Mannose-binding lectin polymorphisms in patients with hepatitis C virus infection

Mesenchymal stem cells in fibrotic diseases-the two sides of the same coin

Fibrosis is caused by extensive deposition of extracellular matrix (ECM) components, which play a crucial role in injury repair. Fibrosis attributes to ~45% of all deaths worldwide. The molecular pathology of different fibrotic diseases varies, and a number of bioactive factors are involved in the pathogenic process. Mesenchymal stem cells (MSCs) are a type of multipotent stem cells that have promising therapeutic effects in the treatment of different diseases. Current updates of fibrotic pathogenesis reveal that residential MSCs may differentiate into myofibroblasts which lead to the fibrosis development. However, preclinical and clinical trials with autologous or allogeneic MSCs infusion demonstrate that MSCs can relieve the fibrotic diseases by modulating inflammation, regenerating damaged tissues, remodeling the ECMs, and modulating the death of stressed cells after implantation. A variety of animal models were developed to study the mechanisms behind different fibrotic tissues and test the preclinical efficacy of MSC therapy in these diseases. Furthermore, MSCs have been used for treating liver cirrhosis and pulmonary fibrosis patients in several clinical trials, leading to satisfactory clinical efficacy without severe adverse events. This review discusses the two opposite roles of residential MSCs and external MSCs in fibrotic diseases, and summarizes the current perspective of therapeutic mechanism of MSCs in fibrosis, through both laboratory study and clinical trials.

Complement Proteins as Soluble Pattern Recognition Receptors for Pathogenic Viruses

The complement system represents a crucial part of innate immunity. It contains a diverse range of soluble activators, membrane-bound receptors, and regulators. Its principal function is to eliminate pathogens via activation of three distinct pathways: classical, alternative, and lectin. In the case of viruses, the complement activation results in effector functions such as virion opsonisation by complement components, phagocytosis induction, virolysis by the membrane attack complex, and promotion of immune responses through anaphylatoxins and chemotactic factors. Recent studies have shown that the addition of individual complement components can neutralise viruses without requiring the activation of the complement cascade. While the complement-mediated effector functions can neutralise a diverse range of viruses, numerous viruses have evolved mechanisms to subvert complement recognition/activation by encoding several proteins that inhibit the complement system, contributing to viral survival and pathogenesis. This review focuses on these complement-dependent and -independent interactions of complement components (especially C1q, C4b-binding protein, properdin, factor H, Mannose-binding lectin, and Ficolins) with several viruses and their consequences.

Collectins: Innate Immune Pattern Recognition Molecules

Collectins are collagen-containing C-type (calcium-dependent) lectins which are important pathogen pattern recognising innate immune molecules. Their primary structure is characterised by an N-terminal, triple-helical collagenous region made up of Gly-X-Y repeats, an a-helical coiled-coil trimerising neck region, and a C-terminal C-type lectin or carbohydrate recognition domain (CRD). Further oligomerisation of this primary structure can give rise to more complex and multimeric structures that can be seen under electron microscope. Collectins can be found in serum as well as in a range of tissues at the mucosal surfaces. Mannanbinding lectin can activate the complement system while other members of the collectin family are extremely versatile in recognising a diverse range of pathogens via their CRDs and bring about effector functions designed at the clearance of invading pathogens. These mechanisms include opsonisation, enhancement of phagocytosis, triggering superoxidative burst and nitric oxide production. Collectins can also potentiate the adaptive immune response via antigen presenting cells such as macrophages and dendritic cells through modulation of cytokines and chemokines, thus they can act as a link between innate and adaptive immunity. This chapter describes the structure-function relationships of collectins, their diverse functions, and their interaction with viruses, bacteria, fungi and parasites.

Role of mannose binding lectin in response to candida antigen immunotherapy of warts

BACKGROUND

Warts is the commonest cutaneous manifestation of human papillomavirus (HPV) infection. Intralesional Candida antigen immunotherapy is used for wart treatment.

AIM

To identify the role of mannose binding lectin (MBL) in susceptibility to HPV infection and to explore the relationship between MBL and response to intralesional Candida antigen immunotherapy of wart.

PATIENTS AND METHODS

A case-control study was enrolled with 96 participants; 48 wart cases and 48 healthy controls. MBL serum level assay baseline and after six settings of intralesional candida antigen injection was done by ELISA technique. MBL2 gene exon 1 codon 54 polymorphism was detected by using restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR).

RESULTS

A statistically significant difference in MBL serum level between wart cases and controls was found. An association between MBL2 exon1 codon 54 polymorphism and susceptibility to HPV infection and development of warts was proved. Carriage of genotype AB was more frequent wart cases (95.8%) than in controls (20.8%). No statistical significance association could be found between the therapeutic response to Candida antigen immunotherapy in wart cases and MBL as regards its serum level and genotypes.

CONCLUSIONS

MBL play an important role in host defense against HPV infection.

The association of mannose binding lectin genotype and immune response to Chlamydia pneumoniae: The Strong Heart Study

Cardiovascular disease (CVD) is an important contributor to morbidity and mortality in American Indian communities. The Strong Heart Study (SHS) was initiated in response to the need for population based estimates of cardiovascular disease in American Indians. Previous studies within SHS have identified correlations between heart disease and deficiencies in mannose binding lectin (MBL), a motif recognition molecule of the innate immune system. MBL mediates the immune response to invading pathogens including Chlamydia pneumoniae (Cp), which has also been associated with the development and progression of CVD. However, a link between MBL2 genotype and Cp in contributing to heart disease has not been established. To address this, SHS collected baseline Cp antibody titers (IgA and IgG) and MBL2 genotypes for common functional variants from 553 individuals among twelve participating tribes. A single nucleotide polymorphism (SNP) in the promoter, designated X/Y, correlated significantly with increased Cp IgG titer levels, whereas another promoter SNP (H/L) did not significantly influence antibody levels to Cp. Two variants within exon 1 of MBL2, the A and B alleles, also displayed significant association with Cp antibody titers. Some MBL2 genotypes were absent from the population, suggesting linkage disequilibrium may be operating within the SHS cohort. Additional factors, such as increasing age and socioeconomic status, were also associated with increased Cp IgG antibody titers. This study demonstrates that MBL2 genotype associates with immune reactivity to C. pneumoniae in the SHS cohort. Thus, MBL2 may contribute to the progression of cardiovascular disease (CVD) among American Indians indirectly through pathogen interactions in addition to its previously defined roles.

