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

Immunogenicity of a reduced-dose whole killed rabies vaccine is significantly enhanced by ISCOMATRIX™ adjuvant, Merck amorphous aluminum hydroxylphosphate sulfate (MAA) or a synthetic TLR9 agonist in rhesus macaques

There is a need for novel rabies vaccines suitable for short course, pre- and post-exposure prophylactic regimens which require reduced doses of antigen to address the current worldwide supply issue. We evaluated in rhesus macaques the immunogenicity of a quarter-dose of a standard rabies vaccine formulated with Merck's amorphous aluminum hydroxylphosphate sulfate adjuvant, the saponin-based ISCOMATRIX™ adjuvant, or a synthetic TLR9 agonist. All adjuvants significantly increased the magnitude and durability of the humoral immune response as measured by rapid fluorescent focus inhibition test (RFFIT). Several three-dose vaccine regimens resulted in adequate neutralizing antibody of ≥ 0.5 IU/ml earlier than the critical day seven post the first dose. Rabies vaccine with ISCOMATRIX™ adjuvant given at days 0 and 3 resulted in neutralizing antibody titers which developed faster and were up to one log10 higher compared to WHO-recommended intramuscular and intradermal regimens and furthermore, passive administration of human rabies immunoglobulin did not interfere with immunogenicity of this reduced dose, short course vaccine regimen. Adjuvantation of whole-killed rabies vaccine for intramuscular injection may therefore be a viable alternative to intradermal application of non-adjuvanted vaccine for both pre- and post-exposure regimens.

Solid-phase supports for oligonucleotide synthesis

This unit attempts to provide a reasonably complete inventory of over 280 solid supports available to oligonucleotide chemists for preparation of natural and 3'-modified oligonucleotides. Emphasis is placed on non-nucleosidic solid supports. The relationship between the structural features of linkers and their behavior in oligonucleotide synthesis and deprotection is discussed wherever the relevant observations are available.

Sequential induction of type I and II interferons mediates a long-lasting gene induction in the liver in response to a novel toll-like receptor 9 agonist

BACKGROUND & AIMS

The toll-like receptor 9 (TLR9) agonist IMO-2125 is currently evaluated in clinical trials for chronic hepatitis C therapy. The aim of this study was to investigate the in vivo mode of action of a closely related compound, referred to as immunomodulatory oligonucleotide (IMO).

METHODS

We analyzed the Jak-STAT pathway activation and induction of interferon-stimulated genes in the liver of wild type, interferon-α/β receptor-deficient and interferon-γ-deficient mice, after administration of IMO.

RESULTS

IMO induced a prolonged activation of the Jak-STAT pathway and upregulation of interferon-stimulated genes in the mouse liver. Contrary to the response observed after interferon-α injection, the signalling induced by IMO was not abrogated following repeated administration. At early time points after IMO injection, STAT1 phosphorylation and interferon-stimulated gene induction required a functional interferon-α/β receptor, whereas at the later time points, the activation was type I interferon-independent. Microarray analysis revealed that IMO induced a broad transcriptional response in the mouse liver. This included upregulation of cytokine and chemokine genes responsible for recruitment of IFN-γ producers, such as T cells and natural killer cells. Interferon-γ-deficient mice showed a transient response to IMO, demonstrating the central role of interferon-γ in sustained activation of Jak-STAT pathway by IMO.

CONCLUSIONS

The bimodal kinetics of response to IMO in the mouse liver are driven by the sequential endogenous production of type I and II interferons. The lack of refractoriness to IMO, combined with the long-lasting induction of interferon-stimulated genes, reveals a favourable pharmacodynamics profile of this novel TLR9 agonist for the treatment of chronic viral hepatitis.

Antiviral applications of Toll-like receptor agonists

In the past, antiviral research has focused mainly on viral targets. As the search for effective and differentiated antiviral therapies continues, cellular targets are becoming more common, bringing with them a variety of challenges and concerns. Toll-like receptors (TLRs) provide a unique mechanism to induce an antiviral state in the host. In this review we introduce TLRs as targets for the pharmaceutical industry, including how they signal and thereby induce an antiviral state through the production of type I interferons. We examine how TLRs are being therapeutically targeted and discuss several clinically precedented agents for which efficacy and safety data are available. We describe some of the chemistries that have been applied to both small molecule and large molecule leads to tune agonist potency, and offer a differentiated safety profile through targeting certain compartments such as the gut or the lung, thereby limiting systemic drug exposure and affecting systemic cytokine levels. The application of low-dose agonists of TLRs as vaccine adjuvants or immunoprotective agents is also presented. Some of the challenges presented by this approach are then discussed, including viral evasion strategies and mechanism-linked inflammatory cytokine induction.

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.