Lectins in oncology and virology: Mechanisms of anticancer activity and SARS-CoV-2 inhibition.

Lectins are proteins or glycoproteins of non-immune origin with carbohydrate-binding properties. They are found both prokaryotic and eukaryotic organisms. The most abundant source of the lectins are plants. Many lectins have anticancer effects by directly exerting cytotoxic effects on malignant cells or indirectly activating the immune system. Lectins also have antiviral activities. These proteins can recognise glycoproteins on the surface of enveloped viruses and bind to them. This creates a physical barrier between them and the corresponding receptors on the surface of the host cell, which prevents the virus from entering the cell and can thus effectively inhibit the replication of the virus. In this review, we focus on the anticancer activities of selected lectins and the underlying mechanisms. We also discuss different types of lectins with antiviral activity. We have paid special attention to lectins with inhibitory activity against SARS-CoV-2. Finally, we outline the challenges of using lectins in therapy and suggest future research directions.

Oncolytic vaccinia virus harboring aphrocallistes vastus lectin exerts anti-tumor effects by directly oncolysis and inducing immune response through enhancing ROS in human ovarian cancer.

Aphrocallistes vastus lectin (AVL) is a Ca2+ dependent C-type lectin produced by sponges. Previous studies have demonstrated that oncolytic vaccinia virus harboring AVL (oncoVV-AVL) effectively triggers cell death in various tumors. However, the effects of oncoVV-AVL on human ovarian cancer (OV) remain unknown. This study aims to investigate the mechanism-of-action of oncoVV-AVL in human OV cell lines and in tumor-bearing nude mice. We found that oncoVV-AVL could directly induce apoptosis and autophagy in ovarian cancer cells. Additionally, our results showed that oncoVV-AVL increased the serum levels of mouse IFN-γ (mIFN-γ), leading to the activation of M1-polarized macrophages. Conversely, NADPH, a reducing agent by providing reducing equivalents, reduced the production of mIFN-γ, and suppressed M1-polarization of macrophage. Based on these findings, we propose that oncoVV-AVL not only contributes to direct cytolysis, but also enhances host immune response by promoting ROS levels.

Concanavalin A, lectin from Canavalia ensiformis seeds has Leishmania infantum antipromastigote activity mediated by carbohydrate recognition domain.

Leishmaniases, caused by Leishmania parasites, are widespread and pose significant health risks globally. Visceral leishmaniasis (VL) is particularly prevalent in Brazil, with high morbidity and mortality rates. Traditional treatments, such as pentavalent antimonials, have limitations due to toxicity and resistance. Therefore, exploring new compounds like lectins is crucial. Concanavalin A (ConA) has shown promise in inhibiting Leishmania growth. This study aimed to evaluate its leishmanicidal effect on L. infantum promastigotes and understand its mechanism of action. In vitro tests demonstrated inhibition of promastigote growth when treated with ConA, with IC50 values ranging from 3 to 5 µM over 24-72 h. This study suggests that ConA interacts with L. infantum glycans. Additionally, ConA caused damage to the membrane integrity of parasites and induced ROS production, contributing to parasite death. Scanning electron microscopy confirmed morphological alterations in treated promastigotes. ConA combined with the amphotericin B (AmB) showed synergistic effects, reducing the required dose of AmB, and potentially mitigating its toxicity. ConA demonstrated no cytotoxic effects on macrophages, instead stimulating their proliferation. These findings reinforce that lectin exhibits promising leishmanicidal activity against L. infantum promastigotes, making ConA a potential candidate for leishmaniasis treatment.

ROS Induced by Aphrocallistes vastus Lectin Enhance Oncolytic Vaccinia Virus Replication and Induce Apoptosis in Hepatocellular Carcinoma Cells.

Oncolytic virotherapy is expected to provide a new treatment strategy for cancer. Aphrocallistes vastus lectin (AVL) is a Ca2+-dependent lectin receptor containing the conserved domain of C-type lectin and the hydrophobic N-terminal region, which can bind to the bird's nest glycoprotein and D-galactose. Our previous studies suggested that the oncolytic vaccinia virus (oncoVV) armed with the AVL gene exerted remarkable replication and antitumor effects in vitro and in vivo. In this study, we found that oncoVV-AVL may reprogram the metabolism of hepatocellular carcinoma cells to promote ROS, and elevated ROS subsequently promoted viral replication and induced apoptosis. This study will provide a new theoretical basis for the application of oncoVV-AVL in liver cancer.