HBV Viral Load and Liver Enzyme Levels May Be Associated with the Wild MBL2 AA Genotype

The present study investigated the frequencies of rs1800450 (MBL ^⁎B, G>A), rs1800451 (MBL ^⁎C, G>A), and rs5030737 (MBL ^⁎D, C>T) polymorphisms in exon 1 of the MBL2 gene among patients with chronic viral hepatitis. Blood samples from patients infected with hepatitis B virus (HBV; n = 65), hepatitis C virus (HCV; n = 92), and a noninfected control group (n = 300) were investigated. The presence of polymorphisms was detected using a real-time polymerase chain reaction to correlate with liver disease pathogenesis and fibrosis staging according to the Metavir classification. The genotypic and allelic frequencies showed no significant differences between the groups, but patients with active HBV and the wild AA genotype presented a positive correlation between increased transaminase and HBV DNA levels and the presence of mild to moderate fibrosis. Patients with HCV and the wild AA genotype presented mild inflammation and higher HCV RNA levels, although the same association was not observed for the fibrosis scores. The results suggest that the mutations in exon 1 of the MBL2 gene do not contribute directly to the clinical and laboratory features of HCV and HBV infections, but further studies should be performed to confirm whether the wild AA genotype has indirect effect on disease progression.

MBL2 Genetic Variants in HCV Infection Susceptibility, Spontaneous Viral Clearance and Pegylated Interferon Plus Ribavirin Treatment Response

Hepatitis C is disease that damages the liver, and it is caused by the hepatitis C virus (HCV). The pathology became chronic in about 80% of the cases due to virus persistence in the host organism. The standard of care consists of pegylated interferon plus ribavirin; however, the treatment response is very variable and different host/viral factors may concur in the disease outcome. The mannose-binding protein C (MBL) is a component of the innate immune system, able to recognize HCV and consecutively activating the immune response. MBL is encoded by MBL2 gene, and polymorphisms, two in the promoter region (H/L and X/Y) and three in exon 1 (at codon 52, 54 and 57), have been described as functionally influencing protein expression. In this work, 203 Italian HCV patients and 61 healthy controls were enrolled and genotyped for the five MBL2 polymorphisms mentioned above to investigate their role in HCV infection susceptibility, spontaneous viral clearance and treatment response. MBL2 polymorphisms were not associated with HCV infection susceptibility and with spontaneous viral clearance, while MBL2 O allele, O/O genotype, HYO haplotype and DP combined genotype (all correlated with low or deficient MBL expression) were associated with sustained virological response. Moreover, a meta-analysis to assess the role of MBL2 polymorphisms in HCV infection susceptibility was also performed: YA haplotype could be associated with protection towards HCV infection.

Association of MBL2 exon1 polymorphisms with high-risk human papillomavirus infection and cervical cancers: a meta-analysis

PURPOSE

High-risk human papillomavirus (HR-HPV) infection is the main known cause of cervical cancer. Mannose-binding lectin (MBL) is a recognition molecule that mediates phagocytosis and activates complement.

METHODS

We performed a meta-analysis to investigate the association of MBL-2 functional polymorphisms with HPV infection and cervical cancer (CC).

RESULTS

The meta-analyses indicated an association between the MBL2 exon 1 polymorphisms and susceptibility to HPV infection in the recessive model (OO vs. AA + AO, p = 0.042, 95 % CI 1.02-3.15), and O/O vs. A/A mode (P = 0.023, 95 % CI 1.10-3.40) in Caucasian. Meanwhile, there was a significant association between MBL2 exon 1 polymorphisms and cervical cancer risk in AO vs. AA model (p = 0.035, 95 % CI 1.03-2.26), and Allelic model (O vs. A, p = 0.022, 95 % CI 1.05-1.96) as compared to HR-HPV-infected patients with CC vs. healthy controls in Caucasian. In addition, no an association was observed between MBL2 -550 H/L and -221 X/Y polymorphisms and HPV infection among Caucasians, but we found an association between the MBL2 -550 H/L polymorphism and susceptibility to HR-HPV infection in recessive model (HH vs. LL + LH, p = 0.003, 95 % CI 1.18-2.23), HH vs. LL model (p = 0.021, 95 % CI 1.07-2.19), and allelic model(H vs. L, p = 0.042, 95 % CI 1.01-1.40) in Asians.

CONCLUSIONS

Collectively, we suggest that the MBL2 gene exon1 polymorphisms are associated with increased risk of high-risk HPV infection and cervical cancer development among Caucasians. Additionally, no significant association was found between the MBL2 -550 H/L or -221 X/Y polymorphisms and HPV infection in Caucasians, but there may be potential links in Asians.

Mannose-binding lectin in chronic hepatitis C in children

OBJECTIVE

To investigate effect of mannose-binding lectin (MBL) genetic polymorphisms and phenotype in chronic hepatitis C and its impact on response to antiviral therapy in children.

METHODS

Fifty four children with chronic hepatitis C, aged 2.5-18 years were enrolled. Forty-five children were treated with interferon-α (IFN-α) alone (n = 2) or IFN-α and ribavirin (n = 43). Twenty-one children who responded to antiviral therapy were defined as sustained responders to therapy (IFN-SR). Before therapy, MBL genotypes and serum MBL levels (by ELISA) were determined. MBL genotype distribution and levels were correlated to disease characteristics and response to therapy.

RESULTS

Children with chronic hepatitis C who did not respond to antiviral therapy (IFN-NR) presented more frequently MBL2 polymorphisms, although this did not reach significance (p = 0.08). MBL levels were significantly lower in children classified as IFN-NR when compared to children defined as IFN-SR (1.623 ng/ml vs. 3.699 ng/ml), (p = 0.04). Serum activity levels of ALT and AST were higher in children with A/O MBL genotype when compared to group with A/A genotype (p < 0.05).

CONCLUSIONS

Our findings suggest negative effect of MBL deficiency (defined by genotype and phenotype) on progression of chronic hepatitis C in children and response to antiviral therapy.

Mannose-binding lectin gene polymorphism and chronic hepatitis B infection in children

BACKGROUND/AIMS

Mannose-binding lectin (MBL) is a member of innate immune system that activates complement system through lectin pathway. MBL deficiency is associated with susceptibility to infectious diseases. In this study, the relation between MBL gene polymorphism and chronic hepatitis B infection in children is evaluated.

