Pathogenic bacteria prime the induction of Toll-like receptor signalling in human colonic cells by the Gal/GalNAc lectin Carbohydrate Recognition Domain of Entamoeba histolytica

When glycobiology meets inflammasome activation: Insights and implications

BACKGROUND

Glycobiology focuses mainly on the study of glycan structures and their biological functions. Glycans not only provide a basic energy supply through the tricarboxylic acid cycle and glycolysis but also serve as important immune regulators during pathogen invasion and homeostasis maintenance. Inflammasomes are critical multiprotein complexes of the immune system that detect both exogenous pathogenic threats and endogenous danger signals to mediate inflammatory responses. Glycobiology has revealed significant insights into the mechanisms of immune responses, particularly in the context of inflammasome activation.

AIM OF REVIEW

This review summarizes the multifaceted relationships between glycobiology and inflammasome activation, highlighting how glycan structures, glycosylation patterns, and glycan-binding proteins influence inflammasome pathways. This review sheds light on novel targets for drug development aimed at modulating inflammatory pathways through the targeting of specific glycan structures.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Glycans directly or indirectly provide prime and activation signals for inflammasomes, glycosylation of inflammasome-related proteins by glycan structures modulates inflammasome activation and downstream inflammation, and the interaction between glycans and lectins also provides regulatory signals for inflammasome activation. This intersection of glycobiology and inflammasome activation presents a unique opportunity to elucidate the molecular mechanisms underlying inflammatory responses and their potential therapeutic implications.

Swine Gut Lactic Acid Bacteria and Their Exopolysaccharides Differentially Modulate Toll-like Receptor Signaling Depending on the Agave Fructans Used as a Carbon Source

Exopolysaccharides (EPSs) produced by probiotic bacteria have garnered attention due to their effects on the gut health of humans and animals. The nutrients that probiotics access during their growth are essential for producing beneficial effects on host health. Direct immunomodulatory effects of graminan-type fructans (GTFs) from Agave tequilana through toll-like receptors (TLRs) have been demonstrated. However, the immunomodulatory effects of these fructans, mediated through the EPSs produced by the probiotics cultivated with them, remain unexplored. We explored the immunomodulatory effects of lactic acid bacteria (LAB) strains isolated from swine and their EPSs, based on the GTFs used as carbon sources during their growth. While the LAB strains activated the NF-κB pathway independently of the GTF source, their EPSs activated it in a GTF source-dependent manner. LAB activation through TLR2 showed a GTF source dependency, whereas their EPSs activated TLR2 independently of the GTF source. The LAB and their EPSs activated TLR4 in a GTF source-dependent manner. Both the LAB and their EPSs inhibited the activation of TLR2 and TLR4 agonists, which exhibited a strong dependence on the GTF source. The strength of GTF C's immunomodulatory effects on LAB illustrates its specificity, its impact on the EPS structure, and its biological effects. Our results support the promising health benefits of this synbiotic model for swine health and lowering inflammation.

Exopolysaccharides from Bifidobacterium longum subsp. infantis and Bifidobacterium adolescentis modulate Toll-like receptor signaling

BACKGROUND

Exopolysaccharides (EPS) from probiotic bacteria like bifidobacteria, have gained considerable attention for the beneficial effects they exert in the gastrointestinal environment. Here, we investigated whether EPS isolated from Bifidobacterium longum subsp. infantis and Bifidobacterium adolescentis can interact with Toll-like receptors (TLRs) in a structure-dependent way and subsequently we investigated whether they influence cytokine-production in dendritic cells (DCs).

RESULTS

EPS from both B. infantis and B. adolescentis were found to be structurally different and were able to inhibit signaling of TLR2 and TLR4 in an EPS-type dependent fashion. EPS from B. infantis was shown to have stronger inhibitory effects on TLR2/1, whereas EPS from B. adolescentis showed stronger effects for TLR2/6 and TLR4. Incubation of DCs with EPS alone had no effect, however stimulation of DCs with spend-medium of epithelial cells incubated with EPS reduced production of the cytokines MCP-1/CCL2 and TNFα.

CONCLUSION

Here we show that EPS from B. infantis and B. adolescentis have structure-dependent immunomodulatory effects, indicating that EPS might be important effector molecules responsible for the health benefits of bifidobacteria.

An insight into the concept of neuroinflammation and neurodegeneration in Alzheimer's disease: targeting molecular approach Nrf2, NF-κB, and CREB

Alzheimer's disease (AD) is a most prevalent neurologic disorder characterized by cognitive dysfunction, amyloid-β (Aβ) protein accumulation, and excessive neuroinflammation. It affects various life tasks and reduces thinking, memory, capability, reasoning and orientation ability, decision, and language. The major parts responsible for these abnormalities are the cerebral cortex, amygdala, and hippocampus. Excessive inflammatory markers release, and microglial activation affect post-synaptic neurotransmission. Various mechanisms of AD pathogenesis have been explored, but still, there is a need to debate the role of NF-κB, Nrf2, inflammatory markers, CREB signaling, etc. In this review, we have briefly discussed the signaling mechanisms and function of the NF-ĸB signaling pathway, inflammatory mediators, microglia activation, and alteration of autophagy. NF-κB inhibition is a current strategy to counter neuroinflammation and neurodegeneration in the brain of individuals with AD. In clinical trials, numbers of NF-κB modulators are being examined. Recent reports revealed that molecular and cellular pathways initiate complex pathological competencies that cause AD. Moreover, this review will provide extensive knowledge of the cAMP response element binding protein (CREB) and how these nuclear proteins affect neuronal plasticity.

Molecular regulation of NLRP3 inflammasome activation during parasitic infection

Parasitic diseases are a serious global health concern, causing many common and severe infections, including Chagas disease, leishmaniasis, and schistosomiasis. The NLRP3 inflammasome belongs to the NLR (nucleotide-binding domain leucine-rich-repeat-containing proteins) family, which are cytosolic proteins playing key roles in the detection of pathogens. NLRP3 inflammasomes are activated in immune responses to Plasmodium, Leishmania, Toxoplasma gondii, Entamoeba histolytica, Trypanosoma cruzi, and other parasites. The role of NLRP3 is not fully understood, but it is a crucial component of the innate immune response to parasitic infections and its functions as a sensor triggering the inflammatory response to the invasive parasites. However, while this response can limit the parasites' growth, it can also result in potentially catastrophic host pathology. This makes it essential to understand how NLRP3 interacts with parasites to initiate the inflammatory response. Plasmodium hemozoin, Leishmania glycoconjugate lipophosphoglycan (LPG) and E. histolytica Gal/GalNAc lectin can stimulate NLRP3 activation, while the dense granule protein 9 (GRA9) of T. gondii has been shown to suppress it. Several other parasitic products also have diverse effects on NLRP3 activation. Understanding the mechanism of NLRP3 interaction with these products will help to develop advanced therapeutic approaches to treat parasitic diseases. This review summarizes current knowledge of the NLRP3 inflammasome's action on the immune response to parasitic infections and aims to determine the mechanisms through which parasitic molecules either activate or inhibit its action.

