ABSTRACT
Migration and homing of immune cells are critical for immune surveillance. Trafficking is mediated by combinations of adhesion and chemokine receptors that guide immune cells, in response to chemokine signals, to specific locations within tissues and the lymphatic system to support tissue-localized immune reactions and systemic immunity1,2. Here we show that disruption of leukaemia inhibitory factor (LIF) production from group 2 innate lymphoid cells (ILC2s) prevents immune cells leaving the lungs to migrate to the lymph nodes (LNs). In the absence of LIF, viral infection leads to plasmacytoid dendritic cells (pDCs) becoming retained in the lungs where they improve tissue-localized, antiviral immunity, whereas chronic pulmonary allergen challenge leads to marked immune cell accumulation and the formation of tertiary lymphoid structures in the lung. In both cases immune cells fail to migrate to the lymphatics, leading to highly compromised LN reactions. Mechanistically, ILC2-derived LIF induces the production of the chemokine CCL21 from lymphatic endothelial cells lining the pulmonary lymphatic vessels, thus licensing the homing of CCR7+ immune cells (including dendritic cells) to LNs. Consequently, ILC2-derived LIF dictates the egress of immune cells from the lungs to regulate tissue-localized versus systemic immunity and the balance between allergen and viral responsiveness in the lungs.
Subject(s)
Cell Movement , Chemokine CCL21 , Dendritic Cells , Immunity, Innate , Leukemia Inhibitory Factor , Lung , Lymph Nodes , Lymphocytes , Mice , Animals , Dendritic Cells/immunology , Lymph Nodes/immunology , Lung/immunology , Lung/virology , Immunity, Innate/immunology , Chemokine CCL21/metabolism , Chemokine CCL21/immunology , Leukemia Inhibitory Factor/metabolism , Leukemia Inhibitory Factor/immunology , Cell Movement/immunology , Female , Lymphocytes/immunology , Lymphocytes/cytology , Male , Receptors, CCR7/metabolism , Receptors, CCR7/immunology , Mice, Inbred C57BL , Allergens/immunology , Endothelial Cells/immunology , Lymphatic Vessels/immunologyABSTRACT
Anaplastic large cell lymphoma (ALCL) is a T-cell malignancy predominantly driven by a hyperactive anaplastic lymphoma kinase (ALK) fusion protein. ALK inhibitors, such as crizotinib, provide alternatives to standard chemotherapy with reduced toxicity and side effects. Children with lymphomas driven by nucleophosmin 1 (NPM1)-ALK fusion proteins achieved an objective response rate to ALK inhibition therapy of 54% to 90% in clinical trials; however, a subset of patients progressed within the first 3 months of treatment. The mechanism for the development of ALK inhibitor resistance is unknown. Through genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) activation and knockout screens in ALCL cell lines, combined with RNA sequencing data derived from ALK inhibitor-relapsed patient tumors, we show that resistance to ALK inhibition by crizotinib in ALCL can be driven by aberrant upregulation of interleukin 10 receptor subunit alpha (IL10RA). Elevated IL10RA expression rewires the STAT3 signaling pathway, bypassing otherwise critical phosphorylation by NPM1-ALK. IL-10RA expression does not correlate with response to standard chemotherapy in pediatric patients, suggesting that a combination of crizotinib and chemotherapy could prevent ALK inhibitor resistance-specific relapse.
Subject(s)
Antineoplastic Agents/pharmacology , Crizotinib/pharmacology , Drug Resistance, Neoplasm/genetics , Interleukin-10 Receptor alpha Subunit/genetics , Lymphoma, Large-Cell, Anaplastic/genetics , Protein Kinase Inhibitors/pharmacology , Protein-Tyrosine Kinases/genetics , Antineoplastic Agents/therapeutic use , CRISPR-Cas Systems , Cell Line , Crizotinib/therapeutic use , Dose-Response Relationship, Drug , Gene Editing , Gene Expression , Humans , Immunohistochemistry , Interleukin-10 Receptor alpha Subunit/metabolism , Lymphoma, Large-Cell, Anaplastic/drug therapy , Lymphoma, Large-Cell, Anaplastic/metabolism , Lymphoma, Large-Cell, Anaplastic/pathology , Models, Biological , Nucleophosmin , Protein Kinase Inhibitors/therapeutic use , Protein-Tyrosine Kinases/metabolism , STAT3 Transcription Factor/metabolism , Signal Transduction/drug effectsABSTRACT
Glaesserella (Haemophilus) parasuis is a commensal bacterium of the upper respiratory tract in pigs and also the causative agent of Glässer's disease, which causes significant morbidity and mortality in pigs worldwide. Isolates are characterized into 15 serovars by their capsular polysaccharide, which has shown a correlation with isolate pathogenicity. To investigate the role the capsule plays in G. parasuis virulence and host interaction, a capsule mutant of the serovar 5 strain HS069 was generated (HS069Δcap) through allelic exchange following natural transformation. HS069Δcap was unable to cause signs of systemic disease during a pig challenge study and had increased sensitivity to complement killing and phagocytosis by alveolar macrophages. Compared with the parent strain, HS069Δcap produced more robust biofilm and adhered equivalently to 3D4/31 cells; however, it was unable to persistently colonize the nasal cavity of inoculated pigs, with all pigs clearing HS069Δcap by 5 days postchallenge. Our results indicate the importance of the capsular polysaccharide to G. parasuis virulence as well as nasal colonization in pigs.
