Assessing the In Vivo Effectiveness of Cationic Lipid Nanoparticles with a Triple Adjuvant for Intranasal Vaccination against the Respiratory Pathogen Bordetella pertussis.

Continuous outbreaks of pertussis around the world suggest inadequate immune protection in infants and weakened immune responses induced over time by the acellular pertussis vaccine. Vaccine adjuvants provide a means to improve vaccine immunogenicity and support long-term adaptive immunity against pertussis. An acellular pertussis vaccine was prepared with pertactin, pertussis toxin, and fimbriae 2/3 antigens combined with a triple-adjuvant system consisting of innate defense regulator peptide IDR 1002, a Toll-like receptor-3 agonist poly(I:C), and a polyphosphazene in a fixed combination. The vaccine was delivered intranasally in a cationic lipid nanoparticle formulation fabricated by simple admixture and two schema for addition of antigens (LT-A, antigens associated outside of L-TriAdj, and LAT, antigens associated inside of L-TriAdj) to optimize particle size and cationic surface charge. In the former, antigens were associated with the lipidic formulation of the triple adjuvant by electrostatic attraction. In the latter, the antigens resided in the interior of the lipid nanoparticle. Two dose levels of antigens were used with adjuvant comprised of the triple adjuvant with or without the lipid nanoparticle carrier. Formulation of vaccines with the triple adjuvant stimulated systemic and mucosal immune responses. The lipid nanoparticle vaccines favored a Th1 type of response with higher IgG2a and IgA serum antibody titers particularly for pertussis toxin and pertactin formulated at the 5 µg dose level in the admixed formulation. Additionally, the lipid nanoparticle vaccines resulted in high nasal SIgA antibodies and an early (4 weeks post vaccination) response after a single vaccination dose. The LT-A nanoparticles trended toward higher titers of serum antibodies compared to LAT. The cationic lipid-based vaccine nanoparticles formulated with a triple adjuvant showed encouraging results as a potential formulation for intranasally administered pertussis vaccines.

Designing a New Multi-Epitope Pertussis Vaccine with Highly Population Coverage Based on a Novel Sequence and Structural Filtration Algorithm.

Pertussis vaccine is produced from physicochemically inactivated toxin for many years. Recent advancements in immunoinformatics [N. Tomar and R. K. De, "Immunoinformatics: an integrated scenario," Immunology, vol. 131, no. 2, pp. 153-168, 2010] and structural bioinformatics can provide a new multidisciplinary approach to overcome the concerns including unwanted antibodies and incomplete population coverage. In this study we focused on solving the challenging issues by designing a multi-epitope vaccine (MEV) using rational bioinformatics analyses. The frequencies of All HLA DP, DQ, and DR alleles were evaluated in almost all countries. Strong binder surface epitopes on the pertussis toxin were selected based on our novel filtration strategy. Finally, the population coverage of MEV was determined in the candidate country. Filtration steps yielded 312 strong binder epitopes. Finally, 8 surface strong binder epitopes were selected as candidate epitopes. The population coverage of the MEV in France and the world was 98 and 100 percent, respectively. Our algorithm successfully filtered many unwanted strong binder epitopes. Considering the HLA type of all individuals in a country, we theoretically provided the maximum chance to all humans to be vaccinated efficiently. Application of a MEV would be led to production of highly efficient target specific antibodies, significant reduction of unwanted antibodies, and avoid possible raising of auto-antibodies as well.

Recombinant Production of a Novel Fusion Protein: Listeriolysin O Fragment Fused to S1 Subunit of Pertussis Toxin.

Background: Some resources have suggested that genetically inactivated pertussis toxoid (PTs) bear a more protective effect than chemically inactivated products. This study aimed to produce new version of PT, by cloning an inactive pertussis toxin S1 subunit (PTS1) in a fusion form with N-terminal half of the listeriolysin O (LLO) pore-forming toxin. Methods: Deposited pdb structure file of the PT was used to model an extra disulfide bond. Codon-optimized ORF of the PTS1 was used to make recombinant constructs of PTS1 and LLO-PTS1 in the pPSG-IBA35 vector. The recombinant PTS1 and LLO-PTS1 proteins were expressed in BL21 DE3 and SHuffle T7 strains of E. coli and purified by affinity chromatography. Cytotoxic effects of the recombinant proteins were examined in the MCF-7 cell line. Results: The purity of the products proved to be more than 85%, and the efficiency of the disulfide bond formation in SHuffle T7 strain was higher than BL21 DE3 strain. No cytotoxicity of the recombinant proteins was observed in MCF-7 cells. Soluble recombinant PTS1 and LLO-PTS1 proteins were produced in SHuffle T7 strain of E. coli with high efficiency of disulfide bonds formation. Conclusion: The LLO-PTS1 with corrected disulfide bonds was successfully expressed in E. coli SHuffle T7 strain. Due to the safety for human cells, this chimeric molecule can be an option to prevent pertussis disease if its immunostimulatory effects would be confirmed in the future.

