Mannose binding lectin (MBL) gene mutation is not a risk factor for systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in Japanese

Effect of mannose-binding lectin gene polymorphisms on the risk of rheumatoid arthritis: Evidence from a meta-analysis

BACKGROUND

The effect of mannose-binding lectin (MBL) gene polymorphisms on susceptibility of rheumatoid arthritis (RA) were evaluated in ethnically different populations, whereas the results were always inconsistent.

MATERIALS AND METHODS

Fourteen articles involving 36 datasets were recruited to evaluate the association between MBL gene polymorphisms and rheumatoid arthritis in a meta-analysis. The random or fixed effect models were used to evaluate the pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs).

RESULTS

Stratified analysis by ethnicities was conducted and the result revealed that rs1800450 (T vs C, OR = 1.32, 95% CI: 1.04-1.67, P < .05) and MBL-A/O (T vs C, OR = 1.20, 95% CI: 1.08-1.34, P < .001) were strongly associated with RA in Brazilian populations. In addition, the significant relationship between rs11003125 (T vs C, OR = 1.16, 95% CI: 1.06-1.26, P < .05) with RA were also observed in East Asian populations. Meanwhile, the inverse associations between rs5030737 with RA in East Asians and rs1800450 with RA in Indians were acquired. However, no association between any MBL polymorphism with RA susceptibility was confirmed in Caucasians.

CONCLUSIONS

The structural polymorphisms in exon 1 of MBL gene may significantly contribute to susceptibility and development of RA in Brazilian and Indian populations, whereas the functional polymorphisms in the promoter region were more likely to associate with RA in East Asians.

Primary Immunodeficiencies in India: Molecular Diagnosis and the Role of Next-Generation Sequencing

Primary immunodeficiency diseases (PIDs) are a group of clinically and genetically heterogeneous disorders showing ethnic and geographic diversities. Next-generation sequencing (NGS) is a comprehensive tool to diagnose PID. Although PID is common in India, data on the genetic spectrum of PIDs are limited due to financial restrictions. The study aims to characterize the clinical and genetic spectrum of PID patients in India and highlight the importance of a cost-effective targeted gene panel sequencing approach for PID in a resource-limited setting. The study includes 229 patients with clinical and laboratory features suggestive of PIDs. Mutation analysis was done by Sanger sequencing and NGS targeting a customized panel of genes. Pathogenic variants were identified in 97 patients involving 42 different genes with BTK and IL12RB1 being the most common mutated genes. Autosomal recessive and X-linked recessive inheritance were seen in 51.6% and 23.7% of patients. Mendelian susceptibility to mycobacterial diseases (MSMD) and IL12RB1 mutations was more common in our population compared to the Western world and the Middle East. Two patients with hypomorphic RAG1 mutations and one female with skewed CYBB mutation were also identified. Another 40 patients had variants classified as variants of uncertain significance (VUS). The study shows that targeted NGS is an effective diagnostic strategy for PIDs in countries with limited diagnostic resources. Molecular diagnosis of PID helps in genetic counseling and to make therapeutic decisions including the need for a stem cell transplantation.

Association of MBL2 gene polymorphisms and systemic lupus erythematosus susceptibility: A meta-analysis

OBJECTIVES

Mannose binding lectin (MBL) gene single nucleotide polymorphisms have been associated with systemic lupus erythematosus (SLE) risk with inconsistent results. This study aimed to explore whether MBL2 A\B, A\C, A\D, A\O, L\H and Y\X polymorphisms affected SLE susceptibility.

METHODS

A meta-analysis was performed on 20 studies, containing allelic contrast, additive, dominant and recessive models. Odds ratio (OR) was calculated to reflect the effect of association.

RESULTS

A total of 64 pooled comparisons were conducted, including 7194 SLE patients and 7401 healthy controls. The meta-analysis inducted a significant association between allele B and SLE (OR = 0.766, 95% CI = 0.681-0.862, P < .001). The genotype BB in the additive model and AB + BB in the recessive model both reduced the risk of SLE (OR = 0.611, 95% CI = 0.422-0.882, P = .009; OR = 0.806, 95% CI = 0.688-0.944, P = .008). Regarding A\O polymorphisms, results revealed statistical differences in allelic contrast, additive model and recessive models (OR = 0.826, 95% CI = 0.732-0.931, P = .002; OR = 0.737, 95% CI = 0.557-0.977, P = .034 and OR = 0.793, 95% CI = 0.683-0.921, P = .002, respectively). As for L\H, meta-analysis revealed that allele H and genotype HH both decreased SLE susceptibility in allelic contrast and dominant models (OR = 1.463, 95% CI = 1.097-2.007, P = .018; OR = 1.383, 95% CI = 1.124-1.701, P = .002). Stratification by ethnicity indicated that allele H related to SLE in European populations (OR = 0.736, 95% CI = 0.617-0.879, P = .001), and the recessive model correlated with SLE in Asians (OR = 0.808, 95% CI = 0.667-0.979, P = .03).

CONCLUSION

The present study suggests that A\B and A\O polymorphisms were associated with SLE susceptibility, and the allele H may be a protective factor in SLE.

