Comparative structural and immunological analysis of outer membrane proteins and dermonecrotic toxin in Bordetella bronchiseptica canine isolate

Bordetella bronchiseptica is a pathogen causing respiratory infections in mammals. With the improving understanding of companion animals' welfare, addressing the side effects of bordetella vaccine gains importance in dogs. Studies on diverse subunit vaccines are actively pursued in humans to safely and effectively control bordetellosis. Therefore, our objective was to develop a canine bordetella vaccine inspired by human vaccine development. We evaluated the immunogenicity of the two bacterial components: the outer membrane proteins (OMPs) and the dermonecrotic toxin (DNT) from a canine isolate of B. bronchiseptica. In-silico analysis identified eight domains of DNT, and Domain 3 was selected as the most promising antigen candidate. Additionally, the OMPs were extracted and examined using SDS-PAGE and Western blot analysis. The distinct immunological characteristic of OMPs and DNT-3 were examined individually and in combination. Gene expression and cytokine production were also evaluated in DH82 cells after stimulation with those antigens. Treatment with OMPs resulted in higher level of Th1 related cytokines, while DNT-3 induced a predominant response associated with Th17 and Th2 in the cytokine production. Synergistic effects were observed exclusively on IL-23, indicating increase of a potential risk of side effects when OMPs and DNT act together. These findings provide valuable insights into the reactogenicity of conventional Bordetella vaccines. Further, the presented preclinical data in this study offer an alternative method of the development for an optimal next-generation Bordetella vaccine for companion animals and humans, replacing the acellular vaccines containing both toxin and protein components.

Method for quantifying the Pasteurella multocida antigen adsorbed on aluminum hydroxide adjuvant in swine atrophic rhinitis vaccine

Swine atrophic rhinitis is a disease caused by Pasteurella multocida and Bordetella bronchiseptica that affects pigs. Inactivated vaccines containing the toxins produced by Pasteurella multocida and Bordetella bronchiseptica have been widely used for the prevention of swine atrophic rhinitis. The efficacy of a vaccine is correlated with the amount of antigen present; however, the protective toxin of P. multocida bound to aluminum hydroxide, which is used as an adjuvant, can hinder the monitoring of the antigen concentration in the vaccine. This study assessed the applicability of a dot immunoassay as an antigen quantification method using monoclonal antibodies. This quantification method was able to detect the antigen with high specificity and sensitivity even when the antigen was bound to the adjuvant, and its application to vaccine products revealed a correlation between the amount of antigen present in the vaccine and the neutralizing antibody titers induced in pigs. The antigen quantification method presented in this study is a simple and sensitive assay capable of quantifying the amount of antigen present in a vaccine that can be used as an alternative quality control measure.

Eosinophils and Bacteria, the Beginning of a Story

Eosinophils are granulocytes primarily associated with TH2 responses to parasites or immune hyper-reactive states, such as asthma, allergies, or eosinophilic esophagitis. However, it does not make sense from an evolutionary standpoint to maintain a cell type that is only specific for parasitic infections and that otherwise is somehow harmful to the host. In recent years, there has been a shift in the perception of these cells. Eosinophils have recently been recognized as regulators of immune homeostasis and suppressors of over-reactive pro-inflammatory responses by secreting specific molecules that dampen the immune response. Their role during parasitic infections has been well investigated, and their versatility during immune responses to helminths includes antigen presentation as well as modulation of T cell responses. Although it is known that eosinophils can present antigens during viral infections, there are still many mechanistic aspects of the involvement of eosinophils during viral infections that remain to be elucidated. However, are eosinophils able to respond to bacterial infections? Recent literature indicates that Helicobacter pylori triggers TH2 responses mediated by eosinophils; this promotes anti-inflammatory responses that might be involved in the long-term persistent infection caused by this pathogen. Apparently and on the contrary, in the respiratory tract, eosinophils promote TH17 pro-inflammatory responses during Bordetella bronchiseptica infection, and they are, in fact, critical for early clearance of bacteria from the respiratory tract. However, eosinophils are also intertwined with microbiota, and up to now, it is not clear if microbiota regulates eosinophils or vice versa, or how this connection influences immune responses. In this review, we highlight the current knowledge of eosinophils as regulators of pro and anti-inflammatory responses in the context of both infection and naïve conditions. We propose questions and future directions that might open novel research avenues in the future.

Respiratory Bordetella bronchiseptica Carriage is Associated with Broad Phenotypic Alterations of Peripheral CD4⁺CD25⁺ T Cells and Differentially Affects Immune Responses to Secondary Non-Infectious and Infectious Stimuli in Mice

The respiratory tract is constantly exposed to the environment and displays a favorable niche for colonizing microorganisms. However, the effects of respiratory bacterial carriage on the immune system and its implications for secondary responses remain largely unclear. We have employed respiratory carriage with Bordetella bronchiseptica as the underlying model to comprehensively address effects on subsequent immune responses. Carriage was associated with the stimulation of Bordetella-specific CD4⁺, CD8⁺, and CD4⁺CD25⁺Foxp3⁺ T cell responses, and broad transcriptional activation was observed in CD4⁺CD25⁺ T cells. Importantly, transfer of leukocytes from carriers to acutely B. bronchiseptica infected mice, resulted in a significantly increased bacterial burden in the recipient's upper respiratory tract. In contrast, we found that respiratory B. bronchiseptica carriage resulted in a significant benefit for the host in systemic infection with Listeria monocytogenes. Adaptive responses to vaccination and influenza A virus infection, were unaffected by B. bronchiseptica carriage. These data showed that there were significant immune modulatory processes triggered by B. bronchiseptica carriage, that differentially affect subsequent immune responses. Therefore, our results demonstrated the complexity of immune regulation induced by respiratory bacterial carriage, which can be beneficial or detrimental to the host, depending on the pathogen and the considered compartment.

Comparative efficacy of intranasal and injectable vaccines in stimulating Bordetella bronchiseptica-reactive anamnestic antibody responses in household dogs

In order to determine the comparative efficacy of injectable and intranasal vaccines to stimulate Bordetella bronchiseptica (Bb)-reactive anamnestic antibodies, a trial was conducted using 144 adult household dogs of various breeds and ages, which had been previously administered intranasal Bb vaccine approximately 12 months before enrollment. Dogs were randomized into 2 groups and blood, nasal swabs, and pharyngeal swabs were collected prior to the administration of single component Bb vaccines intranasally or parenterally. Ten to 14 days later all dogs were resampled to measure changes in systemic and local antibody to Bb. There were no differences in the changes in Bb-reactive serum IgG and nasal IgA between the groups, whereas intranasally vaccinated dogs had significantly higher Bb-reactive serum IgA. These data indicate that both of the current generation of intranasal (modified-live) and injectable (acellular) Bb vaccines can stimulate anamnestic local and systemic antibody responses in previously vaccinated, Bb-seropositive adult household dogs.

