Genetic variants of the MBL2 gene are associated with mortality in pneumococcal sepsis

Host genetic variants associated with susceptibility and severity of pneumococcal pneumonia in adult patients

BACKGROUND

Pneumococcal community-acquired pneumonia (P-CAP) is a major cause of morbidity and hospitalization. Several host genetics factors influencing risk of pneumococcal disease have been identified, with less information about its association with P-CAP. The aim of the study was to assess the influence of single nucleotide polymorphisms (SNP) within key genes involved in the innate immune response on the susceptibility to P-CAP and to study whether these polymorphic variants were associated with the severity and outcome of the episodes in a cohort of adult Caucasian patients.

METHODS

Seventeen SNPs from 7 genes (IL-R1, IL-4, IL-10, IL-12B, NFKBIA, NFKBIE, NFKBIZ) were analyzed. For susceptibility, a case-control study including a cohort of 57 adult with P-CAP, and 280 ethnically matched controls was performed. Genetic influence on clinical severity and outcome was evaluated in a prospective observational study including all consecutive adult P-CAP patients from November 2015 to May 2017.

RESULTS

The NFKBIA polymorphism rs696 and a haplotype combination were associated with susceptibility to P-CAP (OR = 0.62, p = 0.005 and OR = 0.63, p = 0.008, respectively). The SNP IL4 rs2227284 was associated with severe P-CAP (OR = 2.17, p = 0.04). IL-R1 (rs3917267) and IL-10 (rs3024509) variants were related with respiratory failure (OR = 3.31, p = 0.001 and OR = 0.18, p = 0.003, respectively) as well as several haplotype combinations in NFKBIA, NFKBIZ, IL-R1 and IL-10 (p = 0,02, p = 0,01, p = 0,001, p = 0,03, respectively). CURB-65 values were associated with the IL-10 rs3024509 variant (beta = - 0.4, p = 0.04), and with haplotype combinations of NFKBIZ and IL-10 (p = 0.05, p = 0.04, respectively). Genetic variants in IL-10 (rs3024509) and in IL-12B (rs730691) were associated with PSI values (beta = - 0.54, p = 0.01, and beta = - 0.28, p = 0.04, respectively), as were allelic combinations in IL-R1 (p = 0.02) and IL-10 (p = 0.01). Finally, several polymorphisms in the IL-R1 gene (rs13020778, rs2160227, & rs3917267) were associated with the time elapsed until clinical stability (beta = - 0.83, p = 0.03; beta = - 1, p = 0.02 and beta = 1.07, p = 0.008, respectively).

CONCLUSIONS

A genetic variant in NFKBIA was associated with susceptibility to P-CAP in adult Caucasian patients and genetic variants from key cytokines of the innate immune response (Il-4, IL-10, IL-R1 and IL-12B) and NF-κB inhibitors were associated with different phenotypes of severe P-CAP. If validated, these SNPs may help to identify people at risk of P-CAP or severe P-CAP on which preventive measures could be applied.

Role of MBL2 Polymorphisms in Sepsis and Survival: A Pilot Study and In Silico Analysis

Sepsis is a serious infection-induced syndrome with serious ramifications, especially in intensive care units. Global concern motivated the investigation of the role of related genes’ polymorphism in predicting the liability to infection, sepsis, septic shock and survival. Among these genes is the gene encoding mannose-binding lectin (MBL), with its remarkable importance in the immune system. However, the previous studies showed conflicting results and ambiguity that urged us to engage with this issue in the Egyptian population. Prediction of functional and structural impacts of single nucleotide polymorphisms (SNPs) was done using in silico methods. A prospective observational study was conducted in intensive care units; one hundred and thirty patients were followed up. Genotyping was performed using real-time polymerase chain reaction (RT-PCR) technology. MBL SNPs showed a remarkable high frequency in our population, as well. No significant association was found between MBL2 genotypes and any of our analyses (sepsis, septic shock and survival). Only septic shock and age were independently associated with time of survival by Cox regression analysis. Our study may confirm the redundancy of MBL and the absence of significant impact on sepsis liability and mortality in adult patients.

