Characterization of glycans in the developmental stages of Myxobolus cerebralis (Myxozoa), the causative agent of whirling disease

Evaluating glycocalyx morphology and composition in frozen and formalin-fixed liver tumor sections

BACKGROUND

The glycocalyx (GCX) is a glycan structure on the vascular endothelium and cancer cells. It is crucial for blood flow regulation, tumor invasion, and cancer drug resistance. Understanding the role of GCX in human tumors could help develop new cancer biomarkers and therapies.

AIM

This study aimed to demonstrate microstructural changes in human primary and metastatic liver tumors (henceforth termed liver tumors) by visualizing GCX using surgical specimens and comparing formalin-fixed paraffin-embedded sections (FFPEs) with frozen sections. The results of lectin staining were also compared between frozen and FFPE specimens to determine which was more useful for accurately assessing GCX structure and composition.

METHODS

Liver tumors and normal tissue samples from three patients were collected and processed into FFPEs and frozen sections, respectively. Lanthanum nitrate staining and scanning electron microscopy (SEM) were used to assess the GCX structures. Twenty lectins were analyzed for their glycan components in the samples.

RESULTS

SEM revealed significant differences in GCX morphology among the cancer specimens. Frozen sections provided a more accurate GCX evaluation than FFPEs, showing distinct glycan compositions in hepatocellular carcinoma, colorectal carcinoma liver metastases, and melanoma liver metastases. Hepatocellular carcinoma samples exhibited a loss of N-acetylgalactosamine-related lectins.

CONCLUSION

The results revealed that liver tumors have distinct and bulky GCX compared to normal liver tissue, while frozen sections are more reliable for GCX evaluation. These findings highlight glycan alterations in liver tumors and contribute to the development of new cancer therapies targeting GCX on tumor cell surfaces.

Glycocalyx analysis of bladder cancer: three-dimensional images in electron microscopy and vicia villosa lectin as a marker for invasiveness in frozen sections

Introduction: The abnormal glycocalyx (GCX) on the surface of cancer cells has been reported to be tall and aberrantly glycosylated and has been linked to the progression and spread of cancer-a finding also observed in bladder cancer. However, the characteristics of GCX in various types of human bladder cancer remain unknown, and herein, we aimed to provide information on the diversity of glycan components in the GCX of bladder cancers and to shed light on their characteristics. Methods: We used scanning electron microscopy and lanthanum staining to examine the surface GCX of human bladder carcinomas in three-dimensional images, showing the bulky GCX in some carcinomas. We also examined glycan alterations in early to progressive stages of bladder cancers using 20 distinct lectin stains on frozen sections from transurethral resection of bladder tumors. Results and discussion: Distinctive Vicia villosa lectin (VVL) staining was observed in invasive urothelial carcinomas, including those with muscle invasion and variant components. In the clinical setting, cancers with atypia of grades 2-3 had a significantly higher VVL scoring intensity than those with grade 1 atypia (p < 0.005). This study identified that a specific lectin, VVL, was more specific to invasive urothelial carcinomas. This lectin, which selectively binds to sites of cancer progression, is a promising target for drug delivery in future clinical investigations.

To React or Not to React: The Dilemma of Fish Immune Systems Facing Myxozoan Infections

Myxozoans are microscopic, metazoan, obligate parasites, belonging to the phylum Cnidaria. In contrast to the free-living lifestyle of most members of this taxon, myxozoans have complex life cycles alternating between vertebrate and invertebrate hosts. Vertebrate hosts are primarily fish, although they are also reported from amphibians, reptiles, trematodes, mollusks, birds and mammals. Invertebrate hosts include annelids and bryozoans. Most myxozoans are not overtly pathogenic to fish hosts, but some are responsible for severe economic losses in fisheries and aquaculture. In both scenarios, the interaction between the parasite and the host immune system is key to explain such different outcomes of this relationship. Innate immune responses contribute to the resistance of certain fish strains and species, and the absence or low levels of some innate and regulatory factors explain the high pathogenicity of some infections. In many cases, immune evasion explains the absence of a host response and allows the parasite to proliferate covertly during the first stages of the infection. In some infections, the lack of an appropriate regulatory response results in an excessive inflammatory response, causing immunopathological consequences that are worse than inflicted by the parasite itself. This review will update the available information about the immune responses against Myxozoa, with special focus on T and B lymphocyte and immunoglobulin responses, how these immune effectors are modulated by different biotic and abiotic factors, and on the mechanisms of immune evasion targeting specific immune effectors. The current and future design of control strategies for myxozoan diseases is based on understanding this myxozoan-fish interaction, and immune-based strategies such as improvement of innate and specific factors through diets and additives, host genetic selection, passive immunization and vaccination, are starting to be considered.

