Enhancement of immune response against Bordetella spp. by disrupting immunomodulation

Well-adapted pathogens must evade clearance by the host immune system and the study of how they do this has revealed myriad complex strategies and mechanisms. Classical bordetellae are very closely related subspecies that are known to modulate adaptive immunity in a variety of ways, permitting them to either persist for life or repeatedly infect the same host. Exploring the hypothesis that exposure to immune cells would cause bordetellae to induce expression of important immunomodulatory mechanisms, we identified a putative regulator of an immunomodulatory pathway. The deletion of btrS in B. bronchiseptica did not affect colonization or initial growth in the respiratory tract of mice, its natural host, but did increase activation of the inflammasome pathway, and recruitment of inflammatory cells. The mutant lacking btrS recruited many more B and T cells into the lungs, where they rapidly formed highly organized and distinctive Bronchial Associated Lymphoid Tissue (BALT) not induced by any wild type Bordetella species, and a much more rapid and strong antibody response than observed with any of these species. Immunity induced by the mutant was measurably more robust in all respiratory organs, providing completely sterilizing immunity that protected against challenge infections for many months. Moreover, the mutant induced sterilizing immunity against infection with other classical bordetellae, including B. pertussis and B. parapertussis, something the current vaccines do not provide. These findings reveal profound immunomodulation by bordetellae and demonstrate that by disrupting it much more robust protective immunity can be generated, providing a pathway to greatly improve vaccines and preventive treatments against these important pathogens.

Integrated Signaling Pathways Mediate Bordetella Immunomodulation, Persistence, and Transmission

The mammalian immune system includes a sophisticated array of antimicrobial mechanisms. However, successful pathogens have developed subversive strategies to detect, modulate, and/or evade immune control and clearance. Independent disciplines study host immunology and bacterial pathogenesis, but interkingdom signaling between bacteria and host during natural infection remains poorly understood. An efficient natural host infection system has revealed complex communication between Bordetella spp. and mice, identified novel regulatory mechanisms, and demonstrated that bordetellae can respond to microenvironment and inflammatory status cues. Understanding these bacterial signaling pathways and their complex network that allows precisely timed expression of numerous immunomodulatory factors will serve as a paradigm for other organisms lacking such a powerful experimental infection system. VIDEO ABSTRACT.

Emergence of Bordetella holmesii as a Causative Agent of Whooping Cough, Barcelona, Spain

We describe the detection of Bordetella holmesii as a cause of whooping cough in Spain. Prevalence was 3.9% in 2015, doubling to 8.8% in 2016. This emergence raises concern regarding the contribution of B. holmesii to the reemergence of whooping cough and the effectiveness of the pertussis vaccine.

Lymphoid-Tissue-Resident Commensal Bacteria Promote Members of the IL-10 Cytokine Family to Establish Mutualism

Physical separation between the mammalian immune system and commensal bacteria is necessary to limit chronic inflammation. However, selective species of commensal bacteria can reside within intestinal lymphoid tissues of healthy mammals. Here, we demonstrate that lymphoid-tissue-resident commensal bacteria (LRC) colonized murine dendritic cells and modulated their cytokine production. In germ-free and antibiotic-treated mice, LRCs colonized intestinal lymphoid tissues and induced multiple members of the IL-10 cytokine family, including dendritic-cell-derived IL-10 and group 3 innate lymphoid cell (ILC3)-derived IL-22. Notably, IL-10 limited the development of pro-inflammatory Th17 cell responses, and IL-22 production enhanced LRC colonization in the steady state. Furthermore, LRC colonization protected mice from lethal intestinal damage in an IL-10-IL-10R-dependent manner. Collectively, our data reveal a unique host-commensal-bacteria dialog whereby selective subsets of commensal bacteria interact with dendritic cells to facilitate tissue-specific responses that are mutually beneficial for both the host and the microbe.

Adaptability and persistence of the emerging pathogen Bordetella petrii

The first described, environmentally isolated, Bordetella petrii was shown to undergo massive genomic rearrangements in vitro. More recently, B. petrii was isolated from clinical samples associated with jaw, ear bone, cystic fibrosis and chronic pulmonary disease. However, the in vivo consequences of B. petrii genome plasticity and its pathogenicity remain obscure. B. petrii was identified from four sequential respiratory samples and a post-mortem spleen sample of a woman presenting with bronchiectasis and cavitary lung disease associated with nontuberculous mycobacterial infection. Strains were compared genetically, phenotypically and by antibody recognition from the patient and from inoculated mice. The successive B. petrii strains exhibited differences in growth, antibiotic susceptibility and recognition by the patient’s antibodies. Antibodies from mice inoculated with these strains recapitulated the specificity and strain dependent response that was seen with the patient’s serum. Finally, we characterize one strain that was poorly recognized by the patient’s antibodies, due to a defect in the lipopolysaccharide O-antigen, and identify a mutation associated with this phenotype. We propose that B. petrii is remarkably adaptable in vivo, providing a possible connection between immune response and bacterial evasion and supporting infection persistence.