Targeting the complement system in bacterial meningitis

Bacterial meningitis is most commonly caused by Streptococcus pneumoniae and Neisseria meningitidis and continues to pose a major public health threat. Morbidity and mortality of meningitis are driven by an uncontrolled host inflammatory response. This comprehensive update evaluates the role of the complement system in upregulating and maintaining the inflammatory response in bacterial meningitis. Genetic variation studies, complement level measurements in blood and CSF, and experimental work have together led to the identification of anaphylatoxin C5a as a promising treatment target in bacterial meningitis. In animals and patients with pneumococcal meningitis, the accumulation of neutrophils in the CSF was mainly driven by C5-derived chemotactic activity and correlated positively with disease severity and outcome. In murine pneumococcal meningitis, adjunctive treatment with C5 antibodies prevented brain damage and death. Several recently developed therapeutics target C5 conversion, C5a, or its receptor C5aR. Caution is warranted because treatment with C5 antibodies such as eculizumab also inhibits the formation of the membrane attack complex, which may result in decreased meningococcal killing and increased meningococcal disease susceptibility. The use of C5a or C5aR antagonists to specifically target the harmful anaphylatoxins-induced effects, therefore, are most promising and present opportunities for a phase 2 clinical trial.

Host genetic variability and pneumococcal disease: a systematic review and meta-analysis

Background

Pneumonia, sepsis, meningitis, and empyema due to Streptococcus pneumoniae is a major cause of morbidity and mortality. We provide a systemic overview of genetic variants associated with susceptibility, phenotype and outcome of community acquired pneumococcal pneumonia (CAP) and invasive pneumococcal disease (IPD).

Methods

We searched PubMed for studies on the influence of host genetics on susceptibility, phenotype, and outcome of CAP and IPD between Jan 1, 1983 and Jul 4, 2018. We listed methodological characteristics and when genetic data was available we calculated effect sizes. We used fixed or random effect models to calculate pooled effect sizes in the meta-analysis.

Results

We identified 1219 studies of which 60 studies involving 15,358 patients were included. Twenty-five studies (42%) focused on susceptibility, 8 (13%) on outcome, 1 (2%) on disease phenotype, and 26 (43%) on multiple categories. We identified five studies with a hypothesis free approach of which one resulted in one genome wide significant association in a gene coding for lincRNA with pneumococcal disease susceptibility. We performed 17 meta-analyses of which two susceptibility polymorphisms had a significant overall effect size: variant alleles of MBL2 (odds ratio [OR] 1·67, 95% confidence interval [CI] 1·04–2·69) and a variant in CD14 (OR 1·77, 95% CI 1·18–2·66) and none of the outcome polymorphisms.

Conclusions

Studies have identified several host genetics factors influencing risk of pneumococcal disease, but many result in non-reproducible findings due to methodological limitations. Uniform case definitions and pooling of data is necessary to obtain more robust findings.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0572-x) contains supplementary material, which is available to authorized users.

FcγRIIa defunctioning polymorphism in paediatric patients with renal allograft

Introduction

Fc gamma receptor (FcγR) IIa is considered the most widely distributed of the three classes of Fc receptors, and it expresses an allelic polymorphism. This type of polymorphism may modify the immune response and may be an important factor for some diseases. The aim of the study reported herein was to evaluate the association between the FcγRIIa polymorphism and susceptibility to both end-stage renal disease (ESRD) and acute kidney graft rejection (AR) in children who have undergone renal transplantation.

Material and methods

The study evaluated 70 children who had undergone transplantation and 60 healthy subjects. AR was observed in 25 children.

Results

FcγRIIa genotypes and alleles were significantly different between transplantation patients and the control group. The assessment for FcγR of the groups in which AR was present showed that there was only a risk of having an acute rejection in homozygous genotype RR.

Conclusions

FcγRIIa RR genotype and allele frequency was increased in paediatric renal transplant recipients. The present findings showed that FcγRIIa genotype may be related to ESRD disease susceptibility, and FcγRIIa polymorphisms seemed to affect AR.

