In vitro assessment of dual (antiviral and antitumor) activity of a novel lectin produced by the newly cyanobacterium isolate, Oscillatoria acuminate MHM-632 MK014210.1.

A novel lectin was purified from newly cyanobacterium isolate, Oscillatoria acuminate MHM-632 MK014210.1 using affinity chromatography with a molecular weight of 120 kDa under native-PAGE and 30 kDa on reducing-PAGE, represented tetramer nature of this lectin. Oscillatorial lectin showed stability at 60 °C for 30 min, pH-dependent, with the highest activities over the pH range of 6-8, and required zinc ions to express its full activity. Oscillatorial lectin is a glycan-binding protein with a neutral carbohydrate content of 7.0% as evaluated by the phenol-sulfuric acid method. Polyols and α- glycosides polymer of mannose sugar or sugars alcohol were completely inhibited oscillatorial lectin with MIC of 0.195 mM, while ß-glycosides sugars did not show any inhibition effect. The oscillatorial lectin has anti-proliferative activity against Huh-7 and MCF-7 cancer cells and inhibited their proliferation with EC50 values of 106.75 µg/ml and 254.14 µg/ml, respectively. Besides the anticancer effect, oscillatorial lectin also has potent antiviral activity against HSV-1 in a dose-dependent manner via virions neutralization and inhibition of viral replication with IC50 values of 90.95 ng/ml and 131.3 ng/ml, respectively. The unique carbohydrate affinity of oscillatorial lectin provides insight into its use as a promising candidate in many biotechnological applications, like fighting viral infection and combating cancer disease.Communicated by Ramaswamy H. Sarma.

Assessment of Sauromatum guttatum lectin toxicity against Bactrocera cucurbitae.

Lectins are proteins that bind specifically to foreign glycans. Due to this binding property, these molecules have potential application as bioinsecticidal tools replacing conventional chemical insecticides. The present study involved purification of phytolectin from the tubers of Sauromatum guttatum by affinity chromatography on asialofetuin-linked silica matrix. The purity of the sample was checked by SDS-PAGE at pH 8.3. Purified lectin was incorporated in the artificial diet of a Dipteran model, Bactrocera cucurbitae at different concentrations (10, 20, 40, 60 and 80 µgml(-1)). The lectin significantly affected various developmental parameters that were studied. Percentage pupation and percentage emergence was reduced to 44 % and 7.9%, respectively, at 80 µgml(-1) concentration as compared to control (100%). LC50 of Sauromatum guttatum lectin was calculated to be 19.42 µgml(-1). Treatment of insect larvae with LC50 of Sauromatum guttatum lectin suppressed the activity of hydrolytic enzymes (esterases and acid phosphatases) and oxidative enzymes (superoxide dismutase and glutathione-S-transferase). Thus, with low LC50 and high mortality (approximately 92% at 80 µgml(-1)) of the insect larvae, Sauromatum guttatum lectin offers a possibility to engineer crop plants for improved and safer agriculture.

[Comparative assessment of inductive effects of Azospirillum lectins with different antigenic properties on the signal systems of wheat seedling roots].

The lectins of associative nitrogen-fixing bacteria Azospirillum brasilense Sp7 and its mutant A. brasilense Sp7.2.3 were shown to have different effects on the components of the wheat seedling root signal system, namely to regulate the levels of cAMP, nitric oxide, diacylglycerol, and salicylic acid, as well as to induce the activities of superoxide dismutase and lipoxygenase. Our results make it possible to consider azospirilla lectins as inducers of the signal systems in wheat seedling roots, since they cause development of several flows of primary signals. These data are of general biological importance, since lectins are present in all living organisms and most ot the functions of lectins remain insufficiently understood.

Lectins offer new perspectives in the development of macrophage-targeted therapies for COPD/emphysema.

