Vibrational spectroscopy coupled with machine learning sheds light on the cellular effects induced by rationally designed TLR4 agonists.

In this work, we present the potential of Fourier transform infrared (FTIR) microspectroscopy to compare on whole cells, in an unbiased and untargeted way, the capacity of bacterial lipopolysaccharide (LPS) and two rationally designed molecules (FP20 and FP20Rha) to activate molecular circuits of innate immunity. These compounds are important drug hits in the development of vaccine adjuvants and tumor immunotherapeutics. The biological assays indicated that FP20Rha was more potent than FP20 in inducing cytokine production in cells and in stimulating IgG antibody production post-vaccination in mice. Accordingly, the overall significant IR spectral changes induced by the treatment with LPS and FP20Rha were similar, lipids and glycans signals being the most diagnostic, while the effect of the less potent molecule FP20 on cells resulted to be closer to control untreated cells. We propose here the use of FTIR spectroscopy supported by artificial intelligence (AI) to achieve a more holistic understanding of the cell response to new drug candidates while screening them in cells.

Novel TLR4-Activating Vaccine Adjuvant Enhances the Production of Enterococcus faecium-binding Antibodies.

Vaccines are one of the greatest achievements of modern medicine. Due to their safer profile, the latest investigations usually focus on subunit vaccines. However, the active component often needs to be coupled with an adjuvant to be effective and properly trigger an immune response. We are developing a new synthetic monosaccharide-based TLR4 agonist, such as glucosamine-derived compounds FP18 and FP20, as a potential vaccine adjuvant. In this study, we present a new FP20 derivative, FP20Hmp, with a hydroxylated ester linked to the glucosamine core. We show that the modification introduced improves the activity of the adjuvant and its solubility. This study presents the synthesis of FP20Hmp, its in vitro characterization, and in vivo activity while coupled with the ovalbumin antigen or in formulation with an enterococcal antigen. We show that FP20Hmp enables increased production of antigen-specific antibodies that bind to the whole bacterium.

Overcoming Challenges in Chemical Glycosylation to Achieve Innovative Vaccine Adjuvants Possessing Enhanced TLR4 Activity.

Lipopolysaccharide (LPS) mimicry leading to toll-like receptor 4 (TLR4) active compounds has been so far based mainly on reproducing the lipid A portion of LPS. Our work led to a series of structurally simplified synthetic TLR4 agonists in preclinical development as vaccine adjuvants called FPs. FPs bind MD2/TLR4 similarly to lipid A, inserting the lipid chains in the MD2 lipophilic cavity. A strategy to improve FPs' target affinity is introducing a monosaccharide unit in C6, mimicking the first sugar of the LPS core. We therefore designed a panel of FP derivatives bearing different monosaccharides in C6. We report here the synthesis and optimization of FPs' C6 glycosylation, which presented unique challenges and limitations. The biological activity of glycosylated FP compounds was preliminarily assessed in vitro in HEK-Blue cells. The new molecules showed a higher potency in stimulating TLR4 activation when compared to the parent molecule while maintaining TLR4 selectivity.

Emerging Extracellular Molecular Targets for Innovative Pharmacological Approaches to Resistant Mtb Infection.

Emerging pharmacological strategies that target major virulence factors of antibiotic-resistant Mycobacterium tuberculosis (Mtb) are presented and discussed. This review is divided into three parts corresponding to structures and functions important for Mtb pathogenicity: the cell wall, the lipoarabinomannan, and the secretory proteins. Within the cell wall, we further focus on three biopolymeric sub-components: mycolic acids, arabinogalactan, and peptidoglycan. We present a comprehensive overview of drugs and drug candidates that target cell walls, envelopes, and secretory systems. An understanding at a molecular level of Mtb pathogenesis is provided, and potential future directions in therapeutic strategies are suggested to access new drugs to combat the growing global threat of antibiotic-resistant Mtb infection.

New Glucosamine-Based TLR4 Agonists: Design, Synthesis, Mechanism of Action, and In Vivo Activity as Vaccine Adjuvants.

We disclose here a panel of small-molecule TLR4 agonists (the FP20 series) whose structure is derived from previously developed TLR4 ligands (FP18 series). The new molecules have increased chemical stability and a shorter, more efficient, and scalable synthesis. The FP20 series showed selective activity as TLR4 agonists with a potency similar to FP18. Interestingly, despite the chemical similarity with the FP18 series, FP20 showed a different mechanism of action and immunofluorescence microscopy showed no NF-κB nor p-IRF-3 nuclear translocation but rather MAPK and NLRP3-dependent inflammasome activation. The computational studies related a 3D shape of FP20 series with agonist binding properties inside the MD-2 pocket. FP20 displayed a CMC value lower than 5 µM in water, and small unilamellar vesicle (SUV) formation was observed in the biological activity concentration range. FP20 showed no toxicity in mouse vaccination experiments with OVA antigen and induced IgG production, thus indicating a promising adjuvant activity.