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Lectins are present in almost all living organisms and are involved in several biological processes, including immune responses. In the present study, a galactose binding lectin (SsGBL) exhibiting an apparent MW of 43 kDa has been characterized and purified from the mucus of the polichaete Sabella spallanzanii

The phylum of Cnidaria is one of the first branches in the tree of animal life to provide crucial insights on the evolution of immunity. Cnidarians are diblastic aquatic animals with radial symmetry and they are the simplest multicellular organisms that have reached the level of tissue organization. The renewed interest in the study of immunity in Cnidaria has led to additional information to the scenario of the first stages of immunity evolution revealing the cellular processes involved in symbiosis, in the regulation of homeostasis and in the fight against infections. We investigated the inflammatory response in Cnidarian following injection of various substances different in type and dimension, and observed clear, strong and specific reactions especially after injection of bacteria. The enzymes evaluation (protease, phosphatase and esterase), showing how the injection of different bacterial strains alters the expression of these enzymes suggesting a correlation between the appearance of the inflammatory reaction and the modification of enzymatic activities. The Cnidaria phylum has evolved using biotoxins as defense or predation mechanisms for ensure survival in hostile and competitive environments such as the seas and oceans indeed the tissues and the mucus produced by cnidarians are involved in immune defense and contain a large variety of toxins such enzymes, potent pore forming toxins, and neurotoxins. They could also take advantage of the multi-functionality of some of their toxins. The bioactive molecules were characterized and purified by biological assays, acid extraction, HPLC purifications, mass spectroscopy and peptide synthesis. Here, we show the cnidarian bioactive molecules as antimicrobial peptides and enzymes in order to draw important applications in fields ranging from pharmacology to cultural heritage.

Lectins are present in almost all living organisms and are involved in several biological processes, including immune responses. In the present study, a calcium dependent galactose-binding lectin exhibiting an apparent MW of 43 kDa has been characterized and purified from the mucus of the polychaete Sabella spallanzanii by using both affinity chromatography and high-pressure liquid chromatographic methods. Its agglutinating activity towards rabbit erythrocytes was significantly modified by the addition of calcium or EDTA. The activity was optimal at temperature values comprised between 4 and 18 °C, maintain a 50% of activity between 20 and 37 °C, was significant deleted after exposure at 50 °C, and was depleted at 90 °C. The S. spallanzanii Galactose-Binding Lectin (SsGBL) was able to agglutinate bacteria and to preferentially recognize Gram-negative bacteria. The strongest agglutinating activity was observed towards Vibrio alginolyticus and Escherichia coli, by contrast mucus agglutinated in a lesser extent both Aeromonas hydrophyla and the Gram-positive Micrococcus lysodeikticus thus suggesting its involvement in host pathogen interactions., Invertebrate Survival Journal, Vol 16 No 1 (2019)

Recently described biochemical and structural aspects of fucose-binding lectins from the European eel (Anguilla anguilla) and striped bass (Morone saxatilis) led to the identification of a novel lectin family ("F-type" lectins) characterized by a unique sequence motif and a characteristic structural fold. The F-type fold is shared not only with other members of this lectin family, but also with apparently unrelated proteins ranging from prokaryotes to vertebrates. Here we describe the purification, biochemical and molecular properties, and the opsonic activity of an F-type lectin (DlFBL) isolated from sea bass (Dicentrarchus labrax) serum. DlFBL exhibits two tandemly arranged carbohydrate-recognition domains that display the F-type sequence motif. In situ hybridization and immunohistochemical analysis revealed that DlFBL is specifically expressed and localized in hepatocytes and intestinal cells. Exposure of formalin-killed Escherichia coli to DlFBL enhanced their phagocytosis by D. labrax peritoneal macrophages relative to the unexposed controls, suggesting that DlFBL may function as an opsonin in plasma and intestinal mucus.