PATIENTS AND METHODS

The study included 67 children with chronic hepatitis B and 99 healthy controls. The hepatitis B patients were divided into immuntolerant, chronic inactive, and treatment groups according to their laboratory findings. MBL gene codon 52, 54, and 57 polymorphisms were studied with polymerase chain reaction in all patients and controls. The associations of MBL gene polymorphism with clinical, laboratory, and histopathologic findings were evaluated.

RESULTS

Homozygous codon 54 polymorphism of MBL was found significantly higher in chronic hepatitis B patients than controls. Rate of the polymorphism was similar in all groups and, responsive and nonresponsive patients in the treatment group.

CONCLUSIONS

The hepatitis B patients who are homozygous for codon 54 of MBL are prone to develop chronic infection. Longitudinal studies with larger groups are needed.

Role of mannose-binding lectin-2 polymorphism in the development of acute cellular rejection after transplantation for hepatitis C virus-induced liver disease

The development of liver and graft disease is suspected to be affected by genetic diversity. Mannose-binding lectin-2 (MBL-2) is an important immunomodulatory factor that is involved in complement activation. The aim of our study was to elucidate the role of MBL-2 genotypes after liver transplantation (LT) for hepatitis C virus (HCV)-induced liver disease regarding the incidence of acute cellular rejection (ACR), graft inflammation, fibrosis development, and antiviral treatment response.

METHODS

A group of 149 patients who underwent LT for HCV-induced liver disease were genotyped for MBL-2 (rs7096206; G/C) by TaqMan genotyping assay. We evaluated 518 post-LT protocol biopsies and at least 98 urgent liver biopsies regarding graft fibrosis stages, inflammation grades, and evidence for rejection within MBL-2 genotype groups.

RESULT

No association of MBL-2 polymorphisms was observed regarding inflammation, fibrosis, and antiviral treatment outcome. However, the C allele of the MBL-2 gene (P = 0.001) and gender compatibility (P = 0.012) were factors significantly associated with the incidence of ACR.

CONCLUSION

MBL-2 polymorphisms and gender are involved in the development of ACR after LT. CC genotype and gender match may be regarded as risk factors for ACR in HCV-positive graft recipients. Further studies are needed to confirm and verify this observation in non-HCV groups as well.

Serum mannan-binding lectin in egyptian patients with chronic hepatitis C: its relation to disease progression and response to treatment

BACKGROUND

Chronic hepatitis C virus (HCV) infection is a major worldwide public health problem. Egypt has the highest prevalence of adult HCV infection in the world, averaging 15%-25% in rural communities. Mannan-binding lectin (MBL) is a liver-derived pluripotent serum lectin that plays a role in the innate immune system of the host. It is an acute-phase protein that is involved in the activation of the classical complement pathway. MBL may play a defensive role in HCV infection.

OBJECTIVES

To investigate the relationship between MBL concentration and HCV infection in Egyptian patients suffering chronic hepatitis C.

PATIENTS AND METHODS

Serum samples obtained from 35 Egyptian hepatitis C patients and 30 normal controls were assayed for MBL. MBL concentrations were correlated to disease characteristics and treatment response.

RESULTS

Serum MBL was significantly higher in HCV patients than in controls, but no relationship was found between MBL concentration and disease progression in terms of hepatic fibrosis and inflammation. Responders to interferon (INF)-based therapy had significantly higher serum MBL than non-responders.

CONCLUSIONS

We found no association between serum MBL concentration and progression of HCV related liver disease. Responders to INF-based therapy had significantly higher serum MBL than non-responders.

The role of humoral innate immunity in hepatitis C virus infection

Infection with Hepatitis C Virus (HCV) causes chronic disease in approximately 80% of cases, resulting in chronic inflammation and cirrhosis. Current treatments are not completely effective, and a vaccine has yet to be developed. Spontaneous resolution of infection is associated with effective host adaptive immunity to HCV, including production of both HCV-specific T cells and neutralizing antibodies. However, the supporting role of soluble innate factors in protection against HCV is less well understood. The innate immune system provides an immediate line of defense against infections, triggering inflammation and playing a critical role in activating adaptive immunity. Innate immunity comprises both cellular and humoral components, the humoral arm consisting of pattern recognition molecules such as complement C1q, collectins and ficolins. These molecules activate the complement cascade, neutralize pathogens, and recruit antigen presenting cells. Here we review the current understanding of anti-viral components of the humoral innate immune system that play a similar role to antibodies, describing their role in immunity to HCV and their potential contribution to HCV pathogenesis.

Current status of novel antifibrotic therapies in patients with chronic liver disease

Fibrosis accumulation is a dynamic process resulting from a wound-healing response to acute or chronic liver injury of all causes. The cascade starts with hepatocyte necrosis and apoptosis, which instigate inflammatory signaling by chemokines and cytokines, recruitment of immune cell populations, and activation of fibrogenic cells, culminating in the deposition of extracellular matrix. These key elements, along with pathways of transcriptional and epigenetic regulation, represent fertile therapeutic targets. New therapies include drugs specifically designed as antifibrotics, as well as drugs already available with well-established safety profiles, whose mechanism of action may also be antifibrotic. At the same time, the development of noninvasive fibrogenic markers, and techniques (e.g. fibroscan), as well as combined scoring systems incorporating serum and clinical features will allow improved assessment of therapy response. In aggregate, the advances in the elucidation of the biology of fibrosis, combined with improved technologies for assessment will provide a comprehensive framework for design of antifibrotics and their analysis in well-designed clinical trials. These efforts may ultimately yield success in halting the progression of, or reversing, liver fibrosis.

Association of mannose-binding lectin-2 gene polymorphism with the development of hepatitis C-induced hepatocellular carcinoma

BACKGROUND

Development of end-stage liver and graft disease is suspected to be partially determined by the individual genetic background. Mannose-binding lectin (MBL) is an important immunomodulatory factor, which is supposed to be involved in complement activation and oncogenesis. Genetic polymorphisms of MBL-2 alter MBL functionality. The aim of our study was to determine the prevalence of MBL-2 polymorphism (rs7096206) in hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) based on histological analysis of explanted livers in patients undergoing liver transplantation (LT).

METHODS

One hundred and seventy-seven patients, who underwent LT for HCV-induced liver disease, were genotyped for MBL-2 by TaqMan genotyping assay. Sixty-two patients with histologically confirmed HCC were compared with 115 patients without HCC. MBL-2 genotypes were corelated with the growth patern, tumour size and pretransplant α-fetoprotein (AFP) level of HCC patients.