Galactomannan inhibits Trichinella spiralis invasion of intestinal epithelium cells and enhances antibody-dependent cellular cytotoxicity related killing of larvae by driving macrophage polarization

Previous studies have shown that recombinant Trichinella spiralis galectin (rTsgal) is characterized by a carbohydrate recognition domain sequence motif binding to beta-galactoside, and that rTsgal promotes larval invasion of intestinal epithelial cells. Galactomannan is an immunostimulatory polysaccharide composed of a mannan backbone with galactose residues. The aim of this study was to investigate whether galactomannan inhibits larval intrusion of intestinal epithelial cells and enhances antibody-dependent cellular cytotoxicity (ADCC), killing newborn larvae by polarizing macrophages to the M1 phenotype. The results showed that galactomannan specially binds to rTsgal, and abrogated rTsgal facilitation of larval invasion of intestinal epithelial cells. The results of qPCR, Western blotting, and flow cytometry showed that galactomannan and rTsgal activated macrophage M1 polarization, as demonstrated by high expression of iNOS (M1 marker) and M1 related genes (IL-1β, IL-6, and TNF-α), and increased CD86+ macrophages. Galactomannan and rTsgal also increased NO production. The killing ability of macrophage-mediated ADCC on larvae was also significantly enhanced in galactomannan- and rTsgal-treated macrophages. The results demonstrated that Tsgal may be considered a potential vaccine target molecule against T. spiralis invasion, and galactomannan may be a novel adjuvant therapeutic agent and potential vaccine adjuvant against T. spiralis infection.

The protective immunity induced by Trichinella spiralis galectin against larval challenge and the potential of galactomannan as a novel adjuvant

Previous studies showed that recombinant Trichinella spiralis galectin (rTsgal) promoted larval invasion of gut epithelial cells, while anti-rTsgal antibodies inhibited the invasion. Galactomannan (GM) is a polysaccharide capable of regulating immune response. The aim of this study was to evaluate protective immunity induced by rTsgal immunization and the potential of GM as a novel adjuvant. The results showed that vaccination of mice with rTsgal+ISA201 and rTsgal+GM elicited a Th1/Th2 immune response. Mice immunized with rTsgal+ISA201 and rTsgal+GM exhibited significantly higher levels of serum anti-rTsgal antibodies, mucosal sIgA and cellular immune responses, but level of specific antibodies and cytokines of rTsgal+GM group was lower than the rTsgal+ISA201 group. Immunization of mice with rTsgal+ISA201 and rTsgal+GM showed a 50.5 and 40.16% reduction of intestinal adults, and 52.04 and 37.53% reduction of muscle larvae after challenge. Moreover, the numbers of goblet cells and expression level of mucin 2, Muc5ac and pro-inflammatory cytokines (TNF-α and IL-1β) in gut tissues of vaccinated mice were obviously decreased, while Th2 inducing cytokine (IL-4) expression was evidently increased. Galactomannan enhanced protective immunity, alleviated intestinal and muscle inflammation of infected mice. The results indicated that rTsgal+ISA201 vaccination induced a more prominent gut local as well as systemic immune response and protection compared to rTsgal+GM vaccination. The results suggested that Tsgal could be considered as a candidate vaccine target against Trichinella infection and galactomannan might be a potential novel candidate adjuvant of anti-Trichinella vaccines.

Trichinella spiralis galectin binding to toll-like receptor 4 induces intestinal inflammation and mediates larval invasion of gut mucosa

Previous studies showed that Trichinella spiralis galectin (Tsgal) facilitates larval invasion of intestinal epithelium cells (IECs). However, IEC proteins binding with Tsgal were not identified, and the mechanism by which Tsgal promotes larval invasion is not clear. Toll-like receptors (TLRs) are protein receptors responsible for recognition of pathogens. The aim of this study was to investigate whether recombinant Tsgal (rTsgal) binds to TLR-4, activates inflammatory pathway in gut epithelium and mediates T. spiralis invasion. Indirect immunofluorescence (IIF), GST pull-down and co-immunoprecipitation (Co-IP) assays confirmed specific binding between rTsgal and TLR-4 in Caco-2 cells. qPCR and Western blotting showed that binding of rTsgal with TLR-4 up-regulated the TLR-4 transcription and expression in Caco-2 cells, and activated p-NF-κB p65 and p-ERK1/2. Activation of inflammatory pathway TLR-4/MAPK-NF-κB by rTsgal up-regulated pro-inflammatory cytokines (IL-1β and IL-6) and down-regulated anti-inflammatory cytokine TGF-β in Caco-2 cells, and induced intestinal inflammation. TAK-242 (TLR-4 inhibitor) and PDTC (NF-κB inhibitor) significantly inhibited the activation of TLR-4 and MAPK-NF-κB pathway. Moreover, the two inhibitors also inhibited IL-1β and IL-6 expression, and increased TGF-β expression in Caco-2 cells. In T. spiralis infected mice, the two inhibitors also inhibited the activation of TLR-4/MAPK-NF-κB pathway, ameliorated intestinal inflammation, impeded larval invasion of gut mucosa and reduced intestinal adult burdens. The results showed that rTsgal binding to TLR-4 in gut epithelium activated MAPK-NF-κB signaling pathway, induced the expression of TLR-4 and pro-inflammatory cytokines, and mediated larval invasion. Tsgal might be regarded as a candidate molecular target of vaccine against T. spiralis enteral invasive stage.