Immunodeficiency in the lupus clinic

Systemic lupus erythematous (SLE) and immunodeficiency are linked in various ways. For example, rare genetic complement deficiencies can pre-dispose to developing SLE, whilst some treatments for SLE can cause secondary immunodeficiencies. Various case reports describe SLE patients who have concomitant or later develop antibody deficiency, possibly related to immunosuppressive treatment, or possibly related to the lupus itself. Other components of the immune system, innate and adaptive may also be affected. Immunosuppressive treatment may also cause infections in the absence of defects on routine immunological testing. It is important for the clinician to be aware of the associations between SLE and immunodeficiency to ensure optimal investigation and management. This review focuses on aspects of humoral and cellular immunity, and their association with SLE.

Mannose-binding lectin polymorphisms and rheumatoid arthritis: A short review and meta-analysis

Mannose-binding lectin (MBL) is a pattern recognition receptor of the lectin pathway of complement system. MBL binds to carbohydrates on microorganism's surfaces leading to complement activation, opsonization and phagocytosis. Polymorphisms in the MBL gene (MBL2) are associated with variations on MBL serum levels and with the susceptibility to various infectious and autoimmune diseases. The involvement of the lectin pathway in rheumatoid arthritis (RA) has been demonstrated by several studies and although MBL has been considered to have a dual role in the pathogenesis of the disease, the association between MBL and RA remains inconclusive. In an attempt to clarify this relationship, we developed this short review summarizing accumulated evidences in regard to MBL and RA and a meta-analysis to evaluate the influence of MBL2 polymorphisms on the susceptibility to RA. Among a total of 217 articles that were identified following a predefined search strategy on PubMed, Scopus, Scielo, EMBASE and Cochrane databases, only 13 met all inclusion criteria and were included in the meta-analysis. Data assessment was conducted by three independent investigators and presented in odds ratio (OR) and 95% confidence intervals (CIs) using forest plot charts. Both heterogeneity and publication bias were analyzed. The results of the meta-analysis evidenced that MBL2 low producing OO and XX genotypes do not confer higher risk to RA, even when data were analyzed according to cohort's ethnicity. Further studies are needed in order to clarify the importance of other genes of the lectin pathway in the pathogenesis of RA.

Meta-analysis of functional MBL polymorphisms. Associations with rheumatoid arthritis and primary Sjögren's syndrome

OBJECTIVE

The aim of this study was to determine whether functional mannose-binding lectin gene (MBL) polymorphisms are associated with the susceptibility to rheumatoid arthritis (RA) or primary Sjögren's syndrome (pSS).

METHODS

A meta-analysis was conducted to investigate the potential association of RA or pSS with MBL polymorphisms, including the codon 54 (allele B), codon 57 (allele C), and codon 52 (allele D) variants of exon 1, and the - 550 (allele L) and - 221 (allele X) promoter variants.

RESULTS

A total of 12 comparative studies, including eight RA (1623 patients and 1671 controls) and four pSS (280 patients and 516 controls) studies, were included in the meta-analysis. The meta-analysis revealed no association between the MBL B allele and RA in the overall study population (odds ratio [OR] 0.991, 95 % confidence interval [CI] 0.726-1.355, p = 0.957). However, the meta-analysis showed significant associations between the MBL D, H, and X alleles and RA in the overall population (OR 1.708, 95 % CI 1.077-2.707, p = 0.023; OR 1.936, 95 % CI 1.218-3.078, p = 0.005; OR 1.582, 95 % CI 1.216-2.057, p = 0.001, respectively). An association was found between the MBL B allele and pSS in the overall study population (OR 0.691, 95 % CI 0.541-0.917, p = 0.010). Stratification by ethnicity indicated a trend toward an association between the B allele and pSS in European populations, but no association in Asian populations (OR 0.689, 95 % CI 0.465-1.021, p = 0.063; OR 0.896, 95 % CI 0.311-2.562, p = 0.838, respectively).

CONCLUSION

This meta-analysis demonstrated an association between the MBL D, L, and X alleles and the risk of RA. It also demonstrated an association between the MBL B allele and the susceptibility to pSS, suggesting a protective role of the MBL B allele against the development of pSS.

Association of MIF-173G/C and MBL2 codon 54 gene polymorphisms with rheumatoid arthritis: a meta-analysis

The aim of this study was to evaluate the association between macrophage migration inhibitory factor (MIF) -173G/C (rs755622), mannose-binding lectin (MBL2) exon 1 codon 54 (rs1800450) gene polymorphisms and rheumatoid arthritis (RA) susceptibility in ethnically different populations. A meta-analysis was conducted (allelic contrast, the additive model, the dominant model and the recessive model) on the MIF-173G/C polymorphism across five studies (four European and one Asian studies), and the MBL2 codon 54 polymorphism with five studies (four Asian and one European studies), respectively. Meta-analysis indicated an association between the MIF-173G/C in all study subjects in allelic contrast (OR=1.19, 95%CI: 1.05-1.35, P=0.001), the additive model (OR=1.68, 95CI: 1.13-2.49, P=0.001), the dominant model (OR=1.17, 95CI: 1.01-1.35, P=0.003), the recessive model (OR=1.63, 95CI: 1.10-2.42, P=0.001). While stratified by ethnicity with European populations, an association was found in allelic contrast (OR=1.20, 95CI: 1.04-1.38, P=0.002), the additive model (OR=1.85, 95CI: 1.19-2.88, P=0.001), the dominant model (OR=1.20, 95CI: 1.02-1.41, P=0.003). With respect to MBL2 codon 54 polymorphism and RA, no association was found in all study subjects in all comparisons, but there was an association while stratified by ethnicity with Asian populations in the dominant model (OR=1.50, 95CI: 1.01-2.23, P=0.007). In conclusion, the present study suggests that the MIF-173G/C polymorphism is associated with RA susceptibility, but the MBL2 codon 54 polymorphism is not associated with RA.