The adipokines progranulin and omentin can directly regulate feline ovarian granulosa cell functions.

The aim of the present study was to determine the effects of the adipokines progranulin and omentin on the basic functions of feline ovarian cells. For this purpose, we investigated the effects of the addition of progranulin and omentin (0, 0.1, 1, or 10 ng/ml) on the proliferation (accumulation of PCNA and cyclin B1), apoptosis (accumulation of Bax and caspase 3) and progesterone release of cultured feline ovarian granulosa cells by quantitative immunocytochemistry and enzyme-linked immunosorbent assays (ELISAs). Both progranulin and omentin increased cell proliferation and decreased apoptosis. Both progranulin and omentin promoted progesterone release. The present findings demonstrate that the adipokines progranulin and omentin can directly regulate basic feline ovarian cell functions.

Antimicrobial lipids loaded on lectin display reduced MIC, curtail pathogenesis and protect zebrafish from reinfection by immunomodulation.

Antibiotic resistance and re-emergence of highly resistant pathogens is a grave concern everywhere and this has consequences for all kinds of human activities. Herein, we showed that N-palmitoylethanolamine-derived cationic lipid (cN16E) had a lower minimum inhibitory concentration (MIC) against both Gram-positive and Gram-negative bacteria when it was loaded with Butea monosperma seed lectin (BMSL). The analysis using lectin-FITC conjugate labelling indicated that the improved antibacterial activity of BMSL conjugation was due to bacterial cell surface glycan recognition. Live and dead staining experiments revealed that the BMSL-cN16E conjugate (BcN16E) exerts antibacterial activity by damaging the bacterial membrane. BcN16E antimicrobial activity was demonstrated using an infected zebrafish animal model because humans have 70 % genetic similarity to zebrafish. BcN16E therapeutic potential was established successfully by rescuing fish infected with uropathogenic Escherichia coli (UPEC). Remarkably, the rescued infected fish treated with BcN16E prevented reinfection without further therapy, indicating BcN16E immunomodulatory potential. Thus, the study examined the expression of immune-related genes, including tnfα, ifnγ, il-1ß, il-4, il-10, tlr-2, etc. There was a significant elevation in the expression of all these genes compared to control and fish treated with BMSL or cN16E alone. Interestingly, when the rescued zebrafish were reinfected with the same pathogen, the levels of expression of these genes were many folds higher than seen earlier. Radial immune diffusion analyses (RIA) using zebrafish serum revealed antibody production during the initial infection and treatment. Interestingly, reinfected fish had significant immunoprecipitation in RIA, a feature absent in the groups treated with cN16E, BMSL, and control. These results clearly show that the BcN16E complex not only rescued infected zebrafish but also conferred long-lasting protection in terms of immunomodulation that protects against multiple reinfections. The findings support that BcN16E has immense potential as a novel immunostimulant for various biomedical applications.

Multifunctional Cell Regulation Activities of the Mussel Lectin SeviL: Induction of Macrophage Polarization toward the M1 Functional Phenotype.

SeviL, a galactoside-binding lectin previously isolated from the mussel Mytilisepta virgata, was demonstrated to trigger apoptosis in HeLa ovarian cancer cells. Here, we show that this lectin can promote the polarization of macrophage cell lines toward an M1 functional phenotype at low concentrations. The administration of SeviL to monocyte and basophil cell lines reduced their growth in a dose-dependent manner. However, low lectin concentrations induced proliferation in the RAW264.7 macrophage cell line, which was supported by the significant up-regulation of TOM22, a component of the mitochondrial outer membrane. Furthermore, the morphology of lectin-treated macrophage cells markedly changed, shifting from a spherical to an elongated shape. The ability of SeviL to induce the polarization of RAW264.7 cells to M1 macrophages at low concentrations is supported by the secretion of proinflammatory cytokines and chemokines, as well as by the enhancement in the expression of IL-6- and TNF-α-encoding mRNAs, both of which encode inflammatory molecular markers. Moreover, we also observed a number of accessory molecular alterations, such as the activation of MAP kinases and the JAK/STAT pathway and the phosphorylation of platelet-derived growth factor receptor-α, which altogether support the functional reprogramming of RAW264.7 following SeviL treatment. These results indicate that this mussel ß-trefoil lectin has a concentration-dependent multifunctional role in regulating cell proliferation, phenotype, and death in macrophages, suggesting its possible involvement in regulating hemocyte activity in vivo.