Immunomodulatory effect of extracellular vesicles from Entamoeba histolytica trophozoites: Regulation of NETs and respiratory burst during confrontation with human neutrophils

Parasites release extracellular vesicles (EVs) which, in some cases, modulate the host's immune response contributing to the establishment of the infection. In this work we have isolated and characterized the EVs released by trophozoites of the human protozoan parasite Entamoeba histolytica, the causal agent of amoebiasis, when alone or in coculture with human neutrophils, and determined their effect on neutrophil NETs and ROS production. Nanoparticle tracking analysis showed that amoebic EVs are variable in size, ranging from less than 50 nm to nearly 600 nm in diameter (average of 167 nm), whereas neutrophil EVs are more uniform in size, with an average of 136 nm. In cocultures amoeba:neutrophil (1:100) most EVs are 98 nm in size, which is the typical size of exosomes. EVs from amoebae and neutrophils showed almost equal levels of ROS, which were considerably increased in EVs from cocultures. Uptake of amoebic EVs by neutrophils was demonstrated by fluorescence and resulted in a significant reduction in the oxidative burst and NET release triggered by PMA, ionophore A23187, or the amoebae itself used as stimuli. Interestingly, uptake of EVs from cocultures did not affect ROS production, but instead caused a greater delay in the onset of NETs release and in their quantity. A comparative proteomic analysis between the EVs of amoebae and neutrophils separately vs the cocultures showed a similar distribution of protein categories in the GO analysis, but differences in the expression and abundance of proteins such as the N-acetyl-D-galactosamine (GalNAc) inhibitable surface lectin and calreticulin in amoeba EVs, and various antimicrobial molecules in neutrophil EVs, such as lactoferrin and myeloperoxidase. These results highlight the importance of EVs in the immunomodulatory effects exerted by amoeba on human neutrophils.

A novel C-type lectin from Trichinella spiralis mediates larval invasion of host intestinal epithelial cells

The aim of this study was to investigate the characteristics of a novel type C lectin from Trichinella spiralis (TsCTL) and its role in larval invasion of intestinal epithelial cells (IECs). TsCTL has a carbohydrate recognition domain (CRD) of C-type lectin. The full-length TsCTL cDNA sequence was cloned and expressed in Escherichia coli BL21. The results of qPCR, Western blotting and immunofluorescence assays (IFAs) showed that TsCTL was a surface and secretory protein that was highly expressed at the T. spiralis intestinal infective larva (IIL) stages and primarily located at the cuticle, stichosome and embryos of the parasite. rTsCTL could specifically bind with IECs, and the binding site was localized in the IEC nucleus and cytoplasm. The IFA results showed that natural TsCTL was secreted and bound to the enteral epithelium at the intestinal stage of T. spiralis infection. The rTsCTL had a haemagglutinating effect on murine erythrocytes, while mannose was able to inhibit the rTsCTL agglutinating effect for mouse erythrocytes. rTsCTL accelerated larval intrusion into the IECs, whereas anti-rTsCTL antibodies and mannose significantly impeded larval intrusion in a dose-dependent manner. The results indicated that TsCTL specifically binds to IECs and promotes larval invasion of intestinal epithelium, and it might be a potential target of vaccines against T. spiralis enteral stages.

Host-parasite interactions in infections due to Entamoeba histolytica: A tale of known and unknown

Entamoeba histolytica (E. histolytica) is an enteric microaerophilic protozoan parasite responsible for millions of cases worldwide. Majority of the infections due to E. histolytica remain asymptomatic; however, it can cause an array of symptoms ranging from devastating dysentery, colitis, and abscesses in different vital organs. The interactions between the E. histolytica and its host are a multifaceted chain of events rather than merely destruction and invasion. There are manifold decisive steps for the establishment of infections by E. histolytica which includes degradation of mucosal layer, adherence to the host epithelium, invasion into the host tissues, and dissemination to vital organs. It is widely hypothesized that, for establishment of infections, the interactions at the intestinal mucosa decides the fate of the disease. The delicate communications between the parasite, the host factors, and the associated bacterial microflora play a significant role in the pathogenesis of E. histolytica. In this review, we summarize the interactions between the E. histolytica and it's host at the genetic and immunological interphases emphasizing the crucial role of microbiota in these interactions.

Entamoeba histolytica Trophozoites Interact with the c-Met Receptor at the Surface of Liver Origin Cells through the Gal/GalNAc Amoebic Lectin

Amoebiasis in humans is caused by the protozoan parasite Entamoeba histolytica, which cytotoxic activity has been demonstrated on a wide variety of target cells. The process involves the adherence of the parasite to the cell, and such adherence is mediated by an amoebic surface lectin, known as Gal/GalNAc lectin. It is composed of heavy, intermediate, and light subunits. The carbohydrate recognition domain (CRD) has been identified within a cysteine-rich region in the lectin heavy subunit and has an amino acid sequence identity to the receptor-binding domain of hepatocyte growth factor (HGF). Recombinant CRD has been previously shown to compete with HGF for binding to the c-Met receptor IgG fusion protein. In the present study, we searched for evidence of interaction between the Gal/GalNAc lectin at the surface of trophozoites with the c-Met receptor expressed at the surface of HepG2 in coculture assays. Immunoprecipitation of the coculture lysate indicated interaction of the c-Met with a 60 kDa peptide recognized by antiamoebic lectin antibody. Colocalization of both molecules was detected by fluorescence confocal microscopy. Incubation of HepG2 cells with HGF before coculture with trophozoites prevents the cytotoxic effect caused by the parasites but not their adherence to the cells. Our results point to Gal/GalNAc lectin as a ligand of the c-Met receptor at the surface of HepG2 cells.

Fatal attraction: intestinal amebiasis and COVID-19 as risk factors for colonic perforation

The parasite Entamoeba histolytica, the causal agent of amebiasis, is considered a worldwide emergent disease and still represents an important cause of death in Mexico. Here, we describe a clinical case, involving an inflammatory response to both Coronavirus Infectious Disease 2019 (COVID-19) and intestinal amebiasis 54-year-old, COVID-positive Mexican gentleman was admitted to surgery following 6 days of hematochezia. An exploratory laparotomy and colonoscopy revealed multiple fibrous and amebic ulcerations (5–10 cm in diameter), with necrotic tissue predominantly localized in the sigmoid, descending and ascending colon. We discuss the pathophysiological interplay of both COVID-19 and intestinal amebiasis with the aim of highlighting a potentially novel aggravating mechanism in surgical patients suffering from colonic perforation in the setting of abdominal sepsis.

