Broad-spectrum in vitro activity and in vivo efficacy of the antiviral protein griffithsin against emerging viruses of the family Coronaviridae

Viruses of the family Coronaviridae have recently emerged through zoonotic transmission to become serious human pathogens. The pathogenic agent responsible for severe acute respiratory syndrome (SARS), the SARS coronavirus (SARS-CoV), is a member of this large family of positive-strand RNA viruses that cause a spectrum of disease in humans, other mammals, and birds. Since the publicized outbreaks of SARS in China and Canada in 2002-2003, significant efforts successfully identified the causative agent, host cell receptor(s), and many of the pathogenic mechanisms underlying SARS. With this greater understanding of SARS-CoV biology, many researchers have sought to identify agents for the treatment of SARS. Here we report the utility of the potent antiviral protein griffithsin (GRFT) in the prevention of SARS-CoV infection both in vitro and in vivo. We also show that GRFT specifically binds to the SARS-CoV spike glycoprotein and inhibits viral entry. In addition, we report the activity of GRFT against a variety of additional coronaviruses that infect humans, other mammals, and birds. Finally, we show that GRFT treatment has a positive effect on morbidity and mortality in a lethal infection model using a mouse-adapted SARS-CoV and also specifically inhibits deleterious aspects of the host immunological response to SARS infection in mammals.

A new lectin with highly potent antihepatoma and antisarcoma activities from the oyster mushroom Pleurotus ostreatus

A dimeric lectin, composed of subunits with a molecular weight of 40 and 41 kDa, respectively, and demonstrating similarity in N-terminal sequence to each other and to Aleuria aurantia lectin, was isolated from fresh fruiting bodies of the edible mushroom Pleurotus ostreatus. The lectin was unadsorbed on DEAE-cellulose in 10 mmol/L phosphate buffer (pH 7.5), subsequently adsorbed on CM-cellulose in 10 mmol/L NH(4)OAc (pH 5.4), and came off in the first peak from a Superose 12 column during fast protein liquid chromatography. The lectin was acid-labile, alkali-labile, and heat-labile. Its hemagglutinating activity was sensitive to inhibition by CaCl(2), MgCl(2), MnCL(2) and FeCl(3) and potentiation by AlCl(3). Melibiose, lactose, d-galactose, alpha-methyl-d-galactopyranoside, N-acetylneuraminic acid, raffinose, and inulin were capable of inhibiting its hemagglutinating activity, with melibiose being the most potent. The lectin exerted potent antitumor activity in mice bearing sarcoma S-180 and hepatoma H-22. Survival in these mice was prolonged and body weight increase reduced after lectin treatment.

Lectins with potential for anti-cancer therapy

This article reviews lectins of animal and plant origin that induce apoptosis and autophagy of cancer cells and hence possess the potential of being developed into anticancer drugs. Apoptosis-inducing lectins encompass galectins, C-type lectins, annexins, Haliotis discus discus lectin, Polygonatum odoratum lectin, mistletoe lectin, and concanavalin A, fucose-binding Dicentrarchus labrax lectin, and Strongylocentrotus purpuratus lectin, Polygonatum odoratum lectin, and mistletoe lectin, Polygonatum odoratum lectin, autophagy inducing lectins include annexins and Polygonatum odoratum lectin.

Siglecs as targets for therapy in immune-cell-mediated disease

The sialic-acid-binding immunoglobulin-like lectins (siglecs) comprise a family of receptors that are differentially expressed on leukocytes and other immune cells. The restricted expression of several siglecs to one or a few cell types makes them attractive targets for cell-directed therapies. The anti-CD33 (also known as Siglec-3) antibody gemtuzumab (Mylotarg) is approved for the treatment of acute myeloid leukemia, and antibodies targeting CD22 (Siglec-2) are currently in clinical trials for treatment of B cell non-Hodgkins lymphomas and autoimmune diseases. Because siglecs are endocytic receptors, they are well suited for a 'Trojan horse' strategy, whereby therapeutic agents conjugated to an antibody, or multimeric glycan ligand, bind to the siglec and are efficiently carried into the cell. Although the rapid internalization of unmodified siglec antibodies reduces their utility for induction of antibody-dependent cellular cytotoxicity or complement-mediated cytotoxicity, antibody binding of Siglec-8, Siglec-9 and CD22 has been demonstrated to induce apoptosis of eosinophils, neutrophils and depletion of B cells, respectively. Here, we review the properties of siglecs that make them attractive for cell-targeted therapies.

