OprF/I-vaccinated sera inhibit binding of human interferon-gamma to Pseudomonas aeruginosa.

The recombinant outer membrane protein OprF/I has been demonstrated in previous studies to protect against Pseudomonas aeruginosa infection through a mechanism of enhanced antibody-mediated opsonophagocytosis. Recent evidence indicates that P. aeruginosa enhances its virulence phenotype as a consequence of binding to human IFN-gamma through an outer membrane protein, OprF. In this study, we demonstrate that a single boost injection of OprF/I vaccine elicited a strong OprF/I-specific antibody response in individuals who were previously vaccinated with OprF/I in a clinical trial. The OprF/I-vaccinated sera inhibit P. aeruginosa binding to IFN-gamma, suggesting an alternative mechanism by which the OprF/I vaccine confers protection against P. aeruginosa infection.

Systemic, nasal and oral live vaccines against Pseudomonas aeruginosa: a clinical trial of immunogenicity in lower airways of human volunteers.

Vaccination against Pseudomonas aeruginosa is a desirable, yet challenging strategy for prevention of airway infection in patients with cystic fibrosis. We compared the formation of antibodies in lower airways induced by systemic and mucosal vaccination strategies. We immunised 48 volunteers in six vaccination groups with either a systemic, a nasal, or four newly constructed oral live vaccines based on attenuated live Salmonella (strains CVD908 and Ty21a), followed by a systemic booster vaccination. All vaccines were based on a recombinant fusion protein of the highly conserved P. aeruginosa outer membrane proteins OprF and OprI as antigen. While systemic and mucosal vaccines induced a comparable rise of serum antibody titers, a significant rise of IgA and IgG antibodies in the lower airways was noted only after nasal and oral vaccinations. We conclude that nasal and oral OprF-OprI vaccines are promising candidates for development of antipseudomonal immunisation through inducing a specific antibody response in the lung.

Immune responses in the airways by nasal vaccination with systemic boosting against Pseudomonas aeruginosa in chronic lung disease.

RATIONALE: Pneumonia caused by Pseudomonas (P.) aeruginosa is a leading cause of morbidity and mortality in patients with chronic lung diseases. Systemic vaccination in patients with cystic fibrosis has been only successful in part. Mucosal vaccination could lead to enhanced airway immunogenicity. Pathogen specific secretory IgA antibodies could prevent bacterial invasion into the lung mucosa. OBJECTIVES: A phase 1-2 mucosal vaccination trial with an intranasal P. aeruginosa vaccine was performed. METHODS: 12 patients with chronic lung diseases (8 COPD, 2 cystic fibrosis, 1 bronchiectasis, 1 histiocytosis X) were vaccinated three times intranasally followed by a systemic booster vaccination with a recombinant hybrid protein encompassing the main protective epitopes of two outer membrane proteins of P. aeruginosa. Mucosal and systemic antibody responses were measured after boosting and after a half-year follow-up compared to a representative control cohort. MEASUREMENTS: Specific IgG and IgA antibodies in the patient's sera, saliva and sputum were determined by enzyme-linked immunosorbent assay (ELISA) and IgG subclass distributions were defined with monoclonal mouse antibodies. RESULTS: Both forms of vaccination were well tolerated. Significant elevated IgA and IgG antibodies could be measured in sputum, saliva and in the sera of 11/12 patients. CONCLUSIONS: Mucosal vaccination followed by systemic boost with an outer membrane protein vaccine against P. aeruginosa leads to airway immunogenicity against the pathogen. Further clinical trials should elucidate the protective efficacy of this vaccination method.

Assessment of pulmonary antibodies with induced sputum and bronchoalveolar lavage induced by nasal vaccination against Pseudomonas aeruginosa: a clinical phase I/II study.

