No abstract available.
Animals ; Apoptosis/*physiology ; Claudins/*metabolism ; Colitis/*physiopathology ; Intestinal Mucosa/*physiopathology ; Mannose-Binding Lectin/*immunology

OBJECTIVETo purify Mannan-binding lectin (MBL) from human serum and detect its binding ability to several kinds of bacteria common in infectious diseases of children.

METHODSMBL was purified from human serum by affinity chromatography on mannan-Sepharose 4B column. Its binding ability to eight species, 97 strains of bacteria was detected by enzyme-linked lectin assay (ELLA).

RESULTSMBL has different binding ability to bacteria and shows strong binding ability to Klebsiella ornithinolytica and Escherichia coli, but shows relatively lower binding ability to Staphylococcus haemolyticus, Enterobacter cloacae and Staphylococcus epidermidis. To different isolates of Klebsiella pneumoniae, Haemophilus influenzae and Staphylococcus aureus, MBL shows quite different binding ability.

CONCLUSIONSMBL has different binding ability to different bacteria, and has relatively stronger binding ability to Gram-negative bacteria. Its binding ability to different isolates of certain kinds of bacteria is quite different.

Bacteria ; classification ; metabolism ; Child ; Child, Preschool ; Communicable Diseases ; microbiology ; Humans ; Mannose-Binding Lectin ; blood ; metabolism ; Protein Binding ; Species Specificity

OBJECTIVETo prepare the trimeric subunits of recombinant human mannan-binding lectin (MBL) with biological activities.

METHODSA prokaryotic expression vector containing human MBL N-terminal deletant (rhMBLδN) gene we previously constructed was transformed into E. coli for efficient expression of rhMBLδN fusion protein. Based on the principle that the collagen polypeptides tend to self-assembly into the tertiary structure of proteins by forming a triple helix due to the characteristic properties of the collagen proteins, rhMBLδN fusion protein was limitedly hydrolyzed with thrombin. The obtained rhMBLδN polypeptide was repeatedly dialyzed in 50 mmol/L PBS (pH7.2) and ddH(2)O, and the final product was analyzed for its bioactivities using a ligand-binding assay and a C4d deposition assay.

RESULTSrhMBLδN polypeptide with a relative molecular mass of about 20 000 was obtained by limited proteolysis of rhMBLδN fusion protein with thrombin. Repeated dialyses of rhMBLδN polypeptides in 50 mmol/L PBS and ddH(2)O resulted in the isolation of the trimeric subunit trhMBLδN (with a relative molecular mass of about 50 000), which contained a collagen-like helix. The trhMBLδN protein had a higher ligand-binding activity than rhMBLδN polypeptide, and acquired the activity to initiate the lectin pathway of complement activation, but the activities were lower than those of natural MBL.

CONCLUSIONWe have successfully obtained the bioactive trimeric subunit of rhMBL, trhMBLδN, and this structural subunit is also the functional subunit of the MBL molecule.

Complement Activation ; Escherichia coli ; metabolism ; Genetic Vectors ; Humans ; Mannose-Binding Lectin ; biosynthesis ; genetics ; isolation & purification ; Recombinant Proteins ; biosynthesis

