Glycodendritic structures: promising new antiviral drugs

Electrostatic Surface Potential as a Key Parameter in Virus Transmission and Evolution: How to Manage Future Virus Pandemics in the Post-COVID-19 Era

Virus-cell interactions involve fundamental parameters that need to be considered in strategies implemented to control viral outbreaks. Among these, the surface electrostatic potential can give valuable information to deal with new epidemics. In this article, we describe the role of this key parameter in the hemagglutination of red blood cells and in the co-evolution of synaptic receptors and neurotransmitters. We then establish the functional link between lipid rafts and the electrostatic potential of viruses, with special emphasis on gangliosides, which are sialic-acid-containing, electronegatively charged plasma membrane components. We describe the common features of ganglioside binding domains, which include a wide variety of structures with little sequence homology but that possess key amino acids controlling ganglioside recognition. We analyze the role of the electrostatic potential in the transmission and intra-individual evolution of HIV-1 infections, including gatekeeper and co-receptor switch mechanisms. We show how to organize the epidemic surveillance of influenza viruses by focusing on mutations affecting the hemagglutinin surface potential. We demonstrate that the electrostatic surface potential, by modulating spike-ganglioside interactions, controls the hemagglutination properties of coronaviruses (SARS-CoV-1, MERS-CoV, and SARS-CoV-2) as well as the structural dynamics of SARS-CoV-2 evolution. We relate the broad-spectrum antiviral activity of repositioned molecules to their ability to disrupt virus-raft interactions, challenging the old concept that an antibiotic or anti-parasitic cannot also be an antiviral. We propose a new concept based on the analysis of the electrostatic surface potential to develop, in real time, therapeutic and vaccine strategies adapted to each new viral epidemic.

Developments in Treatment Methodologies Using Dendrimers for Infectious Diseases

Dendrimers comprise a specific group of macromolecules, which combine structural properties of both single molecules and long expanded polymers. The three-dimensional form of dendrimers and the extensive possibilities for use of additional substrates for their construction creates a multivalent potential and a wide possibility for medical, diagnostic and environmental purposes. Depending on their composition and structure, dendrimers have been of interest in many fields of science, ranging from chemistry, biotechnology to biochemical applications. These compounds have found wide application from the production of catalysts for their use as antibacterial, antifungal and antiviral agents. Of particular interest are peptide dendrimers as a medium for transport of therapeutic substances: synthetic vaccines against parasites, bacteria and viruses, contrast agents used in MRI, antibodies and genetic material. This review focuses on the description of the current classes of dendrimers, the methodology for their synthesis and briefly drawbacks of their properties and their use as potential therapies against infectious diseases.

Synthesis of Glycodendrimers with Antiviral and Antibacterial Activity

Glycodendrimers are an important class of synthetic macromolecules that can be used to mimic many structural and functional features of cell-surface glycoconjugates. Their carbohydrate moieties perform key important functions in bacterial and viral infections, often regulated by carbohydrate-protein interactions. Several studies have shown that the molecular structure, valency and spatial organisation of carbohydrate epitopes in glycoconjugates are key factors in the specificity and avidity of carbohydrate-protein interactions. Choosing the right glycodendrimers almost always helps to interfere with such interactions and blocks bacterial or viral adhesion and entry into host cells as an effective strategy to inhibit bacterial or viral infections. Herein, the state of the art in the design and synthesis of glycodendrimers employed for the development of anti-adhesion therapy against bacterial and viral infections is described.

Glycodendritic structures as DC-SIGN binders to inhibit viral infections

DC-SIGN, a lectin discovered two decades ago, plays a relevant role in innate immunity. Since its discovery, it has turned out to be a target for developing antiviral drugs based on carbohydrates due to its participation in the infection process of several pathogens. A plethora of carbohydrate multivalent systems using different scaffolds have been described to achieve this goal. Our group has made significant contributions to this field, which are revised herein.

Nanocarriers For Vaginal Drug Delivery

BACKGROUND

Vaginal drug delivery approach represents one of the imperative strategies for local and systemic delivery of drugs. The peculiar dense vascular networks, mucus permeability, and range of physiological characteristics of the vaginal cavity have been exploited for therapeutic benefit. Furthermore, the vaginal drug delivery has been curtailed due to the influence of different physiological factors like acidic pH, constant cervical secretion, microflora, cyclic changes during periods along with turnover of mucus of varying thickness.

OBJECTIVE

This review highlights advancement of nanomedicine and its prospective progress towards the clinic.