Mannose binding lectin and macrophage migration inhibitory factor gene polymorphisms in Turkish children with cardiomyopathy: no association with MBL2 codon 54 A/B genotype, but an association between MIF -173 CC genotype

Myocardial inflammation is one of the commonest mechanisms in cardiomyopathy (CMP). Mannose binding lectin (MBL) is a key molecule in innate immunity, while macrophage migration inhibitory factor (MIF) is a constitutive element of the host defenses. We investigated the possible association between polymorphisms of MBL2 and MIF genes and CMP in Turkish children. Twenty-children with CMP and 30 healthy controls were analyzed for codon 54 A/B polymorphism in MBL, and -173 G/C polymorphism in MIF genes by using PCR-RFLP methods. No significant difference was found between genotypes and alleles of MBL2 gene codon 54 A/B polymorphism in patients and controls (p>0.05). However, serum uric acid levels was found higher in dilated CMP patients with AA genotype. Frequency of MIF -173 CC genotype was significantly higher in patients (p<0.05), and sodium levels were higher in patients with MIF -173 CC genotype. This study is the first to investigate the MBL and MIF gene polymorphisms in Turkish children with CMP. We conclude that CC genotype of MIF (-173) polymorphism may be a risk factor for CMP patients. However, further studies with larger samples are needed to address the exact role of this polymorphism in CMP.

Serum concentration of complement components of the lectin pathway in maintenance hemodialysis patients, and relatively higher levels of L-Ficolin and MASP-2 in Mannose-binding lectin deficiency

Mannose-binding lectin (MBL), L-ficolin and MBL associated serine protease-2 (MASP-2) are molecules involved in initiation of the lectin pathway (LP) in the complement system. Although MBL deficiency is observed in almost 10% of healthy people, studies of associations between MBL deficiency and end-stage renal disease (ESRD) remain rare. The objective of the present study is to clarify the significance of the LP in maintenance hemodialysis (HD) patients, especially in terms of MBL levels. Two hundred and forty-four HD patients who had been followed up for 74±84months and 199 healthy controls were included in this study. Measurements of serum concentrations of MBL, L-ficolin, and MASP-2 were performed. Low serum MBL levels (<0.1µg/mL) in the patients were confirmed by examination of a point mutation in the Mbl-2 gene. Seventeen HD patients (7%) and 20 healthy controls (10%) had MBL deficiency. During the follow-up period, 99 patients died. There was no significant difference in the frequency of deaths by infectious diseases between MBL deficient and non-deficient patients. In both patients and healthy controls with MBL deficiency, the serum concentration of L-ficolin tended to be high, and that of MASP-2 was significantly high (P<0.05). MBL deficiency is not a risk factor for HD induction or life-threatening infections. It is postulated that the elevation of concentration of the two components of the LP, L-ficolin and MASP-2, may compensate for the insufficient activity of the LP in MBL deficiency.

Mannan Binding Lectin (MBL) genotypes coding for high MBL serum levels are associated with rheumatoid factor negative rheumatoid arthritis in never smokers

Introduction

Previous studies have provided inconsistent results on whether variants in the MBL2 gene, coding for the complement-activating mannan-binding lectin (MBL) protein, associate with rheumatoid arthritis (RA). We re-evaluated this in context of the main environmental and genetic risk factors (smoking, HLA-DRB1 'shared epitope' (SE), PTPN22*620W), which predispose to rheumatoid factor (RF) and/or anti-citrullinated-protein antibody (ACPA)-positive RA.

Methods

In this population-based EIRA study, rheumatoid factor (RF), ACPA, smoking, SE and PTPN22*620W status was determined in incident RA cases and matched controls. MBL-high (n = 1330) and MBL-low (n = 1257) genotypes predicting MBL levels were constructed from four promoter and exon-1 polymorphisms in the MBL2 gene. Odds ratios with 95% confidence interval (OR, 95% CI) were calculated by logistic regression. In extended families (n = 316), previously reported data were re-analyzed, considering RF and smoking.

Results

MBL-high genotypes tended to be associated with RF-negative (OR = 1.20, 95% CI 0.96-1.51) but not RF-positive (OR = 1.00, 95% CI 0.83-1.20) RA. Results divided by ACPA status did not differ. When stratified for smoking, MBL-high genotype was strongly associated with RF-negative RA in never smokers (OR = 1.82, 95% CI 1.24-2.69) but not in ever smokers (OR = 0.96, 95% CI 0.73-1.30). In never smokers, the association was observed in both the RF-negative/ACPA-negative (OR = 1.67, 95% CI 1.10-2.55) and RF-negative/ACPA-positive subgroups (OR = 3.07, 95% CI 1.37-6.89), and remained on an SE/PTPN22*620W negative background. In the extended families, the reported association between high MBL and RA was in fact confined to never smokers.

Conclusions

High MBL may predispose to RF-negative RA but only in individuals who have never smoked. This illustrates the importance of phenotypic subgrouping in genetic studies.