Immune Response to the Enteric Parasite Entamoeba histolytica

Entamoeba histolytica is a protozoan parasite responsible for amoebiasis, a disease with a high prevalence in developing countries. Establishing an amoebic infection involves interplay between pathogenic factors for invasion and tissue damage, and immune responses for protecting the host. Here, we review the pathogenicity of E. histolytica and summarize the latest knowledge on immune response and immune evasion mechanisms during amoebiasis.

Neutrophils vs. amoebas: Immunity against the protozoan parasite Entamoeba histolytica

Entamoeba histolytica is a protozoan parasite with high prevalence in developing countries, and causes amoebiasis. This disease affects the intestine and the liver, and is the third leading cause of human deaths among parasite infections. E. histolytica infection of the intestine or liver is associated with a strong inflammation characterized by a large number of infiltrating neutrophils. Consequently, several reports suggest that neutrophils play a protective role in amoebiasis. However, other reports indicate that amoebas making direct contact with neutrophils provoke lysis of these leukocytes, resulting in the release of their lytic enzymes, which in turn provoke tissue damage. Therefore, the role of neutrophils in this parasitic infection remains controversial. Neutrophils migrate from the circulation to sites of infection, where they display several antimicrobial functions, including phagocytosis, degranulation, and formation of neutrophil extracellular traps (NET). Recently, it was found that E. histolytica trophozoites are capable of inducing NET formation. Neutrophils in touch with amoebas launched NET in an explosive manner around the amoebas and completely covered them in nebulous DNA and cell aggregates where parasites got immobilized and killed. In addition, the phenotype of neutrophils can be modified by the microbiome resulting in protection against amoebas. This review describes the mechanisms of E. histolytica infection and discusses the novel view of how neutrophils are involved in innate immunity defense against amoebiasis. Also, the mechanisms on how the microbiome modulates neutrophil function are described.

Single-Cell RNA Sequencing Reveals that the Switching of the Transcriptional Profiles of Cysteine-Related Genes Alters the Virulence of Entamoeba histolytica

Studies on the trophozoite of Entamoeba histolytica suggested this organism could accumulate polyploid cells in its proliferative phase and differentiate its cell cycle from that of other eukaryotes. Therefore, a single-cell sequencing technique was used to study the switching of the RNA transcription profiles of single amoebic trophozoites.

Entamoeba histolytica is an intestinal protozoan that causes human amoebic colitis and extraintestinal abscesses. Virulence variation is observed in the pathogenicity of E. histolytica trophozoites, but the detailed mechanism remains unclear. Here, a single trophozoite was cultured alone, and the progeny of the trophozoites of each generation were subjected to single-cell RNA sequencing (scRNA-seq) to study the transcriptional profiles of trophozoites. The scRNA-seq analysis indicated the importance of sulfur metabolism and the proteasome pathway in pathogenicity, whereas the isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis did not identify the bulk trophozoites. The trophozoite improved the synthesis of cysteine under cysteine-deficient conditions but downregulated the expression of the intermediate subunit of the lectin of E. histolytica trophozoites and retained the expression of the heavy subunit of lectin, resulting in decreased amoebic phagocytosis and cytotoxicity. The variation in the transmembrane kinase gene family might be critical in regulating the proteasome pathway. Thus, the scRNA-seq technique provided an improved understanding of the biological characteristics and the mechanism of virulence variation of amoebic trophozoites.

IMPORTANCE Studies on the trophozoite of Entamoeba histolytica suggested this organism could accumulate polyploid cells in its proliferative phase and differentiate its cell cycle from that of other eukaryotes. Therefore, a single-cell sequencing technique was used to study the switching of the RNA transcription profiles of single amoebic trophozoites. We separated individual trophozoites from axenic cultured trophozoites, CHO cell-incubated trophozoites, and in vivo trophozoites. We found important changes in the sulfur and cysteine metabolism in pathogenicity. The trophozoites strategically regulated the expression of the cysteine-rich protein-encoding genes under cysteine-deficient conditions, thereby decreasing amoebic phagocytosis and cytotoxicity. The single-cell sequencing technique shows evident advantages in comparison with the isobaric tags for relative and absolute quantitation (iTRAQ) proteomic technology (bulk trophozoite level) and reveals the regulation strategy of trophozoites in the absence of exogenous cysteine. This regulation strategy may be the mechanism of virulence variation of amoebic trophozoites.

Interaction between human mucins and parasite glycoproteins: the role of lectins and glycosidases in colonization by intestinal protozoa

Intestinal mucins are the first line of defense against microorganisms. Although knowledge about the mechanisms involved in the establishment of intestinal protozoa is limited, there is evidence that these parasites produce lectin-like molecules and glycosidases, that exert both, constitutive and secretory functions, promoting the establishment of these microorganisms. In the present review, we analyse the main interactions between mucins of the host intestine and the four main protozoan parasites in humans and their implications in intestinal colonization. There are lectin-like molecules that contain complex oligosaccharide structures and N-acetylglucosamine (GlcNAc), mannose and sialic acid as main components, which are excreted/secreted by Giardia intestinalis, and recognized by the host using mannose-binding lectins (MBL). Entamoeba histolytica and Cryptosporidium spp. express the lectin galactose/N-acetyl-D-galactosamine, which facilitates their adhesion to cells. In Cryptosporidium, the glycoproteins gp30, gp40/15 and gp900 and the glycoprotein lectin CpClec are involved in protozoan adhesion to intestinal cells, forming an adhesion-attack complex. G. intestinalis and E. histolytica can also produce glycosidases such as β-N-acetyl-D-glucosaminidase, α-d-glucosidase, β-d-galactosidase, β-l-fucosidase, α-N-acetyl-d-galactosaminidase and β-mannosidase. In Blastocystis, α-D-mannose, α-D-glucose, GlcNAc, α-D-fucose, chitin and sialic acid that have been identified on their surface. Fucosidases, hexosaminidases and polygalacturonases, which may be involved in the mucin degradation process, have also been described in the Blastocystis secretoma. Similarly, symbiotic coexistence with the intestinal microbiota promotes the survival of parasites facilitating cell invasion and nutrients obtention. Furthermore, it is necessary to identify and characterize more glycosidases, which have been only partially described by in silico analyses of the parasite genome.

