Publications by authors named "Immaculada Margarit"

68 Publications

Group B Streptococcus chimeric capsular polysaccharides as novel multivalent vaccine candidates.

Glycoconj J 2021 May 6. Epub 2021 May 6.

GSK, Siena, Italy.

The capsular polysaccharide of the human pathogen Group B Streptococcus is a key virulence factor and vaccine candidate that induces protective antibodies when conjugated to carrier proteins. It consists of long polymeric chains of oligosaccharide repeating units, and each of the ten capsular serotypes described so far presents a unique chemical structure with distinct antigenic properties; therefore, broad protection against this pathogen could be achieved by a combination of ten glycoconjugates. Capsular polysaccharide biosynthesis and assembly follow a polymerase-dependent pathway that is widespread in encapsulated bacteria and is encoded by a polycistronic operon. Here we exploited the sequence similarity between the capsule operons of types V and IX to generate hybrid polysaccharides incorporating epitopes of both serotypes in a single molecule, by co-expressing their specific CpsM, O, I glycosyltransferases in a single isolate. Physicochemical and immunochemical methods confirmed that an engineered strain produced a high molecular weight chimeric polysaccharide, combining antigenic specificities of both type V and IX. By optimizing the copy number of key glycosyltransferase genes, we were able to modulate the ratio between type-specific epitopes. Finally, vaccination with chimeric glycoconjugates significantly decreased the incidence of disease in pups born from immunized mice challenged with either serotype. This study provides proof of concept for a new generation of glycoconjugate vaccines that combine the antigenic specificity of different polysaccharide variants in a single molecule, eliciting a protective immune response against multiple serotype variants.
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http://dx.doi.org/10.1007/s10719-021-10000-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8100357PMC
May 2021

Safety and immunogenicity of an investigational maternal trivalent group B streptococcus vaccine in pregnant women and their infants: Results from a randomized placebo-controlled phase II trial.

Vaccine 2020 10 1;38(44):6930-6940. Epub 2020 Sep 1.

GSK, Rockville, MD, USA. Electronic address:

Background: This study evaluated the safety and immunogenicity of an investigational trivalent group B streptococcus (GBS) vaccine in US pregnant women, transplacental serotype-specific antibody transfer and persistence in infants, and serotype-specific antibodies in breast milk.

Methods: This randomized, observer-blind, placebo-controlled trial administered one dose of trivalent GBS vaccine (n = 49) or placebo (n = 26) to healthy pregnant 18-40-year-old women at 24-34 weeks' gestation. Women were enrolled from March 2014 to August 2015. Safety follow-up continued through postpartum day 180. Primary immunogenicity objectives were to evaluate serotype Ia/Ib/III-specific immunoglobulin G (IgG) levels in sera from women on day 1 (pre-vaccination), day 31, delivery and postpartum days 42 and 90, and from infants at birth (cord blood), days 42 and 90. Antibody transfer ratios (cord blood/maternal sera at delivery) and serotype-specific secretory immunoglobulin A (sIgA) and IgG in breast milk after delivery and on postpartum days 42 and 90 were evaluated. The planned sample size was not based on statistical assumptions for this descriptive study.

Results: Baseline characteristics were similar between groups. Serious adverse events were reported for 16% of GBS-vaccinated women and 15% of their infants, and 15% of placebo recipients and 12% of their infants; none were fatal or deemed vaccine-related. Serotype-specific IgG geometric mean concentrations (GMCs) were 13-23-fold higher in vaccine vs placebo recipients on day 31 and persisted until postpartum day 90. Median antibody concentrations were substantially higher in women with detectable pre-vaccination antibody concentrations. Antibody transfer ratios in the vaccine group were 0.62-0.82. Infant IgG GMCs and breast milk sIgA GMCs were higher in the vaccine vs the placebo group at all timepoints.

Conclusions: Maternal immunization with the trivalent GBS vaccine in US women had a favorable safety profile, elicited antibodies that were transplacentally transferred and persisted in infants for a minimum of 3 months.

Clinical Trial Registration: Clinicaltrials.gov, NCT02046148.
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http://dx.doi.org/10.1016/j.vaccine.2020.08.056DOI Listing
October 2020

Publisher Correction: Mice repeatedly exposed to Group-A β-Haemolytic Streptococcus show perseverative behaviors, impaired sensorimotor gating, and immune activation in rostral diencephalon.

Sci Rep 2020 Aug 3;10(1):13014. Epub 2020 Aug 3.

Sect. Behavioural Neuroscience, Dept. Cell Biology & Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena, 299, I-00161, Roma, Italy.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41598-020-69954-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7398902PMC
August 2020

Structure-Guided Design of a Group B Streptococcus Type III Synthetic Glycan-Conjugate Vaccine.

Chemistry 2020 Jun 11;26(31):6944. Epub 2020 May 11.

Research Center, GlaxoSmithKline Plc, Via Fiorentina 1, 53100, Siena, Italy.

Invited for the cover of this issue is the group of Roberto Adamo at GlaxoSmithKline Research Center, Siena, and colleagues at The University of the Basque Country and Basque Research Technology Alliance. The image depicts a tactical plan with the different elements of the research as part of the team. Read the full text of the article at 10.1002/chem.202000284.
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http://dx.doi.org/10.1002/chem.202002016DOI Listing
June 2020

Structure, dynamics and immunogenicity of a catalytically inactive CC chemokine-degrading protease SpyCEP from .

Comput Struct Biotechnol J 2020 13;18:650-660. Epub 2020 Mar 13.

Department of Life Sciences, Imperial College London, South Kensington Campus, SW7 2AZ, UK.