Photodynamic therapy in oncology

Photodynamic therapy (PDT) is a cancer treatment modality that is based on the administration of a photosensitiser, which is retained in tumour tissues more than in normal tissues, followed by illumination of the tumour with visible light in a wavelength range matching the absorption spectrum of the photosensitiser. The photosensitiser absorbs light energy and induces the production of reactive oxygen species in the tumour environment, generating a cascade of events that kills the tumour cells. The first generation photosensitiser, Photofrin (porfirmer sodium), has been approved for oesophageal and lung cancer in the US and has been under investigation for other malignant and non-malignant diseases. Sub-optimal light penetration at the treatment absorption peak of Photofrin and prolonged skin photosensitivity in patients are limiting factors for this preparation. Several new photosensitisers have improved properties, especially absorption of longer wavelength light which penetrates deeper into tissue and faster clearance from normal tissue. This paper reviews the current use of first- and second-generation photosensitisers in oncology. The use of PDT in oncology has been restricted to certain cancer indications and has not yet become an integral part of cancer treatment in general. The main advantage of PDT is that the treatment can be repeated multiple times safely, without producing immunosuppressive and myelosuppressive effects and can be administered even after surgery, chemotherapy or radiotherapy. The current work on new photosensitisers and light delivery equipment will address some of the present shortcomings of PDT. Much has been learned in recent years about the mechanisms of cellular and tissue responses to PDT and protocols designed to capitalise on this knowledge showed lead to additional improvements.

Drug targeting to the colon with lectins and neoglycoconjugates

Targeting of drugs to specific sites of action provides several advantages over non-targeted drugs. These include the prevention of side effects of drugs on healthy tissues and enhancement of drug uptake by targeted cells. This review will cover traditional approaches of colon drug targeting as well as the use of lectins and neoglycoconjugates for the targeted delivery. Direct and reverse targeting strategies, potential molecular targets and targeting moieties for colon drug delivery, targeted drug delivery systems (DDS) for colon delivery, anticancer DDS targeted to colon cancer are examined. Directions of future development are discussed.

Concanavalin A induces autophagy in hepatoma cells and has a therapeutic effect in a murine in situ hepatoma model

Concanavalin A (ConA), a lectin with mannose specificity that can induce acute hepatic inflammation, was tested for its therapeutic effect against hepatoma. ConA is cytotoxic or inhibitory to hepatoma cells, which is mediated by the autophagic pathway through mitochondria. Once it was bound to cell membrane glycoproteins, the ConA was internalized and preferentially localized onto the mitochondria. The mitochondria membrane permeability changed, and an autophagic pathway including LC3-II generation, double-layer vesicle, BNIP3 induction, and acidic vesicular organelle formation was induced. Either 3-MA or siRNA for BNIP3 and LC3, but neither beclin-1 nor ATG 5, partially inhibited the ConA-induced cell death. In addition to the autophagy induction, ConA is known to be a T cell mitogen. Using an in situ hepatoma model, ConA can exert an anti-hepatoma therapeutic effect, inhibiting tumor nodule formation in the liver and prolonging survival.

CONCLUSION

ConA can be considered as an anti-hepatoma agent therapeutically because of its autophagic induction and immunomodulating activity. This dual function of ConA provides a novel mechanism for the biological effect of lectin.

Mannose-specific plant lectins from the Amaryllidaceae family qualify as efficient microbicides for prevention of human immunodeficiency virus infection