Intestinal amoebiasis: 160 years of its first detection and still remains as a health problem in developing countries

Amoebiasis is a parasitic disease caused by Entamoeba histolytica (E. histolytica), an extracellular enteric protozoan. This infection mainly affects people from developing countries with limited hygiene conditions, where it is endemic. Infective cysts are transmitted by the fecal-oral route, excysting in the terminal ileum and producing invasive trophozoites (amoebae). E. histolytica mainly lives in the large intestine without causing symptoms; however, possibly as a result of so far unknown signals, the amoebae invade the mucosa and epithelium causing intestinal amoebiasis. E. histolytica possesses different mechanisms of pathogenicity for the adherence to the intestinal epithelium and for degrading extracellular matrix proteins, producing tissue lesions that progress to abscesses and a host acute inflammatory response. Much information has been obtained regarding the virulence factors, metabolism, mechanisms of pathogenicity, and the host immune response against this parasite; in addition, alternative treatments to metronidazole are continually emerging. An accesible and low-cost diagnostic method that can distinguish E. histolytica from the most nonpathogenic amoebae and an effective vaccine are necessary for protecting against amoebiasis. However, research about the disease and its prevention has been a challenge due to the relationship between E. histolytica and the host during the distinct stages of the disease is multifaceted. In this review, we analyze the interaction between the parasite, the human host, and the colon microbiota or pathogenic microorganisms, which together give rise to intestinal amoebiasis.

Entamoeba histolytica Cyclooxygenase-Like Protein Regulates Cysteine Protease Expression and Virulence

The intestinal protozoan parasite Entamoeba histolytica (Eh) causes amebiasis associated with severe diarrhea and/or liver abscess. Eh pathogenesis is multifactorial requiring both parasite virulent molecules and host-induced innate immune responses. Eh-induced host pro-inflammatory responses plays a critical role in disease pathogenesis by causing damage to tissues allowing parasites access to systemic sites. Eh cyclooxygenase (EhCox) derived prostaglandin E2 stimulates the chemokine IL-8 from mucosal epithelial cells that recruits neutrophils to the site of infection to exacerbate disease. At present, it is not known how EhCox is regulated or whether it affects the expression of other proteins in Eh. In this study, we found that gene silencing of EhCox (EhCoxgs) markedly increased endogenous cysteine protease (CP) protein expression and virulence without altering CP gene transcripts. Live virulent Eh pretreated with arachidonic acid substrate to enhance PGE2 production or aspirin to inhibit EhCox enzyme activity or addition of exogenous PGE2 to Eh had no effect on EhCP activity. Increased CP enzyme activity in EhCoxgs was stable and significantly enhanced erythrophagocytosis, cytopathic effects on colonic epithelial cells and elicited pro-inflammatory cytokines in mice colonic loops. Acute infection with EhCoxgs in colonic loops increased inflammation associated with high levels of myeloperoxidase activity. This study has identified EhCox protein as one of the important endogenous regulators of cysteine protease activity. Alterations of CP activity in response to Cox gene silencing may be a negative feedback mechanism in Eh to limit proteolytic activity during colonization that can inadvertently trigger inflammation in the gut.

Rab GTPases take centre stage in understanding Entamoeba histolytica biology

Rab GTPases constitute the largest subgroup in the Ras superfamily of GTPases. It is well established that different Rab GTPases are localized in discrete subcellular localization and regulate the membrane trafficking in nearly all eukaryotic cells. Rab GTPase diversity is often regarded as an expression of vesicular trafficking complexity. The pathogenic amoeba Entamoeba histolytica harbours 91 Rab GTPases which is the highest among the currently available genome sequences from the eukaryotic kingdom. Here, we review the current status of amoebic Rab GTPases diversity, unique biochemical and structural features and summarise their predicted regulators. We discuss how amoebic Rab GTPases are involved in cellular processes such as endocytosis, phagocytosis, and invasion of host cellular components, which are essential for parasite survival and virulence.

Molecular characterization of Trichinella spiralis galectin and its participation in larval invasion of host's intestinal epithelial cells

The aim of this study was to study the molecular characteristics of Trichinella spiralis galectin (Tsgal) and interactions between Tsgal and host's intestinal epithelial cells (IECs). The functional domain of Tsgal was cloned and expressed in an E. coli system. The Tsgal was 97.1% identity to the galectin of T. nativa and 20.8% identity to the galectin-8 of humans. Conserved domain analysis revealed that Tsgal belongs to TR-type galectin and has two carbon recognized domain. The rTsgal with 29.1 kDa could be recognized by T. spiralis-infected mice at 42 days post-infection (dpi). The transcription and expression of Tsgal gene was detected by RT-PCR and Western blotting in all T. spiralis developmental stages (intestinal infective larvae, adult worms, newborn larvae, and muscle larvae). The IFA results revealed that Tsgal was mainly located at the cuticles and stichosomes of T. spiralis larvae (ML, IIL and NBL). The rTsgal had hemagglutinating function for erythrocytes from human, rabbit and mouse. The results of Far Western blot and confocal microscopy indicated there was specific binding between rTsgal and IECs, and the binding was located the membrane and cytoplasm of the IECs. Out of four sugars (sucrose, glucose, lactose and maltose), only lactose was able to inhibit the rTsgal agglutinating role for human type B erythrocytes. Moreover, the rTsgal could promote the larval invasion of IECs, while the anti-rTsgal serum inhibited the larval invasion. These results demonstrated that Tsgal might participate in the T. spiralis invasion of intestinal epithelium in early infection stage.

Entamoeba histolytica: Host parasite interactions at the colonic epithelium

Entamoeba histolytica (Eh) is the protozoan parasite responsible for intestinal amebiasis and interacts dynamically with the host intestinal epithelium during disease pathogenesis. A multifaceted pathogenesis profile accounts for why 90% of individuals infected with Eh are largely asymptomatic. For 100 millions individuals that are infected each year, key interactions within the intestinal mucosa dictate disease susceptibility. The ability for Eh to induce amebic colitis and disseminate into extraintestinal organs depends on the parasite competing with indigenous bacteria and overcoming the mucus barrier, binding to host cells inducing their cell death, invasion through the mucosa and outsmarting the immune system. In this review we summarize how Eh interacts with the intestinal epithelium and subverts host defense mechanisms in disease pathogenesis.

Characteristics of inflammatory reactions during development of liver abscess in hamsters inoculated with Entamoeba nuttalli

Background

Entamoeba nuttalli is an intestinal protozoan with pathogenic potential that can cause amebic liver abscess. It is highly prevalent in wild and captive macaques. Recently, cysts were detected in a caretaker of nonhuman primates in a zoo, indicating that E. nuttalli may be a zoonotic pathogen. Therefore, it is important to evaluate the pathogenicity of E. nuttalli in detail and in comparison with that of E. histolytica.

