Use of Bordetella bronchiseptica and Bordetella pertussis as live vaccines and vectors for heterologous antigens

Differential microbial composition in parasitic vs. questing ticks based on 16S next-generation sequencing

Introduction

As tick-borne diseases rise to become the second most prevalent arthropod-transmitted disease globally, the increasing investigations focus on ticks correspondingly. Factors contributed to this increase include anthropogenic influences, changes in vertebrate faunal composition, social-recreational shifts, and climatic variation. Employing the 16S gene sequence method in next-generation sequencing (NGS) allows comprehensive pathogen identification in samples, facilitating the development of refined approaches to tick research omnidirectionally.

Methods

In our survey, we compared the microbial richness and biological diversity of ticks in Wuwei City, Gansu province, differentiating between questing ticks found in grass and parasitic ticks collected from sheep based on 16S NGS method.

Results

The results show Rickettsia, Coxiella, and Francisella were detected in all 50 Dermacentor nuttalli samples, suggesting that the co-infection may be linked to specific symbiotic bacteria in ticks. Our findings reveal significant differences in the composition and diversity of microorganisms, with the Friedmanniella and Bordetella genera existing more prevalent in parasitic ticks than in questing ticks (p < 0.05). Additionally, the network analysis demonstrates that the interactions among bacterial genera can be either promotive or inhibitive in ticks exhibiting different lifestyles with the correlation index |r| > 0.6. For instance, Francisella restrains the development of 10 other bacteria in parasitic ticks, whereas Phyllobacterium and Arthrobacter enhance colonization across all tick species.

Discussion

By leveraging NGS techniques, our study reveals a high degree of species and phylogenetic diversity within the tick microbiome. It further highlights the potential to investigate the interplay between bacterial genera in both parasitic and questing ticks residing in identical habitat environments.

Lacticaseibacillus rhamnosus: A Suitable Candidate for the Construction of Novel Bioengineered Probiotic Strains for Targeted Pathogen Control

Probiotics, with their associated beneficial effects, have gained popularity for the control of foodborne pathogens. Various sources are explored with the intent to isolate novel robust probiotic strains with a broad range of health benefits due to, among other mechanisms, the production of an array of antimicrobial compounds. One of the shortcomings of these wild-type probiotics is their non-specificity. A pursuit to circumvent this limitation led to the advent of the field of pathobiotechnology. In this discipline, specific pathogen gene(s) are cloned and expressed into a given probiotic to yield a novel pathogen-specific strain. The resultant recombinant probiotic strain will exhibit enhanced species-specific inhibition of the pathogen and its associated infection. Such probiotics are also used as vehicles to deliver therapeutic agents. As fascinating as this approach is, coupled with the availability of numerous probiotics, it brings a challenge with regard to deciding which of the probiotics to use. Nonetheless, it is indisputable that an ideal candidate must fulfil the probiotic selection criteria. This review aims to show how Lacticaseibacillus rhamnosus, a clinically best-studied probiotic, presents as such a candidate. The objective is to spark researchers’ interest to conduct further probiotic-engineering studies using L. rhamnosus, with prospects for the successful development of novel probiotic strains with enhanced beneficial attributes.

Insight of oral vaccines as an alternative approach to health and disease management: An innovative intuition and challenges

Vaccination is the most suitable and persuasive healthcare program for the prohibition of various deadly diseases. However, the higher production cost and purification strategies are out of reach for the developing nations. In this scenario, development of edible vaccine turns out to be the most promising alternative for remodeling the pharmaceutical industry with reduced production and purification costs. Generally, oral route of vaccination is mostly preferred due to its safety, compliance, low manufacturing cost and most importantly the ability to induce immunity in both systemic and mucosal sites. Genetically modified microorganisms and plants could efficiently be used as vehicles for edible vaccines. Edible vaccines are supposed to reduce the risk associated with traditional vaccines. Currently, oral vaccines are available in the market for several viral and bacterial diseases like cholera, hepatitis B, malaria, rabies etc. Herein, the review focuses on the breakthrough events in the area of edible vaccines associated with dietary microbes and plants for better control over diseases.