Chlamydia pneumoniae infection induced allergic airway sensitization is controlled by regulatory T-cells and plasmacytoid dendritic cells

Chlamydia pneumoniae (CP) is associated with induction and exacerbation of asthma. CP infection can induce allergic airway sensitization in mice in a dose- and time-dependent manner. Allergen exposure 5 days after a low dose (mild-moderate), but not a high dose (severe) CP infection induces antigen sensitization in mice. Innate immune signals play a critical role in controlling CP infection induced allergic airway sensitization, however these mechanisms have not been fully elucidated. Wild-type, TLR2-/-, and TLR4-/- mice were infected intranasally (i.n.) with a low dose of CP, followed by i.n. exposure to human serum albumin (HSA) and challenged with HSA 2 weeks later. Airway inflammation, immunoglobulins, eosinophils, and goblet cells were measured. Low dose CP infection induced allergic sensitization in TLR2-/- mice, but not in TLR4-/- mice, due to differential Treg responses in these genotypes. TLR2-/- mice had reduced numbers of Tregs in the lung during CP infection while TLR4-/- mice had increased numbers. High dose CP infection resulted in an increase in Tregs and pDCs in lungs, which prevented antigen sensitization in WT mice. Depletion of Tregs or pDCs resulted in allergic airway sensitization. We conclude that Tregs and pDCs are critical determinants regulating CP infection-induced allergic sensitization. Furthermore, TLR2 and TLR4 signaling during CP infection may play a regulatory role through the modulation of Tregs.

[Whooping cough from infants to adults]

Neither natural nor vaccine-induced immunity to pertussis lasts for life. Before intensive vaccination of toddlers, pertussis was essentially a pediatric disease. Mortality and morbidity have fallen drastically in parts of the world where toddlers have been systematically protected with efficacious whole-cell vaccines. The infection is now more common in adults with waning specific immunity, who can go on to infect newborns too young to be vaccinated, with potentially dramatic consequences. For these reasons, the vaccine strategy was recently modified in several countries, with the introduction of vaccine boosters for children, adolescents and young adults, as well as for healthcare workers in contact with newborns. In France, vaccine boosters were introduced for adolescents in 1998 and for adults in contact with newborns in 2004, leading to a decrease in morbidity in adolescents and very young adults. It is important to inform the medical community, and the families with neonates, of these changes in vaccine strategy. Efficient surveillance and notification systems are needed in all countries. Surveillance must include the use of standardized diagnostic tests and reagents. Bacterial isolates should be thoroughly characterized at the genomic, transcriptomic and proteomic levels.

Comparative role of immunoglobulin A in protective immunity against the Bordetellae

The genus Bordetella includes a group of closely related mammalian pathogens that cause a variety of respiratory diseases in a long list of animals (B. bronchiseptica) and whooping cough in humans (B. pertussis and B. parapertussis). While past research has examined how these pathogens are eliminated from the lower respiratory tract, the host factors that control and/or clear the bordetellae from the upper respiratory tract remain unclear. We hypothesized that immunoglobulin A (IgA), the predominant mucosal antibody isotype, would have a protective role against these mucosal pathogens. IgA(-/-) mice were indistinguishable from wild-type mice in their control and clearance of B. pertussis or B. parapertussis, suggesting that IgA is not crucial to immunity to these organisms. However, naïve and convalescent IgA(-/-) mice were defective in reducing the numbers of B. bronchiseptica in the upper respiratory tract compared to wild-type controls. Passively transferred serum from convalescent IgA(-/-) mice was not as effective as serum from convalescent wild-type mice in clearing this pathogen from the tracheae of naive recipient mice. IgA induced by B. bronchiseptica infection predominantly recognized lipopolysaccharide-containing O-antigen, and antibodies against O-antigen were important to bacterial clearance from the trachea. Since an IgA response contributes to the control of B. bronchiseptica infection of the upper respiratory tract, immunization strategies aimed at inducing B. bronchiseptica-specific IgA may be beneficial to preventing the spread of this bacterium among domestic animal populations.

Modeling systems-level regulation of host immune responses

Many pathogens are able to manipulate the signaling pathways responsible for the generation of host immune responses. Here we examine and model a respiratory infection system in which disruption of host immune functions or of bacterial factors changes the dynamics of the infection. We synthesize the network of interactions between host immune components and two closely related bacteria in the genus Bordetellae. We incorporate existing experimental information on the timing of immune regulatory events into a discrete dynamic model, and verify the model by comparing the effects of simulated disruptions to the experimental outcome of knockout mutations. Our model indicates that the infection time course of both Bordetellae can be separated into three distinct phases based on the most active immune processes. We compare and discuss the effect of the species-specific virulence factors on disrupting the immune response during their infection of naive, antibody-treated, diseased, or convalescent hosts. Our model offers predictions regarding cytokine regulation, key immune components, and clearance of secondary infections; we experimentally validate two of these predictions. This type of modeling provides new insights into the virulence, pathogenesis, and host adaptation of disease-causing microorganisms and allows systems-level analysis that is not always possible using traditional methods.

The immune response is a complex network of processes activated in a host upon infection. Pathogens seek to disrupt or evade these processes to ensure their own survival and proliferation. This article provides a systems-level analysis of the immune response against two related bacterial species in the Bordetella genus, B. bronchiseptica and B. pertussis. B. pertussis, the causative agent of whooping cough, has lost many of the virulence factors of its B. bronchiseptica–like progenitor, and is using different strategies for the modulation of the immune system. We have synthesized two separate network models for the interaction of these pathogens with their hosts. Each network is then translated into a predictive dynamic model and is validated by comparison with available experimental data. The model offers predictions regarding cytokine regulation and the effects of perturbations of the immune system, as well as the time course of infections in hosts that had previously encountered the pathogens. We experimentally validate the prediction that convalescent hosts can rapidly clear both pathogens, while antibody transfer cannot substantially reduce the duration of a B. pertussis infection. This type of modeling provides new insights into the virulence, pathogenesis, and host adaptation of disease-causing microorganisms and can be readily extended to other pathogens.