Subject(s)
Haemophilus parasuis/genetics , Animals , Biofilms , Haemophilus Infections/microbiology , Macrophages, Alveolar/microbiology , Phagocytosis/physiology , Swine , Swine Diseases/microbiology , Virulence/geneticsABSTRACT
BACKGROUND: Glaesserella parasuis, the causative agent of GlÓsser's disease, is widespread in swine globally resulting in significant economic losses to the swine industry. Prevention of GlÓsser's disease in pigs has been plagued with an inability to design broadly protective vaccines, as many bacterin based platforms generate serovar or strain specific immunity. Subunit vaccines are of interest to provide protective immunity to multiple strains of G. parasuis. Selected proteins for subunit vaccination should be widespread, highly conserved, and surface exposed. RESULTS: Two candidate proteins for subunit vaccination (RlpB and VacJ) against G. parasuis were identified using random mutagenesis and an in vitro organ culture system. Pigs were vaccinated with recombinant RlpB and VacJ, outer membrane proteins with important contributions to cellular function and viability. Though high antibody titers to the recombinant proteins and increased interferon-γ producing cells were found in subunit vaccinated animals, the pigs were not protected from developing systemic disease. CONCLUSIONS: It appears there may be insufficient RlpB and VacJ exposed on the bacterial surface for antibody to bind, preventing high RlpB and VacJ specific antibody titers from protecting animals from G. parasuis. Additionally, this work confirms the importance of utilizing the natural host species when assessing the efficacy of vaccine candidates.
Subject(s)
Haemophilus Infections/veterinary , Haemophilus parasuis/immunology , Recombinant Proteins/immunology , Swine Diseases/prevention & control , Animals , Antibodies, Bacterial/blood , Bacterial Proteins/immunology , Bacterial Vaccines/immunology , Haemophilus Infections/immunology , Haemophilus Infections/prevention & control , Haemophilus Vaccines/immunology , Haemophilus parasuis/genetics , Serogroup , Sus scrofa , Swine , Swine Diseases/immunology , Swine Diseases/microbiology , Tissue Culture Techniques/veterinary , Vaccination/veterinary , Vaccines, Subunit/administration & dosage , Vaccines, Subunit/immunologyABSTRACT
Haemophilus parasuis is a diverse bacterial species that is found in the upper respiratory tracts of pigs and can also cause Glässer's disease and pneumonia. A previous pangenome study of H. parasuis identified 48 genes that were associated with clinical disease. Here, we describe the development of a generalized linear model (termed a pathotyping model) to predict the potential virulence of isolates of H. parasuis based on a subset of 10 genes from the pangenome. A multiplex PCR (mPCR) was constructed based on these genes, the results of which were entered into the pathotyping model to yield a prediction of virulence. This new diagnostic mPCR was tested on 143 field isolates of H. parasuis that had previously been whole-genome sequenced and a further 84 isolates from the United Kingdom from cases of H. parasuis-related disease in pigs collected between 2013 and 2014. The combination of the mPCR and the pathotyping model predicted the virulence of an isolate with 78% accuracy for the original isolate collection and 90% for the additional isolate collection, providing an overall accuracy of 83% (81% sensitivity and 93% specificity) compared with that of the "current standard" of detailed clinical metadata. This new pathotyping assay has the potential to aid surveillance and disease control in addition to serotyping data.