Over 18 million disease cases and half a million deaths worldwide are estimated to be caused annually by Group A Streptococcus. A vaccine to prevent GAS disease is urgently needed. SpyCEP (Streptococcus Cell-Envelope Proteinase) is a surface-exposed serine protease that inactivates chemokines, impairing neutrophil recruitment and bacterial clearance, and has shown promising immunogenicity in preclinical models. Although SpyCEP structure has been partially characterized, a more complete and higher resolution understanding of its antigenic features would be desirable prior to large scale manufacturing. To address these gaps and facilitate development of this globally important vaccine, we performed immunogenicity studies with a safety-engineered SpyCEP mutant, and comprehensively characterized its structure by combining X-ray crystallography, NMR spectroscopy and molecular dynamics simulations. We found that the catalytically-inactive SpyCEP antigen conferred protection similar to wild-type SpyCEP in a mouse infection model. Further, a new higher-resolution crystal structure of the inactive SpyCEP mutant provided new insights into this large chemokine protease comprising nine domains derived from two non-covalently linked fragments. NMR spectroscopy and molecular simulation analyses revealed conformational flexibility that is likely important for optimal substrate recognition and overall function. These combined immunogenicity and structural data demonstrate that the full-length SpyCEP inactive mutant is a strong candidate human vaccine antigen. These findings show how a multi-disciplinary study was used to overcome obstacles in the development of a GAS vaccine, an approach applicable to other future vaccine programs. Moreover, the information provided may also facilitate the structure-based discovery of small-molecule therapeutics targeting SpyCEP protease inhibition.
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http://dx.doi.org/10.1016/j.csbj.2020.03.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7113628PMC
March 2020

Structure-Guided Design of a Group B Streptococcus Type III Synthetic Glycan-Conjugate Vaccine.

Chemistry 2020 Jun 1;26(31):7018-7025. Epub 2020 Apr 1.

Research Center, GlaxoSmithKline Plc, Via Fiorentina 1, 53100, Siena, Italy.

Identification of glycan functional epitopes is of paramount importance for rational design of glycoconjugate vaccines. We recently mapped the structural epitope of the capsular polysaccharide from type III Group B Streptococcus (GBSIII), a major cause of invasive disease in newborns, by using a dimer fragment (composed of two pentasaccharide repeating units) obtained by depolymerization complexed with a protective mAb. Although reported data had suggested a highly complex epitope contained in a helical structure composed of more than four repeating units, we showed that such dimer conjugated to a carrier protein with a proper glycosylation degree elicited functional antibodies comparably to the full-length conjugated polysaccharide. Here, starting from the X-ray crystallographic structure of the polysaccharide fragment-mAb complex, we synthesized a hexasaccharide comprising exclusively the relevant positions involved in binding. Combining competitive surface plasmon resonance and saturation transfer difference NMR spectroscopy as well as in-silico modeling, we demonstrated that this synthetic glycan was recognized by the mAb similarly to the dimer. The hexasaccharide conjugated to CRM , a mutant of diphtheria toxin, elicited a robust functional immune response that was not inferior to the polysaccharide conjugate, indicating that it may suffice as a vaccine antigen. This is the first evidence of an X-ray crystallography-guided design of a synthetic carbohydrate-based conjugate vaccine.
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http://dx.doi.org/10.1002/chem.202000284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317837PMC
June 2020

Evaluation of Immune Responses to Group B Streptococcus Type III Oligosaccharides Containing a Minimal Protective Epitope.

J Infect Dis 2020 03;221(6):943-947

GSK Vaccines, Siena, Italy.

Recent structural studies demonstrated that the epitope recognized by a monoclonal antibody representative of the protective response against the type III group B Streptococcus polysaccharide was comprised within 2 of the repeating units that constitute the full-length native structure. In the current study, we took advantage of this discovery to design a novel vaccine based on multivalent presentation of the identified minimal epitope on a carrier protein. We show that highly glycosylated short oligosaccharide conjugates elicit functional immune responses comparable to those of the full-length native polysaccharide. The obtained results pave the way to the design of well-defined glycoconjugate vaccines based on short synthetic oligosaccharides.
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http://dx.doi.org/10.1093/infdis/jiz551DOI Listing
March 2020

Safety and Immunogenicity of a Second Dose of an Investigational Maternal Trivalent Group B Streptococcus Vaccine in Nonpregnant Women 4-6 Years After a First Dose: Results From a Phase 2 Trial.

Clin Infect Dis 2020 06;70(12):2570-2579

GlaxoSmithKline (GSK), Rockville, Maryland.

Background: Maternal immunization against group B streptococcus (GBS) could protect infants from invasive GBS disease. Additional doses in subsequent pregnancies may be needed. We evaluated the safety and immunogenicity of a second dose of an investigational trivalent CRM197-glycoconjugate GBS vaccine (targeting serotypes Ia/Ib/III), administered to nonpregnant women 4-6 years postdose 1.

Methods: Healthy women either previously vaccinated with 1 dose of trivalent GBS vaccine 4-6 years before enrollment (n = 53) or never GBS vaccinated (n = 27) received a single trivalent GBS vaccine injection. Adverse events (AEs) were recorded. Serotype-specific (Ia/Ib/III) anti-GBS antibodies were measured by multiplex immunoassay prevaccination and 30/60 days postvaccination.

Results: AEs were reported with similar rates after a first or second dose; none were serious. Of previously GBS-vaccinated women, 92%-98% had anti-GBS concentrations that exceeded an arbitrary threshold (8 µg/mL) for each serotype 60 days postdose 2 vs 36%-56% postdose 1 in previously non-GBS-vaccinated women. Of previously GBS-vaccinated women with undetectable baseline (predose 1) anti-GBS levels, 90%-98% reached this threshold postdose 2. For each serotype, anti-GBS geometric mean concentrations (GMCs) 30/60 days postdose 2 in previously GBS-vaccinated women were ≥200-fold higher than baseline GMCs. Among women with undetectable baseline anti-GBS levels, postdose 2 GMCs in previously GBS-vaccinated women exceeded postdose 1 GMCs in previously non-GBS-vaccinated women (≥7-fold).