Glycan changes in the olfactory mucosa of rats with experimental autoimmune encephalomyelitis

Glycans are components of glycoconjugates and function in odorant recognition and cell signaling in the olfactory mucosa. However, little is known about glycan expression in the olfactory mucosa in the presence of neuroinflammatory disorders, which can influence olfaction. We evaluated the changes in glycan in the olfactory mucosa of rats with experimental autoimmune encephalomyelitis (EAE) by histochemical analyses of 21 lectins. In the olfactory mucosa of normal control rats, 16 lectins bound to olfactory sensory neurons, supporting cells, basal cells, nerve and Bowman's glands, and their expression did not significantly change during the course of EAE. In rats with paralytic-stage EAE, five lectins showed different reactivities with the olfactory mucosa compared to those of normal control rats. Of them, Bandeiraea simplicifolia lectin (BSL)-II and BSL-I showed transiently downregulated binding to olfactory sensory neurons and supporting cells in rats with EAE. The reactivities of Lens culinaris agglutinin for the basement membrane, Vicia villosa agglutinin for Bowman's glands and Dolichos biflorus agglutinin for all nuclei were upregulated in the olfactory mucosa of EAE rats. These results suggest that BSL-II-binding N-acetyl-glucosamine and BSL-I-binding N-acetyl-galactose are involved in transient olfactory dysfunction in EAE, which may hamper odor perception and/or signal processing in olfactory sensory neurons.

Malacosporean myxozoans exploit a diversity of fish hosts

Myxozoans are widespread and common endoparasites of fish with complex life cycles, infecting vertebrate and invertebrate hosts. There are two classes: Myxosporea and Malacosporea. To date about 2500 myxosporean species have been described. By comparison, there are only five described malacosporean species. Malacosporean development in the invertebrate hosts (freshwater bryozoans) has been relatively well studied but is poorly known in fish hosts. Our aim was to investigate the presence and development of malacosporeans infecting a diversity of fish from Brazil, Europe and the USA. We examined kidney from 256 fish belonging variously to the Salmonidae, Cyprinidae, Nemacheilidae, Esocidae, Percidae, Polyodontidae, Serrasalmidae, Cichlidae and Pimelodidae. Malacosporean infections were detected and identified by polymerase chain reaction and small subunit ribosomal DNA sequencing, and the presence of sporogonic stages was evaluated by ultrastructural examination. We found five malacosporean infections in populations of seven European fish species (brown trout, rainbow trout, white fish, dace, roach, gudgeon and stone loach). Ultrastructural analyses revealed sporogonic stages in kidney tubules of three fish species (brown trout, roach and stone loach), providing evidence that fish belonging to at least three families are true hosts. These results expand the range of fish hosts exploited by malacosporeans to complete their life cycle.

Glycan diversity in the vomeronasal organ of the Korean roe deer, Capreolus pygargus: A lectin histochemical study

Glycans in the epithelium play an important role in cell-to-cell communication and adhesion. No detailed evaluation of glycoconjugates in the vomeronasal organs (VNO) of the roe deer has been published previously. The aim of this study was to characterize glycan epitopes in the vomeronasal sensory epithelium (VSE) and non-sensory epithelium (VNSE) using lectin histochemistry. Glycan epitopes identified by lectin histochemistry were grouped as follows: N-acetylglucosamine (s-WGA, WGA, BSL-II, DSL, LEL, STL), mannose (Con A, LCA, PSA), galactose (RCA₁₂₀, BSL-I, Jacalin, PNA, ECL), N-acetylgalactosamine (VVA, DBA, SBA, and SJA), fucose (UEA-I) and complex type N-glycan (PHA-E and PHA-L) groups. The free border of the VSE was positive for all 21 lectins, and 18 of the lectins (excluding DBA, SJA, and PHA-L) showed weak and/or moderate staining in the receptor cells. The supporting cells were weakly positive for 19 lectins (excluding PNA and SJA). Moreover, 17 lectins (excluding BSL-II, Jacalin, PNA, and SJA) were expressed in the basal cells. In the VNSE of roe deer, the free border showed staining for all 21 lectins examined. The ciliated cells were positive for 16 lectins (excluding BSL-II, DSL, PNA, VVA, and SJA). Furthermore, 15 lectins (excluding DSL, LEL, ECL, UEA-I, PHA-E, and PHA-L) were expressed in goblet cells. Twenty lectins (excluding SJA) were expressed in the acini of the vomeronasal glands. Collectively, both VSE and VNSE were rich in N-acetylglucosamine, mannose, galactose, N-acetylgalactosamine, fucose, and complex-type N-glycans, although the different cell types of the VSE and VNSE expressed different glycoconjugates of varying intensities, suggesting that these carbohydrate residues may be involved in odor perception as well as cell-to-cell communication in the VNO.

