Meningococcal disease: A paradigm of type‐IV pilus dependent pathogenesis

Neisseria meningitidis (meningococcus) is a Gram‐negative bacterium responsible for two devastating forms of invasive diseases: purpura fulminans and meningitis. Interaction with both peripheral and cerebral microvascular endothelial cells is at the heart of meningococcal pathogenesis. During the last two decades, an essential role for meningococcal type IV pili in vascular colonisation and disease progression has been unravelled. This review summarises 20 years of research on meningococcal type IV pilus‐dependent virulence mechanisms, up to the identification of promising anti‐virulence compounds that target type IV pili.     

Molecular typing of meningococci: recommendations for target choice and nomenclature

The diversity and dynamics of Neisseria meningitidis populations generate a requirement for high resolution, comprehensive, and portable typing schemes for meningococcal disease surveillance. Molecular approaches, specifically DNA amplification and sequencing, are the methods of choice for various reasons, including: their generic nature and portability, comprehensive coverage, and ready implementation to culture negative clinical specimens. The following target genes are recommended: (1) the variable regions of the antigen-encoding genes porA and fetA and, if additional resolution is required, the porB gene for rapid investigation of disease outbreaks and investigating the distribution of antigenic variants; (2) the seven multilocus sequence typing loci-these data are essential for the most effective national, and international management of meningococcal disease, as well as being invaluable in studies of meningococcal population biology and evolution. These targets have been employed extensively in reference laboratories throughout the world and validated protocols have been published. It is further recommended that a modified nomenclature be adopted of the form: serogroup: PorA type: FetA type: sequence type (clonal complex), thus: B: P1.19,15: F5-1: ST-33 (cc32).     

An OMV Vaccine Derived from a Capsular Group B Meningococcus with Constitutive FetA Expression: Preclinical Evaluation of Immunogenicity and Toxicity

Following the introduction of effective protein-polysaccharide conjugate vaccines against capsular group C meningococcal disease in Europe, meningococci of capsular group B remain a major cause of death and can result in debilitating sequelae. The outer membrane proteins PorA and FetA have previously been shown to induce bactericidal antibodies in humans. Despite considerable antigenic variation among PorA and FetA OMPs in meningococci, systematic molecular epidemiological studies revealed this variation is highly structured so that a limited repertoire of antigenic types is congruent with the hyperinvasive meningococcal lineages that have caused most of the meningococcal disease in Europe in recent decades. Here we describe the development of a prototype vaccine against capsular group B meningococcal infection based on a N. meningitidis isolate genetically engineered to have constitutive expression of the outer membrane protein FetA. Deoxycholate outer membrane vesicles (dOMVs) extracted from cells cultivated in modified Frantz medium contained 21.8% PorA protein, 7.7% FetA protein and 0.03 μg LPS per μg protein (3%). The antibody response to the vaccine was tested in three mouse strains and the toxicological profile of the vaccine was tested in New Zealand white rabbits. Administration of the vaccine, MenPF-1, when given by intramuscular injection on 4 occasions over a 9 week period, was well tolerated in rabbits up to 50 μg/dose, with no evidence of systemic toxicity. These data indicated that the MenPF-1 vaccine had a toxicological profile suitable for testing in a phase I clinical trial.     

综述与专论: 少突胶质细胞病——佩梅病的临床特点及致病机制

佩梅病（Pelizaeus-Merzbacher disease,PMD）是髓鞘形成低下性脑白质营养不良疾病中最常见的一种,其临床特点主要表现为发育落后尤其是大运动落后、眼震、肌张力低下等。其致病机制主要为脑白质髓鞘形成细胞-少突胶质细胞发生病理性改变从而导致髓鞘形成不良,相应理论基础包括以往研究中PLP1点突变通过影响PLP1/DM20寡聚体的形成,进而影响少突胶质细胞的存活,髓鞘分子结构的形成等;而PLP1重复突变则使少突胶质细胞及髓鞘脂的发育停止。近年来对细胞器互作网络（organelle interaction network,OIN）的研究进一步揭示了PLP1突变的致病机制：PLP1点突变通过影响PLP1蛋白上膜进而影响少突胶质细胞髓鞘化。PLP1重复突变则改变内质网线粒体间的连接,继而影响线粒体的形态功能等产生致病作用。目前已有相关研究表明,一些小分子化合物或药物例如胆固醇、吡拉西坦等以及基因疗法在动物体内对PMD临床症状有改善作用,其在PMD 患者体内的疗效有待进一步证实。     