Mannan-binding lectin (MBL) is a soluble innate immune protein that binds to glycosylated targets. MBL acts as an opsonin and activates complement, contributing to the destruction and clearance of infecting microorganisms. Hepatitis C virus (HCV) encodes two envelope glycoproteins E1 and E2, expressed as non-covalent E1/E2 heterodimers in the viral envelope. E1 and E2 are potential ligands for MBL. Here we describe an analysis of the interaction between HCV and MBL using recombinant soluble E2 ectodomain fragment, the full-length E1/E2 heterodimer, expressed in vitro, and assess the effect of this interaction on virus entry. A binding assay using antibody capture of full length E1/E2 heterodimers was used to demonstrate calcium dependent, saturating binding of MBL to HCV glycoproteins. Competition with various saccharides further confirmed that the interaction was via the lectin domain of MBL. MBL binds to E1/E2 representing a broad range of virus genotypes. MBL was shown to neutralize the entry into Huh-7 cells of HCV pseudoparticles (HCVpp) bearing E1/E2 from a wide range of genotypes. HCVpp were neutralized to varying degrees. MBL was also shown to neutralize an authentic cell culture infectious virus, strain JFH-1 (HCVcc). Furthermore, binding of MBL to E1/E2 was able to activate the complement system via MBL-associated serine protease 2. In conclusion, MBL interacts directly with HCV glycoproteins, which are present on the surface of the virion, resulting in neutralization of HCV particles.
Binding, Competitive ; Glycosylation ; Hepacivirus ; genetics ; pathogenicity ; physiology ; Humans ; Mannose-Binding Lectin ; metabolism ; Mannose-Binding Protein-Associated Serine Proteases ; metabolism ; Monosaccharides ; metabolism ; Protein Binding ; Protein Multimerization ; Tumor Cells, Cultured ; Viral Envelope Proteins ; metabolism ; Virion ; pathogenicity ; physiology ; Virus Internalization

The study was aimed to investigate the mechanism of mannan-binding lectin (MBL) on bacterial lipopolysaccharide (LPS)-induced human peripheral blood monocyte-derived dendritic cell (DC) maturation. The monocytes were prepared from the peripheral blood of healthy adult volunteers. The immature dendritic cells (imDC) were induced by 5-day-culture in medium supplemented with rhGM-CSF and rhIL-4. FACS was used to investigate the interaction of MBL with imDC and the impact of MBL on LPS binding to imDC. ELISA and Western blot was used to analyze the interaction of MBL with soluble TLR4 ectodomain protein (sTLR4); Western blot was used to detect LPS-induced NF-κB translocation in imDC. The results showed that MBL could directly bind to imDC in the presence of calcium. sTLR4 protein or LPS could competitively inhibit the binding of MBL to imDC. ELISA and Western blot showed that MBL could evidently bind to sTLR4 protein in a concentration-dependent manner. FACS showed that MBL could competitively inhibit the binding of LPS to imDC by binding to imDC directly. Western blot showed that MBL decreased LPS-induced NF-κB translocation in imDC. It is concluded that MBL may competitively inhibit the binding of LPS to imDC by binding to TLR4 expressed on imDC, resulted in inhibition of LPS-induced DC maturation, suggesting that MBL can regulate DC maturation through ligand-binding. This study provides the good foundation to clarify the mechanism of MBL inhibiting the LPS-induced DC maturation.
Cell Differentiation ; Cells, Cultured ; Dendritic Cells ; cytology ; drug effects ; metabolism ; Humans ; Ligands ; Lipopolysaccharides ; adverse effects ; Mannose-Binding Lectin ; pharmacology ; Monocytes ; cytology ; metabolism ; Toll-Like Receptor 4 ; metabolism

Acanthamoeba spp. are single-celled protozoan organisms that are widely distributed in the environment. In this study, to understand functional roles of a mannose-binding protein (MBP), Acanthamoeba castellanii was treated with methyl-alpha-D-mannopyranoside (mannose), and adhesion and cytotoxicity of the amoeba were analyzed. In addition, to understand the association of MBP for amoeba phagocytosis, phagocytosis assay was analyzed using non-pathogenic bacterium, Escherichia coli K12. Amoebae treated with mannose for 20 cycles exhibited larger vacuoles occupying the most area of the amoebic cytoplasm in comparison with the control group amoebae and glucose-treated amoebae. Mannose-selected amoebae exhibited lower levels of binding to Chinese hamster ovary (CHO) cells. Exogenous mannose inhibited >50% inhibition of amoebae (control group) binding to CHO cells. Moreover, exogenous mannose inhibited amoebae (i.e., man-treated) binding to CHO cells by <15%. Mannose-selected amoebae exhibited significantly decreased cytotoxicity to CHO cells compared with the control group amoebae, 25.1% vs 92.1%. In phagocytic assay, mannose-selected amoebae exhibited significant decreases in bacterial uptake in comparison with the control group, 0.019% vs 0.03% (P<0.05). Taken together, it is suggested that mannose-selected A. castellanii trophozoites should be severely damaged and do not well interact with a target cell via a lectin of MBP.
Acanthamoeba castellanii/drug effects/metabolism/*pathogenicity ; Amebiasis/*parasitology ; Animals ; CHO Cells ; Cell Adhesion/drug effects ; Cell Survival ; Cricetinae ; Cricetulus ; Escherichia coli K12/metabolism ; Female ; Mannose/*pharmacology ; Mannose-Binding Lectin/*metabolism ; Phagocytosis ; Protozoan Proteins/metabolism