The plant lectins derived from Galanthus nivalis (Snowdrop) (GNA) and Hippeastrum hybrid (Amaryllis) (HHA) selectively inhibited a wide variety of human immunodeficiency virus type 1 (HIV-1) and HIV-2 strains and clinical (CXCR4- and CCR5-using) isolates in different cell types. They also efficiently inhibited infection of T lymphocytes by a variety of mutant virus strains. GNA and HHA markedly prevented syncytium formation between persistently infected HUT-78/HIV cells and uninfected T lymphocytes. The plant lectins did not measurably affect the antiviral activity of other clinically approved anti-HIV drugs used in the clinic when combined with these drugs. Short exposure of the lectins to cell-free virus particles or persistently HIV-infected HUT-78 cells markedly decreased HIV infectivity and increased the protective (microbicidal) activity of the plant lectins. Flow cytometric analysis and monoclonal antibody binding studies and a PCR-based assay revealed that GNA and HHA do not interfere with CD4, CXCR4, CCR5, and DC-SIGN and do not specifically bind with the membrane of uninfected cells. Instead, GNA and HHA likely interrupt the virus entry process by interfering with the virus envelope glycoprotein. HHA and GNA are odorless, colorless, and tasteless, and they are not cytotoxic, antimetabolically active, or mitogenic to human primary T lymphocytes at concentrations that exceed their antivirally active concentrations by 2 to 3 orders of magnitude. GNA and HHA proved stable at high temperature (50 degrees C) and low pH (5.0) for prolonged time periods and can be easily formulated in gel preparations for microbicidal use; they did not agglutinate human erythrocytes and were not toxic to mice when administered intravenously.

Use of lectins as diagnostic and therapeutic tools for cancer

Within the past few years, lectins have become a well-established means for understanding varied aspects of cancer and metastasis. Evidence is now emerging that lectins are dynamic contributors to tumor cell recognition (surface markers), cell adhesion and localization, signal transduction across membranes, mitogenic stimulation, augmentation of host immune defense, cytotoxicity, and apoptosis. To advance understanding of these lectin-dependent processes, attempts are being made to discover new lectins that have one or more of these functions and to develop lectin- (or glycoconjugate-) based tools that could be used to home in on tumor cells. This review will summarize current research on the lectins and recent advances in the development of lectin-based diagnostic and therapeutic tools for cancer. Additionally, the future potential of lectin-based diagnosis and therapy is discussed.

Inhibition of several strains of influenza virus in vitro and reduction of symptoms by an elderberry extract (Sambucus nigra L.) during an outbreak of influenza B Panama

A standardized elderberry extract, Sambucol (SAM), reduced hemagglutination and inhibited replication of human influenza viruses type A/Shangdong 9/93 (H3N2), A/Beijing 32/92 (H3N2), A/Texas 36/91 (H1N1), A/Singapore 6/86 (H1N1), type B/Panama 45/90, B/Yamagata 16/88, B/Ann Arbor 1/86, and of animal strains from Northern European swine and turkeys, A/Sw/Ger 2/81, A/Tur/Ger 3/91, and A/Sw/Ger 8533/91 in Madin-Darby canine kidney cells. A placebo-controlled, double blind study was carried out on a group of individuals living in an agricultural community (kibbutz) during an outbreak of influenza B/Panama in 1993. Fever, feeling of improvement, and complete cure were recorded during 6 days. Sera obtained in the acute and convalescent phases were tested for the presence of antibodies to influenza A, B, respiratory syncytial, and adenoviruses. Convalescent phase serologies showed higher mean and mean geometric hemagglutination inhibition (HI) titers to influenza B in the group treated with SAM than in the control group. A significant improvement of the symptoms, including fever, was seen in 93.3% of the cases in the SAM-treated group within 2 days, whereas in the control group 91.7% of the patients showed an improvement within 6 days (p < 0.001). A complete cure was achieved within 2 to 3 days in nearly 90% of the SAM-treated group and within at least 6 days in the placebo group (p < 0.001). No satisfactory medication to cure influenza type A and B is available. Considering the efficacy of the extract in vitro on all strains of influenza virus tested, the clinical results, its low cost, and absence of side-effects, this preparation could offer a possibility for safe treatment for influenza A and B.

Potential anti-HIV agents from marine resources: an overview

Human immunodeficiency virus (HIV) infection causes acquired immune deficiency syndrome (AIDS) and is a global public health issue. Anti-HIV therapy involving chemical drugs has improved the life quality of HIV/AIDS patients. However, emergence of HIV drug resistance, side effects and the necessity for long-term anti-HIV treatment are the main reasons for failure of anti-HIV therapy. Therefore, it is essential to isolate novel anti-HIV therapeutics from natural resources. Recently, a great deal of interest has been expressed regarding marine-derived anti-HIV agents such as phlorotannins, sulfated chitooligosaccharides, sulfated polysaccharides, lectins and bioactive peptides. This contribution presents an overview of anti-HIV therapeutics derived from marine resources and their potential application in HIV therapy.

