Late Repression of NF-κB Activity by Invasive but Not Non-Invasive Meningococcal Isolates Is Required to Display Apoptosis of Epithelial Cells

Meningococcal invasive isolates of the ST-11 clonal complex are most frequently associated with disease and rarely found in carriers. Unlike carriage isolates, invasive isolates induce apoptosis in epithelial cells through the TNF-α signaling pathway. While invasive and non-invasive isolates are both able to trigger the TLR4/MyD88 pathway in lipooligosaccharide (LOS)-dependant manner, we show that only non-invasive isolates were able to induce sustained NF-κB activity in infected epithelial cells. ST-11 invasive isolates initially triggered a strong NF-κB activity in infected epithelial cells that was abolished after 9h of infection and was associated with sustained activation of JNK, increased levels of membrane TNFR1, and induction of apoptosis. In contrast, infection with carriage isolates lead to prolonged activation of NF-κB that was associated with a transient activation of JNK increased TACE/ADAM17-mediated shedding of TNFR1 and protection against apoptosis. Our data provide insights to understand the meningococcal duality between invasiveness and asymptomatic carriage

Penicillin Binding Proteins as Danger Signals: Meningococcal Penicillin Binding Protein 2 Activates Dendritic Cells through Toll-Like Receptor 4

Neisseria meningitidis is a human pathogen responsible for life-threatening inflammatory diseases. Meningococcal penicillin-binding proteins (PBPs) and particularly PBP2 are involved in bacterial resistance to β-lactams. Here we describe a novel function for PBP2 that activates human and mouse dendritic cells (DC) in a time and dose-dependent manner. PBP2 induces MHC II (LOGEC50 = 4.7 µg/ml±0.1), CD80 (LOGEC50 = 4.88 µg/ml±0.15) and CD86 (LOGEC50 = 5.36 µg/ml±0.1). This effect was abolished when DCs were co-treated with anti-PBP2 antibodies. PBP2-treated DCs displayed enhanced immunogenic properties in vitro and in vivo. Furthermore, proteins co-purified with PBP2 showed no effect on DC maturation. We show through different in vivo and in vitro approaches that this effect is not due to endotoxin contamination. At the mechanistic level, PBP2 induces nuclear localization of p65 NF-kB of 70.7±5.1% cells versus 12±2.6% in untreated DCs and needs TLR4 expression to mature DCs. Immunoprecipitation and blocking experiments showed tha

Experimental Meningococcal Sepsis in Congenic Transgenic Mice Expressing Human Transferrin

Severe meningococcal sepsis is still of high morbidity and mortality. Its management may be improved by an experimental model allowing better understanding of its pathophysiology. We developed an animal model of meningococcal sepsis in transgenic BALB/c mice expressing human transferrin. We studied experimental meningococcal sepsis in congenic transgenic BALB/c mice expressing human transferrin by transcriptional profiling using microarray analysis of blood and brain samples. Genes encoding acute phase proteins, chemokines and cytokines constituted the largest strongly regulated groups. Dynamic bioluminescence imaging further showed high blood bacterial loads that were further enhanced after a primary viral infection by influenza A virus. Moreover, IL-1 receptor–associated kinase–3 (IRAK-3) was induced in infected mice. IRAK-3 is a negative regulator of Toll-dependant signaling and its induction may impair innate immunity and hence result in an immunocompromised state allowing bacterial survival and systemic spread during sepsis. This new approach should enable detailed analysis of the pathophysiology of meningococcal sepsis and its relationships with flu infection

Differential Modulation of TNF-α–Induced Apoptosis by Neisseria meningitidis

Infections by Neisseria meningitidis show duality between frequent asymptomatic carriage and occasional life-threatening disease. Bacterial and host factors involved in this balance are not fully understood. Cytopathic effects and cell damage may prelude to pathogenesis of isolates belonging to hyper-invasive lineages. We aimed to analyze cell–bacteria interactions using both pathogenic and carriage meningococcal isolates. Several pathogenic isolates of the ST-11 clonal complex and carriage isolates were used to infect human epithelial cells. Cytopathic effect was determined and apoptosis was scored using several methods (FITC-Annexin V staining followed by FACS analysis, caspase assays and DNA fragmentation). Only pathogenic isolates were able to induce apoptosis in human epithelial cells, mainly by lipooligosaccharide (endotoxin). Bioactive TNF-α is only detected when cells were infected by pathogenic isolates. At the opposite, carriage isolates seem to provoke shedding of the TNF-α receptor I (TNF-RI) from the surface that protect cells from apoptosis by chelating TNF-α. Ability to induce apoptosis and inflammation may represent major traits in the pathogenesis of N. meningitidis. However, our data strongly suggest that carriage isolates of meningococci reduce inflammatory response and apoptosis induction, resulting in the protection of their ecological niche at the human nasopharynx

Trends in invasive bacterial diseases during the first 2 years of the COVID-19 pandemic: analyses of prospective surveillance data from 30 countries and territories in the IRIS Consortium.

