BapC autotransporter protein of Bordetella pertussis is an adhesion factor

Bordetella pertussis, the causative agent of whooping cough, attaches to mucosal surfaces in upper respiratory tract, where it produces, a variety of surface-associated and secreted molecules. Among various secreted products, some of the proteins belonging to autotransporter family; pertactin (Prn), bordetella resistance to killing (BrkA) and a newly identified member, bordetella autotransporter protein-C (BapC), are investigated in this study for their adherence potential to various respiratory and non-respiratory tract specific cell lines. Our results reveal that BapC and Prn mutants adhere significantly less (p < 0.0001 and p < 0.05) respectively to human non-respiratory (HeLa-229) and murine macrophages (P-388 D-1) cells compared to their wild-type strains. Prn, BrkA and BapC share no homology in their passenger domains except existence of common motifs arginine-glycine-asparctic (RGD) and glycosaminoglycan binding site (SGXG). We have shown that RGD and SGXG motifs are present in the coiled region in Prn and BrkA proteins with the exception in BapC where R (463) of RGD and S (597) of SGXG motif were observed in beta sheet of the modeled protein structures. Therefore, there is possibility that such arrangement of motifs can confer greater probability of BapC in better selective adherence to binding sites on the HeLa-229 and P-388 D-1 cell lines.     

Development of a real-time PCR for the identification of Bordetella pertussis and Bordetella parapertussis

This study describes a real-time PCR assay for the detection and identification of Bordetella pertussis and Bordetella parapertussis. The assay is based on amplification of a fragment from the repeat sequence regions IS481 and IS1001 found in B. pertussis and B. parapertussis, respectively, with subsequent species identification by melting curve analysis using SYBR Green chemistry. Discrimination between the two species was straightforward, as the corresponding melting points showed a significant difference of 7 degrees C. The assay was evaluated first with reference strains and retrospective human clinical samples, and then prospectively with 132 human clinical specimens received between March 2003 and December 2005. The assay allowed the rapid detection of 22 positive clinical samples, of which 15, including one fatal case, were not identified by standard culture techniques. The new assay was sensitive and specific, and can be implemented easily using any real-time PCR apparatus.     

中国百日咳鲍特菌血清型及其相关基因分析

目的 了解我国1955-2005年临床分离百日咳鲍特菌及疫苗株的血清型及其相关基因特征.方法 应用抗菌毛蛋白2(fim2)和3(fim3)单克隆抗体凝集反应分析我国不同时期分离的80株百日咳鲍特菌株和3株疫苗株的血清型,并与相应的多克隆抗体方法进行比较分析;同时应用PCR方法扩增这些菌株fim2和fimd基因,并对这些PCR产物进行DNA测序分析.结果 研究表明,与多克隆抗体分析结果相比较,单克隆抗体玻片凝集方法和微量凝集反应除一株临床分离株的血清型分析结果不同,其余菌株的结果均一致.研究菌株的血清型分析结果显示17株临床分离菌株和CS与P3S10疫苗株的血清型为fim2&3型、48株菌为fim2型、15株分离菌株与18530疫苗株为fim3型.在我国扩大免疫规划前分离菌株的血清型以fim2型和fim2&3型为主,随着大范围的百日咳疫苗接种,临床分离菌株中fimd型血清型细菌所占的比例逐渐增多.分析菌株中fim2和fimd的基因型以fim2-1(92.5%)和fim3-A(95.0%)亚型为主;18530疫苗株基因型为fim2-2和fim3-A,而其他两株疫苗株的基因型均为fim2-1和fim3-A.在2000年以后,分离出现含有fim3-B和fim3-D亚型菌株,这些结果表明随着我国大范围百日咳疫苗免疫接种,百日咳分离菌株表达的血清型及其基因序列也出现适应性变异.结论 本研究证实了抗fim2和fim3单克隆抗体在百日咳血清型分析的特异性和实用性.对我国不同时期分离菌株和疫苗株的血清型分析,为我国百日咳疫苗株的检定、流行病学和细菌进化的研究奠定了基础.     