Immunity to gastrointestinal microparasites of fish

Fish intestinal parasites cause direct mortalities and also morbidity, poor growth, higher susceptibility to opportunistic pathogens and lower resistance to stress. This review is focused on microscopic parasites (Protozoa and Metazoa) that invade the gastrointestinal tract of fish. Intracellular parasites (mainly Microsporidia and Apicomplexa) evoke almost no host immune reaction while they are concealed in the cytoplasmic and nuclear compartments, and can even use fish cells (macrophages) as Trojan horses to spread in the host. Inflammatory reaction only appears when the parasite bursts infected cells. Immunity against extracellular parasites is depicted for the myxozoans Ceratonova shasta and Enteromyxum spp. The cellular and humoral innate responses and the production of antibodies are crucial for resolving some of these myxozoonoses, but an excessive inflammatory reaction (concerted by cytokines) can become a fatal pathophysiological consequence. The local immune response plays a key role, with numerous genes more strongly regulated in the intestine than at lymphohaematopoietic organs.

Histological and lectin histochemical studies of the vomeronasal organ of horses

The morphological characteristics and glycoconjugate composition of the vomeronasal organ (VNO) of the horse was investigated using histological, immunohistochemical, and lectin histochemical methods. The VNO is bilaterally located at the base of the nasal septum, has a tubular structure surrounded by cartilage, and consists of sensory and non-sensory epithelia. Immunohistochemical examination showed that the vomeronasal sensory epithelium (VSE) consisted of receptor cells positive for both olfactory marker protein (OMP) and protein gene product 9.5 (PGP 9.5), supporting cells, and basal cells. VNO receptor cells were positive for G protein Gαi2 (vomeronasal receptor type 1 marker), but not Gαo (vomeronasal receptor type 2 marker). Lectin histochemical studies using 21 biotinylated lectins showed that the free border of the VSE was positive for 20 lectins. The receptor and supporting cells reacted with 16 lectins while the basal cells reacted with 15 lectins, with varying intensities. In the vomeronasal non-sensory epithelium, the free border was positive for 19 lectins. The cilated cells were positive for 17 lectins and the basal cells were positive for 15 lectins. The vomeronasal glands, positioned in the lamina propria, were stained with both periodic acid Schiff (PAS) and alcian blue (pH 2.5). Eighteen lectins stained the acinar cells of the vomeronasal glands with various binding patterns. These findings suggest that horse VNO receptor cells express vomeronasal receptor type 1, and the VNO glands have mucous to seromucous characteristics. Moreover, each lectin differentially binds each cell type in both the VNO sensory and non-sensory epithelia.

Lectin histochemistry of Kudoa septempunctata genotype ST3-infected muscle of olive flounder (Paralichthys olivaceus)

The localization of carbohydrate terminals in Kudoa septempunctata ST3-infected muscle of olive flounder (Paralichthys olivaceus) was investigated using lectin histochemistry to determine the types of carbohydrate sugar residues expressed in Kudoa spores. Twenty-one lectins were examined, i.e., N-acetylglucosamine (s-WGA, WGA, DSL-II, DSL, LEL, STL), mannose (Con A, LCA, PSA), galactose/N-acetylgalactosamine (RCA12, BSL-I, VVA, DBA, SBA, SJA, Jacalin, PNA, ECL), complex type N-glycans (PHA-E and PHA-L), and fucose (UEA-I). Spores encased by a plasmodial membrane were labeled for the majority of these lectins, with the exception of LCA, PSA, PNA, and PHA-L. Four lectins (RCA 120, BSL-I, DBA, and SJA) belonging to the galactose/N-acetylgalactosamine group, only labeled spores, but not the plasmodial membrane. This is the first confirmation that various sugar residues are present in spores and plasmodial membranes of K. septempunctata ST3.

Histochemical study of the olfactory mucosae of the horse

The olfactory mucosae of the horse were examined by using histology and lectin histochemistry to characterize the carbohydrate sugar residues therein. Histological findings revealed that olfactory epithelium (OE) consisted of both olfactory marker protein (OMP)- and protein gene product (PGP) 9.5-positive receptor cells, supporting cells and basal cells with intervening secretory ducts from Bowman's glands. Mucus histochemistry showed that Bowman's gland acini contain periodic acid-Schiff (PAS) reagent-positive neutral mucins and alcian blue pH 2.5-positive mucosubstances. Lectin histochemistry revealed that a variety of carbohydrate sugar residues, including N-acetylglucosamine, mannose, galactose, N-acetylgalactosamine, fucose and complex type N-glycan groups, are present in the various cell types in the olfactory mucosa at varying levels. Collectively, this is the first descriptive study of horse olfactory mucosa to characterize carbohydrate sugar residues in the OE and Bowman's glands.

