Publications by authors named "Giuseppe Ercoli"

14 Publications

  • Page 1 of 1

Protective Effect of Nasal Colonisation with and Strains against Recolonisation and Invasive Infection.

Vaccines (Basel) 2021 Mar 15;9(3). Epub 2021 Mar 15.

Centre for Inflammation and Tissue Repair, UCL Respiratory, Division of Medicine, University College London, Rayne Institute, London WC1E 6JF, UK.

Rationale: Nasopharyngeal administration of live virulence-attenuated strains is a potential novel preventative strategy. One target for creating reduced virulence strains is the capsule, but loss of the capsule reduces the duration of colonisation in mice which could impair protective efficacy against subsequent infection.

Objectives: To assess protective efficacy of nasopharyngeal administration of unencapsulated strains in murine infection models.

Methods: Strains containing locus deletions combined with the virulence factors (reduces colonisation) or (no effect on colonisation) were constructed and their virulence phenotypes and ability to prevent recolonisation or invasive infection assessed using mouse infection models. Serological responses to colonisation were compared between strains using ELISAs, immunoblots and 254 protein antigen array.

Measurements And Main Results: The and strains were strongly attenuated in virulence in both invasive infection models and had a reduced ability to colonise the nasopharynx. ELISAs, immunoblots and protein arrays showed colonisation with either strain stimulated weaker serological responses than the wild type strain. Mice previously colonised with these strains were protected against septicaemic pneumonia but, unlike mice colonised with the wild type strain, not against recolonisation.

Conclusions: Colonisation with the and strains prevented subsequent septicaemia, but in contrast, to published data for encapsulated double mutant strains they did not prevent recolonisation with . These data suggest targeting the locus is a less effective option for creating live attenuated strains that prevent infections.
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http://dx.doi.org/10.3390/vaccines9030261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8000150PMC
March 2021

The Influence of B Cell Depletion Therapy on Naturally Acquired Immunity to .

Front Immunol 2020 28;11:611661. Epub 2021 Jan 28.

Centre for Inflammation and Tissue Repair, UCL Respiratory, Division of Medicine, University College Medical School, Rayne Institute, London, United Kingdom.

The anti-CD20 antibody Rituximab to deplete CD20+ B cells is an effective treatment for rheumatoid arthritis and B cell malignancies, but is associated with an increased incidence of respiratory infections. Using mouse models we have investigated the consequences of B cell depletion on natural and acquired humoral immunity to . B cell depletion of naïve C57Bl/6 mice reduced natural IgM recognition of , but did not increase susceptibility to pneumonia. ELISA and flow cytometry assays demonstrated significantly reduced IgG and IgM recognition of in sera from mice treated with B cell depletion prior to nasopharyngeal colonization compared to untreated mice. Colonization induced antibody responses to protein rather than capsular antigen, and when measured using a protein array B cell depletion prior to colonization reduced serum levels of IgG to several protein antigens. However, B cell depleted colonized mice were still partially protected against both lung infection and septicemia when challenged with after reconstitution of their B cells. These data indicate that although B cell depletion markedly impairs antibody recognition of in colonized mice, some protective immunity is maintained, perhaps mediated by cellular immunity.
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http://dx.doi.org/10.3389/fimmu.2020.611661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7876223PMC
June 2021

The B-cell inhibitory receptor CD22 is a major factor in host resistance to Streptococcus pneumoniae infection.

PLoS Pathog 2020 04 23;16(4):e1008464. Epub 2020 Apr 23.

Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.

Streptococcus pneumoniae is a major human pathogen, causing pneumonia and sepsis. Genetic components strongly influence host responses to pneumococcal infections, but the responsible loci are unknown. We have previously identified a locus on mouse chromosome 7 from a susceptible mouse strain, CBA/Ca, to be crucial for pneumococcal infection. Here we identify a responsible gene, Cd22, which carries a point mutation in the CBA/Ca strain, leading to loss of CD22 on B cells. CBA/Ca mice and gene-targeted CD22-deficient mice on a C57BL/6 background are both similarly susceptible to pneumococcal infection, as shown by bacterial replication in the lungs, high bacteremia and early death. After bacterial infections, CD22-deficient mice had strongly reduced B cell populations in the lung, including GM-CSF producing, IgM secreting innate response activator B cells, which are crucial for protection. This study provides striking evidence that CD22 is crucial for protection during invasive pneumococcal disease.
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http://dx.doi.org/10.1371/journal.ppat.1008464DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7179836PMC
April 2020

Deletion of the Zinc Transporter Lipoprotein AdcAII Causes Hyperencapsulation of Streptococcus pneumoniae Associated with Distinct Alleles of the Type I Restriction-Modification System.

mBio 2020 03 31;11(2). Epub 2020 Mar 31.

