Identification of a 68-kilodalton outer membrane protein as the major protective antigen of Bordetella bronchiseptica by using specific-pathogen-free piglets

Bordetella bronchiseptica and Bordetella pertussis: Similarities and Differences in Infection, Immuno-Modulation, and Vaccine Considerations

Bordetella pertussis and Bordetella bronchiseptica belong to the genus Bordetella, which comprises 14 other species. B. pertussis is responsible for whooping cough in humans, a severe infection in children and less severe or chronic in adults. These infections are restricted to humans and currently increasing worldwide. B. bronchiseptica is involved in diverse respiratory infections in a wide range of mammals. For instance, the canine infectious respiratory disease complex (CIRDC), characterized by a chronic cough in dogs. At the same time, it is increasingly implicated in human infections, while remaining an important pathogen in the veterinary field. Both Bordetella can evade and modulate host immune responses to support their persistence, although it is more pronounced in B. bronchiseptica infection. The protective immune responses elicited by both pathogens are comparable, while there are important characteristics in the mechanisms that differ. However, B. pertussis pathogenesis is more difficult to decipher in animal models than those of B. bronchiseptica because of its restriction to humans. Nevertheless, the licensed vaccines for each Bordetella are different in terms of formulation, route of administration and immune responses induced, with no known cross-reaction between them. Moreover, the target of the mucosal tissues and the induction of long-lasting cellular and humoral responses are required to control and eliminate Bordetella. In addition, the interaction between both veterinary and human fields are essential for the control of this genus, by preventing the infections in animals and the subsequent zoonotic transmission to humans.

Identification of linear B epitopes of pertactin of Bordetella pertussis induced by immunization with whole and acellular vaccine

Pertussis is a serious infectious disease of the respiratory tract caused by the gram-negative bacteria Bordetella pertussis. There has been a reemergence of this disease within the population of several countries that have well established vaccination programs. Analyzes of clinical isolates suggest an antigenic divergence between the vaccine-based strains to the circulating strains. Although antibodies against P.69 are involved in the observed protective immunity, the sequences recognized as antigenic determinants in P.133, the precursor for P.69, P.3.4 and P.30, have not be determined. Here, the precise mapping of linear B-cell epitopes within the predicted P.133 pertactin sequences was accomplished using the SPOT-synthesis of peptide arrays onto cellulose membranes and screening with murine sera generated by vaccination with either the Pertussis cellular (miPc) or Pertussis acellular (miPa) vaccine. A total of 23 major epitopes were identified by sera from miPc vaccinated mice, while thirteen were identified by sera from miPa vaccinated mice. Of these epitopes, 12 epitopes were specifically identified by antibodies produced in response to the miPc vaccine and two were specific to the miPa vaccine. These epitopes were distributed throughout the pertactin sequence but a significant number were concentrated to the P.30 Prn segment. An analysis of the epitope correlation homologies indicated that the variations from the observed mutations in pertactin would not constitute a problem using these vaccines. In addition, the mapping of epitopes demonstrated a higher number of linear B-cell epitopes immunized with the Pc vaccine than the Pa vaccine.

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.

Pertactin is required for Bordetella species to resist neutrophil-mediated clearance

Pertactin (PRN) is an autotransporter protein produced by all members of the Bordetella bronchiseptica cluster, which includes B. pertussis, B. parapertussis, and B. bronchiseptica. It is a primary component of acellular pertussis vaccines, and anti-PRN antibody titers correlate with protection. In vitro studies have suggested that PRN functions as an adhesin and that an RGD motif located in the center of the passenger domain is important for this function. Two regions of PRN that contain sequence repeats (region 1 [R1] and R2) show polymorphisms among strains and have been implicated in vaccine-driven evolution. We investigated the role of PRN in pathogenesis using B. bronchiseptica and natural-host animal models. A Deltaprn mutant did not differ from wild-type B. bronchiseptica in its ability to adhere to epithelial and macrophage-like cells in vitro or to establish respiratory infection in rats but was cleared much faster than wild-type bacteria in a mouse lung inflammation model. Unlike wild-type B. bronchiseptica, the Deltaprn mutant was unable to cause a lethal infection in SCID-Bg mice, but, like wild-type bacteria, it was lethal for neutropenic mice. These results suggest that PRN plays a critical role in allowing Bordetella to resist neutrophil-mediated clearance. Mutants producing PRN proteins in which the RGD motif was replaced with RGE or in which R1 and R2 were deleted were indistinguishable from wild-type bacteria in all assays, suggesting that these sequences do not contribute to PRN function.

