Intranasal vaccination with recombinant outer membrane protein CD and adamantylamide dipeptide as the mucosal adjuvant enhances pulmonary clearance of Moraxella catarrhalis in an experimental murine model

Needle-Free Immunization with Chitosan-Based Systems

Despite successful use, needle-based immunizations have several issues such as the risk of injuries and infections from the reuse of needles and syringes and the low patient compliance due to pain and fear of needles during immunization. In contrast, needle-free immunizations have several advantages including ease of administration, high level of patient compliance and the possibility of mass vaccination. Thus, there is an increasing interest on developing effective needle-free immunizations via cutaneous and mucosal approaches. Here, we discuss several methods of needle-free immunizations and provide insights into promising use of chitosan systems for successful immunization.

A Cation-Binding Surface Protein as a Vaccine Antigen To Prevent Moraxella catarrhalis Otitis Media and Infections in Chronic Obstructive Pulmonary Disease

Moraxella catarrhalis is an exclusively human respiratory tract pathogen that is a common cause of otitis media in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. A vaccine to prevent these infections would have a major impact on reducing the substantial global morbidity and mortality in these populations. Through a genome mining approach, we identified AfeA, an ∼32-kDa substrate binding protein of an ABC transport system, as an excellent candidate vaccine antigen. Recombinant AfeA was expressed and purified and binds ferric, ferrous, manganese, and zinc ions, as demonstrated by thermal shift assays. It is a highly conserved protein that is present in all strains of M. catarrhalis Immunization with recombinant purified AfeA induces high-titer antibodies that recognize the native M. catarrhalis protein. AfeA expresses abundant epitopes on the bacterial surface and induces protective responses in the mouse pulmonary clearance model following aerosol challenge with M. catarrhalis Finally, AfeA is expressed during human respiratory tract infection of adults with chronic obstructive pulmonary disease (COPD). Based on these observations, AfeA is an excellent vaccine antigen to be included in a vaccine to prevent infections caused by M. catarrhalis.

Potential impact of a Moraxella catarrhalis vaccine in COPD

Moraxella catarrhalis is the second most common cause of exacerbations in adults with COPD, resulting in enormous morbidity and mortality in this clinical setting. Vaccine development for M. catarrhalis has lagged behind the other two important causes of exacerbations in COPD, nontypeable Haemophilus influenzae and Streptococcus pneumoniae. While no licensed vaccine is currently available for M. catarrhalis, several promising candidate vaccine antigens have been identified and characterized and are close to entering clinical trials. Key steps that are required to advance vaccines for M. catarrhalis along the translational pipeline include standardization of assay systems to assess candidate antigens, identification of a reliable correlate of protection and expansion of partnerships between industry, academia and government to overcome regulatory hurdles. A vaccine to prevent M. catarrhalis infections in COPD would have a major impact in reducing morbidity, mortality and healthcare costs in COPD.

Sulfate-binding protein, CysP, is a candidate vaccine antigen of Moraxella catarrhalis

Moraxella catarrhalis causes otitis media in children and respiratory tract infections in adults with chronic obstructive pulmonary disease (COPD). A vaccine to prevent M. catarrhalis infections would have an enormous impact globally in preventing morbidity caused by M. catarrhalis in these populations. Using a genome mining approach we have identified a sulfate binding protein, CysP, of an ATP binding cassette (ABC) transporter system as a novel candidate vaccine antigen. CysP expresses epitopes on the bacterial surface and is highly conserved among strains. Immunization with CysP induces potentially protective immune responses in a murine pulmonary clearance model. In view of these features that indicate CysP is a promising vaccine antigen, we conducted further studies to elucidate its function. These studies demonstrated that CysP binds sulfate and thiosulfate ions, plays a nutritional role for the organism and functions in intracellular survival of M. catarrhalis in human respiratory epithelial cells. The observations that CysP has features of a vaccine antigen and also plays an important role in growth and survival of the organism indicate that CysP is an excellent candidate vaccine antigen to prevent M. catarrhalis otitis media and infections in adults with COPD.