Comparative efficacy of intranasal and oral vaccines against Bordetella bronchiseptica in dogs

In order to determine the comparative efficacy of vaccines administered intranasally or orally to protect puppies from disease subsequent to experimental infection with Bordetella bronchiseptica (Bb), a randomized controlled trial was performed using 48 approximately 8-week-old specific pathogen free, Bb naive Beagle puppies. Puppies were randomized into three groups and administered vaccines containing Bb intranasally or orally, or a placebo intranasally. Twenty-one days later, all dogs were challenge exposed via aerosol administration of Bb. Clinical signs, nasal bacterial shedding and immune responses were monitored for 28 days after challenge. Intranasally vaccinated puppies had significantly lower rates of coughing, nasal discharge, retching and sneezing (i.e. were less sick clinically) than control puppies. The distinction between the orally vaccinated puppies and the control puppies was less consistent. The orally vaccinated puppies had less coughing and less retching than the control puppies, but nasal discharge and sneezing did not differ from control animals. Orally vaccinated puppies had higher rates of coughing, nasal discharge, retching and sneezing than the intranasally vaccinated puppies. Although both intranasal and oral Bb vaccines stimulated immune responses associated with disease sparing following Bb infection, the intranasal route of delivery conferred superior clinical outcomes. The observed difference in clinical efficacy suggests the need to question the rationale for the use of currently available orally administered Bb vaccines.

Immunological and protective effects of Bordetella bronchiseptica subunit vaccines based on the recombinant N-terminal domain of dermonecrotic toxin

Dermonecrotic toxin (DNT) produced by Bordetella bronchiseptica (B. bronchiseptica) can cause clinical turbinate atrophy in swine and induce dermonecrotic lesions in model mice. We know that the N-terminal of DNT molecule contains the receptor-binding domain, which facilitates binding to the target cells. However, we do not know whether this domain has sufficient immunogenicity to resist B. bronchiseptica damage and thereby to develop a subunit vaccine for the swine industry. In this study, we prokaryotically expressed the recombinant N-terminal of DNT from B. bronchiseptica (named DNT-N) and prepared it for the subunit vaccine to evaluate its immunogenicity. Taishan Pinus massoniana pollen polysaccharide (TPPPS), a known immunomodulator, was used as the adjuvant to examine its immune-conditioning effects. At 49 d after inoculation, 10 mice from each group were challenged with B. bronchiseptica, and another 10 mice were intradermally challenged with native DNT, to examine the protection imparted by the vaccines. The immune parameters (T-lymphocyte counts, cytokine secretions, serum antibody titers, and survival rates) and skin lesions were determined. The results showed that pure DNT-N vaccine significantly induced immune responses and had limited ability to resist the B. bronchiseptica and DNT challenge, whereas the mice administered with TPPPS or Freund's incomplete adjuvant vaccine could induce higher levels of the above immune parameters. Remarkably, the DNT-N vaccine combined with TPPPS adjuvant protected the mice effectively to prevent B. bronchiseptica infection. Our findings indicated that DNT-N has potential for development as an effective subunit vaccine to counteract the damage of B. bronchiseptica infection, especially when used conjointly with TPPPS.

Host Specificity of Ovine Bordetella parapertussis and the Role of Complement

The classical bordetellae are comprised of three subspecies that differ from broad to very limited host specificity. Although several lineages appear to have specialized to particular host species, most retain the ability to colonize and grow in mice, providing a powerful common experimental model to study their differences. One of the subspecies, Bordetella parapertussis, is composed of two distinct clades that have specialized to different hosts: one to humans (Bpp_hu), and the other to sheep (Bpp_ov). While Bpp_hu and the other classical bordetellae can efficiently colonize mice, Bpp_ov strains are severely defective in their ability to colonize the murine respiratory tract. Bpp_ov genomic analysis did not reveal the loss of adherence genes, but substantial mutations and deletions of multiple genes involved in the production of O-antigen, which is required to prevent complement deposition on B. bronchiseptica and Bpp_hu strains. Bpp_ov lacks O-antigen and, like O-antigen mutants of other bordetellae, is highly sensitive to murine complement-mediated killing in vitro. Based on these results, we hypothesized that Bpp_ov failed to colonize mice because of its sensitivity to murine complement. Consistent with this, the Bpp_ov defect in the colonization of wild type mice was not observed in mice lacking the central complement component C3. Furthermore, Bpp_ov strains were highly susceptible to killing by murine complement, but not by sheep complement. These data demonstrate that the failure of Bpp_ov to colonize mice is due to sensitivity to murine, but not sheep, complement, providing a mechanistic example of how specialization that accompanies expansion in one host can limit host range.

Evaluation of adjuvant effects of fucoidan for improving vaccine efficacy

Fucoidan is a sulfated polysaccharide derived from brown seaweed, including Fucus vesiculosus. This compound is known to have immunostimulatory effects on various types of immune cells including macrophages and dendritic cells. A recent study described the application of fucoidan as a vaccine adjuvant. Vaccination is regarded as the most efficient prophylactic method for preventing harmful or epidemic diseases. To increase vaccine efficacy, effective adjuvants are needed. In the present study, we determined whether fucoidan can function as an adjuvant using vaccine antigens. Flow cytometric analysis revealed that fucoidan increases the expression of the activation markers major histocompatibility complex class II, cluster of differentiation (CD)25, and CD69 in spleen cells. In combination with Bordetella bronchiseptica antigen, fucoidan increased the viability and tumor necrosis factor-α production of spleen cells. Furthermore, fucoidan increased the in vivo production of antigen-specific antibodies in mice inoculated with Mycoplasma hyopneumoniae antigen. Overall, this study has provided valuable information about the use of fucoidan as a vaccine adjuvant.

Antibody responses to Bordetella bronchiseptica in vaccinated and infected dogs

Bordetella bronchiseptica (Bb) whole cell bacterins have been replaced with acelluar vaccines. We evaluated the response to the acellular Bb vaccines in Bb-seropositive commingled laboratory beagles and client-owned dogs with various lifestyles and vaccination histories. A single parenteral dose of the acellular Bb vaccine resulted in consistent anamnestic IgG, and to a lesser, but notable extent, IgA, Bb-reactive antibody responses in the seropositive beagles. Associated with the increase in antibodies measured by enzyme-linked immunosorbent assay (ELISA) was an increase in the complement (C)-dependent IgG antibody mediated bactericidal effect on Bb in vitro. Antibody responses in client-owned dogs were more variable and were dependent upon the vaccination history and serological evidence of previous Bb exposure. Antibodies from vaccinated dogs recognized several Bb proteins, notably P68 (pertactin) and P220 (fimbrial hemagglutinin), the response to which has been shown to be disease-sparing in Bp infections. These antibody responses were similar to those in experimentally infected dogs and in dogs that had received a widely used whole cell bacterin.

Toll-like receptor 4 limits transmission of Bordetella bronchiseptica

Transmission of pathogens has been notoriously difficult to study under laboratory conditions leaving knowledge gaps regarding how bacterial factors and host immune components affect the spread of infections between hosts. We describe the development of a mouse model of transmission of a natural pathogen, Bordetella bronchiseptica, and its use to assess the impact of host immune functions. Although B. bronchiseptica transmits poorly between wild-type mice and mice lacking other immune components, it transmits efficiently between mice deficient in Toll-Like Receptor 4 (TLR4). TLR4-mutant mice were more susceptible to initial colonization, and poorly controlled pathogen growth and shedding. Heavy neutrophil infiltration distinguished TLR4-deficient responses, and neutrophil depletion did not affect respiratory CFU load, but decreased bacterial shedding. The effect of TLR4 response on transmission may explain the extensive variation in TLR4 agonist potency observed among closely related subspecies of Bordetella. This transmission model will enable mechanistic studies of how pathogens spread from one host to another, the defining feature of infectious disease.

