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

Mannose-binding lectin gene polymorphism and the susceptibility of sepsis: A meta-analysis

Objective

To assess the association between the Mannose-binding lectin (MBL) gene polymorphism and the susceptibility to sepsis using a meta-analysis.

Methods

The publications were searched on PubMed, Embase, and Web of Science databases up to December 1, 2019 for relevant literature.

Results

A total of 32 studies (21 adult and 11 pediatric studies) were selected for analysis. Overall, in the three models of MBL +54 A/B gene polymorphisms, namely the dominant model BB + AB vs. AA ( p = 0.03), the recessive model BB vs. AB + AA ( p < 0.00001), and the allele model B vs. A ( p = 0.04), MBL +54 A/B was significantly related to the risk of sepsis. In the adult group, the MBL A/O gene polymorphism was associated with the risk of sepsis in the dominant model AO + OO vs. AA ( p = 0.006) as well as in the allele model O vs. A ( p = 0.04). The MBL +54 A/B gene polymorphism was significantly related to the risk of sepsis in the recessive model and, therefore, may increase the risk of sepsis. In the pediatric group, no polymorphic loci were significantly associated with sepsis in any of the three models. The results of the publication bias test demonstrated no publication bias in an unadjusted estimate of the relationship between MBL A/O and −211Y/X gene polymorphism and sepsis.

Conclusions

The polymorphisms of MBL that are related to the occurrence of sepsis are primarily A/O and +54 A/B, while −221Y/X and −550H/L have no clear relationship with the susceptibility of sepsis in various age groups or different models.

Components of the Lectin Pathway of Complement in Haematologic Malignancies

The complement system is activated cascadically via three distinct major routes: classical pathway (CP), alternative pathway (AP) or lectin pathway (LP). The unique factors associated with the latter are collectins (mannose-binding lectin, collectin-10, collectin-11), ficolins (ficolin-1, ficolin-2, ficolin-3) and proteins of the mannose-binding lectin-associated serine protease (MASP) family (MASP-1, MASP-2, MASP-3, MAp19, MAp44). Collectins and ficolins are both pattern-recognising molecules (PRM), reactive against pathogen-associated molecular patterns (PAMP) or danger-associated molecular patterns (DAMP). The MASP family proteins were first discovered as complexes with mannose-binding lectin (MBL) and therefore named MBL-associated serine proteases, but later, they were found to interact with ficolins, and later still, collectin-10 and collectin-11. As well as proteolytic enzymes (MASP-1, MASP-2, MASP-3), the group includes non-enzymatic factors (MAp19, MAp44). In this review, the association-specific factors of the lectin pathway with haematologic malignancies and related infections are discussed.

Applying whole-genome sequencing in relation to phenotype and outcomes in siblings with cystic fibrosis

Variations in disease onset and/or severity have often been observed in siblings with cystic fibrosis (CF), despite the same CFTR genotype and environment. We postulated that genomic variation (modifier and/or pharmacogenomic variants) might explain these clinical discordances. From a cohort of patients included in the Wisconsin randomized clinical trial (RCT) of newborn screening (NBS) for CF, we identified two brothers who showed discordant lung disease courses as children, with one milder and the other more severe than average, and a third, eldest brother, who also has severe lung disease. Leukocytes were harvested as the source of DNA, and whole-genome sequencing (WGS) was performed. Variants were identified and analyzed using in-house-developed informatics tools. Lung disease onset and severity were quantitatively different between brothers during childhood. The youngest, less severely affected brother is homozygous for HFE p.H63D. He also has a very rare PLG p.D238N variant that may influence host-pathogen interaction during chronic lung infection. Other variants of interest were found differentially between the siblings. Pharmacogenomics findings were consistent with the middle, most severely affected brother having poor outcomes to common CF treatments. We conclude that genomic variation between siblings with CF is expected. Variable lung disease severity may be associated with differences acting as genetic modifiers and/or pharmacogenomic factors, but large cohort studies are needed to assess this hypothesis.

Low pre-transplant levels of mannose-binding lectin are associated with viral infections and mortality after haematopoietic allogeneic stem cell transplantation

BACKGROUND

Mannose-binding lectin (MBL) is a key component of innate immunity. Low serum MBL levels, related to promoter polymorphism and structural variants, have been associated with an increased risk of infection. The aim of this work was to analyse the incidence and severity of infections and mortality in relation to the MBL2 genotype and MBL levels in patients underwent allogeneic haematopoietic stem cell transplantation (Allo-HSCT).

RESULTS

This was a prospective cohort study of 72 consecutive patients underwent Allo-HSCT between January 2007 and June 2009 in a tertiary referral centre. Three periods were considered in the patients' follow-up: the early period (0-30 days after Allo-HSCT), the intermediate period (30-100 days after Allo-HSCT) and the late period (> 100 days after Allo-HSCT). A commercial line probe assay for MBL2 genotyping and an ELISA Kit were used to measure MBL levels. A total of 220 episodes of infection were collected in the 72 patients. No association between donor or recipient MBL2 genotype and infection was found. The first episode of infection presented earlier in patients with pre-transplant MBL levels of < 1000 ng/ml (median 6d vs 8d, p = 0.036). MBL levels < 1000 ng/ml in the pre-transplant period (risk ratio (RR) 2.48, 95% CI 1.00-6.13), neutropenic period (0-30 days, RR 3.28, 95% CI 1.53-7.06) and intermediate period (30-100 days, RR 2.37, 95% CI 1.15-4.90) were associated with increased risk of virus infection. No association with bacterial or fungal disease was found. Mortality was associated with pre-transplant MBL levels < 1000 ng/ml (hazard ratio 5.55, 95% CI 1.17-26.30, p = 0.03) but not with MBL2 genotype.

CONCLUSIONS

Patients who underwent Allo-HSCT with low pre-transplant MBL levels presented the first episode of infection earlier and had an increased risk of viral infections and mortality in the first 6 months post-transplant. Thus, pre-transplant MBL levels would be important in predicting susceptibility to viral infections and mortality and might be considered a biomarker to be included in the pre-transplantation risk assessment.