Mannose binding lectin gene (MBL2) functional polymorphisms are associated with systemic lupus erythematosus in southern Brazilians

Susceptibility to systemic lupus erythematosus (SLE) has been associated with immunologic, environmental, and genetic factors. To uncover a possible association between MBL2 gene polymorphisms and SLE, we analyzed functional polymorphisms in the promoter and first exon of the MBL2 gene in 134 Brazilian SLE patients and 101 healthy controls. Genotype and allele frequencies of MBL2 A/O polymorphism were significantly different between patients and controls, and the O allele was associated with an increased risk of SLE. An association between low mannose binding lectin (MBL) producer combined genotypes and increased risk for SLE was also reported. Furthermore, when stratifying SLE patients according to clinical and laboratory data, an association between the A/O genotype and nephritic disorders and between the X/Y genotype and antiphospholipid syndrome was evident. Combined genotypes responsible for low MBL production were more frequently observed in SLE patients with nephritis. Our results indicate MBL2 polymorphisms as possible risk factors for SLE development and disease-related clinical manifestations.

Lack of genetic association of promoter and structural variants of mannan-binding lectin (MBL2) gene with susceptibility to generalized vitiligo

BACKGROUND

Vitiligo is a common depigmenting disorder resulting from the loss of functional melanocytes in the skin. It is hypothesized to be of autoimmune origin. Mannan-binding lectin (MBL) plays an important role in innate immunity. It helps in the clearance of apoptotic cells and in complement activation. Genetic variability due to structural and promoter polymorphisms in the MBL2 gene has been reported to be associated with increased risk for several autoimmune diseases including vitiligo.

OBJECTIVES

The aim of this study was to explore whether MBL2 structural and promoter polymorphisms are associated with generalized vitiligo in Gujarat where the prevalence of vitiligo is alarmingly high.

MATERIALS AND METHODS

We undertook a case-control study to investigate the association of MBL2 gene exon 1 polymorphisms - codon 52, codon 54 and codon 57 as well as promoter -221 polymorphism in 92 patients with generalized vitiligo and 94 unaffected age-matched controls by polymerase chain reaction-heteroduplex analysis.

RESULTS

The genotype and allele frequencies of MBL2 structural and promoter polymorphisms did not differ significantly between the control and patient population (P-values: P < 0.019 for codon 52, P < 0.373 for codon 54, P < 0.855 for codon 57 and P < 0.889 for -221 promoter polymorphisms) after Bonferroni's correction for multiple testing, which suggests that there is no association of MBL2 structural and promoter polymorphisms with generalized vitiligo.

CONCLUSIONS

Our results suggest that the well-documented structural and promoter polymorphisms of the MBL2 gene may not be associated with generalized vitiligo in the Gujarat population.

Lack of association of mannose-binding lectin gene polymorphisms with development and clinical manifestations of systemic lupus erythematosus in Chinese children

Mannose-binding lectin (MBL) gene polymorphisms may be associated with adult-onset systemic lupus erythematosus (SLE), but studies in children with SLE are rare. This study tested the genetic association between MBL polymorphisms and paediatric-onset SLE in a cohort of Chinese children in Taiwan. In all 150 children with SLE and 100 healthy controls of comparable age were genotyped for codon 52, 54 and 57 mutations of the MBL gene using a polymerase chain reaction–based assay. Clinical manifestations, organ involvement, disease activity, laboratory characteristics and outcome were recorded and compared between patients with different MBL genotypes. Codon 54 mutation was fairly common in both SLE patients and controls, whereas codon 52 and codon 57 mutations were not detected in our study subjects. No statistically significant differences were found in allele frequencies of the codon 54 mutation between SLE and control groups. Moreover, no association was found between this MBL polymorphism and clinical manifestations, organ involvement, disease activity, laboratory characteristics or outcome of SLE. These results suggest that MBL polymorphisms do not influence susceptibility to paediatric-onset SLE and do not influence clinical manifestations of SLE in Chinese children.

Mannose-binding lectin polymorphisms are not associated with rheumatoid arthritis--confirmation in two large cohorts

OBJECTIVES

In RA, conflicting results have been described on the association between genotypes of the complement factor mannose-binding lectin (MBL) and disease susceptibility and severity. This might be due to underpowerment of previous research work and the fact that no confirmation cohorts were used. Therefore a different approach is warranted.

METHODS

MBL2 gene polymorphisms were determined in two RA cohorts (378 and 261 cases) and 648 controls. Considering MBL polymorphisms, cases and controls were categorized in groups of high, intermediate and low MBL production. The total sample size allows detection of a potential association between RA susceptibility and MBL groups with an odds ratio of 1.37 (alpha < 0.05; 1-beta > 0.8). Disease severity as defined by the need for anti-TNF therapy was also analysed for possible associations with MBL groups.

RESULTS

There was no difference in the frequencies between MBL genotypes of RA cases and controls that are associated with high (cases 54.4%, controls 57.0%), intermediate (cases 28.9%, controls 27.5%) or low (cases 16.7%, controls 15.5%) MBL production. Furthermore, there was no association between MBL groups and disease severity.

CONCLUSIONS

MBL genotype groups are not associated with RA disease susceptibility or severity in this large study including a confirmation cohort. Compared with previous smaller studies these results add to more definite conclusions.

The role of mannose-binding lectin in systemic lupus erythematosus

Susceptibility to systemic lupus erythematosus (SLE) is associated with genetic, hormonal, immunological, and environmental factors. Many genes have been related with the appearance of SLE, including several loci that code different complement components and their receptors. Some genetic deficiencies of complement molecules are strongly associated with SLE, probably because these deficiencies could cause decreased clearance of apoptotic cell material. As a consequence of the apoptotic material accumulation, high levels of autoantigens can be presented inappropriately to the immune system in an inflammatory context, resulting in an imbalance on the mechanisms of immunological tolerance, immune system activation, and autoantibody production. Recent studies proposed a role to the mannose-binding lectin (MBL) in the SLE physiopathogenesis. This protein activates the complement system, and the presence of several polymorphisms at the promoter and coding regions of the MBL-2 gene determines alterations at the plasma levels of MBL. Some of these polymorphisms have been associated with SLE susceptibility, as well as with clinical and laboratory typical features of this disease, cardiovascular events, and infections. Besides, it has been described that the presence of anti-MBL autoantibodies in sera of SLE patients can influence MBL plasma levels and its functional activity.