M cell targeting by lectins: a strategy for mucosal vaccination and drug delivery

Bioadhesins are a recognised method of enhancing the absorption of drugs and vaccines at mucosal surfaces. Additionally, bioadhesins allow for cell specific targeting. Lectin-mediated targeting and delivery exploits unique surface carbohydrates on mucosal epithelial cells. The antigen-sampling M cells offer a portal for absorption of colloidal and particulate delivery vehicles, including bacteria, viruses and inert microparticles. We review work supporting the use of lectins to aid targeting to intestinal M cells. Consideration is also given to lectin-mediated targeting in non-intestinal sites and to the potential application of other bioadhesins to enhance M cell transport. While substantial hurdles must be overcome before mucosal bioadhesins can guarantee consistent, safe, effective mucosal delivery, this strategy offers novel opportunities for drug and vaccine formulation.

The cyanobacterial lectin scytovirin displays potent in vitro and in vivo activity against Zaire Ebola virus

The cyanobacterial lectin scytovirin (SVN) binds with high affinity to mannose-rich oligosaccharides on the envelope glycoprotein (GP) of a number of viruses, blocking entry into target cells. In this study, we assessed the ability of SVN to bind to the envelope GP of Zaire Ebola virus (ZEBOV) and inhibit its replication. SVN interacted specifically with the protein's mucin-rich domain. In cell culture, it inhibited ZEBOV replication with a 50% virus-inhibitory concentration (EC50) of 50 nM, and was also active against the Angola strain of the related Marburg virus (MARV), with a similar EC50. Injected subcutaneously in mice, SVN reached a peak plasma level of 100 nm in 45 min, but was cleared within 4h. When ZEBOV-infected mice were given 30 mg/kg/day of SVN by subcutaneous injection every 6h, beginning the day before virus challenge, 9 of 10 animals survived the infection, while all infected, untreated mice died. When treatment was begun one hour or one day after challenge, 70-90% of mice survived. Quantitation of infectious virus and viral RNA in samples of serum, liver and spleen collected on days 2 and 5 postinfection showed a trend toward lower titers in treated than control mice, with a significant decrease in liver titers on day 2. Our findings provide further evidence of the potential of natural lectins as therapeutic agents for viral infections.

Oral administration of an edible-mushroom-derived protein inhibits the development of food-allergic reactions in mice

BACKGROUND

Food allergy is a common disease without effective treatment. Since strict elimination of food allergens may be difficult, strategies for effective intervention are urgently needed.

OBJECTIVE

The aim was to investigate the prophylactic use of orally administrated FIP-fve, an immunomodulatory protein isolated from the edible mushroom Flammulina velutipes, in a murine model of food allergy.

METHODS

BALB/c mice were immunized twice intraperitoneally with ovalbumin (OVA), at an interval of 2 weeks. Before and during each period of immunization, FIP-fve (200 microg per mouse) or phosphate-buffered saline was given orally every other day with a total of five doses. Then OVA-specific antibodies and cytokine profiles were determined. Subsequently, the mice were orally challenged with OVA. Symptoms of anaphylaxis, levels of plasma histamine, and histology of intestines were examined.

RESULTS

Mice receiving oral FIP-fve treatment during sensitization to OVA had an impaired OVA-specific IgE response with a Th1-predominant cytokine profile. These mice were protected from systemic anaphylaxis-like symptoms induced by subsequent oral challenge with OVA.

CONCLUSION

Oral administration of FIP-fve has a Th1-skewing effect on the development of the allergen-specific immune response, and may serve the purpose of immunoprophylaxis for food allergy and other allergic diseases.

Efficacy of galectins in the amelioration of nephrotoxic serum nephritis in Wistar Kyoto rats

BACKGROUND

Galectins are characterized by specific affinity for beta-galactoside sugars, and they play a role in diverse biological processes, including cell adhesion, cell proliferation, and apoptosis. Galectin-1, -3, and -9 have been implicated in modulating the immune response.