Molecular analysis of actinorhizal symbiotic systems: Progress to date

The application of molecular tools to questions related to the genetics, ecology and evolution of actinorhizal symbiotic systems has been especially fruitful during the past two years. Host plant phylogenies based on molecular data have revealed markedly different relationships among host plants than have previously been suspected and have contributed to the development of new hypotheses on the origin and evolution of actinorhizal symbiotic systems. Molecular analyses of host plant gene expression in developing nodules have confirmed the occurrence of nodulin proteins and in situ hybridization techniques have been successfully adapted to permit the study of the spatial and temporal patterns of gene expression within actinorhizal nodules. The use of heterologous probes in combination with nucleotide sequence analysis have allowed a number of nif genes to be mapped on the Frankia chromosome which will ultimately contribute to the development of hypotheses related to nif gene regulation in Frankia. The use of both 16S and 23S rDNA nucleotide sequences has allowed the construction of phylogenetic trees that can be tested for congruence with symbiotic characters. In addition the development of Frankia-specific gene probes and amplification primers have contributed to studies on the genetic diversity and distribution of Frankia in the soil.     

Imaging of disease dynamics during meningococcal sepsis

Neisseria meningitidis is a human pathogen that causes septicemia and meningitis with high mortality. The disease progression is rapid and much remains unknown about the disease process. The understanding of disease development is crucial for development of novel therapeutic strategies and vaccines against meningococcal disease. The use of bioluminescent imaging combined with a mouse disease model allowed us to investigate the progression of meningococcal sepsis over time. Injection of bacteria in blood demonstrated waves of bacterial clearance and growth, which selected for Opa-expressing bacteria, indicating the importance of this bacterial protein. Further, N. meningitidis accumulated in the thyroid gland, while thyroid hormone T4 levels decreased. Bacteria reached the mucosal surfaces of the upper respiratory tract, which required expression of the meningococcal PilC1 adhesin. Surprisingly, PilC1 was dispensable for meningococcal growth in blood and for crossing of the blood-brain barrier, indicating that the major role of PilC1 is to interact with mucosal surfaces. This in vivo study reveals disease dynamics and organ targeting during meningococcal disease and presents a potent tool for further investigations of meningococcal pathogenesis and vaccines in vivo. This might lead to development of new strategies to improve the outcome of meningococcal disease in human patients.     

Backbone and side-chain assignment of the lipidated and non-lipidated forms of the meningococcal outer membrane protein LP2086

LP2086 is a lipidated outer membrane protein from Neisseria meningitidis that elicits bactericidal antibodies and represents a promising vaccine candidate against meningococcal infections. Here we report the backbone and side-chain assignment for two forms of LP2086: non-lipidated in aqueous buffer and the lipidated protein in micellar solution. Ethical standards  All experiments described comply with the current laws of the United States of America. The authors declare that they have no conflict of interest     

Farmer’s Lung Disease and Microbiological Composition of Hay: A Case–Control Study