RESULTS

The prevalence of GG/GC genotypes was significantly higher among HCC patients compared with tumour-free explanted livers (P = 0.004; odds ratio 2.5; 1.3-4.8). GG/GC genotype group was significantly associated with the size of HCC (P = 0.022), higher pretransplant AFP level (P = 0.010) and bilobar tumour growth (P = 0.038). Furthermore, CC genotype was found to be significantly more frequent in AFP-negative HCCs (P = 0.002).

CONCLUSION

Mannose-binding lectin-2 polymorphism seems to be involved in the development of pretransplant HCV-induced HCC and should be further investigated as potential risk factor for HCV-associated carcinogenesis.

Fibrosis severity and mannan-binding lectin (MBL)/MBL-associated serine protease 1 (MASP-1) complex in HCV-infected patients

BACKGROUND AND STUDY AIMS

Mannan-binding lectin (MBL) is a collectin synthesised in the liver and secreted into the bloodstream. It binds micro-organisms via interactions with glycans on the target surface. Bound MBL subsequently activates MBL-associated serine protease proenzymes (MASPs). Several studies have investigated the possible role for MBL in hepatitis C virus (HCV) infection by examining MBL levels and polymorphisms in relation to disease progression and in response to treatment. The aim of this study was to investigate the relation of the activity of MBL and MBL/MASP-1 complex in sera of patients with mild and severe chronic HCV infection and outcome of HCV infection.

PATIENTS AND METHODS

Serum level of MBL and functional assays for MBL/MASP-1 complex activity were assayed in sera of 80 patients with chronic HCV infection. Patients were divided into two groups according to the results of the liver biopsy, group I (40 HCV patients had mild hepatic fibrosis, Ishak fibrosis stages 0-1) and group II (40 HCV patients had severe hepatic fibrosis, Ishak fibrosis stages 5-6), in addition to 20 control subjects as group III. The analysis of the MBL/MASP-1 complex activity at 0, 3 and 6 months was performed in all patients.

RESULTS

Serum levels of MBL and MBL/MASP-1 complex activity were higher in sera of patients with chronic HCV liver disease compared to those in control subjects. There was a correlation between the activity of the MBL/MASP-1 complex and the severity of fibrosis (P=0.003). MBL/MASP-1 complex activity was associated more significantly with severe fibrosis in comparison to MBL concentration.

CONCLUSION

MBL and MBL/MASP-1 complex activities play a key role in first-line host defence mechanism against certain infectious agents including HCV infection. However, it is also likely that the role of MBL and MBL/MASP-1 complex activity extends beyond this restricted infection-related view in that it appears to be a key regulator of inflammation.

The lectin pathway of complement activation contributes to protection from West Nile virus infection

The function of the lectin pathway of complement activation in vivo against West Nile virus (WNV) or many other pathogenic viruses has not been defined. Mice deficient in lectin pathway recognition molecules (mannose binding lectin-A (MBL-A) and mannose binding lectin-C (MBL-C)) or the effector enzyme mannan-binding lectin-associated serine protease-2 (MASP-2), were more vulnerable to WNV infection than wild type mice. Compared with studies of mice deficient in factors of the classical or alternative pathway, MBL-A(-/-) × MBL-C(-/-) or MASP-2(-/-) mice showed a less severe course of WNV infection. Indeed, a deficiency in lectin pathway activation did not significantly affect the kinetics of viral spread to the central nervous system (CNS) nor did it profoundly alter generation of adaptive B and T cell immune responses. We conclude that MBL-mediated recognition and lectin pathway activation have important yet subordinate functions in protecting against WNV infection and disease.

Mannose-binding lectin deficiency influences innate and antigen-presenting functions of blood myeloid dendritic cells

Mannose-binding lectin (MBL) is a serum lectin that plays a significant role in innate host defence. Individuals with mutations in exon 1 of the MBL2 gene have reduced MBL ligand binding and complement activation function and increased incidence of infection. We proposed that, during infection, MBL deficiency may impact on dendritic cell (DC) function. We analysed the blood myeloid DC (MDC) surface phenotype, inflammatory cytokine production and antigen-presenting capacity in MBL-deficient (MBL-D) individuals and MBL-sufficient (MBL-S) individuals using whole blood culture supplemented with zymosan (Zy) or MBL-opsonized zymosan (MBL-Zy) as a model of infection. Zy-stimulated MDCs from MBL-D individuals had significantly increased production of interleukin (IL)-6 and tumour necrosis factor (TNF)-α. Stimulation with MBL-Zy significantly decreased IL-6 production by MDCs from MBL-D, but had no effect on TNF-α production. MDCs from both MBL-S and MBL-D individuals up-regulated expression of the activation molecule CD83, and down-regulated expression of homing (CXCR4), adhesion (CD62L, CD49d) and costimulatory (CD40, CD86) molecules in response to Zy and MBL-Zy. MDC from both MBL-D and MBL-S individuals induced proliferation of allogeneic (allo) T cells following Zy or MBL-Zy stimulation; however, MBL-D individuals demonstrated a reduced capacity to induce effector allo-T cells. These data indicate that MBL deficiency is associated with unique functional characteristics of pathogen-stimulated blood MDCs manifested by increased production of IL-6, combined with a poor capacity to induce effector allo-T-cell responses. In MBL-D individuals, these functional features of blood MDCs may influence their ability to mount an immune response.

Relationship between oligomer and functional serum mannose-binding lectin in chronic renal failure

INTRODUCTION

Mannose-binding lectin (MBL) plays an important role in first-line host defence against pathogens via the lectin pathway. The binding affinity for ligands is greatly increased by oligomerization, although the basic triplet does not bind solid phase mannan and cannot activate complement. Besides, MBL is a positive acute-phase protein. In this study, we examined the relationship between oligomer and functional serum MBL in chronic renal failure patients who were either uraemic [Pre-haemodialysis (pre-HD) patients], or who were receiving maintenance haemodialysis treatment (HD patients).

MATERIALS AND METHODS

This study included a total of 20 Pre-HD patients, 130 HD patients and 28 healthy subjects. The oligomer and functional serum MBL levels were measured using enzyme-linked immunosorbent assays established previously.

RESULTS

The median serum functional MBL levels were significantly reduced in both Pre-HD and HD patients compared with healthy subjects (P<0·05 for both). Furthermore, the median functional MBL level in Pre-HD patients was significantly lower than that in HD patients (P<0·05). The median serum oligomer MBL levels in both Pre-HD and HD patients were significantly higher compared with healthy subjects (P<0·05 for both). Furthermore, the median oligomer MBL level in HD patients was significantly (P<0·05) higher than that in Pre-HD patients. The ratios of median serum functional MBL levels to oligomer MBL levels were significantly reduced in both Pre-HD and HD patients compared with healthy subjects (P<0·05 for both).

