Increased activity of the mannan-binding lectin complement activation pathway in patients with colorectal cancer

Independent effects of genetic variations in mannose-binding lectin influence the course of HIV disease: the advantage of heterozygosity for coding mutations

BACKGROUND

The in vivo impact of mannose-binding lectin (MBL), a molecule involved in innate immunity, on the pathogenesis of human immunodeficiency virus (HIV)-1 infection and AIDS is unknown.

METHODS

A total of 1102 HIV-positive and 2213 HIV-negative adult subjects were screened for polymorphisms in the coding and promoter regions of MBL2, the gene that encodes MBL.

RESULTS

Variations in MBL2 did not influence the risk of acquiring HIV-1. Heterozygosity for coding mutations (O allele) and homozygosity for the -221 promoter polymorphism (X allele) in MBL2 were associated with a delay in and an accelerated rate of disease progression, respectively. MBL2 variations influenced the rate of progression to AIDS-defining illnesses. In a multivariate model, the effects of MBL2 variations were independent of several parameters known to influence disease progression, including steady-state viral load, baseline CD4(+) T cell counts, and delayed-type hypersensitivity skin test responses, an in vivo marker of cell-mediated immunity. The effects of MBL2 variations were most evident in those who possessed protective genotypes of CCR5 and a high copy number of CCL3L1, the most potent HIV-suppressive CCR5 ligand.

CONCLUSIONS

MBL2 genotypes are independent determinants of HIV disease progression and heterozygosity for MBL2 coding mutations confer disease-retarding effects. MBL-dependent immune responses may play a role in the pathogenesis of HIV infection.

Biological variation in circulating levels of mannan-binding lectin (MBL) and MBL-associated serine protease-2 and the influence of age, gender and physical exercise

Mannan-binding lectin (MBL) and MBL-associated serine protease 2 (MASP-2) are central components of the MBL pathway of complement activation, and may have potential as clinical biomarkers in colorectal cancer (CRC). Prior to clinical usage, knowledge of the biological variations of the molecules is needed. We here investigate variations of MBL and MASP-2 in healthy persons over time and in relation to gender, age and physical activity. MBL and MASP-2 concentrations were determined in serum from healthy adults over a 3-week period and this was repeated 6 months later (n = 32); during a 24-h period (n = 16); and in relation to physical exercise (n = 14). Concentrations in serum and plasma were compared (n = 198). No significant variation over 6 months and no circadian variation was found for MBL (P = 0.39 and P = 0.34 respectively) or MASP-2 (P = 0.54 and P = 0.55). Physical exercise did not affect the levels (P > 0.8). Serum and plasma levels were only marginally different, and were independent of age and gender. Circulating levels of MBL and MASP-2 are stable over time in healthy individuals, which is advantageous for their potential application as biomarkers.

Genetic influences on mannan-binding lectin (MBL) and mannan-binding lectin associated serine protease-2 (MASP-2) activity

The lectin pathway of the complement system is activated when Mannan-binding lectin (MBL) in complex with MASP-2 binds microorganisms. Polymorphisms in both genes are responsible for low serum levels, which associate with increased risk of infection and autoimmune disease. The present study includes 1215 MBL measurements and 1214 MASP-2 activity measurements in healthy Danish adult twins. Total MASP-2 activity was estimated by C4 cleaving activity of samples diluted in an excess of MBL. Twin-twin correlations were higher in monozygotic (MZ) than in dizygotic (DZ) twins for both traits. Heritabilites of MBL levels and MASP-2 activity were estimated using structural equation modeling allowing assessment of the contribution of common genes affecting both traits. The estimated heritability was 0.77 [95% CI 0.64;0.91] for MBL levels and 0.75 [95% CI 0.59;0.81] for MASP-2 activity with the presence of additive genetic factors, shared environmental factors, and non-shared environmental factors. The genetic correlation, i.e., common genetic factors affecting MBL and MASP-2 activity was estimated to r(g) = 0.34 [0.25;0.42]. The data indicate a strong genetic influence for the serum levels of MBL and for MASP-2 activity with a significant genetic correlation between the two traits.

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.

Clinical significance of mannose-binding lectin-associated serine protease-2 expression in esophageal squamous cell carcinoma

Mannan-binding lectin-associated serine protease-2 (MASP-2) is a serine protease involved in the activation of lectin complement pathway. The differential expression of MASP-2 in human esophageal squamous cell carcinoma (ESCC) was recently reported from our laboratory using differential display. To determine the expression of MASP-2 protein, we raised a polyclonal antibody to human MASP-2 and used it for immunohistochemical analysis of MASP-2 in ESCCs. The antibody showed a single band of predicted molecular weight by western blotting. In normal human liver tissue, the cytoplasm was distinctly labeled by the antibody. Intriguingly, besides the cytoplasm, the nuclei of esophageal tumor cells were also labeled. To investigate the association of MASP-2 expression with esophageal tumorigenesis, its expression was analyzed in 51 primary ESCCs, 32 dysplasias, 21 histologically normal esophageal tissues and 6 adenocarcinomas by immunohistochemistry. Increased MASP-2 expression was observed in ESCCs (p = 0.001, Odd's ratio (OR) = 3.662) and in premalignant condition, dysplasia (p = 0.000, OR = 5.091) in comparison with the normal tissues. MASP-2 expression in ESCCs was associated with late clinical stage (p = 0.009, O.R. = 3.430) and nodal metastasis (p = 0.001, O.R. = 4.520). In conclusion, our antibody was demonstrated to be useful in recognizing MASP-2 expression on paraffin embedded tissue sections. To our knowledge, this is the first report showing MASP-2 expression in a solid tumor. MASP-2 expression in premalignant stage (dysplasia) as well as in ESCCs and its association with late clinical stage and nodal metastasis suggest that alteration in its expression is maintained during disease progression and is associated with aggressive tumor behavior.