Genetically detoxified pertussis toxin displays near identical structure to its wild-type and exhibits robust immunogenicity.

The mutant gdPT R9K/E129G is a genetically detoxified variant of the pertussis toxin (PTx) and represents an attractive candidate for the development of improved pertussis vaccines. The impact of the mutations on the overall protein structure and its immunogenicity has remained elusive. Here we present the crystal structure of gdPT and show that it is nearly identical to that of PTx. Hydrogen-deuterium exchange mass spectrometry revealed dynamic changes in the catalytic domain that directly impacted NAD+ binding which was confirmed by biolayer interferometry. Distal changes in dynamics were also detected in S2-S5 subunit interactions resulting in tighter packing of B-oligomer corresponding to increased thermal stability. Finally, antigen stimulation of human whole blood, analyzed by a previously unreported mass cytometry assay, indicated broader immunogenicity of gdPT compared to pertussis toxoid. These findings establish a direct link between the conserved structure of gdPT and its ability to generate a robust immune response.

Toward an Alum Free Mono-Component Monovalent Pertussis Vaccine: A Cytokine Response Assay.

BACKGROUND: Current evidence indicates the resurgence of whooping cough despite high coverage of whole-cell (wP) and acellular (aP) pertussis vaccines. OBJECTIVE: To investigate the cytokine response to a genetically inactivated protein containing the S1 subunit of pertussis toxin (PTS1) with and without the Listeriolysin O (LLO-PTS1), in comparison with current wP and aP vaccines in the mice model. METHODS: Thirty-six female NMRI mice aged 8 to 12 weeks (25 ± 5 g) were divided into six groups, including control (n=6) and five treated groups (n=6/each). Treated groups received intraperitoneal injection of recombinant PTS1, recombinant fusion LLO-PTS1, aP, wP, and sham (phosphate-buffered saline), whereas the control group did not receive anything. After 60 days, the serum levels of IFN-γ, IL-4, and IL-17 cytokines were evaluated by ELISA method. RESULTS: Our findings showed LLO-PTS1 significantly increased IL-17 and IL-4 cytokines compared with wP and aP vaccines. IFN-γ failed to increase substantially in the LLO-PTS1 group compared to others, but it was non-inferior to standard vaccines. CONCLUSION: Our alum free mono-component monovalent recombinant fusion protein (LLO-PTS1) could bear the capacity to stimulate the release of IFN-γ similar to wP and aP vaccines in the mouse model. Besides, it showed better results in stimulating the release of IL-17 and IL-4 response. This study can be regarded as a platform for further probes in booster pertussis vaccine development.

Chemical Synthesis and Immunological Evaluation of a Pentasaccharide Bearing Multiple Rare Sugars as a Potential Anti-pertussis Vaccine.

With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qß, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qß-glycan as a new anti-pertussis vaccine.

Collaborative study for the calibration of the replacement International Standard for pertussis toxin for use in histamine sensitisation and CHO cell clustering assays.

Pertussis toxin (PT) in its detoxified form is one of the major protective antigens in vaccines against Bordetella pertussis (whooping cough). Reference preparations of native PT are required for the quality control of pertussis vaccines. Stocks of the first WHO International Standard (IS) for PT (JNIH-5) were low and a replacement was required. One candidate material was donated by a vaccine manufacturer to NIBSC. It was formulated, lyophilised into sealed glass ampoules and coded 15/126. An international collaborative study assessed the suitability of this material to replace JNIH-5. Fourteen laboratories from 12 countries took part in the study. Eleven laboratories performed lethal murine histamine sensitisation assay (HIST), 14 performed Chinese Hamster Ovary (CHO) cell clustering assay. International Units (IU) were assigned to the material using these assays as they were used to assign units to JNIH-5. It was found that, unlike JNIH-5, the activities of 15/126 in HIST and CHO cell assays did not agree and therefore different unitage for each assay was assigned. The preparation 15/126 was established as the Second WHO IS for PT for HIST and CHO cell assays. It was assigned a unitage of 1,881 IU/ampoule in HIST and 680 IU/ampoule in the CHO cell clustering assay.

