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

OBJECTIVETo explore the significance of plasma levels of mannan-binding lectin (MBL)-associated serine protease 2 (MASP2) in children with upper respiratory tract infection (URTI).

METHODSA total of 103 children with URTI and 35 healthy children were examined for plasma levels of MASP2 and C-reactive protein (CRP). According to CRP levels, white blood cell count (WBC), stage of infection, and administration of treatments, the children with URTI were divided into the elevated CRP group (n=48) and the normal CRP group (n=54), elevated WBC group (n=61) and normal WBC group (n=40), the early stage of infection without treatment group (n=68) and mid-late stage of infection with treatment group (n=35).

RESULTSPlasma MASP2 levels was significantly higher in URTI group than in the healthy control group (P<0.001) and showed a close correlation with age (r=0.302, P<0.01). Plasma MASP2 level was significantly correlated with CRP level in elevated CRP group (r=0.310, P<0.05) but not in normal CRP group (P>0.05), correlated with WBC in elevated WBC group (r=0.392, P<0.01) but not in normal WBC group (P>0.05), and was significantly higher in early stage infection without treatment group than in mid-late stage of infection with treatment group (P<0.01). MASP2, MBL2 and CRP genes had a common binding site for the transcription factor HNF-4α.

CONCLUSIONSMASP2 may be an acute-phase protein, and its plasma level might serve as a new reference index in the diagnosis of URTI in children.

C-Reactive Protein ; metabolism ; Case-Control Studies ; Child ; Humans ; Leukocyte Count ; Mannose-Binding Protein-Associated Serine Proteases ; metabolism ; Respiratory Tract Infections ; blood

The aim of this study was to systemically analyze the proteins that adsorbed on the surface of hemodialysis membrane. The Fresenius F6 reused polysulfone dialyzers were selected as the research objects. The methodology we used encompassed the digestion of protein in rinsed solution and the separation of peptide mixture in virtue of RP-HPLC followed by ESI-MS/MS identification in orde to get their adsorption behavior, species and characteristics. The results illustrated that, after being rinsed by reverse osmosis (RO) water, 179 species of the protein adsorbed on the hemodialysis membrane, most of which were acidulous and middle or small weight protein molecules. The data from counting the numbers of peptides showed there were 5 species of high-abundant proteins (the contents being above 5% each), namely Ficolin-2 precursor, Complement C3 precursor (Fragment), Mannan-binding lectin serine protease 1 isoform 2 precursor, Complement-activating component of Ra-reactive factor precursor, and Mannan-binding lectin serine protease 1 isoform 3. These proteins are in close relationship with human immune system; moreover, they are of great significance to the clinical mechanism for cleaning reuse hemodialyzers and to the development of new hemodialysis materials.
Adsorption ; Complement C3 ; analysis ; Equipment Reuse ; Humans ; Lectins ; analysis ; Mannose-Binding Protein-Associated Serine Proteases ; analysis ; Membranes, Artificial ; Renal Dialysis ; instrumentation

OBJECTIVETo investigate the correlation among serum levels of manning-binding lectin (MBL), MBL-associated serine proteases-2 (MASP-2), complement Cand high-sensitive C reactive protein (HsCRP) in patients with rheumatoid arthritis (RA).

METHODSFasting venous blood were collected from 50 RA patients (25 in active stage and 25 in remission) and 40 healthy subjects for detecting serum levels of MBL, MASP-2, complement Cand HsCRP using enzyme-linked immunosorbent assay (ELISA) and immune turbidity assay.

RESULTSThe serum levels of MBL and MASP-2 were significantly lower and HsCRP level was significantly higher in patients with RA (in both acute stage and remission) than in the healthy control group (P<0.05), but complement Clevel was similar between the RA patients and control group. Bivariate Pearson correlation analysis showed that in RA patients, MBL was positively correlated with MASP-2 level (r=0.550, P=0.001) and negatively with HsCRP (r=-0.323, P=0.022) but not correlated with C(r=-0.022, P=0.882); MASP-2 was negatively correlated with HsCRP (r=0.453, P=0.453) and was not correlated with C(r=0.049, P=0.738). ROC curve analysis revealed the largest area under curve (AUC) of HsCRP (0.844, P=0.001) and smaller AUCs of MBL (0.025, P=0.001) and MASP-2 (0.266, P=0.001). HsCRP had a much higher sensitivity (84%) than MBL (10%) and MASP-2 (40%) in the diagnosis of RA.

CONCLUSIONIn RA patients, MBL and MASP-2 are negatively correlated with HsCRP level. Serum MBL and MASP-2 levels decrease with the progression of joint injury in RA patients, suggesting their involvement in the pathological process of RA; but due to their low sensitivity, they are not appropriate indicators for evaluating the disease activity of RA.

Arthritis, Rheumatoid ; blood ; C-Reactive Protein ; analysis ; Case-Control Studies ; Complement C3 ; analysis ; Enzyme-Linked Immunosorbent Assay ; Humans ; Mannose-Binding Lectin ; blood ; Mannose-Binding Protein-Associated Serine Proteases ; analysis