Immuno-epidemiology of chronic bacterial and helminth co-infections: observations from the field and evidence from the laboratory

Co-infections can alter the host immune responses and modify the intensity and dynamics of concurrent parasitic species. The extent of this effect depends on the properties of the system and the mechanisms of host-parasite and parasite-parasite interactions. We examined the immuno-epidemiology of a chronic co-infection to reveal the immune mediated relationships between two parasites colonising independent organs, and the within-host molecular processes influencing the dynamics of infection at the host population level. The respiratory bacterium, Bordetella bronchiseptica, and the gastrointestinal helminth, Graphidium strigosum, were studied in the European rabbit (Oryctolagus cuniculus), using long-term field data and a laboratory experiment. We found that 65% of the rabbit population was co-infected with the two parasites; prevalence and intensity of co-infection increased with rabbit age and exhibited a strong seasonal pattern with the lowest values recorded during host breeding (from April to July) and the highest in the winter months. Laboratory infections showed no significant immune-mediated effects of the helminth on bacterial intensity in the lower respiratory tract but a higher abundance was observed in the nasal cavity during the chronic phase of the infection, compared with single bacterial infections. In contrast, B. bronchiseptica enhanced helminth intensity and this was consistent throughout the 4-month trial. These patterns were associated with changes in the immune profiles between singly and co-infected individuals for both parasites. This study confirmed the general observation that co-infections alter the host immune responses but also highlighted the often ignored role of bacterial infection in helminth dynamics. Additionally, we showed that G. strigosum had contrasting effects on B. bronchiseptica colonising different parts of the respiratory tract. At the host population level our findings suggest that B. bronchiseptica facilitates G. strigosum infection, and re-infection with G. strigosum assists in maintaining bacterial infection in the upper respiratory tract and thus long-term persistence.

Seroepidemiology of respiratory (group 2) canine coronavirus, canine parainfluenza virus, and Bordetella bronchiseptica infections in urban dogs in a humane shelter and in rural dogs in small communities

This prospective study evaluated seroepidemiologic features of canine respiratory coronavirus (CRCoV), canine parainfluenza virus (CPIV), and Bordetella bronchiseptica infections in dogs in an urban humane shelter and in rural/small community dog populations in western Canada. Seroprevalence of CRCoV and CPIV was low compared with other countries; seroprevalence of B. bronchiseptica was moderate to high in most populations examined. Rural dogs were 0.421 times (P ≤ 0.0001) less likely to be positive for CRCoV than dogs admitted to the shelter. There were no statistical differences in prevalence of antibodies to B. bronchiseptica and CPIV between urban and rural populations. Dogs from Fort Resolution, NWT were significantly (P < 0.05) less likely to have moderate or high antibody titers to the 3 agents than dogs in the shelter. Seroconversion to CRCoV was common in dogs in the shelter, but was not associated (P = 0.18) with respiratory disease. Antibodies to CRCoV, CPIV, or B. bronchiseptica on arrival were not significantly (P > 0.05) associated with disease-sparing after entry into the shelter.

[Immunogenicity and protective efficacy of pertactin recombinants against Bordetella bronchiseptica challenge]

OBJECTIVE

In this study we showed the immunogenicity and protective efficacy of five pertactin recombinants against Bordetella bronchiseptica (Bb) challenge.

METHODS AND RESULTS

The complete coding sequence (2040 bp) of the prn gene (PRN) and its fragments,5'-terminal 1173 bp fragment (PN),3'-terminal 867 bp fragment (PC), two copies of region I (654 bp; PR I) in PN, and 2 copies of region II (678 bp; PR II) in PC, were separately cloned into the prokaryotic expression vector pGEX-KG, and expressed in the Eschierichia coli BL21 (DE3) using induction by isopropyl-beta-D-thiogalactopyranoside. The recombinant proteins were named GST-PRN, GST-PN, GST-PC, GST-2PR I and GST-2PR II. All five recombinant proteins showed immunological reactivity in the Western-blot analysis. Mice, immunized subcutaneously with two doses of the purified proteins mixed with an equal volume of Freund's adjuvant,produced robust PRN-specific IgG antibody levels. When challenged, 6 of 9 mice in GST-2PR I group and all 9 mice in the other groups survived intranasal challenge with three times the 50% lethal dose (LD50) of virulent Bb HH0809. After challenge with 10 LD50 7/9,3/9,6/9,1/10 and 6/10 of the mice survived. Furthermore, complete protection against intraperitoneal (i.p.) challenge with 10 LD50 of HH0809 was observed in mice that were injected i.p. with 0.5 ml rabbit anti-GST-PRN, GST-PN,GST-PC or GST-2PR II serum. Only 1 of 10 mice survived in the group of mice that received anti-GST-2PR I, and no survivors were noted in the group of mice that received PRN-absorbed rabbit antiserum (0/5).

CONCLUSION

In this study,we showed that all of five pertactin recombinants had differential immunogenicity and protective efficacy against Bb challenge. Mice immunized with GST-PC had better survival against fatal Bb challenge than did those immunized with GST-PN. In addition, GST-2PR II and GST-2PR I provided the similar results These data may have implications for the development of safe and efficacious subunit vaccines for the prevention of bordetellosis on the basis of these five pertactin recombinants.

Simultaneous analysis of the nasal shedding kinetics of field and vaccine strains of Bordetella bronchiseptica

Groups of four two-week-old puppies were administered serial dilutions of an intranasal vaccine containing live Bordetella bronchiseptica and canine parainfluenza virus vaccine and housed individually in isolator cages. Three vaccinated groups and one unvaccinated control group were exposed to virulent B bronchiseptica four weeks after vaccination and evaluated. Nasal swabs for bacterial culture and sera for agglutination tests were taken from all the dogs every week for four weeks. The bacteria isolated were identified by growth on specific agar and by specific PCR to distinguish between vaccine and challenge strains. The vaccine strain persisted in the nasal cavity after vaccination but no adverse reactions were observed. Serum agglutination titres were raised in the vaccinated dogs at challenge. Vaccine strains were not isolated after the challenge from most of the vaccinated dogs. The challenge strain was shed in the dogs vaccinated with the lowest dose (10(6.0) cfu/dose) for two to three weeks but the other vaccinated groups (10(7.0) and 10(8.0) cfu/dose) shed the challenge strain transiently or not at all. Only the group vaccinated with 10(6.0) cfu/dose exhibited clinical signs after challenge.