METHODS

Nephrotoxic serum nephritis, which is characterized by crescent formation and glomerular influx of CD8+ cells into glomerular capillaries, was induced in Wistar Kyoto (WKY) rats by injecting rabbit antiglomerular basement membrane serum. Following induction, the rats were treated either with phosphate-buffered saline or dexamethasone, galectin-1, galectin-3, or galectin-9 on alternate days and were sacrificed at day 14. At day 8, splenic lymphocytes were isolated and employed for terminal deoxytransferase-mediated uridine triphosphate nick end-labeling (TUNEL) assay to assess the degree of apoptosis, and the kidneys were utilized to determine the extent of influx of CD4(+) and CD8(+) cells and glomerular damage.

RESULTS

Dexamethasone induced a marked apoptosis of splenic CD4(+) and CD8(+) cells, and it inhibited the production of anti-rabbit IgG and the influx of CD8+ cells and macrophages into the renal glomeruli. Crescent formation and excretion of urinary proteins were also reduced. Galectin-9 failed to induce apoptosis in the CD4(+) cells; however, it induced apoptosis in the CD8(+) cells and inhibited the infiltration of CD8(+) cells. Although galectin-1 and -3 did not induce the apoptosis in the T cells, they inhibited the accumulation of macrophages in the renal glomeruli. Like dexamethasone, the galectins also reduced the crescentic formation, proliferation of glomerular cells, and excretion of urinary proteins.

CONCLUSIONS

Galectin-9 selectively induces apoptosis of the activated CD8(+) cells, while the macrophage influx into the kidney is modulated by all three galectins. This finding raises an interesting possibility for the utility of galectins in the modulation of macrophages that are involved in immune-mediated glomerular diseases.

Behavior of lymphocyte subsets and expression of activation markers in response to immunotherapy with galactoside-specific lectin from mistletoe in breast cancer patients

Cellular aspects of the immunomodulating activity of the galactoside-specific lectin from mistletoe (ML-1) were investigated in 10 cancer patients. Regular subcutaneous injections (4 weeks) of the optimal dosis of ML-1 (1 ng per kg body weight, twice a week) yielded notable increases in the apparent numbers of certain lymphocyte subsets [pan T cells; helper T cells; natural killer (NK) cells] which are generally believed to be involved in antitumor immunity. Moreover, ML-1 administration resulted in an increased level of expression of interleukin (IL)2 receptors on lymphatic cells, an indicator of cellular activation. In vitro, the exposure of human lymphocytes to ML-1 resulted in an enhanced expression of receptors for IL-2 (T cells) and HLA-DQ (B cells), which similarly substantiated the capacity of ML-1 to affect immunological parameters within the host defense system. Thorough clinical trials are now required to assess any impact of the application of the lectin on the course of the disease.

Prophylactic effect of Korean mistletoe (Viscum album coloratum) extract on tumor metastasis is mediated by enhancement of NK cell activity

We here demonstrated the prophylactic effect of an extract (KM-110) from Viscum album coloratum, a Korean mistletoe, on tumor metastasis produced by highly metastatic tumor cells, colon 26-M3.1 carcinoma, B16-BL6 melanoma and L5178Y-ML25 lymphoma cells, using experimental models in mice. Intravenous (i.v.) administration of KM-110 (100 microg/mouse) 2 days before tumor inoculation significantly inhibited lung metastasis of B16-BL6 and colon 26-M3.1 cells, and liver and spleen metastasis of L5178Y-ML25 cells. The prophylactic effect of KM-110 on tumor metastasis was evident with various administration routes, i.e. subcutaneous, oral, intranasal as well as i.v., and was dependent upon the dose of KM-110 administered. Furthermore, mice given KM-110 (100 microg) 2 days before tumor inoculation showed significantly prolonged survival rates compared with the untreated mice. In a time course analysis of NK activity, i.v. administration of KM-110 (100 microg) significantly augmented NK cytotoxicity to Yac-a tumor cells from 1 to 3 days after KM-110 treatment. Furthermore, depletion NK cells by injection of rabbit anti-asialo GM1 serum completely abolished the inhibitory effect of KM-110 on lung metastasis of colon 26-M3.1 cells. These results suggest that KM-110 possesses immunopotentiating activity which enhances the host defense system against tumors, and that its prophylactic effect on tumor metastasis is mediated by NK cell activation.

