor 9 (TLR9) and are likely to play an important role in the reorientation of these Th2 cells. The expression of CD32a on the cell surface of pDCs makes this cell type attractive for targeted delivery of antigen and TLR agonists to revert Th2 responses. Therefore we sought to determine the efficacy of targeted delivery of CpG-C ODN to CD32a on the ability of human and monkey pDCs to secrete inflammatory cytokines. Here we demonstrate that targeted delivery of 3'-biotinylated CpG-C to CD32a on pDC induced phenotypical maturation as determined by CD80, CD83 and CD86 expression. Furthermore, targeting both monkey and human pDCs strongly augmented the secretion of IFNα compared to the delivery of CpG-C in an untargeted fashion (p<0.001). TLR9 induced activation hampers the ability of human pDCs to internalize CD32a. Therefore we opted for targeted delivery of CpG-ODNs to CD32a, which reduces the risk of undesired side effects of systemic TLR treatment and in addition delivers a superior signal for the activation of pDCs. This approach opens new treatment principles for allergic patients.

TLR9 agonist protects mice from radiation-induced gastrointestinal syndrome

Purpose

Radiation-induced gastrointestinal syndrome (RIGS) is due to the clonogenic loss of crypt cells and villi depopulation, resulting in disruption of mucosal barrier, bacterial invasion, inflammation and sepsis. Intestinal macrophages could recognize invading bacterial DNA via TLR9 receptors and transmit regenerative signals to the neighboring crypt. We therefore investigated whether systemic administration of designer TLR9 agonist could ameliorate RIGS by activating TLR9.

Methods and Materials

Male C57Bl6 mice were distributed in four experimental cohorts, whole body irradiation (WBI) (8.4–10.4 Gy), TLR9 agonist (1 mg/kg s.c.), 1 h pre- or post-WBI and TLR9 agonist+WBI+iMyd88 (pretreatment with inhibitory peptide against Myd88). Animals were observed for survival and intestine was harvested for histological analysis. BALB/c mice with CT26 colon tumors in abdominal wall were irradiated with 14 Gy single dose of whole abdominal irradiation (AIR) for tumor growth study.

Results

Mice receiving pre-WBI TLR9 agonist demonstrated improvement of survival after 10.4 Gy (p<0.03), 9.4 Gy (p<0.008) and 8.4 Gy (p<0.002) of WBI, compared to untreated or iMyd88-treated controls. Post-WBI TLR9 agonist mitigates up to 8.4 Gy WBI (p<0.01). Histological analysis and xylose absorption test demonstrated significant structural and functional restitution of the intestine in WBI+TLR9 agonist cohorts. Although, AIR reduced tumor growth, all animals died within 12 days from RIGS. TLR9 agonist improved the survival of mice beyond 28 days post-AIR (p<0.008) with significant reduction of tumor growth (p<0.0001).

Conclusions

TLR9 agonist treatment could serve both as a prophylactic or mitigating agent against acute radiation syndrome and also as an adjuvant therapy to increase the therapeutic ratio of abdominal Radiation Therapy for Gastro Intestinal malignancies.

Nuclease-resistant immunostimulatory phosphodiester CpG oligodeoxynucleotides as human Toll-like receptor 9 agonists

Background

Unmethylated cytosine-guanine (CpG) motif-containing oligodeoxynucleotides (ODNs) have been well characterized as agonists of Toll-like receptor 9 (TLR9). ODNs with a phosphorothioate (PTO) backbone have been studied as TLR9 agonists since natural ODNs with a phosphodiester (PD) backbone are easily degraded by a serum nuclease, which makes them problematic for therapeutic applications. However, ODNs with a PTO backbone have been shown to have undesirable side effects. Thus, our goal was to develop nuclease-resistant, PD ODNs that are effective as human TLR9 (hTLR9) agonists.

Results

The sequence of ODN2006, a CpG ODN that acts as an hTLR9 agonist, was used as the basic CpG ODN material. The 3'-end modification of ODN2006 with a PD backbone (PD-ODN2006) improved its potential as an hTLR9 agonist because of increased resistance to nucleolytic degradation. Moreover, 3'-end modification with oligonucleotides showed higher induction than modification with biotin, FITC, and amino groups. Further, enhancement of hTLR9 activity was found to be dependent on the number of CpG core motifs (GTCGTT) in the PD ODN containing the 3'-end oligonucleotides. In particular, ODN sequences consisting of two to three linked ODN2006 sequences with a PD backbone (e.g., PD-ODN2006-2006 and PD-ODN2006-2006-2006) acted as effective agonists of hTLR9 even at lower concentrations.

Conclusions

This study showed that PD-ODN2006-2006 and PD-ODN-2006-2006-2006 can be used as potentially safe agonists for hTLR9 activation instead of CpG ODNs with a PTO backbone. We propose these CpG ODNs consisting of only a PD backbone as a novel class of CpG ODN.

Synthesis, purification, and characterization of immune-modulatory oligodeoxynucleotides that act as agonists of Toll-like receptor 9

Methods and protocols for automated synthesis and purification of immune modulatory oligonucleotides (IMOs), a novel class of Toll-like receptor 9 (TLR9) agonists, are described. IMOs containing two short identical sequences of 11-mers with phosphorothioate linkages can be synthesized in parallel synthetic strategy. A C3-linker that mimics the natural inter-nucleotide distance was commonly used for joining the two segments of IMOs. NittoPhase solid support bearing a symmetrical C3-linker (glycerol) and nucleoside-β-cyanoethyl-N,N-diisopropylphosphoramidites were used for IMO synthesis. The parallel synthesis was carried out in a 3'→ 5' direction with removal of the final dimethoxytrityl (DMT) protecting group. After synthesis, the IMO was cleaved and deprotected by treating with aqueous ammonia. The product was purified on anion-exchange HPLC, desalted, lyophilized, and characterized by anion-exchange HPLC, capillary gel electrophoresis, polyacrylamide gel electrophoresis, and MALDI-TOF mass spectral analysis.

Impact of nature and length of linker incorporated in agonists on toll-like receptor 9-mediated immune responses

Oligodeoxynucleotides containing unmethylated CpG motifs act as ligands of Toll-like receptor 9 (TLR9). We previously reported a novel class of TLR9 agonists, referred to as immune-modulatory oligonucleotides (IMOs), in which two 11-mers of the same sequence are attached via their 3'-ends through a 1,2,3-propanetriol linker and contain a synthetic immune-stimulatory motif, Cp7-deaza-dG. In the present study, we have examined the impact of length, nature, and stereochemistry of the linker incorporated in agonists for TLR9 activation. The new linkers studied include (S)-(-)-1,2,4-butanetriol, 1,3,5-pentanetriol, cis,cis-1,3,5-cyclohexanetriol, cis,trans-1,3,5-cyclohexanetriol, 1,3,5-tris(2-hydroxyethyl)isocyanurate, tetraethyleneglycol, and hexaethyleneglycol in place of 1,2,3-propanetriol linker. Agonists with various linkers are studied for TLR9-mediated immune responses in HEK293 cells, human cell-based assays, and in vivo in mice. Results of these studies suggest that C3-C5 linkers, 1,2,3-propanetriol, (S)-(-)-1,2,4-butanetriol, or 1,3,5-pentanetriol, are optimal for stimulation of TLR9-mediated immune responses. Rigid C3 linkers with different stereochemistry have little effect on immune stimulation, while linkers longer than C5 reduced TLR9-mediated immune stimulation.