Contribution of Bordetella bronchiseptica filamentous hemagglutinin and pertactin to respiratory disease in swine

Bordetella bronchiseptica is pervasive in swine populations and plays multiple roles in respiratory disease. Most studies addressing virulence factors of B. bronchiseptica are based on isolates derived from hosts other than pigs. Two well-studied virulence factors implicated in the adhesion process are filamentous hemagglutinin (FHA) and pertactin (PRN). We hypothesized that both FHA and PRN would serve critical roles in the adhesion process and be necessary for colonization of the swine respiratory tract. To investigate the role of FHA and PRN in Bordetella pathogenesis in swine, we constructed mutants containing an in-frame deletion of the FHA or the PRN structural gene in a virulent B. bronchiseptica swine isolate. Both mutants were compared to the wild-type swine isolate for their ability to colonize and cause disease in swine. Colonization of the FHA mutant was lower than that of the wild type at all respiratory tract sites and time points examined and caused limited to no disease. In contrast, the PRN mutant caused similar disease severity relative to the wild type; however, colonization of the PRN mutant was reduced relative to the wild type during early and late infection and induced higher anti-Bordetella antibody titers. Together, our results indicate that despite inducing different pathologies and antibody responses, both FHA and PRN are necessary for optimal colonization of the swine respiratory tract.

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.

Subcutaneous vaccination with attenuated Salmonella enterica serovar Choleraesuis C500 expressing recombinant filamentous hemagglutinin and pertactin antigens protects mice against fatal infections with both S. enterica serovar Choleraesuis and Bordetella bronchiseptica

Salmonella enterica serovar Choleraesuis strain C500 is a live, attenuated vaccine that has been used in China for over 40 years to prevent piglet paratyphoid. We compared the protective efficacies of subcutaneous (s.c.) and oral vaccination of BALB/c mice with C500 expressing the recombinant filamentous hemagglutinin type I domain and pertactin region 2 domain antigen (rF1P2) of Bordetella bronchiseptica. Protective efficacy against both S. enterica serovar Choleraesuis infection in an oral fatal challenge model and B. bronchiseptica infection in a model of fatal acute pneumonia was evaluated. Both the s.c. and oral vaccines conferred complete protection against fatal infection with the virulent parent S. enterica serovar Choleraesuis strain (C78-1). All 20 mice vaccinated s.c. survived intranasal challenge with four times the 50% lethal dose of virulent B. bronchiseptica (HH0809) compared with 4 of 20 vector-treated controls and 1 of 18 phosphate-buffered saline-treated controls that survived, but no significant protection against HH0809 was observed in orally vaccinated animals. Both the s.c. and oral vaccines elicited rF1P2-specific serum immunoglobulin G (IgG) and IgA antibodies. However, lung homogenates from s.c. vaccinated animals had detectably high levels of rF1P2-specific IgG and IgA; a much lower level of rF1P2-specific IgG was detected in samples from orally vaccinated mice, and the latter showed no evidence of local IgA. Furthermore, a more abundant and longer persistence of vaccine organisms was observed in the lungs of mice immunized s.c. than in those of mice immunized orally. Our results suggest that s.c. rather than oral vaccination is more efficacious in protecting mice from fatal challenge with B. bronchiseptica.