Anti-MBL autoantibodies in patients with rheumatoid arthritis: prevalence and clinical significance

Occurrence of autoantibodies in patients' sera is the characteristic feature of autoimmune disorders. We assessed the presence of anti-mannose binding lectin (MBL) autoantibodies in the sera of 107 rheumatoid arthritis (RA) patients and 121 control subjects by enzyme immunoassay. Elevated levels of anti-MBL autoantibodies in the sera of RA patients (P<0.0001) was detected for the first time. The ratios of anti-MBL positive in RA patients and controls were respectively 60.7% and 1.65%. Experiments were then designed to understand the functional relevance of these autoantibodies. An inverse correlation of anti-MBL autoantibodies with serum MBL levels (P=0.001) and MBL complex activity (P=0.02) was observed without genetic association between MBL polymorphisms and anti-MBL autoantibody secretion. A significant increase (P=0.038) in the level of anti-MBL autoantibodies was observed in 23 synovial fluid samples in comparison to the serum samples. Moreover, the anti-MBL autoantibodies were found to be more often present in the sera of RA patients (60.75% sensitivity, 98.35% specificity and 0.913 area under the ROC curve) in comparison to the IgM and IgG isotypes of rheumatoid factors (RF). Anti-MBL autoantibodies were still positive in 25.23% RA patients when both the RF isotypes were negative. Also, in RA patients, at all stages of disease activity and joint deformity, anti-MBL autoantibodies were more often present than both the RF isotypes. Therefore, the significant presence of anti-MBL autoantibodies enunciates that anti-MBL autoantibodies might have a diagnostic value; however, more studies are needed to confirm the role of anti-MBL autoantibodies in the diagnosis of rheumatoid arthritis.

Phase I Safety, Tolerability, and Pharmacokinetic Study of Recombinant Human Mannan-Binding Lectin

Mannan-binding lectin (MBL), a human plasma protein, plays an important role in the innate immune defence. MBL recognizes microorganisms through surface carbohydrate structures. Due to genetic polymorphisms, MBL plasma concentrations range from 5 to 10,000 ng/mL. Approximately 30% of the human population have low levels of MBL (below 500 ng/mL). MBL deficiency is associated with increased susceptibility to infections in immunosuppressed individuals, e.g., during chemotherapeutically induced neutropenia. Replacement therapy with MBL may be beneficial in this patient group, and recombinant human MBL (rhMBL) is in development as a novel therapeutic approach. To assess the safety, tolerability, and pharmacokinetics of rhMBL, a placebo-controlled double-blinded study was performed in MBL-deficient healthy male subjects. rhMBL was administered as both single intravenous (i.v.) infusions (0.01, 0.05, 0.1, and 0.5 mg/kg) and repeated i.v. infusions (0.1 or 0.3 mg/kg given at 3-day intervals). There were no difference in incidence and type of adverse events reported in the study between the groups of subjects receiving rhMBL and the placebo group. All adverse events reported as drug-related were mild and no serious adverse events were recorded. There were no clinically significant changes in laboratory evaluations, ECG or vital signs, and no anti-MBL antibodies were detected following rhMBL administration. After single i.v. doses of rhMBL the maximal plasma levels increased in a dose-dependent manner reaching a geometric mean of 9710 ng/mL+/-10.5% in the highest dose group (0.5 mg/kg), with an elimination half-life of approximately 30 h. No rhMBL accumulation in plasma was observed following repeat dosing. Administration of rhMBL restored the ability to activate the MBL pathway of the complement system without non-specific activation of the complement cascade. In conclusion, no safety or tolerability concern was raised following rhMBL administration no signs of immunogenicity detected, and an rhMBL plasma level judged sufficient to achieve therapeutic benefit (>1000 ng/mL) can be achieved.

Mannan-binding lectin and complement C4A in Icelandic multicase families with systemic lupus erythematosus

OBJECTIVE

To determine whether low mannan-binding lectin (MBL) and C4A null alleles (C4AQ0) are associated with systemic lupus erythematosus (SLE) in multicase families with SLE.

METHODS

Low MBL level was determined by measuring serum levels and by genotyping for mutant structural (B/C/D, designated as 0) and promoter (LX) alleles (by real-time polymerase chain reaction). C4AQ0 was detected by protein electrophoresis and corroborated with haplotype and genotype analysis. In nine Icelandic families, 24 patients with SLE were compared with 83 first-degree and 23 second-degree relatives without SLE. Twenty four unrelated family members and a population group of 330 Icelanders served as controls.

RESULTS

Overall, the frequency of low MBL genotypes (0/0, LX/0 and wild-type/0) tended to be higher in patients with SLE than in their first-degree and second-degree relatives (p = 0.06), but the frequency was similar in the families and in the controls (p = 0.6). The frequency of C4AQ0 was, however, increased in patients and their relatives compared with that in the controls (p = 0.04). The combination of low MBL genotypes and C4AQ0 was found more often in the patients than in their relatives (p = 0.03) and controls (p = 0.02). However, low MBL level was observed only in patients and first-degree relatives in five of the nine multicase families. In these five families, patients with SLE had low MBL genotypes more often (64%) than their first-degree (38%) and second-degree (0%) relatives (p = 0.001), and the patients with SLE also had, accordingly, lower MBL levels than their relatives (p = 0.001).