We have previously shown that the defective ability of alveolar macrophages (AM) to phagocytose apoptotic cells ('efferocytosis') in chronic obstructive pulmonary disease/emphysema (COPD) could be therapeutically improved using the C-type lectin, mannose binding lectin (MBL), although the exact mechanisms underlying this effect are unknown. An S-type lectin, galectin-3, is also known to regulate macrophage phenotype and function, via interaction with its receptor CD98. We hypothesized that defective expression of galectin/CD98 would be associated with defective efferocytosis in COPD and that mechanisms would include effects on cytoskeletal remodeling and macrophage phenotype and glutathione (GSH) availability. Galectin-3 was measured by ELISA in BAL from controls, smokers and current/ex-smokers with COPD. CD98 was measured on AM using flow cytometry. We assessed the effects of galectin-3 on efferocytosis, CD98, GSH, actin polymerisation, rac activation, and the involvement of PI3K (using ß-actin probing and wortmannin inhibition) in vitro using human AM and/or MH-S macrophage cell line. Significant decreases in BAL galectin-3 and AM CD98 were observed in BAL from both current- and ex-smoker COPD subjects vs controls. Galectin 3 increased efferocytosis via an increase in active GTP bound Rac1. This was confirmed with ß-actin probing and the role of PI3K was confirmed using wortmannin inhibition. The increased efferocytosis was associated with increases in available glutathione and expression of CD98. We provide evidence for a role of airway lectins in the failed efferocytosis in COPD, supporting their further investigation as potential macrophage-targeted therapies.

Assessment of plant lectin antifungal potential against yeasts of major importance in medical mycology.

The search for new compounds with antifungal activity is accelerating due to rising yeast and fungal resistance to commonly prescribed drugs. Among the molecules being investigated, plant lectins can be highlighted. The present work shows the potential of six plant lectins which were tested in vitro against yeasts of medical importance, Candida albicans, Candida tropicalis, Candida parapsilosis, Cryptococcus gattii, Cryptococcus neoformans, Malassezia pachydermatis, Rhodotorula sp. and Trichosporon sp. Broth microdilution susceptibility testing was performed in accordance with standard protocols to evaluate antifungal activity. Minimum inhibitory concentration (MIC) was determined at 80% yeast growth inhibition, whereas the minimum fungicidal concentration (MFC) was evaluated after making the subcultures of each dilution. Only C. parapsilosis growth was inhibited by the lectins tested. Abelmoschus esculentus lectin showed the highest MIC (0.97 µg ml(-1)). Lectins from Canavalia brasiliensis, Mucuna pruriens and Clitoria fairchildiana presented the highest MFC at (3.90 µg ml(-1)). These results encourage further studies with wider yeast strain selections, and open new perspectives for the development of pharmacological molecules.

A ConA-like lectin from Dioclea guianensis Benth. has antifungal activity against Colletotrichum gloeosporioides, unlike its homologues, ConM and ConA.

This study reports on the antifungal activity of Dgui, a ConA-like lectin from Dioclea guianensis seeds. Dgui inhibited conidial germination but not mycelial growth of Colletotrichum gloeosporioides. The lectins ConA and ConM from Canavalia ensiformis and Canavalia maritima, respectively, share high levels of amino acid sequence similarity (>84%) with Dgui and have the same specificity toward glucose/mannose but had no effect on the fungus. Fluorescence microscopy showed that both Dgui and ConM bind to C. gloeosporioides ungerminated conidia. However, Dgui did not bind to C. gloeosporioides germinated conidia and germ tubes and was not inhibitory to mycelial growth. Because only Dgui inhibited germination of the fungus, C. gloeosporioides conidia might have surface-specific germination targets recognized by Dgui but not by its homologues, ConM and ConA. Therefore, Dgui is a candidate for biotechnological approaches for improving the resistance of various nutritionally and commercially important crops that are affected by C. gloeosporioides.

Mechanisms and assessment of lectin-mediated mitogenesis.