Streptococcus pneumoniae and chronic endobronchial infections in childhood

Streptococcus pneumoniae (pneumococcus) is the main cause of bacterial pneumonia worldwide and has been studied extensively in this context. However, its role in chronic endobronchial infections and accompanying lower airway neutrophilic infiltration has received little attention. Severe and recurrent pneumonia are risk factors for chronic suppurative lung disease (CSLD) and bronchiectasis; the latter causes considerable morbidity and, in some populations, premature death in children and adults. Protracted bacterial bronchitis (PBB) is another chronic endobronchial infection associated with substantial morbidity. In some children, PBB may progress to bronchiectasis. Although nontypeable Haemophilus influenzae is the main pathogen in PBB, CSLD and bronchiectasis, pneumococci are isolated commonly from the lower airways of children with these diagnoses. Here we review what is known currently about pneumococci in PBB, CSLD and bronchiectasis, including the importance of pneumococcal nasopharyngeal colonization and how persistence in the lower airways may contribute to the pathogenesis of these chronic pulmonary disorders. Antibiotic treatments, particularly long-term azithromycin therapy, are discussed together with antibiotic resistance and the impact of pneumococcal conjugate vaccines. Important areas requiring further investigation are identified, including immune responses associated with pneumococcal lower airway infection, alone and in combination with other respiratory pathogens, and microarray serotyping to improve detection of carriage and infection by multiple serotypes. Genome wide association studies of pneumococci from the upper and lower airways will help identify virulence and resistance determinants, including potential therapeutic targets and vaccine antigens to treat and prevent endobronchial infections. Much work is needed, but the benefits will be substantial.

Clinical significance of the single nucleotide polymorphism TLR2 R753Q in heart transplant recipients at risk for cytomegalovirus disease

BACKGROUND

The toll-like receptor 2 (TLR2) is a significant component of innate immunity against cytomegalovirus (CMV) infection but information on the clinical significance of the single nucleotide polymorphism (SNP) (R753Q) is conflicting.

OBJECTIVES

The inconsistent observations of the immunological and clinical significance of the TLR2 R753Q polymorphism for CMV infection indicates the influence of confounders.

STUDY DESIGN

The presence of the TLR2 polymorphism was determined by a genotyping assay of 175 HTX patients and 281 healthy blood donors and evaluated in relation to selected virological and clinical parameters.

RESULTS

Relative frequency of TLR2 polymorphism was similar in HTX patients and blood donors (homozygous wild-type, 94.3% vs. 94.0%; heterozygous, 5.1% vs. 5.7%; homozygous mutated, <1%). CMV viremia was detectable in 108 (61.7%) of HTX patients. The TLR2 polymorphism was neither associated with occurrence or level of CMV infection nor with survival, graft failure or rejection, or CMV serostatus of patient before transplantation. Nevertheless, CMV viremia occurred in 83.1% of R+/D+, 77.1% of R+/D-, and 64.3% of R-/D+ patients. Time of first CMV viremia was in R-/D+ patients later than in CMV-seropositive patients (median, 182days versus 23 days; P<0.001) corresponding to the duration of antiviral prophylaxis in R-/D+ patients.

CONCLUSIONS

The TLR2 R753Q polymorphism is extremely rare in the general population and HTX patients. Screening for this risk factor of CMV disease may not be cost-effective in contrast to testing for CMV viremia.

The role of genetics and antibodies in sepsis

During the course of sepsis when immunosuppression predominates, the concentrations of circulating immunoglobulins (IGs) are decreased and this is associated with adverse outcomes. The production of IGs as response to invasive bacterial pathogens takes place through a complex pathway starting from the recognition of the antigen (Ag) by innate immune cells that process and present Ags to T cells. The orchestration of T-helper (Th) lymphocyte responses directs specific B cells and ends with the production of IGs by plasma cells. All molecules implicated in this process are encoded by genes bearing single nucleotide polymorphisms (SNPs). Meta-analysis of case-control studies have shown that the carriage of minor frequency SNPs of CD14, TLR2 and TNF is associated with increased sepsis risk. The ambiguity of results of clinical trials studying the clinical efficacy of exogenous IG administration in sepsis suggests that efficacy of treatment should be considered after adjustment for SNPs of all implicated genes in the pathway of IG production.

Virulence Factors of Streptococcus pneumoniae. Comparison between African and French Invasive Isolates and Implication for Future Vaccines

Background

Many surface proteins thought to promote Streptocococcus pneumoniae virulence have recently been discovered and are currently being considered as future vaccine targets. We assessed the prevalence of 16 virulence genes among 435 S. pneumoniae invasive isolates from France and the “African meningitis belt” region, with particular focus on serotype 1 (Sp1), to compare their geographical distribution, assess their association with site of infection and evaluate their potential interest as new vaccine candidates.

Methods

Detection by PCR of pspA (+families), pspC (+pspC.4), pavA, lytA, phtA,B,D,E, nanA,B,C, rrgA (Pilus-1), sipA (Pilus-2), pcpA and psrp was performed on all isolates, as well as antibiotic resistance testing and MLVA typing (+MLST on 54 representative strains). Determination of ply alleles was performed by sequencing (Sp1 isolates).

