OBJECTIVE

To understand the expression of genes involved in different complement pathways in the retina and retinal pigment epithelium (RPE)/choroid under physiologic conditions and how their expression is regulated by inflammatory cytokines.

METHODS

The expression of complement components of the classical pathway (CP), mannose-binding lectin (MBL) pathway, alternative pathway (AP), and terminal pathway in the retina and RPE/choroid was determined by conventional reverse transcription polymerase chain reaction (RT-PCR). The effect of inflammatory cytokines, tumor necrosis factor-alpha (TNF-α, 20 ng/ml), interleukin (IL)-6 (10 ng/ml), interferon-gamma (IFN-γ, 100 ng/ml) or lipopolysaccharides (LPS, 1 μg/ml) on the expression of these complement component genes was tested in vitro in primary cultured RPE cells and a microglial cell line (BV2 cells) and quantified by real-time RT-PCR.

RESULTS

In the CP, complements C1qb, C1r, C1s, C2, and C4 were constitutively expressed by retina and RPE/choroid. Complement factor H and factor B of the AP as well as C3 were also detected in the retinal and RPE/choroidal tissues. In the MBL pathway, low levels of mannose-binding lectin (MBL)-associated serine protease (MASP)-1 in the retina and RPE/choroid and MASP2L in the retina were detected. Other components, including mannose-binding lectin 1 (MBL1), mannose-binding lectin 2 (MBL2), complement factor I (CFI), complement component 5 (C5) and complement factor H-related protein 1 (CFHR1), were not detected in either the retina or the RPE/choroid. The expression of CP- and AP-complement component genes in RPE and microglial cells was upregulated by interferon (IFN)-γ treatment. Treatment with TNF-α selectively upregulated the expression of C1s and C3 genes but downregulated complement factor H gene expression in RPE and microglial cells. The expression of genes involved in the MBL pathway was not affected by the inflammatory cytokines tested in this study.

CONCLUSIONS

Retina and RPE/choroid express a variety of complement components that are involved mainly in the CP and AP. RPE and microglial cells are the main sources of retinal complement gene expression. Retinal complement gene expression is regulated by inflammatory cytokines, such as IFN-γ and TNF-α.

Mannose-binding lectin (MBL2) variants that decrease the plasma level of the protein or encode dysfunctional proteins are frequently associated with the severity of a number of infections and autoimmune disorders. The high frequencies of these variants in most populations of the world are probably maintained by some selective advantage against widespread diseases. We found 14 new MBL2 allelic haplotypes, two of them with non-synonymous variants, by screening 136 children with uncomplicated malaria, 131 children with severe malaria and 39 older healthy schoolchildren. We also found a significant association of a novel variant with susceptibility to severe malaria (P=0.010). Increased MBL plasma levels and corresponding MBL2 genotypes were associated with lower concentration of several cytokines and chemokines in plasma of malaria patients. We suggest that malaria could have been one of the evolutionary driving forces shaping the MBL2 polymorphism in the African population.

Structural variants of the Mannose Binding Lectin (MBL) cause quantitative and qualitative functional deficiencies, which are associated with various patterns of susceptibility to infectious diseases and other disorders. We determined genetic MBL variants in 2010 Ghanaian patients with pulmonary tuberculosis (TB) and 2346 controls and characterized the mycobacterial isolates of the patients. Assuming a recessive mode of inheritance, we found a protective association between TB and the MBL2 G57E variant (odds ratio 0.60, confidence interval 0.4-0.9, P 0.008) and the corresponding LYQC haplotype (P(corrected) 0.007) which applied, however, only to TB caused by M. africanum but not to TB caused by M. tuberculosis. In vitro, M. africanum isolates bound recombinant human MBL more efficiently than did isolates of M. tuberculosis. We conclude that MBL binding may facilitate the uptake of M. africanum by macrophages, thereby promoting infection and that selection by TB may have favoured the spread of functional MBL deficiencies in regions endemic for M. africanum.