Plant lectins as inhibitors of tumour growth and modulators of host immune response

The antitumour activities of four plant lectins, phytohaemagglutinin, pokeweed mitogen, soybean agglutinin, and wheat germ agglutinin, were evaluated on a murine ascitic lymphoma. The effects of lectin treatment on mitogenic response of peripheral blood lymphocytes and macrophage-mediated tumour cell lysis were also assessed. All four lectins studied were found to be able to restrict tumour growth and to improve the life expectancy of the host. The response of peripheral blood lymphocytes towards mitogenic stimulation was found to be improved and enhancement of tumour cytolysis by peritoneal macrophages was noted following lectin treatment.

Algae-Derived Bioactive Molecules for the Potential Treatment of SARS-CoV-2

The recently emerged COVID-19 disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has adversely affected the whole world. As a significant public health threat, it has spread worldwide. Scientists and global health experts are collaborating to find and execute speedy diagnostics, robust and highly effective vaccines, and therapeutic techniques to tackle COVID-19. The ocean is an immense source of biologically active molecules and/or compounds with antiviral-associated biopharmaceutical and immunostimulatory attributes. Some specific algae-derived molecules can be used to produce antibodies and vaccines to treat the COVID-19 disease. Algae have successfully synthesized several metabolites as natural defense compounds that enable them to survive under extreme environments. Several algae-derived bioactive molecules and/or compounds can be used against many diseases, including microbial and viral infections. Moreover, some algae species can also improve immunity and suppress human viral activity. Therefore, they may be recommended for use as a preventive remedy against COVID-19. Considering the above critiques and unique attributes, herein, we aimed to systematically assess algae-derived, biologically active molecules that could be used against this disease by looking at their natural sources, mechanisms of action, and prior pharmacological uses. This review also serves as a starting point for this research area to accelerate the establishment of anti-SARS-CoV-2 bioproducts.

Lectins as Promising Therapeutics for the Prevention and Treatment of HIV and Other Potential Coinfections

Human immunodeficiency virus-acquired immunodeficiency syndrome (HIV/AIDS) remains a global health problem. Current therapeutics specifically target the viral pathogen at various stages of its life cycle, although complex interactions between HIV and other pathogenic organisms are evident. Targeting HIV and concomitant infectious pathogens simultaneously, both by therapeutic regimens and in prevention strategies, would help contain the AIDS pandemic. Lectins, a ubiquitous group of proteins that specifically bind glycosylated molecules, are interesting compounds that could be used for this purpose, with demonstrated anti-HIV properties. In addition, potential coinfecting pathogens, including other enveloped viruses, bacteria, yeasts and fungi, and protozoa, display sugar-coated macromolecules on their surfaces, making them potential targets of lectins. This review summarizes the currently available findings suggesting that lectins should be further developed to simultaneously fight the AIDS pandemic and concomitant infections in HIV infected individuals.

Lectin conjugates as potent, nonabsorbable CFTR inhibitors for reducing intestinal fluid secretion in cholera

BACKGROUND & AIMS

Inhibitors of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel are predicted to prevent intestinal fluid secretion in cholera. We previously discovered low- affinity glycine hydrazide (GlyH) CFTR inhibitors that block CFTR at its external pore. The goal of this study was to develop potent CFTR inhibitors that are minimally absorbed and washed out of the intestinal lumen for application as antisecretory agents in cholera.

METHODS

GlyH analogs (malonic hydrazides, MalH) were chemically conjugated to various lectins ("MalH-lectin") and purified. CFTR inhibition potency was measured by short-circuit current analysis, mechanism of action by patch-clamp, and antidiarrheal efficacy in closed-loop and suckling mouse models.

RESULTS

By lectin conjugation, we improved CFTR inhibitory potency by approximately 100-fold (to 50 nmol/L) and retarded washout. High-affinity CFTR inhibition was abolished by MalH-lectin heat denaturation, protease digestion, or competition by mannose or unconjugated lectin. Patch-clamp analysis indicated CFTR inhibition by an external pore occlusion mechanism. Fluorescently labeled MalH-lectin remained membrane bound for >6 hours after washout, whereas washout occurred in a few minutes without the lectin. MalH-ConA and MalH-wheat (IC50 50-100 pmol) blocked cholera toxin-induced intestinal fluid secretion in closed intestinal loops in mice and greatly reduced mortality in a suckling mouse model of cholera.