Genomic plasticity and antibody response of Bordetella bronchiseptica strain HT200, a natural variant from a thermal spring

Classical Bordetella species are primarily isolated from animals and humans causing asymptomatic infection to lethal pneumonia. However, isolation of these bacteria from any extra-host environmental niche has not been reported so far. Here, we have characterized the genomic plasticity and antibody response of Bordetella bronchiseptica strain HT200, isolated from a thermal spring. Genomic ANI value and SNPs-based phylogenetic tree suggest a divergent evolution of strain HT200 from a human-adapted lineage of B. bronchiseptica. Growth and survivability assay showed strain HT200 retained viability for more than 5 weeks in the filter-sterilized spring water. In addition, genes or loci encoding the Bordetella virulence factors such as DNT, ACT and LPS O-antigen were absent in strain HT200, while genes encoding other virulence factors were highly divergent. Phenotypically, strain HT200 was non-hemolytic and showed weak hemagglutination activity, but was able to colonize in the respiratory organs of mice. Further, both infection and vaccination with strain HT200 induced protective antibody response in mouse against challenge infection with virulent B. bronchiseptica strain RB50. In addition, genome of strain HT200 (DSM 26023) showed presence of accessory genes and operons encoding predicted metabolic functions pertinent to the ecological conditions of the thermal spring.

Heterologous expression of porcine reproductive and respiratory syndrome virus glycoprotein 5 in Bordetella bronchisepticaaroA mutant

Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important disease around the globe. Protection against this virus remains problematic. Here, we evaluated antibody (IgG & IgA) inducibility of a heterologous PRRSV glycoprotein 5 (GP5) expressed in a live attenuated Bordetella bronchisepticaaroA mutant strain (BBS-GP5). Mice and pigs were primed with recombinant GP5 (rGP5) subcutaneously followed by boosting with live BBS-GP5. As a result, anti-GP5 IgG was induced in both mice (P<0.001) and pigs (P<0.1). Pigs were challenged with live PRRSV (VR2332). Viral RNA was found to be significantly (P<0.01) removed in the vaccinated pig group. Overall, BBS-GP5 is a good candidate as a live attenuated vaccine against PRRSV infection.

Colonic immune stimulation by targeted oral vaccine

Background

Currently, sufficient data exist to support the use of lactobacilli as candidates for the development of new oral targeted vaccines. To this end, we have previously shown that Lactobacillus gasseri expressing the protective antigen (PA) component of anthrax toxin genetically fused to a dendritic cell (DC)-binding peptide (DCpep) induced efficacious humoral and T cell-mediated immune responses against Bacillus anthracis Sterne challenge.

Methodology/Principal Finding

In the present study, we investigated the effects of a dose dependent treatment of mice with L. gasseri expressing the PA-DCpep fusion protein on intestinal and systemic immune responses and confirmed its safety. Treatment of mice with different doses of L. gasseri expressing PA-DCpep stimulated colonic immune responses, resulting in the activation of innate immune cells, including dendritic cells, which induced robust Th1, Th17, CD4⁺Foxp3⁺ and CD8⁺Foxp3⁺ T cell immune responses. Notably, high doses of L. gasseri expressing PA-DCpep (10¹² CFU) were not toxic to the mice. Treatment of mice with L. gasseri expressing PA-DCpep triggered phenotypic maturation and the release of proinflammatory cytokines by dendritic cells and macrophages. Moreover, treatment of mice with L. gasseri expressing PA-DCpep enhanced antibody immune responses, including IgA, IgG₁, IgG_2b, IgG_2c and IgG₃. L. gasseri expressing PA-DCpep also increased the gene expression of numerous pattern recognition receptors, including Toll-like receptors, C-type lectin receptors and NOD-like receptors.

Conclusion/Significance

These findings suggest that L. gasseri expressing PA-DCpep has substantial immunopotentiating properties, as it can induce humoral and T cell-mediated immune responses upon oral administration and may be used as a safe oral vaccine against anthrax challenge.