Bordetella adenylate cyclase toxin: a swift saboteur of host defense

Bordetella that infect mammals produce a multifunctional repeat in toxin (RTX) adenylate cyclase toxin known as CyaA, an excellent example of bacterial sophistication in subverting host defense. Recent reports show that interaction of CyaA with tracheal epithelial cells aids adhesion of Bordetella to ciliated mucosa and induces production of the pro-inflammatory cytokine interleukin, IL-6. Myeloid phagocytes, attracted to the site of infection are the target of freshly secreted CyaA that binds to the alpha(M)beta2 integrin (CD11b/CD18), penetrates cells and promptly suppresses their bactericidal functions by converting cellular ATP to cAMP. Such uncontrolled cAMP signaling can also drive CD11b-expressing immature dendritic cells into a semi-mature state, possibly hijacking them to shape the local adaptive immune response towards tolerance of the pathogen.

Bordetella filamentous hemagglutinin plays a critical role in immunomodulation, suggesting a mechanism for host specificity

Bordetella pertussis, the causative agent of the acute childhood respiratory disease whooping cough, is a human-adapted variant of Bordetella bronchiseptica, which displays a broad host range and typically causes chronic, asymptomatic infections. These pathogens express a similar but not identical surface-exposed and secreted protein called filamentous hemagglutinin (FHA) that has been proposed to function as both a primary adhesin and an immunomodulator. To test the hypothesis that FHA plays an important role in determining host specificity and/or the propensity to cause acute versus chronic disease, we constructed a B. bronchiseptica strain expressing FHA from B. pertussis (FHA(Bp)) and compared it with wild-type B. bronchiseptica in several natural-host infection models. FHA(Bp) was able to substitute for FHA from B. bronchiseptica (FHA(Bb)) with regard to its ability to mediate adherence to several epithelial and macrophage-like cell lines in vitro, but it was unable to substitute for FHA(Bb) in vivo. Specifically, FHA(Bb), but not FHA(Bp), allowed B. bronchiseptica to colonize the lower respiratory tracts of rats, to modulate the inflammatory response in the lungs of immunocompetent mice, resulting in decreased lung damage and increased bacterial persistence, to induce a robust anti-Bordetella antibody response in these immunocompetent mice, and to overcome innate immunity and cause a lethal infection in immunodeficient mice. These results indicate a critical role for FHA in B. bronchiseptica-mediated immunomodulation, and they suggest a role for FHA in host specificity.

Efficacies of whole cell and acellular pertussis vaccines against Bordetella parapertussis in a mouse model

Pertussis vaccine development has mainly focused on Bordetella pertussis, and consequently these vaccines contain B. pertussis antigens only. However, the related species Bordetella parapertussis can also cause pertussis, although symptoms associated with the disease are generally considered to be milder. Recent field studies have shown that in some outbreaks B. parapertussis can prevail. Using a mouse model we compared the efficacy against B. parapertussis of two commercially available acellular vaccines and two whole cell vaccines, used in The Netherlands and Finland, respectively. The efficacies of the two whole cell vaccines against B. parapertussis were similar, but much lower compared to the efficacy against B. pertussis. Although, the acellular vaccines conferred some protection against B. parapertussis early in infection, the values were not significant. Later in infection, a highly significant enhancement of colonisation by B. parapertussis was observed in mice vaccinated with acellular vaccines. The whole cell vaccines protected significantly better than the acellular vaccines against B. parapertussis. The possible consequences of a switch from whole cell to acellular vaccines was discussed in the light of our findings.

Role of antibodies in immunity to Bordetella infections

The persistence of Bordetella pertussis and B. parapertussis within vaccinated populations and the reemergence of associated disease highlight the need to better understand protective immunity. The present study examined host immunity to bordetellae and addressed potential concerns about the mouse model by using a comparative approach including the closely related mouse pathogen B. bronchiseptica. As previously observed with B. pertussis, all three organisms persisted throughout the respiratory tracts of B-cell-deficient mice, indicating that B cells are required for bacterial clearance. However, adoptively transferred antibodies rapidly cleared B. bronchiseptica but not human pathogens. These results obtained with the mouse model are consistent with human clinical observations, including the lack of correlation between antibody titers and protection, as well as the limited efficacy of intravenous immunoglobulin treatments against human disease. Together, this evidence suggests that the mouse model accurately reflects substantial differences between immunities to these organisms. Although both B. pertussis and B. parapertussis are more closely related to B. bronchiseptica than they are to each other, they share the ability to resist rapid clearance from the lower respiratory tract by adoptively transferred antibodies, an adaptation that correlates with their emergence as human pathogens that circulate within vaccinated populations.

Role of systemic and mucosal immune responses in reciprocal protection against Bordetella pertussis and Bordetella parapertussis in a murine model of respiratory infection

The roles of systemic humoral immunity, cell-mediated immunity, and mucosal immunity in reciprocal protective immunity against Bordetella pertussis and Bordetella parapertussis were examined by using a murine model of respiratory infection. Passive immunization with serum from mice infected with B. pertussis established protective immunity against B. pertussis but not against B. parapertussis. Protection against B. parapertussis was induced in mice that had been injected with serum from mice infected with B. parapertussis but not from mice infected with B. pertussis. Adoptive transfer of spleen cells from mice infected with B. pertussis or B. parapertussis also failed to confer reciprocal protection. To examine the role of mucosal immunity in reciprocal protection, mice were infected with preparations of either B. pertussis or B. parapertussis, each of which had been incubated with the bronchoalveolar wash of mice that were convalescing after infection with B. pertussis or B. parapertussis. Such incubation conferred reciprocal protection against B. pertussis and B. parapertussis on infected mice. The data suggest that mucosal immunity including secreted immunoglobulin A in the lungs might play an important role in reciprocal protective immunity in this murine model of respiratory infection.

