From ASCA breakthrough in Crohn's disease and Candida albicans research to thirty years of investigations about their meaning in human health

Anti-Saccharomyces cerevisiae antibodies (ASCA) are human antibodies that can be detected using an enzyme-linked immunosorbent assay involving a mannose polymer (mannan) extracted from the cell wall of the yeast S. cerevisiae. The ASCA test was developed in 1993 with the aim of differentiating the serological response in two forms of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. The test, which is based on the detection of anti-oligomannosidic antibodies, has been extensively performed worldwide and there have been hundreds of publications on ASCA. The earlier studies concerned the initial diagnostic indications of ASCA and investigations then extended to many human diseases, generally in association with studies on intestinal microorganisms and the interaction of the micro-mycobiome with the immune system. The more information accumulates, the more the mystery of the meaning of ASCA deepens. Many fundamental questions remain unanswered. These questions concern the heterogeneity of ASCA, the mechanisms of their generation and persistence, the existence of self-antigens, and the relationship between ASCA and inflammation and autoimmunity. This review aims to discuss the gray areas concerning the origin of ASCA from an analysis of the literature. Structured around glycobiology and the mannosylated antigens of S. cerevisiae and Candida albicans, this review will address these questions and will try to clarify some lines of thought. The importance of the questions relating to the pathophysiological significance of ASCA goes far beyond IBD, even though these diseases remain the preferred models for their understanding.

Towards an experimental system for the examination of protein mannosylation in Actinobacteria

The actinobacterial species Cellulomonas fimi ATCC484 has long been known to secrete mannose-containing proteins, but a closer examination of glycoproteins associated with the cell has never been reported. Using ConA lectin chromatography and mass spectrometry we have surveyed the cell associated glycoproteome from C. fimi and collected detailed information on the glycosylation sites of 19 cell-associated glycoproteins. In addition, we have expressed a previously known C. fimi secreted cellulase, Celf_3184, (formerly CenA), a putative peptide prolyl-isomerase, Celf_2022, and a penicillin binding protein, Celf_0189, in the mannosylation capable host, Corynebacterium glutamicum. We found that the glycosylation machinery in C. glutamicum was able to use the recombinant C. fimi proteins as substrates and that the glycosylation matched closely that found in the native proteins when expressed in C. fimi. We are pursuing this observation as a prelude to dissecting the biosynthetic machinery and biological consequences of this protein mannosylation.

Mannose-Anchored Nano-Selenium Loaded Nanostructured Lipid Carriers of Etravirine for Delivery to HIV Reservoirs

The present investigation aims to develop and explore mannosylated lipid-based carriers to deliver an anti-HIV drug, Etravirine (TMC) and Selenium nanoparticles (SeNPs), to the HIV reservoirs via the mannose receptor. The successful mannosylation was evaluated by the change in zeta potential and lectin binding assay using fluorescence microscopy. Electron microscopy and scattering studies were employed to study the structure and surface of the nanocarrier system. The presence of selenium at the core-shell of the nanocarrier system was confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray analysis. Further, the in vitro anti-HIV1 efficacy was assessed using HIV1 infected TZM-bl cells followed by in vivo biodistribution studies to evaluate distribution to various reservoirs of HIV. The results exhibited higher effectiveness and a significant increase in the therapeutic index as against the plain drug. The confocal microscopy and flow cytometry studies exhibited the efficient uptake of the coumarin-6 tagged respective formulations. The protective effect of nano selenium toward oxidative stress was evaluated in rats, demonstrating the potential of the lipidic nanoparticle-containing selenium in mitigating oxidative stress in all the major organs. The in vivo biodistribution assessment in rats showed a 12.44, 8.05 and 9.83-fold improvement in the brain, ovary, and lymph node biodistribution, respectively as compared with plain TMC. Delivery of such a combination via mannosylated nanostructured lipid carriers could be an efficient approach for delivering drugs to reservoirs of HIV while simultaneously reducing the oxidative stress induced by such long-term therapies by co-loading Nano-Selenium.