Centre for Inflammation and Tissue Repair, Department of Medicine, Royal Free and University College Medical School, Rayne Institute, London, United Kingdom.

The capsule is the dominant virulence factor, yet how variation in capsule thickness is regulated is poorly understood. Here, we describe an unexpected relationship between mutation of , which encodes a zinc uptake lipoprotein, and capsule thickness. Partial deletion of in three of five capsular serotypes frequently resulted in a mucoid phenotype that biochemical analysis and electron microscopy of the D39 mutants confirmed was caused by markedly increased capsule thickness. Compared to D39, the hyperencapsulated mutant strain was more resistant to complement-mediated neutrophil killing and was hypervirulent in mouse models of invasive infection. Transcriptome analysis of D39 and the mutant identified major differences in transcription of the Sp_0505-0508 locus, which encodes an SpnD39III (ST5556II) type I restriction-modification system and allelic variation of which correlates with capsule thickness. A PCR assay demonstrated close linkage of the SpnD39IIIC and F alleles with the hyperencapsulated strains. However, transformation of with fixed SpnD39III alleles associated with normal capsule thickness did not revert the hyperencapsulated phenotype. Half of hyperencapsulated strains contained the same single nucleotide polymorphism in the capsule locus gene , which is required for the initiation of capsule synthesis. These results provide further evidence for the importance of the SpnD39III (ST5556II) type I restriction-modification system for modulating capsule thickness and identified an unexpected linkage between capsule thickness and mutation of Further investigation will be needed to characterize how mutation of affects SpnD39III (ST5556II) allele dominance and results in the hyperencapsulated phenotype. The capsule affects multiple interactions with the host including contributing to colonization and immune evasion. During infection, the capsule thickness varies, but the mechanisms regulating this are poorly understood. We have identified an unsuspected relationship between mutation of , a gene that encodes a zinc uptake lipoprotein, and capsule thickness. Mutation of resulted in a striking hyperencapsulated phenotype, increased resistance to complement-mediated neutrophil killing, and increased virulence in mouse models of infection. Transcriptome and PCR analysis linked the hyperencapsulated phenotype of the strain to specific alleles of the SpnD39III (ST5556II) type I restriction-modification system, a system which has previously been shown to affect capsule thickness. Our data provide further evidence for the importance of the SpnD39III (ST5556II) type I restriction-modification system for modulating capsule thickness and identify an unexpected link between capsule thickness and , further investigation of which could further characterize mechanisms of capsule regulation.
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http://dx.doi.org/10.1128/mBio.00445-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7157770PMC
March 2020

Relative Contributions of Extracellular and Internalized Bacteria to Early Macrophage Proinflammatory Responses to Streptococcus pneumoniae.

mBio 2019 09 24;10(5). Epub 2019 Sep 24.

Centre for Inflammation and Tissue Repair, UCL Respiratory, Division of Medicine, University College Medical School, Rayne Institute, London, United Kingdom