The evolution of multicellular organisms was marked by adaptations to protect against pathogens. The mechanisms for discriminating the ’’self’’ from ’’non-self” have evolved into a long history of cellular and molecular strategies, from damage repair to the co-evolution of host-pathogen interactions. We investigated the inflammatory response in Anemonia sulcata (Cnidaria: Anthozoa) following injection of substances that varied in type and dimension, and observed clear, strong and specific reactions, especially after injection of Escherichia coli and Vibrio alginolyticus. Moreover, we analyzed enzymatic activity of protease, phosphatase and esterase, showing how the injection of different bacterial strains alters the expression of these enzymes and suggesting a correlation between the appearance of the inflammatory reaction and the modification of enzymatic activities. Our study shows for the first time, a specific reaction and enzymatic responses following injection of bacteria in a cnidarian.

We investigated the haemolytic capacity of the crude venom extracted from isolated nematocysts of Pelagia noctiluca (Cnidaria: Scyphozoa), and evidenced the proteic fractions responsible for this activity. The nematocyst venom was used at various concentrations to evaluate the haemolytic activity and the lysosomal membrane stability of red blood cells of two teleostean species treated with the extract. The nematocyst extract was assayed against erythrocytes of the two teleostean species living in different environments, Carassius auratus as a common freshwater species, and Liza aurata as a representative of seawater species. Experiments on the haemolytic activity of P. noctiluca in the presence of lipid components of erythrocyte membranes showed that sphyngomyelin strongly inhibited this activity. The crude venom was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis SDS-PAGE and high performance liquid chromatography (HPLC) to detect the proteic composition, and it was found that the active haemolytic components of this venom are distributed in at least four protein fractions. The results of our experiments indicated that Pelagia noctiluca venom induces haemolysis and lysosomal membrane destabilisation in both species and that Carassius auratus was more susceptible to jellyfish venom than was Liza aurata. No significant differences in glutathione (GSH) levels were observed between control and treatments; consequently the toxins do not cause the oxidative stress but likely recognize specific targets (i.e. sphyngomyelin) in the plasmatic membrane of red blood cells.

The study of cnidarians immunity, as model systems of metazoans, lead additional informations on the first steps of the immunity evolution. The functions of the genes and cellular pathways in higher vertebrates are conserved during the evolution of metazoans, as shown by the discovery of homologues in cnidarians. These basal metazoans in fact, are far from "simples" in the range of methods at their disposal to deal with potential prey but also invading microbes and pathogens. They can give informations about the invertebrates innate immune repertoire. We investigated the immunobiology starting from the inflammatory response in Anemonia sulcata (Cnidaria: Anthozoa) following injection of substances different in type and dimension, to understand the effector mechanisms involved in this process. We observed clear, strong and specific reactions especially after injection of bacteria and the alteration of the expression of enzymes (protease, phosphatase and esterase), showing a correlation between the appearance of the inflammatory reaction and the modification of enzymatic activities. From cnidarian phylum a large number of toxic compounds have been isolated. Tissues and mucus produced by cnidarians may have a role in immune defense and contain a variety of toxins as neurotoxins, cytolysins and antimicrobial peptides, which can have multifunctional role. The bioactive molecules were purified by acid extraction and HPLC purifications and characterized through biological assays, mass spectroscopy and peptide synthesis. Here, we show the cnidarian bioactive molecules as antimicrobial peptides and enzymes in order to draw applications in fields ranging from pharmacology to cultural heritage. Particularly, in the control of the microbic growth and especially in the tuning of biocleaning protocols, bioactive molecules with proteasic and esterasic activity have been used. These novel enzymes are active at temperature lower than 30°C, they need a reduced time of application and are safety for both operators and environment. Thus they could provide an important contribution to the development of sustainable innovative protocols.