Previous studies performed in France have suggested that handling hay contaminated with high amounts of moulds, and especially Absidia corymbifera and Eurotium amstelodami, may favour farmer’s lung disease. The circumstances favouring farmer’s lung disease and the distinctive microbiological composition of hay samples that provoke attacks need to be specified. We present a case–control study which investigates the agricultural practices and the microbiological composition of hay handled in patients with farmer’s lung disease as compared to those of a representative control population. Ten cases identified the hay they were handling at the onset of symptoms. The location, type of farm and working conditions were similar to those of the control farms. Conversely, the microbiological composition of hay differed, with significantly higher amounts of E. amstelodami (P < 0.01), A. corymbifera (P = 0.003), mesophilic Streptomyces (P < 0.01), thermophilic Streptomyces (P < 0.01) and Saccharomonospora viridis (P < 0.01) than in the control population. Our results demonstrate that hay identified by patients as having a harmful effect is characterized by a higher total amount of microorganisms, notably five microorganisms that seem discriminative. Mean concentrations are 2- to 115-fold higher in hay suspected to cause symptoms than in hay from a representative panel of farms. Handling hay with high amounts of these five microorganisms constitutes a risk factor for farmer’s lung disease that should be considered for the development of prophylactic measures.     

Evolutionary and genomic insights into meningococcal biology

Epidemic disease caused by Neisseria meningitidis, the meningococcus, has been recognized for two centuries, but remains incompletely controlled and understood. There have been dramatic reductions in serogroup A and C meningococcal disease following the introduction of protein-polysaccharide conjugate vaccines, but there is currently no comprehensive vaccine against serogroup B meningococci. Genetic analyses of meningococcal populations have provided many insights into the biology, evolution and pathogenesis of this important pathogen. The meningococcus, and its close relative the gonococcus, are the only pathogenic members of the genus Neisseria, and the invasive propensity of meningococci varies widely, with approximately a dozen 'hyperinvasive lineages' responsible for most disease. Despite this, attempts to identify a 'pathogenome', a subset of genes associated with the invasive phenotypes, have failed; however, genome-wide studies of representative meningococcal isolates using high-throughput sequencing are beginning to provide details on the relationship of invasive phenotype and genotype in this fascinating organism and how this relationship has evolved.     

Effectiveness of antibiotics in preventing meningococcal disease after a case: systematic review

Objective To summarise the evidence for the role of antibiotics in preventing further cases of meningococcal disease through chemoprophylaxis given to the index patient, household contacts, and children in day care settings after a single case.Design Systematic review.Methods Studies were identified by searching Embase (1983-2003), Medline (1965-2003), and CAB Health (1973-2003) and by contacting the World Health Organization and the European meningococcal disease surveillance network and examining references of identified papers. The review included all studies with at least 10 cases in which outcomes were compared between treated and untreated groups.Main outcome measure Subsequent cases of meningococcal disease 1-30 days after onset of disease in the index patient.Results Four observational studies and one small trial met the inclusion criteria. Meta-analysis of studies on chemoprophylaxis given to household contacts showed a significant reduction in risk (risk ratio 0.11, 95% confidence interval 0.02 to 0.58). The number needed to treat to prevent a case was estimated as 218 (121 to 1135). Primary outcome data were not available in studies of chemoprophylaxis given to the index patient: when prophylaxis had not been given, rate of carriage after discharge from hospital was estimated as 3% (0 to 6), probably an underestimate of the true rate. No studies of chemoprophylaxis in day care settings were identified that met the inclusion criteria.Conclusion There have been no high quality experimental trials looking at control policies for meningococcal disease. The best available evidence is from retrospective studies. The risk of meningococcal disease in household contacts of a patient can be reduced by an estimated 89% if they take antibiotics known to eradicate meningococcal carriage. Chemoprophylaxis should be recommended for the index patient and all household contacts.     

