Polymorphism in the promoter region of the mannose-binding lectin gene among human T-cell lymphotropic virus infected subjects

ABSTRACT: The present study investigated the frequency of the mutations at positions -550 and -221 of the mannose-binding lectin (MBL) gene in a sample of 75 human T-cell lymphotropic virus (HTLV) infected patients and 96 HTLV seronegative controls, in order to evaluate the occurrence of a possible association between the polymorphism and HTLV infection. A sequence specific primer-polymerase chain reaction was used for discrimination of the polymorphism. The analysis of allele frequencies at position -550 did not show any significant differences between HTLV infected group and controls, but there was a significant difference at position -221. The comparative analysis of haplotypes frequencies were not significant, but the genotype frequencies between the two groups, revealed a higher prevalence of genotype LYLX (25.3%), associated with medium and low MBL serum levels among HTLV infected subjects. The odds ratio estimation demonstrated that the presence of genotype LYLX was associated with an increased risk of HTLV infection (p = 0.0096; 1.38 < IC95% < 7.7605). There was no association between proviral load and the promoter polymorphism, but when promoter and exon 1 mutations were matched, it was possible to identify a significant higher proviral load among HTLV infected individuals carrying haplotypes correlated to low serum levels of MBL. The present study shows that the polymorphism in the promoter region of the MBL gene may be a genetic marker associated with HTLV infection, and emphasizes the need for further studies to determinate if the present polymorphism have any impact on diseases linked to HTLV infection.

Investigação do polimorfismo do exon - 1 do gene MBL (Mannose-Binding Lectin) em pacientes portadores de tuberculose

A lectina ligante de manose (MBL) é uma proteína considerada de fase aguda com importante papel na primeira linha de defesa do sistema imune inato, cujos níveis séricos são determinados geneticamente. A MBL ativa a via da lectina do complemento, além de mediar a opsonização e fagocitose de microrganismos. Vários estudos associam os níveis séricos de MBL à suscetibilidade ou resistência a agentes infecciosos entre eles o Mycobacterium tuberculosis, agente causador da tuberculose humana. Neste estudo, com o objetivo de avaliar a ocorrência de uma possível associação entre os polimorfismos e a tuberculose, avaliamos as freqüências das mutações no éxon 1 do gene MBL em um grupo de 167 pacientes com tuberculose, subdivididos em 3 grupos: pacientes com tuberculose pulmonar, pacientes com tuberculose extrapulmonar, pacientes com tuberculose multirresistente a drogas, e grupo controle com 159 profissionais da saúde, negativos para tuberculose. A identificação dos alelos MBL *A, *B, *C e *D foi realizada por meio da reação em cadeia da polimerase, utilizando seqüências de iniciadores específicos e posterior digestão enzimática. As análises das freqüências alélicas e genotípicas do éxon 1 não mostraram qualquer diferença significativa entre pacientes com tuberculose e grupo controle (p>0,05). Não foram observadas associações significativas entre os grupos de tuberculose pulmonar, extrapulmonar e tuberculose multirresistente a drogas, quando relacionados entre si e ao grupo controle. Os dados obtidos em nosso estudo não demonstraram evidencias de qualquer influência das variações do éxon 1 do gene MBL na tuberculose ativa, sugerindo que os polimorfismos nessa região do gene não tem nenhuma influencia na susceptibilidade à tuberculose.

Investigação dos polimorfismos no éxon 1 do gene MBL (Mannose-Binding Lectin) e sua associação com a síndrome da imunodeficiência adquirida (AIDS)

No presente estudo foram investigadas as freqüências das mutações no éxon 1 do gene MBL em um grupo de 128 pacientes com Aids, 116 portadores assintomáticos da infecção pelo HIV-1, 84 mulheres soronegativas profissionais do sexo, com comportamentos de alto risco e 99 indivíduos controles soronegativos, com o objetivo de avaliar a ocorrência de uma possível associação entre os polimorfismos neste gene e a infecção pelo HIV-1. A identificação dos alelos MBL *A, *B, *C e *D foi realizada por meio da reação em cadeia mediada pela polimerase, utilizando sequências de iniciadores específicos e posterior digestão enzimática (RFLP). As análises das frequências alélicas e genotípicas do éxon 1 não mostraram qualquer diferença significativa entre pacientes soropositivos (assintomáticos e Aids) e soronegativos (controle e controle de alto risco) (p>0,05). Não foram observadas associações significativas entre a presença de co-infecções e as variantes alélicas. Entretanto, tuberculose, neurotoxoplasmose, candidíase, neurocriptococose e pneumonia foram as co-infecções com maior prevalência. As associações entre o número de linfócitos TCD4+, a carga viral plasmática e os polimorfismos no éxon 1 do gene MBL nos pacientes com Aids e portadores assintomáticos não foram estatisticamente significante. Desse modo, pode-se sugerir a ausência de associação entre estes polimorfismos e a susceptibilidade à infecção pelo HIV-1, destacando a necessidade de estudos adicionais para determinar se estes polimorfismos apresentam qualquer impacto associado à infecção ou a progressão para a Aids.