The discovery of lectin-mediated mitogenesis by Nowell in 1960 stimulated interest in the properties of lectins while advancing knowledge of immunology. Although some lectins are polyclonal activators both in vitro and in vivo, others may display a broad range of activities toward human lymphocytes. Indeed, the same lectin (e.g., wheat germ agglutinin or Datura lectin) may be mitogenic, comitogenic, or antimitogenic, depending on the experimental conditions. An individual lectin may bind to several glycoproteins on the lymphocyte surface, resulting in interactions that may or may not be functionally relevant, and that may have opposing effects. Studies with lectins and with monoclonal antibodies (MAbs) have established that a surprisingly large variety of cell-surface molecules can influence the initiation and regulation of lymphocyte activation and proliferation. Interactions between lymphocytes and accessory cells are crucial; some signals are cell-mediated, but others depend on soluble cytokines. Mitogenic lectins presumably bind to the T-cell receptor complex and also promote a positive costimulatory signal leading to the synthesis of interleukin 2 and interleukin 2 receptors (IL-2R). Nonmitogenic, comitogenic, and antimitogenic lectin activities also probably act via accessory molecules involved in costimulation. Plant lectin-animal lymphocyte interactions presumably have no physiological significance, but it is suggested that the former mimics microbial superantigens, which may function in the colonization of host cells. Mitogenic stimulation of lymphocytes can be assessed in several ways. The standard technique measures [3H]-thymidine incorporation into DNA, but nonradioactive procedures are also available.

Surface modification of guinea pig sperm during in vitro capacitation: an assessment using lectin-induced agglutination of living sperm.

Plant lectins have been used to advantage to study carbohydrate-containing cell surface receptors in numerous systems. In this study, a simple, reliable assay was developed to quantitate lectin-induced agglutinability of sperm. This assay was used successfully to compare some of the surface properties of uncapacitated and capacitated guinea pig sperm. Capacitation was induced by incubating sperm in minimum capacitation medium (MCM) or modified Tyrodes solution (T-PL). Control incubations were done in Ham's F-10 or Hank's balanced salt solution which do not support capacitation. At timed intervals during incubation, sperm samples were assessed for pattern and degree of lectin-induced agglutination. Results establish that: (1) soybean agglutinin (SBA) and to a lesser extent concanavalin A (Con A) induced agglutinability of guinea pig sperm increase during in vitro capacitation in MCM; (2) a similar increase in SBA induced agglutinability occurs during capacitation in T-PL, but not in the non-capacitating media; and (3) for sperm incubated in MCM or T-PL, there is a significant increase in tail to tail agglutination after capacitation. The results with SBA demonstrate that D-galactose and/or N-acetyl-D-galactosamine containing receptor sites or the guinea pig sperm surface are affected by capacitation, and this effect occurs, at least in part, in the sperm tail. Possible explanations for the observed increase in agglutinability are discussed. The agglutination assay may prove useful as a direct test for the occurrence of capacitation and may be especially valuable for species having a small acrosome or limited number of eggs.

An assessment of cell-mediated immunity in acute allograft rejection in man. A prospective study.

A detailed multifactorial computer analysis of several in vitro tests of cell-mediated immunity has been carried out before and after surgery in 15 renal transplant recipients. Factors studied include lymphocyte blastogenesis, T- and B-cell levels, and lymphocyte protein synthesis. Large doses of immunosuppressive agents chnage lymphocyte subpopulations. This is seen especially in transplant patients who have rejection and who have decreased numbers of circulating lymphocytes. The T cells are selectively depressed more than the B cells. This is also reflected in the greater responsiveness of pokeweed mitogen-stimulated lymphocytes compared with lymphocyte responsiveness to phytohemagglutinin and concanavalin A. In this environment, rejection takes place. These observations suggest that rejection may be initiated by cortisone-resistant lymphocytes of the thymic medullary type. Measurements of changes in lymphocyte responsiveness to mitogens or changes in lymphocyte subpopulations do not reliably predict rejection. However, measurement of lymphocyte protein synthesis fills the criterion of providing a reliable test that can be carried out quickly, and in the future may be valuable in predicting rejection.

Electron microscope assessment of fertilization of rabbit ova treated with concanavalin A and wheat germ agglutinin.

Zonaless rabbit ova, exposed to Concanavalin A or Wheat Germ Agglutinin, then to uterine capacitated sperm produce pronuclear, 2 and 4 stage embryos that are indistinguishable from controls. Absence of cortical granules indicates that the ova were fertilized and not merely activated. Survival of lectin-bearing receptors during the period necessary for fertilization was evaluated in ova marked with ferritin-conjugated lectin.