Phase variation of Opa proteins of <Emphasis Type="BoldItalic">Neisseria meningitidis</Emphasis> and the effects of bacterial transformation

Opa proteins are major proteins involved in meningococcal colonization of the nasopharynx and immune interactions. Opa proteins undergo phase variation (PV) due to the presence of the 5′-CTCTT-3′ coding repeat (CR) sequence. The dynamics of PV of meningococcal Opa proteins is unknown. Opa PV, including the effect of transformation on PV, was assessed using a panel of Opa-deficient strains of Neisseria meningitidis. Analysis of Opa expression from UK disease-causing isolates was undertaken. Different opa genes demonstrated variable rates of PV, between 6.4 ×10^–4 and 6.9 ×10^–3 per cell per generation. opa genes with a longer CR tract had a higher rate of PV (r ²=0.77, p=0.1212). Bacterial transformation resulted in a 180-fold increase in PV rate. The majority of opa genes in UK disease isolates (315/463, 68.0%) were in the ‘on’ phase, suggesting the importance of Opa proteins during invasive disease. These data provide valuable information for the first time regarding meningococcal Opa PV. The presence of Opa PV in meningococcal populations and high expression of Opa among invasive strains likely indicates the importance of this protein in bacterial colonization in the human nasopharynx. These findings have potential implications for development of vaccines derived from meningococcal outer membranes.     

A new structural class of S-adenosylhomocysteine hydrolase inhibitors

Effective inhibitors of S-adenosylhomocysteine hydrolase hold promise towards becoming useful therapeutic agents. Since most efforts have focused on the development of nucleoside analog inhibitors, issues regarding bioavailability and selectivity have been major challenges. Considering the marine sponge metabolite ilimaquinone was found to be a competitive inhibitor of S-adenosylhomocysteine hydrolase, new opportunities for developing selective new inhibitors of this enzyme have become available. Based on the activities of various hybrid analogs, SAR studies, pharmacophore modeling, and computer docking studies have lead to a predictive understanding of ilimaquinone’s S-adenosylhomocysteine hydrolase inhibitory activities. These studies have allowed for the design and preparation of simplified structural variants possessing new furanoside bioisosteres with 100-fold greater inhibitory activities than that of the natural product.     

Protein C promoter polymorphisms associate with sepsis in children with systemic meningococcemia

Meningococcal disease may present as sepsis, meningitis or a combination of both. Protein C (PC) is an important regulator of thrombin activity. Two polymorphisms in the promoter region of PC (C-1654T, A-1641G) have been shown to affect PC levels. In patients with meningococcal sepsis, low PC levels have been correlated with increased severity and poor outcome. We established a multicenter case-control study to determine whether PC promoter polymorphisms are associated with occurrence and outcome of meningococcal disease and sepsis. 288 previously healthy children with meningococcal infection from 97 pediatric hospitals in Germany, Switzerland, Italy, and Austria and 309 healthy controls were included in the study. A strong age-dependant effect was found. Patients younger than 1 year carried significantly more often the CG-CG genotype than healthy controls (28.6% vs. 17.8%, P = 0.04). Carriers of the CG allele showed a 3.43-fold increased odds ratio (OR) to develop sepsis (95% CI: 1.05-11.20; 85.7% vs. 63.6%, P = 0.036). The TA-TA genotype conferred a protective role for the development of sepsis (P = 0.017) with a Haldane OR of 0.09 (95% CI: 0.01-0.94). Systolic blood pressure values were significantly decreased in patients carrying the CG-CG genotype (70 vs. 86 mmHg, P = 0.005), and the need for adrenergic support significantly higher (70% vs. 26%, P = 0.018), resulting in an OR of 6.61 (95% CI: 1.28-34.14). These findings show that in young children PC promoter genotype is associated with susceptibility for meningococcal disease, the development of meningococcal sepsis, lower blood pressure, and need for adrenergic support.     

Association of secondhand smoke exposure with pediatric invasive bacterial disease and bacterial carriage: a systematic review and meta-analysis

Background

A number of epidemiologic studies have observed an association between secondhand smoke (SHS) exposure and pediatric invasive bacterial disease (IBD) but the evidence has not been systematically reviewed. We carried out a systematic review and meta-analysis of SHS exposure and two outcomes, IBD and pharyngeal carriage of bacteria, for Neisseria meningitidis (N. meningitidis), Haemophilus influenzae type B (Hib), and Streptococcus pneumoniae (S. pneumoniae).