The case for maternal vaccination against pertussis

Despite high vaccine coverage, the incidence of pertussis is increasing in a number of countries. Particularly alarming is the increase of pertussis in infants too young to be (fully) vaccinated, because the highest morbidity and mortality is observed in this category. Maternal vaccination offers the possibility to protect infants from birth until immunity is induced by active vaccination, and has been shown to be effective and safe for tetanus over long periods of time. Maternal vaccination studies with whole-cell pertussis vaccines have not shown serious adverse effects in mother and child. In one study, protection of newborn babies was found. Additional support for the efficacy of maternal vaccination comes from studies showing that transfer of antibodies confers protection against pertussis. Maternal vaccination might be an effective way to decrease morbidity and mortality caused by pertussis in newborn babies.

The role of peptide loops of the Bordetella pertussis protein P.69 pertactin in antibody recognition

Bordetella pertussis, the etiological agent of whooping cough, is re-emerging in several countries with a traditionally high vaccine uptake. In these B. pertussis strains, polymorphisms were found in several proteins, including P.69 pertactin (P.69 Prn). P.69 Prn, an adhesin, contains two variable regions which are composed of repeats, one of which flanks the receptor binding site. Antibody titers against P.69 Prn correlate with protection and P.69 Prn is one of the components of acellular pertussis vaccines. Nevertheless, little is known about the structure and location of P.69 Prn epitopes. We used a three pronged approach to identify discontinuous epitopes that are recognized by mouse monoclonal antibodies, i.e. site-directed mutagenesis, deletion mapping and competition assays. Site-directed mutagenesis was focused on regions of P.69 Prn predicted to form loops according to the crystal structure. In this report we describe the location of several discontinuous epitopes that are also recognized by human antibodies. Our results reveal an important role of the N-terminus in immune recognition. We provide data for an indirect role of loops in immune evasion by masking of epitopes. We propose that the repeat regions have evolved to allow rapid antigenic variation to deflect the immune response from the functional domain of P.69 Prn. The results presented here provide a better understanding of the structure and function of variable loops and their role in the persistence of pathogens in immunologically primed populations.

Adaptive evolution of the Bordetella autotransporter pertactin

The virulence factor pertactin is expressed by the closely related pathogens Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica. Pertactin is an autotransporter involved in adherence of Bordetella species to the lung epithelium of mammalian hosts, and it is an important component of most current acellular pertussis vaccines. These three species produce immunologically distinct pertactin molecules, resulting in a lack of cross-protection against B. parapertussis and probably also against B. bronchiseptica. Variation in pertactin is not only inter-specific, but also occurs between isolates from the same species. Knowledge about codons that are under positive selection could facilitate the development of more broadly protective vaccines. Using different nucleotide substitution models, pertactin genes from B. bronchiseptica, B. parapertussis and B. pertussis were compared, and positively selected codons were identified using an empirical Bayesian approach. This approach yielded 15 codons predicted to be under diversifying selection pressure. These results were interpreted in an immunological context and may help in improving future pertussis vaccines.

PFGE and pertactin gene sequencing suggest limited genetic variability within the Finnish Bordetella parapertussis population

The outer-membrane protein pertactin (Prn) of Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica is believed to function as an adhesin and is an important immunogen. The emergence of B. pertussis and B. bronchiseptica Prn variants has been reported. The aim of this study was to determine whether similar variation is found in B. parapertussis Prn and to characterize Finnish clinical B. parapertussis isolates that were collected in 1982-2000. Of 76 B. parapertussis isolates studied, seven (9 %) were found to have silent and non-silent nucleotide changes. In addition, one (1 %) had eight PQP repeats instead of nine. Three closely related B. parapertussis XbaI PFGE patterns were found. Genetic variation of B. parapertussis was found to be very limited, suggesting that B. parapertussis is a stable organism that is well-adapted to its own ecological niche.