BACKGROUND The Invasive Respiratory Infection Surveillance (IRIS) Consortium was established to assess the impact of the COVID-19 pandemic on invasive diseases caused by Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, and Streptococcus agalactiae. We aimed to analyse the incidence and distribution of these diseases during the first 2 years of the COVID-19 pandemic compared to the 2 years preceding the pandemic. METHODS For this prospective analysis, laboratories in 30 countries and territories representing five continents submitted surveillance data from Jan 1, 2018, to Jan 2, 2022, to private projects within databases in PubMLST. The impact of COVID-19 containment measures on the overall number of cases was analysed, and changes in disease distributions by patient age and serotype or group were examined. Interrupted time-series analyses were done to quantify the impact of pandemic response measures and their relaxation on disease rates, and autoregressive integrated moving average models were used to estimate effect sizes and forecast counterfactual trends by hemisphere. FINDINGS Overall, 116 841 cases were analysed: 76 481 in 2018-19, before the pandemic, and 40 360 in 2020-21, during the pandemic. During the pandemic there was a significant reduction in the risk of disease caused by S pneumoniae (risk ratio 0·47; 95% CI 0·40-0·55), H influenzae (0·51; 0·40-0·66) and N meningitidis (0·26; 0·21-0·31), while no significant changes were observed for S agalactiae (1·02; 0·75-1·40), which is not transmitted via the respiratory route. No major changes in the distribution of cases were observed when stratified by patient age or serotype or group. An estimated 36 289 (95% prediction interval 17 145-55 434) cases of invasive bacterial disease were averted during the first 2 years of the pandemic among IRIS-participating countries and territories. INTERPRETATION COVID-19 containment measures were associated with a sustained decrease in the incidence of invasive disease caused by S pneumoniae, H influenzae, and N meningitidis during the first 2 years of the pandemic, but cases began to increase in some countries towards the end of 2021 as pandemic restrictions were lifted. These IRIS data provide a better understanding of microbial transmission, will inform vaccine development and implementation, and can contribute to health-care service planning and provision of policies. FUNDING Wellcome Trust, NIHR Oxford Biomedical Research Centre, Spanish Ministry of Science and Innovation, Korea Disease Control and Prevention Agency, Torsten Söderberg Foundation, Stockholm County Council, Swedish Research Council, German Federal Ministry of Health, Robert Koch Institute, Pfizer, Merck, and the Greek National Public Health Organization

The Neisseria meningitidis adhesion regulatory protein CrgA acts through oligomerization and interaction with RNA polymerase

International audienceCrgA is a LysR-type transcriptional regulator involved in the intimate adhesion of Neisseria meningitidis to target human epithelial cells. It is negatively autoregulated, and its expression is transiently induced upon contact with target cells. We analysed the functional organization of CrgA using in frame deleted proteins. Four truncated proteins were constructed and purified. They were deleted between residues 20 and 40, 121 and 154, 111 and 181 and 268 and 291. Meningococcal mutants harbouring the corresponding deleted crgA alleles were also constructed. All mutants showed a reduced ability to adhere to epithelial cells. beta-Galactosidase activity assays using a crgA-lacZ transcriptional fusion showed that all the mutations except the 268-291 deletion resulted in loss of induction upon contact with target cells. Gel mobility shift assays and cross-linking assays showed that the oligomerization of CrgA is required for DNA binding and that the N-terminal part of CrgA is directly involved in DNA binding through a helix-turn-helix motif. The C-terminal region is also involved in DNA binding, probably by permitting the oligomerization of CrgA. The C-terminal region also seemed to interact with RNA polymerase. Therefore, the binding of CrgA and its interaction with RNA polymerase may inhibit the clearance of meningococcal promoters that are repressed by CrgA during the intimate adhesion of N. meningitidis to target cells