Mannose-anchored N,N,N-trimethyl chitosan nanoparticles for pulmonary administration of etofylline

Drug delivery to lungs via pulmonary administration offers potential for the development of new drug delivery systems. Here we fabricated the etofylline (ETO) encapsulated mannose-anchored N,N,N-trimethyl chitosan nanoparticles (Mn-TMC NPs). The prominent characteristics like biocompatibility, controlled release, targeted delivery, high penetrability, enhanced physical stability, and scalability mark Mn-TMC NPs as a viable alternative to various nanoplatform technologies for effective drug delivery. Mannosylation of TMC NPs leads to the evolution of new drug delivery vehicle with gratifying characteristics, and potential benefits in efficient drug therapy. It is widely accepted that following pulmonary administration, the introduction of mannose to the surface of drug nanocarriers provide selective macrophage targeting via receptor-mediated endocytosis. The fabricated Mn-TMC NPs exhibited particle size of 223.3 nm, PDI 0.490, and ζ-potential -19.1 mV, drug-loading capacity 76.26 ± 1.2%, and encapsulation efficiency of 91.75 ± 0.88%. Sustained drug release, biodegradation studies, stability, safety, and aerodynamic behavior revealed the effectiveness of prepared nanoformulation for pulmonary administration. In addition, the in vivo pharmacokinetic studies in Wistar rat model revealed a significant improvement in therapeutic efficacy of ETO, illustrating mannosylation a promising approach for efficient therapy of airway diseases following pulmonary administration.

The role of variant alleles of the mannose-binding lectin in the inhibitor development in severe hemophilia A

INTRODUCTION

The administration of FVIII leads to inhibitors in up to 30% of patients with hemophilia A (HA), the most severe treatment complication. FVIII-mannosylation fosters the presentation of FVIII to CD4⁺-T-lymphocytes. Mannose as primary ligand for the mannose-binding lectin (MBL) activates the lectin pathway of complement. MBL2 single nucleotide polymorphisms (SNPs) lead to low peripheral MBL concentrations that may hamper the removal of mannosylated FVIII.

OBJECTIVE

Investigation of the association between the inhibitor development in hemophilia A and MBL2-SNPs.

METHODS

In a case-control study the MBL2-SNPs in exon 1 at codons 52, 54 and 57 (C, B, D-Alleles respectively) were determined in 237 patients with severe hemophilia A with and without inhibitors to FVIII (119 vs 118). The association of MBL2-SNPs and the -308 G>A TNF-α-polymorphism with the presence of inhibitors were determined.

RESULTS

In the inhibitor group higher frequencies of the B allele (codon 54) (OR: 1.77, P < 0.05) were present. Summarising the MBL2 SNPs (alleles B, C and D) as 0, the 0/0 type occurred only in the inhibitor group (frequencies: 0.08 vs 0, P = 0.003). Based on the genetic background a functional immune response phenotype was determined. 11.8% of patients with inhibitors were of the low MBL/high TNF-α phenotype vs 0.03% of the non-inhibitor patients (OR: 3.71).

CONCLUSION

Data suggest an association of MBL2-SNPs alone or combined with the 308-TNF-α polymorphism in the inhibitor development. Investigations of components of all three complement pathways are required to comprehend their individual and overall contribution to the inhibitor development in HA.

Identification and characterization of UDP-mannose in human cell lines and mouse organs: Differential distribution across brain regions and organs

Mannosylation in the endoplasmic reticulum is a key process for synthesizing various glycans. Guanosine diphosphate mannose (GDP-Man) and dolichol phosphate-mannose serve as donor substrates for mannosylation in mammals and are used in N-glycosylation, O-mannosylation, C-mannosylation, and the synthesis of glycosylphosphatidylinositol-anchor (GPI-anchor). Here, we report for the first time that low-abundant uridine diphosphate-mannose (UDP-Man), which can serve as potential donor substrate, exists in mammals. Liquid chromatography-mass spectrometry (LC-MS) analyses showed that mouse brain, especially hypothalamus and neocortex, contains higher concentrations of UDP-Man compared to other organs. In cultured human cell lines, addition of mannose in media increased UDP-Man concentrations in a dose-dependent manner. These findings indicate that in mammals the minor nucleotide sugar UDP-Man regulates glycosylation, especially mannosylation in specific organs or conditions.

Dolichol-phosphate mannose synthase depletion in zebrafish leads to dystrophic muscle with hypoglycosylated α-dystroglycan

Defective dolichol-phosphate mannose synthase (DPMS) complex is a rare cause of congenital muscular dystrophy associated with hypoglycosylation of alpha-dystroglycan (α-DG) in skeletal muscle. We used the zebrafish (Danio rerio) to model muscle abnormalities due to defects in the subunits of DPMS. The three zebrafish ortholog subunits (encoded by the dpm1, dpm2 and dpm3 genes, respectively) showed high similarity to the human proteins, and their expression displayed localization in the midbrain/hindbrain area and somites. Antisense morpholino oligonucleotides targeting each subunit were used to transiently deplete the dpm genes. The resulting morphant embryos showed early death, muscle disorganization, low DPMS complex activity, and increased levels of apoptotic nuclei, together with hypoglycosylated α-DG in muscle fibers, thus recapitulating most of the characteristics seen in patients with mutations in DPMS. Our results in zebrafish suggest that DPMS plays a role in stabilizing muscle structures and in apoptotic cell death.