CONCLUSIONS

We found significant reductions in the ratios of serum functional MBL levels to oligomer MBL levels in HD and Pre-HD patients compared with healthy subjects.

Specific interaction of hepatitis C virus glycoproteins with mannan binding lectin inhibits virus entry

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.

Association of mannose-binding lectin gene polymorphisms with Kawasaki disease in the Japanese

OBJECTIVE

Kawasaki disease (KD) is a systemic vasculitis in childhood; its etiology is unknown. The possibility that KD is an infectious disease has been discussed and investigated for decades, in light of the implication that infections are involved in the pathogenesis of KD. Young children rely on their innate immune system for protection against virus and micro-organisms. Human mannose binding lectin (MBL) is a C-type serum lectin synthesized by the liver as an acute phase protein and it plays an important role in the innate immune system. Here, we investigate the relationship between the MBL gene polymorphisms and the occurrence of KD in the Japanese population.

METHOD

The frequencies of the genotypes, defined as mutations in codons 52, 54 and 57, and the functional promoter variants of the MBL were determined in 45 patients with KD.

RESULTS

The MBL codon-54 polymorphism frequency of heterozygote (GGC/GAC) and promoter variants were significantly higher in the KD group than that in the control group (P < 0.05). Neither group showed codon 52 nor 57 polymorphisms.

CONCLUSION

It is possible that mutations of the MBL gene might be related to the trigger of the pathogenesis of Kawasaki disease.

Association of hepatitis C virus infection and liver fibrosis severity with the variants alleles of MBL2 gene in a Brazilian population

Mannose binding lectin (MBL) is a molecule of the innate immunity, which activates the complement system and modulates inflammation. We investigated the association of the polymorphisms in the exon 1 and promoter region of the MBL gene (MBL2) with the susceptibility to hepatitis C virus (HCV) infection and the degree of liver fibrosis in Brazilian patients chronically infected with HCV. The study was performed in 232 healthy control subjects and 186 patients, 157 of whom underwent liver biopsy after histopathology analysis and classification of fibrosis according to Metavir score. Exon 1 was genotyped by melting temperature assay and the promoter region by Taqman real-time polymerase chain reacation. The frequency of genotypes related to low production of MBL was higher in patients with HCV than in controls (p(c) = 0.0001, odds ratio = 3.52; confidence interval = 1.86-6.71). In addition, the frequency of variant haplotype, HYO was higher in patients with the severe fibrosis stage F4 (10.7%) than in patients with the mild/moderate fibrosis stage F1/F2 (3.4%), when compared with the HYA haplotype (p(c) = 0.04, odds ratio = 5.25, confidence interval = 1.11-23.62). We conclude that MBL variant alleles expressing low levels of MBL are associated with the susceptibility to HCV infection and that the inheritance of HYO haplotype could be associated with fibrosis severity.

Structural polymorphism of the mannose-binding lectin 2 (MBL2 ) gene in HCV-infected patients with a serological marker for thyroid autoimmunity

We studied the association of the mannose-binding lectin-2 (MBL2) polymorphism with anti-thyroid antibodies (ATA) in hepatitis C virus (HCV)-infected Brazilian patients (n = 162) and 124 healthy volunteers screened for ATA. Our results showed that patients with ATA had higher frequency of genotype 00 than controls. MBL may play a role as disease modifier in HCV infection.

Mannose-binding lectin gene polymorphisms are not associated with susceptibility to hepatitis C virus infection in the Brazilian Amazon region

The present study compares the genotype frequencies between two population groups composed by 73 hepatitis C virus (HCV)-infected patients and 92 seronegative controls and investigates the role of allele variants as a possible factor in the susceptibility to HCV infection and the influence on disease progression. The identification of MBL*B and MBL*C alleles was performed by restriction fragment length polymorphism analysis of the 349-bp product using BanI and MboII restriction enzymes, respectively, and a polymerase chain reaction-sequence-specific polymorphism for discrimination of MBL*D. The analysis of allele and genotype frequencies between an HCV-infected group and seronegative controls did not indicate significant differences. The comparison of chronically infected subjects with and without liver cirrhosis was also not statistically significant. The odds ratio estimations were not significant, and the values obtained cannot suggest that the presence of allele variant MBL*B could have some influence in the risk of HCV infection progression to liver cirrhosis and that the presence of allele MBL*D could confer some protection against disease progression, but a larger sample size is necessary to confirm the present results.

Mannose-binding lectin in high-risk human papillomavirus infection

OBJECTIVE

Mannose-binding lectin (MBL) is a serum lectin that mediates phagocytosis and activates complement. We investigated the association of mbl-2 functional polymorphisms with human papillomavirus (HPV) infection, which is a primary etiologic factor for cervical cancer.

STUDY DESIGN

The frequencies of haplotypes and genotypes of mbl-2 exon1 and promoter region variants were analyzed in 150 patients with HPV and 277 control subjects with no HPV. Unconditional logistic regression analysis was performed to evaluate an association between specific mbl-2 alleles and susceptibility to HPV infection.

RESULTS

The frequency of high-producer mbl-2 genotypes was higher in patients with HPV than in control subjects with no HPV (P = .001). The genotype of the mbl-2 gene polymorphisms represented the least significant risk for the group with HPV.

CONCLUSION

Certain polymorphisms in the MBL promoter region are increased among cervical samples that demonstrate HPV infection. This finding suggests a potential link between MBL and high-risk HPV infection.

Mannose-binding lectin MBL2 gene polymorphisms and outcome of hepatitis C virus-infected patients

INTRODUCTION

Mannose-binding lectin (MBL) is involved in host's response to several infections including hepatitis B but little is known about MBL and hepatitis C virus (HCV) infection. The present study attempts to investigate whether MBL2 genotype and serum MBL levels affect the course of HCV infection.

RESULTS AND DISCUSSIONS

We investigated the variant alleles in MBL2 gene promoter and exon-1 regions in 80 Caucasian HCV-infected patients. Mutations in MBL2 were determined by polymerase chain reaction and restriction fragment length polymorphisms analysis. Serum MBL levels were measured by ELISA. Polymorphism homozygosity in exon-1 region was significantly related to lower serum MBL levels (p < 0.001), to liver inflammation (p = 0.034, OR = 11.7) and, in a lesser degree, to fibrosis. Polymorphisms in promoter sites -221nt and -550nt were not shown to be related with serum MBL levels or progress to liver inflammation and fibrosis. Serum MBL levels were adversely associated with progression to fibrosis (p = 0.037). Response to antiviral treatment was related to hepatitis C virus genotype (p < 0.001, OR = 10.9), but not to MBL2 genotype or serum MBL levels.