Role of Bordetella O antigen in respiratory tract infection

Lipopolysaccharide (LPS), as the major surface molecule of gram-negative bacteria, interacts with the host in complex ways, both inducing and protecting against aspects of inflammatory and adaptive immunity. The membrane-distal repeated carbohydrate structure of LPS, the O antigen, can prevent antibody functions and may vary as a mechanism of immune evasion. Genes of the wbm locus are required for the assembly of O antigen on the animal pathogen Bordetella bronchiseptica and the human pathogen B. parapertussis. However, the important human pathogen B. pertussis lacks these genes and a number of in vitro and in vivo characteristics associated with O antigen in other organisms. To determine the specific functions of O antigen in these closely related Bordetella subspecies, we compared wbm deletion (Deltawbm) mutants of B. bronchiseptica and B. parapertussis in a variety of assays relevant to natural respiratory tract infection. Complement was not activated or depleted by wild-type bordetellae expressing O antigen, but both Deltawbm mutants activated complement and were highly sensitive to complement-mediated killing in vitro. Although the O-antigen structures appear to be substantially similar, the two mutants differed strikingly in their defects within the respiratory tract. The B. parapertussis Deltawbm mutant was severely defective in colonization of the tracheas and lungs of mice, while the B. bronchiseptica Deltawbm mutant showed almost no defect. While in vitro characteristics such as serum resistance may be attributable to O antigen directly, the role of O antigen during infection appears to be more complex, possibly involving factors differing among the closely related bordetellae or different interactions between each one and its host.

Comparative phenotypic analysis of the Bordetella parapertussis isolate chosen for genomic sequencing

The genomes of three closely related bordetellae are currently being sequenced, thus providing an opportunity for comparative genomic approaches driven by an understanding of the comparative biology of these three bacteria. Although the other strains being sequenced are well studied, the strain of Bordetella parapertussis chosen for sequencing is a recent human clinical isolate (strain 12822) that has yet to be characterized in detail. This investigation reports the first phenotypic characterization of this strain, which will likely become the prototype for this species in comparison with the prototype strains of B. pertussis (Tohama I), B. bronchiseptica (RB50), and other isolates of B. parapertussis. Multiple in vitro and in vivo assays distinguished each species. B. parapertussis was more similar to B. bronchiseptica than to B. pertussis in many assays, including in BvgS signaling characteristics, presence of urease activity, regulation of urease expression by BvgAS, virulence in the respiratory tracts of immunocompromised mice, induction of anti-Bordetella antibodies, and serum antimicrobial resistance. In other assays, B. parapertussis was distinct from all other species (in pigment production) or more similar to B. pertussis (by lack of motility and cytotoxicity to a macrophage-like cell line). These results begin to provide phenotypes that can be related to genetic differences identified in the genomic sequences of bordetellae.

Reciprocal protective immunity against Bordetella pertussis and Bordetella parapertussis in a murine model of respiratory infection

The protective immunity induced by infection with Bordetella pertussis and with Bordetella parapertussis was examined in a murine model of respiratory infection. Convalescent mice that had been infected by aerosol with B. pertussis or with B. parapertussis exhibited a protective immune response against B. pertussis and also against B. parapertussis. Anti-filamentous hemagglutinin (anti-FHA) serum immunoglobulin G (IgG) and anti-FHA lung IgA antibodies were detected in both mice infected with B. pertussis and those infected with B. parapertussis. Antibodies against pertussis toxin (anti-PT) and against killed B. pertussis cells were detected in mice infected with B. pertussis. Pertactin-specific antibodies and antibodies against killed B. parapertussis cells were detected in mice infected with B. parapertussis. Spleen cells from mice infected with B. pertussis secreted interferon-gamma (IFN-gamma) in response to stimulation by FHA or PT. Spleen cells from mice infected with B. parapertussis also secreted IFN-gamma in response to FHA. Interleukin-4 was not produced in response to any of the antigens tested. The profiles of cytokine secretion in vitro revealed induction of a Th1-biased immune response during convalescence from infection by B. pertussis and by B. parapertussis. It is possible that Th1 and Th2 responses against FHA might be related to the reciprocal protection achieved in our murine model.

Structural variability and originality of the Bordetella endotoxins

Structural studies of Bordetella endotoxins (LPSs) have revealed remarkable differences: (i) between their LPSs and those of other bacterial pathogens; (ii) among the LPSs of the seven identified Bordetella species; and (iii) among the LPSs of some Bordetella strains. The lipid As have the "classical" bisphosphorylated diglucosamine backbone but tend to have fewer and species-specific fatty acid components compared to those of other genera. Nevertheless, three strains of B. bronchiseptica have at least three different fatty acid distributions; however, the recently identified B. hinzii and B. trematum LPSs had identical lipid A structures. The B. pertussis core is a dodecasaccharide multi-branched structure bearing amino and carboxylic groups. Another unusual feature is the presence of free amino sugars in the central core region and a complex distal trisaccharide unit containing five amino groups of which four are acetylated and one is methylated. The B. pertussis LPS does not have O-chains and that of B. trematum had only a single O-unit, unlike the LPSs of all the other species of the smooth-type. The O-chain-free cores of non-B. pertussis LPSs were always built on the B. pertussis core model but most were species-specifically incomplete. The LPS structures of three B. bronchiseptica strains were found to be different from each other. The O-chains of B. bronchiseptica and B. parapertussis were almost identical and had some features in common with B. hinzii O-chain. Serological analyses are consistent with the determined LPS structures.