Bordetella pertussis TonB, a Bvg-independent virulence determinant

In gram-negative bacteria, high-affinity iron uptake requires the TonB/ExbB/ExbD envelope complex to release iron chelates from their specific outer membrane receptors into the periplasm. Based on sequence similarities, the Bordetella pertussis tonB exbB exbD locus was identified on a cloned DNA fragment. The tight organization of the three genes suggests that they are cotranscribed. A putative Fur-binding sequence located upstream from tonB was detected in a Fur titration assay, indicating that the tonB exbB exbD operon may be Fur-repressed in high-iron growth conditions. Putative structural genes of the beta-subunit of the histone-like protein HU and of a new two-component regulatory system were identified upstream from tonB and downstream from exbD, respectively. A B. pertussis DeltatonB exbB::Km(r) mutant was constructed by allelic exchange and characterized. The mutant was impaired for growth in low-iron medium in vitro and could not use ferrichrome, desferal, or hemin as iron sources. Levels of production of the major bacterial toxins and adhesins were similar in the TonB(+)/TonB(-) pair. The DeltatonB exbB mutant was still responsive to chemical modulators of virulence; thus, the BvgA/BvgS two-component system is not TonB dependent. Nevertheless, in vivo in the mouse respiratory infection model, the colonization ability of the mutant was reduced compared to the parental strain.     

Triplex real‐time PCR assay for detection and differentiation of Bordetella pertussis and Bordetella parapertussis

Xu Y, Xu Y, Hou Q, Yang R, Zhang S. Triplex real‐time PCR assay for detection and differentiation of Bordetella pertussis and Bordetella parapertussis. APMIS 2010; 118: 685–91. A triplex real‐time PCR assay for detection and differentiation of Bordetella pertussis and Bordetella parapertussis was developed. Three targets were used for amplification in a single tube: the insertion sequence IS481 and the pertussis toxin promoter region (ptxP) for B. pertussis, and the insertion sequence IS1001 for B. parapertussis. The performance of this PCR assay was evaluated in parallel in three single‐target real‐time PCR assays using DNA extracted from B. pertussis and B. parapertussis reference strains and nasopharyngeal swabs taken from 105 patients who had been coughing for more than 7 days. The minimum detection limit of the triplex PCR was one to five colony‐forming units (CFU) of B. pertussis and 1 CFU of B. parapertussis per reaction, and the coefficients of both intra‐ and inter‐assay variation were less than 7%. Results were available within 4 h. Of the 105 nasopharyngeal samples, seven were culture positive and 23 were PCR positive for B. pertussis. All culture‐positive samples were also PCR positive. Our single‐tube triplex real‐time PCR assay proved to be sensitive, specific and suitable for simultaneous detection and discrimination of B. pertussis and B. parapertussis.     

Performance of Bordetella pertussis IS481 real-time PCR in a vaccine trial setting

A real-time PCR method targeting the Bordetella pertussis IS481 gene fragment was evaluated in a vaccine trial setting in which real-time PCR results could be validated against culture and serology results. Two commonly used DNA extraction methods, Amplicor Respiratory Preparation kit and the QIAamp DNA Mini Kit, were compared. An approximately 50-fold higher sensitivity was achieved using the Amplicor kit. 89 of 276 aspirates analysed with the IS481 real-time PCR were positive. Interestingly, six of these were culture negative and came from serology-negative patients. Defining true positive cases either as culture-positive or as PCR-positive cases that had been confirmed with a serology-positive result or verified with a newly constructed recA PCR, the sensitivity and specificity of the IS481 real-time PCR were 89% and 98%, respectively. This study confirms the specificity and high diagnostic sensitivity of IS481-based PCR methods for diagnosis of B. pertussis.     

Effect of Bordetella pertussis Vaccination in Mice and the Isolated Tracheal Response to Isoprenaline

The administration of Bordetella pertussis vaccine to mice has been associated with the development of an impaired beta-adrenoceptor responsiveness and in many respects has resembled human asthma. Trachea (n = 12) were isolated from Swiss-Webster mice 5 days following the intraperitoneal administration of 2 x 10(9) B. pertussis organisms. The tracheal smooth muscle response to carbachol was measured and compared with that found in trachea from unvaccinated mice (n = 15). The contractile response was similar in both groups. The tracheal smooth muscle relaxant effects of isoproterenol were measured in these two groups. The EC50 value for isoprenaline (6.5 x 10(-7) M) in trachea from B. pertussis treated mice was significantly (P < 0.05) greater than that noted in the control animals (2.3 x 10(-7) M). These studies demonstrated that in tracheal smooth muscle isolated from B. pertussis vaccinated mice, the relaxant effects of isoprenaline are impaired.     