Human Immune Responses to Pertussis Vaccines.

Pertussis still represents a major cause of morbidity and mortality worldwide. Although vaccination is the most powerful tool in preventing pertussis and despite nearly 70 years of universal childhood vaccination, incidence of the disease has been rising in the last two decades in countries with high vaccination coverage. Two types of vaccines are commercially available against pertussis: whole-cell pertussis vaccines (wPVs) introduced in the 1940s and still in use especially in low and middle-income countries; less reactogenic acellular pertussis vaccines (aPVs), licensed since the mid-1990s.In the last years, studies on pertussis vaccination have highlighted significant gaps and major differences between the two types of vaccines in the induction of protective anti-pertussis immunity in humans. This chapter will discuss the responses of the immune system to wPVs and aPVs, with the aim to enlighten critical points needing further efforts to reach a good level of protection in vaccinated individuals.

Bordetella pertussis antigens encapsulated into N-trimethyl chitosan nanoparticulate systems as a novel intranasal pertussis vaccine.

The mucosal immune system serves as the first line of defense against Bordetella pertussis. Intranasal vaccination, due to its potential to induce systemic and mucosal immune responses, appears to prevent the initial adherence and colonization of the bacteria at the first point of contact. In the present study, two B. pertussis antigens, pertussis Toxoid (PTd) and Filamentous hemagglutinin (FHA), which play a very significant role in virulence and protection against pertussis, were encapsulate into N-trimethyl chitosan (TMC) nanoparticulate systems. After preparation of TMC nanoparticles (NPs), the NPs were characterized and their ability to induce efficient immune responses against B. pertussis was studied in a mouse model. Our findings showed that PTd + FHA-loaded TMC NPs have strong ability to induce IL-4, IL-17, IFN-γ, IgG, and IgA in the mouse model. Results from this study suggest that nasal administration of the PTd + FHA-loaded TMC NPs induced not only a systemic immune response but also a local mucosal response, which may improve the efficacy of pertussis prevention through respiratory tract transmission.

Evaluation of Pertussis Toxin Expression in B2 and THIJS Media.

Whole-cell pertussis vaccine (wP) has been imperative and highly effective in preventing childhood deaths due to pertussis. Pertussis toxin is one of the virulence factors of Bordetella pertussis in all available pertussis vaccines. wP production in Razi Vaccine and Serum Research Institute is according to bioreactor culture of B. pertussis strains in B2 medium. The aim of this study was to evaluate B. pertussis strain 509 PT production in B2 and Thalen-IJssel (THIJS) media by Chinese Hamster Ovary (CHO) cell and enzyme-linked immunosorbent assay methods (ELISA). In the current study, B. pertussis strain 509 was cultured in B2 and THIJS media. Six samples were taken during the log growth phase within 2-3 h intervals (triplicate). The growth rate was calculated using opacity and the quantification of cell-associated and released PT measured by ELISA and CHO cell assays. THIJS medium was significantly showed an increase in the bacterial growth rate. During the first 29 h, bacterial concentrations in B2 and THIJS culture medium were 19 and 29 IOU, respectively. In THIJS medium, greater amount of pertussistoxin production was cell-associated. In B2 medium, maximum cell-associated toxin by ELISA and CHO cell assays were in the ODs of 1.1 and 0.9 and for THIJS medium in the ODs of 1.6 and 1.1, respectively. B. pertussis strain 509 in THIJS medium produced higher cell mass and cell-associated pertussis toxin than that of B2. It can be used for the production of whole-cell vaccine with higher pertussis toxin and accordingly using lower biomass per dose leading to the reduction of vaccine toxicity.

Development of a thermostable spray dried outer membrane vesicle pertussis vaccine for pulmonary immunization.