Methodology/Principal findings

Trophozoites of E. nuttalli GY4 and E. histolytica SAW755 strains were inoculated into liver of hamsters. Expression levels of proinflammatory factors of hamsters and virulence factors from E. histolytica and E. nuttalli were compared between the two parasites. Inoculations with trophozoites of E. nuttalli resulted in an average necrotic area of 24% in liver tissue in 7 days, whereas this area produced by E. histolytica was nearly 50%. Along with the mild liver tissue damage induced by E. nuttalli, expression levels of proinflammatory factors (TNF-α, IL-6 and IL-1β) and amebic virulence protein genes (lectins, cysteine proteases and amoeba pores) in local tissues were lower with E. nuttalli in comparison with E. histolytica. In addition, M2 type macrophages were increased in E. nuttalli-induced amebic liver abscesses in the late stage of disease progression and lysate of E. nuttalli trophozoites induced higher arginase expression than E. histolytica in vitro.

Conclusions/Significance

The results show that differential secretion of amebic virulence proteins during E. nuttalli infection triggered lower levels of secretion of various cytokines and had an impact on polarization of macrophages towards a M1/M2 balance. However, regardless of the degree of macrophage polarization, there is unambiguous evidence of an intense acute inflammatory reaction in liver of hamsters after infection by both Entamoeba species.

Entamoeba nuttalli is the phylogenetically closest protozoan to Entamoeba histolytica and is highly prevalent in macaques. Previous studies have indicated that E. nuttalli is virulent in a hamster model. In this study, we compared the immunopathological basis of formation of liver abscess in hamsters between E. nuttalli and E. histolytica. Mild liver tissue damage developed after intrahepatic injection of trophozoites of E. nuttalli, and lower expression levels of genes for host proinflammatory factors and amebic virulence proteins were detected at the edges of liver abscesses induced by E. nuttalli. In addition, alternatively activated macrophages were increased in E. nuttalli-induced liver abscesses in the late stage of disease progression. The lysate of E. nuttalli trophozoites also induced higher arginase expression than E. histolytica in vitro. Polarization of macrophages is likely to affect the degree of acute inflammatory reactions in liver in an animal model during E. nuttalli infection. Our data reveal new characteristics of abscess formation by E. nuttalli.

Toll-like receptors participate in Naegleria fowleri recognition

Naegleria fowleri is a protozoan that invades the central nervous system and causes primary amoebic meningoencephalitis. It has been reported that N. fowleri induces an important inflammatory response during the infection. In the present study, we evaluated the roles of Toll-like receptors in the recognition of N. fowleri trophozoites by human mucoepithelial cells, analyzing the expression and production of innate immune response mediators. After amoebic interactions with NCI-H292 cells, the expression and production levels of IL-8, TNF-α, IL-1β, and human beta defensin-2 were evaluated by RT-PCR, ELISA, immunofluorescence, and dot blot assays, respectively. To determine whether the canonical signaling pathways were engaged, we used different inhibitors, namely, IMG-2005 for MyD88 and BAY 11-7085 for the nuclear factor NFkB. Our results showed that the expression and production of the pro-inflammatory cytokines and beta defensin-2 were induced by N. fowleri mainly through the canonical TLR4 pathway in a time-dependent manner.

Targeting and Recognition of Toll-Like Receptors by Plant and Pathogen Lectins

We have reported that some lectins act as agonists of toll-like receptors (TLRs) and have immunomodulatory properties. The plant lectin ArtinM, for example, interacts with N-glycans of TLR2, whereas other lectins of microbial origin interact with TLR2 and TLR4. Expression of the receptors on the surface of antigen-presenting cells exposes N-glycans that may be targeted by lectins of different structures, specificities, and origins. In vitro, these interactions trigger cell signaling that leads to NF-κB activation and production of the Th1 polarizing cytokine IL-12. In vivo, a same sequence of events follows the administration of an active lectin to mice infected with an intracellular pathogen, conferring resistance to the pathogen. The lectins of the human pathogens Toxoplasma gondii (TgMIC1 and TgMIC4) and Paracoccidioides brasiliensis (Paracoccin), by recognition and activation of TLR2 and TLR4, induce cell events and in vivo effects comparable to the promoted by the plant lectin ArtinM. In this article, we highlight these two distinct mechanisms for activating antigen-presenting cells. On the one hand, TLRs act as sensors for the presence of conventional pathogen-associated molecular patterns, such as microbial lipids. On the other hand, we showed that TLR-mediated cell activation might be triggered by an alternative way, in which lectins bind to TLRs N-glycans and stimulate cells to increase the expression of pro-inflammatory cytokines. This process may lead to the development of new pharmaceutical tools that promote protective immune responses directed against intracellular pathogens and tumors.

Role of EhRab7A in phagocytosis of type 1 fimbriated E. coli by Entamoeba histolytica

Entamoeba histolytica, the causative agent of amoebic colitis and liver abscess in human, ingests the intestinal bacteria and variety of host cells. Phagocytosis of bacteria by the amebic trophozoite has been reported to be important for the virulence of the parasite. Here, we set out to characterize different stages of phagocytosis of type 1 E. coli and investigated the role of a set of amoebic Rab GTPases in the process. The localizations of the Rab GTPases during different stages of the phagocytosis were investigated using laser scanning confocal microscopy and their functional relevance were determined using fluorescence activated cell sorter based assay as well as colony forming unit assay. Our results demonstrate that EhRab7A is localized on the phagosomes and involved in both early and late stages of type 1 E. coli phagocytosis. We further showed that the E. coli or RBC containing phagosomes are distinct from the large endocytic vacuoles in the parasite which are exclusively used to transport human holotransferrin and low density lipoprotein. Remarkably, type 1 E. coli uptake was found to be insensitive to cytochalasin D treatment, suggesting that the initial stage of E. coli phagocytosis is independent of the formation of actin filaments.