Mannose binding lectin and prediction of risk for chemotherapy induced febrile neutropenia in patients with a solid tumor

Mannose-binding lectin (MBL) - deficient patients who undergo chemotherapy for a solid tumor might have an increased risk developing febrile neutropenia (FN). We investigated in a prospective cohort study relations between MBL-serum levels and polymorphisms in MBL promotor genotypes (-550H/L and -221X/Y) on incidence and severity of FN. Risk of FN was 17.9% in MBL-deficient and 22.5% in MBL-sufficient patients (RR = 0.796, p = 0.45). Median MBL serum levels at baseline were respectively 1.39 µg/mL and 1.09 µg/mL (p = 0.92) in patients with and without FN. In conclusion, serum MBL and MBL genotypes (-550H/L and -221X/Y) do not determine the risk for developing FN.

The Role of Complement Activating Collectins and Associated Serine Proteases in Patients With Hematological Malignancies, Receiving High-Dose Chemotherapy, and Autologous Hematopoietic Stem Cell Transplantations (Auto-HSCT)

We conducted a prospective study of 312 patients (194 with multiple myeloma, 118 with lymphomas) receiving high-dose conditioning chemotherapy and autologous hematopoietic stem cell transplantation (auto-HSCT). Polymorphisms of MBL2 and MASP2 genes were investigated and serial measurements of serum concentrations of mannose-binding lectin (MBL), CL-LK collectin and MASP-2 as well as activities of MBL-MASP-1 and MBL-MASP-2 complex were made. Serum samples were taken before conditioning chemotherapy, before HSCT and once weekly after (totally 4-5 samples); in minority of subjects also 1 and/or 3 months post transplantation. The results were compared with data from 267 healthy controls and analyzed in relation to clinical data to explore possible associations with cancer and with chemotherapy-induced medical complications. We found a higher frequency of MBL deficiency-associated genotypes (LXA/O or O/O) among multiple myeloma patients compared with controls. It was however not associated with hospital infections or post-HSCT recovery of leukocytes, but seemed to be associated with the most severe infections during follow-up. Paradoxically, high MBL serum levels were a risk factor for prolonged fever and some infections. The first possible association of MBL2 gene 3′-untranslated region polymorphism with cancer (lymphoma) in Caucasians was noted. Heterozygosity for MASP2 gene +359 A>G mutation was relatively frequent in lymphoma patients who experienced bacteremia during hospital stay. The median concentration of CL-LK was higher in myeloma patients compared with healthy subjects. Chemotherapy induced marked increases in serum MBL and MASP-2 concentrations, prolonged for several weeks and relatively slighter decline in CL-LK level within 1 week. Conflicting findings on the influence of MBL on infections following chemotherapy of myeloma and lymphoma have been reported. Here we found no evidence for an association between MBL deficiency and infection during the short period of neutropenia following conditioning treatment before HSCT. However, we noted a possible protective effect of MBL during follow-up, and suspected that to be fully effective when able to act in combination with phagocytic cells after their recovery.

Low circulating mannan-binding lectin levels correlate with increased frequency and severity of febrile episodes in myeloma patients who undergo ASCT and do not receive antibiotic prophylaxis

Patients with multiple myeloma (MM) who undergo autologous stem cell transplantation (ASCT) are susceptible to severe infections. Low levels of circulating mannan-binding lectin (MBL) are associated with increased risk of infection. In this prospective study, we evaluated 100 patients who underwent ASCT regarding the effect of MBL on the incidence and severity of febrile episodes. Seventeen patients had MBL levels <500 ng/mL (11 received antibiotic prophylaxis and 6 did not). Although there was no statistical difference regarding the development of febrile episodes between patients with low and normal MBL, among 17 patients with low MBL levels, six out of eleven patients who received antibiotic prophylaxis developed a febrile episode compared with six out of six patients who did not receive antibiotic prophylaxis and developed a febrile episode. Patients with low MBL levels who responded less frequently to first line antibiotic therapy required more frequent administration of a second more advanced line of antibiotics, independently of receiving or not prophylaxis, and required prolonged hospitalization. In the univariate analysis low MBL associated with shorter OS. Our results suggest that patient with low MBL levels should receive antibiotic prophylaxis to reduce the number of febrile episodes and raise the issue of MBL replacement for these patients.

Evaluation of Mannose-Binding Lectin is a Useful Approach to Predict the Risk of Infectious Complications Following Autologous Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) associated immunocompromised state carries high risk of infectious complications. Mannose-binding lectin (MBL) is an acute phase protein involved in innate immune response. Serum MBL level is genetically determined and quite stable. According to literature, significant association was shown between low MBL concentrations and serious infections. The association between serum MBL level and frequency and severity of infections was studied in 186 patients following autologous HSCT. Double-monoclonal antibody sandwich enzyme-linked immunosorbent assay was used to determine MBL antigen level in sera. MBL levels were measured around 100 days following transplantation, in a period without active infection. Twenty-one patients (11%) were MBL deficient. The median time of first infection and number of infections during the first year post-transplantation were not significantly different between patients with MBL deficiency and those without MBL deficiency. The occurrence and number of infections after HSCT correlated with the MBL/C-reactive protein ratio. The number of severe infections was not higher among those with MBL deficiency. The occurrence of infections after the pre-engraftment period during the first year post-transplantation was significantly different in patient groups separated by MBL cut-off level. The MBL/C-reactive protein ratio might be a useful marker of infectious complications. MBL measurement may be helpful in antibiotic treatment. In case of MBL deficiency, earlier and more intensive treatment may be indicated.

Risk stratification and immunogenetic risk for infections following stem cell transplantation

Patients undergoing haematopoietic stem cell transplantation (HSCT) are highly exposed to infectious agents. However, it is not known why certain HSCT recipients rapidly develop severe infections while other, despite similar immunosuppressive conditions, do not. Increasing evidence suggests that such differences may be due, in part, to polymorphisms in immune genes. Thus, the identification of genetic factors influencing susceptibility to infections in HSCT recipients may lead to the development of individualized management strategies. However, studies are challenged by several issues, including the relative small size of existing cohorts, the frequent use of prophylactic or preemptive antimicrobial agents, and the fact that genes responsible for immune functions can be inherited either from the donor or the host. Consequently, the major challenge for today's researchers is to overcome these limitations and find associations that are robust enough to be translated into reliable risk stratification strategies for infectious diseases.

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.

Early Changes of Mannose-Binding Lectin, H-Ficolin, and Procalcitonin in Patients with Febrile Neutropenia: A Prospective Observational Study

Objective:

The significance of mannose-binding lectin (MBL) and H-ficolin deficiency in febrile neutropenic (FN) patients and the correlation of these markers along with consecutive C-reactive protein (CRP) and procalcitonin (PCT) levels during the infectious process are investigated.