Worldwide resurgence of whooping cough calls for improved, next-generation pertussis vaccines that induce broad and long-lasting immunity. A mucosal pertussis vaccine based on outer membrane vesicles (omvPV) is a promising candidate. Further, a vaccine that is stable outside the cold chain would be of substantial advantage for worldwide distribution and application. A vaccine formulated as a powder could both stabilize the vaccine as well as make it suitable for pulmonary vaccination. To that end, we developed a spray dried omvPV with improved stability compared to the liquid omvPV formulation. Spray drying did not affect the structural integrity of the omvPV. The antigenicity of Vag8, a major antigen in omvPV was diminished slightly and an altered tryptophan fluorescence indicated some changes in protein structure. However, when administered via the pulmonary route in mice after reconstitution, spray dried omvPV showed comparable immune responses and protection against challenge with live B. pertussis as liquid omvPV. Mucosal IgA and Th17 responses were established in addition to broad systemic IgG and Th1/Th17 responses, indicating the induction of an effective immunity profile. Overall, a spray dried omvPV was developed that maintained effective immunogenic properties and has an improved storage stability.

Reporter cell lines for detection of pertussis toxin in acellular pertussis vaccines as a functional animal-free alternative to the in vivo histamine sensitization test.

Detoxified pertussis toxin (pertussis toxoid) is a major antigen in acellular pertussis vaccines. Testing these vaccines on the presence of residual pertussis toxin (PTx) and reversion to toxicity is performed by the regulatory required in vivo Histamine Sensitization test (HIST). Lack of mechanistic understanding of the HIST, technical handicaps and animal welfare concerns, have promoted the development of alternative methods. As the majority of the cellular effects of PTx depend on its ability to activate intracellular pathways involving cAMP, the in vitro cAMP-PTx assay was developed. Although this assay could be used to detect PTx activity, it lacked sensitivity and robustness for use in a quality control setting. In the present study, novel reporter cell lines (CHO-CRE and A10-CRE) were generated that stably express a reporter construct responsive to changes in intracellular cAMP levels. These reporter cell lines were able to detect PTx in a concentration-dependent manner when combined with fixed amounts of forskolin. The CHO-CRE cell line enabled detection of PTx in the context of a multivalent vaccine containing aP, with a sensitivity equal to the HIST. However, the sensitivity of the A10-CRE cells was insufficient for this purpose. The experiments also suggest that the CHO-CRE reporter cell line might be suitable for assessment of cellular effects of PTd reverted to PTx. The CHO-CRE reporter cell line provides a platform that meets the criteria for specificity and sensitivity and is a promising in vitro model with potential to replace the HIST.

Purification design and practice for pertactin, the third component of acellular pertussis vaccine, from Bordetella pertussis.

Development of acellular pertussis vaccine (aPV) requires purification of several components from Bordetella pertussis. While the components pertussis toxin (PT) and filamentous hemagglutinin (FHA) have been successfully purified, the third component, pertactin, proves to be a difficult target due to its very low concentration. In order to solve its purification problem, we performed the surface potential analysis with GRASP2 program. The results demonstrated that there are two major charge patches, one negative and one positive, which are located separately on this linear protein. For this special feature, we designed a dual ion exchange chromatography strategy including an anionic exchange and a cationic exchange process for separation of pertactin from the heat extract of B. pertussis. The initial anionic exchange chromatography concentrated the product from 1.7% to 14.6%, with recovery of 80%. The second cationic exchange chromatography increased the purity to 33%, with recovery of 83%. The final purification was accomplished by hydrophobic interaction chromatography, yielding a purity of 96%. The total recovery of the three columns was 61%. Characterization of the purified antigen was performed with CD, intrinsic fluorescence, HP-SEC and western-blot, showing that the purified protein kept its natural conformation and immune-reactivity. The rationally designed process proved to be feasible, and it is suitable for large-scale preparation of the third aPV component pertactin.

Effect of different detoxification procedures on the residual pertussis toxin activities in vaccines.

Pertussis toxin (PTx) is a major virulence factor produced by Bordetella pertussis and its detoxified form is one of the major protective antigens in vaccines against whooping cough. Ideally, PTx in the vaccine should be completely detoxified while still preserving immunogenicity. However, this may not always be the case. Due to multilevel reaction mechanisms of chemical detoxification that act on different molecular sites and with different production processes, it is difficult to define a molecular characteristic of a pertussis toxoid. PTx has two functional distinctive domains: the ADP-ribosyltransferase enzymatic subunit S1 (A-protomer) and the host cell binding carbohydrate-binding subunits S2-5 (B-oligomer); and in this study, we investigated the effect of different detoxification processes on these two functional activities of the residual PTx in toxoids and vaccines currently marketed worldwide using a recently developed in vitro biochemical assay system. The patho-physiological activities in these samples were also estimated using the in vivo official histamine sensitisation tests. Different types of vaccines, detoxified by formaldehyde, glutaraldehyde or by both, have different residual functional and individual baseline activities. Of the vaccines tested, PT toxoid detoxified by formaldehyde had the lowest residual PTx ADP-ribosyltransferase activity. The carbohydrate binding results detected by anti-PTx polyclonal (pAb) and anti-PTx subunits monoclonal antibodies (mAb) showed specific binding profiles for toxoids and vaccines produced from different detoxification methods. In addition, we also demonstrated that using pAb or mAb S2/3 as detection antibodies would give a better differential difference between these vaccine lots than using mAbs S1 or S4. In summary, we showed for the first time that by measuring the activities of the two functional domains of PTx, we could characterise pertussis toxoids prepared from different chemical detoxification methods and this study also highlights the potential use of this in vitro biochemical assay system for in-process control.