ATP-Binding Cassette (ABC) Transporters of the Human Respiratory Tract Pathogen, Moraxella catarrhalis: Role in Virulence

Moraxella catarrhalis is a human respiratory tract pathogen that causes otitis media (middle ear infections) in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. In view of the huge global burden of disease caused by M. catarrhalis, the development of vaccines to prevent these infections and better approaches to treatment have become priorities. In previous work, we used a genome mining approach that identified three substrate binding proteins (SBPs) of ATP-binding cassette (ABC) transporters as promising candidate vaccine antigens. In the present study, we performed a comprehensive assessment of 19 SBPs of 15 ABC transporter systems in the M. catarrhalis genome by engineering knockout mutants and studying their role in assays that assess mechanisms of infection. The capacity of M. catarrhalis to survive and grow in the nutrient-limited and hostile environment of the human respiratory tract, including intracellular growth, account in part for its virulence. The results show that ABC transporters that mediate uptake of peptides, amino acids, cations and anions play important roles in pathogenesis by enabling M. catarrhalis to 1) grow in nutrient-limited conditions, 2) invade and survive in human respiratory epithelial cells and 3) persist in the lungs in a murine pulmonary clearance model. The knockout mutants of SBPs and ABC transporters showed different patterns of activity in the assay systems, supporting the conclusion that different SBPs and ABC transporters function at different stages in the pathogenesis of infection. These results indicate that ABC transporters are nutritional virulence factors, functioning to enable the survival of M catarrhalis in the diverse microenvironments of the respiratory tract. Based on the role of ABC transporters as virulence factors of M. catarrhalis, these molecules represent potential drug targets to eradicate the organism from the human respiratory tract.

Immunoinformatics Identifies a Lactoferrin Binding Protein A Peptide as a Promising Vaccine With a Global Protective Prospective Against Moraxella catarrhalis

BACKGROUND

Moraxella catarrhalis is an established pathogen that is causing substantial infections to both children and adults. However, so far there is no effective vaccine to halt the spread of these infections.

METHODS

Immunoinformatics tools were used to predict M. catarrhalis epitopes that could offer immunoprotection among major proportions of human populations worldwide. Mice were immunized with the best 3 peptides and then challenged with M. catarrhalis in the pulmonary clearance model. Finally, antibodies against these epitopes were detected in humans.

RESULTS

Immunoinformatics analyses identified 44 epitopes that are predicted to be good major histocompatibility complex class II binders and at the same time show high population coverage worldwide. After intraperitoneal immunization of mice with the best 3 peptides, peptide A, derived from lactoferrin-binding protein A, showed superior activity in immunogenicity and in clearing M. catarrhalis from mouse lungs. Higher clearance was obtained by combining intraperitoneal and intranasal immunization. In the serum samples from children with otitis media infected with M. catarrhalis, antibody levels against peptide A were significantly lower than in samples from children without otitis media.

CONCLUSIONS

Peptide A is the first promising peptide-based vaccine against M. catarrhalis Immunoinformatics predicts that it should have a global protection around the world.

Vaccine targets against Moraxella catarrhalis

INTRODUCTION

Moraxella catarrhalis is a prominent pathogen that causes acute otitis media in children and lower respiratory tract infections in adults, resulting in a significant socioeconomic burden on healthcare systems globally. No vaccine is currently available for M. catarrhalis. Promising M. catarrhalis target antigens have been characterized in animal models and should soon enter human clinical trials.

AREAS COVERED

This review discusses the detailed features and research status of current candidate target antigens for an M. catarrhalis vaccine. The approaches for assessing M. catarrhalis vaccine efficacy are also discussed.

EXPERT OPINION

Targeting the key molecules contributing to serum resistance may be a viable strategy to identify effective vaccine targets among M. catarrhalis antigens. Elucidating the role and mechanisms of the serum and mucosal immune responses to M. catarrhalis is significant for vaccine target selection, testing and evaluation. Developing animal models closely simulating M. catarrhalis-caused human respiratory diseases is of great benefit in better understanding pathogenesis and evaluating vaccine efficacy. Carrying out clinical trials will be a landmark in the progress of M. catarrhalis vaccine research. Combined multicomponent vaccines will be a focus of future M. catarrhalis vaccine studies.