The evolution of multicellular organisms was marked by adaptation to protect against pathogens. The mechanisms for discriminating the ''self'' from ''non-self” have evolved into a long history of cellular and molecular strategies from damage repair to the co-evolution of host-pathogen interaction. The phylum of Cnidaria is one of the first branches in the tree of animal life to provide crucial insights on the evolution of immunity. Sea anemones (Anthozoa, Cnidaria) are benthic sessile species able to maintain the integrity of the tissues and allorecognition in colonial forms and to differentiate between symbionts and pathogenic intruders. We investigated the inflammatory response in sea anemone Anemonia sulcata following injection of various substances different in type and dimension, and observed clear, strong and specific reactions especially after injection of Escherichia coli and Vibrio alginolyticus. In particular we studied the effect of injectioninoculation of different sized suspensions (LPS, Phenyl Sepharose, cellulose, red blood cells, bacteria) into the pedal disk, of specimens in order to observe differential physical, biochemical and enzymatic reactions. We have shown for the first time in cnidarians a specific cellular and molecular response against pathogenic bacteria. The first phenomenon we observed was a body and foot swelling, followed by the formation of a yellowish rejection zone . A further study was also carried out by a histological analysis for the characterization of the area of rejection.This specific response suggested an extrusion of the material damaged by the animal, probably from the pores cinclides from which protrude the acontia in the pedal disk, a defense mechanism that has not yet been found in other cnidarians. Moreover, we analyzed enzymatic activity of protease, phosphatase and esterase, showing how the injection of different bacterial strains alters the expression of these enzymes, that catabolize prey tissues, suggesting a correlation between the appearance of the inflammatory reaction and the modification of enzymatic activities. Our study shows for the first time, a specific inflammatory-like response rejection and enzymatic responses following injection of bacteria in Cnidarian.

The discovery of rhamnose-binding lectins (RBLs) in teleost fish eggs led to the identification of a novel lectin family characterized by a unique sequence motif and a structural fold, and initially proposed to modulate fertilization. Further studies of the RBL tissue localization and gene organization were also suggestive of role(s) in innate immunity. Here we describe the purification, and biochemical and functional characterization of a novel RBL (DlRBL) from sea bass (Dicentrarchus labrax) serum. The purified DlRBL had electrophoretic mobilities corresponding to 24 kDa and 100 kDa under reducing and non-reducing conditions, respectively, suggesting that in plasma the DlRBL is present as a physiological homotetramer. DlRBL subunit transcripts revealed an open reading frame encoding 212 amino acid residues that included two tandemly-arrayed carbohydrate-recognition domains, and an 18-residue signal sequence at the N-terminus. The deduced size of 24.1 kDa for the mature protein was in good agreement with the subunit size of the isolated lectin. Binding activity of DlRBL for rabbit erythrocytes could be inhibited in the presence of rhamnose or galactose, did not require calcium, and was optimal at around 20 °C and within the pH 6.5–8.0 range. DlRBL agglutinated Gram positive and Gram negative bacteria, and exposure of formalin-killed Escherichia coli to DlRBL enhanced their phagocytosis by D. labrax peritoneal macrophages relative to the unexposed controls. Taken together, the results suggest that plasma DlRBL may play a role in immune recognition of microbial pathogens and facilitate their clearance by phagocytosis.

The F-lectin, a fucose-binding protein found from invertebrates to ectothermic vertebrates, is the last lectin family to be discovered. Here, we describe effects of two different types of stressors, bacterial infection and confinement stress, on the modulation of European sea bass Dicentrarchus labrax (L.) F-lectin (DlFBL), a well-characterized serum opsonin, using a specific antibody. The infection of the Vibrio alginolyticus bacterial strain increased the total haemagglutinating activity during the 16-day testing period. The DlFBL value showed an upward regulation on the first, second and last days and underwent a slight downward regulation 4 days post-challenge. In contrast, the effect of confinement and density stress showed a decrease in the plasma concentration of lectin, ranging from 50% to 60% compared with the control. The modulation of DlFBL is in line with the hypothesis that humoral lectins could be involved and recruited in the initial recognition step of the inflammation, which leads to agglutination, and the activation of mechanisms responsible for killing of the pathogens.