Conclusions: A second trivalent GBS vaccine dose administered 4-6 years postdose 1 was immunogenic with a favorable safety profile. Women with undetectable preexisting anti-GBS concentrations may benefit from a sufficiently spaced second vaccine dose.

Clinical Trials Registration: NCT02690181.
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http://dx.doi.org/10.1093/cid/ciz737DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7286364PMC
June 2020

Novel Multiplex Immunoassays for Quantification of IgG against Group B Capsular Polysaccharides in Human Sera.

mSphere 2019 08 7;4(4). Epub 2019 Aug 7.

GSK, Siena, Italy

Group B (GBS) infections constitute a major cause of invasive disease during the first three months of life and an unmet medical need that could be addressed by maternal vaccination. The GBS capsular polysaccharides (CPSs) have shown promise as vaccine targets in clinical studies. A highly specific serological assay to quantify maternal and neonatal anti-CPS antibody levels will be instrumental for GBS vaccine licensure. Here, we describe the development and comparison of two novel multiplex immunoassays (MIAs) based on the Luminex technology for the quantification of IgG antibodies recognizing the five most frequent GBS capsular variants (Ia, Ib, II, III, and V) out of the ten types identified. The first assay is based on the use of biotinylated CPSs coupled to streptavidin-derivatized magnetic microspheres (Biotin-CPS MIA), while the second is a sandwich assay with plain CPSs coupled to magnetic microspheres coated with polysaccharide-specific mouse monoclonal antibodies (Sandwich MIA). Both assays showed good specificity, linearity, and precision, although the Biotin-CPS MIA presented higher sensitivity and lower complexity than the Sandwich MIA. A panel of human sera representing a wide range of anti-CPS IgG concentrations was tested in parallel by the two assays, which resulted in comparable titers. Our data support the preservation of antigenic epitopes in the biotinylated polysaccharides and the suitability of the Biotin-CPS MIA for the precise determination of GBS anti-CPS IgG concentrations in human sera. Group B streptococcal infections can cause death in neonates up to 3 months of age. Intrapartum antibiotic prophylaxis in GBS-colonized mothers has limited early infections but has no impact after the first week of life. The development of a maternal vaccine to address this unmet medical need has been identified as a priority by the World Health Organization, and the GBS CPSs are considered the best antigen targets. However, to date there are no accepted standardized assays to measure immune responses to the investigational vaccines and for establishment of serocorrelates of protection. Here, we describe the performance of two microsphere-based pentaplex immunoassays for the determination of antibodies recognizing the five most frequent GBS serotypes. Our data confirm that an assay based on biotinylated polysaccharides coupled to streptavidin microspheres would be suitable for the intended purpose.
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http://dx.doi.org/10.1128/mSphere.00273-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6686225PMC
August 2019

The Streptococcus agalactiae complement interfering protein combines multiple complement-inhibitory mechanisms by interacting with both C4 and C3 ligands.

FASEB J 2019 03 19;33(3):4448-4457. Epub 2018 Dec 19.

GlaxoSmithKline (GSK), Siena, Italy; and.

Group B Streptococcus (GBS) colonizes the human lower intestinal and genital tracts and constitutes a major threat to neonates from pregnant carrier mothers and to adults with underlying morbidity. The pathogen expresses cell-surface virulence factors that enable cell adhesion and penetration and that counteract innate and adaptive immune responses. Among these, the complement interfering protein (CIP) was recently described for its capacity to interact with the human C4b ligand and to interfere with the classical- and lectin-complement pathways. In the present study, we provide evidence that CIP can also interact with C3, C3b, and C3d. Immunoassay-based competition experiments showed that binding of CIP to C3d interferes with the interaction between C3d and the complement receptor 2/cluster of differentiation 21 (CR2/CD21) receptor on B cells. By B-cell intracellular signaling assays, CIP was confirmed to down-regulate CR2/CD21-dependent B-cell activation. The CIP domain involved in C3d binding was mapped via hydrogen deuterium exchange-mass spectrometry. The data obtained reveal a new role for this GBS polypeptide at the interface between the innate and adaptive immune responses, adding a new member to the growing list of virulence factors secreted by gram-positive pathogens that incorporate multiple immunomodulatory functions.-Giussani, S., Pietrocola, G., Donnarumma, D., Norais, N., Speziale, P., Fabbrini, M., Margarit, I. The Streptococcus agalactiae complement interfering protein combines multiple complement-inhibitory mechanisms by interacting with both C4 and C3 ligands.
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http://dx.doi.org/10.1096/fj.201801991RDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6404586PMC
March 2019

European Multicentre Tics in Children Studies (EMTICS): protocol for two cohort studies to assess risk factors for tic onset and exacerbation in children and adolescents.

Eur Child Adolesc Psychiatry 2019 Jan 7;28(1):91-109. Epub 2018 Jul 7.

Clinic of Child and Adolescent Psychiatry and Psychotherapy, University of Zurich, Zurich, Switzerland.

Genetic predisposition, autoimmunity and environmental factors [e.g. pre- and perinatal difficulties, Group A Streptococcal (GAS) and other infections, stress-inducing events] might interact to create a neurobiological vulnerability to the development of tics and associated behaviours. However, the existing evidence for this relies primarily on small prospective or larger retrospective population-based studies, and is therefore still inconclusive. This article describes the design and methodology of the EMTICS study, a longitudinal observational European multicentre study involving 16 clinical centres, with the following objectives: (1) to investigate the association of environmental factors (GAS exposure and psychosocial stress, primarily) with the onset and course of tics and/or obsessive-compulsive symptoms through the prospective observation of at-risk individuals (ONSET cohort: 260 children aged 3-10 years who are tic-free at study entry and have a first-degree relative with a chronic tic disorder) and affected individuals (COURSE cohort: 715 youth aged 3-16 years with a tic disorder); (2) to characterise the immune response to microbial antigens and the host's immune response regulation in association with onset and exacerbations of tics; (3) to increase knowledge of the human gene pathways influencing the pathogenesis of tic disorders; and (4) to develop prediction models for the risk of onset and exacerbations of tic disorders. The EMTICS study is, to our knowledge, the largest prospective cohort assessment of the contribution of different genetic and environmental factors to the risk of developing tics in putatively predisposed individuals and to the risk of exacerbating tics in young individuals with chronic tic disorders.
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http://dx.doi.org/10.1007/s00787-018-1190-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6349795PMC
January 2019

Neonatal corticosterone mitigates autoimmune neuropsychiatric disorders associated with streptococcus in mice.