Immune Response of Amebiasis and Immune Evasion by Entamoeba histolytica

Entamoeba histolytica is a protozoan parasite and the causative agent of amebiasis. It is estimated approximately 1% of humans are infected with E. histolytica, resulting in an estimate of 100,000 deaths annually. Clinical manifestations of amebic infection range widely from asymptomatic to severe symptoms, including dysentery and extra-intestinal abscesses. Like other infectious diseases, it is assumed that only ~20% of infected individuals develop symptoms, and genetic factors of both the parasite and humans as well as the environmental factors, e.g., microbiota, determine outcome of infection. There are multiple essential steps in amebic infection: degradation of and invasion into the mucosal layer, adherence to the intestinal epithelium, invasion into the tissues, and dissemination to other organs. While the mechanisms of invasion and destruction of the host tissues by the amebae during infection have been elucidated at the molecular levels, it remains largely uncharacterized how the parasite survive in the host by evading and attacking host immune system. Recently, the strategies for immune evasion by the parasite have been unraveled, including immunomodulation to suppress IFN-γ production, elimination of immune cells and soluble immune mediators, and metabolic alterations against reactive oxygen and nitrogen species to fend off the attack from immune system. In this review, we summarized the latest knowledge on immune reaction and immune evasion during amebiasis.

Bjcul, a snake venom lectin, modulates monocyte-derived macrophages to a pro-inflammatory profile in vitro

Macrophages are cells of high plasticity and can act in different ways to ensure that the appropriate immune response remains controlled. This study shows the effects of the C-type Bothrops jararacussu venom lectin (BJcuL) on the activation of human macrophages derived from the U937 cell line. BJcuL binds on the cell surface, and this event is inhibited by its specific carbohydrate. It induced phagocytosis and production of H2O2, and expression of antigen presentation molecules. It also enhanced the production of TNF-α, GM-CSF and IL-6 by macrophages and indirectly induced T cells to an increased production of TNF-α, IFN-γ and IL-6 in the presence of LPS. Our results suggest that BJcuL can modulate macrophage functional activation towards an M1 state.

The Interplay of Host Microbiota and Parasitic Protozoans at Mucosal Interfaces: Implications for the Outcomes of Infections and Diseases

Infections by parasitic protozoans are largely neglected, despite threatening millions of people, particularly in developing countries. With descriptions of the microbiota in humans, a new frontier of investigation is developing to decipher the complexity of host-parasite-microbiota relationships, instead of the classic reductionist approach, which considers host-parasite in isolation. Here, we review with specific examples the potential roles that the resident microbiota can play at mucosal interfaces in the transmission of parasitic protozoans and in the progress of infection and disease. Although the mechanisms underlying these relationships remain poorly understood, some examples provide compelling evidence that specific components of the microbiota can potentially alter the outcomes of parasitic infections and diseases in humans. Most findings suggest a protective role of the microbiota, which might lead to exploratory research comprising microbiota-based interventions to prevent and treat protozoal infections in the future. However, these infections are often accompanied by an unbalanced microbiota and, in some specific cases, apparently, these bacteria may contribute synergistically to disease progression. Taken together, these findings provide a different perspective on the ecological nature of protozoal infections. This review focuses attention on the importance of considering polymicrobial associations, i.e., parasitic protozoans and the host microbiota, for understanding these human infections in their natural microbial context.

A surface membrane protein of Entamoeba histolytica functions as a receptor for human chemokine IL-8: its role in the attraction of trophozoites to inflammation sites

Entamoeba histolytica trophozoites respond to the presence of IL-8, moving by chemotaxis towards the source of the chemokine. IL-8 binds to the trophozoite membrane and triggers a response that activates signaling pathways that in turn regulate actin/myosin cytoskeleton organisation to initiate migration towards the chemokine, suggesting the presence of a receptor for IL-8 in the parasite. Antibodies directed to the human IL-8 receptor (CXCR1) specifically recognised a 29 kDa protein in trophozoite membrane fractions. The same protein was immunoprecipitated by this antibody from total amebic extracts. Peptide analysis of the immunoprecipitated protein revealed a sequence with high homology to a previously identified amebic outer membrane peroxiredoxin and a motif within the third loop of human CXCR1, which is an important site for IL-8 binding and activation of signaling processes. Immunodetection assays demonstrated that the anti-human CXCR1 antibody binds to the 29 kDa protein in a different but close site to where IL-8 binds to the trophozoite surface membrane, suggesting that human and amebic receptors for this chemokine share common epitopes. In the context of the human intestinal environment, a receptor for IL-8 could be a great advantage for E. histolytica trophozoite survival, as they could reach an inflammatory milieu containing abundant nutrients. In addition, it has been suggested that the high content of accessible thiol groups of the protein and its peroxidase activity could provide protection in the oxygen rich milieu of colonic lesions, allowing trophozoite invasion of other tissues and escape from the host immune response.

Differential modulation of avian β-defensin and Toll-like receptor expression in chickens infected with infectious bronchitis virus

The host innate immune response either clears invading viruses or allows the adaptive immune system to establish an effective antiviral response. In this study, both pathogenic (passage 3, P3) and attenuated (P110) infectious bronchitis virus (IBV) strains were used to study the immune responses of chicken to IBV infection. Expression of avian β-defensins (AvBDs) and Toll-like receptors (TLRs) in 16 tissues of chicken were compared at 7 days PI. The results showed that P3 infection upregulated the expression of AvBDs, including AvBD2, 4, 5, 6, 9, and 12, while P110 infection downregulated the expression of AvBDs, including AvBD3, 4, 5, 6, and 9 in most tissues. Meanwhile, the expression level of several TLRs showed a general trend of upregulation in the tissues of P3-infected chickens, while they were downregulated in the tissues of P110-infected chickens. The result suggested that compared with the P110 strain, the P3 strain induced a more pronounced host innate immune response. Furthermore, we observed that recombinant AvBDs (including 2, 6, and 12) demonstrated obvious anti-viral activity against IBV in vitro. Our findings contribute to the proposal that IBV infection induces an increase in the messenger RNA (mRNA) expression of some AvBDs and TLRs, which suggests that AvBDs may play significant roles in the resistance of chickens to IBV replication.

Entamoeba histolytica: adhesins and lectins in the trophozoite surface

Entamoeba histolytica is the causative agent of amebiasis in humans and is responsible for 100,000 deaths annually, making it the third leading cause of death due to a protozoan parasite. Pathogenesis appears to result from the potent cytotoxic activity of the parasite, which kills host cells within minutes. Although the mechanism is unknown, it is well established to be contact-dependent. The life cycle of the parasite alternates with two forms: the resistant cyst and the invasive trophozoite. The adhesive interactions between the parasite and surface glycoconjugates of host cells, as well as those lining the epithelia, are determinants for invasion of human tissues, for its cytotoxic activity, and finally for the outcome of the disease. In this review we present an overview of the information available on the amebic lectins and adhesins that are responsible of those adhesive interactions and we also refer to their effect on the host immune response. Finally, we present some concluding remarks and perspectives in the field.