Subject(s)
Haemophilus Infections/diagnosis , Haemophilus Infections/veterinary , Haemophilus parasuis/genetics , Haemophilus parasuis/pathogenicity , Molecular Diagnostic Techniques/methods , Swine Diseases/diagnosis , Animals , Genome/genetics , Haemophilus Infections/microbiology , Haemophilus parasuis/isolation & purification , Multiplex Polymerase Chain Reaction , Swine , Swine Diseases/microbiology , Virulence/geneticsABSTRACT
Haemophilus parasuis causes Glässer's disease and pneumonia in pigs. Indirect hemagglutination (IHA) is typically used to serotype this bacterium, distinguishing 15 serovars with some nontypeable isolates. The capsule loci of the 15 reference strains have been annotated, and significant genetic variation was identified between serovars, with the exception of serovars 5 and 12. A capsule locus and in silico serovar were identified for all but two nontypeable isolates in our collection of >200 isolates. Here, we describe the development of a multiplex PCR, based on variation within the capsule loci of the 15 serovars of H. parasuis, for rapid molecular serotyping. The multiplex PCR (mPCR) distinguished between all previously described serovars except 5 and 12, which were detected by the same pair of primers. The detection limit of the mPCR was 4.29 × 10(5) ng/µl bacterial genomic DNA, and high specificity was indicated by the absence of reactivity against closely related commensal Pasteurellaceae and other bacterial pathogens of pigs. A subset of 150 isolates from a previously sequenced H. parasuis collection was used to validate the mPCR with 100% accuracy compared to the in silico results. In addition, the two in silico-nontypeable isolates were typeable using the mPCR. A further 84 isolates were analyzed by mPCR and compared to the IHA serotyping results with 90% concordance (excluding those that were nontypeable by IHA). The mPCR was faster, more sensitive, and more specific than IHA, enabling the differentiation of 14 of the 15 serovars of H. parasuis.
Subject(s)
Genotyping Techniques/methods , Haemophilus parasuis/classification , Haemophilus parasuis/genetics , Multiplex Polymerase Chain Reaction/methods , Serotyping/methods , Animals , Bacterial Capsules/genetics , Genetic Loci , Haemophilus Infections/diagnosis , Haemophilus Infections/microbiology , Haemophilus Infections/veterinary , Haemophilus parasuis/isolation & purification , Sensitivity and Specificity , Swine , Swine Diseases/diagnosis , Swine Diseases/microbiology , Time FactorsABSTRACT
BACKGROUND: Haemophilus parasuis is the etiologic agent of Glässer's disease in pigs and causes devastating losses to the farming industry. Whilst some hyper-virulent isolates have been described, the relationship between genetics and disease outcome has been only partially established. In particular, there is weak correlation between serovar and disease phenotype. We sequenced the genomes of 212 isolates of H. parasuis and have used this to describe the pan-genome and to correlate this with clinical and carrier status, as well as with serotype. RESULTS: Recombination and population structure analyses identified five groups with very high rates of recombination, separated into two clades of H. parasuis with no signs of recombination between them. We used genome-wide association methods including discriminant analysis of principal components (DAPC) and generalised linear modelling (glm) to look for genetic determinants of this population partition, serovar and pathogenicity. We were able to identify genes from the accessory genome that were significantly associated with phenotypes such as potential serovar specific genes including capsule genes, and 48 putative virulence factors that were significantly different between the clinical and non-clinical isolates. We also show that the presence of many previously suggested virulence factors is not an appropriate marker of virulence. CONCLUSIONS: These genes will inform the generation of new molecular diagnostics and vaccines, and refinement of existing typing schemes and show the importance of the accessory genome of a diverse species when investigating the relationship between genotypes and phenotypes.
Subject(s)
Genome-Wide Association Study , Haemophilus parasuis/pathogenicity , Animals , Genome, Viral , Haemophilus parasuis/classification , Haemophilus parasuis/genetics , Recombination, Genetic , Swine/virology , Virulence/geneticsABSTRACT
Innate lymphoid cells (ILCs) and adaptive T lymphocytes promote tissue homeostasis and protective immune responses. Their production depends on the transcription factor GATA3, which is further elevated specifically in ILC2s and T helper 2 cells to drive type-2 immunity during tissue repair, allergic disorders, and anti-helminth immunity. The control of this crucial up-regulation is poorly understood. Using CRISPR screens in ILCs we identified previously unappreciated myocyte-specific enhancer factor 2d (Mef2d)-mediated regulation of GATA3-dependent type-2 lymphocyte differentiation. Mef2d-deletion from ILC2s and/or T cells specifically protected against an allergen lung challenge. Mef2d repressed Regnase-1 endonuclease expression to enhance IL-33 receptor production and IL-33 signaling and acted downstream of calcium-mediated signaling to translocate NFAT1 to the nucleus to promote type-2 cytokine-mediated immunity.