BACKGROUND: Vaccination against Pseudomonas aeruginosa is a desirable albeit challenging strategy for prevention of airway infection in patients with cystic fibrosis. We assessed the immunogenicity of a nasal vaccine based on the outer membrane proteins F and I from Pseudomonas aeruginosa in the lower airways in a phase I/II clinical trial. METHODS: N = 12 healthy volunteers received 2 nasal vaccinations with an OprF-OprI gel as a primary and a systemic (n = 6) or a nasal booster vaccination (n = 6). Antibodies were assessed in induced sputum (IS), bronchoalveolar lavage (BAL), and in serum. RESULTS: OprF-OprI-specific IgG and IgA antibodies were found in both BAL and IS at comparable rates, but differed in the predominant isotype. IgA antibodies in IS did not correlate to the respective serum levels. Pulmonary antibodies were detectable in all vaccinees even 1 year after the vaccination. The systemic booster group had higher IgG levels in serum. However, the nasal booster group had the better long-term response with bronchial antibodies of both isotypes. CONCLUSION: The nasal OprF-OprI-vaccine induces a lasting antibody response at both, systemic and airway mucosal site. IS is a feasible method to non-invasively assess bronchial antibodies. A further optimization of the vaccination schedule is warranted.

A three-step purification method of large quantities of human recombinant alpha endothelial cellular growth factor for clinical use.

The endothelial cellular growth factor alpha-ECGF is a candidate drug for the induction of therapeutic neoangiogenesis. Its use in extensive experimental and clinical trials is hampered by the fact that currently published purification procedures allow only small yields, and the absence of pyrogenic impurities is not demonstrated. The rh alpha-ECGF was expressed in E. coli. Isolation of rh alpha-ECGF from E. coli lysates to apparent homogenicity was achieved by a three step purification procedure involving ionic exchange, heparin-sepharose and polymyxin B chromatography. By this method, 200 mg of rh alpha-ECGF was purified from 15 g wet weight E. coli bacteria. The isolated protein of 18 kDa appeared as a single band after SDS gel electrophoresis and subsequent silver-staining. The biological activity was expressed in the chorion-allantois-membrane assay and in the 3H-thymidine proliferation in baby hamster kidney cells. Drug trials with rabbits revealed no increase in body temperature after intravenous injections with 1 mg rh-ECGF.

Enhanced immunogenicity in the murine airway mucosa with an attenuated Salmonella live vaccine expressing OprF-OprI from Pseudomonas aeruginosa.

We constructed an oral live vaccine based on the attenuated aroA mutant Salmonella enterica serovar Typhimurium strain SL3261 expressing outer membrane proteins F and I (OprF-OprI) from Pseudomonas aeruginosa and investigated it in a mouse model. Strains with in vivo inducible protein expression with the PpacC promoter showed good infection rates and immunogenicity but failed to engender detectable antibodies in the lung. However, a systemic booster vaccination following an oral primary immunization yielded high immunoglobulin A (IgA) and IgG antibody levels in both upper and lower airways superior to conventional systemic or mucosal booster vaccination alone. In addition, the proportion of IgG1 and IgG2a antibodies suggested that the systemic booster does not alter the more TH1-like type of response induced by the oral Salmonella primary vaccination. We conclude that an oral primary systemic booster vaccination strategy with an appropriate mucosal vector may be advantageous in diseases with the risk of P. aeruginosa airway infection, such as cystic fibrosis.

Secretory delivery of recombinant proteins in attenuated Salmonella strains: potential and limitations of Type I protein transporters.

Live attenuated Salmonella strains have been extensively explored as oral delivery systems for recombinant vaccine antigens and effector proteins with immunoadjuvant and immunomodulatory potential. The feasibility of this approach was demonstrated in human vaccination trials for various antigens. However, immunization efficiencies with live vaccines are generally significantly lower compared to those monitored in parenteral immunizations with the same vaccine antigen. This is, at least partly, due to the lack of secretory expression systems, enabling large-scale extracellular delivery of vaccine and effector proteins by these strains. Because of their low complexity and the terminal location of the secretion signal in the secreted protein, Type I (ATP-binding cassette) secretion systems appear to be particularly suited for development of such recombinant extracellular expression systems. So far, the Escherichia coli hemolysin system is the only Type I secretion system, which has been adapted to recombinant protein secretion in Salmonella. However, this system has a number of disadvantages, including low secretion capacity, complex genetic regulation, and structural restriction to the secreted protein, which eventually hinder high-level in vivo delivery of recombinant vaccines and effector proteins. Thus, the development of more efficient recombinant protein secretion systems, based on Type I exporters can help to improve efficacies of live recombinant Salmonella vaccines. Type I secretion systems, mediating secretion of bacterial surface layer proteins, such as RsaA in Caulobacter crescentus, are discussed as promising candidates for improved secretory delivery systems.