BACKGROUND/AIMS: This animal study aimed to define the underlying cellular mechanisms of intestinal barrier dysfunction. METHODS: Rats were fed 4% with dextran sodium sulfate (DSS) to induce experimental colitis. We analyzed the sugars in 24-hour urine output by high pressure liquid chromatography. The expression of claudins, mannan-binding lectin (MBL), and MBL-associated serine proteases 2 (MASP-2) were detected in the colonic mucosa by immunohistochemistry; and apoptotic cells in the colonic epithelium were detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method assay. RESULTS: The lactulose and sucralose excretion levels in the urine of rats with DSS-induced colitis were significantly higher than those in the control rats. Mannitol excretion was lower and lactulose/mannitol ratios and sucralose/mannitol ratios were significantly increased compared with those in the control group (p<0.05). Compared with the controls, the expression of sealing claudins (claudin 3, claudin 5, and claudin 8) was significantly decreased, but that of claudin 1 was increased. The expression of pore-forming claudin 2 was upregulated and claudin 7 was downregulated in DSS-induced colitis. The epithelial apoptotic ratio was 2.8%+/-1.2% in controls and was significantly increased to 7.2%+/-1.2% in DSS-induced colitis. The expression of MBL and MASP-2 in the intestinal mucosa showed intense staining in controls, whereas there was weak staining in the rats with colitis. CONCLUSIONS: There was increased intestinal permeability in DSS-induced colitis. Changes in the expression and distribution of claudins, increased epithelial apoptosis, and the MASP-2-induced immune response impaired the intestinal epithelium and contributed to high intestinal permeability.
Animals ; Apoptosis/*physiology ; Claudins/*metabolism ; Colitis/chemically induced/immunology/*physiopathology ; Colon/immunology/physiopathology ; Dextran Sulfate ; Intestinal Mucosa/*physiopathology ; Lactulose/metabolism ; Mannitol/metabolism ; Mannose-Binding Lectin/*immunology ; Permeability ; Rats ; Rats, Sprague-Dawley ; Sucrose/analogs & derivatives/metabolism ; Up-Regulation

Mannose-binding lectin (MBL) plays an important role in immune defense. This study was undertaken to investigate the association between hepatitis B virus infection and polymorphisms of MBL gene. We assessed the single nucleotide polymorphism at codon 54 in exon 1 of MBL in patients with hepatitis B virus infection and HBsAg negative controls in Korean population. A total of 498 enrolled subjects was classified into four groups. Group 1; Clearance, Group 2; Inactive healthy carrier, Group 3; Chronic hepatitis, Group 4; Liver cirrhosis. MBL gene polymorphisms at codon 54 led to three genotypes (G/G, G/A, A/A). When we divided subjects into clearance group (group 1) and persistence group (group 2-4), G/G genotype and A-allele carrier were observed in 55.6% and 44.4% in clearance group, 64.8% and 35.2% in persistence group (p=0.081), respectively. When hepatitis B virus persistent cases were divided into inactive healthy carrier (group 2) and disease progression group (group 3 and 4), MBL gene polymorphisms at codon 54 were not related to disease progression (p=0.166). MBL gene polymorphism at codon 54 was not associated with the clearance of hepatitis B virus infection nor progression of disease in chronic hepatitis B virus infection.
Adult ; Alleles ; Codon ; Disease Progression ; Female ; Fibrosis ; Genotype ; Hepatitis ; Hepatitis B/*genetics/*metabolism ; Hepatitis B virus/*metabolism ; Heterozygote ; Humans ; Korea ; *Lectins ; Male ; Mannose-Binding Lectin/*chemistry/*genetics ; Middle Aged ; *Polymorphism, Genetic ; Polymorphism, Single Nucleotide ; Research Support, Non-U.S. Gov't