Dual mechanism of protection by live attenuated Bordetella pertussis BPZE1 against Bordetella bronchiseptica in mice

Bordetella bronchiseptica, a gram-negative bacterium, causes chronic respiratory tract infections in a wide variety of mammalian hosts, including man, and no human vaccine is currently available. Acellular pertussis vaccines protect poorly against B. bronchiseptica, although they contain cross-reactive antigens. We have recently developed Bordetella pertussis BPZE1, a novel, live attenuated pertussis vaccine, currently completing phase I clinical trials in humans, and found that it protects against both B. pertussis and Bordetella parapertussis in mice. Here, we show that a single nasal administration of BPZE1 protects mice against lethal infection with B. bronchiseptica. After challenge, the vaccinated animals displayed markedly reduced lung inflammation and tissue damage, decreased neutrophil infiltration and increased levels of CD4(+)CD25(+)FoxP3(+) regulatory T cells in the lungs compared to non-immunized mice. Depletion of these cells abolished BPZE1-induced protection, indicating that BPZE1 protects against lethal inflammation through the recruitment of regulatory T cells. In addition, the B. bronchiseptica load was significantly decreased in the vaccinated animals. Using passive transfer experiments, protection was found to be essentially cell mediated, and BPZE1-induced Th1 and Th17 T cells recognize whole B. bronchiseptica extracts, although the participation of antibodies in protection cannot be discounted. Thus, a single administration of BPZE1 can confer protection against B. bronchiseptica in mice by a dual mechanism.

Invited review: Application of omics tools to understanding probiotic functionality

The human gut microbiota comprises autochthonous species that colonize and reside at high levels permanently and allochthonous species that originate from another source and are transient residents of the human gut. The interactions between bacteria and the human host can be classified as a continuum from symbiosis and commensalism (mutualism) to pathogenesis. Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Recent advances in omics tools and sequencing techniques have furthered our understanding of probiotic functionality and the specific interactions between probiotics and their human hosts. Although it is known that not all probiotics use the same mechanisms to confer benefits on hosts, some specific mechanisms of action have been revealed through omic investigations. These include competitive exclusion, bacteriocin-mediated protection against intestinal pathogens, intimate interactions with mucin and the intestinal epithelium, and modulation of the immune system. The ability to examine fully sequenced and annotated genomes has greatly accelerated the application of genetic approaches to elucidate many important functional roles of probiotic microbes.

Microbes, intestinal inflammation and probiotics

Inflammatory bowel disease (IBD) is known for causing disturbed homeostatic balance among the intestinal immune compartment, epithelium and microbiota. Owing to the emergence of IBD as a major cause of morbidity and mortality, great efforts have been put into understanding the sequence of intestinal inflammatory events. Intestinal macrophages and dendritic cells act in a synergistic fashion with intestinal epithelial cells and microbiota to initiate the triad that governs the intestinal immune responses (whether inflammatory or regulatory). In this review, we will discuss the interplay of intestinal epithelial cells, bacteria and the innate immune component. Moreover, whether or not genetic intervention of probiotic bacteria is a valid approach for attenuating/mitigating exaggerated inflammation and IBD will also be discussed.

Lactococcus lactis as a live vector: heterologous protein production and DNA delivery systems

Lactic acid bacteria (LAB), widely used in the food industry, are present in the intestine of most animals, including humans. The potential use of these bacteria as mucosal delivery vehicles for vaccinal, medical or technological use has been extensively investigated. Lactococcus lactis, a LAB species, is a potential candidate for the production of biologically useful proteins and for plasmid DNA delivery to eukaryotic cells. Several delivery systems have been developed to target heterologous proteins to a specific cell location (i.e., cytoplasm, cell wall or extracellular medium) and more recently to efficiently transfer DNA to eukaryotic cells. A promising application of L. lactis is its use for the development of live mucosal vaccines. Here, we have reviewed the expression of heterologous protein and the various delivery systems developed for L. lactis, as well as its use as an oral vaccine carrier.

Cross-species protection mediated by a Bordetella bronchiseptica strain lacking antigenic homologs present in acellular pertussis vaccines