Isolation, characterization and antimicrobial properties of hepatopancreas lectin of the freshwater crab Oziotelphusanaga.

Lectins are versatile proteins that specifically recognize and interact with sugar moieties expressed on the cell surface. The potential of lectin in drug targeting and delivery has instigated interest to identify natural lectins. Crabs have been identified as a rich source of lectin because the innate immune system is activated on encounter of pathogens and helps in the production of lectin. Although the presence of lectins in crab's hemolymph is well documented, little information about lectin in hepatopancreas, a vital organ for immunity and digestion in crustaceans, is currently available. A calcium dependent lectin (75 kDa) was purified from the hepatopancreas of the freshwater crab Oziotelphusa naga by bioadsorption and fetuin linked Sepharose 4B affinity chromatography technique. The isolated hepatopancreas lectin is calcium dependent and maximum agglutination was observed with rabbit erythrocytes. The hemagglutinating activity of the hepatopancreas lectin was effectively inhibited by sugars, such as α-lactose, GlcNAc, trehalose and NeuAc. Compared to sialylated N-glycosylated proteins including transferrin and apo transferrin, sialylated O-glycosylated proteins like fetuin exhibited stronger inhibitory effect. The ability of erythrocytes to bind hepatopancreas lectin has been diminished by desialylation of the potent inhibitor, indicating the significance of sialic acid in lectin-ligand interactions. The purified hepatopancreas lectin showed a broad spectrum of antimicrobial activity against bacteria Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, E. coli and fungi Candida albicans and Aspergillus niger. The findings of this study demonstrate the significance of hepatopancreas lectin as a multifunctional defense protein that inhibits the growth of bacteria and fungi.

In silico discovery and anti-tumor bioactivities validation of an algal lectin from Kappaphycus alvarezii genome.

Lectins are proteins that bind specifically and reversibly to carbohydrates, and some of them have significant anti-tumor activities. Compared to those of lectins from land plants, there are far fewer studies on algal lectins, despite of the high biodiversity of algae. However, canonical strategies based on chromatographic feature-oriented screening cannot satisfy the requirement for algal lectin discovery. In this study, prospecting for novel OAAH family lectins throughout 358 genomes of red algae and cyanobacteria was conducted. Then 35 candidate lectins and 1843 of their simulated mutated forms were virtually screened based on predicted binding specificities to characteristic carbohydrates on cancer cells inferred by a deep learning model. A new lectin, named Siye, was discovered in Kappaphycus alvarezii genome and further verified on different cancer cells. Without causing agglutination of erythrocytes, Siye showed significant cytotoxicity to four human cancer cell lines (IC50 values ranging from 0.11 to 3.95 µg/mL), including breast adenocarcinoma HCC1937, lung carcinoma A549, liver cancer HepG2 and romyelocytic leukemia HL60. And the cytotoxicity was induced through promoting apoptosis by regulating the caspase and the p53 pathway within 24 h. This study testifies the feasibility and efficiency of the genome mining guided by evolutionary theory and artificial intelligence in the discovery of algal lectins.

In vitro antiproliferative effects of Vatairea macrocarpa (Benth.) Ducke lectin on human tumor cell lines and in vivo evaluation of its toxicity in Drosophila melanogaster.

Tumor cells may develop alterations in glycosylation patterns during the initial phase of carcinogenesis. These alterations may be important therapeutic targets for lectins with antitumor action. This work aimed to evaluate the in vitro cytotoxicity of VML on tumor and non-tumor cells (concentration of 25 µg/mL and then microdiluted) and evaluate its in vivo toxicity at different concentrations (1.8, 3.5 and 7.0 µg/mL), using Drosophila melanogaster. Toxicity in D. melanogaster evaluated mortality rate, as well as oxidative stress markers (TBARS, iron levels, nitric oxide levels, protein and non-protein thiols). The cytotoxicity assay showed that VML had cytotoxic effect on leukemic lines HL-60 (IC50 = 3.5 µg/mL), KG1 (IC50 = 18.6 µg/mL) and K562 (102.0 µg/mL). In the toxicity assay, VML showed no reduction in survival at concentrations of 3.5 and 7.0 µg/mL and did not alter oxidative stress markers at any concentrations tested. Cytotoxicity of VML from HL-60, KG1 and K562 cells could arise from the interaction between the lectin and specific carbohydrates of tumor cells. In contrast, effective concentrations of VML against no-tumor cells human keratinocyte - HaCat and in the D. melanogaster model did not show toxicity, suggesting that VML is a promising molecule in vivo studies involving leukemic cells.