Deficiency of mannose-binding lectin greatly increases susceptibility to postburn infection with Pseudomonas aeruginosa

Burn injury disrupts the mechanical and biological barrier that the skin presents against infection by symbionts like the Pseudomonas aeruginosa, a Gram-negative bacteria. A combination of local factors, antimicrobial peptides, and resident effector cells form the initial response to mechanical injury of the skin. This activity is followed by an inflammatory response that includes influx of phagocytes and serum factors, such as complement and mannose-binding lectin (MBL), which is a broad-spectrum pattern recognition molecule that plays a key role in innate immunity. A growing consensus from studies in humans and mice suggests that lack of MBL together with other comorbid factors predisposes the host to infection. In this study we examined whether MBL deficiency increases the risk of P. aeruginosa infection in a burned host. We found that both wild-type and MBL null mice were resistant to a 5% total body surface area burn alone or s.c. infection with P. aeruginosa alone. However, when mice were burned then inoculated s.c. with P. aeruginosa at the burn site, all MBL null mice died by 42 h from septicemia, whereas only one-third of wild-type mice succumbed (p = 0.0005). This result indicates that MBL plays a key role in containing and preventing a systemic spread of P. aeruginosa infection following burn injury and suggests that MBL deficiency in humans maybe a premorbid variable in the predisposition to infection in burn victims.

Serum mannan-binding lectin-associated serine protease 2 levels in colorectal cancer: relation to recurrence and mortality

PURPOSE

Mannan-binding lectin-associated serine protease 2 (MASP-2) is a plasma protein involved in inflammatory processes. MASP-2 circulates in complex with the protein mannan-binding lectin (MBL) or ficolins, and is activated to recruit the complement system when MBL binds to its targets. The level of MASP-2 is genetically determined, and the aim of the present study was to evaluate the effect of MASP-2 levels on postoperative infection, recurrence and survival.

EXPERIMENTAL DESIGN

MASP-2 concentrations were determined in serum from 605 patients collected before elective resection for primary colorectal cancer. The primary end points were postoperative infection, time to any recurrence, and time to death. The median time of follow-up was 7.9 years.

RESULTS

MASP-2 levels were not correlated to postoperative infections (P = 0.49). High MASP-2 levels significantly correlated with recurrent cancer disease [P = 0.03; hazard ratio (HR) = 1.4; 95% confidence interval (CI), 1.0-2.0] and with poor survival (P = 0.0005; HR = 1.4; 95% CI, 1.2-1.7). Multivariate statistical analysis, including age, gender, Dukes' stage of disease, tumor localization, and postoperative pneumonia, showed that the MASP-2 level had an independent prognostic value in the patients (P = 0.0001; HR = 1.5; 95% CI, 1.2-1.8).

CONCLUSION

In the cohort of patients with colorectal cancer investigated, MASP-2 concentration in serum proved to be an independent prognostic marker with high MASP-2 levels predicting recurrence and poor survival. Postoperative infection could not be shown to be associated with MASP-2 levels.

Preoperative mannan-binding lectin pathway and prognosis in colorectal cancer

PURPOSE

Deficiency of the mannan-binding lectin (MBL) pathway of innate immunity is associated with increased susceptibility to infections. In patients with colorectal cancer (CRC), postoperative infection is associated with poor prognosis. The aim of the present study was to evaluate (1) the relation between the MBL pathway and postoperative infectious complications and survival of patients resected for CRC, and (2) the role of MBL in acute phase response compared to C-reactive protein (CRP).

METHODS

Preoperative MBL concentration, MBL-associated serine protease (MBL/MASP) activity and CRP were determined in serum from 611 patients and 150 healthy controls. The patients were observed for 8 years. Postoperative infections, recurrence and survival were recorded.

RESULTS

The MBL pathway components were increased in the patients compared with the healthy controls (p < 0.0001). Low MBL levels were predictive of pneumonia (p = 0.01), and pneumonia (n = 87) was associated with poor survival (p = 0.003; HR = 1.5; 95% CI, 1.1 to 1.9). MBL and MBL/MASP activity showed no correlation with CRP (Spearman's rho = 0.02; 95% CI, -0.06 to 0.10).

CONCLUSION

Low preoperative MBL levels are predictive of pneumonia, which is associated with poorer survival. MBL concentration and MBL/MASP activity was not predictive of other postoperative infections or long-term prognosis, and showed no correlation with CRP.

Mannose-binding lectin: laying the stepping stones from clinical research to personalized medicine

As a key component of the complement system, mannose-binding lectin (MBL) is one of the linchpins of innate immunity. It is, therefore, not surprising that MBL2 genetic variants affecting the quantity and activity of the MBL protein in serum have been associated with increased susceptibility to infection and autoimmune diseases, and with poorer prognostic outcomes. This enhanced risk is particularly the case for children and immunosuppressed patients, especially when immunity is further compromised by coexistent primary or secondary immune deficiencies. In several disease areas, such as sepsis, cystic fibrosis, and recurrent childhood infections, the association between low MBL-producing allelic variants and disease risk and/or severity is particularly strong. It is here that the use of MBL testing and replacement therapy has reached the threshold of personalized medicine. The role of MBL in health and disease, advances in MBL testing methodologies and key areas for possible applications of MBL replacement therapy are reviewed.