Chitosan microspheres containing Bordetella bronchiseptica antigens as novel vaccine against atrophic rhinitis in pigs

The immune-stimulating activities of Bordetella bronchiseptica antigens containing dermonecrotoxin (BBD) loaded in chitosan microspheres (CMs) have already been reported in vitro and in vivo with a mouse alveolar macrophage cell line (RAW264.7) and mice. Therefore, this study attempted to demonstrate the successful induction of mucosal immune responses after the intranasal administration of BBD loaded in CMs (BBD-CMs) in colostrum-deprived pigs. The BBD was introduced to the CMs using an ionic gelation process involving tripolyphosphate (TPP). Colostrum-deprived pigs were then directly immunized through intranasal administration of the BBD-CMs. A challenge with a field isolate of B. bronchiseptica was performed ten days following the final immunization. The BBD-specific IgG and IgA titers, evident in the nasal wash and serum from the vaccinated pigs, increased with time (p<0.05). Following the challenge, the clinical signs of infection were about 6-fold lower in the vaccinated pigs compared with the nonvaccinated pigs. The grades for gross morphological changes in the turbinate bones from the vaccinated pigs were also significantly lower than the grades recorded for the nonvaccinated pigs (p<0.001). Therefore, the mucosal and systemic immune responses induced in the current study would seem to indicate that the intranasal administration of BBD-CMs may be an effective vaccine against atrophic rhinitis in pigs.

[Protecting mice from fatal Bordetella bronchiseptica infection by immunization with recombinant pertactin antigens]

OBJECTIVE

We evaluated the efficacy of the recombinant pertactin (PRN)-specific active or passive immunization against Bordetella bronchiseptica (Bb) in an aerosol challenge model established by using BALB/c mice.

METHODS AND RESULTS

Mice, immunized subcutaneously with two doses of purified glutathione S-transferase (GST)-PRN protein mixed with an equal volume of Freund's adjuvant, produced robust PRN-specific IgG antibody activity. All 20 mice vaccinated with GST-PRN protein survived aerosol challenge with three times the 50% lethal dose (LD50) of virulent Bb HH0809 compared with 3 of 20 GST protein-treated controls and 4 of 20 PBS-treated controls that survived. Furthermore, we observed complete protection against intraperitoneal challenge with ten times the LD50 of virulent HH0809 strain in mice that were injected intraperitoneally with 0.5 ml rabbit anti-GST-PRN serum. No survivors were observed in mice that received either rabbit anti-GST serum or PBS alone.

CONCLUSION

The recombinant PRN protein had strong immunogenicity against Bb infection.

Demonstration of 1-year duration of immunity for attenuated Bordetella bronchiseptica vaccines in dogs

Three groups of healthy dogs with low antibody titers to Bordetella bronchiseptica (Bb), canine parainfluenza virus (CPI), and canine adenovirus type 2 (CAV-2) were used in this study. One group was vaccinated with a single dose of monovalent attenuated Bb vaccine and one group with a trivalent vaccine containing attenuated Bb, CPI, and CAV-2; dogs were vaccinated intranasally with a single dose of the respective vaccines. The third group served as unvaccinated controls. All vaccinated dogs subsequently developed serum antibody titers to Bb that persisted for at least 1 year. Following Bb challenge 1 year after vaccination, all vaccinated dogs, regardless of group, showed significantly fewer clinical signs and shed significantly fewer challenge organisms than unvaccinated controls. These results demonstrate that intranasal administration of a single dose of monovalent attenuated Bb vaccine or trivalent vaccine containing attenuated Bb, CPI, and CAV-2 provides 1 year of protection against Bb.

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.

Pluronic® F127 enhances the effect as an adjuvant of chitosan microspheres in the intranasal delivery of Bordetella bronchiseptica antigens containing dermonecrotoxin

We have studied a vaccine delivery system in vitro and in vivo based on chitosan microspheres (CMs) prepared in the presence of selected immunomodulators, Pluronic block copolymer F127 (F127). The Bordetella bronchiseptica multiple antigens containing dermonecrotoxin (BBD), a virulent factor leading to atrophic rhinitis (AR) in swine was loaded in CMs/F127 or CMs alone. The microspheres, prepared using an ionic gelation process with tripolyphosphate, demonstrated release profiles that showed a greater amount of BBD being released from BBD-loaded CMs/F127 (BBD-CMs/F127). In vitro experiments using mouse alveolar macrophage cells (RAW 264.7) demonstrated that BBD-CMs/F127 have significantly higher immune-stimulating activities than controls. The highest immune-stimulating activities by the BBD-CMs/F127 using RAW 264.7 cells were mirrored in the in vivo studies following nasal administration to mice. The mice immunized with BBD-CMs/F127 showed higher BBD specific IgA antibody responses in nasal wash, saliva and serum than mice immunized with BBD-CMs alone. Protective immunity was measured by survival rate after challenge with B. bronchiseptica via the nasal cavity. The survival rate of the group treated with BBD-CMs/F127 was higher than those of other groups. These results suggested that CMs/F127 represents a novel mucosal delivery system and that F127 could enhance the delivery of BBD-CMs in the vaccination scheme.

Use of a genetically defined double mutant strain of Bordetella bronchiseptica lacking adenylate cyclase and type III secretion as a live vaccine

While most vaccines consisting of killed bacteria induce high serum antibody titers, they do not always confer protection as effective as that induced by infection, particularly against mucosal pathogens. Bordetella bronchiseptica is a gram-negative respiratory pathogen that is endemic in many nonhuman mammalian populations and causes substantial disease in a variety of animals. At least 14 different live attenuated vaccines against this pathogen are available for use in a variety of livestock and companion animals. However, there are few published data on the makeup or efficacy of these vaccines. Here we report the use of a genetically engineered double mutant of B. bronchiseptica, which lacks adenylate cyclase and type III secretion, as a vaccine candidate. This strain is safe at high doses, even for highly immunocompromised animals, and induces immune responses that are protective against highly divergent B. bronchiseptica strains, preventing colonization in the lower respiratory tract and decreasing the bacterial burden in the upper respiratory tract. This novel B. bronchiseptica vaccine candidate induces strong local immunity while eliminating damage caused by the two predominant cytotoxic mechanisms.

Different mechanisms of vaccine-induced and infection-induced immunity to Bordetella bronchiseptica

A recent resurgence in the number of cases of whooping cough, and other respiratory diseases caused by members of the bordetellae, in vaccinated populations has demonstrated the need for a thorough understanding of vaccine-induced immunity to facilitate more intelligent vaccine design. In this work, we use a murine model of respiratory infection using the highly successful animal pathogen, Bordetella bronchiseptica. Since previously infected animals have been shown to resist re-infection by B. bronchiseptica, we sought to examine the differences between vaccine-induced immunity and infection-induced immunity. Both prior infection and vaccination conferred nearly complete protection in the lungs, however, only prior infection resulted in significant protection in the upper respiratory tract. While immunity induced by prior infection offered significant protection even in the absence of complement or FcgammaRs, vaccination-induced protection required both complement and FcgammaRs. Although vaccination induced higher titers of B. bronchiseptica-specific antibodies, this serum was less effective than infection-induced serum in clearing bacteria from the lower respiratory tract. Together these findings highlight substantial differences between the mechanisms involved in vaccine- and infection-induced protective immunity.