CONCLUSION

These findings suggest that polymorphisms in MBL2 gene exon-1 region are related to low serum MBL levels and progression of HCV infection to liver inflammation and fibrosis.

Mannan-binding lectin MBL2 gene polymorphism in chronic hepatitis C: association with the severity of liver fibrosis and response to interferon therapy

Hepatitis C virus (HCV) is a major cause of hepatic disease and of liver transplantation worldwide. Mannan-binding lectin (MBL), encoded by the MBL2 gene, can have an important role as an opsonin and complement activating molecule in HCV persistence and liver injury. We assessed the MBL2 polymorphism in 102 Euro-Brazilian patients with moderate and severe chronic hepatitis C, paired for gender and age with 102 HCV seronegative healthy individuals. Six common single nucleotide polymorphisms in the MBL2 gene, three in the promoter (H/L, X/Y and P/Q) and three in exon 1 (A, the wild-type, and B, C or D also known as O) were evaluated using real-time polymerase chain reaction with fluorescent hybridization probes. The concentration of MBL in plasma was measured by enzyme-linked immunosorbent assay. The frequency of the YA/YO genotype was significantly higher in the HCV patients compared with the controls (P = 0.022). On the other hand, the genotypes associated with low levels of MBL (XA/XA, XA/YO and YO/YO) were decreased significantly in the patients with severe fibrosis (stage F4), when compared with the patients with moderate fibrosis (stage F2) (P = 0.04) and to the control group (P = 0.011). Furthermore, MBL2 genotypes containing X or O mutations were found to be associated with non-responsiveness to pginterferon and ribavirin treatment (P = 0.023). MBL2 polymorphisms may therefore be associated not only with the development of chronic hepatitis C, but also with its clinical evolution and response to treatment.

The role of the mannose-binding lectin in innate immunity

The innate immune system, which includes mannose-binding lectin (MBL), recognizes a broad range of molecular patterns on a broad range of infectious agents and is able to distinguish them from self. MBL is a liver-derived serum protein and is secreted into the serum, where it can activate an immune response before the induction of antigen-specific immunity. Circumstantial evidence in human populations suggests that low serum levels of MBL predispose to infection. To analyze the role of MBL in vivo, we created MBL-null mice and challenged these mice with infection under various conditions. Our results suggest that MBL plays an important role as a first-line host defense against certain infectious agents. In addition, it is likely that MBL is a key regulator of inflammation beyond expected roles in the infection.

Association of polymorphisms in the first exon of mannose binding lectin gene (MBL2) in Brazilian patients with HCV infection

In our study we investigated the role of the polymorphisms in the first exon of MBL2 gene in the susceptibility to HCV infection and disease progression in a Northeastern Brazilian population. One hundred and eleven patients seen at the Gastroenterology Service of the Oswaldo Cruz Hospital of the University of Pernambuco were included in this study. A total of 165 unexposed, uninfected individuals matched for place of origin were employed as healthy controls. MBL2 genotyping was performed by using a melting temperature assay. The 0 allele was significantly more frequent in the HCV positive group than the healthy controls (34% vs. 20%, p<0.01, respectively) and was associated to an increased risk of HCV-1 infection (O.R.=2.1; C.I. 1.41-3.19). Also genotypes frequencies were significantly different in HCV positive subjects when compared to healthy controls with the 00 and A0 genotypes being significantly overrepresented in HCV infected subject (15% and 37%, respectively) as compared to healthy subjects (6% and 27%, respectively, p<0.01 ) Allele and genotypes frequencies were also evaluated in HCV infected subjects according to their response to pegylated-INFalpha/riboviron therapy. There was a trend for HCV positive responders vs. non-responders to be 0 allele positive and a similar trend was observed for the MBL2 A0 and 00 genotypes, but neither of these reached statistical significance. Our findings indicate that MBL might represent an important antiviral molecule having a protective role in the first stages of HCV infection, as shown by the increased frequency of wild-type alleles in control population as compared to the infected group.

Severe fibrosis in hepatitis C virus-infected patients is associated with increased activity of the mannan-binding lectin (MBL)/MBL-associated serine protease 1 (MASP-1) complex

Mannan-binding lectin (MBL) binds microorganisms via interactions with glycans on the target surface. Bound MBL subsequently activates MBL-associated serine protease proenzymes (MASPs). A role for MBL in hepatitis C virus (HCV) infection had been indicated by previous studies examining MBL levels and polymorphisms in relation to disease progression and response to treatment. We undertook this study to investigate a possible relationship between disease progression and functional MBL/MASP-1 complex activity. A functional assay for MBL/MASP-1 complex activity was employed to examine serum samples from patients with chronic HCV infection, non-HCV liver disease and healthy controls. Intrapatient consistency of MBL/MASP-1 complex activity levels was assessed in sequential samples from a subgroup of patients. Median values of MBL/MASP-1 complex activity were higher in sera from patients with liver disease compared with healthy controls. MBL/MASP-1 complex activity levels correlate with severity of fibrosis after adjusting for confounding factors (P = 0.003). MBL/MASP-1 complex activity was associated more significantly with fibrosis than was MBL concentration. The potential role of MBL/MASP-1 complex activity in disease progression is worthy of further study to investigate possible mechanistic links.

Lack of association between mannose-binding lectin gene polymorphisms and juvenile idiopathic arthritis in a Han population from the Hubei province of China

Many studies have reported that polymorphisms of the mannose-binding lectin (MBL) gene are associated with autoimmune disease. Here, we investigate the relationship between MBL gene polymorphisms and susceptibility to juvenile idiopathic arthritis (JIA) in a Han-nationality population from the Hubei province of China. PCR-restriction fragment length polymorphism was used to investigate polymorphisms of codons 54 and 57 in exon 1 of the MBL gene in 93 patients with JIA and 48 control children. Neither group showed codon 57 polymorphisms. There was no significant difference in the genotypic frequencies of codon 54 between patients with JIA and healthy controls (wild type, 71.0% versus 75.0%, respectively; heterozygous type, 25.8% versus 25.0%, respectively; and homozygous type, 3.2% versus 0.0%, respectively). In addition, no association was found between the subgroups of patients with JIA and control individuals. Our results provide no evidence for a relationship between MBL gene mutation and susceptibility to JIA.