The purification, cloning, sequencing, molecular properties and expression of a fucose-binding lectin from the serum of Dicentrarchus labrax (DlFBL) have been previously reported. We now describe the distribution and expression of DlFBL during fish ontogeny. Immunohistochemistry and in situ hybridization assays were carried out at various developmental stages (from 10 days posthatching larvae to juveniles). Another fucose-binding lectin, similar to DlFBL in biochemical, immunochemical and agglutinating properties, was extracted and purified from eggs and appeared to be localized in the embryo yolk sack residual. DlFBL was found in columnar and goblet cells of the intestinal epithelium of larvae (from 20 days post-hatching) and juveniles and in parenchymal tissue of juveniles. DlFBL mRNA and protein were detected in the intestinal epithelium and in hepatocytes. An amplification product from degenerate primers indicates that lectin isotypes with DlFBL epitopes are expressed in eggs and embryos. Whether the lectin fraction isolated from eggs and embryos includes DlFBL of maternal origin remains unclear.

This study shows that high methylmercury concentrations are cytotoxic for Dicentrarchus labrax leucocytes, whereas subletal concentrations affect leucocyte phagocytosis and cells morphology in a dose dependent fashion. Although the serum hemoagglutinating activity was not inhibited by the metal, the activity of purified serum F-lectin fraction and mucus was significantly decreased by relevant methylmercury concentrations.

This study shows that high methylmercury concentrations are cytotoxic for Styela plicata hemocytes, whereas sublethal concentrations affect immunocyte responses. Moreover, hemocytes exposed to the xenobiotic present a significantly enhanced phenoloxidase activity as revealed in the hemocyte lysate supernatant compared with the control. Although the cytotoxic activity of S. plicata hemocytes toward rabbit erythrocytes is a PO-dependent cell-target reaction due to quinone products, it was significantly decreased by suitable methylmercury concentrations in the medium. The same xenobiotic concentrations decreased the hemocyte phagocytic activity toward yeast. In both the responses cell-target contacts could be affected by methylmercury, whereas the releasing capacity appeared to be unchanged, as indicated by hemocyte PO-release in the medium. Finally, changes in hemocyte shape and spreading capacity were shown. On the basis of the present results, Styela plicata hemocyte responses could be an additional immunotoxicology test using a microplate method that reveals cell morphological changes and spreading capacity. Copyright © 2007 John Wiley & Sons, Ltd.

The purification, cloning, sequencing, molecular properties and expression of a fucose-binding lectin from the serum of Dicentrarchus labrax (DlFBL) have been previously reported. We now describe the distribution and expression of DlFBL during fish ontogeny. Immunohistochemistry and in situ hybridization assays were carried out at various developmental stages (from 10 days posthatching larvae to juveniles). Another fucose-binding lectin, similar to DlFBL in biochemical, immunochemical and agglutinating properties, was extracted and purified from eggs and appeared to be localized in the embryo yolk sack residual. DlFBL was found in columnar and goblet cells of the intestinal epithelium of larvae (from 20 days post-hatching) and juveniles and in parenchymal tissue of juveniles. DlFBL mRNA and protein were detected in the intestinal epithelium and in hepatocytes. An amplification product from degenerate primers indicates that lectin isotypes with DlFBL epitopes are expressed in eggs and embryos. Whether the lectin fraction isolated from eggs and embryos includes DlFBL of maternal origin remains unclear.

A novel fucose-binding lectin, designated SauFBP32, was purified by affinity chromatography on fucose-agarose, from the serum of the gilt head bream Sparus aurata. Electrophoretic mobility of the subunit revealed apparent molecular weights of 35 and 30 kDa under reducing and non-reducing conditions, respectively. Size exclusion analysis suggests that the native lectin is a monomer under the selected experimental conditions. Agglutinating activity towards rabbit erythrocytes was not significantly modified by addition of calcium or EDTA; activity was optimal at 37 degrees C, retained partial activity by treatment at 70 degrees C, and was fully inactivated at 90 degrees C. On western blot analysis, SauFBP showed intense cross-reactivity with antibodies specific for a sea bass (Dicentrarchus labrax) fucose-binding lectin. In addition, the similarity of the N-terminal sequence and a partial coding domain to teleost F-type lectins suggests that SauFBP32 is a member of this emerging family of lectins.