Bactericidal, opsonophagocytic and anti-adhesive effectiveness of cross-reactive antibodies against Moraxella catarrhalis

Moraxella catarrhalis is a human-restricted significant respiratory tract pathogen. The bacteria accounts for 15-20% of cases of otitis media in children and is an important causative agent of infectious exacerbations of chronic obstructive pulmonary disease in adults. The acquisition of new M. catarrhalis strains plays a central role in the pathogenesis of both mentioned disorders. The antibody-dependent immune response to this pathogen is critical for its effective elimination. Thus, the knowledge about the protective threshold of cross-reactive antibodies with defined functionality seems to be important. The complex analysis of broad-spectrum effectiveness of cross-reactive antibodies against M. catarrhalis has never been performed. The goal of the present study was to demonstrate and compare the bactericidal, opsonophagocytic and blocking function of cross-reacting antibodies produced in response to this bacterium or purified outer membrane proteins incorporated in Zwittergent-based micelles. The multivalent immunogens were used in order to better mimic the natural response of the host. The demonstrated broad-spectrum effectiveness of cross-reactive antibodies in pathogen eradication or inhibition strongly indicates that this pool of antibodies by recognition of pivotal shared M. catarrhalis surface epitopes seems to be an essential additional source to control host-microbe interaction.

Substrate binding protein SBP2 of a putative ABC transporter as a novel vaccine antigen of Moraxella catarrhalis

Moraxella catarrhalis is a common respiratory tract pathogen that causes otitis media in children and infections in adults with chronic obstructive pulmonary disease. Since the introduction of the pneumococcal conjugate vaccines with/without protein D of nontypeable Haemophilus influenzae, M. catarrhalis has become a high-priority pathogen in otitis media. For the development of antibacterial vaccines and therapies, substrate binding proteins of ATP-binding cassette transporters are important targets. In this study, we identified and characterized a substrate binding protein, SBP2, of M. catarrhalis. Among 30 clinical isolates tested, the sbp2 gene sequence was highly conserved. In 2 different analyses (whole-cell enzyme-linked immunosorbent assay and flow cytometry), polyclonal antibodies raised to recombinant SBP2 demonstrated that SBP2 expresses epitopes on the bacterial surface of the wild type but not the sbp2 mutant. Mice immunized with recombinant SBP2 showed significantly enhanced clearance of M. catarrhalis from the lung compared to that in the control group at both 25-μg and 50-μg doses (P < 0.001). We conclude that SBP2 is a novel, attractive candidate as a vaccine antigen against M. catarrhalis.

Use of the Chinchilla model to evaluate the vaccinogenic potential of the Moraxella catarrhalis filamentous hemagglutinin-like proteins MhaB1 and MhaB2

Moraxella catarrhalis causes significant health problems, including 15–20% of otitis media cases in children and ∼10% of respiratory infections in adults with chronic obstructive pulmonary disease. The lack of an efficacious vaccine, the rapid emergence of antibiotic resistance in clinical isolates, and high carriage rates reported in children are cause for concern. In addition, the effectiveness of conjugate vaccines at reducing the incidence of otitis media caused by Streptococcus pneumoniae and nontypeable Haemophilus influenzae suggest that M. catarrhalis infections may become even more prevalent. Hence, M. catarrhalis is an important and emerging cause of infectious disease for which the development of a vaccine is highly desirable. Studying the pathogenesis of M. catarrhalis and the testing of vaccine candidates have both been hindered by the lack of an animal model that mimics human colonization and infection. To address this, we intranasally infected chinchilla with M. catarrhalis to investigate colonization and examine the efficacy of a protein-based vaccine. The data reveal that infected chinchillas produce antibodies against antigens known to be major targets of the immune response in humans, thus establishing immune parallels between chinchillas and humans during M. catarrhalis infection. Our data also demonstrate that a mutant lacking expression of the adherence proteins MhaB1 and MhaB2 is impaired in its ability to colonize the chinchilla nasopharynx, and that immunization with a polypeptide shared by MhaB1 and MhaB2 elicits antibodies interfering with colonization. These findings underscore the importance of adherence proteins in colonization and emphasize the relevance of the chinchilla model to study M. catarrhalis–host interactions.