Human mannose-binding protein (MBL) is a component of innate immunity. To capture the common genetic variants of MBL2, we resequenced a 10.0 kb region that includes MBL2 in 102 individuals representing four major US ethnic groups. In all, 87 polymorphic sites were observed, indicating a high level of heterozygosity (total pi=18.3 x 10(-4)). Estimates of linkage disequilibrium across MBL2 indicate that it is divided into two blocks, with a probable recombination hot spot in the 3' end. Three non-synonymous SNPs in exon 1 of the encoding MBL2 gene and three upstream SNPs form common 'secretor haplotypes' that can predict circulating levels. Common variants have been associated with increased susceptibility to infection and autoimmune diseases. The high frequencies of B, C and D alleles in certain populations suggest a possible selective advantage for heterozygosity. There is limited diversity of haplotype structure; the 'secretor haplotypes' lie on a restricted number of extended haplotypes, which could include additional linked SNPs, which might also have possible functional implications. There is evidence for gene conversion in the region between the two blocks, in the last exon. Our data should form the basis for conducting MBL2 candidate gene association studies using a locus-wide approach.

Because chronic intestinal inflammation is a risk factor for colorectal cancer, we hypothesized that genetic variants of inflammatory mediators, such as mannose-binding lectin 2 (MBL2), are associated with colon cancer susceptibility. Here, we report the association of 24 MBL2 single-nucleotide polymorphisms (SNP) and corresponding haplotypes with colon cancer risk in a case-control study. Four SNPs in the 3'-untranslated region (UTR) of the gene (rs10082466, rs2120132, rs2099902, and rs10450310) were associated with an increased risk of colon cancer in African Americans. ORs for homozygous variants versus wild-type ranged from 3.17 [95% confidence interval (CI), 1.57-6.40] to 4.51 (95% CI, 1.94-10.50), whereas the 3'-UTR region haplotype consisting of these four variants had an OR of 2.10 (95% CI, 1.42-3.12). The C allele of rs10082466 exhibited a binding affinity of miR-27a and this allele was associated with both lower MBL plasma levels and activity. We found that 5' secretor haplotypes known to correlate with moderate and low MBL serum levels exhibited associations with increased risk of colon cancer in African Americans, specifically as driven by two haplotypes, LYPA and LYQC, relative to the referent HYPA haplotype (LYPA: OR, 2.60; 95% CI, 1.33-5.08 and LYQC: OR, 2.28; 95% CI, 1.20-4.30). Similar associations were not observed in Caucasians. Together, our results support the hypothesis that genetic variations in MBL2 increase colon cancer susceptibility in African Americans.

BACKGROUND

Common variants in genes related to inflammation, innate immunity, epithelial cell function, and angiogenesis have been reported to be associated with risks for Acute Lung Injury (ALI) and related outcomes. We tested whether previously-reported associations can be validated in an independent cohort at risk for ALI.

METHODS

We identified 37 genetic variants in 27 genes previously associated with ALI and related outcomes. We prepared allelic discrimination assays for 12 SNPs from 11 genes with MAF>0.05 and genotyped these SNPs in Caucasian subjects from a cohort of critically ill patients meeting criteria for the systemic inflammatory response syndrome (SIRS) followed for development of ALI, duration of mechanical ventilation, and in-hospital death. We tested for associations using additive and recessive genetic models.

RESULTS

Among Caucasian subjects with SIRS (n = 750), we identified a nominal association between rs2069832 in IL6 and ALI susceptibility (OR(adj) 1.61; 95% confidence interval [CI], 1.04-2.48, P = 0.03). In a sensitivity analysis limiting ALI cases to those who qualified for the Acute Respiratory Distress Syndrome (ARDS), rs61330082 in NAMPT was nominally associated with risk for ARDS. In terms of ALI outcomes, SNPs in MBL2 (rs1800450) and IL8 (rs4073) were nominally associated with fewer ventilator-free days (VFDs), and SNPs in NFE2L2 (rs6721961) and NAMPT (rs61330082) were nominally associated with 28-day mortality. The directions of effect for these nominal associations were in the same direction as previously reported but none of the associations survived correction for multiple hypothesis testing.

CONCLUSIONS

Although our primary analyses failed to statistically validate prior associations, our results provide some support for associations between SNPs in IL6 and NAMPT and risk for development of lung injury and for SNPs in IL8, MBL2, NFE2L2 and NAMPT with severity in ALI outcomes. These associations provide further evidence that genetic factors in genes related to immunity and inflammation contribute to ALI pathogenesis.

BACKGROUND

Host genetic factors are important determinants for risk of HIV-1 infection and disease progression. This study examined associations of host genetic variants and neurocognitive impairment in Chinese individuals infected through contaminated blood products.