Subject(s)
GATA3 Transcription Factor , Immunity, Innate , Interleukin-33 , MEF2 Transcription Factors , NFATC Transcription Factors , Pneumonia , Th2 Cells , Animals , Mice , MEF2 Transcription Factors/metabolism , MEF2 Transcription Factors/genetics , Th2 Cells/immunology , Interleukin-33/metabolism , NFATC Transcription Factors/metabolism , Pneumonia/immunology , GATA3 Transcription Factor/metabolism , GATA3 Transcription Factor/genetics , Mice, Inbred C57BL , Cell Differentiation , Calcium Signaling , Hypersensitivity/immunology , Lung/immunology , Allergens/immunology , Lymphocytes/immunology , Interleukin-1 Receptor-Like 1 ProteinABSTRACT
Haemophilus parasuis is the causative agent of Glässer's disease, a systemic disease of pigs, and is also associated with pneumonia. H. parasuis can be classified into 15 different serovars. Here we report, from the 15 serotyping reference strains, the DNA sequences of the loci containing genes for the biosynthesis of the group 1 capsular polysaccharides, which are potential virulence factors of this bacterium. We contend that these loci contain genes for polysaccharide capsule structures, and not a lipopolysaccharide O antigen, supported by the fact that they contain genes such as wza, wzb, and wzc, which are associated with the export of polysaccharide capsules in the current capsule classification system. A conserved region at the 3' end of the locus, containing the wza, ptp, wzs, and iscR genes, is consistent with the characteristic export region 1 of the model group 1 capsule locus. A potential serovar-specific region (region 2) has been found by comparing the predicted coding sequences (CDSs) in all 15 loci for synteny and homology. The region is unique to each reference strain with the exception of those in serovars 5 and 12, which are identical in terms of gene content. The identification and characterization of this locus among the 15 serovars is the first step in understanding the genetic, molecular, and structural bases of serovar specificity in this poorly studied but important pathogen and opens up the possibility of developing an improved molecular serotyping system, which would greatly assist diagnosis and control of Glässer's disease.
Subject(s)
Bacterial Proteins/genetics , Genetic Variation , Haemophilus parasuis/classification , Haemophilus parasuis/genetics , Polysaccharides, Bacterial/biosynthesis , Swine Diseases/microbiology , Animals , Bacterial Proteins/metabolism , Bacterial Typing Techniques , Haemophilus Infections/microbiology , Haemophilus Infections/veterinary , Haemophilus parasuis/metabolism , Polysaccharides, Bacterial/chemistry , Polysaccharides, Bacterial/genetics , Sequence Analysis, DNA , Serotyping , Species Specificity , Sus scrofa , Swine , Virulence , Virulence Factors/biosynthesis , Virulence Factors/geneticsABSTRACT
Primary effusion lymphoma (PEL) is associated with Kaposi sarcoma herpesvirus (KSHV) but its pathogenesis is poorly understood. Many KSHV-associated products can deregulate cellular pathways commonly targeted in cancer. However, KSHV infection alone is insufficient for malignant transformation. PEL also lacks the chromosomal translocations seen in other lymphoma subtypes. We investigated 28 PELs and ten PEL cell lines by 1 Mb resolution array comparative genomic hybridization (CGH) and found frequent gains of 1q21-41 (47%), 4q28.3-35 (29%), 7q (58%), 8q (63%), 11 (32%), 12 (61%), 17q (29%), 19p (34%), and 20q (34%), and losses of 4q (32%), 11q25 (29%), and 14q32 (63%). Recurrent focal amplification was seen at several regions on chromosomes 7, 8, and 12. High-resolution chromosome-specific tile-path array CGH confirmed these findings, and identified selectin-P ligand (SELPLG) and coronin-1C (CORO1C) as the targets of a cryptic amplification at 12q24.11. Interphase FISH and quantitative PCR showed SELPLG/CORO1C amplification (>4 extra copies) and low levels of copy number gain (1-4 extra copies) in 23% of PELs, respectively. Immunohistochemistry revealed strong expression of both SELPLG and coronin-1C in the majority of PELs, irrespective of their gene dosage. SELPLG is critical for cell migration and chemotaxis, while CORO1C regulates actin-dependent processes, thus important for cell motility. Their overexpression in PEL is expected to play an important role in its pathogenesis.