Multiplex immunoassay for in vitro characterization of acellular pertussis antigens in combination vaccines.

Vaccines characterization is required to ensure physical, chemical, and biological integrity of antigens and adjuvants. Current analytical methods mostly require complete antigen desorption from aluminum-based adjuvants and are not always suitable to distinguish individual antigens in multivalent formulations. Here, Luminex technology is proposed to improve the analytics of vaccine characterization. As proof of concept, TdaP (tetanus, diphtheria and acellular pertussis) combination, adjuvanted with aluminum hydroxide, was chosen as model formulation to quantify and determine the level of adsorption of acellular pertussis (aP) antigens onto adjuvant surface at the same time. The assay used specific antibodies bound to magnetic microspheres presenting unique digital signatures for each pertussis antigen, allowing the simultaneous recognition of respective antigens in the whole vaccine, avoiding laborious procedures for adjuvant separation. Accurate and reproducible quantification of aP antigens in TdaP vaccine has been achieved in the range 0.78-50 ng/mL, providing simultaneously information on antigen identity, quantity, and degree of adsorption to aluminum hydroxide. The current study could further be considered as a model to set up in vitro potency assays thus supporting the replacement of animal tests accordingly to the 3Rs concept.

[Bordetella pertussis lipooligosaccharide-derived neoglycoconjugates - new components of pertussis vaccine]. / Neoglikokoniugaty lipooligosacharydu Bordetella pertussis-nowe potencjalne skladniki szczepionki przeciwkrztuscowej.

Pertussis is a contagious respiratory tract disease caused by the Gram-negative bacterium Bordetella pertussis. Despite widespread vaccination, in recent years the pertussis incidence has increased. The whole-cell pertussis vaccine has been very effective but reactogenic. Therefore the improved vaccines contain only a few isolated and inactivated antigens of B. pertussis. However, a waning of the acellular vaccine-induced immunity indicates that these vaccines lack some important protective B. pertussis antigens. The vaccine containing an inactivated pertussis toxin induces the production of toxin-neutralizing antibodies, but it does not lead to destruction of bacteria. Since many virulence factors are involved in the pathogenesis of pertussis, beside the toxin-neutralizing activity, the direct bactericidal activity is essential in anti-pertussis immunity. Lipooligosaccharide is the main surface component of B. pertussis. It is a target for bactericidal antibodies during natural infection. The endotoxic activity of LOS makes it unacceptable for acellular vaccines against B. pertussis. However, the non-toxic moiety of the B. pertussis LOS-derived oligosaccharide coupled to a carrier protein forms an immunogenic glycoconjugate which has a potential application as a new component of a pertussis vaccine. In this paper, we present a review of current research and reasons for the increased pertussis incidence. The epidemiologic situation of pertussis in the past decades showing the ineffectiveness of contemporary, acellular pertussis vaccines is also discussed. The immune processes elicited by natural infection with B. pertussis were compared to the vaccine-induced immunity. The important role of bactericidal antibodies against lipooligosaccharide was indicated in effective immune defense. In a number of research papers the immunogenicity and protective properties of glycoconjugates containing the oligosaccharide component of B. pertussis have been described, and its application as a new component of a pertussis vaccine have been implied.

Characterization of co-purified acellular pertussis vaccines.