Results

MLVA and virulence genes profiles segregated Sp1 isolates into 2 groups that followed continent distribution. The ply allele 5 and most of the genes that were variable (nanC, Pilus-2, psrp, pcpA, phtD) were present in the French Sp1 isolates (PMEN clone Sweden¹-28, ST306) but absent from the African ones. Whereas all African Sp1 isolates clustered into a single MLST CC (CC217), MLVA distinguished two CCs that followed temporal evolution. Pilus-2 and psrp were more prevalent in bacteraemic pneumonia yielded isolates and phtB in meningitis-related isolates. Considering vaccine candidates, phtD was less prevalent than anticipated (50%) and pcpA varied importantly between France and Africa (98% versus 34%). Pilus-1 was carried by 7-11% of isolates and associated with β-lactams resistance.

Conclusions

Most virulence genes were carried by the European ST306 clone but were lacking on Sp1 isolates circulating in the African meningitis belt, where a more serious pattern of infection is observed. While virulence proteins are now considered as vaccine targets, the geographical differences in their prevalence could affect the efficacy expected from future vaccines.

Post-infectious bronchiolitis obliterans and mannose-binding lectin insufficiency in Argentinean children

BACKGROUND AND OBJECTIVE

Post-infectious bronchiolitis obliterans (PIBO) is a severe disorder following acute lower pulmonary infection in young children, especially caused by adenovirus. Mannose-binding lectin (MBL) deficiency arising from polymorphisms in the coding and non-coding region on the MBL2 gene has been associated with more frequent and severe respiratory infections. Our aim was to evaluate the influence of MBL variants in the susceptibility and evolution of children with PIBO.

METHODS

One hundred eleven children with PIBO diagnosis were studied. The coding A, B, D and X promoter variants of MBL2 gene were assessed by PCR-RFLP. B and D alleles were pooled as O. The combined genotypes A/A and YA/O were grouped as sufficient MBL (sMBL), and O/O and XA/O as insufficient MBL (iMBL) groups. To evaluate the frequency of MBL2 polymorphisms in the general population, we studied DNA samples from 127 healthy donors from the blood bank of the hospital (control group).

RESULTS

iMBL variants were significantly more frequent in PIBO children compared with controls (21.6% vs 10.2%, P = 0.01). PIBO patients with iMBL required intensive care unit (P = 0.001) and mechanical assistance at the moment of viral injury (P = 0.001) more frequently than those with sMBL.

CONCLUSIONS

Insufficiency of MBL was more common in PIBO children than in healthy controls. This genetic condition was significantly associated with more severe initial disease, illustrating the relevance of innate immune defence factors prior to the maturation of the adaptative immune system.

[Prevention of Streptococcus pneumoniae (pneumococcal) infections in adults]

Infections caused by Streptococcus pneumoniae (pneumococcus) are still meaning a serious health problem, about 40% of community acquired pneumonia (CAP) is due to pneumococcal bacteria in adults requiring hospitalization. The incidence and mortality rate of pneumococcal infections is increasing in the population above 50 years of age. Certain congenital and acquired immunocompromised conditions make the individual susceptible for pneumococcal infection and other chronic comorbidities should be considered as a risk factor as well, such as liver and renal diseases, COPD, diabetes mellitus. Lethality of severe pneumococcal infections with bacteraemia still remains about 12% despite adequate antimicrobial therapy in the past 60 years. Underestimation of pneumococcal infections is mainly due to the low sensitivity of diagnostic tools and underuse of bacteriological laboratory confirmation methods. 13-valent pneumococcal conjugate vaccine (PCV-13) became available recently beyond the 23-valent polysacharide vaccine (PPV-23) which has been using for a long time.The indication and proper administration of the two vaccines are based on international recommendations and vaccination guideline published by National Centre for Epidemiology (NCE):Pneumococcal vaccination is recommended for: Every person above 50 years of age. Patients of all ages with chronic diseases who are susceptible for severe pneumococcal infections: respiratory (COPD), heart, renal, liver disease, diabetes, or patients under immunsuppressive treatment. Smokers regardless of age and comorbidities. Cochlear implants, cranial-injured patients. Patients with asplenia.Recommendation for administration of the two different vaccines:Adults who have not been immunized previously against pneumococcal disease must be vaccinated with a dose of 13-valent pneumococcal conjugate vaccine first. This protection could be extended with administration of 23-valent pneumococcal polysaccharide vaccine at least two month later. Adults who have been immunized previously, but above 65 years of age, with a 23-valent polysaccharide vaccine are recommended to get one dose of conjugate vaccine at least one year later. Adults who have been immunized previously, but under 65 years of age, with a 23-valent polysaccharide vaccine are recommended to get one dose of conjugate vaccine at least one year later. After a minimal interval of two months one dose of 23-valent pneumococcal polysaccharide vaccine is recommended if at least 5 years have elapsed since their previous PPSV23 dose. Vaccination of immuncompromised patients (malignancy, transplantation, etc.) and patients with asplenia should be defined by vaccinology specialists. Pneumococcal vaccines may be administered concommitantly or any interval with other vaccines.