Modulation of Campylobacter jejuni adhesion to biotic model surfaces by fungal lectins and protease inhibitors.

Campylobacter jejuni, a Gram-negative bacterium, is one of the most common causes of foodborne illness worldwide. Its adhesion mechanism is mediated by several bacterial factors, including flagellum, protein adhesins, lipooligosaccharides, proteases, and host factors, such as surface glycans on epithelial cells and mucins. Fungal lectins, specialized carbohydrate-binding proteins, can bind to specific glycans on host and bacterial cells and thus influence pathogenesis. In this study, we investigated the effects of fungal lectins and protease inhibitors on the adhesion of C. jejuni to model biotic surfaces (mucin, fibronectin, and collagen) and Caco-2 cells as well as the invasion of Caco-2 cells. The lectins Marasmius oreades agglutinin (MOA) and Laccaria bicolor tectonin 2 (Tec2) showed remarkable efficacy in all experiments. In addition, different pre-incubations of lectins with C. jejuni or Caco-2 cells significantly inhibited the ability of C. jejuni to adhere to and invade Caco-2 cells, but to varying degrees. Pre-incubation of Caco-2 cells with selected lectins reduced the number of invasive C. jejuni cells the most, while simultaneous incubation showed the greatest reduction in adherent C. jejuni cells. These results suggest that fungal lectins are a promising tool for the prevention and treatment of C. jejuni infections. Furthermore, this study highlights the potential of fungi as a rich reservoir for novel anti-adhesive agents.

Lectibodies as antivirals.

Growing concerns regarding the emergence of highly transmissible viral diseases highlight the urgent need to expand the repertoire of antiviral therapeutics. For this reason, new strategies for neutralizing and inhibiting these viruses are necessary. A promising approach involves targeting the glycans present on the surfaces of enveloped viruses. Lectins, known for their ability to recognize specific carbohydrate molecules, offer the potential for glycan-targeted antiviral strategies. Indeed, numerous studies have reported the antiviral effects of various lectins of both endogenous and exogenous origins. However, many lectins in their natural forms, are not suitable for use as antiviral therapeutics due to toxicity, other unfavorable pharmacological effects, and/or unreliable manufacturing sources. Therefore, improvements are crucial for employing lectins as effective antiviral therapeutics. A novel approach to enhance lectins' suitability as pharmaceuticals could be the generation of recombinant lectin-Fc fusion proteins, termed "lectibodies." In this review, we discuss the scientific rationale behind lectin-based antiviral strategies and explore how lectibodies could facilitate the development of new antiviral therapeutics. We will also share our perspective on the potential of these molecules to transcend their potential use as antiviral agents.

Omentin reduces venous neointimal hyperplasia in arteriovenous fistula through hypoxia-inducible factor-1 alpha inhibition.

Arteriovenous fistula (AVF) failure often involves venous neointimal hyperplasia (VNH) driven by elevated hypoxia-inducible factor-1 alpha (HIF-1α) in the venous wall. Omentin, known for its anti-inflammatory and anti-hyperplasia properties, has an uncertain role in early AVF failure. This study investigates omentin's impact on VNH using a chronic renal failure (CRF) rabbit model. The CRF rabbit model of AVF received omentin-expressing adenoviral vector or control ß-gal vector to assess omentin's effects on VNH. Human vascular smooth muscle cells (HVSMCs), stimulated with tumor necrosis factor-α (TNF-α), were exposed to recombinant human omentin (Rh-OMT) to study its influence on cell proliferation and migration. The AMP-activated protein kinase (AMPK) inhibitor compound C and the mammalian target of rapamycin (mTOR) activator MHY1485 were employed to explore omentin's mechanisms in VNH reduction through HIF-1α inhibition. Omentin treatment reduced VNH in CRF rabbits, concomitant with HIF-1α down-regulation and the suppression of downstream factors, including vascular endothelial growth factor and matrix metalloproteinases. Rh-OMT inhibited TNF-α-induced HVSMC proliferation and migration by modulating both cell cycle and cell adhesion proteins. Additionally, omentin reduced HIF-1α expression through the AMPK/mTOR pathway activation. Notably, the blockade of AMPK/mTOR signaling reversed omentin-mediated inhibition of VNH, cell proliferation, and migration, both in vivo and in vitro. In conclusion, omentin mitigates VNH post-AVF creation by restraining HIF-1α via AMPK/mTOR signaling. Strategies boosting circulating omentin levels may offer promise in averting AVF failure.