Compatibility of a bivalent modified-live vaccine against Bordetella bronchiseptica and cp iV , and a trivalent modified-live vaccine against cpv , cdv and cav-2

Eight puppies (group 1) were vaccinated once with a bivalent modified-live vaccine against infectious tracheobronchitis by the intranasal route and at the same time with an injectable trivalent vaccine against canine parvovirus, canine distemper virus and canine adenovirus; a second group of eight puppies (group 2) was vaccinated only with the intranasal bivalent vaccine, and a further eight puppies (group 3) were vaccinated only with the injectable trivalent vaccine. Three weeks later they were all challenged with wildtype Bordetella bronchiseptica and canine parainfluenza virus by the aerosol route, and their antibody responses to the five vaccine organisms were determined. Oronasal swabs were taken regularly before and after the challenge for the isolation of bacteria and viruses, and the puppies were observed for clinical signs for three weeks after the challenge. There were no significant differences in the puppies' titres against canine parvovirus, canine distemper virus and canine adenovirus type 2 between the groups vaccinated with or without the bivalent intranasal vaccine. After the challenge the mean clinical scores of the two groups vaccinated with the intranasal vaccine were nearly 90 per cent lower (P=0.001) than the mean score of the group vaccinated with only the trivalent injectable vaccine, and the puppies in this group all became culture-positive for B bronchiseptica and canine parainfluenza virus. There were only small differences between the rates of isolation of B bronchiseptica from groups 1, 2 and 3, but significantly lower yields of canine parainfluenza virus were isolated from groups 1 and 2 than from group 3.

Bordetella bronchiseptica modulates macrophage phenotype leading to the inhibition of CD4+ T cell proliferation and the initiation of a Th17 immune response

Bordetella bronchiseptica is a Gram-negative bacterium equipped with several colonization factors that allow it to establish a persistent infection of the murine respiratory tract. Previous studies indicate that B. bronchiseptica adenylate cyclase toxin (ACT) and the type III secretion system (TTSS) synergize to drive dendritic cells into an altered phenotype to down-regulate the host immune response. In this study, we examined the effects of B. bronchiseptica ACT and TTSS on murine bone marrow-derived macrophages. We demonstrate that ACT and TTSS are required for the inhibition of Ag-driven CD4+ T cell proliferation by bacteria-infected macrophages. We identify PGE2 as the mediator of this inhibition, and we show that ACT and the TTSS synergize to increase macrophage production of PGE2. We further demonstrate that B. bronchiseptica can modulate normal macrophage function and drive the immune response toward a Th17 phenotype classified by the significant production of IL-17. In this study, we show that B. bronchiseptica-infected macrophages can induce IL-17 production from naive CD4+ splenocytes, and that lung tissues from B. bronchiseptica-infected mice exhibit a strong Th17 immune response. ACT inhibited surface expression of CD40 and CD86, suppressed TNF-alpha production, and up-regulated IL-6 production. TTSS also synergized with ACT to up-regulate IL-10 and PGE2 secretion. These findings indicate that persistent colonization by B. bronchiseptica may rely on the ability of the bacteria to differentially modulate both macrophage and dendritic cell function leading to an altered adaptive immune response and subsequent bacterial colonization.

Comparison of the mucosal immune response in dogs vaccinated with either an intranasal avirulent live culture or a subcutaneous antigen extract vaccine of Bordetella bronchiseptica

Healthy dogs with low antibody titer to Bordetella bronchiseptica were vaccinated intranasally with an avirulent live vaccine, subcutaneously with an antigen extract vaccine, or subcutaneously and intranasally with a placebo. Intranasally vaccinated dogs developed B. bronchiseptica-specific IgA titers in nasal secretions that remained at high levels until the end of the study; dogs vaccinated subcutaneously with the antigen extract or placebo did not develop measurable antigen-specific IgA titers in nasal secretions. Dogs were challenged with virulent live B. bronchiseptica 63 days after vaccination. Intranasally vaccinated dogs had significantly lower cough scores (P < or =.0058) and shed significantly fewer challenge organisms (P <.0001) than dogs in either of the other groups. Cough scores of subcutaneously vaccinated dogs were not significantly different from placebo-vaccinated dogs.

In vivo induction of mucosal immune responses by intranasal administration of chitosan microspheres containing Bordetella bronchiseptica DNT

In vitro immune-stimulating activities of Bordetella bronchiseptica dermonecrotoxin (BBD)-loaded in chitosan microspheres (CMs) were reported with a mouse alveolar macrophage cell line (RAW264.7). Based on the report, in vivo activity of immune-induction was investigated by intranasal administration of the BBD-loaded CMs into mice. BBD was loaded into the CMs prepared by an ionic gelation process with tripolyphosphate. Mice were immunized by direct administration of the BBD-loaded CMs into the nasal cavity. After immunization of the mice, BBD-specific immune responses (IgG and IgA titers) were measured in sera, nasal wash, and saliva by ELISA. BBD-specific IgA titers in the nasal cavity were time- and dose-dependently increased by the administration. Similar phenomena were observed in the analysis of systemic IgA and IgG in sera. However, the antibody in saliva was undetectable by ELISA. These results suggested that direct vaccination via the nasal cavity was effective for targeting nasal-associated lymphoid tissues, and that CMs were an efficient adjuvant in nasal mucosal immunity for atrophic rhinitis vaccine.

The Bordetella bronchiseptica type III secretion system inhibits gamma interferon production that is required for efficient antibody-mediated bacterial clearance

Several species of pathogenic microorganisms have developed strategies to survive and persist in vital organs which are normally maintained as sterile by the generation of strong immune responses. Here, we report an immunomodulation involving the Bordetella bronchiseptica type III secretion system (TTSS) which contributes to bacterial survival in the lower respiratory tract of the host. The prolonged persistence of B. bronchiseptica that was observed in gamma interferon (IFN-gamma)-/- mice indicates that the efficient clearance of bacteria from the lower respiratory tract requires not only B cells and antibodies but also IFN-gamma production. Our data also suggest that interleukin-10 (IL-10)-producing splenocytes are generated early during infection and that IL-10 inhibits IFN-gamma-producing cells and delays the clearance of B. bronchiseptica from the lungs. The TTSS of B. bronchiseptica inhibits the generation of IFN-gamma-producing splenocytes and is required for long-term bacterial persistence in the lower respiratory tract in wild-type mice. This suggests that a mechanism involving the modulation of IFN-gamma production by the TTSS facilitates B. bronchiseptica survival in the lower respiratory tract.

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.

Bordetella bronchiseptica flagellin is a proinflammatory determinant for airway epithelial cells

Motility is an important virulence phenotype for many bacteria, and flagellin, the monomeric component of flagella, is a potent proinflammatory factor. Of the three Bordetella species, Bordetella pertussis and Bordetella parapertussis are nonmotile human pathogens, while Bordetella bronchiseptica expresses flagellin and causes disease in animals and immunocompromised human hosts. The BvgAS two-component signal transduction system regulates phenotypic-phase transition (Bvg+, Bvg-, and Bvg(i)) in bordetellae. The Bvg- phase of B. bronchiseptica is characterized by the expression of flagellin and the repression of adhesins and toxins necessary for the colonization of the respiratory tract. B. bronchiseptica naturally infects a variety of animal hosts and constitutes an excellent model to study Bordetella pathogenesis. Using in vitro coculture models of bacteria and human lung epithelial cells, we studied the effects of B. bronchiseptica flagellin on host defense responses. Our results show that B. bronchiseptica flagellin is a potent proinflammatory factor that induces chemokine, cytokine, and host defense gene expression. Furthermore, we investigated receptor specificity in the response to B. bronchiseptica flagellin. Our results show that B. bronchiseptica flagellin is able to signal effectively through both human and mouse Toll-like receptor 5.