Whole-cell pertussis vaccines (WPVs) have been completely replaced by the co-purified acellular vaccines (APVs) in China. To date few laboratory studies were reported for co-purified APVs in terms of their antigenic composition and protective immune responses. To further understand the antigenic composition in co-purified APVs, in the present study 2-dimensional gel electrophoresis-based proteomic technology was used to analyze the composition of co-purified APVs. The results showed that besides the main antigens pertussis toxin (PT) and filamentous hemagglutinin (FHA), co-purified APVs also contained pertactin (PRN), fimbriae (FIM) 2and3 and other minor protein antigens. Of the 9 proteins identified, 3 were differentially presented in products from manufacturer 1 and manufacturer 2. Compared with WPVs and purified APVs, co-purified APVs induced a mixed Th1/Th2 immune response with more toward to a Th1 response than the purified APVs in this study. These results hint that different immune mechanisms might be involved in protection induced by co-purified and purified APVs.

Genetically detoxified pertussis toxin (PT-9K/129G): implications for immunization and vaccines.

Pertussis toxin (PT) is one of the major virulence factors of Bordetella pertussis and the primary component of all pertussis vaccines available to date. Because of its various noxious effects the toxin needs to be detoxified. In all currently available vaccines, detoxification is achieved by treatment with high quantity of chemical agents such as formaldehyde, glutaraldehyde or hydrogen peroxide. Although effective in detoxification, this chemical treatment alters dramatically the immunological properties of the toxin. In contrast, PT genetically detoxified through the substitution of two residues necessary for its enzymatic activity maintains all functional and immunological properties. This review describes in detail the characteristics of this PT-9K/129G mutant and shows that it is non-toxic and a superior immunogen compared with chemically detoxified PT. Importantly, data from an efficacy trial show that the PT-9K/129G-based vaccine induces earlier and longer-lasting protection, further supporting the hypothesis that PT-9K/129G represents an ideal candidate for future pertussis vaccine formulations.

[Immunobiological properties of Bordetella pertussis lipopolysaccharide in the acellular pertussis vaccine].

AIM: Study of Bordetella pertussis lipopolysaccharide (LPS) immunobiological properties in the acellular pertussis vaccine. MATERIALS AND METHODS: Experimental series of acellular pertussis vaccines (APV), lyophilized LPS were used. Antibody titers against LPS in mice sera were evaluated by using EIA with peroxidase conjugate of anti-species antibodies against mice IgG. LPS activity in B. pertussis antigen complex preparations was determined in quantitative chromogenic LAL-test by end point. APV protective activity was determined in mice test during intracerebral infection by B. pertussis strain No. 18323 virulent culture. APV safety was determined in the mice body weight change test. RESULTS: The presence of LPS in APV was shown in immune electrophoresis with purified B. pertussis LPS preparation as a control. Formalin treatment changes immunochemical properties of APV LPS that lead to the shift of precipitation bands with pertussis agglutinating sera from the start zone into cathode. The quantity of LPS in pertussis culture supernatants was on average 49050 +/- 6774 endotoxin units per ml (EU/ml). In APV preparations the quantity of LPS was on average 906 +/- 90 EU/ml, i.e. decreased by more than 50 times. An increase of antibody titers against B. pertussis LPS in mice sera after the APV immunization was shown in EIA, which gives evidence of its presence in immunogenic form in the complex preparations. The preclinical studies carried out show protective activity and specific safety of the experimental APV series. CONCLUSION: Formalin-neutralized APV preparation is a complex of protein antigens in association with LPS. Formalin treatment results in modification of LPS molecule that retains antigenic properties but is significantly less toxic.

Bordetella pertussis iron regulated proteins as potential vaccine components.

Bordetella pertussis is the etiologic agent of whooping cough, an illness whose incidence has been increasing over the last decades. Pertussis reemergence despite high vaccination coverage, together with the recent isolation of circulating strains deficient in some of the vaccine antigens, highlight the need for new vaccines. Proteins induced under physiological conditions, such as those required for nutrient acquisition during infection, might represent good targets for better preventive strategies. By mean of serological proteome analysis we identified two novel antigens of B. pertussis potentially involved in iron acquisition during host colonization. We had previously demonstrated that one of them, designated IRP1-3, is protective against pertussis infection in mice. In the present study, we show that the other antigen, named AfuA (BP1605), is a highly antigenic protein, exposed on the bacterial surface, conserved among clinical isolates and expressed during infection. Immunization of mice with the recombinant AfuA induced opsonophagocytic antibodies which could explain the protection against B. pertussis infection conferred by mice immunization with rAfuA. Importantly, we found that the addition of rAfuA and rIRP1-3 proteins to the commercial three pertussis components acellular vaccine significantly increased its protective activity. Taken together, our results point at these two antigens as potential components of a new generation of acellular vaccines.