METHODS

Relevant literature reports and patents related to topics are retrieved and used.

RESULT

The extensive literature search and patent revealed that nanocarriers are efficacious over conventional treatment approaches.

CONCLUSION

Recently, nanotechnology based drug delivery approach has promised better therapeutic outcomes by providing enhanced permeation and sustained drug release activity. Different nanoplatforms based on drugs, peptides, proteins, antigens, hormones, nucleic material, and microbicides are gaining momentum for vaginal therapeutics.

Mechanistic Studies of Viral Entry: An Overview of Dendrimer-Based Microbicides As Entry Inhibitors Against Both HIV and HSV-2 Overlapped Infections

This review provides an overview of the development of different dendrimers, mainly polyanionic, against human immunodeficiency virus (HIV) and genital herpes (HSV-2) as topical microbicides targeting the viral entry process. Vaginal topical microbicides to prevent sexually transmitted infections such as HIV and HSV-2 are urgently needed. To inhibit HIV/HSV-2 entry processes, new preventive targets have been established to maximize the current therapies against wild-type and drug-resistant viruses. The entry of HIV/HSV-2 into target cells is a multistep process that triggers a cascade of molecular interactions between viral envelope proteins and cell surface receptors. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV/HSV-2. Inhibitors of each entry step have been identified with regard to generations and surface groups, and possible roles for these agents in anti-HIV/HSV-2 therapies have also been discussed. Four potential binding sites for impeding HIV infection (HSPG, DC-SIGN, GSL, and CD4/gp120 inhibitors) and HSV-2 infection (HS, gB, gD, and gH/gL inhibitors) exist according to their mechanisms of action and structures. This review clarifies that inhibition of HIV/HSV-2 entry continues to be a promising target for drug development because nanotechnology can transform the field of HIV/HSV-2 prevention by improving the efficacy of the currently available antiviral treatments.

Nanoparticle-based drug delivery to the vagina: a review

Vaginal drug administration can improve prophylaxis and treatment of many conditions affecting the female reproductive tract, including sexually transmitted diseases, fungal and bacterial infections, and cancer. However, achieving sustained local drug concentrations in the vagina can be challenging, due to the high permeability of the vaginal epithelium and expulsion of conventional soluble drug dosage forms. Nanoparticle-based drug delivery platforms have received considerable attention for vaginal drug delivery, as nanoparticles can provide sustained release, cellular targeting, and even intrinsic antimicrobial or adjuvant properties that can improve the potency and/or efficacy of prophylactic and therapeutic modalities. Here, we review the use of polymeric nanoparticles, liposomes, dendrimers, and inorganic nanoparticles for vaginal drug delivery. Although most of the work toward nanoparticle-based drug delivery in the vagina has been focused on HIV prevention, strategies for treatment and prevention of other sexually transmitted infections, treatment for reproductive tract cancer, and treatment of fungal and bacterial infections are also highlighted.

A multivalent inhibitor of the DC-SIGN dependent uptake of HIV-1 and Dengue virus

DC-SIGN is a C-type lectin receptor on antigen presenting cells (dendritic cells) which has an important role in some viral infection, notably by HIV and Dengue virus (DV). Multivalent presentation of carbohydrates on dendrimeric scaffolds has been shown to inhibit DC-SIGN binding to HIV envelope glycoprotein gp120, thus blocking viral entry. This approach has interesting potential applications for infection prophylaxis. In an effort to develop high affinity inhibitors of DC-SIGN mediated viral entry, we have synthesized a group of glycodendrimers of different valency that bear different carbohydrates or glycomimetic DC-SIGN ligands and have studied their DC-SIGN binding activity and antiviral properties both in an HIV and a Dengue infection model. Surface Plasmon Resonance (SPR) competition studies have demonstrated that the materials obtained bind efficiently to DC-SIGN with IC50s in the μm range, which depend on the nature of the ligand and on the valency of the scaffold. In particular, a hexavalent presentation of the DC-SIGN selective antagonist 4 displayed high potency, as well as improved accessibility and chemical stability relative to previously reported dendrimers. At low μm concentration the material was shown to block both DC-SIGN mediated uptake of DV by Raji cells and HIV trans-infection of T cells.

