Use of Therapeutic Pathogen Recognition Receptor Ligands for Osteo-Immunomodulation

Therapeutic pathogen recognition receptor (PRR) ligands are reaching clinical practice following their ability to skew the immune response in a specific direction. We investigated the effects of various therapeutic PRR ligands on bone cell differentiation and inflammation. Following stimulation, alkaline phosphatase (ALP) activity (Day 10), osteocalcin, osteonectin expression (Day 14), and calcium deposition (Day 21) were quantified in bone marrow-derived human mesenchymal stem cells (hMSCs). The osteoclastogenic response was determined by measuring tartrate-resistant acid phosphate (TRAP) activity in human monocytes. TNF-α, IL-6, IL-8, and IL-10 expressions were measured by enzyme-linked immunosorbent assay as an indicator of the ligands’ inflammatory properties. We found that nucleic acid-based ligands Poly(I:C) and CpG ODN C increased early ALP activity in hMSCs by 4-fold without affecting osteoclast formation. These ligands did not enhance expression of the other, late osteogenic markers. MPLA, Curdlan, and Pam3CSK4 did not affect osteogenic differentiation, but inhibited TRAP activity in monocytes, which was associated with increased expression of all measured cytokines. Nucleic acid-based ligands are identified as the most promising osteo-immunomodulators, as they favor early osteogenic differentiation without inducing an exaggerated immune-cell mediated response or interfering in osteoclastogenesis and thus can be potentially harnessed for multifunctional coatings for bone biomaterials.

Ortho -Substituted lipidated Brartemicin derivative shows promising Mincle-mediated adjuvant activity

This journal is © The Royal Society of Chemistry. The macrophage inducible C-type lectin (Mincle) is a pathogen recognition receptor (PRR) that is a promising target for the development of Th1-polarising vaccine adjuvants. We recently reported on the synthesis and evaluation of lipidated Brartemicin analogues that showed Mincle agonist activity, with our lead agonist exhibiting potent Th1 adjuvant activity that was greater than that of trehalose dibehenate (TDB). Herein, we report on the efficient synthesis and subsequent biological evaluation of additional lipidated Brartemicin analogues that were designed to determine the structural requirements for optimal Mincle signalling. While all the Brartemicin analogues retained their ability to signal through Mincle and induce a functional response, the o-substituted and m,m-disubstituted derivatives (5a and 5d, respectively) induced a potent inflammatory response when using cells of both murine and human origin, with this response being the greatest observed thus far. As the inflammatory response elicited by 5a was slightly better than that induced by 5d, our findings point to o-substituted Brartemicin analogues as the preferred scaffold for further adjuvant development.

Ortho -Substituted lipidated Brartemicin derivative shows promising Mincle-mediated adjuvant activity

This journal is © The Royal Society of Chemistry. The macrophage inducible C-type lectin (Mincle) is a pathogen recognition receptor (PRR) that is a promising target for the development of Th1-polarising vaccine adjuvants. We recently reported on the synthesis and evaluation of lipidated Brartemicin analogues that showed Mincle agonist activity, with our lead agonist exhibiting potent Th1 adjuvant activity that was greater than that of trehalose dibehenate (TDB). Herein, we report on the efficient synthesis and subsequent biological evaluation of additional lipidated Brartemicin analogues that were designed to determine the structural requirements for optimal Mincle signalling. While all the Brartemicin analogues retained their ability to signal through Mincle and induce a functional response, the o-substituted and m,m-disubstituted derivatives (5a and 5d, respectively) induced a potent inflammatory response when using cells of both murine and human origin, with this response being the greatest observed thus far. As the inflammatory response elicited by 5a was slightly better than that induced by 5d, our findings point to o-substituted Brartemicin analogues as the preferred scaffold for further adjuvant development.

Advances in Desmuramyl Peptide Research

Immune adjuvants are added to vaccines in order to enhance the immune response to an antigen. Muramyl dipeptide, N-acetylmuramyl-L-alanyl-D-isoglutamine, is the smallest structural unit of peptidoglycans showing the immunostimulating activity. Muramyl dipeptide analogues without the hydrophilic N-acetylmuramyl moiety are called desmuramyl peptides. Here, we provide review of desmuramyl peptides which were synthesized in order to improve the pharmacological properties of parent muramyl dipeptide, including our results regarding adamantane containing derivatives. Approach for future design of novel immunostimulators based on multiple pathogen recognition receptor activation was also considered.

Cellular polarity asymmetrically functionalizes pathogen recognition receptor-mediated intrinsic immune response in human intestinal epithelium cells

SummaryIntestinal epithelial cells (IECs) act as a physical barrier separating the commensal-containing intestinal tract from the sterile interior. These cells have found a complex balance allowing them to be prepared for pathogen attacks while still tolerating the presence of bacteria/viral stimuli present in the lumen of the gut. Using primary human IECs, we probed the mechanisms, which allow for such a tolerance. We discovered that viral infection emanating from the basolateral side of IECs elicited a stronger intrinsic immune response as compared to lumenal apical infection. We determined that this asymmetric immune response was driven by the clathrin-sorting adapter AP-1B which mediates the polarized sorting of Toll-like receptor 3 (TLR3) toward the basolateral side of IECs. Mice and human IECs lacking AP-1B showed an exacerbated immune response following apical stimulation. Together these results suggest a model where the cellular polarity program plays an integral role in the ability of IECs to partially tolerate apical commensals while remaining fully responsive against invasive basolateral pathogens.

The Interplay between Human Cytomegalovirus and Pathogen Recognition Receptor Signaling

The cellular antiviral innate immune response is triggered upon recognition of specific viral components by a set of the host’s cytoplasmic or membrane-bound receptors. This interaction induces specific signaling cascades that culminate with the production of interferons and the expression of interferon-stimulated genes and pro-inflammatory cytokines that act as antiviral factors, suppressing viral replication and restricting infection. Here, we review and discuss the different mechanisms by which each of these receptors is able to recognize and signal infection by the human cytomegalovirus (HCMV), an important human pathogen mainly associated with severe brain defects in newborns and disabilities in immunocompromised individuals. We further present and discuss the many sophisticated strategies developed by HCMV to evade these different signaling mechanisms and counteract the cellular antiviral response, in order to support cell viability and sustain its slow replication cycle.