Physiopathologie des infections invasives à méningocoque

International audienceNeisseria meningitidis, le méningocoque est une bactérie strictement humaine, commensale du tractus respiratoire. Dans des conditions mal élucidées, cette bactérie pourrait être responsable d'infections systémiques qui posent un sérieux problème de santé publique, à cause de leur potentiel épidémique et de la gravité des séquelles que peuvent générer ces infections. Les études épidémiologiques ont montré que les isolats invasifs diffèrent génotypiquement et phénotypiquement des isolats du portage asymptomatique. Dans ces conditions, les infections méningococciques constituent un processus multifactoriel qui implique à la fois des facteurs liés à l'hôte et d'autres liés à la bactérie. L'analyse du comportement des souches invasives et des souches de portage, ainsi que les bases moléculaires impliquées dans les étapes séquentielles de leurs interactions avec l'hôte, permettra de mieux comprendre cette infection

Vaccines targeting serogroup B meningococci.

International audienc

Changes in Invasive Neisseria meningitidis and Haemophilus influenzae Infections in France during the COVID-19 Pandemic

BackgroundSince the appearance of COVID-19 in January 2020, invasive bacterial infections have decreased significantly worldwide. However, alterations in age and sex distributions, clinical forms, phenotypes, and genotypes of isolates have not been analyzed. Our goal is to present and discuss these data considering the current COVID-19 pandemic situation. Methods: The data of the national reference center for meningococci and Haemophilus influenzae in France were mined to examine the above aspects of invasive bacterial infection before (2018–2019) and after (2020–2021) the COVID-19 pandemic. Detailed epidemiological, clinical, and microbiological data were collected, and whole genome sequencing was carried out on meningococcal isolates (n = 1466). Results: In addition to the overall decline in the number of cases, various changes in age, sex, and phenotypes of isolates were also noted. As for N. meningitidis, more cases were observed in adults, as well as more invasive pneumopathies. Furthermore, fewer hyperinvasive meningococcal genotypes have circulated since COVID-19 emerged. The situation has been different for H. influenzae, as the number of invasive cases among adults decreased due to a reduction in non-typeable isolates. In contrast, cases due to serotypeable isolates, particularly serotypes a and b, increased in children <5 years-old. Conclusions: It is possible that measures implemented to stop COVID-19 may have reduced the circulation of N. meningitidis and H. influenzae isolates, but to a variable extent. This may be due to differences in circulation between these two species according to age groups. Vaccination schedules against these two species may have also influenced the evolution of these invasive bacterial infections since the emergence of the COVID-19 pandemic

Immediate outcomes of bacterial meningitis in childhood may benefit from slow initial β-lactam infusion and oral paracetamol.

International audienceEvaluation of: Pelkonen T, Roine I, Cruzeiro ML, Pitkaranta A, Kataja M, Peltola H. Slow initial β-lactam infusion and oral paracetamol to treat childhood bacterial meningitis: a randomised, controlled trial. Lancet Infect. Dis. 11(8), 613-621 (2011). Acute bacterial meningitis is a medical emergency that requires prompt management. Despite effective antibiotic and adjunctive therapies, mortality is still unacceptably high in acute bacterial meningitis in children as this mortality did not substantially improve since the first use of antimicrobial therapies in the mid-20th century. β-lactams and particularly third-generation cephalosporins (ceftriaxone or cefotaxime) penetrate most body tissues and fluids, such as the cerebrospinal fluid, well. They are effective against the three most frequent bacterial causative agents of acute bacterial meningitis (Neisseria meningitidis, Streptococcus pneumoniae and Hemophilus influenzae). They are currently the consensual choices for the presumptive treatment of acute bacterial meningitis and usually used as a bolus every 4-6 h. Pelkonen et al. published a prospective, double-blind, single-center study with a two-by-two factorial design that aimed to explore the benefits in children of infused compared with bolus cefotaxime administration. Each group (bolus and infusion) was divided into two subgroups (with oral paracetamol or with placebo). No significant difference was observed for the final outcomes (mortality or severe neurological sequela and deafness) in the four subgroups. However, a post-hoc analysis of the results suggested that cefotaxime infusion plus paracetamol recipients had significant lower mortality during the first 72 h, irrespective of causative agents. However, the relevance of this study in sub-Saharan Africa is still difficult to evaluate as more than half of the initially assessed patients did not meet the inclusion criteria. The extension of the conclusions to developed countries may require further evaluations in terms of pharmacokinetic/pharmacodynamic properties as well as a thorough characterization of the causative agents under the view of the heterogeneous genetic structure of circulating bacterial strains in developed countries