Macromolecular prodrugs for controlled delivery of ribavirin

Ribavirin (RBV)-containing polymers are synthesized based on poly(N-vinylpyrrolidone) and poly(acrylic acid), two polymers with extensive characterization in biomedicine. The copolymers are shown to exhibit a minor to negligible degree of association with erythrocytes, thus effectively eliminating the origin of the main side effects of RBV. The therapeutic benefit of macromolecular RBV prodrugs is illustrated by matched efficacy in suppressing production of nitric oxide by stimulated cultured macrophages as compared to pristine RBV with no associated cytotoxicity, which is in stark contrast to an RBV-based treatment which results in a significant decrease in cell viability. These results contribute to the development of antiviral polymer therapeutics and delivery of RBV in particular.

Glycodendritic structures: tools to interact with DC-SIGN

The key role of carbohydrates in many biological events has attracted the interest of the scientific community. This fact has demanded the access to new tools necessary to understand this role and the interaction of carbohydrates with their corresponding receptors, lectins. Glycodendrimers and glycodendritic structures in general, have demonstrated to be very efficient and interesting tools to intervene in those processes where carbohydrates participate. In this review, we discuss the different glycodendritic structures that have been used to interfere with DC-SIGN, a very attractive lectin involved in infection processes and in the regulation of the immune response.

Quinoxalinone Inhibitors of the Lectin DC-SIGN

The C-type lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) can serve as a docking site for pathogens on the surface of dendritic cells. Pathogen binding to DC-SIGN can have diverse consequences for the host. DC-SIGN can facilitate HIV-1 dissemination, but the interaction of Mycobacterium tuberculosis with DC-SIGN is important for host immunity. The ability of pathogens to target DC-SIGN provides impetus to identify ligands that can perturb these interactions. Here, we describe the first stable small molecule inhibitors of DC-SIGN. These inhibitors were derived from a collection of quinoxalinones, which were assembled using a tandem cross metathesis-hydrogenation sequence. To assess the ability of these small molecules to block DC-SIGN-mediated glycan adhesion and internalization, we developed a sensitive flow cytometry assay. Our results reveal that the quinoxalinones are effective inhibitors of DC-SIGN-glycan interactions. These compounds block both glycan binding to cells and glycan internalization. We anticipate that these non-carbohydrate inhibitors can be used to elucidate the role of DC-SIGN in pathogenesis and immune function.

A glycomimetic compound inhibits DC-SIGN-mediated HIV infection in cellular and cervical explant models

OBJECTIVE

Dendritic cell-specific intercellular adhesion molecule (ICAM)-3 grabbing nonintegrin (DC-SIGN) participates in the initial stages of sexually transmitted HIV-1 infection by recognizing highly mannosylated structures presented in multiple copies on HIV-1 gp120 and promoting virus dissemination. Inhibition of HIV interaction with DC-SIGN thus represents a potential therapeutic approach for viral entry inhibition at the mucosal level.

DESIGN

Herein we evaluate the efficacy in inhibiting HIV-1 infection and the potential toxicity of a multimeric glycomimetic DC-SIGN ligand (Dendron 12).

METHODS

The ability of Dendron 12 to block HIV-1 infection was assessed in cellular and human cervical explant models. Selectivity of Dendron 12 towards DC-SIGN and langerin was evaluated by surface plasmon resonance studies. β chemokine production following stimulation with Dendron 12 was also analyzed. Toxicity of the compound was evaluated in cellular and tissue models.

RESULTS

Dendron 12 averted HIV-1 trans infection of CD4(+) T lymphocytes in presence of elevated viral loads and prevented HIV-1 infection of human cervical tissues, under conditions mimicking compromised epithelial integrity, by multiple clades of R5 and X4 tropic viruses. Treatment with Dendron 12 did not interfere with the activity of langerin and also significantly elicited the production of the β chemokines MIP-1α, MIP-1β and RANTES.

CONCLUSION

Dendron 12 thus inhibits HIV-1 infection by competition with binding of HIV to DC-SIGN and stimulation of β-chemokine production. Dendron 12 represents a promising lead compound for the development of anti-HIV topical microbicides.

Synthesis of a glycodendrimer incorporating multiple mannosides on a glucoside core

The synthesis of a glycodendrimer by incorporating repetitive mannoside units onto a glucoside core was carried out to multivalently probe fundamental carbohydrate–protein interactions. The dendritic structure was constructed by a modified procedure that utilized multiple glycosylations between a thioether glycosyl donor and five elongated spacer arms of a glycosyl acceptor. The completed dendrimer bears a full carbohydrate structure, and thus should find its potential application in the study of mannose–lectin interactions.