Serum immunoglobulin G antibody responses to Bordetella pertussis lipooligosaccharide and B. parapertussis lipopolysaccharide in children with pertussis and parapertussis

Serum immunoglobulin G (IgG) antibodies against the lipooligosaccharide (LOS) of Bordetella pertussis and the lipopolysaccharide (LPS) of Bordetella parapertussis were measured by enzyme-linked immunosorbent assay in paired sera from 40 children with pertussis and 14 with parapertussis. Wide differences in the individual responses were noted. Both anti-LOS and -LPS IgG levels increased significantly in the children with pertussis, as did anti-LPS but not anti-LOS in those with parapertussis.

Use of pertussis toxin encoded by ptx genes from Bordetella bronchiseptica to model the effects of antigenic drift of pertussis toxin on antibody neutralization

Recently, concern has been voiced about the potential effect that antigenic divergence of circulating strains of Bordetella pertussis might have on the efficacy of pertussis vaccines. In order to model antigenic drift of pertussis toxin, a critical component of many pertussis vaccines, and to examine the effects of such drift on antibody neutralization, we engineered a strain of B. pertussis to produce a variant pertussis toxin molecule that contains many of the amino acid changes found in the toxin encoded by Bordetella bronchiseptica ptx genes. This altered form of the toxin, which is efficiently secreted by B. pertussis and which displays significant biological activity, was found to be neutralized by antibodies induced by vaccination as readily as toxin produced by wild-type B. pertussis. These findings suggest that significant amino acid changes in the pertussis toxin sequence can occur without drastically altering the ability of antibodies to recognize and neutralize the toxin molecule.

Use of monoclonal fluorescent antibodies for the detection of B. pertussis and B. parapertussis

While it has been said that PCR is likely to replace DFA as the test of choice, accessibility to and cost of the technique may limit the number of laboratories that are able to implement the process. Still, the advantage of DFA staining relative to other diagnostic methods, including PCR, is the provision of a rapid result and lower overall cost. The laboratory diagnosis of pertussis remains problematic, and polyclonal DFA reagents for its detection have brought into question the utility of DFA. However, the integration of a commercially available monoclonal DFA reagent, in combination with the development and standardization of existing procedures, should provide clinicians with an improved method for the diagnosis and epidemiology of pertussis.

Parapertussis and pertussis: differences and similarities in incidence, clinical course, and antibody responses

OBJECTIVES

To compare the incidence, clinical course, and serologic response to Bordetella antigens in patients with parapertussis and pertussis.

DESIGN

Two studies were performed in Sweden during the 1990s, when pertussis vaccines were used only in clinical trials. Study I was a retrospective study of patients with positive Bordetella cultures obtained in clinical routine, and study II involved an active search for patients with Bordetella infections during a placebo-controlled trial of a pertussis toxoid vaccine.

RESULTS

Study I includes 58, and study II 23 patients with parapertussis. In study I, the incidence of parapertussis was 0.016 cases per 100 person years in children 0 to 6 years old and 0 in older children and adults. In study II, the incidence rates of parapertussis and pertussis were 0.2 and 16.2 per 100 person years, respectively, in children followed from 3 months to 3 years of age. The median number of days with cough was 21 in parapertussis and 59 in pertussis. The proportions of children with whooping and vomiting were lower in parapertussis than in pertussis. Geometric mean serum filamentous hemagglutinin IgG increased from 6 to 63, and pertactin IgG from 4 to 12 units/mL in parapertussis patients, which was similar to increases in children with pertussis.

CONCLUSIONS

Disease caused by Bordetella parapertussis is diagnosed less commonly and is milder and of shorter duration than disease caused by Bordetella pertussis. Parapertussis induced serum IgG against filamentous hemagglutinin and pertactin of similar magnitude as does pertussis, and did not induce serum IgG against pertussis toxin.

Genetic basis for lipopolysaccharide O-antigen biosynthesis in bordetellae

Bordetella bronchiseptica and Bordetella parapertussis express a surface polysaccharide, attached to a lipopolysaccharide, which has been called O antigen. This structure is absent from Bordetella pertussis. We report the identification of a large genetic locus in B. bronchiseptica and B. parapertussis that is required for O-antigen biosynthesis. The locus is replaced by an insertion sequence in B. pertussis, explaining the lack of O-antigen biosynthesis in this species. The DNA sequence of the B. bronchiseptica locus has been determined and the presence of 21 open reading frames has been revealed. We have ascribed putative functions to many of these open reading frames based on database searches. Mutations in the locus in B. bronchiseptica and B. parapertussis prevent O-antigen biosynthesis and provide tools for the study of the role of O antigen in infections caused by these bacteria.

Bacterin-induced protection of turkeys against fowl cholera following infection with Bordetella avium

Groups of Beltsville small white turkeys, passively immunized and not passively immunized against Bordetella avium, were challenged with live B. avium at 2 days of age. Birds not passively immunized developed severe bordetellosis with early onset, whereas passively immunized birds developed mild bordetellosis with late onset. Following convalescence, birds with and without exposure to B. avium were vaccinated against fowl cholera with a water-in-oil bacterin. The birds were given a homologous challenge with serotype A: 3 Pasteurella multocida. Although no difference in protection against fowl cholera was seen between vaccinated birds that were previously infected with B. avium and those that were not, survivability was better in birds given two doses rather than 1 dose of bacterin.