Comparison of real-time PCR and conventional hemi-nested PCR for the detection of Bordetella pertussis in nasopharyngeal samples

We directly compared a conventional hemi-nested PCR assay with a real-time (LightCycler) PCR assay for the detection of Bordetella pertussis in nasopharyngeal samples. Of the 152 samples tested, 49 (32%) were positive by first-round conventional PCR, 56 (37%) were positive by the hemi-nested PCR assay, and 39 (26%) were positive by the real-time assay. All samples testing positive with the real-time assay were also positive by the hemi-nested assay (both first- and second-round PCR), and all culture-positive samples tested positive by both PCR assays. These results suggest that the hemi-nested assay is more sensitive than the real-time assay for detecting B. pertussis .     

Changes of the Swedish Bordetella pertussis population in incidence peaks during an acellular pertussis vaccine period between 1997 and 2004

In a surveillance programme undertaken from 1997 through 2004, Bordetella pertussis isolates and clinical information were collected after introduction of acellular pertussis vaccines (Pa) in 1996. Changes in the B. pertussis population were studied in three incidence peaks: 1999-2000, 2002 and 2004. Available isolates from 158 fully vaccinated children representing all of Sweden, plus 37 from the Gothenburg area 2003-2004, were analysed by pulsed-field gel electrophoresis (PFGE), serotyping and sequencing of the virulence factor genes pertussis toxin subunits 1 and 3 (ptxA, ptxC), pertactin (prn), tracheal colonisation factor (tcfA) and fimbria3 (fim3). Allele ptxA1 was found in all isolates. There was a statistically significant increasing trend in three out of five studied genes, ptxC, prn and tcfA, and for a fourth, Fim3, if Gothenburg strains were included. The PFGE profile BpSR11 appearing in the 1999-2000 peak dominated by >or=23% during the entire period, bringing with it the allele combination 1/2/2/2/B (ptxA1/ptxC2/prn2/tcfA2/fim3B). Other BpSR11-related profiles with the same allele combination and more than 82% similarity--BpSR5 in the 2002 peak and BpSR12 in the 2004 peak--appeared with an increasing trend. Although vaccination with Pa has reduced disease, new variants have emerged representing clones surviving in the immunized population.     

Attenuated Bordetella pertussis vaccine strain BPZE1 modulates allergen‐induced immunity and prevents allergic pulmonary pathology in a murine model

Background Virulent Bordetella pertussis, the causative agent of whooping cough, exacerbates allergic airway inflammation in a murine model of ovalbumin (OVA) sensitization. A live genetically attenuated B. pertussis mucosal vaccine, BPZE1, has been developed that evokes full protection against virulent challenge in mice but the effect of this attenuated strain on the development of allergic responses is unknown. Objective To assess the influence of attenuated B. pertussis BPZE1 on OVA priming in a murine model of allergic airway inflammation. Methods Mice were challenged with virulent or attenuated strains of B. pertussis, and sensitized to allergen (OVA) at the peak of bacterial carriage. Subsequently, airway pathology, local inflammation and OVA‐specific immunity were examined. Results In contrast to virulent B. pertussis, live BPZE1 did not exacerbate but reduced the airway pathology associated with allergen sensitization. BPZE1 immunization before allergen sensitization did not have an adjuvant effect on allergen specific IgE but resulted in a statistically significant decrease in airway inflammation in tissue and bronchoalveolar lavage fluid. BPZE1 significantly reduced the levels of OVA‐driven IL‐4, IL‐5 and IL‐13 but induced a significant increase in IFN‐γ in response to OVA re‐stimulation. Conclusions These data demonstrate that, unlike virulent strains, the candidate attenuated B. pertussis vaccine BPZE1 does not exacerbate allergen‐driven airway pathology. BPZE1 may represent an attractive T‐helper type 1 promoting vaccine candidate for eradication of whooping cough that is unlikely to promote atopic disease.     

High-resolution melting analysis for the detection of two erythromycin-resistant Bordetella pertussis strains carried by healthy schoolchildren in China

Two erythromycin-resistant strains of Bordetella pertussis were isolated from nasopharyngeal specimens of two asymptomatic schoolchildren in China. High-resolution melting and sequencing analyses confirmed the homogeneous A2047G mutation in 23S rRNA genes of the two isolates. High-resolution melting (HRM) analysis is a useful assay for the rapid detection of erythromycin-resistant B. pertussis. The appearance of erythromycin-resistant B. pertussis strains in China is alarming.     