Effect of in situ expression of human interleukin-6 on antibody responses against Salmonella typhimurium antigens.

In an attempt to trigger increased mucosal secretory immune responses against bacterial surface antigens, we constructed an optimized human interleukin (hIL)-6-secreting Salmonella typhimurium strain (X4064(pCH1A+pYL3E)), utilizing the hemolysin (Hly) exporter for secretory delivery of a functional hIL-6-hemolysin fusion protein (hIL-6-HlyA(s)). Through stable introduction of a second hIL-6-HlyA(s) expression plasmid (pYL3E) in the previously described X4064(pCH1A) strain, hIL-6-HlyA(s) secretion efficiencies were increased by at least 10-fold. As pCH1A in the parental strain, pYL3E was stable in vitro in the absence of antibiotic selection and in vivo neither did plasmids interfere in their stabilities. Increased hIL-6-HlyA(s) expression did not adversely interfere with bacterial growth. Comparative immunization experiments in mice with oral application of the different hIL-6-secreting strains revealed that increased in situ hIL-6-production influenced systemic antibody responses against Salmonella antigens but had no marked effect on mucosal responses. In mice immunized with X4064(pCH1A+pYL3E) significantly higher sera IgG and IgA titers for lipopolysaccharide (LPS) were found compared to mice immunized with X4064(pCH1A) and a hIL-6-negative control strain. Higher sera antibody titers were accompanied by increased numbers of IgG- and IgA-specific antibody-secreting cells in spleens and Peyer's patches, respectively. These data suggest that systemic antibody responses against Salmonella LPS are largely effected by IL-6 and, moreover, the amount and the cellular location of recombinantly expressed IL-6 appears to be crucial for enhancement of immune responses.

Clinical study to assess the immunogenicity and safety of a recombinant Pseudomonas aeruginosa OprF-OprI vaccine in burn patients.

In a recent clinical trial we evaluated the safety and immunogenicity of a recombinant OprF-OprI vaccine consisting of the mature outer membrane protein I (OprI) and amino acids 190-342 of OprF of Pseudomonas aeruginosa in burn patients and compared the elicited antibodies with antibodies against tetanus as response to a simultaneous immunization given on the day of admission. Safety and immunogenicity of the vaccine had been tested before in healthy human volunteers as published in 1999. In this first clinical trial we immunized eight burn patients suffering from second or third degree burns involving between 35% and 55% of the body surface three times with 100 microg of the OprF-OprI vaccine. The vaccine was found to be very well tolerated. The patients did not show any serious side effects - and in particular no activation of the mediator cascade was observed. None of the subjects showed systemic P. aeruginosa infections during or after the treatment of their burns. The serological tests (ELISA) for detection of antibodies against P. aeruginosa and tetanus toxoid showed seroconversion for seven patients after inoculation. The data indicate that OprF-OprI can be a useful vaccine in the therapeutic management of burn injuries.

Mucosal vaccination with a recombinant OprF-I vaccine of Pseudomonas aeruginosa in healthy volunteers: comparison of a systemic vs. a mucosal booster schedule.

We compared the immunogenicity of two vaccination schedules with either a systemic or a mucosal booster, both following a mucosal primary vaccination with a recombinant outer membrane fusion protein of Pseudomonas aeruginosa (OprF-I) in 12 healthy volunteers. The systemic booster induced higher levels of OprF-I-specific serum antibodies of IgG isotype, with a mean+/-S.E.M. of 32.6+/-7.8x10(7) enzyme-linked immunosorbent assay (ELISA) units (EU) as compared to the nasal booster with 14.6+/-2.1x10(7) EU (P=0.05). Specific serum IgA antibodies and antibodies in saliva did not differ between the two vaccination groups. We conclude that a combined mucosal/systemic vaccination with the OprF-I vaccine may offer an enhanced systemic immunogenicity. Further studies on the long-term immunogenicity and induction of antibodies on the respiratory airway surface are warranted.