Lack of association between genetic variants in the mannose-binding lectin 2 (MBL2) gene and HPV infection

Genetic variants in the immunomodulatory gene mannose-binding lectin 2 (MBL2), were associated with risk, severity, and frequency of viral infections. In a case-control setting, we investigated the association of MBL2 functional polymorphisms with Human Papillomas Virus (HPV) infection. No differences between cases (HPV(+)) and controls (HPV(-)) were found in the distribution of each single genotypes or allele. Haplotype analysis did not show any difference between HPV+ and HPV(-) groups.

Mannan binding lectin and viral hepatitis

Mannan binding lectin (MBL) is a pattern recognition molecule of the innate immune system that binds to sugars on the surface of invading micro-organisms. Target binding, complement activation and other functions of MBL are dependent on the presence of multiple carbohydrate recognition domains. Several polymorphisms in the promoter and structural regions of MBL2 adversely affect the plasma concentration and oligomeric state of MBL. The possession of mutant alleles has been linked to disease outcome for a variety of bacterial and viral infections. Viral hepatitis is caused by unrelated viruses referred to as hepatitis virus A-E. The disease usually has both acute and chronic phases, the latter leading to cirrhosis and hepatocellular carcinoma. Hepatitis viruses B and C (HBV and HCV, respectively) are a significant cause of morbidity worldwide. HBV encodes envelope glycoproteins termed large, middle, and small that may exist in glycosylated or unglycosylated forms on the virion. An interaction between HBV glycoproteins and MBL has been demonstrated in vitro. Significant associations between MBL levels, determined by MBL2 haplotypes, and HBV persistence and disease progression have been described. HCV encodes two highly glycosylated envelope proteins, E1 and E2, which are potential targets for interaction with MBL. Mutant MBL2 haplotypes have been linked to disease progression and response to therapy in HCV infection. Here we summarise the effect of MBL2 polymorphisms on MBL function and how this may relate to disease outcome in HBV and HCV infection.

Mannose-binding lectin and maladies of the bowel and liver

Mannose-binding lectin (MBL) is a pattern-recognition molecule that binds to characteristic carbohydrate motifs present on the surface of many different pathogens. MBL binding stimulates the immune system via the lectin pathway of complement activation. In certain clinical situations, often characterized by pre-existing immune compromise, MBL deficiency increases the risk of infectious and other disease-specific complications. Many of the key pathogenic processes inherent to common gastroenterological diseases, such as infection, immunological damage, and carcinogenesis, have been linked to MBL. This editorial reviews the biology of MBL, outlines key disease associations to document the breadth of influence of MBL, and finally, highlights the relevance of MBL to both gastroenterological health and disease.

Mannose-Binding Lectin: Clinical Implications for Infection, Transplantation, and Autoimmunity

Mannose-binding lectin (MBL) is a recognition molecule of the lectin pathway of complement and a key component of innate immunity. MBL variant alleles have been described in the coding region of the MBL gene, which are associated with low MBL serum concentration and impaired MBL structure and function. Both high and low serum levels of functional MBL have been associated with a variety of diseases and disease complications. Functioning as double-edged sword, low MBL serum levels have been shown to enhance the risk for infections. On the other hand, high MBL serum levels and high MBL activity have been associated with inflammatory diseases, transplant rejection, and diabetic nephropathy. Underscoring the Jekyll-and-Hyde character of MBL, both high and low serum MBL levels are associated with several aspects of autoimmune diseases. This review provides a general outline of the genetic and molecular characteristics of MBL and discusses MBL-disease association and its consequence in infection, transplantation, and autoimmunity.

Autoimmune pancreatitis and complement activation system

OBJECTIVES

Autoimmune pancreatitis is characterized by increased serum level of IgG4, but its pathogenesis has not been fully elucidated. Because this disease is occasionally associated with decreased levels of complements, we sought to clarify which complement activation system was operating in its active state.

METHODS

We measured serum levels of complements, mannose-binding lectin, and circulating immune complex in patients with autoimmune pancreatitis, patients with chronic pancreatitis, and healthy controls.

RESULTS

We found high serum circulating immune complex values, which decreased significantly after corticosteroid therapy. In patients with autoimmune pancreatitis, elevated levels of circulating immune complex, as determined by C1q assay, were significantly associated with increased serum levels of IgG1 and decreased levels of C4, as well as with a tendency toward decreased levels of C3. There were no significant differences in the serum levels of mannose-binding lectin or in the frequency of a mutant allele of mannose-binding lectin between patients with autoimmune pancreatitis and those with chronic calcifying pancreatitis. Furthermore, corticosteroid therapy had no effect on the level of mannose-binding lectin.

CONCLUSIONS

Autoimmune pancreatitis exhibits a high serum circulating immune complex values in its active state, which links to a complement activation system with a classic pathway rather than the mannose-binding lectin pathway or alternative pathways.

Association of HYPA haplotype in the mannose-binding lectin gene-2 with Behçet's disease

Behcet's disease (BD) is a multisystemic, recurrent inflammatory disease caused by the combinations of multiple genetic and environmental factors. Moreover, the MBL2 gene single-nucleotide polymorphisms and haplotypes are known to increase the susceptibility to inflammatory disease and to alter the serum levels of mannose-binding lectin (MBL. We postulated that the haplotypes of the MBL2 gene influence therapeutic response in BD, thus affecting the clinical symptoms in 282 BD patients. The promoter region, MBL2-550*C/*C (L/L) homozygote was found to have a lower frequency in BD patients than that in controls. No difference was observed in the allele frequencies of G-221C (Y/X), C+4T (P/Q) or Gly54Asp (A/B) of the MBL2 gene in BD patients and in controls. The HYPA haplotype contributed to BD occurrence, whereas the LYPA haplotype was negatively associated with BD. BD patients with several symptoms and with an earlier disease-onset age had a higher HYPA haplotype frequency. BD patients showing poor response (S) to therapy had a higher HYPA frequency than those showing good response (M). It seems that possessing HYPA increases the risk of BD and that the MBL2 HYPA haplotype plays a role in MBL levels and increases the susceptibility to BD.