Biology and mucosal immunity to myxozoans

Myxozoans are among the most abundant parasites in nature. Their life cycles involve two hosts: an invertebrate, usually an annelid, and a vertebrate, usually a fish. They affect fish species in their natural habitats but also constitute a menace for fish aquaculture. Using different strategies they are able to parasitize and cause damage in multiple organs, including mucosal tissues, which they use also as portals of entry. In fish, the main mucosal sites include the intestine, skin and gills. Recently the finding of a specific mucosal immunoglobulin in teleost (IgT), analogous to mammalian IgA, and the capacity of fish to develop a specific mucosal immune response against different pathogens, has highlighted the importance of studying immune responses at mucosal sites. In this review, we describe the major biological characteristics of myxozoan parasites and present the data available regarding immune responses for species that infect mucosal sites. As models for mucosal immunity we review the responses to Enteromyxum spp. and Ceratomyxa shasta, both of which parasitize the intestine. The immune response at the skin and gills is also described, as these mucosal tissues are used by myxozoans as attaching surfaces and portal of entry, and some species also parasitize these sites. Finally, the development of immunoprophylactic strategies is discussed.

Antigenic characterization of Enteromyxum leei (Myxozoa: Myxosporea)

Enteromyxum leei, an intestinal myxozoan parasite affecting a wide range of fish, was partially purified, and the immunogenic composition of its glycoproteins as well as the proteolytic activity were studied. Parasite extracts, mainly containing spores, were separated by SDS-PAGE, and thereafter, immunoblots were carried out with a polyclonal antiserum (Pab) raised against E. leei. Periodic acid/Schiff staining of gels, periodate- and Proteinase K-treated Western blots and Lectin blots were performed to analyse the terminal carbohydrate composition of the parasite's antigens. Additionally, the cross-reaction of the parasite extracts with a Pab raised against the polar filament of the myxozoan Myxobolus pendula was studied. Both Pabs detected proteic epitopes on antigenic proteins and glycoproteins of E. leei, ranging between 15 and 280 kDa. In particular, 2 glycoproteic bands (15 and 165 kDa), immunoreactive to both Pabs and with glucose and mannose moieties, could correspond to common antigens shared among myxozoans. The 165 kDa band also presented galactose, N-acetyl-galactosamine and N-acetyl-glucosamine, pointing to its possible origin on chitin-built spore valves and to its possible involvement in host-parasite interactions. The molecular weight of the 15 kDa glycoproteic antigen matches that of minicollagen, a cnidarian-specific protein of nematocysts with a myxozoan homologue. Several proteases with apparent molecular weights ranging between 43 and 245 kDa were found in zymographies of E. leei extracts, and these may have a potential role in the parasite's pathogenesis. This is a useful approach for further studies to detect targets for antiparasitic therapy.

A Chitinase from Aeromonas veronii CD3 with the potential to control myxozoan disease

Background

The class Myxosporea encompasses about 2,400 species, most of which are parasites of fish and cause serious damage in aquaculture. Due to the concerns about food safety issues and limited knowledge of Myxozoa life cycle and fish immune system, no chemicals, antibiotics or immune modulators are available to control myxozoa infection. Therefore, little can be done once Myxozoa establishment has occurred.

Methodology/Principal Findings

In this paper we isolated Aeromonas veronii CD3 with significant myxospore shell valve-degrading ability from pond sediment. A 3,057-bp full-length chitinase gene was consequently cloned, and the corresponding mature, recombinant chitinase (ChiCD3) produced by Escherichia coli had substantial chitinase activity. The deduced sequence of ChiCD3 contained one catalytic domain, two chitin-binding domains, and one putative signal peptide. ChiCD3 had an optimal activity at 50°C and pH 6.0, and retained more than 50% of its optimal activity under warm water aquaculture conditions (∼30°C and pH ∼7.0). After incubation with ChiCD3, 38.0±4.8% of the myxospores had damaged shell valves, whereas myxospores incubated with commercially available chitinases remained intact.

Conclusion/Significance

This study reveals a new strategy to control myxozoan disease. ChiCD3 that has capacity to damage the shell valve of myxospores can be supplemented into fish feed and used to control Myxozoa-induced diseases specifically.