Sci Rep 2018 07 5;8(1):10188. Epub 2018 Jul 5.

Centre for Behavioural Sciences and Mental Health, Istituto Superiore di Sanità, Roma, Italy.

Increased glucocorticoid concentrations have been shown to favor resilience towards autoimmune phenomena. Here, we addressed whether experimentally induced elevations in circulating glucocorticoids mitigate the abnormalities exhibited by an experimental model of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus (PANDAS). This is a pathogenic hypothesis linking repeated exposures to Group-A-beta-hemolytic streptococcus (GAS), autoantibodies targeting selected brain nuclei and neurobehavioral abnormalities. To persistently elevate glucocorticoid concentrations, we supplemented lactating SJL/J mice with corticosterone (CORT; 80 mg/L) in the drinking water. Starting in adolescence (postnatal day 28), developing offspring were exposed to four injections - at bi-weekly intervals - of a GAS homogenate and tested for behavioral, immunological, neurochemical and molecular alterations. GAS mice showed increased perseverative behavior, impaired sensorimotor gating, reduced reactivity to a serotonergic agonist and inflammatory infiltrates in the anterior diencephalon. Neonatal CORT persistently increased circulating glucocorticoids concentrations and counteracted these alterations. Additionally, neonatal CORT increased peripheral and CNS concentrations of the anti-inflammatory cytokine IL-9. Further, upstream regulator analysis of differentially expressed genes in the striatum showed that the regulatory effect of estradiol is inhibited in GAS-treated mice and activated in GAS-treated mice exposed to CORT. These data support the hypothesis that elevations in glucocorticoids may promote central immunomodulatory processes.
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http://dx.doi.org/10.1038/s41598-018-28372-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033871PMC
July 2018

Fighting Antibiotic-Resistant Klebsiella pneumoniae with "Sweet" Immune Targets.

mBio 2018 05 15;9(3). Epub 2018 May 15.

GSK, Siena, Italy

Antibiotics and vaccines have greatly impacted human health in the last century by dramatically reducing the morbidity and mortality associated with infectious diseases. The recent challenge posed by the emergence of multidrug-resistant bacteria could possibly be addressed by novel immune prophylactic and therapeutic approaches. Among the newly threatening pathogens, is particularly worrisome in the nosocomial setting, and its surface polysaccharides are regarded as promising antigen candidates. The majority of carbapenem-resistant strains belong to the sequence type 158 (ST258) lineage, with two main clades expressing capsular polysaccharides CPS1 and CPS2. In a recent article, S. D. Kobayashi and colleagues (mBio 9:e00297-18, 2018, https://doi.org/10.1128/mBio.00297-18) show that CPS2-specific IgGs render ST258 clade 2 bacteria more sensitive to human serum and phagocytic killing. E. Diago-Navarro et al. (mBio 9:e00091-18, 2018, https://doi.org/10.1128/mBio.00091-18) generated two murine monoclonal antibodies recognizing distinct glycotopes of CPS2 that presented functional activity against multiple ST258 strains. These complementary studies represent a step toward the control of this dangerous pathogen.
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http://dx.doi.org/10.1128/mBio.00874-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5954227PMC
May 2018

Protective effect of Group B Streptococcus type-III polysaccharide conjugates against maternal colonization, ascending infection and neonatal transmission in rodent models.

Sci Rep 2018 02 7;8(1):2593. Epub 2018 Feb 7.

GSK, Siena, Italy.

Group B Streptococcus (GBS) is a normal inhabitant of recto-vaginal mucosae in up to 30% of healthy women. Colonization is a major risk factor for perinatal infection which can lead to severe complications such as stillbirth and neonatal invasive disease. Intra-partum antibiotic prophylaxis in colonized women is a safe and cost-effective preventive measure against early-onset disease in the first days of life, but has no effect on late-onset manifestations or on early maternal infection. Maternal immunization with capsular polysaccharide-based vaccines shows promise for the prevention of both early-onset and late-onset neonatal infections, although ability to prevent maternal colonization and ascending infection has been less studied. Here we investigated the effect of a GBS glycoconjugate vaccine since the very early stage of maternal GBS acquisition to neonatal outcome by rodent models of vaginal colonization and ascending infection. Immunization of female mice and rats with a type III glycoconjugate reduced vaginal colonization, infection of chorioamniotic/ placental membranes and bacterial transmission to fetuses and pups. Type III specific antibodies were detected in the blood and vagina of vaccinated mothers and their offspring. The obtained data support a potential preventive effect of GBS glycoconjugate vaccines during the different stages of pregnancy.
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http://dx.doi.org/10.1038/s41598-018-20609-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5803199PMC
February 2018

Functional activity of maternal and cord antibodies elicited by an investigational group B Streptococcus trivalent glycoconjugate vaccine in pregnant women.

J Infect 2018 05 31;76(5):449-456. Epub 2018 Jan 31.

GSK + Novartis Vaccines and Diagnostics, Siena, Italy. Electronic address:

Objectives: The main aim of this exploratory study was to evaluate functional activity of antibodies elicited by a maternal Group B Streptococcus (GBS) investigational vaccine composed of capsular polysaccharides Ia, Ib, and III conjugated to genetically detoxified Diphtheria toxin CRM. The second objective was to investigate the relationship between serotype-specific IgG concentrations and functional activity in maternal and cord sera.