Novel genetic and phenotypic heterogeneity in Bordetella bronchiseptica pertactin

The Bordetella bronchiseptica outer membrane protein pertactin is believed to function as an adhesin and is an important protective immunogen. Previous sequence analysis of the pertactin gene identified two regions predicted to encode amino acid repeat motifs. Recent studies have documented DNA sequence heterogeneity in both regions. The present study describes additional variants in these regions, which form the basis for six novel pertactin types. Immunoblotting demonstrated phenotypic heterogeneity in pertactin consistent with the predicted combined sizes of the repeat regions. A revised system for classifying B. bronchiseptica pertactin variants is proposed.

Polymorphism of repeated regions of pertactin in Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica

Pertactin is an outer membrane protein expressed by Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica that induces protective immunity to Bordetella infections. The immunodominant and immunoprotective epitopes of pertactin include two repeated regions, I and II. Comparison of these two repeated regions showed that B. parapertussis pertactin is invariant, whereas B. pertussis pertactin varies mostly in region I and B. bronchiseptica pertactin varies in both repeated regions I and II, but mostly in region II. These differences may result from specific characteristics of these Bordetella species.

Polymorphism in the Bordetella pertussis virulence factors P.69/pertactin and pertussis toxin in The Netherlands: temporal trends and evidence for vaccine-driven evolution

The Bordetella pertussis proteins P.69 (also designated pertactin) and pertussis toxin are important virulence factors and have been shown to confer protective immunity in animals and humans. Both proteins are used in the new generation of acellular pertussis vaccines (ACVs), and it is therefore important to study the degree of antigenic variation in these proteins. Sequence analysis of the genes for P.69 and the pertussis toxin S1 subunit, using strains collected from Dutch patients in the period 1949 to 1996, revealed three P.69 and three S1 variants which show differences in amino acid sequence. Polymorphism in P.69 was confined to a region comprised of repeats and located proximal to the RGD motif involved in adherence to host tissues. Variation in S1 was observed in two regions previously identified as T-cell epitopes. P.69 and S1 variants, identical to those included in the Dutch whole-cell pertussis vaccine (WCV), were found in 100% of the strains from the 1950s, the period when the WCV was introduced in The Netherlands. However, nonvaccine types of P.69 and S1 gradually replaced the vaccine types in later years and were found in approximately 90% strains from 1990 to 1996. These results suggest that vaccination has selected for strains which are antigenically distinct from vaccine strains. Analysis of strains from vaccinated and nonvaccinated individuals indicated that the WCV protects better against strains with the vaccine type P.69 than against strains with non-vaccine types (P = 0.024). ACVs contain P.69 and S1 types which are found in only 10% of recent Dutch B. pertussis isolates, implying that they do not have an optimal composition. Our findings cast a new light on the reemergence of pertussis in highly vaccinated populations and may have major implications for the long-term efficacy of both WCVs and ACVs.

Safety and immunogenicity of two acellular pertussis vaccines with different pertussis toxoid and filamentous hemagglutinin content in infants 2-6 months old

The optimal composition and antigen content of acellular pertussis vaccines is not known. Two vaccines with different quantities of pertussis toxoid (10 and 20 micrograms) and filamentous hemagglutinin (5 and 20 micrograms) and identical 69 kD protein (3 micrograms) and fimbriae 2 and 3 (5 micrograms) combined with diphtheria and tetanus toxoids were compared in a randomized, double-blind study in 2,050 infants undergoing their primary immunization series at 8 centers in the US and Canada. A 6:1 increased antigen to lower antigen allocation was used; 96% of infants received 3 doses and completed the study. A 'clinically significant' local reaction was reported in 3-6% of participants after each dose. Erythema was the most common reaction occurring in 3-5% of infants after the second or third dose. A clinically significant systemic adverse reaction was reported in 28-34% of vaccinees (or vaccinated children) after each dose; fever (7-18%) and fussiness (12-17%) were most common. There were no differences in adverse events between the 2 vaccine formulations. Antibody responses were measured in 292 infants at 1 center. At 7 months, geometric mean anti-filamentous hemagglutinin antibody titers were higher in recipients of the higher antigen content vaccine (p < 0.001) whereas recipients of the lower antigen content formulation had higher anti-fimbriae antibody (p < 0.001) and agglutinin titers (p < 0.05). No differences were detected in anti-pertussis toxin or other antibody responses between the formulations. We conclude that increasing the antigen content of the acellular pertussis vaccine had a variable effect on antibody response but was not associated with increased adverse reactions.