The efficacy of a whole cell pertussis vaccine and fimbriae against Bordetella pertussis and Bordetella parapertussis infections in a respiratory mouse model

Due to local and systemic side-effects, the currently used, highly effective, whole-cell pertussis vaccines (WCVs) will be replaced by acellular vaccines (ACVs) in some countries. These ACVs contain detoxified pertussis toxin, either alone or in combination with the filamentous haemagglutinin, pertactin and fimbriae. Ongoing clinical trials show that ACVs are clearly less reactogenic than WCVs and that ACVs comprised of three to five proteins are highly efficacious in inducing protection against Bordetella pertussis infections. An important unresolved question is, what the effect will be of the switch from WCVs to ACVs on the incidence of Bordetella parapertussis infections, the second causative agent of pertussis. A comparison of the efficacy of WCVs and ACVs against B. parapertussis infection is required to answer this question. We show that the Dutch WCV, although prepared from B. pertussis strains, protects against B. parapertussis infection in a murine respiratory model, although less efficiently than against B. pertussis infection. It was shown previously that the ACV components pertussis toxin, FHA and pertactin did not protect against B. parapertussis infection in a murine respiratory model. We have investigated the efficacy of two other ACV components, B. pertussis serotype-2 and -3 fimbriae against B. parapertussis infection in the murine model. The B. pertussis fimbriae protected mice against B. parapertussis infection although less efficiently than against B. pertussis infection. This result indicates that B. pertussis and B. parapertussis fimbriae are antigenically distinct. B. pertussis fimbriae were found to be as efficacious as the WCV against B. pertussis infection. Our results are discussed in the light of the switch from WCVs to ACVs.

Passive immune protection of turkeys against Coryza

Antisera made against whole cells of Bordetella avium protected turkeys against disease signs of turkey coryza, but antiserum against the dermonecrotic heat-labile toxin (DHLT) did not. Neither antiserum against whole cells nor antiserum against DHLT protected turkeys against colonization of the trachea by B. avium. At least 25 bands in whole cell lysate of B. avium separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) reacted in immunoblots with protective antiserum. These bands occurred at < 40 kDa and > 105.3 kDa. DHLT had an isoelectric point (pI) in the range pH 6.3-6.7. Following SDS-PAGE of isoelectric-focused fractions, two bands were recognized by anti-DHLT with immunoblots of pI 6.3, pI 6.5, and pI 6.7 fractions separated by SDS-PAGE.

[A new Bordetella species in sheep?]

Occasionally the occurrence of isolates of the genus Bordetella has been reported, with unclear assignment to one of the known species in sheep from New Zealand and Great Britain. In this study we describe the isolation of strains belonging to the genus Bordetella in a flock of sheep from Germany. These isolates were characterized biochemically by serological tests and whole cell fatty acid analysis. Our isolates could be divided into three subgroups by their differential growth on MacConcey- and Tyrosine agar. A clear assignment to one of the known Bordetella species was not possible.

Effect of Bordetella bronchiseptica and serotype D Pasteurella multocida bacterin-toxoid on the occurrence of atrophic rhinitis after experimental infection with B. bronchiseptica and toxigenic type AP. multocida

In efficacy tests, 7 primary specific-pathogen-free piglets vaccinated with the Bordetella bronchiseptica and type D Pasteurella multocida bacterin-toxoid were challenged with B. bronchiseptica and type A P. multocida. Severe or moderate nasal turbinate atrophy was produced in the non-vaccinated pigs, whereas, only one of the 4 pigs in the vaccinated group had slight turbinate atrophy. Other immune sera against crude toxin of P. multocida type A or D were cross neutralized. The results of the present study show that the P. multocida serotype D bacterin-toxoid is effective against atrophic rhinitis caused by toxigenic P. multocida serotype A as well as toxigenic P. multocida serotype D.

A clinical validation of Bordetella pertussis and Bordetella parapertussis polymerase chain reaction: comparison with culture and serology using samples from patients with suspected whooping cough from a highly immunized population

The aim of this study was to validate the performance of the polymerase chain reaction (PCR) assay for Bordetella pertussis and Bordetella parapertussis in comparison with both culture and serology. The number of samples positive in PCR was 2.4-fold higher than the number of samples positive in culture. In serologically confirmed cases, the sensitivity of PCR and culture depended on the duration of disease and the age of the patient, being less sensitive in older age and later in disease. The sensitivity of the PCR in patients with < 10 days of symptoms was 70%, 50%, and 10% in the age groups < 1 year, 1-4 years, and > or = 5 years, respectively. Evidence suggested that the effect of age on sensitivity may be due to differences in immune responses. The low IgA response in the < 1 year age group may be related to the high number of samples positive in PCR and culture, even late in disease.

Immunomagnetic separation and solid-phase detection of Bordetella pertussis

In the present study, novel solid-phase methods were used for both sample preparation and PCR detection of Bordetella pertussis. The sample preparation was performed by immunomagnetic separation with paramagnetic beads coated with polyclonal antibodies directed toward the surface antigens of the bacteria. The precoated immunobeads were directly used on nasopharyngeal aspirates to capture the bacteria on the solid support and were subsequently transferred to the PCR tube with no further manipulations. The region encompassing the pertussis toxin promoter was analyzed to allow direct discrimination between the three major Bordetella species (B. pertussis, B. parapertussis, and B. bronchiseptica). The resulting amplicons were captured on a second magnetic solid phase, allowing detection and restriction analysis of the target sequence. A colorimetric detection system based on a DNA binding fusion protein enabled the use of standardized enzyme-linked immunosorbent format tests both for the detection of Bordetella spp. and for species evaluation. When the optimized system was evaluated on 55 clinical aspirate samples, 21 of 22 (95%) culture-positive samples were positive by the system that we developed. In addition, two samples were positive by the PCR-based assay, while the culture assay was negative. The implications of these results are discussed.