Methods: Maternal and cord sera collected at baseline and at delivery from vaccine and placebo recipients during a double-blind placebo-controlled Phase II study (www.clinicaltrials.gov, NCT01446289) were tested in an opsono-phagocytic bacterial killing assay. Cord sera from vaccine recipients were also passively transferred to newborn mice to investigate conferred protection against bacterial challenge.

Results: Antibody-mediated GBS phagocytic killing was significantly increased in maternal serum at delivery and in cord sera from the investigational vaccine group as compared to the placebo group. Anti-capsular IgG concentrations above 1 µg/mL mediated in vitro killing against GBS strains belonging to all three serotypes and IgG levels correlated with functional titers. Passively administered cord sera elicited a dose-dependent protective response against all GBS serotypes in the in vivo model.

Conclusions: The maternal vaccine elicited functional antibodies that were placentally transferred. Anti-capsular IgG concentrations in maternal and cord sera were predictive of functional activity and in vivo protection in the mouse model.
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http://dx.doi.org/10.1016/j.jinf.2018.01.006DOI Listing
May 2018

Contribution of pilus type 2b to invasive disease caused by a Streptococcus agalactiae ST-17 strain.

BMC Microbiol 2017 07 3;17(1):148. Epub 2017 Jul 3.

GSK S.r.l., Siena, Italy.

Background: Group B Streptococcus (GBS) is a major cause of invasive disease especially in neonates. In GBS three structurally distinct pilus polymers have been identified as important virulence factors and promising vaccine candidates. The vast majority of Group B Streptococci belonging to the hypervirulent serotype III ST-17 lineage bear pilus types 1 and 2b. The purpose of this study was to investigate the relative contribution of these two pilus types to the pathogenesis of a ST-17 strain.

Results: We performed in vivo and in vitro analysis of isogenic knockout mutants derived from the GBS COH1 ST-17 strain deprived of either pilus type 1 or 2b. We compared the two pilus mutants with the wild type strain in a mouse model of invasive disease, in vitro survival in macrophages, and adherence/invasion assays using human brain endothelial and lung epithelial cell lines. Significantly less of the pilus 2b mutant was recovered from the blood, lungs and brain tissue of infected mice compared to the wild-type and pilus 1 mutant strains. Further, while the pilus 2b mutant survived similarly in murine macrophages, it exhibited a lower capacity to adhere and invade human brain epithelial and lung endothelial cell lines.

Conclusions: The data suggest an important role of pilus 2b in mediating GBS infection and host cell interaction of strains belonging to the hypervirulent GBS ST-17 lineage.
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http://dx.doi.org/10.1186/s12866-017-1057-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5496222PMC
July 2017

Structure of a protective epitope of group B type III capsular polysaccharide.

Proc Natl Acad Sci U S A 2017 05 24;114(19):5017-5022. Epub 2017 Apr 24.

GSK Vaccines, 53100 Siena, Italy

Despite substantial progress in the prevention of group B (GBS) disease with the introduction of intrapartum antibiotic prophylaxis, this pathogen remains a leading cause of neonatal infection. Capsular polysaccharide conjugate vaccines have been tested in phase I/II clinical studies, showing promise for further development. Mapping of epitopes recognized by protective antibodies is crucial for understanding the mechanism of action of vaccines and for enabling antigen design. In this study, we report the structure of the epitope recognized by a monoclonal antibody with opsonophagocytic activity and representative of the protective response against type III GBS polysaccharide. The structure and the atomic-level interactions were determined by saturation transfer difference (STD)-NMR and X-ray crystallography using oligosaccharides obtained by synthetic and depolymerization procedures. The GBS PSIII epitope is made by six sugars. Four of them derive from two adjacent repeating units of the PSIII backbone and two of them from the branched galactose-sialic acid disaccharide contained in this sequence. The sialic acid residue establishes direct binding interactions with the functional antibody. The crystal structure provides insight into the molecular basis of antibody-carbohydrate interactions and confirms that the conformational epitope is not required for antigen recognition. Understanding the structural basis of immune recognition of capsular polysaccharide epitopes can aid in the design of novel glycoconjugate vaccines.
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http://dx.doi.org/10.1073/pnas.1701885114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441712PMC
May 2017

Immunogenicity and protective efficacy induced by self-amplifying mRNA vaccines encoding bacterial antigens.

Vaccine 2017 01 7;35(2):361-368. Epub 2016 Dec 7.

GSK Vaccines S.r.l., Via Fiorentina 1, 53100 Siena, Italy. Electronic address:

Nucleic acid vaccines represent an attractive approach to vaccination, combining the positive attributes of both viral vectors and live-attenuated vaccines, without the inherent limitations of each technology. We have developed a novel technology, the Self-Amplifying mRNA (SAM) platform, which is based on the synthesis of self-amplifying mRNA formulated and delivered as a vaccine. SAM vaccines have been shown to stimulate robust innate and adaptive immune responses in small animals and non-human primates against a variety of viral antigens, thus representing a safe and versatile tool against viral infections. To assess whether the SAM technology could be used for a broader range of targets, we investigated the immunogenicity and efficacy of SAM vaccines expressing antigens from Group A (GAS) and Group B (GBS) Streptococci, as models of bacterial pathogens. Two prototype bacterial antigens (the double-mutated GAS Streptolysin-O (SLOdm) and the GBS pilus 2a backbone protein (BP-2a)) were successfully expressed by SAM vectors. Mice immunized with both vaccines produced significant amounts of fully functional serum antibodies. The antibody responses generated by SAM vaccines were capable of conferring consistent protection in murine models of GAS and GBS infections. Inclusion of a eukaryotic secretion signal or boosting with the recombinant protein resulted in higher specific-antibody levels and protection. Our results support the concept of using SAM vaccines as potential solution for a wide range of both viral and bacterial pathogens, due to the versatility of the manufacturing processes and the broad spectrum of elicited protective immune response.
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http://dx.doi.org/10.1016/j.vaccine.2016.11.040DOI Listing
January 2017

Immune Responses to Invasive Group B Streptococcal Disease in Adults.

