Functional Analysis of Bacillus anthracis Protective Antigen by Using Neutralizing Monoclonal Antibodies

Protective antigen (PA) is central to the action of the lethal and edema toxins produced by Bacillus anthracis. It is the common cell-binding component, mediating the translocation of the enzymatic moieties (lethal factor [LF] and edema factor) into the cytoplasm of the host cell. Monoclonal antibodies (MAbs) against PA, able to neutralize the activities of the toxins in vitro and in vivo, were screened. Two such MAbs, named 7.5 and 48.3, were purified and further characterized. MAb 7.5 binds to domain 4 of PA and prevents the binding of PA to its cell receptor. MAb 48.3 binds to domain 2 and blocks the cleavage of PA into PA63, a step necessary for the subsequent interaction with the enzymatic moieties. The epitope recognized by this antibody is in a region involved in the oligomerization of PA63; thus, MAb 48.3 does not recognize the oligomer form. MAbs 7.5 and 48.3 neutralize the activities of anthrax toxins produced by B. anthracis in mice. Also, there is an additive effect between the two MAbs against PA and a MAb against LF, in protecting mice against a lethal challenge by the Sterne strain. This work contributes to the functional analysis of PA and offers immunotherapeutic perspectives for the treatment of anthrax disease

Bordetella parapertussis Bacteremia: Clinical Expression and Bacterial Genomics

International audienceWhooping cough's primary etiological agent is Bordetella pertussis. The closely related Bordetella parapertussis rarely causes severe disease. Here we report an unusual case of bacteremia caused by B. parapertussis, review the literature, and characterize the genomic sequence of the bacterial isolate in comparison with B. parapertussis isolates from respiratory infections

Genomic Sequencing of Bordetella pertussis for Epidemiology and Global Surveillance of Whooping Cough

Bordetella pertussis causes whooping cough, a highly contagious respiratory disease that is reemerging in many world regions. The spread of antigen-deficient strains may threaten acellular vaccine efficacy. Dynamics of strain transmission are poorly defined because of shortcomings in current strain genotyping methods. Our objective was to develop a whole-genome genotyping strategy with sufficient resolution for local epidemiologic questions and sufficient reproducibility to enable international comparisons of clinical isolates. We defined a core genome multilocus sequence typing scheme comprising 2,038 loci and demonstrated its congruence with whole-genome single-nucleotide polymorphism variation. Most cases of intrafamilial groups of isolates or of multiple isolates recovered from the same patient were distinguished from temporally and geographically cocirculating isolates. However, epidemiologically unrelated isolates were sometimes nearly undistinguishable. We set up a publicly accessible core genome multilocus sequence typing database to enable global comparisons of B. pertussis isolates, opening the way for internationally coordinated surveillance

Anopheles gambiae maternal age and parous state control offspring susceptibility to Plasmodium falciparum

Maternal effects have been reported in many organisms whereby exposure to environmental stress, either toxics or pathogens will impact on progeny response to these stresses. Here we show that Anopheles gambiae susceptibility to Plasmodium falciparum is dependent upon maternal effects driven by females not previously exposed to the parasite. The maternal effect involved both mother age and reproductive state. Offspring of old females or from a 4 th gonotrophic cycle are more susceptible than offspring from young females. These maternal effects also contribute to overall better fitness of the offspring. As mosquito population age structure contributes heavily shaping malaria transmission, consequences of this novel finding should be taken into account in further strategies for controlling malaria transmission

Evolution of Bordetella pertussis over a 23-year period in France, 1996 to 2018

International audienceBackground: Bordetella pertussis is the main agent of whooping cough. Vaccination with acellular pertussis vaccines has been largely implemented in high-income countries. These vaccines contain 1 to 5 antigens: pertussis toxin (PT), filamentous haemagglutinin (FHA), pertactin (PRN) and/or fimbrial proteins (FIM2 and FIM3). Monitoring the emergence of B. pertussis isolates that might partially escape vaccine-induced immunity is an essential component of public health strategies to control whooping cough. Aim: We aimed to investigate temporal trends of fimbriae serotypes and vaccine antigenexpression in B. pertussis over a 23-year period in France (1996-2018). Methods: Isolates (n = 2,280) were collected through hospital surveillance, capturing one third of hospitalised paediatric pertussis cases. We assayed PT, FHA and PRN production by Western blot (n = 1,428) and fimbriae production by serotyping (n = 1,058). Molecular events underlying antigen deficiency were investigated by genomic sequencing