Materials and Methods:

Patients with any hematological malignancies who were defined to have “microbiologically confirmed infection”, “clinically documented infection”, or “fever of unknown origin” were included in this single-center prospective observational study. Serum levels of CRP, PCT, MBL, and H-ficolin were determined on 3 separate occasions: at baseline (between hospital admission and chemotherapy), at the onset of fever, and at the 72nd hour of fever.

Results:

Forty-six patients (54% male, mean age 41.7 years) with 61 separate episodes of FN were evaluated. Eleven patients (23.9%) had “microbiologically confirmed infection”, 17 (37%) had “clinically documented infection”, and 18 (39.1%) had “fever of unknown origin”. Fourteen (30.4%) patients had low (<500 ng/mL) initial MBL levels and 7 (15.21%) had low (<12,000 ng/mL) H-ficolin levels. Baseline MBL and H-ficolin levels did not significantly change on the first and third days of fever (p=0.076). Gram-negative bacteremia more frequently occurred in those with low initial MBL levels (p=0.006). PCT levels were significantly higher in those with microbiologically documented infections. Mean and median PCT levels were significantly higher in cases with bacteremia. There was no significant difference between hemoculture-positive and-negative patients in terms of CRP levels.

Conclusion:

Monitoring serum H-ficolin levels was shown to be of no benefit in terms of predicting severe infection. Low baseline MBL levels were correlated with high risk of gram-negative bacteremia; however, no significant correlation was shown in the follow-up. Close monitoring of PCT levels is warranted to provide more accurate and specific data while monitoring cases of bacteremia.

Infections After High-Dose Chemotherapy and Autologous Hematopoietic Stem Cell Transplantation

Infection represents an important cause of morbidity after autologous hematopoietic stem cell transplantation (HSCT). Immunodeficiency is the key risk factor and results from interplay between the underlying disease and its therapy. Various defects in the immune system coexist in HSCT recipients. In the early post-transplant period, neutropenia, oral and gastrointestinal mucositis, and the presence of central venous catheters are the main risk factors. Bacterial infections predominate, and the agents and antibiotic susceptibility profiles vary widely in different regions. Invasive candidiasis is infrequent with fluconazole use, but the incidence of invasive aspergillosis is on the rise, mainly in patients receiving purine analogues or intensive chemotherapy before transplant. In the post-engraftment period, infections are less frequent, but may contribute to significant non-relapse mortality. The dynamics of immune reconstitution drives the risk for infection in this period. The most frequent infections are varicella-zoster virus disease and respiratory tract infections. Assessment of the risk of infection in each period and the identification of patients at higher risk of specific infections are critical to the appropriate management of infectious complications after autologous hematopoietic stem cell transplantation.

Serum mannose-binding lectin and C-reactive protein are potential biomarkers for patients with community-acquired pneumonia

AIM

The aim of this study was to identify whether mannose-binding lectin (MBL) and C-reactive protein (CRP) may be used as clinical biomarkers for predicting outcome of community-acquired pneumonia (CAP) by tracking serum MBL and CRP level changes during a time course.

METHODS

One hundred four patients with CAP and 100 healthy individuals were enrolled in this study. The patients were further divided into Survivor and Death groups based on 30-day mortality. The MBL and CRP levels in these patients at pre- and post-treatments at days 4 and 7 were determined using an immunoturbidimetric assay and an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared to the control group, the MBL and CRP levels in the CAP group were significantly higher. CRP levels in the CAP group significantly reduced within 1 week following anti-infection and other supporting therapies including anti-phlegm and liquidation. MBL levels were significantly higher in the Survivor group than in the Death group (p<0.05). On the contrary, CRP levels were significantly higher in the Death group than in the Survivor group (p<0.05). There was a negative correlation between the serum MBL and CRP levels in all patients following the treatments.

CONCLUSION

Both the MBL and CRP can serve as inflammatory markers in predicting the outcome of patients with CAP.

Mannose-binding lectin gene variants and infections in patients receiving autologous stem cell transplantation

Background

Serious infections are common in patients undergoing autologous stem cell transplantation (ASCT) mainly because of the effects of immunosuppression. The innate immune system plays an important role in the defense against different infections. Mannose binding lectin (MBL) is a central molecule of the innate immune system. There are several promoter polymorphisms and structural variants of the MBL2 gene that encodes for this protein. These variants produce low levels of MBL and have been associated with an increased risk for infections.

Methods

Prospective cohort study. The incidence, severity of infections and mortality in 72 consecutive patients with hematologic diseases who underwent ASCT between February 2006 and June 2008 in a tertiary referral center were analyzed according to their MBL2 genotype. INNO-LiPA MBL2 was used for MBL2 gene amplification and genotyping. Relative risks (RR) (IC95%) as measure of association were calculated. Multivariate analysis was performed using logistic regression.

Results

A statistically significant higher number of fungal infections was found in patients with MBL2 variants causing low MBL levels (21.1%versus1.9%, p=0.016). In this MBL2 variant group infection was more frequently the cause of mortality than in the MBL2 wild-type group (p=0.05). Although not statistically significant, there was a higher incidence of major infections in the MBL2 variant group as well as a higher number of infections caused by gram-positive bacteria.

Conclusions

Low-producer MBL2 genotypes were associated with an increased number of fungal infections in ASCT patients, which would suggest that MBL has a protective role against such infections. ASCT patients with MBL2 variant genotypes are more likely to die as a result of an infection.

Mannose-binding lectin 2 gene polymorphism and susceptibility to upper respiratory tract infection among endurance athletes

The aim of this study was to investigate the influence of mannose-binding lectin 2 (MBL2)-exon-1 gene polymorphisms on upper respiratory tract infection (URTI) incidence among endurance athletes. To this end, 100 healthy elite male athletes participating in the study were classified as either healthy or prone to frequent URTI. Blood samples, DNA isolation, multiplex polymerase chain reaction (PCR) and conventional PCR-RFLP were performed. Genomic DNA was extracted from peripheral leukocytes of whole blood samples using the QIAmp DNA Blood Mini Kit. For comparison of the distribution of genotypes between two groups and for estimating odds ratios (OR) for URTI susceptibility in relation to the MBL2-exon-1 polymorphism, Pearson's chi-square and logistic regression method were used, respectively. The MBL2-exon-1 genotype distribution differed between athletes with URTI and healthy athletes (χ(2) = 7.81, p = 0.02). The AO and AO + OO genotypes of MBL2 were observed at a greater frequency in the illness-prone group compared with the healthy group (34.04% vs. 11.32%). In conclusion, findings from this study have identified a potential role of genetic variation in influencing the risk for URTI in athletic populations and single-nucleotide polymorphisms (SNPs) in the MBL2-exon-1 genes were associated with an altered risk profile. These measures may have a predictive value in the identification of individuals who are more likely to experience recurrent infections when exposed to high physical stress in the areas of athletic endeavour.