OBJECTIVETo express the carbohydrate recognition domain (CRD) of Balb/C mouse mannan binding lectin A (MBL-A) in E.coli.

METHODSThe target gene fragment was obtained by PCR from the plasmid pmMBL-A harboring mouse MBL-A gene. The PCR product was recombined with the prokaryotic expression vector pET-41a(+) and the resulting recombinant plasmid was identified by PCR, restriction analysis and sequencing before transformation into E.coli BL21(DE3) cell for expression of the target protein. After washing and renaturation, the protein was purified on GST-Tag purification resins and analyzed by SDS-PAGE, Western blotting and enzyme-linked immunosorbent assay (ELISA).

RESULTSA DNA fragment of about 450 bp was amplified by PCR and the recombinant plasmid pET41a-mMBL-A-CRD was constructed by linking the fragment with pET41a(+) vector. The result of restriction enzyme analysis and sequencing of the selected clones were consistent with those by computer analysis. The recombinant vector was expressed in E.coli BL21(DE3), and the expressed protein existed mainly as inclusion bodies, whose relative molecular mass was about 47,000 by SDS-PAGE analysis. After washing, renaturation and purification, the purity of recombinant protein was about 90%. Western blotting suggested immunoreactivity of the purified protein with anti-GST antibody, and its sugar binding activity was verified by ELISA.

CONCLUSIONWe have successfully obtained mouse MBL-A CRD protein, which provides the base for further functional study of the MBL-A molecule.

Animals ; Carbohydrates ; chemistry ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; Inclusion Bodies ; metabolism ; Mannose-Binding Lectin ; biosynthesis ; chemistry ; genetics ; Mice ; Mice, Inbred BALB C ; Recombinant Fusion Proteins ; biosynthesis ; chemistry ; genetics

The genomic DNA were extracted from the leaves of Polygonatum roseum (Liliaceae) in Xinjiang and the primers were designed according to conservative sequences of Polygonatum lectins gene. The complete ORF of Polygonatum roseum agglutinin (PRA) gene was amplified as a fragment of 550 bp, which was identical with predicted size. Like most of the plant lectin genes, there was no intron in the PRA gene. The ORF of the gene encoded 159 amino acid residues, in which included a signal sequence of 28 amino acid residues at its N-terminus. The cDNA sequence had 92% identities compared with the published sequence. The amino acid sequence and SWISS-MODEL analysis indicated that the three-dimensional structure of PRA strongly resembled with that of monocot mannose-binding lectins, which comprised with three antiparallel four-stranded beta-sheets arranged as a 12-stranded beta-barrel. The recombinant pGEX4T-1-PRA and pMAL-p2x-PRA prokaryotic expression vectors were constructed to produce GST-PRA and MBP-PRA fusion proteins in E. coli, respectively. SDS-PAGE of the fusion protein demonstrated that the PRA lectin protein migrated at a size of 14 kD. The immunization was performed by intra-muscular injection of pcDNA3-PRA, and the antiserum was detected by ELISA. Western blotting analysis showed the antiserum specifically bound the lectin protein. The establishment of such an expression system might provide materials for further investigation of the properties and functions of PRA proteins. It also laid the basis for plant genetic engineering on its defensive functions to pests and diseases.
Amino Acid Sequence ; Animals ; Base Sequence ; China ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Female ; Mannose-Binding Lectin ; biosynthesis ; genetics ; Mice ; Molecular Sequence Data ; Polygonatum ; chemistry ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; pharmacology ; Sequence Analysis