Polimorfismo da região promotora do gene MBL (Mannose-Binding Lectin) e o seu impacto na infecção pelo Vírus da imunodeficiência humana 1 (HIV-1) e na progressão da SIDA/AIDS

Um emergente interesse à MBL tem surgido, devido a sua importância no sistema imune inato. Recentes estudos relatam uma influência do polimorfismo na região promotora nas regiões -550 (H/L) e -221 (X/Y) do gene MBL, com a deficiência do sistema imune à determinados patógenos. O objetivo do presente estudo é investigar a associação entre o polimorfismo na região promotora do gene MBL e a infecção pelo HIV-1e a progressão à SIDA/AIDS. No estudo foi feita identificação destes alelos em uma população de 127 pacientes soropositivos para HIV-1 e em 97 indivíduos soronegativos, a partir da técnica de SSP-PCR, utilizando-se seqüências de iniciadores específicos para cada variante. A evolução da infecção nos pacientes soropositivos foi avaliada por meio da contagem de linfócito T CD4⁺ e da carga viral plasmática. As distribuições nas freqüências alélicas e haplotípicas entre os grupos de portadores do HIV-1 e nos controles soronegativos não apresentaram diferenças estatisticamente significantes (p>0,05). Entretanto, pacientes soropostivos portadores do haplótipo HY apresentaram uma maior contagem e uma evolução significativa no número de linfócitos T CD4⁺; e uma menor contagem e maior redução da carga viral plasmática, em relação aos pacientes portadores dos haplótipos LY, LX e HX. Os resultados do presente estudo mostram que a presença de haplótipos relacionados a médios e baixos níveis séricos de MBL podem ter um papel direto na forma como o paciente soropositivo evolui laboratorialmente. Desse modo, conclui-se que a caracterização dos haplótipos da região promotora do gene MBL em portadores da infecção pelo HIV-1 pode ser importante na avaliação do prognóstico de evolução da SIDA/AIDS.

Mannose-binding lectin gene polymorphism and risk factors for cardiovascular disease in postmenopausal women

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Association between mannose-binding lectin and interleukin-1 receptor antagonist gene polymorphisms and recurrent vulvovaginal candidiasis

Objective The influence of functional polymorphisms in the genes coding for mannose-binding lectin (MBL) and interleukin-1 receptor antagonist (IL-1ra) on recurrent vulvovaginal candidiasis (RVVC) were examined in an urban Brazilian population. Methods DNA was isolated from buccal swabs of 100 women with RVVC and 100 control women and tested by gene amplification for a single nucleotide polymorphism in codon 54 of the MBL2 gene and for a length polymorphism in intron 2 of the IL1RN gene. Genotype and allele frequencies were compared between groups. Results The frequency of the variant MBL2 B allele, associated with reduced circulating and vaginal MBL concentrations, was 27.0% in RVVC and 8.5% in control women (p < .0001). The MBL2 B, B genotype was present in 12% of RVVC patients and 1% of controls (p = .0025). The IL1RN 2 allele frequency, associated with the highest level of unopposed IL-1 beta activity, was 24.0% in RVVC and 23.4% in controls. The IL1RN genotype distribution was also similar in both groups. Conclusion Carriage of the MBL2 codon 54 polymorphism, but not the IL1RN length polymorphism, predisposes to RVVC in Brazilian women.

Deficiency of mannose-binding lectin-associated serine protease-2 associated with increased risk of fever and neutropenia in pediatric cancer patients

BACKGROUND: Mannose-binding lectin-associated serine protease-2 (MASP-2) is an essential component of the lectin pathway of complement activation. MASP-2 deficiency is common because of genetic polymorphisms, but its impact on susceptibility to infection is largely unknown. The aim of the present study was to determine whether children with cancer and MASP-2 deficiency develop more frequent or more severe episodes of fever and severe chemotherapy-induced neutropenia (FN). METHODS: Serum MASP-2 was measured by enzyme-linked immunosorbent assay at the time of diagnosis in children treated with chemotherapy for cancer. Association of FN episodes with MASP-2 concentration was analyzed using Poisson regression accounting for chemotherapy intensity and duration. RESULTS: Median MASP-2 in 94 children was 527 ng/mL (interquartile range, 367-686). Nine (10%) children had MASP-2 deficiency (<200 ng/mL). During a cumulative chemotherapy exposure time of 82 years, 177 FN episodes were recorded. MASP-2 deficient children had a significantly increased risk of developing FN (multivariate risk ratio, 2.08; 95% confidence interval, 1.31-3.21; P = 0.002), translating into significantly prolonged cumulative duration of hospitalization and of intravenous antimicrobial therapy. They experienced significantly more episodes of FN without a microbiologically defined etiology, and there was a trend toward more frequent episodes of FN with bacteremia. CONCLUSION: In this study, MASP-2 deficiency was associated with an increased risk of FN in children treated with chemotherapy for cancer. MASP-2 deficiency represents a novel risk factor for chemotherapy-related infections.