Mannose-binding lectin polymorphisms and the risk of sepsis: evidence from a meta-analysis

Several studies have evaluated the association between mannose-binding lectin (MBL) polymorphisms and sepsis. However, the results are inconclusive and conflicting. To better understand the roles of MBL polymorphisms in sepsis, we conducted a comprehensive meta-analysis. All relevant studies were searched from PubMed, EMBASE and Web of Knowledge databases, with the last report up to 7 May 2013. Twenty-nine studies addressing four MBL polymorphisms (-550G/C, -221G/C, structure variant A/O, Gly54Asp) were analysed for susceptibility to sepsis and one study for sepsis-related mortality. Overall, significant associations between structure variant A/O and susceptibility to sepsis were observed for AO + OO vs. AA [odds ratio (OR) 1·27, 95% confidence interval (CI) 1·05-1·52, P = 0·01] and O vs. A (OR 1·19, 95% CI 1·02-1·40, P = 0·03). In subgroup analysis based on age group, increased risk was found in the paediatric group in the dominant model (OR 1·72, 95% CI 1·16-2·56, P = 0·007). Moreover, there was a slight association between the +54A/B polymorphism and susceptibility to sepsis in Caucasians (recessive model: OR 10·64, 95% CI 1·24-91·65, P = 0·03). However, no association was observed for -550G/C and -221G/C polymorphisms both overall and in subgroup analysis. For sepsis-related mortality, only one study suggested AO/OO was associated with in-hospital mortality in pneumococcal sepsis patients after controlling for confounding variables. Our meta-analysis indicated that MBL structure variants might be associated with susceptibility to sepsis but further studies with a large sample size should be conducted to confirm these findings.

Autologous hematopoietic stem cell transplantation following high dose chemotherapy for non-rhabdomyosarcoma soft tissue sarcomas

BACKGROUND

Soft tissue sarcomas (STS) are a highly heterogeneous group of rare malignant solid tumors. Non-rhabdomyosarcoma soft tissue sarcomas (NRSTS) comprise all STS except rhabdomyosarcoma. In patients with advanced local or metastatic disease, autologous hematopoietic stem cell transplantation (HSCT) applied after high-dose chemotherapy (HDCT) is a planned rescue therapy for HDCT-related severe hematologic toxicity. The rationale for this update is to determine whether any randomized controlled trials (RCTs) have been conducted and to clarify whether HDCT followed by autologous HSCT has a survival advantage.

OBJECTIVES

To assess the effectiveness and safety of HDCT followed by autologous HSCT for all stages of non-rhabdomyosarcoma soft tissue sarcomas (NRSTS) in children and adults.

SEARCH METHODS

For this update we modified the search strategy to improve the precision and reduce the number of irrelevant hits. All studies included in the original review were considered for re-evaluation in the update. We searched the electronic databases CENTRAL (2012, Issue 11) in The Cochrane Library , MEDLINE and EMBASE (05 December 2012) from their inception using the newly developed search strategy. Online trials registers and reference lists of systematic reviews were searched.

SELECTION CRITERIA

Terms representing STS and autologous HSCT were required in the title or abstract. In studies with aggregated data, participants with NRSTS and autologous HSCT had to constitute at least 80% of the data. Single-arm studies were included in addition to studies with a control arm because the number of comparative studies was expected to be very low.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted study data. Some studies identified in the original review were re-examined and found not to meet the inclusion criteria and were excluded in this update. For studies with no comparator group, we synthesized the results for studies reporting aggregate data and conducted a pooled analysis of individual participant data using the Kaplan-Meyer method. The primary outcomes were overall survival (OS) and treatment-related mortality (TRM).

MAIN RESULTS

The selection process was carried out from the start of the search dates for the update. We included 57 studies, from 260 full text articles screened, reporting on 275 participants that were allocated to HDCT followed by autologous HSCT. All studies were not comparable due to various subtypes. We identified a single comparative study, an RCT comparing HDCT followed by autologous HSCT versus standard chemotherapy (SDCT). The overall survival (OS) at three years was 32.7% versus 49.4% with a hazard ratio (HR) of 1.26 (95% confidence interval (CI) 0.70 to 2.29, P value 0.44) and thus not significantly different between the treatment groups. In a subgroup of patients that had a complete response before treatment, OS was higher in both treatment groups and OS at three years was 42.8% versus 83.9% with a HR of 2.92 (95% CI 1.1 to 7.6, P value 0.028) and thus was statistically significantly better in the SDCT group. We did not identify any other comparative studies. We included six single-arm studies reporting aggregate data of cases; three reported the OS at two years as 20%, 48%, and 51.4%. One other study reported the OS at three years as 40% and one further study reported a median OS of 13 months (range 3 to 19 months). In two of the single-arm studies with aggregate data, subgroup analysis showed a better OS in patients with versus without a complete response before treatment. In a survival analysis of pooled individual data of 80 participants, OS at two years was estimated as 50.6% (95% CI 38.7 to 62.5) and at three years as 36.7% (95% CI 24.4 to 49.0). Data on TRM, secondary neoplasia and severe toxicity grade 3 to 4 after transplantation were sparse. The one included RCT had a low risk of bias and the remaining 56 studies had a high risk of bias.

AUTHORS' CONCLUSIONS

A single RCT with a low risk of bias shows that OS after HDCT followed by autologous HSCT is not statistically significantly different from standard-dose chemotherapy. Therefore, HDCT followed by autologous HSCT for patients with NRSTS may not improve the survival of patients and should only be used within controlled trials if ever considered.