Novel MASP2 variants detected among North African and Sub-Saharan individuals

The lectin pathway of the complement system is activated when mannan-binding lectin (MBL) in complex with MBL-associated serine protease 2 (MASP-2) binds to carbohydrate structures on microorganisms. Structural gene mutations and promoter polymorphisms in the MBL2 gene responsible for low-MBL serum levels are present in all human populations and associate with increased risk of infection. Recently, investigations on Danes revealed the existence of a mutation on the MASP2 gene, which introduces an amino acid substitution in the CUB1 domain (Asp105Gly; numbering refers to the mature protein), and is associated with reduction in the level of MASP-2 in serum. Here, we present the results of a sequence-based typing analysis of the MBL2 and MASP2 gene polymorphisms in a group of 65 Africans (50 North Africans and 15 Sub-Saharan) and of 104 Spaniards. The analysis identified three novel exon 3 MASP2 variants introducing amino acid substitutions at positions 84 (Arg-->Gln), 103 (Arg-->Cys) and 111 (Pro-->Leu) in the CUB1 domain. None of these variants were identified in Spaniards. The Arg84Gln was detected in four of the 15 Sub-Saharans. The Arg103Cys and Pro111Leu variants were detected only among North Africans (two and four individuals, respectively). The Asp105Gly variant was similarly represented among Spaniards and North Africans (three and two individuals, respectively), which appears to be a lower frequency than that reported for Danes (5.5%). As reported for MBL2, the marked geographic distribution of the new MASP2 variants may represent an evolutionary adaptation to different environments.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Anti-mannose binding lectin antibodies in sera of Japanese patients with systemic lupus erythematosus

Mannose-binding lectin (MBL) is a key element in innate immunity with functions and structure similar to that of complement C1q. It has been reported that MBL deficiency is associated with occurrence of systemic lupus erythematosus (SLE). We hypothesized that anti-MBL antibodies, if present, would affect the occurrence or disease course of SLE, by reduction of serum MBL levels, interference of MBL functions, or binding to MBL deposited on various tissues. To address this hypothesis, we measured the concentration of anti-MBL antibodies in sera of 111 Japanese SLE patients and 113 healthy volunteers by enzyme immunoassay. The titres of anti-MBL antibodies in SLE patients were significantly higher than those in healthy controls. When the mean + 2 standard deviations of controls was set as the cut off point, individuals with titres of anti-MBL antibodies above this level were significantly more frequent in SLE patients (9 patients) than in controls (2 persons). One SLE patient had an extremely high titre of this antibody. No associations of titres of anti-MBL antibodies and (i) genotypes of MBL gene, (ii) concentrations of serum MBL, or (iii) disease characteristics of SLE, were apparent. Thus, we have confirmed that anti-MBL antibodies are indeed present in sera of some patients with SLE, but the significance of these autoantibodies in the pathogenesis of SLE remains unclear.

Impact of Mannose-Binding Lectin on Susceptibility to Infectious Diseases

When the adaptive immune response is either immature or compromised, the innate immune system constitutes the principle defense against infection. Mannose-binding lectin (MBL) is a C-type serum lectin that plays a central role in the innate immune response. MBL binds microbial surface carbohydrates and mediates opsonophagocytosis directly and by activation of the lectin complement pathway. A wide variety of clinical isolates of bacteria, fungi, viruses, and parasites are bound by MBL. Three polymorphisms in the structural gene MBL2) and 2 promoter gene polymorphisms are commonly found that result in production of low serum levels of MBL. Clinical studies have shown that MBL insufficiency is associated with bacterial infection in patients with neutropenia and meningococcal sepsis. Low MBL levels appear to predispose persons to HIV infection. Numerous other potential infectious disease associations have been described. Therapy to supplement low MBL levels is being explored using either plasma-derived or recombinant material.

Mannose binding lectin gene polymorphism in patients with type I diabetes

Our purpose was to investigate a possible relationship between occurrence of type I diabetes and polymorphism of the mannose binding lectin gene. Polymorphism of codon 54 of the mannose binding lectin (MBL) gene, whose presence of the minority allele leads to significant reduction of serum MBL concentration, was investigated in 128 Japanese patients with type I diabetes and 78 healthy volunteers by restriction fragment length polymorphism method. Frequencies of the minority allele were compared between the patient group and the control group. Frequency of the minority allele was 24.2% in the patient group and 19.9% in the control group. The probability of being heterozygous or homozygous for the minority allele was 41.4% in the patient group and 33.3% in the control group. Patients with DRB1*0405-DQB1*0401 and/or DRB1*0901-DQB1*0303 haplotypes, the two major type I diabetes-prone human leukocyte antigen haplotypes, showed a slightly higher probability of being heterozygous or homozygous for allele B of the MBL gene. Possession of the minority allele of the MBL gene may be a minor risk factor for having type I diabetes.

Mannan-binding lectin and hepatitis C infection

Japanese patients with chronic hepatitis C infection unresponsive to treatment with interferon possessed genotypes disproportionately conferring low mannan-binding lectin (MBL) concentrations. Our aims were to confirm or refute this finding in European patients at the MBL protein level, and to investigate whether a low circulating concentration of MBL might influence susceptibility to, or disease progression from, hepatitis C viral infection. Serum samples obtained from 180 hepatitis C patients and 566 blood donors were assayed for MBL. MBL concentrations were related to disease characteristics retrieved from patients' records. MBL concentrations were higher in hepatitis C patients (median 2.5 microg/ml versus 1.3; P < 0.0001) and the proportion of patients with very low (MBL-deficient) concentrations was similar to that of the healthy controls. There were no significant associations between patients with low serum MBL and the disease features studied, including response to antiviral therapy. Therefore, low circulating MBL does not increase susceptibility to hepatitis C infection, and MBL concentration does not have a major influence on the course of the disease or the response to antiviral therapy. MBL replacement therapy would therefore not be indicated for chronic hepatitis C patients who failed to respond fully to treatment with interferon and ribavirin.

Genetic polymorphisms and the progression of liver fibrosis: a critical appraisal

Liver fibrosis is a highly dynamic process in which multiple genes interact with environmental factors. Recent human epidemiologic studies have identified possible polymorphisms in a number of candidate genes that influence the progression of liver fibrosis. These genetic factors could explain the broad spectrum of responses to the same etiologic agent found in patients with chronic liver diseases. Polymorphisms in genes encoding immunoregulatory proteins, proinflammatory cytokines, and fibrogenic factors may influence disease progression in patients with alcohol-induced liver disease, primary biliary cirrhosis, or chronic hepatitis C. However, some of the studies have yielded contradictory results. For example, conflicting results have been obtained in studies assessing the role of mutations in the hemochromatosis gene on fibrosis progression in patients with chronic hepatitis C. Large-scale, well-designed studies are required to clarify the actual role of this factor and other genetic variants in liver fibrosis.