METHODS

Two hundred and one HIV-infected patients from Anhui, China, had neuropsychological tests at baseline and 12 months. DNA was genotyped for APOE epsilon2, epsilon3 and epsilon4 alleles; MBL2-A/O; CCR5-wt/Delta32; CCR5-59029-G/A; CCR2-180-G/A; SDF-1-G/A; IL4-589-C/T; MCP-1-2518-A/G; CX3CR1-745-G/A; -849-C/T polymorphisms and CCL3L1 copy number variants using real-time PCR. Univariate and multivariate analyses were performed.

RESULTS

The cohort included 61% men, with mean education 5.5 years, AIDS diagnosis 113 (55%), on antiretrovirals 114 (56%), mean baseline CD4(+) cell count 349 cells/microl and mean log10 RNA 4.09. At baseline, 37% had global neuropsychological impairment increasing to 44% after 12 months. Of 43 patients with the APOE epsilon4 allele, 58% were cognitively impaired compared with 31% without the epsilon4 allele (P = 0.001, odds ratio 3.09, 95% confidence interval 1.54-6.18). The mean global deficit score (GDS) for epsilon4-positive participants on antiretrovirals for 12 months was 0.88 (0.55) compared with 0.63 (0.54) for epsilon4-negative participants (P = 0.053, 95% confidence interval -0.004 to 0.51). For MBL2, 52% of patients with the O/O genotype declined in cognitive function over 12 months compared with 23% with A/A (odds ratio 3.62, 95% confidence interval 1.46-9.03, P = 0.004). No associations were observed for the other genetic variants.

CONCLUSIONS

The APOE epsilon4 allele was associated with increased risk for cognitive deficits, whereas the MBL2 O/O genotype was associated with increased risk for progressive cognitive decline in Chinese individuals infected with HIV through contaminated blood products.

Mannose-binding lectin (MBL) and the ficolins (Ficolin-1, Ficolin-2 and Ficolin-3) are soluble collagen-like proteins that are involved in innate immune defence. They bind sugar structures or acetylated compounds present on microorganisms and on dying host cells and they initiate activation of the lectin complement pathway in varying degrees. Common variant alleles situated both in promoter and structural regions of the human MBL gene (MBL2) influence the stability and the serum concentration of the protein. Although not as thoroughly investigated as the MBL2 gene polymorphisms the ficolin genes (FCNs) also exhibit genetic variations affecting both the serum concentration, stability and binding capacity of the corresponding proteins. Epidemiological studies have suggested that the genetically determined variations in MBL serum concentrations influence the susceptibility to and the course of different types of diseases, while the importance of the ficolins in general and the genetic variation in the FCNs genes in particular is still largely unresolved. This overview will summarize the current molecular knowledge of the human MBL2, FCN1, FCN2 and FCN3 genes.

Mannose binding lectin (MBL) is a central component of the innate immune response and thus may be important for determining hepatitis B virus (HBV) persistence. Since single-nucleotide polymorphisms (SNPs) in the gene encoding MBL (mbl2) alter the level of functional MBL, we hypothesized that mbl2 genotypes are a determinant of HBV persistence or recovery from viral infection. We tested this hypothesis by using a nested case control design with 189 persons with HBV persistence matched to 338 individuals who had naturally recovered from HBV infection. We determined genotypes of two promoter and three exon 1 SNPs in mbl2 and grouped these genotypes according to the amount of functional MBL production. We found that the promoter SNP -221C, which leads to deficient MBL production, was more common in those subjects with viral persistence (odds ratio [OR], 1.38; 95% confidence interval [CI], 1.01 to 1.89; P = 0.04). Those subjects homozygous for the combination of promoter and exon 1 genotypes associated with the highest amount of functional MBL had significantly increased odds of recovery from infection (OR, 0.55; 95% CI, 0.37 to 0.84; P = 0.005). Conversely, those homozygous for the combination of promoter and exon 1 genotypes which produce the lowest amount of functional MBL were more likely to have viral persistence (OR, 1.76; 95% CI, 1.02 to 3.01; P = 0.04). These data are consistent with the hypothesis that functional MBL plays a central role in the pathogenesis of acute hepatitis B.