A Complex-Type N-Glycan-Specific Lectin Isolated from Green Alga Halimeda borneensis Exhibits Potent Anti-Influenza Virus Activity.

Marine algal lectins specific for high-mannose N-glycans have attracted attention because they strongly inhibit the entry of enveloped viruses, including influenza viruses and SARS-CoV-2, into host cells by binding to high-mannose-type N-glycans on viral surfaces. Here, we report a novel anti-influenza virus lectin (named HBL40), specific for complex-type N-glycans, which was isolated from a marine green alga, Halimeda borneensis. The hemagglutination activity of HBL40 was inhibited with both complex-type N-glycan and O-glycan-linked glycoproteins but not with high-mannose-type N-glycan-linked glycoproteins or any of the monosaccharides examined. In the oligosaccharide-binding experiment using 26 pyridylaminated oligosaccharides, HBL40 only bound to complex-type N-glycans with bi- and triantennary-branched sugar chains. The sialylation, core fucosylation, and the increased number of branched antennae of the N-glycans lowered the binding activity with HBL40. Interestingly, the lectin potently inhibited the infection of influenza virus (A/H3N2/Udorn/72) into NCI-H292 cells at IC50 of 8.02 nM by binding to glycosylated viral hemagglutinin (KD of 1.21 × 10-6 M). HBL40 consisted of two isolectins with slightly different molecular masses to each other that could be separated by reverse-phase HPLC. Both isolectins shared the same 16 N-terminal amino acid sequences. Thus, HBL40 could be useful as an antivirus lectin specific for complex-type N-glycans.

Maackia amurensis seed lectin (MASL) and soluble human podoplanin (shPDPN) sequence analysis and effects on human oral squamous cell carcinoma (OSCC) cell migration and viability.

Maackia amurensis lectins serve as research and botanical agents that bind to sialic residues on proteins. For example, M. amurensis seed lectin (MASL) targets the sialic acid modified podoplanin (PDPN) receptor to suppress arthritic chondrocyte inflammation, and inhibit tumor cell growth and motility. However, M. amurensis lectin nomenclature and composition are not clearly defined. Here, we sought to definitively characterize MASL and its effects on tumor cell behavior. We utilized SDS-PAGE and LC-MS/MS to find that M. amurensis lectins can be divided into two groups. MASL is a member of one group which is composed of subunits that form dimers, evidently mediated by a cysteine residue in the carboxy region of the protein. In contrast to MASL, members of the other group do not dimerize under nonreducing conditions. These data also indicate that MASL is composed of 4 isoforms with an identical amino acid sequence, but unique glycosylation sites. We also produced a novel recombinant soluble human PDPN receptor (shPDPN) with 17 threonine residues glycosylated with sialic acid moieties with potential to act as a ligand trap that inhibits OSCC cell growth and motility. In addition, we report here that MASL targets PDPN with very strong binding kinetics in the nanomolar range. Moreover, we confirm that MASL can inhibit the growth and motility of human oral squamous cell carcinoma (OSCC) cells that express the PDPN receptor. Taken together, these data characterize M. amurensis lectins into two major groups based on their intrinsic properties, clarify the composition of MASL and its subunit isoform sequence and glycosylation sites, define sialic acid modifications on the PDPN receptor and its ability to act as a ligand trap, quantitate MASL binding to PDPN with KD in the nanomolar range, and verify the ability of MASL to serve as a potential anticancer agent.

Structural and functional analysis of Cyanovirin-N homologs: Carbohydrate binding affinities and antiviral potential of cyanobacterial peptides.