Panel 6: Vaccines

OBJECTIVE

To update progress on the effectiveness of vaccine for prevention of acute otitis media (AOM) and identification of promising candidate antigens against Streptococcus pneumoniae, nontypeable Haemophilus influenzae, and Moraxella catarrhalis.

REVIEW METHODS

Literature searches were performed in OvidSP and PubMed restricted to articles published between June 2007 and September 2011. Search terms included otitis media, vaccines, vaccine antigens, and each of the otitis pathogens and candidate antigens identified in the ninth conference report.

CONCLUSIONS

The current report provides further evidence for the effectiveness of pneumococcal conjugate vaccines (PCVs) in the prevention of otitis media. Observational studies demonstrate a greater decline in AOM episodes than reported in clinical efficacy trials. Unmet challenges include extending protection to additional serotypes and additional pathogens, the need to prevent early episodes, the development of correlates of protection for protein antigens, and the need to define where an otitis media vaccine strategy fits with priorities for child health.

IMPLICATIONS FOR PRACTICE

Acute otitis media continues to be a burden on children and families, especially those who suffer from frequent recurrences. The 7-valent PCV (PCV7) has reduced the burden of disease as well as shifted the pneumococcal serotypes and the distribution of otopathogens currently reported in children with AOM. Antibiotic resistance remains an ongoing challenge. Multiple candidate antigens have demonstrated the necessary requirements of conservation, surface exposure, immunogenicity, and protection in animal models. Further research on the role of each antigen in pathogenesis, in the development of correlates of protection in animal models, and in new adjuvants to elicit responses in the youngest infants is likely to be productive and permit more antigens to move into human clinical trials.

Comprehensive antigen screening identifies Moraxella catarrhalis proteins that induce protection in a mouse pulmonary clearance model

Moraxella catarrhalis is one of the three most common causative bacterial pathogens of otitis media, however no effective vaccine against M. catarrhalis has been developed so far. To identify M. catarrhalis vaccine candidate antigens, we used carefully selected sera from children with otitis media and healthy individuals to screen small-fragment genomic libraries that are expressed to display frame-selected peptides on a bacterial cell surface. This ANTIGENome technology led to the identification of 214 antigens, 23 of which were selected by in vitro or in vivo studies for additional characterization. Eight of the 23 candidates were tested in a Moraxella mouse pulmonary clearance model, and 3 of these antigens induced significantly faster bacterial clearance compared to adjuvant or to the previously characterized antigen OmpCD. The most significant protection data were obtained with the antigen MCR_1416 (Msp22), which was further investigated for its biological function by in vitro studies suggesting that Msp22 is a heme binding protein. This study comprises one of the most exhaustive studies to identify potential vaccine candidate antigens against the bacterial pathogen M. catarrhalis.

Secondary electrospray ionization-mass spectrometry (SESI-MS) breathprinting of multiple bacterial lung pathogens, a mouse model study

Bacterial pneumonia is one of the leading causes of disease-related morbidity and mortality in the world, in part because the diagnostic tools for pneumonia are slow and ineffective. To improve the diagnosis success rates and treatment outcomes for bacterial lung infections, we are exploring the use of secondary electrospray ionization-mass spectrometry (SESI-MS) breath analysis as a rapid, noninvasive method for determining the etiology of lung infections in situ. Using a murine lung infection model, we demonstrate that SESI-MS breathprints can be used to distinguish mice that are infected with one of seven lung pathogens: Haemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae, representing the primary causes of bacterial pneumonia worldwide. After applying principal components analysis, we observed that with the first three principal components (primarily comprised of data from 14 peaks), all infections were separable via SESI-MS breathprinting (P < 0.0001). Therefore, we have shown the potential of this SESI-MS approach for rapidly detecting and identifying acute bacterial lung infections in situ via breath analysis.

Moraxella catarrhalis: from interactions with the host immune system to vaccine development

Moraxella catarrhalis is a human-restricted commensal that over the last two decades has developed into an emerging respiratory tract pathogen. The bacterial species is equipped with various adhesins to facilitate its colonization. Successful evasion of the human immune system is a prerequisite for Moraxella infection. This strategy involves induction of an excessive proinflammatory response, intervention of granulocyte recruitment to the infection site, activation of selected pattern recognition receptors and cellular adhesion molecules to counteract the host bacteriolytic attack, as well as, finally, reprogramming of antigen presenting cells. Host immunomodulator molecules are also exploited by Moraxella to aid in resistance against complement killing and host bactericidal molecules. Thus, breaking the basis of Moraxella immune evasion mechanisms is fundamental for future invention of effective therapy in controlling Moraxella infection.