Mannose-binding lectin (MBL) is a part of the innate immune defense and activates complement via MBL associated serine proteases (MASPs). Human MBL is expressed by hepatocytes, but recent evidence in mice indicates a substantial extra-hepatic transcription. Therefore, we investigated whether mRNA transcribed from the human mbl2 gene as well as the masp genes was present in different tissues. The transcription of human mbl2 is regulated by two alternative promoters (named 0 and 1) where promoter 0 derived transcripts include an additional 5' untranslated part encoded by an extra exon (exon 0). Low extra-hepatic levels of mbl2 mRNA were predominantly found in small intestine and testis tissue, and were quantitatively dominated by promoter 1 transcripts. Moreover, these transcripts varied due to the use of alternative acceptor splice sites positioned inside exon 1. The mRNA distribution of masp1 and masp2 were found very similar to that of mbl2, while masp3 mRNA seemed ubiquitous present at quite high levels when compared to liver. These results indicate that the regulation of mbl2 gene expression in man is more complex than previously anticipated and that local expression of MBL may be relevant in local immune defense, particularly in restricted areas of the gastrointestinal and reproductive tracts.

OBJECTIVE

Identification of the genes responsible for systemic lupus erythematosus (SLE).

METHODS

All the exons and putative promoter regions of 53 candidate genes (TNFRSF6/Fas, TNFSF6/FasL, Fli1, TNFSF10/TRAIL, TNFSF12/TWEAK, Bcl-2, PTEN, FADD, TRADD, CDKN1A, TNFRSF1A/TNFR1, TNFRSF4/OX40, TNFSF4/OX40L, TNFSF5/CD40L, TNFSF13B/BAFF, ICOS, CTLA4, CD28, FYN, G2A, CR2, PTPRC/CD45, CD22, CD19, Lyn, PDCD1, PTPN6, TGFB1, TGFB2, TGFB3, TGFBR1, TGFBR2, TGFBR3, CD3Z, DNASE1, APCS, MERTK, C3, C1QA, C1QB, C1QG, C2, MBL2, IGHM, IL-2, IL-4, IL-10, IFNG, TNFA, MAN2A1, TNFRSF11A/RANK, TNFRSF11B/OPG, TNFSF11/OPGL) were screened for single nucleotide polymorphisms (SNPs) and their association with SLE was assessed by case-control studies. A total of 509 cases and 964 controls of Japanese descent were enrolled.

RESULTS

A total of 316 SNPs was identified. When analysed in the Japanese population, the allele frequencies of T at rs7951 and G at rs2230201 of the C3 gene were 0.110 and 0.626, respectively, in SLE patients; significantly higher than the frequencies of 0.081 and 0.584, respectively, in controls [odds ratio (OR) = 1.40, 95% confidence interval (CI) = 1.05-1.86, P = 0.016 and OR=1.19, 95% CI = 1.01-1.41, P = 0.038, respectively]. The mean serum C3 level of carriers of the rs7951 T allele was significantly lower than that of non-carriers of the T allele in 87 SLE patients whose medical records were available (P = 0.0018).

CONCLUSIONS

rs7951 T allele of the C3 gene was significantly associated with SLE, and decreased serum level of C3 seems to be correlated with this allele.

BACKGROUND

Visceral leishmaniasis (VL) is almost always lethal if not treated, but most infections with the causative agents are clinically silent. Mannan-binding lectin (MBL), an opsonin, is a candidate molecule for modifying progression to VL because it may enhance infection with intracellular pathogens. Mutations in the MBL2 gene decrease levels of MBL and may protect against development of VL. This case-control study examines genotypes of MBL2 and levels of MBL in individuals presenting with different outcomes of infection with Leishmania chagasi.

METHODS

Genotypes for MBL2 and levels of serum MBL were determined in uninfected control subjects (n=76) and in individuals presenting with asymptomatic infection (n=90) or VL (n=69).

RESULTS

Genotypes resulting in high levels of MBL were more frequent (odds ratio [OR], 2.5 [95% confidence interval [CI], 1.3-5.0]; P=.006) among individuals with VL than among those with asymptomatic infections and were even more frequent (OR, 3.97 [95% CI, 1.10-14.38]; P=.043) among cases of VL presenting with clinical complications than among those with uneventful courses. Serum levels of MBL were higher (P=.011) in individuals with VL than in asymptomatic infections .

CONCLUSIONS

Genotypes of the MBL2 gene predict the risk for developing VL and clinical complications in infections with L. chagasi.