Bordetella holmesii isolated from a patient with sickle cell anemia: analysis and comparison with other Bordetella holmesii isolates

Objectives To analyze a Bordetella holmesii isolate from a patient with sickle cell anemia and to compare it with other B. holmesii strains and isolates and with strains of B. pertussis and B. bronchiseptica , two well-characterized species of the Bordetella genus.
Methods The bacteriological characteristics and proteins produced by the B. holmesii isolate and the reference strain (ATCC 51541) were analyzed and compared with those of B. pertussis and B. bronchiseptica using sera from patients infected with B. pertussis , B. bronchiseptica or B. holmesii .
Results The bacteriological characteristics of the B. holmesii isolate studied here were similar to those of the B. holmesii reference strain and other isolates. Some of the proteins produced by B. holmesii isolates were similar to those produced by B. pertussis and B. bronchiseptica , but none of these proteins was similar to the toxins and adhesins involved in the pathogenicity of B. pertussis and B. bronchiseptica . The phenotypic diversity of the proteins produced by B. holmesii isolates and the reference strain was striking.
Conclusions Our results suggest that either, the expression of B. holmesii proteins is regulated as in B. pertussis and B. bronchiseptica , with the B. holmesii strain exhibiting different phases, or the proteins produced in B. holmesii are different.     

30 and 32 kDa outer membrane proteins of Bordetella pertussis as a modulator on promoting degranulation of mast cells

Asthma is a common allergic disease of respiratorytract in human,especiallyin children [1-3] ,andcan be classified into 3 clinical types ,immediateasthmatic reaction (IAR) ,late asthmatic reaction(LAR) and biphasic asthmatic reaction(BAR)[4] ,in which approximately 60 %of cases intheworld belong to IgE-mediated IAR[5-7] . By theprevious epidemiological studies ,it was reportedthat respiratory infections by some pathogenic mi-croorganisms, such asBordetella pertussis, in-fluenza virus A o…     

百日咳鲍特菌外膜蛋白体外促肥大细胞脱颗粒的作用

目的了解百日咳鲍特菌Ⅰ相菌株外膜蛋白(outer membrane proteins,OMP)生物学活性与IgE 介导哮喘的关系.方法采用去垢剂处理、DEAE-52和Sephadex G-150层析法制备百日咳鲍特菌Ⅰ相菌株OMP及其组分,以SDS-PAGE估计OMP组分的相对分子质量(Mr).采用ELISA检测百日咳全菌死疫苗诱导动物产生的总IgE和卵白蛋白(ovalbumin,OVA)特异的IgE量.采用肥大细胞脱颗粒试验观察OMP及其组分促进脱颗粒的作用、ELISA检测培养物上清中组胺水平.采用组胺敏感试验检测OMP及其组分增加小鼠对组胺致死敏感性的作用.结果从百日咳鲍特菌OMP中分离获得Mr为(30、32、38和69)×103的4个组分.1～100μg/ml OMP及其组分均未显示凝集鲎变形细胞溶解物的活性.OVA和百日咳鲍特菌联合免疫豚鼠的血清总IgE和OVA特异性IgE较单用OVA免疫有明显增加(t=2.75～6.59;P<0.05～0.01).OMP及其Mr 30×103、Mr 32×103组分有明显的促豚鼠肥大细胞脱颗粒的作用(t=4.914～9.137,P<0.01),但Mr 38×103、Mr 69×103组分无此活性.OMP及其Mr 30×103、Mr 32×103组分处理的上清中组胺水平明显高于阴性对照组(t=5.672～9.304,P<0.01),但Mr 38×103、Mr 69×103组分无此活性.结论百日咳鲍特菌有较强的IgE佐剂活性,某些OMP组分具有促进肥大细胞脱颗粒、组胺释放及增加小鼠对组胺致死敏感性的作用,提示百日咳鲍特菌感染或疫苗接种与IgE介导的哮喘有密切关系.     

Seroprevalence of IgG antibodies against Bordetella pertussis in healthy individuals aged 4–24 years in Turkey

The distribution of IgG antibodies to Bordetella pertussis was investigated in serum samples from 550 subjects, aged 4–24 years, to determine the optimal age for booster immunisation. Levels of antibody to B. pertussis antigens were determined using an ELISA that measures a mixture of pertussis toxin, filamentous haemagglutinin and lipopolysaccharide. Geometric mean titres of anti-pertussis antibodies in subjects aged 4–6 years were significantly lower than those in other age groups, which reflects waning immunity following vaccination. High positive titres in older children and adolescents suggested acquired B. pertussis infection, and booster doses at the ages of 7 and 15 years are therefore suggested.     