Emerg Infect Dis 2016 11;22(11):1877-1883

Immunization of nonpregnant adults could help prevent invasive group B Streptococcus (GBS) infections, but adult immune responses have not been investigated. We defined capsular polysaccharide (CPS) and pilus island (PI) surface antigen distribution and expression and immune responses to GBS infection in nonpregnant adults. Prospective surveillance from 7 hospitals in Houston, Texas, USA, identified 102 adults with GBS bacteremia; 43% had skin/soft tissue infection, 16% bacteremia without focus, and 12% osteomyelitis. CPS-specific IgG was determined by ELISA and pilus-specific IgG by multiplex immunoassay. CPS types were Ia (24.5%), Ib (12.7%), II (9.8%), III (16.7%), IV (13.7%), and V (12.7%); 9.8% were nontypeable by serologic methods. Pili, expressed by 89%, were most often PI-2a. CPS and pilus-specific IgG increased during convalescence among patients with strains expressing CPS or PI. All GBS expressed CPS or PI; 79% expressed both. Increased antibodies to CPS and PI during recovery suggests that GBS bacteremia in adults is potentially vaccine preventable.
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http://dx.doi.org/10.3201/eid2211.160914DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5088039PMC
November 2016

Genomic Analysis Reveals Multi-Drug Resistance Clusters in Group B Streptococcus CC17 Hypervirulent Isolates Causing Neonatal Invasive Disease in Southern Mainland China.

Front Microbiol 2016 15;7:1265. Epub 2016 Aug 15.

GlaxoSmithKline Vaccines S.r.l., Siena Italy.

Neonatal invasive disease caused by group B Streptococcus (GBS) represents a significant public health care concern globally. However, data related to disease burden, serotype distribution, and molecular epidemiology in China and other Asian countries are very few and specifically relative to confined regions. The aim of this study was to investigate the genetic characteristics of GBS isolates recovered from neonates with invasive disease during 2013-2014 at Guangzhou and Changsha hospitals in southern mainland China. We assessed the capsular polysaccharide type, pilus islands (PIs) distribution and hvgA gene presence in a panel of 26 neonatal clinical isolates, of which 8 were recovered from Early Onset Disease and 18 from Late Onset Disease (LOD). Among 26 isolates examined, five serotypes were identified. Type III was the most represented (15 cases), particularly among LOD strains (n = 11), followed by types Ib (n = 5), V (n = 3), Ia (n = 2) and II (n = 1). We performed whole-genome sequencing analysis and antimicrobial susceptibility testing on the 14 serotype III isolates belonging to the hypervirulent Clonal Complex 17 (serotype III-CC17). The presence of PI-2b alone was associated with 13 out of 14 serotype III-CC17 strains. Genome analysis led us to identify two multi-drug resistance gene clusters harbored in two new versions of integrative and conjugative elements (ICEs), carrying five or eight antibiotic resistance genes, respectively. These ICEs replaced the 16 kb-locus that normally contains the PI-1 operon. All isolates harboring the identified ICEs showed multiple resistances to aminoglycoside, macrolide, and tetracycline antibiotic classes. In conclusion, we report the first whole-genome sequence analysis of 14 GBS serotype III-CC17 strains isolated in China, representing the most prevalent lineage causing neonatal invasive disease. The acquisition of newly identified ICEs conferring multiple antibiotic resistance could in part explain the spread of this specific clone among Chinese neonatal isolates and underlines the need for a constant epidemiological surveillance.
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http://dx.doi.org/10.3389/fmicb.2016.01265DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4983569PMC
August 2016

The Protective Value of Maternal Group B Streptococcus Antibodies: Quantitative and Functional Analysis of Naturally Acquired Responses to Capsular Polysaccharides and Pilus Proteins in European Maternal Sera.

Clin Infect Dis 2016 09 11;63(6):746-753. Epub 2016 Jul 11.

GSK Vaccines Srl, Siena.

Background: Group B Streptococcus (GBS) is a major cause of neonatal sepsis and meningitis. A vaccine targeting pregnant women could protect infants through placentally transferred antibodies. The association between GBS maternal antibody concentrations and the risk of neonatal infection has been investigated in US and African populations. Here we studied naturally acquired immunoglobulin G (IgG) responses to GBS capsular polysaccharides (CPS) and pilus proteins in European pregnant women.

Methods: Maternal sera were prospectively collected in 8 EU countries from 473 GBS non-colonized and 984 colonized pregnant women who delivered healthy neonates and from 153 mothers of infants with GBS disease. GBS strains from these colonized women and infected infants were obtained in parallel and their capsular and pilus types were identified by serological and molecular methods. Maternal serum concentrations of IgG anti- Ia, -Ib, -III and -V polysaccharides and anti-BP-1, -AP1-2a and -BP-2b pilus proteins were determined by enzyme-linked immunosorbent assay. Antibody functional activity was quantified by Opsonophagocytic Killing Assay.

Results: Antibody levels against CPS and pilus proteins were significantly higher in GBS colonized women delivering healthy babies than in mothers of neonates with GBS disease or non-colonized women. Moreover, maternal anti-capsular IgG concentrations showed a significant correlation with functional titers measured by Opsonophagocytic Killing Assay.