Mannose Binding Lectin (MBL) is a liver derived, circulating plasma protein that plays a pivotal role in innate immunity. MBL functions as a pathogen recognition molecule, opsonising organisms and initiating the complement cascade. MBL deficiency arising from mutations and promoter polymorphisms in the MBL2 gene is common and has been associated with risk, severity, and frequency of infection in a number of clinical settings. With MBL therapy on the horizon, the usefulness of replacement MBL therapy has been challenged by the notion, that as an acute phase protein, MBL levels may rise under stress to sufficient levels, in individuals who are usually deficient. This report demonstrates that in patients with sepsis and septic shock, the majority of patients do not display an MBL acute phase response: 41.4% of individuals maintained consistent MBL levels throughout hospital stay, 31.3% of individuals demonstrated a positive acute phase response, and a negative acute phase response was observed in 27.3% of individuals studied. Importantly, a positive acute phase response was generally observed in individuals with wild-type MBL2 genes. When a positive acute phase response was observed in individuals with coding mutation, these individuals demonstrated a normal MBL level on admission to hospital. Furthermore, no individual, regardless of genotype who was MBL deficient at admission was able to demonstrate a positive acute phase response into the normal MBL range. These findings indicate MBL demonstrates a variable acute phase response in the clinical setting of sepsis and septic shock.

OBJECTIVE

To evaluate associations between polymorphisms in the gene coding for mannose-binding lectin (MBL) and the diagnosis of acute or recurrent vulvovaginal candidiasis and bacterial vaginosis

METHODS

Women at two outpatient clinics in Brazil filled out a questionnaire and were examined for the presence of vulvovaginal candidiasis or bacterial vaginosis. A buccal swab was blindly tested for codons 54 and 57 MBL2 gene polymorphisms by polymerase chain reaction and endonuclease digestion.

RESULTS

A total of 177 women were enrolled. Vulvovaginal candidiasis was identified in 78 (44.1%) women, 33 (18.6%) had bacterial vaginosis, and 66 (37.3%) were normal controls. Recurrent vulvovaginal candidiasis was present in 50 (64.1%) of the women with vulvovaginal candidiasis; 20 (60.6%) of the bacterial vaginosis patients had recurrent disease. Vulvovaginal candidiasis was associated with white race (P=.007), bacterial vaginosis was associated with nonwhite race (P=.05), and both were associated with a history of allergy (P< or =.02) and having sexual intercourse at least three times a week (P<.001). Carriage of the variant MBL2 codon 54 allele B was more frequent in women with recurrent vulvovaginal candidiasis (25.0%) than in the women with acute vulvovaginal candidiasis (17.9%) or controls (10.6%) (P=.004). Allele B was also more prevalent in women with recurrent bacterial vaginosis (22.5%) than in those with acute bacterial vaginosis (0%) (P=.009). The MBL2 codon 57 polymorphism was infrequent and not associated with vulvovaginal candidiasis or bacterial vaginosis.

CONCLUSIONS

The incidence of vulvovaginal candidiasis and bacterial vaginosis differs by ethnicity in Brazilian women. The MBL2 codon 54 gene polymorphism is associated with both recurrent vulvovaginal candidiasis and recurrent bacterial vaginosis.

BACKGROUND

The relationship among chronic inflammation, innate immunity, and cancer is well established. Mannose-binding lectin (MBL) is a key player in innate immunity. Five polymorphisms in the promoter and first exon of the MBL2 gene alter the expression and function of MBL in humans and are associated with inflammation-related disease susceptibility. These five polymorphisms create six well-characterized haplotypes that result in lower (i.e., LYB, LYC, HYD, and LXA) or higher (i.e., HYA and LYA) serum MBL concentrations. We investigated whether survival of patients with lung cancer was associated with these polymorphisms.

METHODS

We used a multivariable Cox proportional hazards model to study the association between MBL2 polymorphisms and their haplotypes and diplotypes in 558 white and 173 African American patients with non-small-cell lung cancer in the Baltimore, MD, area and lung cancer mortality. Smoking history and race were obtained from interviews, tumor stage was obtained from medical records, and cause of death was obtained from the National Death Index. All statistical tests were two-sided.