Variants in the Mannose-binding Lectin Gene MBL2 do not Associate With Sepsis Susceptibility or Survival in a Large European Cohort.

BACKGROUND  Sepsis is an increasingly common condition, which continues to be associated with unacceptably high mortality. A large number of association studies have investigated susceptibility to, or mortality from, sepsis for variants in the functionally important immune-related gene MBL2. These studies have largely been underpowered and contradictory. METHODS  We genotyped and analyzed 4 important MBL2 single nucleotide polymorphisms (SNPs; rs5030737, rs1800450, rs1800451, and rs7096206) in 1839 European community-acquired pneumonia (CAP) and peritonitis sepsis cases, and 477 controls from the United Kingdom. We analyzed the following predefined subgroups and outcomes: 28-day and 6 month mortality from sepsis due to CAP or peritonitis combined, 28-day mortality from CAP sepsis, peritonitis sepsis, pneumococcal sepsis or sepsis in younger patients, and susceptibility to CAP sepsis or pneumococcal sepsis in the United Kingdom. RESULTS  There were no significant associations (all P-values were greater than .05 after correction for multiple testing) between MBL2 genotypes and any of our predefined analyses. CONCLUSIONS  In this large, well-defined cohort of immune competent adult patients, no associations between MBL2 genotype and sepsis susceptibility or outcome were identified.

Mannose-binding lectin gene polymorphism predicts hospital admissions for COPD infections

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.

Mannan-binding lectin deficiency results in unusual antibody production and excessive experimental colitis in response to mannose-expressing mild gut pathogens

In Crohn's disease (CD) the deficiency of mannan-binding lectin (MBL) is associated with an increased prevalence of anti-Saccharomyces cerevisiae antibodies (ASCA) and with complicated phenotypes of the disease. However, the role of MBL in intestinal inflammation is currently unclear. A study was undertaken to analyse local MBL expression in human intestine and the consequences of MBL deficiency in experimental colitis and yeast infection.

Crystal structure of a beta-prism II lectin from Remusatia vivipara

The crystal structure of a beta-prism II (BP2) fold lectin from Remusatia vivipara, a plant of traditional medicinal value, has been determined at a resolution of 2.4 A. This lectin (RVL, Remusatia vivipara lectin) is a dimer with each protomer having two distinct BP2 domains without a linker between them. It belongs to the ``monocot mannose-binding'' lectin family, which consists of proteins of high sequence and structural similarity. Though the overall tertiary structure is similar to that of lectins from snowdrop bulbs and garlic, crucial differences in the mannose-binding regions and oligomerization were observed. Unlike most of the other structurally known proteins in this family, only one of the three carbohydrate recognition sites (CRSs) per BP2 domain is found to be conserved. RVL does not recognize simple mannose moieties. RVL binds to only N-linked complex glycans like those present on the gp120 envelope glycoprotein of HIV and mannosylated blood proteins like fetuin, but not to simple mannose moieties. The molecular basis for these features and their possible functional implications to understand the different levels of carbohydrate affinities in this structural family have been investigated through structure analysis, modeling and binding studies. Apart from being the first structure of a lectin to be reported from the Araceae/Arum family, this protein also displays a novel mode of oligomerization among BP2 lectins.

The Role of Nanometer-Scaled Ligand Patterns in Polyvalent Binding by Large Mannan-Binding Lectin Oligomers

Mannan-binding lectin (MBL) is an important protein of the innate immune system and protects the body against infection through opsonization and activation of the complement system on surfaces with an appropriate presentation of carbohydrate ligands. The quaternary structure of human MBL is built from oligomerization of structural units into polydisperse complexes typically with three to eight structural units, each containing three lectin domains. Insight into the connection between the structure and ligand-binding properties of these oligomers has been lacking. In this article, we present an analysis of the binding to neoglycoprotein-coated surfaces by size-fractionated human MBL oligomers studied with small-angle x-ray scattering and surface plasmon resonance spectroscopy. The MBL oligomers bound to these surfaces mainly in two modes, with dissociation constants in the micro to nanomolar order. The binding kinetics were markedly influenced by both the density of ligands and the number of ligand-binding domains in the oligomers. These findings demonstrated that the MBL-binding kinetics are critically dependent on structural characteristics on the nanometer scale, both with regard to the dimensions of the oligomer, as well as the ligand presentation on surfaces. Therefore, our work suggested that the surface binding of MBL involves recognition of patterns with dimensions on the order of 10-20 nm. The recent understanding that the surfaces of many microbes are organized with structural features on the nanometer scale suggests that these properties of MBL ligand recognition potentially constitute an important part of the pattern-recognition ability of these polyvalent oligomers. The Journal of Immunology, 2012, 188: 1292-1306.