Conclusions: Maternal anti-capsular IgG concentrations above 1 µg/mL mediated GBS killing in vitro and were predicted to respectively reduce by 81% (95% confidence interval, 40%-100%) and 78% (45%-100%) the risk of GBS Ia and III early-onset disease in Europe.
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http://dx.doi.org/10.1093/cid/ciw377DOI Listing
September 2016

The Group B Streptococcus-Secreted Protein CIP Interacts with C4, Preventing C3b Deposition via the Lectin and Classical Complement Pathways.

J Immunol 2016 Jan 25;196(1):385-94. Epub 2015 Nov 25.

GSK Vaccines S.r.l., 53100 Siena, Italy

The group B Streptococcus (GBS) is a leading cause of neonatal invasive disease. GBS bacteria are surrounded by a thick capsular polysaccharide that is a potent inhibitor of complement deposition via the alternative pathway. Several of its surface molecules can however activate the classical and lectin complement pathways, rendering this species still vulnerable to phagocytic killing. In this study we have identified a novel secreted protein named complement interfering protein (CIP) that downregulates complement activation via the classical and lectin pathways, but not the alternative pathway. The CIP protein showed high affinity toward C4b and inhibited its interaction with C2, presumably preventing the formation of the C4bC2a convertase. Addition of recombinant CIP to GBS cip-negative bacteria resulted in decreased deposition of C3b on their surface and in diminished phagocytic killing in a whole-blood assay. Our data reveal a novel strategy exploited by GBS to counteract innate immunity and could be valuable for the development of anti-infective agents against this important pathogen.
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http://dx.doi.org/10.4049/jimmunol.1501954DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4683360PMC
January 2016

Estimating the burden of invasive Group B Streptococcal disease in young infants in southern mainland China: an observational study.

Int J Clin Exp Med 2015 15;8(8):13699-707. Epub 2015 Aug 15.

GlaxoSmithKline (China) Investment Co Ltd Shanghai, China.

Objectives: To estimate the incidence, case fatality ratio and serotypes associated with early-onset (EOD) and late-onset (LOD) invasive GBS disease in infants in southern mainland China.

Methods: During the six-month study period, infants aged ≤ 90 days with culture-confirmed GBS disease born in the study hospitals or elsewhere, but presenting to a study hospital, were enrolled. GBS-positive cultures were genotyped, serotyped and sequence typed. The incidence rate was calculated for infants born in the study hospitals, and case fatality ratio and causative serotypes identified for all enrolled GBS cases.

Results: Ten cases were enrolled: 2 EOD cases born in the study hospitals and 8 LOD cases born elsewhere. Incidence rate was 0.28 (95% confidence interval: 0.08-1.03, n = 2/7061 successfully followed-up consenting subjects); no cases resulted in fatality. In the 8 GBS isolates available for typing, 4 serotypes (Ia, Ib, III and V) and 5 multi-locus sequence types (1, 10, 12, 17 and 23) were identified.

Conclusions: This is the first study specifically investigating the incidence of GBS invasive disease in infants in southern mainland China. Incidence and case fatality were low but further research is needed in larger, more diverse cohorts to estimate disease burden for the broader Chinese population.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613000PMC
November 2015

Mice repeatedly exposed to Group-A β-Haemolytic Streptococcus show perseverative behaviors, impaired sensorimotor gating, and immune activation in rostral diencephalon.

Sci Rep 2015 08 25;5:13257. Epub 2015 Aug 25.

Sect. Behavioural Neuroscience, Dept. Cell Biology &Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena, 299, I-00161 Roma, Italy.

Repeated exposure to Group-A β-Haemolytic Streptococcus (GAS) may constitute a vulnerability factor in the onset and course of pediatric motor disturbances. GAS infections/colonization can stimulate the production of antibodies, which may cross the blood brain barrier, target selected brain areas (e.g. basal ganglia), and exacerbate motor alterations. Here, we exposed developing SJL male mice to four injections with a GAS homogenate and evaluated the following domains: motor coordination; general locomotion; repetitive behaviors; perseverative responses; and sensorimotor gating (pre-pulse inhibition, PPI). To demonstrate that behavioral changes were associated with immune-mediated brain alterations, we analyzed, in selected brain areas, the presence of infiltrates and microglial activation (immunohistochemistry), monoamines (HPLC), and brain metabolites (in vivo Magnetic Resonance Spectroscopy). GAS-exposed mice showed increased repetitive and perseverative behaviors, impaired PPI, and reduced concentrations of serotonin in prefrontal cortex, a brain area linked to the behavioral domains investigated, wherein they also showed remarkable elevations in lactate. Active inflammatory processes were substantiated by the observation of infiltrates and microglial activation in the white matter of the anterior diencephalon. These data support the hypothesis that repeated GAS exposure may elicit inflammatory responses in brain areas involved in motor control and perseverative behavior, and result in phenotypic abnormalities.
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http://dx.doi.org/10.1038/srep13257DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4548234PMC
August 2015

Group B streptococcal infections in the newborn infant and the potential value of maternal vaccination.

Expert Rev Anti Infect Ther 2015 20;13(11):1387-99. Epub 2015 Aug 20.

a 1 Terapia Intensiva Neonatale, Azienda Ospedaliero-Universitaria Policlinico, Modena, Italy.

Group B Streptococcus (GBS) is a leading cause of neonatal bacterial infections in developed countries. Early-onset disease (EOD) occurs at day 0-6 and late-onset disease occurs at day 7-89. Currently, the prevention of EOD relies upon intrapartum antibiotic prophylaxis (IAP) given to women who are GBS positive at prenatal screening or women with risk factors for EOD. Although successfully implemented, IAP has not fully eradicated EOD, and incidence rates of late-onset disease remain unchanged. Furthermore, antibiotic resistance may result from widespread antibiotic use. New prophylactic strategies are therefore of critical importance. A vaccine active against GBS, administered during pregnancy and combined with targeted IAP, could overcome these problems and reduce the mortality and morbidity associated with invasive diseases.
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http://dx.doi.org/10.1586/14787210.2015.1079126DOI Listing
July 2016

Exploring the Effect of Conjugation Site and Chemistry on the Immunogenicity of an anti-Group B Streptococcus Glycoconjugate Vaccine Based on GBS67 Pilus Protein and Type V Polysaccharide.