RESULTS

We found a statistically significant association between the X allele of the promoter Y/X polymorphism (which results in a lower serum MBL concentration) and improved lung cancer survival among white patients (risk ratio [RR] of death from lung cancer with X/X or X/Y genotype compared with Y/Y genotype = 0.61, 95% confidence interval [CI] = 0.46 to 0.81) but not among African American patients (RR = 1.11, 95% CI = 0.69 to 1.77). The associations among white patients were strongest in heavy smokers and were independent of stage. We also found a statistically significant interaction between the Y/X polymorphism and race for lung cancer survival (P(interaction) = .019). The MBL2 LXA haplotype and XA/B diplotype, which are also associated with low serum MBL levels, were statistically significantly associated with improved lung cancer survival among white patients.

CONCLUSIONS

The functional Y/X polymorphism of the innate-immunity gene MBL2 and MBL2 haplotypes and diplotypes appear to be associated with lung cancer survival among white patients.

Dengue disease can clinically evolve from an asymptomatic and mild disease, known as dengue fever (DF), to a severe disease known as dengue hemorrhagic fever (DHF). Recent evidence has shown how host genetic factors can be correlated with severe dengue susceptibility or protection. Many of these genes, such as CD209, TNF-a, vitamin D receptor, and FC gamma receptor IIA, are components of the innate immune system, suggesting that innate responses might have a role in dengue pathogenesis. MBL2 gene polymorphisms have been shown to modulate susceptibility or protection in many viral diseases. We investigated the involvement of MBL2 gene in the dengue clinical outcome through the analysis of MBL2 exon 1 polymorphisms (at codons 52, 54, and 57) known to be associated with reduced serum levels of the MBL protein. The genotypes of 110 well-characterized dengue-positive patients were statistically analyzed to establish possible correlations between MBL2 polymorphisms and parameters such as sex, type of infection (primary or secondary response), race/ethnicity, course of infection, and age. We found significant correlations between wild-type AA MBL2 genotype and age as associated risk factors for development of dengue-related thrombocytopenia.

BACKGROUND

There is increasing evidence that mannose-binding lectin (MBL) has a complex role in many diseases, particularly in infectious diseases. However, the relationship between MBL deficiency and cryptococcal meningitis has not been clarified. The purpose of this study was to investigate the correlation between MBL polymorphism and non-HIV cryptococcal meningitis.

METHODS

A case-controlled genetic association study was conducted. Patients with cryptococcal meningitis and control subjects were genotyped for 6 alleles of MBL2 gene (H/L, Y/X, P/Q, A/D, A/B, and A/C). The distributions in allele frequency, genotypes, haplotypes, and genotype groups were compared between patients and control subjects.

RESULTS

Study participants included 103 HIV-uninfected patients with cryptococcal meningitis and 208 healthy control subjects, all of Chinese Han ethnicity. The homozygous mutative genotypes (O/O) of the coding region were associated with cryptococcal meningitis (P = .023; odds ratio [OR], 4.29; 95% confidence interval [CI], 1.11-19.88), the correlation more overt in immunocompetent patients (P = .005; OR, 6.65; 95% CI, 1.49-33.05). MBL-deficient participant group was associated with cryptococcal meningitis (P = .039; OR, 2.09; 95% CI, .96-4.51), particularly in immunocompetent patients (P = .028; OR, 2.51; 95% CI, .96-6.22).

CONCLUSIONS

This is the first to show genotypes coding for MBL deficiency are associated with cryptococcal meningitis in nonimmunocompromised hosts.

OBJECTIVE

Mannose-binding lectin (MBL) is a pattern-recognition receptor that activates complement and modulates inflammation. Homozygosity for the most common allele of the MBL2 gene that is associated with high MBL serum concentrations is more prevalent among patients with pre-eclampsia. The objective of this study was to determine maternal plasma MBL concentrations in normal pregnant women and patients with pre-eclampsia.

METHODS

This cross-sectional study included normal pregnant women (n = 187) and patients with pre-eclampsia (n = 99). Maternal plasma MBL concentrations were determined by ELISA.

RESULTS

Women with pre-eclampsia had a higher median maternal plasma MBL concentration than normal pregnant women. MBL concentration distribution curves were three-modal, the subintervals in normal pregnancy were low (< 143.7), intermediate (143.7-1898.9) and high >> 1898.9 ng/mL). The proportion of normal pregnant women was larger in the low subinterval, while the proportion of patients with preeclampsia was larger in the high subinterval (P = 0.02). Normal pregnant women in the high subinterval had a larger rate of placental underperfusion than those in the low and intermediate subintervals (P = 0.02).