Galatrox is a C-type lectin in Bothrops atrox snake venom that selectively binds LacNAc-terminated glycans and can induce acute inflammation

Previous studies indicate that snake venom contains glycan-binding proteins (GBPs), although the binding specificity and biological activities of many of these GBPs is unclear. Here we report our studies on the glycan binding specificity and activities of galatrox, a Bothrops atrox snake venom-derived GBP. Glycan microarray analysis indicates that galatrox binds most strongly to glycans expressing N-acetyllactosamine (LacNAc), with a significant preference for Galβ1-4GlcNAcβ over Galβ1-3GlcNAcβ compounds. Galatrox also bound immobilized laminin, a LacNAc-dense extracellular matrix component, suggesting that this GBP can bind LacNAc-bearing glycoproteins. As several endogenous mammalian GBPs utilize a similar binding LacNAc binding preference to regulate neutrophil and monocyte activity, we hypothesized that galatrox may mediate B. atrox toxicity through regulation of leukocyte activity. Indeed, galatrox bound neutrophils and promoted leukocyte chemotaxis in a carbohydrate-dependent manner. Similarly, galatrox administration into the mouse peritoneal cavity induced significant neutrophil migration and the release of pro-inflammatory cytokines IL-1α and IL-6. Exposure of bone marrow-derived macrophages to galatrox induced generation of pro-inflammatory mediators IL-6, TNF-α, and keratinocyte-derived chemokine. This signaling by galatrox was mediated via its carbohydrate recognition domain by activation of the TLR4-mediated MyD88-dependent signaling pathway. These results indicate that galatrox has pro-inflammatory activity through its interaction with LacNAc-bearing glycans on neutrophils, macrophages and extracellular matrix proteins and induce the release of pro-inflammatory mediators.

Regulation of virulence of Entamoeba histolytica

Entamoeba histolytica is the third-leading cause of parasitic mortality globally. E. histolytica infection generally does not cause symptoms, but the parasite has potent pathogenic potential. The origins, benefits, and triggers of amoebic virulence are complex. Amoebic pathogenesis entails depletion of the host mucosal barrier, adherence to the colonic lumen, cytotoxicity, and invasion of the colonic epithelium. Parasite damage results in colitis and, in some cases, disseminated disease. Both host and parasite genotypes influence the development of disease, as do the regulatory responses they govern at the host-pathogen interface. Host environmental factors determine parasite transmission and shape the colonic microenvironment E. histolytica infects. Here we highlight research that illuminates novel links between host, parasite, and environmental factors in the regulation of E. histolytica virulence.

Toll-like receptor signaling activation by Entamoeba histolytica induces beta defensin 2 in human colonic epithelial cells: its possible role as an element of the innate immune response

Background

Entamoeba histolytica, a protozoan parasite of humans, produces dysenteric diarrhea, intestinal mucosa damage and extraintestinal infection. It has been proposed that the intestinal microbiota composition could be an important regulatory factor of amebic virulence and tissue invasion, particularly if pathogenic bacteria are present. Recent in vitro studies have shown that Entamoeba histolytica trophozoites induced human colonic CaCo2 cells to synthesize TLR-2 and TLR-4 and proinflammatory cytokines after binding to the amebic Gal/GalNac lectin carbohydrate recognition domain. The magnitude of the inflammatory response induced by trophozoites and the subsequent cell damage were synergized when cells had previously been exposed to pathogenic bacteria.

Methodology/Principal Findings

We show here that E. histolytica activation of the classic TLR pathway in CaCo2 cells is required to induce β defensin-2 (HBD2) mRNA expression and production of a 5-kDa cationic peptide with similar properties to the antimicrobial HBD2 expressed by CaCo2 cells exposed to enterotoxigenic Escherichia coli. The induced peptide showed capacity to permeabilize membranes of bacteria and live trophozoites. This activity was abrogated by inhibition of TLR2/4-NFκB pathway or by neutralization with an anti-HBD2 antibody.

Conclusions/Significance

Entamoeba histolytica trophozoites bind to human intestinal cells and induce expression of HBD2; an antimicrobial molecule with capacity to destroy pathogenic bacteria and trophozoites. HDB2's possible role as a modulator of the course of intestinal infections, particularly in mixed ameba/bacteria infections, is discussed.

Entamoeba histolytica ameba/bacteria mixed intestinal infections are common in endemic regions of Amebiasis. Recent investigations support the idea that pathogen interplay in these infections may have a role in invasive disease, activating signals that increase intestinal inflammation. We have studied interactions of amebic trophozoites with human colonic CaCo2 cells, using as positive control pathogenic intestinal bacteria E. coli (ETEC). Both pathogens activated a chain of chemical reactions in the cells that led to production of the antimicrobial peptide β defensin-2 (HBD2), an element of the innate immune response. Pathogen activation of CaCo2 cell response and production of HBD2 were analyzed employing biochemical, cell, molecular biology, and immunology methods. Amebas induced HBD2 via the same classic Toll-receptor signaling pathway activated by ETEC. Amebic-induced HBD2 showed capacity to permeabilize and cause severe damage to bacteria and ameba membranes. Although this study was done in vitro, due to lack of an adequate animal model in which to monitor ameba/bacteria interactions, it provides a new insight into intestinal infections, showing that presence of amebas induces synthesis of elements of an innate immune response that could affect the equilibrium of the intestinal microbiota and modify the course of intestinal infections by other pathogens.

The role of Galactose in human health and disease

According to the universal biological findings, cellular bodies are covered with an intense coating of glycans. Diversity of glycan chains, linked to lipids and proteins is due to isomeric and conformational modifications of various sugar residues, giving rise to unique carbohydrate structures with a wide range of sequences and anomeric configurations. Proteins and lipids, carrying specific sugar residues (like Galactose) with particular stereochemical properties (sequence, anomery and linkages) are involved in broad spectrums of biological processes, including intercellular and intracellular interactions, microbial adhesion and cellular signaling. By studying the role of specific seterochemical features of galactose (Gal), we have improved our understanding about the normal physiology and diseases in human bodies.