HIV microbicides: state-of-the-art and new perspectives on the development of entry inhibitors

Since the discovery of HIV at the beginning of the 1980s, numerous efforts have been devoted to the search of an efficient vaccine. There are at least 25 drugs available for HIV treatment, but no cure is available. The observation that therapy for HIV disease is life long and that these drugs are associated with a number of side effects underlines the need for approaches aimed at preventing rather than treating infection. Additionally, the economic burden of treatment for the HIV infection occupies an increasing share of healthcare expenditure, making current practices likely to become difficult to sustain in the long run. Unfortunately, no effective vaccine for this disease is foreseeable in the near future. Microbicides could be an alternate way to build preventative approaches to HIV infection. Strategies based on preventing the virus from reaching its target cells seem to have some room for development and application. In this review we explore the state-of-the-art of available microbicides, focusing on HIV entry inhibitors. In addition, we discuss new compounds that show anti-HIV activity, which could be effective candidates.

Design, synthesis and activity evaluation of mannose-based DC-SIGN antagonists

In this article, we describe the design, synthesis and activity evaluation of glycomimetic DC-SIGN antagonists, that use a mannose residue to anchor to the protein carbohydrate recognition domain (CRD). The molecules were designed from the structure of the known pseudo-mannobioside antagonist 1, by including additional hydrophobic groups, which were expected to engage lipophilic areas of DC-SIGN CRD. The results demonstrate that the synthesized compounds potently inhibit DC-SIGN-mediated adhesion to mannan coated plates. Additionally, in silico docking studies were performed to rationalize the results and to suggest further optimization.

A general glycomimetic strategy yields non-carbohydrate inhibitors of DC-SIGN

Shikimic acid can be transformed into monovalent and multivalent glycomimetics that target different members of the C-type lectin class, including DC-SIGN, a dendritic cell lectin that facilitates HIV transmission.

Potential of carbohydrate-binding agents as therapeutics against enveloped viruses

Twenty‐seven years after the discovery of HIV as the cause of AIDS more than 25 drugs directed against four different viral targets (i.e. reverse transcriptase, protease, integrase, envelope gp41) and one cellular target (i.e. CCR5 co‐receptor) are available for treatment. However, the search for an efficient vaccine is still ongoing. One of the main problems is the presence of a continuously evolving dense carbohydrate shield, consisting of N‐linked glycans that surrounds the virion and protects it against efficient recognition and persistent neutralization by the immune system. However, several lectins from the innate immune system specifically bind to these glycans in an attempt to process the virus antigens to provoke an immune response. Across a wide variety of different species in nature lectins can be found that can interact with the glycosylated envelope of HIV‐1 and can block the infection of susceptible cells by the virus. In this review, we will give an overview of the lectins from non‐mammalian origin that are endowed with antiviral properties and discuss the complex interactions between lectins of the innate immune system and HIV‐1. Also, attention will be given to different carbohydrate‐related modalities that can be exploited for antiviral chemotherapy.  © 2010 Wiley Periodicals, Inc. Med Res Rev

Inhibition of DC-SIGN-mediated HIV infection by a linear trimannoside mimic in a tetravalent presentation

HIV infection is pandemic in humans and is responsible for millions of deaths every year. The discovery of new cellular targets that can be used to prevent the infection process represents a new opportunity for developing more effective antiviral drugs. In this context, dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN), a lectin expressed at the surface of immature dendritic cells and involved in the initial stages of HIV infection, is a promising therapeutic target. Herein we show the ability of a new tetravalent dendron containing four copies of a linear trimannoside mimic to inhibit the trans HIV infection process of CD4+ T lymphocytes at low micromolar range. This compound presents a high solubility in physiological media, a neglectable cytotoxicity, and a long-lasting effect and is based on carbohydrate-mimic units. Notably, the HIV antiviral activity is independent of viral tropism (X4 or R5). The formulation of this compound as a gel could allow its use as topical microbicide.

Dendrimers as therapeutic agents: a systematic review

Objectives

Dendrimers by virtue of their therapeutic value have recently generated enormous interest among biomedical scientists. This review describes the therapeutic prospects of the dendrimer system.

Key findings

Their bioactivity suggests them to be promising therapeutic agents, especially in wound healing, bone mineralisation, cartilage formation and tissue repair, and in topical treatments to prevent HIV transmission. Findings also demonstrate their potential as anti-prion, anti-Alzheimer's, anticoagulant, antidote, anti-inflammatory and anticancer agents. One of the dendrimer-based formulations with activity against herpes simplex virus (VivaGel from Starpharma) has successfully completed phase I clinical trials and is expected to be available on the market soon.