Cyanobacteria, a group of photosynthetic prokaryotes, can sinthesize several substances due to their secondary metabolism, with notable properties, such as Cyanovirin-N(CVN), a carbohydrate-binding lectin, that exhibits antiviral activity against several pathogens, due to its ability to bind viral surface carbohydrates such as mannose, thus interfering with the viral entry on the cell. CVN has been described in several cyanobacterial strains and shows biotechnological potential for the development of drugs of pharmaceutical interest. This study focuses on the genomic exploration and characterization of Cyanovirin-N homologs to assess the conservation of carbohydrate-binding affinity within the group. The analysis of their antiviral properties was carried out using bioinformatics tools to study protein models through an in silico pipeline, following the steps of genomic prospection on public databases, homology modeling, docking, molecular dynamics and energetic analysis. Mannose served as the reference ligand, and the lectins' binding affinity with mannose was assessed across Cyanovirin-N homologs. Genomic mining identified 33 cyanobacterial lectin sequences, which underwent structural and functional characterization. The results obtained from this work indicate strong carbohydrate affinity on several homologs, pointing to the conservation of antiviral properties alongside the group. However, this affinity was not uniformly distributed among sequences, exhibiting significant heterogeneity in binding site residues, suggesting potential multi-ligand binding capabilities on the Cyanovirin-N homologs group. Studies focused on the properties involved in these molecules and the investigation of the genetic diversity of Cyanovirin-N homologs could provide valuable insights into the discovery of new drug candidates, harvesting the potential of bioinformatics for large-scale functional and structural analysis.

A Review of the Leishmanicidal Properties of Lectins.

Lectins are proteins widely distributed among plants, animals and microorganisms that have the ability to recognize and interact with specific carbohydrates. They have varied biological activities, such as the inhibition of the progression of infections caused by fungi, bacteria, viruses and protozoa, which is related to the interaction of these proteins with the carbohydrates present in the cell walls of these microorganisms. Leishmaniasis are a group of endemic infectious diseases caused by protozoa of the genus Leishmania. In vitro and in vivo tests with promastigotes and amastigotes of Leishmania demonstrated that lectins have the ability to interact with glycoconjugates present on the cell surface of the parasite, it prevents their development through various mechanisms of action, such as the production of ROS and alteration of membrane integrity, and can also interact with defense cells present in the human body, thus showing that these molecules can be considered alternative pharmacological targets for the treatment of leishmaniasis. The objective of the present work is to carry out a bibliographic review on lectins with leishmanicidal activity, emphasizing the advances and perspectives of research in this theme. Through the analysis of the selected studies, we were able to conclude that lectins have great potential for inhibiting the development of leishmaniasis. However, there are still few studies on this subject.

New l-Rhamnose-Binding Lectin from the Bivalve Glycymeris yessoensis: Purification, Partial Structural Characterization and Antibacterial Activity.

In this study, a new l-rhamnose-binding lectin (GYL-R) from the hemolymph of bivalve Glycymeris yessoensis was purified using affinity and ion-exchange chromatography and functionally characterized. Lectin antimicrobial activity was examined in different ways. The lectin was inhibited by saccharides possessing the same configuration of hydroxyl groups at C-2 and C-4, such as l-rhamnose, d-galactose, lactose, l-arabinose and raffinose. Using the glycan microarray approach, natural carbohydrate ligands were established for GYL-R as l-Rha and glycans containing the α-Gal residue in the terminal position. The GYL-R molecular mass determined by MALDI-TOF mass spectrometry was 30,415 Da. The hemagglutination activity of the lectin was not affected by metal ions. The lectin was stable up to 75 °C and between pH 4.0 and 12.0. The amino acid sequence of the five GYL-R segments was obtained with nano-ESI MS/MS and contained both YGR and DPC-peptide motifs which are conserved in most of the l-rhamnose-binding lectin carbohydrate recognition domains. Circular dichroism confirmed that GYL is a α/ß-protein with a predominance of the random coil. Furthermore, GYL-R was able to bind and suppress the growth of the Gram-negative bacteria E. coli by recognizing lipopolysaccharides. Together, these results suggest that GYL-R is a new member of the RBL family which participates in the self-defense mechanism against bacteria and pathogens with a distinct carbohydrate-binding specificity.