Polymorphisms of Toll-like receptors (TLR2 and TLR4) are associated with the risk of infectious complications in acute myeloid leukemia

Infectious complications continue to be one of the major causes of morbidity and mortality in patients with acute myeloid leukemia (AML). Several single-nucleotide polymorphisms (SNPs) of Toll-like receptors (TLRs) can affect the genetic susceptibility to infections or even sepsis. We sought to investigate the impact of different SNPs on the incidence of developing sepsis and pneumonia in patients with newly diagnosed AML following induction chemotherapy. We analyzed three SNPs in the TLR2 (Arg753Gln) and TLR4 (Asp299Gly and Thr399Ile) gene in a cohort of 155 patients with AML who received induction chemotherapy. The risk of developing sepsis and pneumonia was assessed by multiple logistic regression analyses. The presence of the TLR2 Arg753Gln polymorphism was significantly associated with pneumonia in AML patients (odds ratio (OR): 10.78; 95% confidence interval (CI): 2.0-58.23; P=0.006). Furthermore, the cosegregating TLR4 polymorphisms Asp299Gly and Thr399Ile were independent risk factors for the development of both sepsis and pneumonia (OR: 3.55; 95% CI: 1.21-10.4, P=0.021 and OR: 3.57, 95% CI: 1.3-9.86, P=0.014, respectively). To our best knowledge, this study represents the first analysis demonstrating that polymorphisms of TLR2 and TLR4 influence the risk of infectious complications in patients with AML undergoing induction chemotherapy.

Soluble mediators regulating immunity in early life

Soluble factors in blood plasma have a substantial impact on both the innate and adaptive immune responses. The complement system, antibodies, and anti-microbial proteins and peptides can directly interact with potential pathogens, protecting against systemic infection. Levels of these innate effector proteins are generally lower in neonatal circulation at term delivery than in adults, and lower still at preterm delivery. The extracellular environment also has a critical influence on immune cell maturation, activation, and effector functions, and many of the factors in plasma, including hormones, vitamins, and purines, have been shown to influence these processes for leukocytes of both the innate and adaptive immune systems. The ontogeny of plasma factors can be viewed in the context of a lower effectiveness of immune responses to infection and immunization in early life, which may be influenced by the striking neonatal deficiency of complement system proteins or enhanced neonatal production of the anti-inflammatory cytokine IL-10, among other ontogenic differences. Accordingly, we survey here a number of soluble mediators in plasma for which age-dependent differences in abundance may influence the ontogeny of immune function, particularly direct innate interaction and skewing of adaptive lymphocyte activity in response to infectious microorganisms and adjuvanted vaccines.

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.

The role of mannose-binding lectin in severe sepsis and septic shock

Severe sepsis and septic shock are a primary cause of death in patients in intensive care unit (ICU). Investigations upon genetic susceptibility profile to systemic complications during severe infections are a field of increasing scientific interest. Particularly when adaptive immune system is compromised or immature, innate immunity plays a key role in the immediate defense against invasive pathogens. Mannose-binding lectin (MBL) is a serum protein that recognizes a wide range of pathogenic microorganisms and activates complement cascade via the antibody-independent pathway. More than 30% of humans harbor mutations in MBL gene (MBL2) resulting in reduced plasmatic levels and activity. Increased risk of infection acquisition has been largely documented in MBL-deficient patients, but the real impact of this form of innate immunosuppression upon clinical outcome is not clear. In critically ill patients higher incidence and worse prognosis of severe sepsis/septic shock appear to be associated with low-producers haplotypes. However an excess of MBL activation might be also harmful due to the possibility of an unbalanced proinflammatory response and an additional host injury. Strategies of replacement therapies in critically ill patients with severe infections are under investigation but still far to be applied in clinical practice.