Subject(s)
Gene Amplification , Lymphoma, Primary Effusion/genetics , Membrane Glycoproteins/genetics , Microfilament Proteins/genetics , Cell Movement/genetics , Chromosome Aberrations , Cocarcinogenesis , Comparative Genomic Hybridization/methods , Epstein-Barr Virus Infections/complications , Gene Expression Profiling/methods , Humans , Lymphoma, Primary Effusion/metabolism , Lymphoma, Primary Effusion/virology , Membrane Glycoproteins/metabolism , Microfilament Proteins/metabolism , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Tumor Cells, CulturedABSTRACT
The group II intron (GBSi1) identified downstream of the C5a-peptidase gene (scpB) in a subpopulation of Streptococcus agalactiae isolates is a suggested marker for a separate genetic lineage of serotype III isolates. In the present study two additional copies of GBSi1, one of which not previously described, were identified among serotype III isolates. All intron copies shared a common target site motif. A single copy of GBSi1 was found in a subgroup of serotype II and V isolates. In these isolates, the intron had inserted downstream of scpB, which suggests that this is the primary insertion site for GBSi1. Most bacterial group II introns described to date reside in transposable elements. The scpB locus was found to be flanked by insertion sequences similar to what has been described in an intronless serotype Ia isolate. However, this region contained an additional 2.1 kb DNA fragment present only in intron carrying isolates. This DNA fragment contained a partial transposase and putative plasmid related proteins. This may suggest that GBSi1 once was brought into the S. agalactiae genome by an integrated plasmid.
Subject(s)
DNA, Bacterial/genetics , Introns/genetics , Plasmids/genetics , Streptococcus agalactiae/genetics , Base Sequence , Binding Sites/genetics , Cloning, Molecular , DNA, Bacterial/chemistry , Gene Dosage , Molecular Sequence Data , Mutagenesis, Insertional , Sequence Analysis, DNAABSTRACT
Haemophilus parasuis is an important respiratory tract pathogen of swine and the etiological agent of Glässer's disease. The molecular pathogenesis of H. parasuis is not well studied, mainly due to the lack of efficient tools for genetic manipulation of this bacterium. In this study we describe a Tn5-based random mutagenesis method for use in H. parasuis. A novel chloramphenicol-resistant Tn5 transposome was electroporated into the virulent H. parasuis serovar 5 strain 29755. High transposition efficiency of Tn5, up to 10(4) transformants/µg of transposon DNA, was obtained by modification of the Tn5 DNA in the H. parasuis strain HS071 and establishment of optimal electrotransformation conditions, and a library of approximately 10,500 mutants was constructed. Analysis of the library using transposon-directed insertion-site sequencing (TraDIS) revealed that the insertion of Tn5 was evenly distributed throughout the genome. 10,001 individual mutants were identified, with 1561 genes being disrupted (69.4% of the genome). This newly-developed, efficient mutagenesis approach will be a powerful tool for genetic manipulation of H. parasuis in order to study its physiology and pathogenesis.
Subject(s)
DNA Transposable Elements , Gene Library , Haemophilus parasuis/genetics , Mutagenesis, Insertional/methods , Animals , Bacterial Proteins/genetics , Base Sequence , Electroporation , Haemophilus parasuis/pathogenicity , Humans , Molecular Sequence DataABSTRACT
BACKGROUND: More than half of patients with multiple sclerosis have progressive disease characterised by accumulating disability. The absence of treatments for progressive multiple sclerosis represents a major unmet clinical need. On the basis of evidence that mesenchymal stem cells have a beneficial effect in acute and chronic animal models of multiple sclerosis, we aimed to assess the safety and efficacy of these cells as a potential neuroprotective treatment for secondary progressive multiple sclerosis. METHODS: Patients with secondary progressive multiple sclerosis involving the visual pathways (expanded disability status score 5·5-6·5) were recruited from the East Anglia and north London regions of the UK. Participants received intravenous infusion of autologous bone-marrow-derived mesenchymal stem cells in this open-label study. Our primary objective was to assess feasibility and safety; we compared adverse events from up to 20 months before treatment until up to 10 months after the infusion. As a secondary objective, we chose efficacy outcomes to assess the anterior visual pathway as a model of wider disease. Masked endpoint analyses was used for electrophysiological and selected imaging outcomes. We used piecewise linear mixed models to assess the change in gradients over time at the point of intervention. This trial