Humoral immune response against proteophosphoglycan surface antigens of Entamoeba histolytica elicited by immunization with synthetic mimotope peptides.

The protozoan parasite Entamoeba histolytica, which is responsible for intestinal amebiasis and amebic liver abscess, is causing significant morbidity and mortality worldwide. Proteophosphoglycans (PPGs, also known as lipophosphoglycans, LPGs, or lipopeptidophosphoglycans, LPPGs) are major surface components of E. histolytica. Passive immunization with a monoclonal antibody (EH5) directed against the PPGs protected severe combined immune-deficient mice from amebic liver abscess. The structure of the PPGs is very complex and only known in part. To find peptide mimics of E. histolytica PPG antigens, we had screened phage-displayed random peptide libraries with the antibody EH5. We identified various peptide mimics of E. histolytica PPGs, all sharing a consensus sequence Gly-Thr-His-Pro-X-Leu. Several of the phage clones induced a significant, specific IgG response against membrane antigens of E. histolytica after immunization of mice with whole phage particles. In the present work, in order to avoid the use of phage particles for immunization, we coupled two selected chemically synthesized peptides to keyhole limpet hemocyanin (KLH). The two KLH-conjugated peptides were immunogenic in mice and induced the production of high titers of anti-peptide antibodies, and one of the two peptides was also able to induce significant titers of antibodies against E. histolytica PPGs. Our results demonstrate that the KLH-conjugated peptides are able to mimic the EH5 epitope without the M13 phage sequences flanking the peptide inserts and independent of the structural framework of the phage.

Comparison of protein with DNA therapy for chronic myocardial ischemia using fibroblast growth factor-2.

OBJECTIVE: Treatment of coronary disease by growth factors has become an increasingly used strategy for otherwise untreatable patients and is subject to a number of clinical studies. The aim is to stimulate the development of a sufficient collateral circulation and hereby to rescue cardiac function. The objective of our study was to compare the effectiveness of fibroblast growth factor-2 (FGF-2) as protein and as naked plasmid DNA in a porcine model of chronic myocardial ischemia. MATERIALS AND METHODS: A severe stenosis of the left anterior descending artery (LAD) artery was created in healthy pigs. After 1 week, perfusion and regional and global contractility was assessed at baseline at rest and under stress. Afterwards, recombinant FGF-2 (n=6) or naked plasmid DNA encoding FGF-2 (n=7) was intramyocardially injected into the LAD territory. Control animals were left untreated (n=5). After 3 months, the animals were re-examined and underwent immunohistologic analysis. One animal received an Enhanced Green Fluorescent Protein plasmid. RESULTS: Plasmid-dependent protein synthesis was present in cardiomyocytes. FGF-2 protein as well as plasmid injections resulted in an increased number of capillaries and of arterioles compared with untreated ischemia. The improvement of the regional myocardial blood flow by FGF-2 plasmid therapy at rest might however indicate the effectiveness of the DNA application for the induction of a collateral circulation. A benefit from FGF-2 plasmid therapy was revealed with regard to regional contractility. Systemic hemodynamics were partially improved following plasFGF-2 treatment. CONCLUSIONS: In this porcine model of chronic myocardial ischemia, intramyocardial injection of FGF-2 plasmid was more effective than of FGF-2 protein in improving regional perfusion and contractility compared to untreated ischemia.

Cloning and hemolysin-mediated secretory expression of a codon-optimized synthetic human interleukin-6 gene in Escherichia coli.