Mannose-binding lectin genotype influences frequency and duration of infectious complications in children with malignancy

Children with cancer receiving identical treatment differ in their experience of infection, suggesting that variations in immunity may influence susceptibility to infection. Studies of the influence of mannose-binding lectin (MBL), an important component of the innate immune system, in children with febrile neutropenia (FN) have yielded conflicting results. We examined the role of MBL in infection susceptibility in the largest cohort of children with cancer reported to date. MBL levels were measured and genotyping performed on children (≤16 y) receiving chemotherapy for cancer in London, UK. Clinical data from FN episodes were recorded prospectively. MBL status was assessed in 269 children; 513 episodes of FN were captured from 211 patients. Patients with MBL2 polymorphisms experienced more FN episodes than wildtype genotype (median 2 vs. 1, respectively; P = 0.074) and more episodes with documented infection (P = 0.045). Patients experiencing multiple FN episodes had lower MBL levels (P = 0.036). MBL genotype influenced duration of episode in some groups: high-risk MBL-deficient patients spent up to 5 nights longer/episode in hospital than equivalent wildtypes. These results indicate that MBL deficiency influences both susceptibility to and outcome of FN episodes and may be most important in those patients at higher risk of complications of FN.

Mannan-binding lectin in malignancy

Complement may play a dual role in cancer: it may contribute either to the development or to the inhibition of tumour growth. Its components may be candidate biomarkers facilitating the disease detection, its progress or effectiveness of therapy. Additionally, complement deficiencies may increase the risk of infections and contribute to the higher mortality, especially in patients undergoing aggressive chemotherapy. In this paper, possible cancer associations of one of the factors activating complement via the lectin pathway, mannan-binding lectin (MBL), are discussed.

Antimicrobial therapy of febrile complications after high-dose chemotherapy and autologous hematopoietic stem cell transplantation--guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO)

More than 18,000 autolgous transplantation were performed in Europe in the year 2009. It as a routine procedure in experienced centres. Even if there is a low mortality rate, infections are a major issue after transplantation, occurring in more than 60 % of the patients. In this review we discuss all aspects of infections after autologous stem transplantation, including epidemiology, diagnostics, therapeutic algorithms, prophylaxis and supportive therapy.

MBL Deficiency as Risk of Infection and Autoimmunity

In pathogen recognition by C-type lectins, several levels of complexity can be distinguished; these might modulate the immune response in different ways. Firstly, the pathogen-associated molecular pattern repertoire expressed at the microbial surface determines the interactions with specific receptors (Fig. 42.1). Secondly, each immune cell type possesses a specific set of pathogen-recognition receptors. Thirdly, changes in the cell-surface distribution of C-type lectins regulate carbohydrate binding by modulating receptor affinity for different ligands. Crosstalk between these receptors results in a network of multimolecular complexes, adding a further level of complexity in pathogen recognition (Cambi and Figdor 2005; Thiel et al. 2006) (see 10.1007/978-3-7091-1065-2_23). MBL deficiency is genetically determined and predisposes to recurrent infections and chronic inflammatory diseases. MBL deficiency has been implicated in susceptibility and course of viral, bacterial, fungal, and protozoan infection. More than 10% of the general population may, depending on definition, be classified as MBL deficient, underlining the redundancy of the immune system. MBL-disease association studies have been a fruitful area of research, which implicates a role for MBL in infective, inflammatory and autoimmune disease processes. MBL deficiency predisposes both to infection by extra-cellular pathogens and to autoimmune disease.

Serum levels of mannose-binding lectin and the risk of infection in pediatric oncology patients with chemotherapy

Morbidity and mortality due to infections remain serious problems in pediatric oncology patients receiving chemotherapy. Association of mannose-binding lectin (MBL) levels with an increased risk for infection in previous studies was contradictory. The aim of this study was to determine whether MBL deficiency is associated with the risk of infections in pediatric oncology patients. Before the start of chemotherapy a blood sample was taken from 75 patients with acute lymphoblastic leukemia and MBL serum concentration was measured using a commercially enzyme-linked immunosorbent assay kit. Twenty patients had concentrations under 1000 µg/L, defining MBL deficiency and the remaining 55 patients had concentrations >1000 µg/L. Ten patients suffered from more than 1 episode of severe infection. Sixty-five percent of patients with MBL below 1000 µg/mL suffered from 2 or more episodes of infections (3 of 16 individuals with 1 severe infection; 10 of 16 with 2 and 3 of 16 with 3), in contrast to only 29 of 55 (52%) patients with MBL above 1000 µg/mL (19 of 27 individuals with 1 severe infection and 10 of 27 with 2). The difference between 2 groups was significant (P<0.001). The results of this study indicate that low MBL serum levels (<1000 µg/L) identify pediatric cancer patients at increased risk for infections.

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

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

Systemic mannose-binding lectin is not associated with Chronic Obstructive Pulmonary Disease

Mannose-binding lectin (MBL) deficiency is associated with increased susceptibility to airways infections and autoimmunity. We examined whether MBL deficiency was more common in COPD patients, and whether MBL deficiency was associated with COPD severity. 415 COPD patients and 231 healthy subjects, aged 40-75, were examined in 2006/07. Plasma MBL levels were determined by ELISA. Low or deficient MBL levels were defined as plasma levels below 500ng/mL or 100ng/mL respectively. Logistic regression models determined factors associated with MBL deficiency; with explanatory variables study category, sex, age, smoking, comorbid heart disease, and CRP. For COPD severity, explanatory variables were FEV1, exacerbation history, hypoxia, respiratory symptoms, inhaled steroids, and CRP. 18.2% of healthy subjects and 22.2% of patients had MBL levels below 100ng/mL (p=0.23); 42.9% of healthy subjects and 49.6% of patients had levels below 500ng/mL (p=0.10). After adjustment for co-variables, patients had an OR (95% CI) of 1.26 (0.7, 2.2) for having MBL levels below 100ng/mL compared with healthy subjects, and an OR (95% CI) of 1.06 (0.7, 1.7) for having levels below 500ng/mL. Among the COPD patients, none of the disease variables were associated with MBL deficiency. No association was found between MBL deficiency and COPD or COPD severity.