Lectin activity in mycelial extracts of Fusarium species

ABSTRACT Lectins are non-immunogenic carbohydrate-recognizing proteins that bind to glycoproteins, glycolipids, or polysaccharides with high affinity and exhibit remarkable ability to agglutinate erythrocytes and other cells. In the present study, ten Fusarium species previously not explored for lectins were screened for the presence of lectin activity. Mycelial extracts of F. fujikuroi, F. beomiformii, F. begoniae, F. nisikadoi, F. anthophilum, F. incarnatum, and F. tabacinum manifested agglutination of rabbit erythrocytes. Neuraminidase treatment of rabbit erythrocytes increased lectin titers of F. nisikadoi and F. tabacinum extracts, whereas the protease treatment resulted in a significant decline in agglutination by most of the lectins. Results of hapten inhibition studies demonstrated unique carbohydrate specificity of Fusarium lectins toward O-acetyl sialic acids. Activity of the majority of Fusarium lectins exhibited binding affinity to D-ribose, L-fucose, D-glucose, L-arabinose, D-mannitol, D-galactosamine hydrochloride, D-galacturonic acid, N-acetyl-d-galactosamine, N-acetyl-neuraminic acid, 2-deoxy-D-ribose, fetuin, asialofetuin, and bovine submaxillary mucin. Melibiose and N-glycolyl neuraminic acid did not inhibit the activity of any of the Fusarium lectins. Mycelial extracts of F. begoniae, F. nisikadoi, F. anthophilum, and F. incarnatum interacted with most of the carbohydrates tested. F. fujikuroi and F. anthophilum extracts displayed strong interaction with starch. The expression of lectin activity as a function of culture age was investigated. Most species displayed lectin activity on the 7th day of cultivation, and it varied with progressing of culture age.

Lectin, hemolysin and protease inhibitors in seed fractions with ovicidal activity against Haemonchus contortus / Lectina, hemolisina e inibidores de protease em frações de sementes com atividade ovicida contra Haemonchus contortus

Bioactive molecules of plant species are promising alternatives for the chemical control of gastrointestinal nematodes in ruminants. Extracts of native and exotic seed species from Brazil's semi-arid region were tested in vitro in an egg hatch assay and the bioactivity of their proteins was investigated. Each seed species was subjected to three extractions with three types of solvents. All the seeds showed ovicidal activity, which varied according to the solvents. Higher ovicidal activity was found in the molecule fractions of low molecular weight (<12 kDa) for Albizia lebbeck, Ipomoea asarifolia, Jatropha curcas, Libidibia ferrea, Moringa oleifera and Ricinus communis (P<0.05, Bonferroni test). The two fractions of Crotalaria spectabilis showed the same ovicidal activity (P>0.05, Bonferroni test). Hemagglutinating activity was detected in the fractions of C. spectabilis and M. oleifera fractions, hemolysin activity in the A. lebbeck and M. oleifera fractions, serine protease inhibitory activity in the A. lebbeck, I. asarifolia, J. curcas, M. oleifera and R. communis fractions, cysteine protease inhibitor activity in the M. oleifera fraction, and no protein activity in the L. ferrea fraction. The results of this work reveal new plant species with a potential for use in controlling nematode parasites in goats, thus opening a new field of research involving plant protein molecules with ovicidal properties.

Moléculas bioativas de espécies vegetais são alternativas promissoras ao controle químico dos nematoides gastrintestinais em ruminantes. Extratos de sementes de espécies nativas e exóticas do Semiárido Brasileiro foram testados in vitro em ensaio de eclosão de ovos e investigada a natureza proteica da bioatividade. Três extrações com três solventes foram feitas para cada semente estudada. Todas as sementes apresentaram atividade ovicida, variando com o solvente utilizado. Maior taxa de inibição da eclosão concentrou-se nas frações de moléculas de baixa massa molecular (<12 kDa) para Albizia lebbeck, Ipomoea asarifolia, Jatropha curcas, Libidibia ferrea, Moringa oleifera e Ricinus communis (P<0,05, teste de Bonferroni). Crotalaria spectabilis mostrou atividade nas duas frações, sem diferença entre elas (P>0,05, teste de Bonferroni). Observou-se atividade hemaglutinante nas frações de C. spectabilis e M. oleifera, de hemolisina em A. lebbeck e M. oleifera, de atividade inibidora de protease da serina em A. lebbeck, I. asarifolia, J. curcas, M. oleifera e R. communis, de atividade inibidora de protease da cisteína em M. oleifera e nenhuma atividade proteica na fração de L. ferrea. Os resultados revelaram novas espécies botânicas com potencial de controle de nematoides em caprinos e um novo campo de pesquisa, o estudo de moléculas de origem proteica com atividade ovicida.