Both intracellular immune sensing and extracellular innate immune sensing have been implicated in initiating macrophage proinflammatory cytokine responses to The capsule, a major virulence determinant, prevents phagocytosis, and we hypothesized that this would reduce activation of host innate inflammatory responses by preventing activation of intracellular proinflammatory signaling pathways. We investigated this hypothesis in human monocyte-derived macrophages stimulated with encapsulated or isogenic unencapsulated mutant Unexpectedly, despite strongly inhibiting bacterial internalization, the capsule resulted in enhanced inflammatory cytokine production by macrophages infected with Experiments using purified capsule material and a mutant expressing an serotype 4 capsule indicated these differences required whole bacteria and were not due to proinflammatory effects of the capsule itself. Transcriptional profiling demonstrated relatively few differences in macrophage gene expression profiles between infections with encapsulated and those with unencapsulated , largely limited to reduced expression of proinflammatory genes in response to unencapsulated bacteria, predicted to be due to reduced activation of the NF-κB family of transcription factors. Blocking internalization using cytochalasin D had minimal effects on the inflammatory response to Experiments using murine macrophages indicated that the affected genes were dependent on Toll-like receptor 2 (TLR2) activation, although not through direct stimulation of TLR2 by capsule polysaccharide. Our data demonstrate that the early macrophage proinflammatory response to is mainly dependent on extracellular bacteria and reveal an unexpected proinflammatory effect of encapsulated that could contribute to disease pathogenesis. Multiple extra- and intracellular innate immune receptors have been identified that recognize , but the relative contributions of intra- versus extracellular bacteria to the inflammatory response were unknown. We have shown that intracellular contributes surprisingly little to the inflammatory responses, with production of important proinflammatory cytokines largely dependent on extracellular bacteria. Furthermore, although we expected the polysaccharide capsule to block activation of the host immune system by reducing bacterial internalization and therefore activation of intracellular innate immune receptors, there was an increased inflammatory response to encapsulated compared to unencapsulated bacteria, which is likely to contribute to disease pathogenesis.
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http://dx.doi.org/10.1128/mBio.02144-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759765PMC
September 2019

Mechanisms of Naturally Acquired Immunity to .

Front Immunol 2019 1;10:358. Epub 2019 Mar 1.

Centre for Inflammation and Tissue Repair, UCL Respiratory, London, United Kingdom.

In this review we give an update on the mechanisms of naturally acquired immunity against , one of the major human bacterial pathogens that is a common cause of pneumonia, septicaemia, and meningitis. A clear understanding of the natural mechanisms of immunity to is necessary to help define why the very young and elderly are at high risk of disease, and for devising new prevention strategies. Recent data has shown that nasopharynx colonization by induces antibody responses to protein and capsular antigens in both mice and humans, and also induces Th17 CD4+ cellular immune responses in mice and increases pre-existing responses in humans. These responses are protective, demonstrating that colonization is an immunizing event. We discuss the data from animal models and humans on the relative importance of naturally acquired antibody and Th17 cells on immunity to at three different anatomical sites of infection, the nasopharynx (the site of natural asymptomatic carriage), the lung (site of pneumonia), and the blood (site of sepsis). Mouse data suggest that CD4+ Th17 cells prevent both primary and secondary nasopharyngeal carriage with no role for antibody induced by previous colonization. In contrast, antibody is necessary for prevention of sepsis but CD4+ cellular responses are not. Protection against pneumonia requires a combination of both antibody and Th17 cells, in both cases targeting protein rather than capsular antigen. Proof of which immune component prevents human infection is less easily available, but two recent papers demonstrate that human IgG targeting protein antigens is highly protective against septicaemia. The role of CD4+ responses to prior nasopharyngeal colonization for protective immunity in humans is unclear. The evidence that there is significant naturally-acquired immunity to independent of anti-capsular polysaccharide has clinical implications for the detection of subjects at risk of infections, and the data showing the importance of protein antigens as targets for antibody and Th17 mediated immunity should aid the development of new vaccine strategies.
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http://dx.doi.org/10.3389/fimmu.2019.00358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6405633PMC
September 2020

A Novel, Multiple-Antigen Pneumococcal Vaccine Protects against Lethal Challenge.

Infect Immun 2019 03 21;87(3). Epub 2019 Feb 21.

Centre for Inflammation and Tissue Repair, UCL Respiratory, Division of Medicine, University College Medical School Rayne Institute, London, United Kingdom

Current vaccination against uses vaccines based on capsular polysaccharides from selected serotypes and has led to nonvaccine serotype replacement disease. We have investigated an alternative serotype-independent approach, using multiple-antigen vaccines (MAV) prepared from TIGR4 lysates enriched for surface proteins by a chromatography step after culture under conditions that induce expression of heat shock proteins (Hsp; thought to be immune adjuvants). Proteomics and immunoblot analyses demonstrated that, compared to standard bacterial lysates, MAV was enriched with Hsps and contained several recognized protective protein antigens, including pneumococcal surface protein A (PspA) and pneumolysin (Ply). Vaccination of rodents with MAV induced robust antibody responses to multiple serotypes, including nonpneumococcal conjugate vaccine serotypes. Homologous and heterologous strains of were opsonized after incubation in sera from vaccinated rodents. In mouse models, active vaccination with MAV significantly protected against pneumonia, while passive transfer of rabbit serum from MAV-vaccinated rabbits significantly protected against sepsis caused by both homologous and heterologous strains. Direct comparison of MAV preparations made with or without the heat shock step showed no clear differences in protein antigen content and antigenicity, suggesting that the chromatography step rather than Hsp induction improved MAV antigenicity. Overall, these data suggest that the MAV approach may provide serotype-independent protection against .
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http://dx.doi.org/10.1128/IAI.00846-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6386546PMC
March 2019