The Bordetella species are Gram-negative bacterial pathogens that are characterized by long-term colonization of the mammalian respiratory tract and are causative agents of respiratory diseases in humans and animals. Despite widespread and efficient vaccination, there has been a world-wide resurgence of pertussis, which remains the leading cause of vaccine-preventable death in developed countries. It has been proposed that current acellular vaccines (Pa) composed of only a few bacterial proteins may be less efficacious because of vaccine-induced antigenic shifts and adaptations. To gain insight into the development of a newer generation of vaccines, we constructed a Bordetella bronchiseptica strain (LPaV) that does not express the antigenic homologs included in any of the Pa vaccines currently in use. This strain also lacks adenylate cyclase toxin, an essential virulence factor, and BipA, a surface protein. While LPaV colonized the mouse nose as efficiently as the wild-type strain, it was highly deficient in colonization of the lower respiratory tract and was attenuated in induction of inflammation and injury to the lungs. Strikingly, to our surprise, we found that in an intranasal murine challenge model, LPaV elicited cross-species protection against both B. bronchiseptica and Bordetella pertussis. Our data suggest the presence of immunogenic protective components other than those included in the pertussis vaccine. Combined with the whole-genome sequences of many Bordetella spp. that are available, the results of this study should serve as a platform for strategic development of the next generation of acellular pertussis vaccines.

Utilisation des bactéries lactiques comme vecteurs vaccinaux

Aujourd’hui, nous disposons de données suffisantes qui confortent l’intérêt d’utiliser des bactéries lactiques (BL), notamment des souches des lactocoques et lactobacilles, pour le développement de nouvelles stratégies de vaccination mucosale. Les BL sont des bactéries à Gram positif utilisées depuis des millénaires dans la production d’aliments fermentés. Elles sont donc de bonnes candidates pour le développement de nouvelles stratégies de vectorisation orale et constituent des alternatives attractives aux stratégies vaccinales basées sur des bactéries pathogènes atténuées dont l’utilisation présente des risques sanitaires. Ce chapitre passe en revue la recherche et les progrès les plus récents dans l’utilisation des BL comme vecteurs de délivrance de protéines d’intérêt médical pour développer de nouveaux vaccins.

Dendritic cell targeting of Bacillus anthracis protective antigen expressed by Lactobacillus acidophilus protects mice from lethal challenge

Efficient vaccines potentiate antibody avidity and increase T cell longevity, which confer protection against microbial lethal challenge. A vaccine strategy was established by using Lactobacillus acidophilus to deliver Bacillus anthracis protective antigen (PA) via specific dendritic cell-targeting peptides to dendritic cells (DCs), which reside in the periphery and mucosal surfaces, thus directing and regulating acquired immunity. The efficiency of oral delivery of L. acidophilus expressing a PA-DCpep fusion was evaluated in mice challenged with lethal B. anthracis Sterne. Vaccination with L. acidophilus expressing PA-DCpep induced robust protective immunity against B. anthracis Sterne compared with mice vaccinated with L. acidophilus expressing PA-control peptide or an empty vector. Additionally, serum anti-PA titers, neutralizing PA antibodies, and the levels of IgA-expressing cells were all comparable with the historical recombinant PA plus aluminum hydroxide vaccine administered s.c. Collectively, development of this strategy for oral delivery of DC-targeted antigens provides a safe and protective vaccine via a bacterial adjuvant that may potentiate mucosal immune responses against deadly pathogens.

Development of Mucosal Vaccines Based on Lactic Acid Bacteria

Today, sufficient data are available to support the use of lactic acid bacteria (LAB), notably lactococci and lactobacilli, as delivery vehicles for the development of new mucosal vaccines. These non-pathogenic Gram-positive bacteria have been safely consumed by humans for centuries in fermented foods. They thus constitute an attractive alternative to the attenuated pathogens (most popular live vectors actually studied) which could recover their pathogenic potential and are thus not totally safe for use in humans. This chapter reviews the current research and advances in the use of LAB as live delivery vectors of proteins of interest for the development of new safe mucosal vaccines. The use of LAB as DNA vaccine vehicles to deliver DNA directly to antigen-presenting cells of the immune system is also discussed.