CONCLUSIONS

These findings indicate that low MBL levels can predispose people to SLE and highlight the genetic heterogeneity of this disease.

The mannose-binding lectin gene polymorphisms and systemic lupus erythematosus: two case-control studies and a meta-analysis

OBJECTIVE

Mannose-binding lectin (MBL) enhances opsonization and activates complement. Dysfunctional alleles of MBL have been associated with low plasma concentrations of MBL and increased risk of systemic lupus erythematosus (SLE), but genotyping studies have shown inconsistent results. We performed case-control studies of the MBL polymorphisms in 2 Caucasian cohorts and a meta-analysis incorporating all published results of MBL genotyping in SLE to explore whether the MBL functional variants are associated with SLE.

METHODS

MBL genotypes at 7 single-nucleotide polymorphisms were sequenced in 96 European American patients with SLE and 96 age-, race-, and sex-matched controls. MBL codons 52, 54, and 57 were genotyped in 285 German patients with SLE and 200 race-matched controls. Allele frequencies of all known variants were tallied for meta-analysis.

RESULTS

Although there was a trend toward association with MBL polymorphisms in both patient cohorts evaluated, none of them was significantly associated with SLE on its own. Seventeen comparisons from 15 studies were included in the meta-analysis. Publication bias was excluded by Egger's regression test (P = 0.14). The overall odds ratio for MBL codon 54 variant B was 1.406 (95% confidence interval 1.221-1.608; P < 0.001). Stratification by ethnicity showed significantly increased odds ratios for association of the MBL codon 54 B variant with SLE in African, Asian, and Caucasian cohorts.

CONCLUSION

Meta-analysis of all available studies on MBL polymorphisms and SLE shows that MBL variant alleles such as MBL exon 1 codon 54 B, promoter -550 L, and promoter -221 X are SLE risk factors. This association is robust and persists after incorporation of data from our 2 cohorts in which the association failed to reach significance.

Mannose-binding lectin: biology and clinical implications

The innate host defence molecule mannose-binding lectin (MBL) has attracted great interest as a potential candidate for passive immunotherapy to prevent infection. MBL is a multimeric lectin that recognizes a wide array of pathogens independently of specific antibody, and initiates the lectin pathway of complement activation. The basic structural unit is a triple helix of MBL peptides, which aggregate into complement-fixing higher-order structures (tetramers, pentamers and hexamers). The gene encoding MBL, MBL2, contains several common polymorphisms that influence transcription and assembly of the molecule into multimers. MBL2 coding alleles associated with low blood levels are present in up to 40% of Caucasoids, with up to 8% having genotypes associated with profound reduction in circulating MBL levels. Low-producing MBL2 variants and low MBL levels are associated with increased susceptibility to and severity of a variety of infective illnesses, particularly when immunity is already compromised--for example, in infants and young children, patients with cystic fibrosis, and after chemotherapy and transplantation. These observations suggest that administration of recombinant or purified MBL may be of benefit in clinical settings where MBL deficiency is associated with a high burden of infection. This review provides a background to MBL biology and disease associations, and identifies the exciting therapeutic possibilities of MBL replacement.

Association of mannose-binding lectin gene (MBL2) polymorphisms with rheumatoid arthritis in an Indian cohort of case-control samples

Single nucleotide polymorphisms in the mannose-binding lectin (MBL2) gene, as well as the serum MBL2 level, have been associated with various autoimmune diseases. We investigated whether such polymorphisms and/or the serum MBL2 level were associated with rheumatoid arthritis (RA) in an Indian population. The frequency of the B variant (codon 54) of the MBL2 gene was quite frequent in the healthy Indian population and was significantly (P=6.35x10(-6)) lower in RA patients. We replicated this association (P=1.78x10(-5)) in an independent cohort of control individuals. Promoter polymorphism at -550 nt showed a significant overrepresentation (P=0.003) of the minor allele G in severe RA patients compared with the less severe group. Haplotype LYA frequency was significantly (P=0.03) high in the less severe group, while the frequency of the HYA haplotype was significantly (P=0.04) increased in the severe RA patients. No statistically significant difference in serum MBL2 was observed as a whole, but the individuals homozygous for the LYA haplotype had significantly lower (P=0.017) serum MBL2 levels compared with individuals homozygous for the HYA haplotype. Therefore, the B variant of the MBL2 gene may be associated with protection from RA in our study population, and the promoter polymorphism (-550 nt) seems to have some role in disease progression.

Association of MBL gene polymorphisms with major bacterial infection in patients treated with high-dose chemotherapy and autologous PBSCT

A growing body of evidence indicates that genetic factors are involved in an increased risk of infection. We investigated whether mannose-binding lectin (MBL) gene polymorphisms that cause low levels of MBL are associated with the occurrence of major infections in patients, mainly bearing hematological malignancies, after high-dose chemotherapy (HDT) rescued by autologous peripheral blood stem cell transplantation (auto-PBSCT). A retrospective evaluation of 113 patients treated with HDT and auto-PBSCT revealed that the low-producing genotypes, B/B and B/LXA, were associated with major bacterial infection (P=0.0016, OR 7.9). We next performed a nation-wide large-scale study to assess the allele frequency of the MBL coding mutation in a total of 2623 healthy individuals in Japan. The frequency of allele B was estimated to be approximately 0.2, almost the same in seven different areas of Japan. This common occurrence suggests that MBL deficiency may play an important role in the clinical settings of immunosuppression.