Mannose-displaying fluorescent framboidal nanoparticles containing phenylboronic acid groups as a potential drug carrier for macrophage targeting

Functional polymeric nanoparticles have been used for various applications in the biomaterials field. Recently, we reported phenylboronic acid-containing nanoparticles (PBA NPs) having an unique framboidal morphology, prepared in a single-step by the aqueous dispersion polymerization of N-acryloyl-3-aminophenylboronic acid (PBAAM) in the presence of poly(ethylene glycol) acrylamide (PEGAM) as a polymerizable dispersant and N,N'-methylenebisacrylamide (MBAM) as a crosslinker. In this study, we prepared mannosylated and fluorescent PBA NPs that could be used for different applications such as drug delivery and bioimaging. Fluorescent PBA NPs were synthesized by including the fluorescent Nile Blue acrylamide monomer in the reaction mixture during the dispersion polymerization of PBAAM. By using a carboxyl group-bearing PEGAM dispersant, carboxyl group-bearing PBA NPs were prepared that were modified with mannosamine to yield mannosylated PBA NPs. Cellular uptake studies showed that the mannosylated PBA NPs were selectively taken up by murine RAW264.7 macrophages. These results show that PBA NPs allow for flexible modification with various functionalities and could therefore be a potential platform for targeted delivery of drugs to macrophages.

Divergent and convergent synthesis of polymannosylated dibranched antigenic peptide of the immunodominant epitope MBP(83-99)

Multiple antigenic peptide (MAP) systems are dendrimeric structures bearing multiple copies of identical or different peptide epitopes, and they have been demonstrated to show enhanced immunogenicity. Herein, we report the direct (divergent) and indirect (convergent) synthesis, using contemporary synthetic approaches, of a di-branched antigenic peptide (di-BAP) containing the immunodominant epitope MBP(83-99), which is implicated in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). The direct synthesis (di-BAP 1) was performed using microwave irradiation. The indirect synthesis (di-BAP 2) was carried out performing an efficient chemoselective coupling reaction through the formation of a thioether bond. Both di-BAPs were conjugated to polysaccharide mannan since mannosylation is a promising technique to achieve modulation in immune response. The conjugation was achieved through free amino groups of both di-BAPs via the formation of Schiff bases. The mannan-conjugated di-BAPs were further evaluated in vivo in a prophylactic vaccination protocol, prior to EAE induction in Lewis rats.

Mannosylated bioreducible nanoparticle-mediated macrophage-specific TNF-α RNA interference for IBD therapy

The application of RNA interference (RNAi) for inflammatory bowel disease (IBD) therapy has been limited by the lack of non-cytotoxic, efficient and targetable small interfering RNA (siRNA) carriers. TNF-α is the major pro-inflammatory cytokine mainly secreted by macrophages during IBD. Here, a mannosylated bioreducible cationic polymer (PPM) was synthesized and further spontaneously assembled nanoparticles (NPs) assisted by sodium triphosphate (TPP). The TPP-PPM/siRNA NPs exhibited high uniformity (polydispersity index = 0.004), a small particle size (211-275 nm), excellent bioreducibility, and enhanced cellular uptake. Additionally, the generated NPs had negative cytotoxicity compared to control NPs fabricated by branched polyethylenimine (bPEI, 25 kDa) or Oligofectamine (OF) and siRNA. In vitro gene silencing experiments revealed that TPP-PPM/TNF-α siRNA NPs with a weight ratio of 40:1 showed the most efficient inhibition of the expression and secretion of TNF-α (approximately 69.9%, which was comparable to the 71.4% obtained using OF/siRNA NPs), and its RNAi efficiency was highly inhibited in the presence of mannose (20 mm). Finally, TPP-PPM/siRNA NPs showed potential therapeutic effects on colitis tissues, remarkably reducing TNF-α level. Collectively, these results suggest that non-toxic TPP-PPM/siRNA NPs can be exploited as efficient, macrophage-targeted carriers for IBD therapy.