Structure and function of the Leptospira interrogans peroxide stress regulator (PerR), an atypical PerR devoid of a structural metal-binding site

International audiencePeroxide sensing is essential for bacterial survival during aerobic metabolism and host infection. Peroxide stress regulators (PerRs) are homodimeric transcriptional repressors with each monomer typically containing both structural and regulatory metal-binding sites. PerR binding to gene promoters is controlled by the presence of iron in the regulatory site, and iron-catalyzed oxidation of PerR by H2O2 leads to the dissociation of PerR from DNA. In addition to a regulatory metal, most PerRs require a structural metal for proper dimeric assembly. We present here a structural and functional characterization of the PerR from the pathogenic spirochete Leptospira interrogans, a rare example of PerR lacking a structural metal-binding site. In vivo studies showed that the leptospiral PerR belongs to the peroxide stimulon in pathogenic species and is involved in controlling resistance to peroxide. Moreover, a perR mutant had decreased fitness in other host-related stress conditions, including at 37 °C or in the presence of superoxide anion. In vitro, leptospiral PerR could bind to the perR promoter region in a metal-dependent manner. The crystal structure of the leptospiral PerR revealed an asymmetric homodimer, with one monomer displaying complete regulatory metal coordination in the characteristic caliper-like DNA-binding conformation and the second monomer exhibiting disrupted regulatory metal coordination in an open non-DNA-binding conformation. This structure showed that leptospiral PerR assembles into a dimer in which a metal-induced conformational switch can occur independently in the two monomers. Our study demonstrates that structural metal binding is not compulsory for PerR dimeric assembly and for regulating peroxide stress

Corynebacterium ramonii sp. nov., a novel toxigenic member of the Corynebacterium diphtheriae species complex

International audienceThe Corynebacterium diphtheriae species complex comprises seven bacterial species, including Corynebacterium ulcerans, a zoonotic pathogen from multiple animal species. In this work, we characterise phenotypically and genotypically isolates belonging to two C. ulcerans lineages. Results from phylogenetic analyses, in silico DNA-DNA hybridization (DDH) and MALDI-TOF spectra differentiate lineage 2 from C. ulcerans lineage 1, which, together with their distinct transmission dynamics (human-to-human vs animal-to-human), indicates that lineage 2 is a separate Corynebacterium species, which we propose to name Corynebacterium ramonii. This species is of particular medical interest considering that its human-to-human transmission is likely, and that some C. ramonii isolates carry the diphtheria toxin gene

A comprehensive resource for Bordetella genomic epidemiology and biodiversity studies

International audienceThe genus Bordetella includes bacteria that are found in the environment and/or associated with humans and other animals. A few closely related species, including Bordetella pertussis , are human pathogens that cause diseases such as whooping cough. Here, we present a large database of Bordetella isolates and genomes and develop genotyping systems for the genus and for the B. pertussis clade. To generate the database, we merge previously existing databases from Oxford University and Institut Pasteur, import genomes from public repositories, and add 83 newly sequenced B. bronchiseptica genomes. The public database currently includes 2582 Bordetella isolates and their provenance data, and 2085 genomes ( https://bigsdb.pasteur.fr/bordetella/ ). We use core-genome multilocus sequence typing (cgMLST) to develop genotyping systems for the whole genus and for B. pertussis , as well as specific schemes to define antigenic, virulence and macrolide resistance profiles. Phylogenetic analyses allow us to redefine evolutionary relationships among known Bordetella species, and to propose potential new species. Our database provides an expandable resource for genotyping of environmental and clinical Bordetella isolates, thus facilitating evolutionary and epidemiological research on whooping cough and other Bordetella infections