The natural history and prognosis of rheumatoid arthritis: association of radiographic outcome with process variables, joint motion and immune proteins

OBJECTIVE

The purposes of the present study were: 1) to investigate how the long-term course of outcome and inflammatory variables could be described in individual patients and suitably summarized in groups of patients; 2) to investigate the associations between outcome and inflammatory variables on the basis of the defined summary measures; and 3) to investigate new prognostic aspects of RA by means of frozen sera and DNA specimens.

PATIENTS AND METHODS

During the period 1966-78, 685 Danish Caucasian patients with RA, classified according to the 1958 American Rheumatism Association (ARA) criteria, were admitted to the Department of Rheumatology of Aarhus University Hospital. For scientific purposes all patients went through the same examination programme, including biochemical variables, clinical evaluation of 68 diarthrodial joints, and radiographic evaluation of 46 diarthrodial joints. Since 1987, data from these patients have been organized in a database. The data are arranged according to onset of disease. This thesis is based on about 600,000 data-points from 257 patients.

RESULTS

The thesis is based on six studies. The first study shows that early symptomatic improvement of RA during gold treatment was stable over several years, but when evaluated radiographically, the condition continued to deteriorate. In the second study, six main types of radiographic progression were identified: (a) a rare type with no radiographic progression at all (<1%); (b) a type with a slow or moderate onset, but an increasing progression rate (exponential growth type) (9%); (c) a linear type (30%); (d) a type with a moderate to fast onset, and a stable progression rate (the square root type) (11%); (e) a type with a fast onset, but a later decreasing progression rate (the first order kinetics type) (30%) and (f) a type characterized by slow onset, then acceleration and later deceleration (the sigmoid type) (20%). The fact that there was a systematic progression was used to define a system of radiographic events, which could be used as outcome measures in prediction models of the long-term course of RA. The third study shows that low serum levels of the complement-activating serum lectin, mannan (mannose) binding protein (lectin) (MBP = MBL), are associated with a higher erythrocyte sedimentation rate (ESR) (p=0.006), joint swelling score (JS score) (p=0.019), limitation of joint motion score (LM score) (p=0.027), and annual increase in radiographic destruction score (R score) (p=0.053). The fourth study demonstrated a highly significant association between summary measures of inflammatory variables and radiographic outcome, as defined in the second study, indicating that the degree of inflammation is important for the development of destructive joint damage in RA. The fifth study showed that MBL-insufficient patients (two defective structural MBL alleles, or one defective allele combined with a low-expression variant of the normal allele) had a relative risk of a severe radiographic event of 3.1 compared with the MBL competent group (p<0.0001). The sixth study showed that the relative risk (RR) of early interleukin (IL)-1alpha auto-antibodies (aAb) positive patients developing serious radiographic joint destruction was significantly lower than for IL-1alpha aAb-negative patients, RR=0.29 (p=0.04). In rheumatoid factor (RF) positive patients RR was only 0.18 (p=0.02). Patients who seroconverted >2 years after the onset of RA showed the most aggressive development of joint erosion, with RR of serious radiographic joint destruction of 2.56 (p=0.048). Other factors investigated in subgroups of the patients were HLA-DR4, chemokine receptor 5 (CCR 5) genotypes. IL-6 aAb, vascular endothelial growth factor (VEGF) aAb, and interferon (IFN)-gamma aAb. About 80% of the patients were HLA-DR4 positive, indicating the importance of HLA-DR4 as a predisposing factor for RA. There was no association between IL-6 aAb and radiographic outcome, or CCR5 genotypes and radiographic outcome. VEGF aAb and IFN-gamma aAb were quantitatively unimportant.

CONCLUSION

In spite of a general improvement in single measures of inflammatory variables, and a general deterioration in radiographic outcome of RA, there is a highly significant association between summary measures of inflammatory variables and radiographic outcome. The progression of radiographic damage in RA follows mathematical patterns. A new method of evaluating the long-term radiographic outcome by means of Kaplan-Meier plots is demonstrated. It is shown that MBL and IL-1alpha aAb are predictors of the prognosis of RA and may play important roles in the pathogenesis of RA.

Photosensitivity in rheumatic diseases

There have been a number of recent advances in the genetic understanding of photosensitive rheumatic diseases, especially subacute cutaneous lupus erythematosus and dermatomyositis. These advances support the concept that increased numbers of ultraviolet light-induced apoptotic cells in skin lead to a supra-threshold concentration of antigenic peptides. The current genetic data suggest that increased keratinocyte apopotosis can result from increased amounts of TNF-alpha that induce apoptosis due to a ultraviolet light-sensitive TNF promoter polymorphism or to decreased clearance of apototic cells due to polymorphisms associated with decreased serum levels of collectins such as C1q and mannose-binding lectin. These diseases are frequently oligogenic, and other yet to be elucidated genes will, in individual patients, lead to increased numbers of apoptotic cells associated with these cutaneous autoimmune diseases. In the presence of specific MHC class I and II genes, antigen-presenting cells initiate a primary immune response that leads to cutaneous, and likely systemic, autoimmune disease.