A randomized controlled trial of two acellular pertussis-diphtheria-tetanus vaccines in primary immunization in Ghana: antibody responses and adverse reactions

Two acellular pertussis vaccines combined with diphtheria and tetanus toxoids (APDT vaccines) were compared with a whole cell PDT (WCPDT) vaccine in primary immunization in Ghana. One is a liquid vaccine which is used for general immunization in Japan and the other is a freeze-dried vaccine newly developed as a heat-stable vaccine. Eighty-nine infants were recruited in the study. Sixty-eight who completed three doses of the immunization were assessed for immunological responses. Twenty-one dropped out because of sickness or moving from the study area. A total of 242 vaccinations in 89 infants were followed up for adverse reactions. Geometric mean titres (GMTs) to filamentous haemagglutinin in the two APDT vaccinees were significantly higher than in the WCPDT recipients. GMTs to pertussis toxin, diphtheria and tetanus toxoids were not significantly different among the three groups. Seropositive rates to pertussis antigens, tetanus and diphtheria toxoids were 94.4 to 100% in the two APDT vaccines. Systemic reactions within 7 days of inoculation were similarly low in the three groups, but significantly fewer infants had local reactions after either of the two APDT vaccines than after the WCPDT vaccine.

Flagellin gene transcription in Bordetella bronchiseptica is regulated by the BvgAS virulence control system

The products of the bvgAS locus activate expression of a majority of the known Bordetella virulence factors but also exert negative control over a class of genes called vrg genes (bvg-repressed genes). BvgAS negatively controls the production of flagella and the phenotype of motility in Bordetella bronchiseptica. In this study flaA, the flagellin gene, was cloned and characterized to facilitate studies of this negative control pathway. An internal flaA probe detected hybridizing sequences on genomic Southern blots of Bordetella pertussis, Bordetella parapertussis, and Bordetella avium, although B. pertussis and B. parapertussis are nonmotile. FlaA is similar to the FliC flagellins of Salmonella typhimurium and Escherichia coli, and flaA complemented an E. coli flagellin mutant. Insertional inactivation of the chromosomal flaA locus eliminated motility, which was restored by complementation with the wild-type locus. Analysis of flaA mRNA production by Northern (RNA) blotting and primer extension indicated that negative regulation by BvgAS occurs at the level of transcription. The transcriptional start site of flaA mapped near a consensus site for the alternative sigma factor, sigma F, encoded by fliA in E. coli and S. typhimurium. Consistent with a role for a fliA analog in B. bronchiseptica, transcriptional activation of a flaA-lacZ fusion in E. coli required fliA and a flaA-linked locus designated frl.frl also efficiently complemented mutations in the flagellar master regulatory locus, flhDC, of E. coli. Our analysis of the motility phenotype of B. bronchiseptica suggests that the Bordetella virulence control system mediates transcriptional control of flaA through a regulatory hierarchy that includes the frl locus and an alternative sigma factor.

Derivation of a physical map of the chromosome of Bordetella pertussis Tohama I

We have used pulsed-field gel electrophoresis to derive a restriction map of the chromosome of Bordetella pertussis for the enzymes XbaI, SpeI, PacI, and PmeI, which cleave 25, 16, 2, and 1 times, respectively. The apparent size of the genome is 3,750 kb. The positions of genes for major virulence determinants in the vir regulon and of some housekeeping genes were determined. Apart from the previously known linkage of the vir and fha loci, no significant linkage of virulence genes was demonstrated.