Recombinant form of human wild type mannan-binding lectin (MBL/A) but not its structural variant (MBL/C) promotes phagocytosis of zymosan by activating complement

Mannan-binding lectin (MBL) mediates innate immune responses, such as activation of the complement lectin pathway and phagocytosis, to help fight infections. In the present study, employing recombinant forms of human MBL (rMBL), the role of wild type MBL (rMBL/A) and its structural variant rMBL/C in mediating THP-1 phagocytosis of fluorescent-labeled zymosan was examined and compared to MBL purified from human plasma (pMBL/A). Flow cytometric analyses revealed that opsonization of zymosan with rMBL/A and pMBL/A (0.5-30microg/ml) resulted in a 1.9- and 2.7-fold enhancement in its uptake by THP-1 cells in the presence of serum that was depleted of both MBL and the classical pathway component, C1q (MBL/C1q Dpl serum). In contrast, no enhancement in phagocytosis was observed when zymosan was opsonized with rMBL/C. Addition of MBL monoclonal antibody, EDTA, or mannan to the opsonization reaction mixture inhibited THP-1 phagocytosis of pMBL/A opsonized zymosan. Heat inactivation of MBL/C1q Dpl serum abolished the 2-fold increase in phagocytosis and in the absence of serum the direct opsonic activity of MBL did not contribute significantly to the uptake of zymosan into THP-1 cells. Activation products of complement components C3 and C4 were deposited on zymosan opsonized with pMBL/A and rMBL/A but not rMBL/C indicating that MBL-mediated phagocytosis of zymosan requires activation of the complement lectin pathway. The findings imply that impaired MBL-mediated phagocytosis may put individuals homozygous for the mutant allele MBL/C but not wild type MBL/A at increased risk to infections such as yeast.

Influence of MBL-2 mutations in the infection risk of patients with follicular lymphoma treated with rituximab, fludarabine, and cyclophosphamide

The employment of current treatments based on chemotherapy and immunotherapy leads to inmunosuppression. The presence of mutations or polymorphisms in genes related to immune system might involve an additional disadvantage. The aim of the present study was to analyze mannose-binding lectin (MBL-2 gene) mutations and their association with severe infections and event-free survival in patients diagnosed with follicular lymphoma, treated uniformly, in the clinical trial LNHF-03. The results of this trial showed impressive clinical efficacy but was complicated with 80 documented infectious episodes. Patients were classified into two genotypic groups, AA and AO/OO, based on their haplotypic inheritance. Neither the number of infectious episodes nor differences in event-free survival was found as a function of MBL-2 groups. Other factors, including the lymphoma malignancy and the immune alterations associated with the disease, should be considered responsible for this observation.

Use of a modeling framework to evaluate the effect of a modifier gene (MBL2) on variation in cystic fibrosis

Variants in mannose-binding lectin (MBL2; protein MBL) have shown association with different aspects (eg, lung function, infection, survival) of cystic fibrosis (CF) in some studies but not others. Inconsistent results may be due to confounding among disease variables that were not fully accounted for in each study. To account for these relationships, we derived a modeling framework incorporating CFTR genotype, age, Pseudomonas aeruginosa (Pa) infection, and lung function from 788 patients in the US CF Twin and Sibling Study. This framework was then used to identify confounding variables when testing the effect of MBL2 variation on specific CF traits. MBL2 genotypes corresponding to low levels of MBL associated with Pa infection 1.94 years earlier than did MBL2 genotypes corresponding to high levels of MBL (P=0.0034). In addition, Pa-infected patients with MBL2 genotypes corresponding to low levels of MBL underwent conversion to mucoid Pa 2.72 years earlier than did patients with genotypes corresponding to high levels of MBL (P=0.0003). MBL2 was not associated with the time to transition from infection to conversion or with lung function. Thus, use of a modeling framework that identified confounding among disease variables revealed that variation in MBL2 associates with age at infection with Pa and age at conversion to mucoid Pa in CF.

Pharmacologic rationale for early G-CSF prophylaxis in cancer patients and role of pharmacogenetics in treatment optimization

The use of recombinant human granulocyte colony stimulating factors (G-CSF) has become an integral part of supportive care during cytotoxic chemotherapy. Current guidelines recommend the use of G-CSF in patients with substantial risk of febrile neutropenia. However, little consensus exists about optimal timing and tailoring of this therapy. Based on the known effects of chemotherapy and G-CSF on bone marrow compartments, we propose a model that supports the prophylactic rather than therapeutic use of G-CSF therapy. In addition, several genetic alterations in G-CSF signalling pathway have been described. These genetic variants may predict the risk of febrile neutropenia and response to G-CSF. Thus, future pharmacogenetic/omics studies in this field are warranted. Through the identification of patients at risk and the knowledge of biological basis for optimal timing, hopefully we should soon be able to improve the application of the existing guidelines for G-CSF therapy and patient's prognosis.

Complement activating soluble pattern recognition molecules with collagen-like regions, mannan-binding lectin, ficolins and associated proteins

Mannan-binding lectin (MBL), L-ficolin, M-ficolin and H-ficolin are all complement activating soluble pattern recognition molecules with recognition domains linked to collagen-like regions. All four may form complexes with four structurally related proteins, the three MBL-associated serine proteases (MASPs), MASP-1, MASP-2 and MASP-3, and a smaller MBL-associated protein (MAp19). The four recognition molecules recognize patterns of carbohydrate or acetyl-group containing ligands. After binding to the relevant targets all four are able to activate the complement system. We thus have a system where four different and/or overlapping patterns of microbial origin or patterns of altered-self may be recognized, but in all cases the signalling molecules, the MASPs, are shared. MASP-1 and MASP-3 are formed from one gene, MASP1/3, by alternative splicing generating two different mRNAs from a single primary transcript. Similarly MASP-2 and MAp19 are both generated from one gene, MASP-2/MAp19, by alternative splicing. A number of non-synonymous polymorphisms of the four recognition molecules and of the MASPs are known, and the implications of these alterations are being studied. The clinical impact of deficiencies will be discussed.

Serum levels of mannose-binding lectin and the risk of fever in neutropenia pediatric cancer patients

BACKGROUND

Fever in neutropenia (FN) is a frequent complication in pediatric oncology. Deficiency of mannose-binding lectin (MBL), an important component of innate immunity, is common due to genetic polymorphisms, but its impact on infections in oncologic patients is controversial. This study investigated whether MBL serum levels at cancer diagnosis are associated with the development of FN in pediatric cancer patients.

PROCEDURE

Serum MBL was measured using ELISA. Frequency, duration, and cause of FN were assessed retrospectively. Association with MBL level was analyzed using uni- and multivariate Poisson regression taking into account both intensity and duration of chemotherapy.