Mucosal immunity and nasal influenza vaccination

Influenza remains a threat to public health, with immunization being a suitable method of infection prevention and control. Our understanding of the immunological regulations at the mucosa, antigen processing and presentation, and B-cell activation has improved, enabling research and targeted induction of immune responses at the site of antigen delivery. Nasal influenza immunization has distinct features compared with intramuscular vaccines, providing protection at the pathogen's entry site, higher levels of mucosal antibodies, cross-protection and needle-free application. This review summarizes our knowledge about mucosal immunity and the experience from clinical trials on the impact and safety of nasal influenza vaccination.

Purification and crystallization of the ABC-type transport substrate-binding protein OppA from Thermoanaerobacter tengcongensis

Di- and oligopeptide- binding protein OppAs play important roles in solute and nutrient uptake, sporulation, biofilm formation, cell wall muropeptides recycling, peptide-dependent quorum-sensing responses, adherence to host cells, and a variety of other biological processes. Soluble OppA from Thermoanaerobacter tengcongensis was expressed in Escherichia coli. The protein was found to be >95% pure with SDS-PAGE after a series of purification steps and the purity was further verified by mass spectrometry. The protein was crystallized using the sitting-drop vapour-diffusion method with PEG 400 as the precipitant. Crystal diffraction extended to 2.25 Å. The crystal belonged to space group C222(1), with unit-cell parameters of a=69.395, b=199.572, c=131.673 Å, and α=β=γ=90°.

Characterization and evaluation of the Moraxella catarrhalis oligopeptide permease A as a mucosal vaccine antigen

Moraxella catarrhalis is a common cause of otitis media in children and of lower respiratory tract infections in adults with chronic obstructive pulmonary disease; therefore, these two groups would benefit from a vaccine to prevent M. catarrhalis infections. A genome mining approach for vaccine antigens identified oligopeptide permease protein A (OppA), an oligopeptide binding protein of an apparent oligopeptide transport system. Analysis of the oppA gene by PCR and sequence analysis revealed that OppA is highly conserved among clinical isolates of M. catarrhalis. Recombinant OppA was expressed as a lipoprotein and purified, and an oppA knockout mutant was constructed. Antiserum raised to recombinant purified OppA recognized epitopes on the bacterial surface of the wild type but not the OppA knockout mutant. Antibodies raised to purified recombinant OppA recognized native OppA in multiple strains. Intranasal immunization of mice induced systemic and mucosal antibodies to OppA and resulted in enhanced clearance of M. catarrhalis in a mouse pulmonary clearance model. OppA is a highly conserved, immunogenic protein that expresses epitopes on the bacterial surface and that induces potentially protective immune responses in a mouse model. OppA should be evaluated further as a vaccine antigen for M. catarrhalis.

Characterization of proteins Msp22 and Msp75 as vaccine antigens of Moraxella catarrhalis

Moraxella catarrhalis is a respiratory tract pathogen causing otitis media in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. This study examined two newly identified proteins as potential vaccine antigens. Antisera raised to recombinant purified proteins Msp22 and Msp75 recognized corresponding native proteins in multiple strains of M. catarrhalis. Vaccine formulations individually administered subcutaneously and intranasally showed enhanced clearance of M. catarrhalis in a mouse pulmonary clearance model by both routes of administration. Msp22 and Msp75 are antigenically conserved proteins that induce potentially protective immune responses and should be examined further as vaccine antigens for M. catarrhalis.