Methods and Findings

Two independent reviewers searched Medline, EMBASE, and selected other databases, and screened articles for inclusion and exclusion criteria. We identified 30 case-control studies on SHS and IBD, and 12 cross-sectional studies on SHS and bacterial carriage. Weighted summary odd ratios (ORs) were calculated for each outcome and for studies with specific design and quality characteristics. Tests for heterogeneity and publication bias were performed. Compared with those unexposed to SHS, summary OR for SHS exposure was 2.02 (95% confidence interval [CI] 1.52–2.69) for invasive meningococcal disease, 1.21 (95% CI 0.69–2.14) for invasive pneumococcal disease, and 1.22 (95% CI 0.93–1.62) for invasive Hib disease. For pharyngeal carriage, summary OR was 1.68 (95% CI, 1.19–2.36) for N. meningitidis, 1.66 (95% CI 1.33–2.07) for S. pneumoniae, and 0.96 (95% CI 0.48–1.95) for Hib. The association between SHS exposure and invasive meningococcal and Hib diseases was consistent regardless of outcome definitions, age groups, study designs, and publication year. The effect estimates were larger in studies among children younger than 6 years of age for all three IBDs, and in studies with the more rigorous laboratory-confirmed diagnosis for invasive meningococcal disease (summary OR 3.24; 95% CI 1.72–6.13).

Conclusions

When considered together with evidence from direct smoking and biological mechanisms, our systematic review and meta-analysis indicates that SHS exposure may be associated with invasive meningococcal disease. The epidemiologic evidence is currently insufficient to show an association between SHS and invasive Hib disease or pneumococcal disease. Because the burden of IBD is highest in developing countries where SHS is increasing, there is a need for high-quality studies to confirm these results, and for interventions to reduce exposure of children to SHS. Please see later in the article for the Editors'' Summary     

Evidence of Positive Darwinian Selection in Putative Meningococcal Vaccine Antigens

Meningococcal meningitidis is a life-threatening disease. In Europe and the United States the majority of cases are caused by virulent meningococcal strains belonging to serogroup B. Presently there is no effective vaccine against serogroup B strains, as traditional vaccine antigens such as polysaccharide capsules are unusable as they lead to autoimmunity. The year 2000 saw the publication of the complete genome of Neisseria meningitidis MC58, a virulent serogroup B bacterium. Working in conjunction with the sequencing project, researchers endeavored to locate highly conserved membrane-associated proteins that elicit an immune response. It is hoped that these proteins will provide a basis for novel vaccines against serogroup B strains. A number of potential vaccine antigens have been located and are presently in phase I clinical trials. Recently many reports pertaining to the evidence of positive Darwinian selection in membrane proteins of pathogens have been reported. This study utilized in silico methods to test for evidence of historical positive Darwinian selection in seven such vaccine candidates. We found that two of these proteins show signatures of adaptive evolution, while the remaining proteins show evidence of strong purifying selection. This has significant implications for the design of a vaccine against serogroup B strains, as it has been shown that vaccines that target epitopes that are under strong purifying selection are better than those that target variable epitopes.[Reviewing Editor: Rasmus Nielsen]     

Genome Sequence of a Neisseria meningitidis Capsule Null Locus Strain from the Clonal Complex of Sequence Type 198

Neisseria meningitidis is a commensal and accidental pathogen exclusively of humans. Although the production of polysaccharide capsules is considered to be essential for meningococcal virulence, there have been reports of constitutively unencapsulated strains causing invasive meningococcal disease (IMD). Here we report the genome sequence of a capsule null locus (cnl) strain of sequence type 198 (ST-198), which is found in half of the reported cases of IMD caused by cnl meningococcal strains.     