CONCLUSIONS

The high potency of MalH-lectin conjugates results from "anchoring" the CFTR-blocking MalH to cell surface carbohydrates by the lectin. The high-affinity, slow washout, and external site of action of the MalH-lectin conjugates support their further development as antisecretory drugs for enterotoxin-mediated secretory diarrheas.

A Novel Therapeutic Strategy for Pancreatic Cancer: Targeting Cell Surface Glycan Using rBC2LC-N Lectin-Drug Conjugate (LDC)

Various cancers, including pancreatic ductal adenocarcinoma (PDAC), remain intractable even with costly tumor-targeting antibody drugs. Because the outermost coatings of cancer cells are composed of cell-specific glycan layers (glycocalyx), lectins, proteins with glycan-binding potential, were evaluated for possible use as drug carriers in PDAC treatment. A human PDAC cell line with well-to-moderately differentiated properties (Capan-1) was subjected to lectin microarray analysis to identify specific lectin-glycan pairs. The selected lectin was fused with a bacterial exotoxin for the construction of a lectin-drug conjugate (LDC), and its safety and antitumor effects were evaluated. A specific affinity between a recombinant bacterial C-type lectin (rBC2LC-N) and Capan-1 was identified, and its positivity was confirmed in 69 human samples. In contrast to the belief that all lectins mediate harmful hemagglutination, rBC2LC-N did not cause hemagglutination with human erythrocytes and was safely administered to mice. The 50% inhibitory concentration of LDC to Capan-1 (1.04 pg/mL = 0.0195 pmol/L) was 1/1,000 lower than that reported for conventional immunotoxins. The intraperitoneal administration of LDC reduced the tumor weight from 390 to 130.8 mg (P < 0.01) in an orthotopic model and reduced the number of nodules from 48 to 3 (P < 0.001) and improved survival from 62 to 105 days in a peritoneal dissemination model (P < 0.0001). In addition, the effect of LDC was reproduced in nodules from patient-derived PDAC xenografts through intravenous injection. Herein, we show the concept of utilizing lectins as drug carriers to target glycans on the cancer cell surface, highlighting new insights into cancer treatments. Mol Cancer Ther; 17(1); 183-95. ©2017 AACR.

A novel sialic acid-specific lectin from Phaseolus coccineus seeds with potent antineoplastic and antifungal activities

A novel lectin (PCL) with specificity towards sialic acid was purified from Phaseolus coccineus L. (P. multiflorus willd) seeds using ion exchange chromatography on CM and DEAE-Sepharose, and gel filtration on Sephacryl S-200 column. PCL was a homodimer consisting of 29,831.265 Da subunits as determined by gel filtration and MS. Also, PCL was a non-metalloprotein and its N-terminal 23-amino acid sequence, ATETSFSFQRLNLANLVLNKESS, was determined. Subsequently, MTT method, cell morphological analysis and LDH activity-based cytotoxicity assays demonstrated that PCL was highly cytotoxic to L929 cells and induced apoptosis in a dose-dependent manner. Using caspase inhibitors, a typical caspase-dependent pathway was confirmed. PCL also showed remarkable antifungal activity towards some plant pathogenic fungi. Furthermore, when sialic acid-specific activity was fully inhibited, cytotoxicity and antifungal activity were abruptly decreased, respectively, suggesting a significant correlation between sialic acid-specific site and its bi-functional bioactivities.

Advances in Prodrug Design

The background of prodrug design is presented herein as the basis for introducing new and advanced latent systems, taking into account mainly the versatility of polymers and other macromolecules as carriers. PDEPT (Polymer-Directed Enzyme Prodrug Therapy); PELT (Polymer-Enzyme Liposome Therapy); CDS (Chemical Delivery System); ADEPT(Antibody-Directed Enzyme Prodrug Therapy); GDEPT/VDEPT (Gene-Directed Enzyme Prodrug Therapy/Virus-Directed Enzyme Prodrug Therapy); ODDS (Osteotropic Drug Delivery System) and LEAPT (Lectin-directed enzyme-activated prodrug therapy) are briefly described and some examples are given.