Immune modulators with defined molecular targets: cornerstone to optimize rational vaccine design

Vaccination remains the most valuable tool for preventing infectious diseases. However, the performance of many existing vaccines should be improved and there are diseases for which vaccines are still not available. The use of well-defined antigens for the generation of subunit vaccines has led to products with an improved safety profile. However, purified antigens are usually poorly immunogenic, making essential the use of adjuvants. Despite the fact that adjuvants have been used to increase the immunogenicity of vaccines for more than 70 years, only a handful has been licensed for human use (e.g., aluminium salts, the micro-fluidized squalene-in-water emulsion MF59 and monophosphoryl lipid A). Thus, the development of new adjuvants which are able to promote broad and sustained immune responses at systemic and mucosal levels still remains as a major challenge in vaccinology. Recent advances in our understanding of the immune system have facilitated the identification of new biological targets for screening programs aimed at the discovery of novel immune stimulators. This resulted in the identification of new candidate adjuvants, which made possible the modulation of the immune responses elicited according to specific needs. A number of promising adjuvants which are currently under preclinical or clinical development will be described in this chapter.

Current progress of adhesins as vaccine candidates for Moraxella catarrhalis

Moraxella catarrhalis is an emerging pathogen and all isolates are now considered beta-lactamase producing. Potential further use of vaccines against Streptococcus pneumoniae and nontypeable Haemophilus influenzae means that M. catarrhalis might be thrust further into the limelight. However, a vaccine has not yet been designed. In this review, the progress of M. catarrhalis adhesins as vaccine candidates is discussed with a focus on various candidate antigens that spanned those discovered more than 10 years ago, for example, the ubiquitous surface proteins to newer antigens, such as the Moraxella IgD-binding hemagglutinin.

Contribution of Moraxella catarrhalis type IV pili to nasopharyngeal colonization and biofilm formation

Moraxella catarrhalis is a gram-negative mucosal pathogen of the human respiratory tract. Although little information is available regarding the initial steps of M. catarrhalis pathogenesis, this organism must be able to colonize the human mucosal surface in order to initiate an infection. Type IV pili (TFP), filamentous surface appendages primarily comprised of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of bacteria. We previously identified the genes that encode the major proteins involved in the biosynthesis of M. catarrhalis TFP and determined that the TFP expressed by this organism are highly conserved and essential for natural transformation. We extended this initial study by investigating the contribution of TFP to the early stages of M. catarrhalis colonization. TFP-deficient M. catarrhalis bacteria exhibit diminished adherence to eukaryotic cells in vitro. Additionally, our studies demonstrate that M. catarrhalis cells form a mature biofilm in continuous-flow chambers and that biofilm formation is enhanced by TFP expression. The potential role of TFP in colonization by M. catarrhalis was further investigated using in vivo studies comparing the abilities of wild-type M. catarrhalis and an isogenic TFP mutant to colonize the nasopharynx of the chinchilla. These results suggest that the expression of TFP contributes to mucosal airway colonization. Furthermore, these data indicate that the chinchilla model of nasopharyngeal colonization provides an effective animal system for studying the early steps of M. catarrhalis pathogenesis.

Needle-free vaccine delivery

The need for minimally invasive delivery methods is urgent. As the number of registered vaccines increases, so does the number of injections. The use of sharps can be unsafe and needle immunisation is less suitable for mass immunisations during emergencies such as pandemics or bioterrorist attacks. The approach of combining vaccines has limitations due to high development costs, risk of pharmaceutical or immunological interference and economic risks. Advancements in the development of alternatives to injection with syringes and needles are discussed in this paper, and include: mucosal vaccination, injection without needles and vaccine delivery via the skin.

Toll or toll-free adjuvant path toward the optimal vaccine development

Successful vaccines contain an adjuvant component that activates the innate immune system, thereby eliciting antigen-specific immune responses. Many adjuvants appear to be ligands for toll-like receptors (TLR), which are thus promising targets for the development of novel adjuvants to elicit vaccine immunogenicity. However, recent evidence suggests that some adjuvants activate the innate immune system in a TLR-independent manner possibly through other pattern recognition receptors and signaling machinery. In particular, newly identified intracellular retinoic-acid-inducible gene (RIG)-like receptors, NOD-like receptors, or even as yet unknown recognition machinery for the adjuvant may regulate TLR-independent vaccine immunogenicity. To develop optimal vaccines, it will be critical to understand how TLR-dependent and TLR-independent innate immune activation, by various adjuvants, control the consequent adaptive immune responses to vaccine.