Acellular Bordetella pertussis vaccine enhances mucosal interleukin-10 production, induces apoptosis of activated Th1 cells and attenuates colitis in Galphai2-deficient mice

Mice deficient for the inhibitory G protein subunit alpha2 (Galphai2(-/-)) spontaneously develop a progressive inflammatory bowel disease resembling ulcerative colitis, and have a T helper 1 (Th1)-dominated immune response prior to onset of colitis, which is further augmented after the onset of disease. The present study was performed to investigate whether the Galphai2(-/-) mice were able to down-regulate the Th1-dominated inflammatory mucosal immune response and/or induce an anti-inflammatory Th2/T regulatory response and thereby diminish the severity of colitis following treatment with acellular Bordetella pertussis vaccine. The acellular vaccine against B. pertussis, the causative agent of whooping cough, has been demonstrated to induce a Th2-mediated response in both man and mice. We therefore treated Galphai2(-/-) mice intraperitoneally with a three-component acellular B. pertussis vaccine. The treated Galphai2(-/-) mice showed significantly increased interleukin (IL)-10 production in intestinal tissue, associated with significantly reduced colitis and decreased mortality, compared to untreated Galphai2(-/-) mice. The attenuation of colitis in Galphai2(-/-) mice was due, at least partly, to the B. pertussis surface antigen filamentous haemagglutinin (FHA), which almost completely inhibited proliferation of CD4(+) T cells and stimulated apoptosis of activated CD4(+) T helper 1 cells. In conclusion, the three-component acellular B. pertussis vaccine containing filamentous haemagglutinin increases the production of IL-10 in the intestinal mucosa, induces apoptosis of activated Th1 cells and attenuates colitis in Galphai2(-/-) mice.     

A vir-repressed gene of Bordetella pertussis is required for virulence.

Coordinate regulation of gene expression in Bordetella pertussis is controlled by the products of the vir locus, BvgA and BvgS. In the presence of modulating signals such as MgSO4 and nicotinic acid, expression of vir-activated genes (vag) is reduced, while expression of vir-repressed genes (vrg) is maximal. We have cloned one of these vir-repressed genes, vrg-6, in Escherichia coli. DNA sequencing has shown that vrg-6 is contained on a single EcoRI restriction endonuclease fragment and is predicted to code for a protein of 105 amino acids with a molecular weight of 11,441. The predicted protein product appears to have two domains, one consisting of seven hydrophobic proline-rich pentameric repeats and the other consisting of five alkaline trimeric repeats. Southern blot analysis has revealed vrg-6-homologous sequences in the chromosomes of Bordetella bronchiseptica and Bordetella parapertussis, but, unlike Bordetella pertussis, these species do not express vrg-6-homologous RNA when grown under modulating conditions. In order to assess the role of vrg gene products in B. pertussis pathogenesis, two 18323 derivatives which harbor TnphoA insertions in vrg genes were analyzed in a mouse model of respiratory infection. Strain SK6, which carries a vrg-6::TnphoA mutation, failed to induce lymphocytosis and was significantly less able to colonize lungs and trachea than its parent strain 18323 or than SK18, which harbors a TnphoA fusion in the vrg-18 locus. This is the first evidence that a vir-repressed gene may play an important role in the virulence of B. pertussis and the pathogenesis of whooping cough.     

Immunogenicity and protective efficacy of a recombinant filamentous haemagglutinin from Bordetella pertussis

Bordetella pertussis is the causative agent of whooping cough, a major childhood pathogen; acellular vaccines consisting of purified B. pertussis antigens such as filamentous haemagglutinin (FHA) are commonly used to prevent pertussis. Despite the importance of FHA in B. pertussis pathogenesis and its inclusion in most acellular vaccines, the functional importance of individual domains in the induction of protective immunity is largely unknown. In this study, we have purified a recombinant FHA protein from Escherichia coli consisting of a 42 kDa maltose binding domain of E. coli and the 43 kDa type I immunodominant domain of FHA. The fusion protein (Mal85) was purified from E. coli cell lysates via affinity chromatography with an amylose column. Mal85 was then delivered to BALB/c mice intranasally encapsulated in liposomes, formulated with Protollin(TM) or in conjunction with an immunostimulatory CpG oligonucleotide. Mice were also vaccinated intraperitoneally with alum-adsorbed Mal85. Sera from all treatment groups showed strong IgG responses to Mal85 and recognized native FHA. Specific salivary IgA was induced in mice vaccinated with Mal85 in liposomes, Protollin(TM) and delivered with CpG. Vaccination with Mal85 encapsulated in liposomes or formulated with Protollin(TM) provided protection against aerosol challenge with B. pertussis in BALB/c mice. These data indicate that the type I domain of FHA is a protective antigen in mice and may serve as a candidate for inclusion in new acellular pertussis vaccines.