RESULTS

In 94 children, with a cumulative follow-up time of 81.7 years, 177 FN episodes were recorded. Patients with both very low MBL levels (<100 microg/L; risk ratio (RR), 1.93; 95% CI, 1.14-3.28; P = 0.014) and normal MBL levels (>or=1,000 microg/L; RR, P = 0.011) had significantly more frequent FN episodes than patients with low MBL levels (100-999 microg/L). Patients with very low MBL levels had significantly more episodes of FN with severe bacterial infection (bacteremia or pneumonia; RR, 4.49; 1.69 = 11.8; P = 0.003), while those with normal MBL levels had more FN episodes with no microbial etiology identified (RR, 1.85; 1.14 = 3.03; P = 0.014).

CONCLUSIONS

Very low MBL levels are associated with more frequent FN episodes, mainly due to severe bacterial infections. The surprising finding that children with normal MBL levels had more frequent FN episodes than those with low MBL levels needs testing in prospective studies.

Mannan-binding lectin (MBL) in women with tumours of the reproductive system

Mannan-binding lectin (MBL) is an important factor of innate immunity contributing to the clearance of microorganisms. Recently, an antitumourigenic role of MBL has been suggested. We investigated mbl2 genotypes, MBL concentrations, and MBL-MASP-2 complex activity in patients with ovarian cancer. The expression of both mbl2 and masp-2 genes were investigated in ovarian tissue sections. Additionally, samples from patients with other malignant and benign tumours of the reproductive tract were tested. A significantly higher incidence of MBL deficiency/insufficiency-associated genotypes was found among patients with malignant disease compared to age-matched controls. Unexpectedly, no differences in median MBL level or MBL-MASP-2 complex activity were found between the groups. This was partly a reflection of higher MBL concentrations and MBL-MASP-2 activity in cancer patients compared with healthy women carrying corresponding genotypes. MBL-specific mRNA expression was detected in several normal and malignant ovarian tissues, as well as in ovarian epithelial cell lines. Intracellular staining with MBL-specific antibodies demonstrated the presence of MBL in ovarian cell lines, and in normal as well as malignant ovarian tissue sections. In contrast, MASP-2-specific mRNA expression was detected only in the ovary tissues of patients with malignant disease. No significant changes in MBL concentration during 3 months of chemotherapy were noticed. MBL was detected in ascites and in the fluid of benign ovarian cysts. Our findings may reflect anti-tumourigenic activity of MBL protein which might suggest potential therapeutic application. However, it cannot be excluded that mbl-2 mutant alleles may be in linkage disequilibrium with an unidentified tumour susceptibility gene(s).

Low Mannose-Binding Lectin Concentration Is Associated with Severe Infection in Patients with Hematological Cancer Who Are Undergoing Chemotherapy

BACKGROUND

Mannose-binding lectin (MBL) is a serum lectin involved in innate immune response. Low serum MBL concentration may constitute a risk factor for infection in patients receiving myelosuppressive chemotherapy.

METHODS

We conducted a prospective, observational study that assessed MBL concentration as a risk factor for infection in patients with hematological malignancy who were hospitalized to undergo at least 1 chemotherapy cycle. MBL deficiency was defined using an algorithm that considered the serum MBL concentration and the MBL genotype. The primary end point was the ratio of duration of febrile neutropenia to the duration of neutropenia. Secondary end points included the incidence of severe infection (e.g., sepsis, pneumonia, bacteremia, and invasive fungal infection). Logistic regression analysis was conducted, and Fisher's exact test was used to analyze binary outcomes, and Kaplan-Meier estimates and log rank tests were used for time-to-event variables.

RESULTS

We analyzed 255 patients who received 569 cycles of chemotherapy. The median duration of neutropenia per cycle was 7 days (interquartile range, 0-13 days). Sixty-two patients (24%) were found to have MBL deficiency. Febrile neutropenia occurred at least once in 200 patients. No difference in the primary outcome was seen. The incidence of severe infection was higher among MBL-deficient patients than among non-MBL-deficient patients (1.96 vs. 1.34 cases per 100 days for analysis of all patients [P=.008] and 1.85 vs. 0.94 cases per 100 days excluding patients with acute leukemia [P<.001]).

CONCLUSIONS

MBL deficiency does not predispose adults with hematological cancer to more-frequent or more-prolonged febrile episodes during myelosuppressive chemotherapy, but MBL-deficient patients have a greater number of severe infections and experience their first severe infection earlier, compared with nondeficient patients.

Aspects of genetic susceptibility to human infectious diseases

Host genetic factors play a major role in determining differential susceptibility to major infectious diseases of humans, such as malaria, HIV/AIDS, tuberculosis, and invasive pneumococcal disease. Progress in identifying the relevant genetic loci has come from a variety of approaches. Most convincing associations have been identified by case-control studies assessing biologically plausible candidate genes. All six of the genes that have a major effect on infectious disease susceptibility in humans have been identified in this way. However, recently genome-wide linkage analysis of affected sibling pairs has identified susceptibility loci for chronic infections such as leprosy and chronic hepatitis B virus persistence. Other approaches used successfully have included assessment in humans of the homologues of susceptibility genes mapped and identified in murine models. However, the great majority of susceptibility loci remain to be identified and the advent of large-scale genome-wide association scans offers a new approach to defining many of these.

New directions in the genomics of allogeneic hematopoietic stem cell transplantation

Despite optimal supportive care and high-resolution HLA matching, complications such as GVHD and infection remain major barriers to the success of allogeneic HCT (allo-HCT). This has led to growing interest in the non-HLA genetic determinants of complications after allo-HCT. Most studies have examined genetic predictors of GVHD, relapse, and mortality and have focused on 3 main areas: minor histocompatibility antigen (miHAs), inflammatory mediators of GVHD, and more recently NK cell-mediated allorecognition. The genetic basis of other outcomes such as infection and drug toxicity are less well studied but are being actively investigated. High-throughput methodologies such as single nucleotide polymorphism arrays are enabling the study of hundreds of thousands of genetic markers throughout the genome and the interrogation of novel genetic variants such as copy number variations. These data offer the opportunity to better predict those at risk of complications and to identify novel targets for therapeutic intervention. This review examines the current data regarding the non-HLA genomics of allo-HCT and appraises the promises and pitfalls for integration of this new genetic information into clinical transplantation practice.

Mannan-binding lectin pathway deficiencies and invasive fungal infections following allogeneic stem cell transplantation

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.

CONCLUSION

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.