Bordetella type III secretion modulates dendritic cell migration resulting in immunosuppression and bacterial persistence

Chronic bacterial infection reflects a balance between the host immune response and bacterial factors that promote colonization and immune evasion. Bordetella bronchiseptica uses a type III secretion system (TTSS) to persist in the lower respiratory tract of mice. We hypothesize that colonization is facilitated by bacteria-driven modulation of dendritic cells (DCs), which leads to an immunosuppressive adaptive host response. Migration of DCs to the draining lymph nodes of the respiratory tract was significantly increased in mice infected with wild-type B. bronchiseptica compared with mice infected with TTSS mutant bacteria. Reduced colonization by TTSS-deficient bacteria was evident by 7 days after infection, whereas colonization by wild-type bacteria remained high. This decrease in colonization correlated with peak IFN-gamma production by restimulated splenocytes from infected animals. Wild-type bacteria also elicited peak IFN-gamma production on day 7, but the quantity was significantly lower than that elicited by TTSS mutant bacteria. Additionally, wild-type bacteria elicited higher levels of the immunosuppressive cytokine IL-10 compared with the TTSS mutant bacteria. B. bronchiseptica colonization in IL-10(-/-) mice was significantly reduced compared with infections in wild-type mice. These findings suggest that B. bronchiseptica use the TTSS to rapidly drive respiratory DCs to secondary lymphoid tissues where these APCs stimulate an immunosuppressive response characterized by increased IL-10 and decreased IFN-gamma production that favors bacterial persistence.

The Complex Mechanism of Antibody-Mediated Clearance ofBordetellafrom the Lungs Requires TLR4

Although the antibacterial effects of Abs are well studied in in vitro systems, the in vivo effects of Abs cannot always be accurately predicted. Complicated cross-talk between different effector functions of Abs and various arms of the immune system can affect their activities in vivo. Using the mouse respiratory pathogen Bordetella bronchiseptica, we examined the mechanisms of Ab-mediated clearance of bacteria from the respiratory tract. Interestingly, although TLR4 was not necessary for protective immunity following infection, it was required for rapid bacterial clearance in mice that were vaccinated or adoptively transferred Abs. TLR4 was important for the rapid recruitment of neutrophils that are necessary for Ab-mediated bacterial clearance via a mechanism that requires both FcgammaR and CR3. These data are consistent with a model in which TLR4-mediated inflammatory responses aid in the recruitment of neutrophils, which phagocytose Ab- and complement-opsonized bacteria via FcgammaRs and CR3. Although pattern recognition receptors are known to be involved in innate immunity and the generation of adaptive immunity, their contributions to specific adaptive immune functions should be considered in ongoing efforts to improve vaccine-induced protective immunity.

Protection of dogs for 13 months against Bordetella bronchiseptica and canine parainfluenza virus with a modified live vaccine

Twelve specific pathogen-free (spf) puppies were vaccinated intranasally with a bivalent, modified live vaccine against infectious tracheobronchitis (group 1) and six puppies of the same age and from the same source served as unvaccinated controls (group 2). Both groups were challenged with wild-type Bordetella bronchiseptica and canine parainfluenza virus by the aerosol route 56 weeks after group 1 had been vaccinated, and at the same time six 10-week-old spf puppies from the same source (group 3) were also challenged. Oronasal swabs were taken regularly before and after the challenge, for the isolation of bacteria and viruses, and the dogs were observed for clinical signs for three weeks after the challenge. The control dogs became culture-positive for B bronchiseptica and canine parainfluenza virus, but the isolation yields from the vaccinated group were significantly lower (P<0.05). The mean clinical scores of the vaccinated group were 61 per cent lower than the scores of group 2 (P=0.009), and 90 per cent lower than the scores of group 3 (P=0.001).

Factors associated with upper respiratory tract disease caused by feline herpesvirus, feline calicivirus, Chlamydophila felis and Bordetella bronchiseptica in cats: experience from 218 European catteries

A full history of the management practices and the prevalence of upper respiratory tract disease (URTD) at 218 rescue shelters, breeding establishments and private households with five or more cats was recorded. Oropharyngeal and conjunctival swabs and blood samples were taken from 1748 cats. The prevalences of feline herpesvirus (FHV), feline calicivirus (FCV), Chlamydophila felis and Bordetella bronchiseptica were determined by PCR on swab samples. An ELISA was applied to determine the prevalence of antibodies to B. bronchiseptica. The rates of detection by PCR of each pathogen in the cats in catteries with and without ongoing URTD were, respectively, FHV 16 per cent and 8 per cent; FCV 47 per cent and 29 per cent; C. felis 10 per cent and 3 per cent; and B. bronchiseptica 5 per cent and 1.3 per cent; the seroprevalences of B. bronchiseptica were 61 per cent and 41 per cent, respectively. There was evidence that FHV, FCV and B. bronchiseptica played a role in URTD. The risk factors associated with the disease were less than excellent hygiene, contact with dogs with URTD, and larger numbers of cats in the cattery or household.

Role of Bordetella bronchiseptica adenylate cyclase in nasal colonization and in development of local and systemic immune responses in piglets

Two Bordetella bronchiseptica mutants, lacking the adenylate cyclase (Cya) or both Cya and pertactin (Prn), were compared with their parental strain NL1013 in their abilities to colonize the nose of neonate piglets and to induce local and systemic antibody responses against filamentous hemagglutinin (FHA) after intranasal (i.n.) inoculation. The number of bacteria recovered and the duration of infection in the nasal secretions were greater for the wild-type parent strain than for the Cya-deficient mutant, indicating that Cya plays an important role during B. bronchiseptica colonization of the nasal cavity. The double mutant did not colonize the nasal cavity and was less able to adhere to epithelial cells in vitro than the other two strains, supporting the hypothesis that Prn plays a major role in cell adhesion. In piglets inoculated with the wild type strain, anti-FHA IgM was found in the nasal secretions one week after inoculation, followed two weeks later by anti-FHA IgA; their presence was concomitant with decreases in bacterial counts. Anti-FHA IgG appeared at six weeks after infection in the serum. In contrast, i.n. inoculation with either mutant failed to induce a nasal secretory antibody response but did induce an earlier and higher IgM response in the serum than inoculation with the wild type strain. However, only the Cya-deficient mutant was able to prime the piglets for the development of a secondary nasal IgM and serum IgG response to FHA after intranasal inoculation with the wild type B. bronchiseptica.