Summary

All reports cited in this review demonstrate the use of dendrimers as medical therapeutics in different ailments. The review focuses on the current state of therapeutic potential of the dendrimer system.

Dendrimers for enhanced drug solubilization

Approximately 40% of newly developed drugs are rejected by the pharmaceutical industry and will never benefit a patient because of low water solubility. Another 17% of launched drugs exhibit suboptimal performance for the same reason. Given the growing impact and need for drug delivery, a thorough understanding of delivery technologies that enhance the bioavailability of drugs is important. The high level of control over the dendritic architecture (size, branching density, surface functionality) makes dendrimers ideal excipients for enhanced solubility of poorly water-soluble drugs. Many commercial small-molecule drugs with anticancer, anti-inflammatory and antimicrobial activity have been formulated successfully with dendrimers, such as poly(amidoamine) (PAMAM), poly(propylene imine) (PPI or DAB) and poly(etherhydroxylamine) (PEHAM). Some dendrimers themselves show pharmaceutical activity in these three areas, providing the opportunity for combination therapy in which the dendrimers serve as the drug carrier and simultaneously as an active part of the therapy.

Glycopeptide dendrimers, part III: a review. Use of glycopeptide dendrimers in immunotherapy and diagnosis of cancer and viral diseases

Glycopeptide dendrimers containing different types of tumor associated-carbohydrate antigens (T(N), TF, sialyl-T(N), sialyl-TF, sialyl-Le(x), sialyl-Le(a) etc.) were used in diagnosis and therapy of different sorts of cancer. These dendrimeric structures with incorporated T-cell epitopes and adjuvants can be used as antitumor vaccines. Best results were obtained with multiantigenic vaccines, containing, e.g. five or six different TAAs. The topic of TAAs and their dendrimeric forms at molecular level are reviewed, including structure, syntheses, and biological activities. Use of glycopeptide dendrimers as antiviral vaccines against HIV and influenza is also described. Their syntheses, physico-chemical properties, and biological activities are given with many examples.

Synthesis of new polyether glycodendrons as oligosaccharide mimetics

Divalent and tetravalent glycomimetics based on polyether glycodendrons have been prepared. The branched scaffolds were decorated with galactose moieties on one hand and were elaborated into new glycodendrons of a 'mixed' type on the other, carrying both galactose and mannose moieties as biologically important sugar epitopes. All synthesized glycodendrons possess a focal point that can be employed for further derivatization and functionalization.

Mannosylated G(0) Dendrimers with Nanomolar Affinities toEscherichia coli FimH

Pentaerythritol and bis-pentaerythritol scaffolds were used for the preparation of first generation glycodendrimers bearing aryl alpha-D-mannopyranoside residues assembled using single-step Sonogashira and click chemistry. The carbohydrate precursors were built with either para-iodophenyl, propargyl, or 2-azidoethyl aglycones whereas the pentaerythritol moieties were built with terminal azide or propargyl groups, respectively. Cross-linking abilities of this series of glycodendrimers were first evaluated with the lectin from Canavalia ensiformis (Concanavalin A). Surface plasmon resonance measurements showed these two families of mannosylated clusters as the best ligands known to date toward Escherichia coli K12 FimH with subnanomolar affinities. Tetramer 4 had a K(d) of 0.45 nM. These clusters were 1000 times more potent than mannose for their capacity to inhibit the binding of E. coli to erythrocytes in vitro.

Antibacterial activities of poly(amidoamine) dendrimers terminated with amino and poly(ethylene glycol) groups

Poly(amidoamine) (PAMAM) dendrimer derivatives have been investigated for their biological applications, especially for delivery of drugs, including antimicrobial drugs to eukaryotic cells, but their effects on bacterial cells are largely unexplored. Herein we report that amino-terminated PAMAM dendrimers are highly toxic to the common Gram-negative pathogen Pseudomonas aeruginosa. The concentration that kills 50% of the bacteria (EC50) was in the range of approximately 0.9-1.5 microg/mL for the generation 5, amino-terminated dendrimers with or without partial (43%) coating of poly(ethylene glycol) (PEG). These EC50 values were lower than that ( approximately 1.9-2.8 microg/mL) for LL-37, a potent antimicrobial peptide expressed in a variety of epithelia. On the contrary, the dendrimers were far less toxic (EC50 > 21 microg/mL) to the Gram-positive pathogen Staphylococcus aureus than LL-37 (EC50 = approximately 1.9 microg/mL). In agreement with the previous studies on other cell types, the dendrimers were not cytotoxic to human corneal epithelial cells at the concentrations that were toxic to P. aeruginosa. Our findings indicate that amino-terminated PAMAM dendrimers and their partially PEG-coated derivatives possess attractive antimicrobial properties, particularly against Gram-negative bacteria, thus expanding the potential biological application of the dendrimers.