Epitopes of Bordetella pertussis lipopolysaccharides as potential markers for typing of isolates with monoclonal antibodies

Three hybridomas (P1P3, D7 and 60.5) producing monoclonal antibodies (mAbs) against Bordetella pertussis lipopolysaccharide (LPS) were established. All reacted with the LPS from a typical, vaccine strain of B. pertussis (1414), but not with that of a variant strain (A100). Two of these mAbs (P1P3 and 60.5) cross-reacted with a B. bronchiseptica LPS; only one (P1P3) reacted with a B. parapertussis LPS. ELISA reactivities with intact LPSs, and defined partial structures covalently linked to bovine serum albumin, were compared. mAb 60.5 bound to the terminal region of a distal trisaccharide consisting of N-acetylated amino sugars. D7 reacted with a substructure which can be modified in the B. parapertussis and B. bronchiseptica LPSs by addition of a polymeric O-chain. P1P3 bound to a nonacetylated glucosamine substituted with L-glycero-D-manno-heptose, present in the 'core' of the B. pertussis LPS. These mAbs may be useful for rapid typing of Bordetella in clinical isolates.

Polymerase chain reaction for the identification of Bordetella pertussis and Bordetella parapertussis

The polymerase chain reaction (PCR) for the detection of Bordetella pertussis and Bordetella parapertussis DNA in clinical samples was well documented by recent studies. Different regions in Bordetella pertussis DNA have been successfully used as targets for this method by various authors. In this work we report the usefulness of the PCR assay also for speciating Bordetellae isolates in those cases where the biochemical and serological tests gave inconclusive results.

Characterisation of ovine Bordetella parapertussis isolates by analysis of specific endotoxin (lipopolysaccharide) epitopes, filamentous haemagglutinin production, cellular fatty acid composition and antibiotic sensitivity

Isolates of Bordetella parapertussis, recovered from sheep or man, were characterised by reaction with specific anti-Bordetella lipopolysaccharide monoclonal antibodies, production of filamentous haemagglutinin, fatty acid patterns, and antibiotic sensitivity. Generally, the isolates lay within one of four groups, with separation of the ovine isolates into two groups. Reactions with specific monoclonal antibodies against lipopolysaccharide separated the ovine isolates into these two groupings. Analysis of the cellular fatty acid compositions by cluster analysis differentiated between the human and the ovine strains and also showed variation within the ovine isolates. When the production of filamentous haemagglutinin was analysed in an ELISA system, a similar pattern emerged. Varying concentrations of filamentous haemagglutinin (11-429 ng (mg total protein)-1) were extracted from the human isolates and the one group of ovine isolates with no significant protein detected in the other ovine group. These studies demonstrate variation between and within B. parapertussis isolates recovered from two mammalian sources.

[Infection with species of the genus Bordetella in adults, a factor in maintaining morbidity for whooping cough. Serological studies]

A number of 1021 serological investigations were performed to identify agglutinating antibodies against B. pertussis and B. parapertussis in adults. The investigations were initiated to study the presence of agglutinins in serum, in response to a previous infection with Bordetella species. The serological tests revealed the presence of agglutinating antibodies at titres considered to be positive (> or = 1/320) in 136 (13.3%) sera. The results obtained suggest that pertussis is relatively frequent in adults, and must be considered as a factor of maintaining morbidity.

A time-course study of the transfer of immunoglobulin G from blood to tracheal and lacrimal secretions in young turkeys

Three-week-old turkeys were injected intravenously with Bordetella avium-specific immunoglobulin G (IgG), and absorbance readings were measured in blood, tracheal washings, and lacrimal secretions using an enzyme-linked immunosorbent assay at various time intervals. IgG was detected in tracheal and lacrimal secretions as early as 5 minutes after injection and peaked at 10 minutes after injection. Thereafter, IgG absorbance declined rapidly, reaching background levels by 24 hours. The absorbance readings of IgG in all three sites were comparable at all times from 10 minutes to 24 hours after administration. The results indicated that movement of IgG from blood to mucosal surfaces in turkeys occurs rapidly.

Biological and protective activities of outer membrane proteins from Bordetella

In this work the biological properties and the capability of the outer membrane proteins (OMPs) from different strains of Bordetella to induce protection against challenge with B. pertussis 18323 were examined. The OMPs from each strain were isolated using Schnaitmann's method. Two OMPs (30 and 32 kDa) were found to be specific for the vaccine strains of B. pertussis and were absent in the OMPs preparation from both B. parapertussis and B. bronchiseptica. When the OMPs from the vaccine strains of B. pertussis were assayed in the mouse intracerebral protection test, they were found to be highly protective (75%-88%) against a challenge with 250 50% lethal doses (LD50) of B. pertussis 18323. However, no correlation was observed between the protective activity and the lymphocytosis-promoting factor (LPF) content of different preparations. Moreover, neither LPF activity or histamine-sensitizing activity (HSA) were found in any of the OMPs assayed. Our results show that OMPs from B. pertussis vaccine strains play a key role in the induction of protective immunity against B. pertussis 18323 in mice, making them excellent candidates to be used in further studies for the development of a pertussis vaccine for humans.