The bvgAS locus negatively controls motility and synthesis of flagella in Bordetella bronchiseptica

The products of the bvgAS locus coordinately regulate the expression of Bordetella virulence factors in response to environmental conditions. We have identified a phenotype in Bordetella bronchiseptica that is negatively controlled by bvg. Environmental signals which decrease (modulate) the expression of bvg-activated genes lead to flagellum production and motility in B. bronchiseptica. Wild-type (Bvg+) strains are motile and produce peritrichous flagella only in the presence of modulating signals, whereas Bvg- (delta bvgAS or delta bvgS) strains are motile in the absence of modulators. The bvgS-C3 mutation, which confers signal insensitivity and constitutive activation of positively controlled loci, eliminates the induction of motility and production of flagellar organelles. The response to environmental signals is conserved in a diverse set of clinical isolates of both B. bronchiseptica and B. avium, another motile Bordetella species; however, nicotinic acid induced motility only in B. bronchiseptica. Purification of flagellar filaments from B. bronchiseptica strains by differential centrifugation followed by CsCl equilibrium density gradient centrifugation revealed two classes of flagellins of Mr 35,000 and 40,000. A survey of clinical isolates identified only these two flagellin isotypes, and coexpression of the two forms was not detected in any strain. All B. avium strains tested expressed a 42,000-Mr flagellin. Amino acid sequence analysis of the two B. bronchiseptica flagellins revealed 100% identity in the N-terminal region and 80% identity with Salmonella typhimurium flagellin. Monoclonal antibody 15D8, which recognizes a conserved epitope in flagellins in members of the family Enterobacteriaceae, cross-reacted with flagellins from B. bronchiseptica and B. avium. Our results highlight the biphasic nature of the B. bronchiseptica bvg regulon and provide a preliminary characterization of the Bvg-regulated motility phenotype.

Recombinant P.69/pertactin: immunogenicity and protection of mice against Bordetella pertussis infection

The immunogenicity of recombinant (r-) pertactin was examined. Parenteral immunization of mice with natural or r-pertactin produced a similar increase in serum anti-pertactin antibodies and a decrease in Bordetella pertussis lung counts following aerosol challenge. Study of the kinetics of B. pertussis growth in the respiratory tract of immunized and control mice revealed that immunization with r-pertactin halted the multiplication of B. pertussis in the lungs and facilitated the early onset of bacterial clearance. In the trachea, bacterial numbers declined sharply in immunized animals during the first 3 days after challenge but thereafter B. pertussis numbers remained fairly constant throughout the rest of the experiment. Very low doses (0.1 micrograms) of r-pertactin were immunogenic and protective but only if the antigen was absorbed to alhydrogel. In vitro proliferation assays with lymphocytes from mice primed with either natural or r-pertactin indicated that the major T-cell epitopes of pertactin are conserved in the recombinant protein.

Comparison of acellular and whole-cell pertussis-component diphtheria-tetanus-pertussis vaccines in infants. The APDT Vaccine Study Group

In a multicenter, double-blind, randomized, longitudinal study, 252 children received licensed Lederle diphtheria-tetanus toxoids and pertussis vaccine adsorbed (DTP) at 2, 4, and 6 months of age, and 245 children received a DTP vaccine with the Lederle/Takeda acellular pertussis component (APDT) at the same ages. Both groups of children received APDT vaccine at 18 months of age. After each of the first three immunizations, APDT vaccine recipients had fewer local and systemic reactions than did DTP vaccinees. Reactions after the 18-month APDT vaccination were minimal in severity regardless of the vaccine previously received. Antibody responses to lymphocytosis-promoting factor and agglutinogens were more pronounced in DTP recipients; however, APDT recipients had a better serologic response to filamentous hemagglutinin, and responses to the 69K protein were equivalent. This APDT vaccine produces fewer reactions than the standard whole-cell DTP vaccine. The protective significance of the serologic responses to the APDT vaccine is unknown, but the greater response to filamentous hemagglutinin and equivalent response to the 69K protein compared with those to DTP vaccine seem promising.