A recombinant conjugated pneumococcal vaccine that protects against murine infections with a similar efficacy to Prevnar-13.

NPJ Vaccines 2018 31;3:53. Epub 2018 Oct 31.

1Department of Respiratory Medicine, Centre for Inflammation and Tissue Repair, University College London, London, UK.

The pneumococcal conjugate vaccine (PCV) strongly protects against vaccine serotypes, but the rapid expansion of non-vaccine serotype disease and the vaccine's high expense has reduced its overall impact. We have developed Protein Glycan Coupling Technology (PGCT) as a flexible methodology for making low-cost polysaccharide/protein glycoconjugates recombinantly in . We have used PGCT to make a recombinant PCV containing serotype 4 capsular polysaccharide linked to the proteins NanA, PiuA, and Sp0148. The introduction of the UDP-glucose 4-epimerase gene GalE () into improved the yield of the resulting glycoprotein. PGCT glycoconjugate vaccination generated strong antibody responses in mice to both the capsule and the carrier protein antigens, with the PiuA/capsule glycoconjugate inducing similar anti-capsular antibody responses as the commercial PCV Prevnar-13. Antibody responses to PGCT glycoconjugates opsonised and expressing the serotype 4 capsule and promoted neutrophil phagocytosis of to a similar level as antisera generated by vaccination with Prevnar-13. Vaccination with the PGCT glycoconjugates protected mice against meningitis and septicaemia with the same efficacy as vaccination with Prevnar-13. In addition, vaccination with the protein antigen components from PGCT glycoconjugates alone provided partial protection against septicaemia and colonisation. These data demonstrate that a vaccine made by PGCT is as effective as Prevnar-13, identifies PiuA as a carrier protein for glycoconjugate vaccines, and demonstrates that linking capsular antigen to protein antigens has additional protective benefits that could provide a degree of serotype-independent immunity.
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http://dx.doi.org/10.1038/s41541-018-0090-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208403PMC
October 2018

An ex vivo porcine spleen perfusion as a model of bacterial sepsis.

ALTEX 2019 3;36(1):29-38. Epub 2018 Aug 3.

Department of Genetics and Genome Biology, University of Leicester, Leicester, UK.

An ex vivo, porcine spleen perfusion model was established to study the early events occurring in the spleen prior to the onset of bacterial sepsis, using organs retrieved from animals slaughtered for food production. Porcine spleens were harvested from adult pigs and connected to a normothermic extracorporeal perfusion circuit. A constant perfusion of heparinized blood was performed for 6 hours. After injection of Streptococcus pneumoniae to the circuit serial samples of both blood and spleen biopsies were collected and analysed. Functionality of the perfused organs was assessed by monitoring the blood-gas parameters, flow rate and filtering capability of the organ. Interestingly, we observed full clearance of bacteria from the blood and an increase in bacterial counts in the spleen. Classical histology and immunohistochemistry on biopsies also confirmed no major damages in the organ architecture and changes in the immune cell distribution, other than the presence of clusters of pneumococci. A time-course study confirmed that each focus of infection derived from the replication of single pneumococcal cells within splenic macrophages. The model proposed - in line with the 3Rs principles - has utility in the replacement of experimental animals in infection research. Murine models are prevalently used to study pneumococcal infections, but are often not predictive for humans due to substantial differences in the immune systems of the two species. This model is designed to overcome these limitations, since porcine immunology and splenic architecture in particular, closely resemble those of humans.
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http://dx.doi.org/10.14573/altex.1805131DOI Listing
April 2019

Intracellular replication of Streptococcus pneumoniae inside splenic macrophages serves as a reservoir for septicaemia.

Nat Microbiol 2018 05 16;3(5):600-610. Epub 2018 Apr 16.