is registered with ClinicalTrials.gov, number NCT00395200. FINDINGS: We isolated, expanded, characterised, and administered mesenchymal stem cells in ten patients. The mean dose was 1·6×10(6) cells per kg bodyweight (range 1·1-2·0). One patient developed a transient rash shortly after treatment; two patients had self-limiting bacterial infections 3-4 weeks after treatment. We did not identify any serious adverse events. We noted improvement after treatment in visual acuity (difference in monthly rates of change -0·02 logMAR units, 95% CI -0·03 to -0·01; p=0·003) and visual evoked response latency (-1·33 ms, -2·44 to -0·21; p=0·020), with an increase in optic nerve area (difference in monthly rates of change 0·13 mm(2), 0·04 to 0·22; p=0·006). We did not identify any significant effects on colour vision, visual fields, macular volume, retinal nerve fibre layer thickness, or optic nerve magnetisation transfer ratio. INTERPRETATION: Autologous mesenchymal stem cells were safely given to patients with secondary progressive multiple sclerosis in our study. The evidence of structural, functional, and physiological improvement after treatment in some visual endpoints is suggestive of neuroprotection. FUNDING: Medical Research Council, Multiple Sclerosis Society of Great Britain and Northern Ireland, Evelyn Trust, NHS National Institute for Health Research, Cambridge and UCLH Biomedical Research Centres, Wellcome Trust, Raymond and Beverly Sackler Foundation, and Sir David and Isobel Walker Trust.
Subject(s)
Mesenchymal Stem Cell Transplantation/methods , Mesenchymal Stem Cells/physiology , Multiple Sclerosis, Chronic Progressive/drug therapy , Transplantation, Autologous/methods , Vision Disorders/diagnosis , Adult , Feasibility Studies , Female , Humans , Infusions, Intravenous , Leukocytes, Mononuclear/transplantation , Male , Mesenchymal Stem Cell Transplantation/adverse effects , Middle Aged , Multiple Sclerosis, Chronic Progressive/physiopathology , Severity of Illness Index , Transplantation, Autologous/adverse effects , Treatment Outcome , Vision Disorders/drug therapy , Vision Disorders/physiopathologyABSTRACT
The mechanism of chaperonins is still under intense investigation. Earlier studies by others and us on the bacterial chaperonin GroEL points to an active role of chaperonins in unfolding the target protein during initial binding. Here, a natural eukaryotic chaperonin system [tail-less complex polypeptide 1 (TCP-1) ring complex (TRiC) and its target protein actin] was investigated to determine if the active participation of the chaperonin in the folding process is evolutionary-conserved. Using fluorescence resonance energy transfer (FRET) measurements on four distinct doubly fluorescein-labeled variants of actin, we have obtained a fairly detailed map of the structural rearrangements that occur during the TRiC-actin interaction. The results clearly show that TRiC has an active role in rearranging the bound actin molecule. The target is stretched as a consequence of binding to TRiC and further rearranged in a second step as a consequence of ATP binding; i.e., the mechanism of chaperonins is conserved during evolution.
Subject(s)
Actins/chemistry , Chaperonins/chemistry , Chaperonin Containing TCP-1 , Cloning, Molecular , Electrophoresis, Polyacrylamide Gel , Fluorescence Resonance Energy Transfer , Models, Molecular , Mutagenesis, Site-Directed , Protein ConformationABSTRACT
Streptococcus agalactiae, also designated group B streptococcus (GBS), is an important pathogen in neonates, pregnant women, and nonpregnant adults with predisposing conditions. We used multilocus sequence typing (MLST) to characterize 158 GBS isolates that were associated with neonatal and adult invasive disease and that were collected in northern and western Sweden from 1988 to 1997. Five major genetic lineages (sequence type [ST] 19, ST-17, ST-1, ST-23, and ST-9 complexes) were identified among the isolates, including serotype Ia, Ib, and II to V isolates, indicating a highly clonal population structure among invasive GBS isolates. A number of STs were found to contain isolates of different serotypes, which indicates that capsule switching occurred rather frequently. Two distantly related genetic lineages were identified among isolates of serotype III, namely, clonal complex 19 (CC19), and CC17. CC19 was equally common among isolates from adult and neonatal disease (accounting for 10.3% of GBS isolates from adult disease and 18.7% from neonatal disease), whereas CC17 significantly appeared to be associated with neonatal invasive disease (isolated from 21.9% of neonatal isolates but only 2.6% of adult isolates). The distribution of the mobile elements GBSi1 and IS1548 reveals that they can act as genetic markers for lineages CC17 and CC19, respectively.