Influence of cytokine and mannose binding protein gene polymorphisms on human T-cell leukemia virus type I (hTLV-I) provirus load in HTLV-I asymptomatic carriers

Human T-cell leukemia virus type I (HTLV-I) provirus load differs more than 100-fold among carriers and a high provirus load in the peripheral blood mononuclear cells (PBMCs) is regarded as a risk factor for both preleukemic states and inflammatory diseases including HTLV-I-associated myelopathy (HAM). We examined polymorphisms in the genes for tumor necrosis factor (TNF), TNF receptor type 1 and 2, lymphotoxin (LT)-alpha, interleukin (IL)-1beta, IL-6, IL-10, monocyte chemoattractant protein (MCP)-1, and mannose binding protein (ManBP) in 143 HTLV-I carriers whether these polymorphisms affect the provirus load in the PBMCs of carriers. No significant association was observed between these polymorphisms and the provirus load. Homozygotes for a ManBP-variant allele, however, showed a tendency for the decreased number of provirus load. When combined, the data on the alleles of LT-alpha and MCP-1, HTLV-I carriers having high producer alleles of both genes showed a trend for increased provirus load. These data suggest that inflammation or an active immune response may induce an increased amount of HTLV-I-infected T cells, leading to a high provirus load.

Mannose binding lectin (MBL) polymorphisms associated with low MBL production in patients with dermatomyositis

One theory for the pathophysiology of photosensitive autoimmune skin diseases is that photoinduction of tumor necrosis factor alpha (TNFalpha) secretion leads to keratinocyte apoptosis and translocation of previously sequestered cellular antigens that then activate the immune system. We previously found an association of the overproducing TNFalpha-308 A variant with adult dermatomyositis and with subacute cutaneous lupus erythematosus. Here we focused on mannose binding lectin (MBL), which is one of several proteins involved in clearance of apoptotic cells and could thereby lessen photosensitive autoimmunity. We examined three variant MBL polymorphisms associated with decreased MBL protein (Asp54, Glu57, and the LX promoter polymorphism) in adult dermatomyositis, subacute cutaneous lupus erythematosus, and discoid lupus, and controls. The variant Asp54 allele was positively associated with adult dermatomyositis in a dose-responsive fashion (p=0.0004), as was the Glu57 allele (p=0.004). None of the three variant MBL alleles considered individually was significantly associated with either subacute cutaneous lupus erythematosus or discoid lupus. In adult dermatomyositis patients homozygous for the wild-type TNFalpha-308G allele (GG), i.e., presumably without elevated TNFalpha production, 69% had at least two of the MBL polymorphisms, versus 20% of healthy GG controls (p=0.0011). Combinations of low-producing MBL variants were over-represented in adult dermatomyositis in a dose-responsive fashion (p=0.0002). In adult dermatomyositis patients with one variant TNFalpha-308 A allele (GA), 46% had at least two MBL polymorphisms, versus 7% of GA controls (p=0.0077). Thus, low-producing MBL genes are very strongly associated with adult dermatomyositis. Our model is that genetic polymorphisms leading to overproduction of apoptotic keratinocytes and then impaired clearance of these cells contribute to the pathogenesis of adult dermatomyositis, a photoinduced autoimmune skin disease.

Genetic approaches to the investigation of rheumatoid arthritis

The investigation of genetic factors affecting the development or severity of rheumatoid arthritis may give new insights into the pathways involved in disease pathogenesis and lead to the identification of novel therapeutic targets. Recently, several novel approaches have been used in the attempt to unravel the complex association of rheumatoid arthritis with the human leukocyte antigen ( HLA ) gene region. It is clear that non-HLA genes are also involved in disease pathogenesis, and identifying them remains a challenge. In the past year, considerable headway has been made in this field, and some interesting strategies have been used. This review summarizes the results of many of the HLA and non-HLA studies and tries to draw lessons from the investigation of genetic susceptibility factors in other complex diseases.

Association of mannose-binding lectin gene variation with disease severity and infections in a population-based cohort of systemic lupus erythematosus patients

This study describes the importance of mannose-binding lectin (MBL) variant alleles for systemic lupus erythematosus (SLE) and accompanying infections in a population-based cohort. MBL alleles were determined in 99 SLE patients recruited from a representative Danish region. Patients were classified according to the 1982 revised ACR criteria as definite SLE (D-SLE) (n = 77) fulfilling > or =4 criteria and incomplete SLE (I-SLE) (n = 22) with 0.99, respectively). A meta-analysis of eight previously published studies suggested that the presence of MBL variant alleles confer a 1.6 times overall increased risk for D-SLE (P < 0.00001). MBL variant allele carriers had higher disease activity (SLEDAI-index) in a 2-year follow-up period (P = 0.02) and had an increased risk of acquiring complicating infections in general (P = 0.03) and respiratory infections in particular (P = 0.0006). Only in SLE patients fulfilling > or =4 ACR criteria an increased frequency of MBL variant alleles was found. MBL variant alleles were also associated with increased risk of disease activity and of complicating infections indicating that the MBL gene is an SLE disease modifier locus.

Mannose-binding lectin polymorphisms in a Canary Islands (Spain) population

We have compared the structural and promoter variants of the mannose-binding lectin (MBL) gene in a population from Gran Canaria with that from other populations previously reported. The observed frequencies of the seven alleles of the MBL gene in our population were: HYPA, 0.24; LYQA, 0.22; LYPA, 0.08; LXPA, 0.19; LYPB, 0.17; LYQC, 0.03 and HYPD, 0.07. The frequency of non-producer alleles and of MBL-deficient individuals in our population is higher than in other European and Asian population.