Active and passive immunizations with Bordetella colonization factor A protect mice against respiratory challenge with Bordetella bronchiseptica

Bordetella colonization factor A (BcfA) is an outer membrane immunogenic protein, which is critical for efficient colonization of the murine respiratory tract. These properties of BcfA prompted us to examine its utility in inducing a protective immune response against Bordetella bronchiseptica in a mouse model of intranasal infection. Mice vaccinated with BcfA demonstrated reduced pathology in the lungs and harbored lower bacterial burdens in the respiratory tract. Immunization with BcfA led to the generation of BcfA-specific antibodies in both the sera and lungs, and passive immunization led to the reduction of B. bronchiseptica in the tracheas and lungs. These results suggest that protection after immunization with BcfA is mediated in part by antibodies against BcfA. To further investigate the mechanism of BcfA-induced immune clearance, we examined the role of neutrophils and macrophages. Our results demonstrate that neutrophils are critical for anti-BcfA antibody-mediated clearance and that opsonization with anti-BcfA serum enhances phagocytosis of B. bronchiseptica by murine macrophages. We show that immunization with BcfA results in the production of gamma interferon and subclasses of immunoglobulin G antibodies that are consistent with the induction of a Th1-type immune response. In combination, our findings suggest that the mechanism of BcfA-mediated immunity involves humoral and cellular responses. Expression of BcfA is conserved among multiple clinical isolates of B. bronchiseptica. Our results demonstrate the striking protective efficacy of BcfA-mediated immunization, thereby highlighting its utility as a potential vaccine candidate. These results also provide a model for the development of cell-free vaccines against B. bronchiseptica.

Immunogenicity of recombinant protective antigen and efficacy against intranasal challenge with Bordetella bronchiseptica

Bordetella bronchiseptica is a Gram-negative respiratory pathogen that causes substantial disease in a variety of animals. Filamentous hemagglutinin (FHA) and pertactin are important attachment factors and protective immunogens, which serve as protective antigens in several animal models of infection with B. bronchiseptica. Here, we showed the efficacy of subcutaneous immunization of mice with a recombinant protein rF1P2, which consisted of the important immunodominant protective type I domain (F1) of FHA and the highly immunogenic region II domain (P2) of pertactin. Groups of mice tested, when challenged with different strains of B. bronchiseptica were fully protected, with long-lasting immunity to lethal B.bronchiseptica challenge, whereas mice immunized with Freund's adjuvant alone or PBS were not. In rF1P2-immunized mice, specific antibodies lasted for more than 120 days, and the IgG1/IgG2a ratio remained at a constant level till the end of the study. This suggests that rF1P2-induced a long-lasting balanced humoral immune responses and immunological memory in mice. rF1P2-specific antisera inhibited hemagglutination associated with full-length mature FHA. Furthermore, passive antiserum transfer from immunized animals completely protected naive mice from subsequent B. bronchiseptica challenge. These data may have implications for the development of safe and efficacious subunit vaccines for the prevention of bordetellosis, and may contribute to future acellular whooping cough vaccines.

Targeting mucosal dendritic cells with microbial antigens from probiotic lactic acid bacteria

The use of vaccines against infectious microbes has been critical to the advancement of medicine. Vaccine strategies combined with, or without, adjuvants have been established to eradicate various bacterial and viral pathogens. A new generation of vaccines is being developed using specific strains of Gram-positive, lactic acid bacteria and, notably, some probiotic lactobacilli. These bacteria have been safely consumed by humans for centuries in fermented foods. Thus, they can be orally administered, are well tolerated by recipients and could be easily and economically provided to large populations. In this overview, we focus on mucosal immunity and how its cellular component(s), particularly dendritic cells, can be specifically targeted to deliver immunogenic subunits, such as the protective antigen from Bacillus anthracis (the causative agent of anthrax). An antigen-specific immune response can be elicited using specific strains of Lactobacillus acidophilus expressing the protective antigen. A mucosal, dendritic cell-targeted approach increases the bioavailability of an immunogen of interest when delivered orally by L. acidophilus. This provides an efficiently elegant natural strategy and serves a dual function as an immune-stimulating adjuvant in vivo.

Current prophylactic and therapeutic uses of a recombinant Lactococcus lactis strain secreting biologically active interleukin-12

The noninvasive and food-grade Gram-positive bacterium Lactococcus lactis is well adapted to deliver medical proteins to the mucosal immune system. In the last decade, the potential of live recombinant lactococci to deliver such proteins to the mucosal immune system has been investigated. This approach offers several advantages over the traditional systemic injection, such as easy administration and the ability to elicit both systemic and mucosal immune responses. This paper reviews the current research and advances made with recombinant L. lactis as live vector for the in situ delivery of biologically active interleukin-12, a potent pleiotropic cytokine with adjuvant properties when co-delivered with vaccinal antigens, at mucosal surfaces. Three well-illustrated examples demonstrate the high potential of interleukin-12-secreting lactococci strains for future prophylactic and therapeutic uses.

