Acetylated Trivalent Mannobioses: Chemical Modification, Structural Elucidation, and Biological Evaluation

Mannose receptor independent uptake of transmembrane glycocluster immunostimulant TADM by macrophages

Triacedimannose (TADM) is a synthetic trivalent acetylated glycocluster comprising β-1,2-linked mannobioses that in humans induces TNF in vitro and in vivo. The purpose of this study was to analyze whether uptake of acetylated glycoclusters of such β-1,2-linked mannobioses by human macrophages is dependent on the mannose receptor (CD206) or if it is mediated by transmembrane activation. In mannose receptor blocking assays, monocyte-derived polarized macrophages were incubated with carbohydrate test-compounds and their binding to the mannose receptor was demonstrated as inhibition of FITC-Dextran binding. For 1H NMR spectroscopy, macrophages were incubated with TADM. The cells were collected at 6 and 24 h of incubation, centrifuged and washed twice with PBS. We found dose-dependent blocking of the mannose receptor in macrophage carbohydrate constructs containing free hydroxyl groups, but not by the trivalent acetylated glycocluster molecules. NMR spectroscopic analyses demonstrated that TADM was found in washed cellular pellets after 6-h co-culture, while after 24-h co-culture TADM was no more detectable, suggesting cleavage of the acetyl groups in vitro. The Type 1 immune response enhancing effects of TADM and other, stereochemically and structurally similar, trivalent acetylated glycoclusters may be due to transmembrane uptake of macrophages independent of the mannose receptor.

Immunomodulatory Synthetic Glycocluster Molecule Prevents Melanoma Growth In Vivo

Triacedimannose (TADM) is a synthetic trivalent acetylated glycocluster and a transmembrane macrophage activator independent of the mannose receptor. TADM induces Th1-type immune responses and suppresses Th2-type cytokines in acute and chronic allergic inflammation models in vivo. We, therefore, wanted to test whether TADM could also facilitate anti-tumour tissue responses similar to what has been observed for the immune checkpoint inhibitors, such as anti-PD-1 and anti-CTLA-4. A syngeneic mouse melanoma model was selected since metastatic melanoma has been successfully targeted by checkpoint inhibitors in the clinic. TADM inhibited the growth of B16 mouse melanoma tumours at levels comparable to an anti-PD-1 antibody. TADM-treated tumours encompassed significantly more apoptotic cells as measured by TUNEL staining, and interferon-gamma (IFN-γ) expression was increased in the spleens of TADM-treated mice compared to untreated controls. TADM-treated mice also demonstrated increased Ly6 C low monocytes and neutrophils in the spleens. However, TADM-treated tumours showed no discernible differences in infiltrating immune cells. TADM can alone suppress the growth of melanoma tumours. TADM likely activates M1 type macrophages, type N1 neutrophils, and CD8+ and Th1 T cells, suppressing the type 2 immune response milieu of melanoma tumour with a strong type 1 immune response.

Synthesis and biological evaluation of carbohydrate-Coumarin/vanillic acid hybrid as a promising antiparasitic agent

Leishmaniasis is caused by infection with the protozoan parasites Leishmania. It is classified as one of the most significant neglected tropical diseases. It remains a significant global public health concern. Current treatments include the use of pentavalent antimonial, amphotericin B, pentamidine, miltefosine, and paromomycin. However, several limitations such as toxicity, side effect, and resistance to these drugs of certain species are of concern. To combat this disease, effective chemotherapy is urgently required for its treatment and management. In this study, we synthesized a series of carbohydrate-coumarin/vanillic acid hybrids linked through triazole moiety via CuACC (Copper-catalysed azide-alkyne cycloaddition) reaction. These compounds were evaluated for their in vitro antiparasitic activity using MTT assay against Leishmania donovani whereas, all compounds show IC₅₀ value in the range of 65-74 μM.

A novel glycocluster molecule prevents timothy-induced allergic airway inflammation in mice

BACKGROUND

Allergen-specific immunotherapy (SIT) effectively alleviates type I allergic diseases characterized by T helper (Th)2-type immunity. Our recent studies have shown that a synthetic trivalent glycocluster, triacedimannose (TADM), suppresses the Th2-type allergic inflammation. The aim of this study was to compare TADM with two well-known adjuvants, unmethylated cytosine-phosphate-guanine oligodeoxynucleotide (CpG) and monophosphoryl lipid A (MPLA) in a grass allergen-induced chronic allergic inflammation model in mice.

METHODS

Female BALB/c mice were intranasally sensitized with 50 μL of timothy grass pollen extract (TE) twice a week for a period of 15 weeks. Therapeutic intranasal treatments were then performed once a week after the tenth intranasal TE instillation using TADM (10 or 25 μg/50 μL), CpG-ODN (20 μg/50 μL) or MPLA (2 μg/50 μL). Groups of 9-10 animals per treatment were killed 24 hours after the last timothy dosage. Blood, bronchoalveolar lavage (BAL) fluids and lung biopsies were taken for subsequent analysis.

RESULTS

When mice were repeatedly exposed to TE for 15 weeks, the number of eosinophils and lymphocytes increased in the BAL fluids. The eosinophil and lymphocyte counts decreased dose-dependently and were practically abolished in the mice treated with TADM. Treatments with MPLA or CpG significantly increased the numbers of neutrophils, while CpG nonsignificantly decreased eosinophilia compared to timothy exposure.

CONCLUSIONS

A novel synthetic glycocluster molecule inhibited the development of grass-induced eosinophilic pulmonary inflammation in mice when administrated in the airways. This compound could be a candidate to be used either as an adjuvant in SIT or as a topical anti-inflammatory treatment.

[Adjuvants]

It is estimated that only 5% of all patients who can principally benefit from specific immunotherapy (SIT) undergo this treatment. SIT represents the only curative treatment for allergic disorders and efficacy has been demonstrated with various allergens. There is an urgent demand for the development of safe preparations with enhanced efficacy achievable by only a few administrations. Adjuvants are pharmacological or immunological acting molecules modifying the specific immunological response to allergens. In vaccine technology, adjuvants are broadly used to enhance immunogenicity of highly purified antigens with low immune stimulating activity. Adjuvants may target to a retarded allergen release, a modulation of the immune system, or can be used as vector systems to transport allergens and adjuvants effectively to target cells.