MBL2 polymorphism and risk of severe infections in multiple myeloma patients receiving high-dose melphalan and autologous stem cell transplantation

Severe infections related to treatment are common in patients with multiple myeloma (MM). Genetic polymorphisms of the immune system may influence the risk of infections. Mannan-binding lectin (MBL) is part of the innate immune system, and individuals homozygous for wild-type MBL encoding gene (MBL2) have a well-functioning MBL pathway of complement activation, in contrast to individuals carrying one or two variant alleles. We evaluated 113 courses of high-dose melphalan and autologous stem cell transplantation (ASCT) in patients with MM. Patients homozygous for wild-type MBL2 had a significantly reduced risk of septicaemia during the ASCT procedure compared with patients carrying variant MBL2: Odds Ratio (OR) 0.19 (95% CI: 0.04-0.77), (P=0.02) in multivariate analysis. The risk of Common Toxicity Criteria grade 3-4 infections in general was not affected by wild-type MBL2: OR 1.20 (95% CI: 0.52-2.78), (P=0.67). The findings indicate that MBL to some extent protects against the most severe infections during ASCT.

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.

Infections during induction therapy of childhood acute lymphoblastic leukemia - no association to mannose-binding lectin deficiency

OBJECTIVES

Infection during the induction phase of childhood acute lymphoblastic leukemia (ALL) is a major cause of morbidity and mortality. Several studies have indicated that genetically determined low serum levels of mannose-binding lectin (MBL), a component of innate immunity, are associated with increased risk for infections in patients receiving chemotherapy. Thus, these patients have been proposed to be candidates for MBL replacement therapy.

METHODS

In a population-based cohort of 137 children with ALL treated at a single pediatric hematology-oncology center with an almost identical chemotherapy regimen, we studied the relationship between polymorphisms in the MBL gene (MBL2) and the MBL2 promoter and the risk of infections during the first 50 d of induction therapy.

RESULTS

No increased frequency of infection was seen for the children with genotypes encoding serum low levels of MBL. A higher incidence of fever (P < 0.004), infectious events (P = 0.025), days with neutropenia (P < 0.001) and a higher frequency of antimicrobial therapy (P = 0.0007) were seen in the young age group (<2.5 yr) compared with the older age group (> or =2.5 yr), independent of the MBL genotype.

CONCLUSIONS

MBL deficiency did not influence the frequency of infections in children receiving induction chemotherapy for ALL, not even in the youngest children (<2.5 yr) whom we found to have the highest risk for infections.

The role of mannose-binding lectin (MBL) in paediatric oncology patients with febrile neutropenia

Children with cancer often have fever during chemotherapy-induced neutropenia, but only some develop serious infectious complications. Mannose-binding lectin (MBL) deficiency might increase infection susceptibility in these children. MBL genotype and phenotype were prospectively determined in 110 paediatric oncology patients. During febrile neutropenia, MBL concentrations were measured longitudinally in time. MBL genotype and phenotype were correlated to clinical and laboratory parameters. Structural exon-1 MBL2 mutations and the LX promoter polymorphism lead to deficient MBL concentrations. The capacity to increase MBL concentrations during febrile neutropenia was associated with MBL2 genotype. Infectious parameters did not differ between MBL-deficient and MBL-sufficient neutropenic children (n = 66). In contrast, MBL-sufficient patients had a greater risk of Intensive Care admittance (Relative Risk 1.6, 95% Confidence Interval 1.3-2.0, P = 0.04). MBL-deficient neutropenic children did not have more severe infections. However, most patients (61%) were severely neutropenic (<100 cells/microL), compromising the opsonophagocytic effector function of MBL. MBL substitution might still be beneficial in patients with phagocytic activity.

Clinical manifestations of mannan-binding lectin deficiency

Mannan-binding lectin (MBL) is a plasma protein of the innate immune system with the ability to initiate antimicrobial and inflammatory actions. MBL deficiency is common. More than 10% of the general population may, depending on definition, be classified as MBL deficient, underlining the redundancy of the immune system. Ongoing research attempt to illuminate at which conditions MBL deficiency may lead to disease. With examples, this review illustrates the diversity of results obtained so far.

Influence of FcgammaRIIA and MBL polymorphisms on severe acute respiratory syndrome

Polymorphisms of human Fc γ‐receptor IIA (FcγRIIA) and mannose‐binding lectin (MBL) genes have been associated with susceptibility to or severity of some infectious diseases. In order to investigate whether these genetic factors might influence susceptibility to infection with the severe acute respiratory syndrome‐associated coronavirus (SARS‐Cov) as well as the course and severity of the infection, we evaluated polymorphisms of FcγRIIA and MBL genes in DNA samples from a group of approximately 180 people from Hong Kong who were infected with SARS‐Cov. These included 132 patients who had moderate course of SARS infection (home subgroup), 26 patients with a severe course requiring treatment in an intensive care ward (ICU subgroup) and a subgroup of 22 patients who died from SARS (deceased subgroup). A total of 200 normal blood donors from the same region were used as controls. A significant association was found between the FcγRIIA‐R/R131 genotype and a severe course of SARS, with higher frequency of homozygosity for FcγRIIA‐R/R131 in the ICU subgroup of SARS patients when compared with controls (P = 0.03; odds ratio: 3.2; 95% confidence interval: 1.1–9.1). In comparison with controls, a significant difference in linear trend distribution of FcγRIIA genotypes was seen among the severe SARS patients (ICU and deceased subgroups) without co‐morbidity, and the incidence of FcγRIIA‐H/H131 was lower in these patients as well. There were no significant differences in MBL genotypes and allele frequencies among SARS patients and controls. The study reveals that in addition to age and co‐morbidity, FcγRIIA polymorphism of individuals may also influence outcome after infection with the SARS‐Cov.

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.

Neutropenia febril: pasado, presente y futuro

The present review aims to provide an overall view of the changes that have occurred in the last 40 years in the etiological agents isolated in febrile neutropenic patients, as well as in their antibacterial susceptibility patterns and their involvement in empirical treatment regimes. This overall view allows us to observe how the modifications introduced in the treatment of these patients has been accompanied by continual changes in the causative microorganisms, which in turn has required treatment regimens to be redesigned. Because of these constant changes, the significant advances achieved in diagnostic techniques and the recognition of subpopulations of patients with distinct degrees of morbidity and mortality, specialists in the various fields involved in the management of febrile neutropenic patients must constantly update their knowledge.