Downregulation of mitogen-activated protein kinases by the Bordetella bronchiseptica Type III secretion system leads to attenuated nonclassical macrophage activation

Bordetella bronchiseptica utilizes a type III secretion system (TTSS) to establish a persistent infection of the murine respiratory tract. Previous studies have shown that the Bordetella TTSS mediated cytotoxicity in different cell types, inhibition of NF-kappaB in epithelial cells, and differentiation of dendritic cells into a semimature state. Here we demonstrate modulation of mitogen-activated protein kinase (MAPK) signaling pathways and altered cytokine production in macrophages and dendritic cells by the Bordetella TTSS. In macrophages, the MAPKs ERK and p38 were downregulated. This resulted in attenuated production of interleukin- (IL-)6 and IL-10. In contrast, the Th-1-polarizing cytokine IL-12 was produced at very low levels and remained unmodulated by the Bordetella TTSS. In dendritic cells, ERK was transiently activated, but this failed to alter cytokine profiles. These results suggest that the Bordetella TTSS modulates antigen-presenting cells in a cell type-specific manner and the secretion of high levels of IL-6 and IL-10 by macrophages might be important for pathogen clearance.

Intranasal immunisation against tetanus with an attenuated Bordetella bronchiseptica vector expressing FrgC: improved immunogenicity using a Bvg-regulated promoter to express FrgC

Mice were immunised intranasally with live Bordetella bronchiseptica aroA strains possessing plasmids encoding fragment C (FrgC) of tetanus toxin. FrgC was expressed either from a constitutive tac promoter (strain GVB120) or the Bvg-dependent fhaB promoter (strain GVB1543). Serum anti-FrgC antibody titres were detected in all mice immunised with GVB1543 and GVB120 but the average titres were higher and the responses to FrgC were more consistent in GVB1543 immunised animals. This was reflected in the protective immunity conferred by the different strains: 100% of GVB1543 immunised mice were protected against tetanus toxin challenge whereas only 60% of animals immunised with GVB120 survived tetanus challenge. Viability of the B. bronchiseptica vector strain was shown to be critical to its efficacy as a vector for FrgC.

Toll-like receptor 4-dependent early elicited tumor necrosis factor alpha expression is critical for innate host defense against Bordetella bronchiseptica

Toll-like receptor 4 (TLR4) mediates the response to lipopolysaccharide, and its activation induces the expression of a large number of inflammatory genes, many of which are also induced by other pathogen-associated molecular patterns. Interestingly, the subset of genes that are dependent on TLR4 for optimal expression during gram-negative bacterial infection has not been determined. We have previously shown that TLR4-deficient mice rapidly develop acute pneumonia after inoculation with Bordetella bronchiseptica, suggesting that TLR4 is required for expression of early elicited gene products in this model. Microarray analysis with macrophages derived from wild-type and TLR4-deficient mice was used to identify genes whose expression, within 1 h of bacterial exposure, is dependent on TLR4. The results of this investigation suggest that TLR4 is not required for the majority of the transcriptional response to B. bronchiseptica. However, early tumor necrosis factor alpha (TNF-alpha) mRNA expression is primarily dependent on TLR4 and in vitro and in vivo protein levels substantiate this finding. TLR4-deficient mice and TNF-alpha-/- mice are similarly susceptible to infection with relatively low doses of B. bronchiseptica and in vivo neutralization studies indicate that it is the TLR4-dependent early elicited TNF-alpha response that is critical for preventing severe pneumonia and limiting bacterial growth. These results suggest that one critical role for TLR4 is the generation of a robust but transient TNF-alpha response that is critical to innate host defense during acute gram-negative respiratory infection.

Bordetella type III secretion and adenylate cyclase toxin synergize to drive dendritic cells into a semimature state

Bordetella bronchiseptica establishes persistent infection of the murine respiratory tract. We hypothesize that long-term colonization is mediated in part by bacteria-driven modulation of dendritic cells (DCs) leading to altered adaptive immune responses. Bone marrow-derived DCs (BMDCs) from C57BL/6 mice infected with live B. bronchiseptica exhibited high surface expression of MHCII, CD86, and CD80. However, B. bronchiseptica-infected BMDCs did not exhibit significant increases in CD40 surface expression and IL-12 secretion compared with BMDCs treated with heat-killed B. bronchiseptica. The B. bronchiseptica type III secretion system (TTSS) mediated the increase in MHCII, CD86, and CD80 surface expression, while the inhibition of CD40 and IL-12 expression was mediated by adenylate cyclase toxin (ACT). IL-6 secretion was independent of the TTSS and ACT. These phenotypic changes may result from differential regulation of MAPK signaling in DCs. Wild-type B. bronchiseptica activated the ERK 1/2 signaling pathway in a TTSS-dependent manner. Additionally, ACT was found to inhibit p38 signaling. These data suggest that B. bronchiseptica drive DC into a semimature phenotype by altering MAPK signaling. These semimature DCs may induce tolerogenic immune responses that allow the persistent colonization of B. bronchiseptica in the host respiratory tract.

In vitro study of the immune stimulating activity of an athrophic rhinitis vaccine associated to chitosan microspheres

Chitosan microspheres (CMs) were prepared by an ionic gelation process with tripolyphosphate and characterized. Bordetella Bronchiseptica Dermonecrotoxin (BBD), a major virulence factor of a causative agent of atrophic rhinitis (AR), was loaded on to the CMs for nasal vaccination. BBD-loaded CMs were observed as aggregated shapes although unloaded CMs were observed as relatively spherical ones. The average particle size of the BBD-loaded CMs was 4.39 microm. The lower the molecular weight of chitosan and the higher the medium pH, the greater was the release of BBD from the BBD-loaded CMs in vitro due to weaker intermolecular interaction between chitosan and BBD. Tumor necrosis factor alpha and nitric oxide from RAW264.7 cells exposed to BBD-loaded CMs were gradually secreted with time, suggesting that released BBD from CMs had immune stimulating activity of AR vaccine in vitro.

A placebo-controlled trial of two intranasal vaccines to prevent tracheobronchitis (kennel cough) in dogs entering a humane shelter

A placebo-controlled field trial was conducted to compare the effectiveness of intranasal (IN) vaccines containing Bordetella bronchiseptica and canine-parainfluenza virus, with (IN-BPA) or without (IN-BP) canine-adenovirus type 2, for prevention of kennel cough at a humane shelter. Dogs were examined on admission to the shelter and those without respiratory signs of disease were assigned daily, on a rotating basis, to receive one of three vaccines. We enrolled 972 healthy dogs. Dogs were monitored for up to 30 days post-vaccination for coughing and other clinical signs of respiratory disease. Thirty-three (10.7%; 95% confidence interval (CI): 7.2, 14.2) dogs in the IN-BP group, 36 (10.2%; 95% CI: 7.0, 13.4) dogs in the IN-BPA group, and 42 (13.5%; 95% CI: 9.7, 17.3) dogs in the IN-P group coughed spontaneously for ≥1 day within 30 days of vaccination (P=0.37). The IN-BP and IN-BPA vaccines were 20.7 and 24.4% effective, respectively, in reducing coughing compared with a placebo vaccine. The strongest prognostic factor for coughing (regardless of vaccine group) was the number of days spent at the shelter, with each additional day increasing the risk of coughing by 3% (95% CI: 0.5, 6.3). The low incidence of coughing in the shelter during this study precluded observation of differences in vaccine effectiveness. No differences in vaccine-associated adverse events (coughing, sneezing, nasal or ocular discharge) were noted during the first 3 days post-administration or thereafter.