Mannose Glycoconjugates Functionalized at Positions 1 and 6. Binding Analysis to DC-SIGN Using Biosensors

The design of glycoconjugates to allow the generation of multivalent ligands capable of interacting with the receptor DC-SIGN is a topic of high interest due to the role played by this lectin in pathogen infections. Mannose, a ligand of this lectin, could be conjugated at two different positions, 1 and 6, not implicated in the binding process. We have prepared mannose conjugates at these two positions with a long spacer to allow their attachment to a biosensor chip surface. Analysis of the interaction between these surfaces and the tetravalent extracellular domain (ECD) of DC-SIGN by SPR biosensor has demonstrated that both positions are available for this conjugation without affecting the protein binding process. These results emphasize the possibility to conjugate mannose at position 6, allowing the incorporation of hydrophobic groups at the anomeric position to interact with hydrophobic residues in the carbohydrate recognition domain of DC-SIGN, increasing binding affinities. This fact is relevant for the future design of new ligands and the corresponding multivalent systems for DC-SIGN.

Progress towards the treatment of Ebola haemorrhagic fever

Being highly pathogenic for human and nonhuman primates and the subject of former weapon programmes makes Ebola virus one of the most feared pathogens worldwide today. Due to a lack of licensed pre- and postexposure intervention, the current response depends on rapid diagnostics, proper isolation procedures and supportive care of case patients. Consequently, the development of more specific countermeasures is of high priority for the preparedness of many nations. Over the past years, enhanced research efforts directed to better understand virus replication and pathogenesis have identified potential new targets for intervention strategies. The authors discuss the most promising therapeutic approaches for Ebola haemorrhagic fever as judged by their efficacy in animal models. The current development in this field encourages discussions on how to move some of the experimental approaches towards clinical application.

Engineered nanoparticles as precise drug delivery systems

With the remarkable development of nanotechnology in recent years, new drug delivery approaches based on the state-of-the-art nanotechnology have been receiving significant attention. Nanoparticles, an evolvement of nanotechnology, are increasingly considered as a potential candidate to carry therapeutic agents safely into a targeted compartment in an organ, particular tissue or cell. These particles are colloidal structures with a diameter smaller than 1,000 nm, and therefore can penetrate through diminutive capillaries into the cell's internal machinery. This innovative delivery technique might be a promising technology to meet the current challenges in drug delivery. When loaded with a gene or drug agent, nanoparticles can become nanopills, which can effectively treat problematical diseases such as cancer. This article summarizes different types of nanoparticles drug delivery systems under investigation and their prospective therapeutic applications. Also, this article presents a closer look at the advances, current challenges, and future direction of nanoparticles drug delivery systems.

Microbead analysis of cell binding to immobilized lectin: an alternative to microarrays in the development of carbohydrate drugs and diagnostic tests

Microarray technology is currently used in the development of carbohydrate drugs and diagnostic tests. Here we model an inexpensive alternative to microarrays using derivatized microbeads. In this model we examine the binding of mannose-rich yeast to microbeads derivatized with concanavalin A (Con A), a mannose-binding lectin, in the presence of 30 different sugars and 9 different pH conditions. We developed a listing of effective saccharide inhibitors of immobilized Con A based on 3901 replicates. We suggest that this is the most extensive saccharide inhibitor list ever developed for this lectin and it may be useful to use this listing to replace the less extensive lists that have been in the literature for decades. Information is also provided on pH effects on immobilized Con A binding based on 918 trials. Two assays to study binding, one which qualitatively scores more or less binding than control in thousands of replicate samples, and another that quantitatively evaluates binding by counting the number of cells bound to each bead, are also modeled here. We know of no previous studies that provide such extensive information on saccharide inhibition and pH effects on the binding of immobilized Con A. We suggest that this microbead approach, using beads derivatized with lectins or sugars, and the two simple assays presented here, can in some cases substitute for more expensive microarray technology in the development of carbohydrate drugs and diagnostic tests. If, for example, our model Saccharomyces cerevisiae was a pathogen, these studies show that it binds via cell surface mannose residues and drugs to prevent binding could be developed using the inhibitors of binding identified here. The beads could be also used in the development of diagnostic tests that identify the presence of the organism in blood samples, etc. in much the same way as microarray technology is being used today.