Construction and characterization of Bordetella pertussis mutants lacking the vir-regulated P.69 outer membrane protein

The Bordetella pertussis P.69 protein is an immunogen with vaccine potential. The role of this protein in pathogenesis is unclear; it has been associated with the toxic adenylate cyclase and adhesion to eukaryotic cells. For further analysis of the role of P.69 in the biology of B. pertussis, we have constructed strains which specifically lack P.69. The cloned P.69 (prn) gene of B. pertussis was insertionally inactivated with a kanamycin-resistance cassette. This inactivated gene was used to construct P.69- mutants of B. pertussis by allelic exchange using plasmid pRTP1. B. pertussis P.69- strains produced normal levels of other vir-regulated factors, including adenylate cyclase. The serotype of B. pertussis, determined by Eldering and Preston typing sera and monoclonal antibodies, was also unaffected by the presence or absence of P.69. The ability of a prn mutant to adhere to and invade HEp2 cells was not significantly different from that of its parent strain. A strain containing a mutation in fhaB was significantly less adhesive and invasive than its parent, and a prn fhaB double mutant exhibited an even greater reduction in adhesiveness and invasiveness down to levels comparable with a Vir- strain. However, strains harbouring mutations in FHA and/or P.69 were able to colonize or multiply in the murine respiratory tract, although a Vir- strain was unable to survive and proliferate in the same infection model.

P.70 pertactin, an outer-membrane protein from Bordetella parapertussis: cloning, nucleotide sequence and surface expression in Escherichia coli

The gene prn encoding the outer-membrane protein P.70 (pertactin) from Bordetella parapertussis has been cloned in Escherichia coli and its DNA sequence determined. Analysis of the DNA sequence reveals that the gene has an open reading frame comprising 922 amino acids capable of encoding a protein with a molecular weight of 95,177 (P.95). In vivo processing of this precursor yields a protein with an estimated Mr of 70 kDa (P.70) which is located on the surface of B. parapertussis. Homology between the prn gene from B. parapertussis and that from Bordetella pertussis is 91.3%. The homology is 93% when the protein sequence of P.95 is aligned with that of P.93 from B. pertussis. The major differences between the P.70 pertactin from B. parapertussis and the P.69 pertactin from B. pertussis occur in the number of reiterated units within the repeat motifs found in both proteins; the sequence Gly-Gly-Xaa-Xaa-Pro is repeated four times in the P.70 pertactin, and five times in the P.69 pertactin, while the sequence Pro-Gln-Pro occurs nine times in P.70 pertactin and five times in P.69 pertactin. Cloning of the gene for P.95 in an E. coli expression vector results in the synthesis of a protein that mimics native gene expression in B. parapertussis, i.e. the P.95 protein is synthesized and subsequently processed to yield the P.70 form of the protein on the surface of the cell.

Protective Surface Antigen P69 of Bordetella pertussis: Its Characterization and Very High Level Expression in Escherichia coli

The surface antigen, P69 of Bordetella pertussis, an N-terminal fragment of the precursor protein, P93, is likely to be an important component of future subunit vaccines against whooping cough. We have expressed several defined N-terminal fragments of P93 in E. coli and compared their electrophoretic mobilities with that of purified P69 from B. pertussis. These experiments show that P69 is considerably smaller than the 69 kD originally estimated from its gel mobility and is probably 60.4 kD in size. Our initial plasmids expressed only very low levels of this antigen. We diagnosed the limiting factor to be a poor ribosome binding site (RBS) by demonstrating a large stimulation of expression on a two-cistron plasmid. The limitation of expression could be completely overcome by only two base changes close to the initiation codon, resulting in a further increase in expression of P69 at levels to 30-40% total cell protein. Although the protein accumulated as insoluble inclusion bodies, it could be solubilized by guanidinium chloride.