pagP is required for resistance to antibody-mediated complement lysis during Bordetella bronchiseptica respiratory infection

To efficiently colonize and persist in the lower respiratory tract, bacteria must survive multiple host immune mechanisms. Bordetella bronchiseptica is a gram-negative respiratory pathogen that naturally infects mice and persists in the lower respiratory tract for up to 49 days postinoculation. In this work, we examined the effect of mutation of the pagP gene on the persistence of B. bronchiseptica in the lower respiratory tract of mice. The pagP gene encodes a palmitoyl transferase that is responsible for the addition of a palmitoyl group to the lipid A region of B. bronchiseptica lipopolysaccharide. Data presented here confirm that a B. bronchiseptica deltapagP mutant demonstrates defective persistence in the lower respiratory tract of wild-type mice. We hypothesized that the defective persistence of the B. bronchiseptica deltapagP mutant was due to an increased susceptibility of this mutant to a host immune response. In vivo data indicate that both B cells and the complement component C3 are required for the reduced bacterial numbers of the deltapagP mutant on day 14 postinoculation. In addition, an in vitro complement killing assay demonstrated that B. bronchiseptica exhibits pagP-dependent resistance to antibody-mediated complement killing at low concentrations of immune serum. Taken together, these results suggest that pagP is required for B. bronchiseptica to resist antibody-mediated complement lysis during respiratory infection.

Antibody-mediated bacterial clearance from the lower respiratory tract of mice requires complement component C3

To assess the contribution of complement to respiratory immunity in the context of a natural bacterial infection, we used mice genetically deficient in complement components and the murine pathogen Bordetella bronchiseptica. Complement component C3 was not required for the control of bacterial infection or for the generation of infection-induced protective immunity. However, C3-deficient (C3(-/-)) mice were severely defective, compared to wild type, in vaccine-induced protective immunity. Adoptively transferred immune serum from convalescent wild-type or C3(-/-) animals rapidly cleared B. bronchiseptica from the lungs of wild-type mice but did not affect its growth in C3(-/-) mice, indicating that the defect is not in the generation of protective immunity, but in its function. Immune serum was effective in C5-deficient mice but had little effect in the lungs of mice lacking either Fcgamma receptors (FcgammaR) or CR3, suggesting bacterial clearance is not via direct complement-mediated lysis. Together, these data indicate that complement is required for antibody-mediated clearance of Bordetella and suggest the mechanism involves C3 opsonization of bacteria for phagocytosis that is both CR3- and FcgammaR-dependent.

Toll-like receptor 4 is critical to innate host defense in a murine model of bordetellosis

Bordetellae are important respiratory pathogens that cause pertussis (whooping cough) in humans and analogous diseases in domestic and wild animals. Immunity to Bordetella is poorly understood, in particular the early innate immune responses that contribute to inflammation, pathology, and the subsequent generation of adaptive immunity. Using B. bronchiseptica, which naturally infects mice, we show that Toll-like receptor-4 (TLR4) is required for cytokine responses to this pathogen's lipopolysaccharide (LPS) and that TLR4 deficiency results in impaired cytokine responses in vitro and in vivo. TLR4-deficient mice rapidly succumb following inoculation with as few as 1000 organisms, indicating that TLR4 is critical to innate host defense against bordetellosis.

Molecular and antigenic characterization of Bordetella bronchiseptica isolated from a wild southern sea otter (Enhydra lutris nereis) with severe suppurative bronchopneumonia

Bordetella bronchiseptica was isolated in pure culture from the lung, abdomen, and intestine of a wild free-ranging southern sea otter (Enhydra lutris nereis) with severe, suppurative bronchopneumonia. Immunohistochemistry, using antiserum raised to B. bronchiseptica, revealed strong positive staining of bacteria attached to bronchial ciliated epithelia as well as scattered positive staining in affected alveoli. Western blot analysis demonstrated that virulence factors, filamentous hemagglutinin, pertactin, and adenylate cyclase toxin are produced by the sea otter B. bronchiseptica isolate. Ribotype analysis using Pvu II restriction digests indicated that this isolate is most similar to strains commonly obtained in domestic dogs and cats.

Infección por Bordetella spp.: 19 años de diagnóstico por cultivo

INTRODUCTION

This retrospective study reviews the findings from cultures positive for Bordetella spp. obtained over a 19-year period, from January 1984 to December 2002.

METHODS

Nasopharyngeal swabs were directly plated onto charcoal agar supplemented with 10% sheep blood and cephalexin (40 mg/L). Identification of suspected colonies was done by biochemical testing and slide agglutination with specific antisera for B. pertussis and B. parapertussis. The study includes microbiological findings and epidemiological data (age, sex, yearly distribution, seasonal period and number of inpatients and outpatients).

RESULTS

The 2064 nasopharyngeal specimens yielded 269 positive cultures: B. pertussis was isolated from 244 patients, B. parapertussis from 23 and B. bronchiseptica from two. Among the positive patients, 36.9% were younger than 7 months, 38.8% were 7 months to 6 years old and 24.3% were older than 6 years of age.

CONCLUSIONS

The constant number of cases along the 19 years of the study shows that Bordetella spp. continues to circulate in our area. A high percentage of positive cultures were obtained from the group of children theoretically immunized by vaccination. Despite the low number of cases in young people and adults, adult pertussis seems to be a greater public health threat than was previously suspected and probably deserves to be further investigated. The gold standard for the diagnosis of Bordetella spp. infection is still recovery of the organism by culture, and it is especially useful for confirming outbreaks.

Expression of a truncated Pasteurella multocida toxin antigen in Bordetella bronchiseptica

Mild or subclinical respiratory infections caused by Bordetella bronchiseptica are widespread in pigs despite multiple control efforts. Infection with virulent B. bronchiseptica strains is a common risk factor in the establishment of toxin-producing strains of Pasteurella multocida in the nasal cavity of pigs leading to the disease, atrophic rhinitis (AR). This study was designed to explore the possibility of expressing a protective epitope of P. multocida toxin (PMT) in B. bronchiseptica to create single-component mucosal vaccine to control atrophic rhinitis in pigs. To achieve this, a P. multocida toxin fragment (PMTCE), that was non-toxic and protective against lethal challenge in mice, was cloned into a broad-host-range plasmid, PBBR1MCS2, and introduced into B. bronchiseptica by electroporation. The Pasteurella gene construct was placed under the regulatory control of a promoter region that was separately isolated from B. bronchiseptica and appears to be part of the heat shock protein gene family. B. bronchiseptica harboring the plasmid under antibiotic selection expressed the 80kDa PMTCE as determined by PAGE and Western blot with a PMT-specific monoclonal antibody. When introduced into the respiratory tracts of mice, B. bronchiseptica harboring the plasmid construct was reisolated in declining numbers for 72h post-inoculation. Antibody responses (IgM, IgA and IgG) to B. bronchiseptica were detected in serum and respiratory lavage, but PMTCE-specific antibodies were not detected. While further refinements of PMT expression in B. bronchiseptica are necessary, this study provides a basis for the development of a single-component, live-attenuated vaccine against atrophic rhinitis.