Department of Genetics and Genome Biology, University of Leicester, Leicester, UK.

Bacterial septicaemia is a major cause of mortality, but its pathogenesis remains poorly understood. In experimental pneumococcal murine intravenous infection, an initial reduction of bacteria in the blood is followed hours later by a fatal septicaemia. These events represent a population bottleneck driven by efficient clearance of pneumococci by splenic macrophages and neutrophils, but as we show in this study, accompanied by occasional intracellular replication of bacteria that are taken up by a subset of CD169 splenic macrophages. In this model, proliferation of these sequestered bacteria provides a reservoir for dissemination of pneumococci into the bloodstream, as demonstrated by its prevention using an anti-CD169 monoclonal antibody treatment. Intracellular replication of pneumococci within CD169 splenic macrophages was also observed in an ex vivo porcine spleen, where the microanatomy is comparable with humans. We also showed that macrolides, which effectively penetrate macrophages, prevented septicaemia, whereas beta-lactams, with inefficient intracellular penetration, failed to prevent dissemination to the blood. Our findings define a shift in our understanding of the pneumococcus from an exclusively extracellular pathogen to one with an intracellular phase. These findings open the door to the development of treatments that target this early, previously unrecognized intracellular phase of bacterial sepsis.
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http://dx.doi.org/10.1038/s41564-018-0147-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207342PMC
May 2018

Effectiveness of a Very Early Stepping Verticalization Protocol in Severe Acquired Brain Injured Patients: A Randomized Pilot Study in ICU.

PLoS One 2016 22;11(7):e0158030. Epub 2016 Jul 22.

Research Unit for Neurorehabilitation South Tyrol, Landeskrankenhaus Hochzirl-Natters, Zirl, Austria.

Background And Objective: Verticalization was reported to improve the level of arousal and awareness in patients with severe acquired brain injury (ABI) and to be safe in ICU. We evaluated the effectiveness of a very early stepping verticalization protocol on their functional and neurological outcome.

Methods: Consecutive patients with Vegetative State or Minimally Conscious State were enrolled in ICU on the third day after an ABI. They were randomized to undergo conventional physiotherapy alone or associated to fifteen 30-minute sessions of verticalization, using a tilt table with robotic stepping device. Once stabilized, patients were transferred to our Neurorehabilitation unit for an individualized treatment. Outcome measures (Glasgow Coma Scale, Coma Recovery Scale revised -CRSr-, Disability Rating Scale-DRS- and Levels of Cognitive Functioning) were assessed on the third day from the injury (T0), at ICU discharge (T1) and at Rehab discharge (T2). Between- and within-group comparisons were performed by the Mann-Whitney U test and Wilcoxon signed-rank test, respectively.

Results: Of the 40 patients enrolled, 31 completed the study without adverse events (15 in the verticalization group and 16 in the conventional physiotherapy). Early verticalization started 12.4±7.3 (mean±SD) days after ABI. The length of stay in ICU was longer for the verticalization group (38.8 ± 15.7 vs 25.1 ± 11.2 days, p = 0.01), while the total length of stay (ICU+Neurorehabilitation) was not significantly different (153.2 ± 59.6 vs 134.0 ± 61.0 days, p = 0.41). All outcome measures significantly improved in both groups after the overall period (T2 vs T0, p<0.001 all), as well as after ICU stay (T1 vs T0, p<0.004 all) and after Neurorehabilitation (T2 vs T1, p<0.004 all). The improvement was significantly better in the experimental group for CRSr (T2-T0 p = 0.033, T1-T0 p = 0.006) and (borderline) for DRS (T2-T0 p = 0.040, T1-T0 p = 0.058).

Conclusions: A stepping verticalization protocol, started since the acute stages, improves the short-term and long-term functional and neurological outcome of ABI patients.

Trial Registration: clinicaltrials.gov NCT02828371.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0158030PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4957764PMC
July 2017

Development of a serological assay to predict antibody bactericidal activity against non-typeable Haemophilus influenzae.

BMC Microbiol 2015 Apr 18;15:87. Epub 2015 Apr 18.

Novartis Vaccines & Diagnostics s.r.l. (a GSK company), Via Fiorentina 1, 53100, Siena, Italy.