CONCLUSIONS

The median maternal plasma MBL concentration is elevated in patients with pre-eclampsia and a larger proportion of these patients are in the high subinterval than normal pregnant women, suggesting that this component of the innate immune system is involved in the mechanisms of disease in pre-eclampsia.

Mannose-binding lectin (MBL) is an innate immune system pattern recognition molecule that kills a wide range of pathogens via the lectin complement pathway. MBL deficiency is associated with severe infection but the best measure of this deficiency is undecided. We investigated the influence of MBL functional deficiency on the development of sepsis in 195 adult patients, 166 of whom had bloodstream infection and 35 had pneumonia. Results were compared with 236 blood donor controls. MBL function (C4b deposition) and levels were measured by enzyme-linked immunosorbent assay. Using receiver-operator characteristics of MBL function in healthy controls, we identified a level of <0.2 U microL(-1) as a highly discriminative marker of low MBL2 genotypes. Median MBL function was lower in sepsis patients (0.18 U microL(-1)) than in controls (0.48 U microL(-1), P<0.001). MBL functional deficiency was more common in sepsis patients than controls (P<0.001). MBL functional deficient patients had significantly higher sequential organ failure assessment (SOFA) scores and higher MBL function and levels were found in patients with SOFA scores predictive of good outcome. Deficiency of MBL function appears to be associated with bloodstream infection and the development of septic shock. High MBL levels may be protective against severe sepsis.

OBJECTIVE

The Mannan-binding lectin (MBL) pathway involves recognition of fungal surfaces by MBL and cleavage of C2 and C4 by MBL-associated serine protease (namely, MASP-2). Recent data show that MBL pathway deficiency might result not only from polymorphisms of the MBL2 gene but also of MASP2. The aim of the study was to assess whether polymorphisms of these genes are associated with invasive fungal infections (IFIs) following allogeneic stem cell transplantation (allo-SCT).

METHODS

The promoter and the exon 1 of MBL2 and the exon 3 of MASP2 were sequenced in 106 donor-recipient pairs from HLA-identical sibling allo-SCTs performed in a single institution.

RESULTS

Ten percent of the donors and 11% of the recipients carried the MBL-low (O/O, LXA/O) genotypes; 7% of the donors and 3% of the recipients were heterozygous for the MASP2 Asp105Gly variant. Factors associated with a higher probability of IFIs were donor's MBL-low genotype (38% vs 12%, p = 0.01), recipient's MASP2 variant (67% vs 14%, p = 0.01), and acute graft-versus-host disease (GVHD) grades II to IV (27% vs 11%, p = 0.04); in the multivariate analysis MBL-low genotype (relative risk [RR] 7.3, p = 0.003), MASP2 variant (RR 6.4, p = 0.002), and acute GVHD II to IV (RR 3.8, p = 0.02) retained independent prognostic value.

CONCLUSIONS

These results show for the first time that polymorphisms responsible for not only MBL but also MASP-2 deficiency are independent predictive factors for IFI after allo-SCT.

The mannose-binding lectin 2 (MBL2) gene is polymorphic and codes for a protein with an important role in the innate immune response, whose variants have been associated with a great number of diseases. Point variations have been described in the 5' regulatory region at positions -550 (MBL2*H or *L) and -221 (*X or *Y), in the 5' untranslated sequence at position +4 (*P or *Q), and in the coding sequence of exon 1 at codons 52, 54, and 57 (MBL2*A or D, A or B, and A or C, respectively). These can be in cis or in trans configuration. The different haplotypes influence the immunological phenotype of the individual, which makes MBL2 haplotyping very important. Previously described MBL2-typing methods do not present adequate haplotype resolution or are too complex and costly. We have developed a new MBL2-typing strategy that is economical and renders rapid and reliable results without ambiguities. We typed 202 individuals of European, 32 of African, and 16 of Oriental descent. Only five to six reactions from 10 possible PCR-SSPs (sequence-specific polymerase chain reactions) were sufficient to genotype one individual unambiguously. The reactions were specific for amplification of the variants located upstream of the coding sequence. The results were associated to the results of hybridizations of the amplified products with eight sequence-specific oligonucleotide probes (SSOP). The strategy led to identification of eight alleles: MBL2*HYPA, HYPD, LYPA, LYPB, LYPD, LYQA, LYQC, and LXPA. Their frequencies in each of the groups were similar to those of other populations studied to date, with MBL2*LYPD (g.[-550G>C; -221C>G; 4T>C; 223C>T; 230A>G; 239A>G]) being novel. All samples were found to be in Hardy-Weinberg equilibrium.