Specific and cross-reacting monoclonal antibodies to Bordetella parapertussis and Bordetella bronchiseptica lipopolysaccharides

Three groups of monoclonal antibodies (mAbs) were produced that would be useful for immunochemical typing and diagnosis of infections due to Bordetella species, and for the structural analysis of their lipopolysaccharides. PP6, a representative of the first group, recognizes an epitope shared by smooth-type Bordetella parapertussis and Bordetella bronchiseptica lipopolysaccharides (LPS). This epitope is carried by structurally identical polymeric O-chains (POC) present on both LPS molecules. PP8 and PP9 are representatives of the second group of mAbs. The interaction of PP8 and PP9 with B. parapertussis and B. bronchiseptica LPS requires POC, but periodate-sensitive sugar units of the core are also involved in the binding. The mAb BRg1 belongs to the third group, and specifically recognizes B. bronchiseptica LPS. Binding and inhibition studies with various Bordetella LPS molecules, and with their polysaccharide fragments, indicated that BRg1 interacts with a structure located at the hinge between the POC and a core region of the B. bronchiseptica LPS containing periodate-resistant sugars. This suggests that the structures of the hinge regions of the B. parapertussis and B. bronchiseptica LPS are different.

Production of monoclonal antibodies to the Bordetella avium 41-kilodalton surface protein and characterization of the hemagglutinin

Production of monoclonal antibodies (MAbs) to Bordetella avium surface proteins led to further characterization of the hemagglutinin. Proteins obtained by homogenization of whole-cell B. avium were used to immunize mice for the production of monoclonal antibodies. Immunoprecipitation and Western blot techniques were used to determine the specificity of three MAbs, which all recognized the B. avium 41-kilodalton (kd) surface protein. In addition, all of the MAbs inhibited hemagglutination (HA) of guinea pig erythrocytes by B. avium. The 41-kd protein recognized by the MAbs was observed by the indirect immunofluorescence test and sodium dodecyl sulfate-polyacrylamide gel electrophoresis to bind to guinea pig erythrocytes. When HA-positive isolates of B. avium were treated with periodic acid, which cleaves carbohydrates from proteins, the isolates became HA-negative. Likewise, treatment of HA-positive B. avium isolates with proteinase K, which would also remove carbohydrates associated with proteins on the surface of the bacterium, inhibited HA. Considering these data, we suggest that the B. avium hemagglutinin is a carbohydrate closely associated with the 41-kd surface protein.

Mucosal and systemic humoral immune response to Bordetella avium in experimentally infected turkeys

Antibody response to Bordetella avium was measured in serum and mucosal secretions of experimentally infected turkeys. Two-day-old turkeys were inoculated with B. avium, and four inoculated turkeys and four uninoculated control birds per trial were euthanatized weekly from 1 through 8 weeks postinoculation (PI). Maternal antibody of the IgG isotype, present in all 2-day-old birds sampled, decreased to background levels by 3 weeks of age. Antibody (IgG, IgM, IgA) was detected in serum, tracheal washings, and lacrimal secretions in response to B. avium infection. Regardless of the sample site and isotype, antibody levels peaked at 4-6 weeks PI and then decreased rapidly from 6 to 8 weeks PI. In general, IgM and IgA levels peaked earlier (4-5 weeks PI) but declined more rapidly than IgG levels. Numbers of B. avium in the trachea peaked at 2-3 weeks PI and then decreased rapidly from 4 to 8 weeks PI. Even though no direct causal relationship could be determined, the results indicate that an increasing level of antibody in serum, tracheal washings, and lacrimal secretions is temporally associated with clearance of B. avium from the trachea.

Increase of the bursal follicular medullary compartment in chicks intracloacally inoculated with Bordetella pertussis

The cloacal bursa is a primary lymphoid organ responsible for the maturation of B-lymphocytes. It has been suggested that the bursa may also play a peripheral role when antigens are inoculated by cloacal route. Qualitative and quantitative structural modifications in the bursa from chicks inoculated with Bordetella pertussis by the cloacal route were investigated. Observations indicated that the relative bursal growth as well as the volume fraction and the mitotic index of the follicular medulla from experimental bursae are significantly greater than those of the controls. Macrophages which have phagocytized bacteria, and a gradual relative increase of the RER of lymphoblasts, were other structural modifications found exclusively in the follicular medulla. The observations suggest that the bursal follicular cortex and medulla act as autonomous histophysiological compartments, the latter being responsible for an antigenic stimulation when Bordetella pertussis is intracloacally inoculated in chicks.

A monoclonal antibody-based latex bead agglutination test for the detection of Bordetella avium

The purpose of this study was to develop a rapid method to distinguish Bordetella avium from closely related Bordetella avium-like and B. bronchiseptica bacteria. A monoclonal antibody of the IgM isotype was produced in Balb/c mice against live B. avium strain 75. The monoclonal antibody, in the form of ascites fluid, was added to a bovine serum albumin-glycine buffer (pH 8.6) and adsorbed to 3.03-microns-diameter latex beads. Optimum concentrations of antibody, beads, and bacteria were determined. The latex bead conjugate was tested against 40 isolates of B. avium, 24 isolates of B. avium-like bacteria, 17 isolates of B. bronchiseptica, two isolates of Alcaligenes faecalis, and several other common genera. Strong agglutination occurred with all B. avium isolates and the two isolates of A. faecalis. Weak agglutination occurred with Staphylococcus aureus and two isolates of B. bronchiseptica. There was no agglutination with any of the B. avium-like isolates. The latex bead agglutination test may be useful as an aid in the identification of B. avium when used in conjunction with other criteria.