Background: Non-typeable Haemophilus influenzae (NTHi) is a Gram negative microorganism residing in the human nasopharyngeal mucosa and occasionally causing infections of both middle ear and lower respiratory airways. A broadly protective vaccine against NTHi has been a long-unmet medical need, as the high genetic variability of this bacterium has posed great challenges.

Results: In this study, we developed a robust serum bactericidal assay (SBA) to optimize the selection of protective antigens against NTHi. SBA takes advantage of the complement-mediated lysis of bacterial cells and is a key in vitro method for measuring the functional activity of antibodies. As a proof of concept, we assessed the bactericidal activity of antibodies directed against antigens known to elicit a protective response, including protein D used as carrier protein in the Synflorix pneumococcal polysaccharide conjugate vaccine. Prior to SBA screening, the accessibility of antigens to antibodies and the capacity of the latter to induce C3 complement deposition was verified by flow cytometry. Using baby rabbit serum as a source of complement, the proposed assay not only confirmed the bactericidal activity of the antibodies against the selected vaccine candidates, but also showed a significant reproducibility.

Conclusions: Considering the rapidity and cost-effectiveness of this novel SBA protocol, we conclude that it is likely to become an important tool to prove the capability of antibodies directed against recombinant antigens to induce NTHi in vitro killing and to both select new protective vaccine candidates, and predict vaccine efficacy.
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http://dx.doi.org/10.1186/s12866-015-0420-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4409741PMC
April 2015

LytM proteins play a crucial role in cell separation, outer membrane composition, and pathogenesis in nontypeable Haemophilus influenzae.

mBio 2015 Feb 24;6(2):e02575. Epub 2015 Feb 24.

Novartis Vaccines, Siena, Italy

Unlabelled: LytM proteins belong to a family of bacterial metalloproteases. In Gram-negative bacteria, LytM factors are mainly reported to have a direct effect on cell division by influencing cleavage and remodeling of peptidoglycan. In this study, mining nontypeable Haemophilus influenzae (NTHI) genomes, three highly conserved open reading frames (ORFs) containing a LytM domain were identified, and the proteins encoded by the ORFs were named YebA, EnvC, and NlpD on the basis of their homology with the Escherichia coli proteins. Immunoblotting and confocal analysis showed that while NTHI NlpD is exposed on the bacterial surface, YebA and EnvC reside in the periplasm. NTHI ΔyebA and ΔnlpD deletion mutants revealed an aberrant division phenotype characterized by an altered cell architecture and extensive membrane blebbing. The morphology of the ΔenvC deletion mutant was identical to that of the wild-type strain, but it showed a drastic reduction of periplasmic proteins, including the chaperones HtrA, SurA, and Skp, and an accumulation of β-barrel-containing outer membrane proteins comprising the autotransporters Hap, IgA serine protease, and HMW2A, as observed by proteomic analysis. These data suggest that EnvC may influence the bacterial surface protein repertoire by facilitating the passage of the periplasmic chaperones through the peptidoglycan layer to the close vicinity of the inner face of the outer membrane. This hypothesis was further corroborated by the fact that an NTHI envC defective strain had an impaired capacity to adhere to epithelial cells and to form biofilm. Notably, this strain also showed a reduced serum resistance. These results suggest that LytM factors are not only important components of cell division but they may also influence NTHI physiology and pathogenesis by affecting membrane composition.

Importance: Nontypeable Haemophilus influenzae (NTHI) is an opportunistic pathogen that colonizes the human nasopharynx and can cause serious infections in children (acute otitis media) and adults (chronic obstructive pulmonary disease). Several virulence factors are well studied, but the complete scenario of NTHI pathogenesis is still unclear. We identified and characterized three NTHI LytM factors homologous to the Escherichia coli LytM proteins. Although LytM factors are reported to play a crucial role in the cell division process, in NTHI they are also involved in other bacterial functions. In particular, YebA and NlpD are fundamental for membrane stability: indeed, their absence causes an increased release of outer membrane vesicles (OMVs). On the other hand, our data suggest that EnvC could directly or indirectly affect peptidoglycan permeability and consequently, bacterial periplasmic and outer membrane protein distribution. Interestingly, by modulating the surface composition of virulence determinants, EnvC also has an impact on NTHI pathogenesis.
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http://dx.doi.org/10.1128/mBio.02575-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4358004PMC
February 2015
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