CRISPR/Cas系统与结核病防控新措施相关性研究

结核分枝杆菌(Mycobacterium tuberculosis,MTB,以下简称结核杆菌)感染引起的结核病仍然是严重影响人类健康全球性重大传染病。全球约1/4人口是结核杆菌的潜伏感染者。2019年,世界卫生组织(Worldhealthorganization,WHO)报道全球约150万人死于结核病。深入研究结核杆菌生物学有望为结核病防控提供新工具。成簇规律性间隔短回文重复(Clusteredregularlyinterspacedshort palindromic repeats,CRISPR)/Cas是细菌免疫系统的重要成分,在结核杆菌等分枝杆菌中也广泛存在,同时,也是分枝杆菌基因编辑的重要工具。本文结合课题组研究工作,综述了结核杆菌III-A型CRISPR/Cas系统各组分的生物学功能以及与致病的相关性,CRISPR/Cas编辑工具在诊断治疗耐药结核杆菌和结核病防控新措施中的进展。     

Serological pattern consistent with infection with type I Toxoplasma gondii in mothers and risk of psychosis among adult offspring

Previous studies have shown that maternal antibodies to Toxoplasma measured during pregnancy are associated with an increased risk of schizophrenia and other psychoses in adult offspring. Recently, it has been recognized that different genotypes of Toxoplasma have distinct neuropathogenic potential. The objective of this study was to investigate whether parasite genotype is a contributing factor to disease risk. We have developed an enzyme-linked immunosorbent assay (ELISA) that uses polymorphic polypeptides specific to the three clonal parasite lineages and derived from three dense granule antigens, GRA5, GRA6 and GRA7. We used this assay to measure type-specific antibodies in the sera from 219 pregnant women whose children developed schizophrenia and affective psychotic illnesses in adult life, and 618 matched unaffected control mothers from three cohorts of the Collaborative Perinatal Project. We found that the offspring of mothers with a serological pattern consistent with Toxoplasma type І infection were at significantly increased risk for the development of psychoses as compared with the matched unaffected control mothers (odds ratio = 1.94; 95% confidence interval = 1.08–3.46; p = 0.03). The risk was particularly elevated for affective psychoses (OR = 5.24; 95% CI = 1.67–16.5; p = 0.005). In contrast, we did not find an association between maternal antibodies to other genotypes and risk of psychoses in the offspring. These findings suggest an influence of the parasite genotype on increased risk of psychosis and provide further support for a substantive role of Toxoplasma in the etiology of psychosis.     

Enhancing biological control of basal stem rot disease (<Emphasis Type="Italic">Ganoderma boninense</Emphasis>) in oil palm plantations

Basal Stem Rot (BSR) disease caused by Ganoderma boninense is the most destructive disease in oil palm, especially in Indonesia and Malaysia. The available control measures for BSR disease such as cultural practices and mechanical and chemical treatment have not proved satisfactory due to the fact that Ganoderma has various resting stages such as melanised mycelium, basidiospores and pseudosclerotia. Alternative control measures to overcome the Ganoderma problem are focused on the use of biological control agents and planting resistant material. Present studies conducted at Indonesian Oil Palm Research Institute (IOPRI) are focused on enhancing the use of biological control agents for Ganoderma. These activities include screening biological agents from the oil palm rhizosphere in order to evaluate their effectiveness as biological agents in glasshouse and field trials, testing their antagonistic activities in large scale experiments and eradicating potential disease inoculum with biological agents. Several promising biological agents have been isolated, mainly Trichoderma harzianum, T. viride, Gliocladium viride, Pseudomonas fluorescens, and Bacillus sp. A glasshouse and field trial for Ganoderma control indicated that treatment with T. harzianum and G. viride was superior to Bacillus sp. A large scale trial showed that the disease incidence was lower in a field treated with biological agents than in untreated fields. In a short term programme, research activities at IOPRI are currently focusing on selecting fungi that can completely degrade plant material in order to eradicate inoculum. Digging holes around the palm bole and adding empty fruit bunches have been investigated as ways to stimulate biological agents.