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.

Engineering bacterial vectors for delivery of genes and proteins to antigen-presenting cells

Bacterial vectors offer a biological route to gene and protein delivery with this article featuring delivery to antigen-presenting cells (APCs). Primarily in the context of immune stimulation against infectious disease or cancer, the goal of bacterially mediated delivery is to overcome the hurdles to effective macromolecule delivery. This review will present several bacterial vectors as macromolecule (protein or gene) delivery devices with both innate and acquirable (or engineered) biological features to facilitate delivery to APCs. The review will also present topics related to large-scale manufacture, storage, and distribution that must be considered if the bacterial delivery devices are ever to be used in a global market.

Live bacterial vaccines--a review and identification of potential hazards

The use of live bacteria to induce an immune response to itself or to a carried vaccine component is an attractive vaccine strategy. Advantages of live bacterial vaccines include their mimicry of a natural infection, intrinsic adjuvant properties and their possibility to be administered orally. Derivatives of pathogenic and non-pathogenic food related bacteria are currently being evaluated as live vaccines. However, pathogenic bacteria demands for attenuation to weaken its virulence. The use of bacteria as vaccine delivery vehicles implies construction of recombinant strains that contain the gene cassette encoding the antigen. With the increased knowledge of mucosal immunity and the availability of genetic tools for heterologous gene expression the concept of live vaccine vehicles gains renewed interest. However, administration of live bacterial vaccines poses some risks. In addition, vaccination using recombinant bacteria results in the release of live recombinant organisms into nature. This places these vaccines in the debate on application of genetically modified organisms. In this review we give an overview of live bacterial vaccines on the market and describe the development of new live vaccines with a focus on attenuated bacteria and food-related lactic acid bacteria. Furthermore, we outline the safety concerns and identify the hazards associated with live bacterial vaccines and try to give some suggestions of what to consider during their development.

Complete structures of Bordetella bronchiseptica and Bordetella parapertussis lipopolysaccharides

The structures of the lipopolysaccharide (LPS) core and O antigen of Bordetella bronchiseptica and Bordetella parapertussis are known, but how these two regions are linked to each other had not been determined. We have studied LPS from several strains of these microorganisms to determine the complete carbohydrate structure of the LPS. LPS was analyzed using different chemical degradations, NMR spectroscopy, and mass spectrometry. This identified a novel pentasaccharide fragment that links the O chain to the core in all the LPS studied. In addition, although the O chain of these bacteria was reported as a homopolymer of 1,4-linked 2,3-diacetamido-2,3-dideoxy-alpha-galacturonic acid, we discovered that the polymer contains several amidated uronic acids, the number of which varies between strains. These new data describe the complete structure of the LPS carbohydrate backbone for both Bordetella species and help to explain the complex genetics of LPS biosynthesis in these bacteria.

Infection of newborn piglets with Bordetella pertussis: a new model for pertussis

Bordetella pertussis is the causative agent of pertussis or whooping cough. This bacterium is a human pathogen that under experimental conditions also infects selected rodents and primates. Here, we show for the first time that newborn piglets can be infected with B. pertussis when it is delivered intrapulmonarily. Infected piglets displayed fever and respiratory symptoms, such as nasal discharge, nonparoxysmal coughing, and breathing difficulties. Eventually, all infected animals developed severe bronchopneumonia, which in some cases was combined with a fibrinous pleuritits. Immunohistochemical staining revealed the presence of large numbers of B. pertussis cells within airways, adhering to the epithelial lining or phagocytosed by macrophages and neutrophils. Viable bacteria were reisolated from bronchoalveolar lavages and lung lesions for more than 10 days postinfection. The systemic presence of pertussis toxin was shown by hypoglycemia, lymphocytosis, and induction of a clustered pattern of CHO cells by serum and bronchoalveolar lavage samples. Thus, a large-animal model for pertussis was developed, which should complement existing rodent models for identifying the immune responses relevant to the design of new vaccines. In particular, this model should help researchers analyze the roles of both maternal and mucosal immunity in disease protection against pertussis and should ultimately assist in the design of new vaccines for early life protection.

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.