Previously, we constructed human interleukin-6 (hIL-6)-secreting Escherichia coli and Salmonella typhimurium strains by fusion of the hIL-6 cDNA to the HlyA(s) secretional signal, utilizing the hemolysin export apparatus for extracellular delivery of a bioactive hIL-6-hemolysin (hIL-6-HlyA(s)) fusion protein. Molecular analysis of the secretion process revealed that low secretion levels were due to inefficient gene expression. To adapt the codon usage in hIL-6 cDNA to the E. coli codon bias, a synthetic hIL-6Ec gene variant was constructed from 20 overlapping oligonucleotides, yielding a 561-bp fragment, which comprises the complete hIL-6 cDNA sequence. Genetic fusion of the hIL-6Ec gene with the hlyA(s) secretional signal as an integral part of the hemolysin operon resulted in 3-fold higher hIL-6-HlyA(s) secretion levels in E. coli, compared to a strain expressing the original hIL-6-hlyA(s) fusion gene. An increase in the electrophoretic mobility of secreted hIL-6-HlyA(s) in non-reducing SDS-PAGE, similar to that found for recombinant mature hIL-6, and the absence of such a mobility shift in the intracellular hIL-6-HlyA(s) protein fraction indicated that in hIL-6-HlyA(s) most probably correct intramolecular disulfide bond formation occurred during the secretion step. To confirm the disulfide bond formation, hIL-6-HlyA(s) was purified by a single-step immunoaffinity chromatography from culture supernatant in yields of 18 microg/L culture supernatant with purity in the range of 60%. These results demonstrate that codon usage has an impact on the hemolysin-mediated secretion of hIL-6 and, furthermore, provide evidence that the hemolysin system enables secretory delivery of disulfide-bridged proteins.

Antigenicity and immunogenicity of phage library-selected peptide mimics of the major surface proteophosphoglycan antigens of Entamoeba histolytica.

Entamoeba histolytica is the protozoan parasite responsible for intestinal amoebiasis and amoebic liver abscess, which cause significant morbidity and mortality in many countries of the world. Proteophosphoglycans (PPGs, also known as lipophosphoglycans, LPGs, or lipopeptidophosphoglycans, LPPGs) represent dominant surface components of E. histolytica. Passive immunization with a monoclonal antibody (EH5) directed against these components protected SCID mice from amoebic liver abscess, so PPGs might be regarded as vaccine candidates; however, their structure is very complex and only known in part. They are glycosylphosphatidylinositol-linked polypeptides of unknown sequence carrying glycan side-chains linked to serine residues via phosphodiester bonds. In order to identify peptide mimics of the E. histolytica PPG antigens, we screened six different phage-displayed random peptide libraries with the antibody EH5. Various peptide mimics of different length were identified and, in all the peptides, a distinct consensus sequence Gly-Thr-His-Pro-X-Leu could be identified. The phages strongly bound to the antibody, and the natural antigen inhibited binding of the phages to antibody EH5. In addition, several of the phages induced a significant immunoglobulin G response against amoebic antigens in immunized mice.

Enhancement of the protective efficacy of an oprF DNA vaccine against Pseudomonas aeruginosa.

The outer membrane protein F gene (oprF) of Pseudomonas aeruginosa was recently shown by us to protect mice from P. aeruginosa chronic pulmonary infection when used as a DNA vaccine administered by three biolistic (gene gun) intradermal inoculations given at 2-week intervals. In the present study, we used two different strategies to improve the protective efficacy of the DNA vaccine. In the first strategy, mice were primed with two biolistic intradermal inoculations with the oprF vaccine and then were given a final intramuscular booster immunization containing either a synthetic peptide-keyhole limpet hemocyanin (KLH) conjugate or a chimeric influenza virus. Both the synthetic peptide conjugate and the chimeric virus contained peptide 10, a previously identified immunoprotective epitope of protein F. The second strategy involved the addition of a second outer membrane protein to the vaccine. DNA encoding a fusion protein comprised of the C-terminal half of protein F fused to OprI was administered by three biolistic intradermal inoculations. Challenge with P. aeruginosa in a chronic pulmonary infection model demonstrated that boosting with the chimeric virus (but not with peptide-KLH) or adding oprI to the DNA vaccine significantly enhanced protection as compared to that afforded by the oprF vaccine given alone. Thus, both strategies appear to augment the protection afforded by an oprF-only DNA vaccine.