Mannose-binding lectin (MBL) is a pattern recognition receptor of the complement system and plays an important role in innate immunity. Whether or not MBL acts as an acute-phase response protein in infection has been an issue of extensive debate, because MBL responses have shown a high degree of heterogeneity. Single nucleotide polymorphisms (SNPs) in the promoter (wild-type Y versus X) and exon 1 (A versus 0) of the MBL2 gene can lead to MBL deficiency. This study investigated the influence of SNPs in the promoter and exon 1 of the MBL2 gene on the acute-phase responsiveness of MBL in 143 patients with community-acquired pneumonia. Acute-phase reactivity was observed only in MBL-sufficient genotypes (YA/YA, XA/YA, XA/XA and YA/0). In patients with wild-type exon 1 genotype A/A, positive acute-phase responses were associated with the presence of the YA haplotype and negative responses with its absence. Genotypes YA/0 and XA/XA produced equal levels of MBL in convalescence. In the acute phase, however, patients with genotype XA/XA displayed negative acute-phase responses more often than those with genotype YA/0. Correlation of MBL and C-reactive protein levels in the acute phase of pneumonia also depended upon the MBL2 genotype. In conclusion, acute-phase responsiveness of MBL was highly dependent upon the MBL2 genotype. These data suggest that heterogeneity in protein responses in the acute phase of disease should always be viewed in the light of possible influences of genetic differences in both structural and regulatory parts of the gene.

Infection frequently causes exacerbations of chronic obstructive pulmonary disease (COPD). Mannose-binding lectin (MBL) is a pattern-recognition receptor that assists in clearing microorganisms. Polymorphisms in the MBL2 gene reduce serum MBL levels and are associated with risk of infection. We studied whether the MBL2 codon 54 B allele affected serum MBL levels, admissions for infective exacerbation in COPD and disease susceptibility. Polymorphism frequency was determined by PCR-RFLP in 200 COPD patients and 104 smokers with normal lung function. Serum MBL was measured as mannan-binding activity in a subgroup of 82 stable COPD patients. Frequency of COPD admissions for infective exacerbation was ascertained for a 2-year period. The MBL2 codon 54 B allele reduced serum MBL in COPD patients. In keeping, patients carrying the low MBL-producing B allele had increased risk of admission for infective exacerbation (OR 4.9, P(corrected)=0.011). No association of MBL2 genotype with susceptibility to COPD was detected. In COPD, serum MBL is regulated by polymorphism at codon 54 in its encoding gene. Low MBL-producing genotypes were associated with more frequent admissions to hospital with respiratory infection, suggesting that the MBL2 gene is disease-modifying in COPD. MBL2 genotype should be explored prospectively as a prognostic marker for infection risk in COPD.

In this paper we explore the use of biological knowledge to supplement statistical analysis in identifying genes associated with disease. It has been previously found that the 402H variant in complement factor H (CFH) is associated with risk for developing age related macular degeneration (AMD). By focusing on the single nucleotide polymorphisms (SNPs) in the complement pathway, we were able to use the genotype data from a recently published AMD genome wide association study to identify two additional genes, C7 and MBL2, as potentially associated with subtypes of AMD. Two SNPs situated in introns of C7 and MBL2 could help differentiate between two forms of AMD: wet (more severe form of AMD) and dry (milder form of AMD). We identified a C7 haplotype associated with protection against developing wet AMD among individuals with homozygous CFH risk allele 402H (p-value 0.001 for wet AMD versus dry AMD, odds ratio (OR) 0.16, OR 95% CI 0.05-0.49) as well as among individuals with at least one CFH risk allele (p-value 0.007 for wet AMD versus dry AMD, OR 0.35, OR 95% CI 0.16-0.77). The fact that the statistical scores for the C7 and MBL2 SNPs were significant (low false discovery rate) at the pathway level, but not significant at the genome level suggests that focusing at the pathway level can be beneficial for identifying SNP signals that would be lost at the genome-wide level.