Bioconjug Chem 2015 Aug 31;26(8):1839-49. Epub 2015 Jul 31.

‡Novartis Institutes for BioMedical Research, 100 Technology Square, Cambridge, Massachusetts 02139, United States.

We have recently described a method for tyrosine-ligation of complex glycans that was proven efficient for the site selective coupling of GBS capsular polysaccharides (PSs). Herein, we explored the effect of conjugation of type V polysaccharide onto predetermined lysine or tyrosine residues of the GBS67 pilus protein with the dual role of T-cell carrier for the PS and antigen. For the preparation of a conjugate at predetermined lysine residues of the protein, we investigated a two-step procedure based on microbial Transglutaminase (mTGase) catalyzed insertion of a tag bearing an azide for following copper-free strain-promoted azide-alkyne [3 + 2] cycloaddition (SPAAC) with the polysaccharide. Two glycoconjugates were obtained by tyrosine-ligation through the known SPAAC and a novel thiol-maleimide addition based approach. Controls were prepared by random conjugation of PSV to GBS67 and CRM197, a carrier protein present in many commercial vaccines. Immunological evaluation in mice showed that all the site-directed constructs were able to induce good levels of anti-polysaccharide and anti-protein antibodies inducing osponophagocytic killing of strains expressing individually PSV or GBS67. GBS67 randomly conjugated to PSV showed carrier properties similar to CRM197. Among the tested site-directed conjugates, tyrosine-directed ligation and thiol-malemide addition was elected as the best combination to ensure production of anti-polysaccharide and anti-protein functional antibodies (in vitro opsonophagocytic killing titers) comparable to the controls made by random conjugation, while avoiding anti-linker antibodies. Our findings demonstrate that (i) mTGase based conjugation at lysine residues is an alternative approach for the synthesis of large capsular polysaccharide-protein conjugates; (ii) GBS67 can be used with the dual role of antigen and carrier for PSV; and (iii) thiol-maleimide addition in combination with tyrosine-ligation ensures the production of anti-polysaccharide and anti-protein functional antibodies while maintaining low levels of anti-linker antibodies. Site-specific conjugation methods aid in defining conjugation site and chemistry in carbohydrate-protein conjugates.
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http://dx.doi.org/10.1021/acs.bioconjchem.5b00365DOI Listing
August 2015

Noncanonical sortase-mediated assembly of pilus type 2b in group B Streptococcus.

FASEB J 2015 Nov 22;29(11):4629-40. Epub 2015 Jul 22.

*Novartis Vaccines and Diagnostics, GlaxoSmithKline, Siena, Italy; and Nuclear Magnetic Resonance Laboratory, Department of Biotechnology, University of Verona, Verona, Italy

Group B Streptococcus (GBS) expresses 3 structurally distinct pilus types (1, 2a, and 2b) identified as important virulence factors and vaccine targets. These pili are heterotrimeric polymers, covalently assembled on the cell wall by sortase (Srt) enzymes. We investigated the pilus-2b biogenesis mechanism by using a multidisciplinary approach integrating genetic, biochemical, and structural studies to dissect the role of the 2 pilus-2b-associated Srts. We show that only 1 sortase (SrtC1-2b) is responsible for pilus protein polymerization, whereas the second one (Srt2-2b) does not act as a pilin polymerase, but similarly to the housekeeping class A Srt (SrtA), it is involved in cell-wall pilus anchoring by targeting the minor ancillary subunit. Based on its function and sequence features, Srt2-2b does not belong to class C Srts (SrtCs), nor is it a canonical member of any other known family of Srts. We also report the crystal structure of SrtC1-2b at 1.9 Å resolution. The overall fold resembles the typical structure of SrtCs except for the N-terminal lid region that appears in an open conformation displaced from the active site. Our findings reveal that GBS pilus type 2b biogenesis differs significantly from the current model of pilus assembly in gram-positive pathogens.
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http://dx.doi.org/10.1096/fj.15-272500DOI Listing
November 2015

The Human Pathogen Streptococcus pyogenes Releases Lipoproteins as Lipoprotein-rich Membrane Vesicles.

Mol Cell Proteomics 2015 Aug 27;14(8):2138-49. Epub 2015 May 27.

From the ‡Novartis Vaccines and Diagnostics (a GSK company), Via Fiorentiina 1, 53100 Siena, Itlay;

Bacterial lipoproteins are attractive vaccine candidates because they represent a major class of cell surface-exposed proteins in many bacteria and are considered as potential pathogen-associated molecular patterns sensed by Toll-like receptors with built-in adjuvanticity. Although Gram-negative lipoproteins have been extensively characterized, little is known about Gram-positive lipoproteins. We isolated from Streptococcus pyogenes a large amount of lipoproteins organized in vesicles. These vesicles were obtained by weakening the bacterial cell wall with a sublethal concentration of penicillin. Lipid and proteomic analysis of the vesicles revealed that they were enriched in phosphatidylglycerol and almost exclusively composed of lipoproteins. In association with lipoproteins, a few hypothetical proteins, penicillin-binding proteins, and several members of the ExPortal, a membrane microdomain responsible for the maturation of secreted proteins, were identified. The typical lipidic moiety was apparently not necessary for lipoprotein insertion in the vesicle bilayer because they were also recovered from the isogenic diacylglyceryl transferase deletion mutant. The vesicles were not able to activate specific Toll-like receptor 2, indicating that lipoproteins organized in these vesicular structures do not act as pathogen-associated molecular patterns. In light of these findings, we propose to name these new structures Lipoprotein-rich Membrane Vesicles.
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http://dx.doi.org/10.1074/mcp.M114.045880DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528243PMC
August 2015