Immunization of burn-patients with a Pseudomonas aeruginosa outer membrane protein vaccine elicits antibodies with protective efficacy

Understanding Pseudomonas aeruginosa-Host Interactions: The Ongoing Quest for an Efficacious Vaccine

Pseudomonas aeruginosa is a leading cause of chronic respiratory infections in people with cystic fibrosis (CF), bronchiectasis or chronic obstructive pulmonary disease (COPD), and acute infections in immunocompromised individuals. The adaptability of this opportunistic pathogen has hampered the development of antimicrobial therapies, and consequently, it remains a major threat to public health. Due to its antimicrobial resistance, vaccines represent an alternative strategy to tackle the pathogen, yet despite over 50 years of research on anti-Pseudomonas vaccines, no vaccine has been licensed. Nevertheless, there have been many advances in this field, including a better understanding of the host immune response and the biology of P. aeruginosa. Multiple antigens and adjuvants have been investigated with varying results. Although the most effective protective response remains to be established, it is clear that a polarised Th2 response is sub-optimal, and a mixed Th1/Th2 or Th1/Th17 response appears beneficial. This comprehensive review collates the current understanding of the complexities of P. aeruginosa-host interactions and its implication in vaccine design, with a view to understanding the current state of Pseudomonal vaccine development and the direction of future efforts. It highlights the importance of the incorporation of appropriate adjuvants to the protective antigen to yield optimal protection.

A Live Salmonella Vaccine Delivering PcrV through the Type III Secretion System Protects against Pseudomonas aeruginosa

The Gram-negative bacterium Pseudomonas aeruginosa is an important opportunistic pathogen that causes infections in cystic fibrosis and hospitalized patients. Therapeutic treatments are limited due to the emergence and spread of new antibiotic-resistant strains. In this context, the development of a vaccine is a priority. Here, we used an attenuated strain of Salmonella enterica serovar Typhimurium as a vehicle to express and deliver the Pseudomonas antigen PcrV. This vaccine induced the generation of specific antibodies in mice and protected them from lethal infections with P. aeruginosa. This is an important step toward the development of an effective vaccine for the prevention of infections caused by P. aeruginosa in humans.

Pseudomonas aeruginosa is a common Gram-negative opportunistic pathogen that is intrinsically resistant to a wide range of antibiotics. The development of a broadly protective vaccine against P. aeruginosa remains a major challenge. Here, we used an attenuated strain of Salmonella enterica serovar Typhimurium as a vehicle to express P. aeruginosa antigens. A fusion between the S. enterica type III secretion effector protein SseJ and the P. aeruginosa antigen PcrV expressed under the control of the sseA promoter was translocated by Salmonella into host cells in vitro and elicited the generation of specific antibodies in mice. Mice immunized with attenuated Salmonella expressing this fusion had reduced bacterial loads in the spleens and lungs and lower serum levels of proinflammatory cytokines than control mice after P. aeruginosa infection. Importantly, immunized mice also showed significantly enhanced survival in this model. These results suggest that type III secretion effectors of S. enterica are appropriate carriers in the design of a live vaccine to prevent infections caused by P. aeruginosa.

IMPORTANCE The Gram-negative bacterium Pseudomonas aeruginosa is an important opportunistic pathogen that causes infections in cystic fibrosis and hospitalized patients. Therapeutic treatments are limited due to the emergence and spread of new antibiotic-resistant strains. In this context, the development of a vaccine is a priority. Here, we used an attenuated strain of Salmonella enterica serovar Typhimurium as a vehicle to express and deliver the Pseudomonas antigen PcrV. This vaccine induced the generation of specific antibodies in mice and protected them from lethal infections with P. aeruginosa. This is an important step toward the development of an effective vaccine for the prevention of infections caused by P. aeruginosa in humans.

Pseudomonas aeruginosa mannose-sensitive hemagglutinin inhibits proliferation and invasion via the PTEN/AKT pathway in HeLa cells

We investigated the effects of Pseudomonas aeruginosa mannose-sensitive hemagglutinin (PA-MSHA) on the proliferation and invasion of human cervical cancer cell lines, as well as the molecular pathways underlying these effects. MTT cell proliferation assays revealed a time- and concentration-dependent cytotoxic effect of PA-MSHA on HeLa cells but not H8 cells. Flow cytometry with propidium iodide and annexin-V-fluorescein isothiocyanate labeling (FITC) indicated that various concentrations of PA-MSHA could induce apoptosis and G2-M cell cycle arrest in HeLa cells. PA-MSHA also impaired the migration and invasion abilities of HeLa cells in Wound healing and Transwell invasion assays. Western blot results demonstrated that PA-MSHA reduced the expression of p-AKT, p-GSK3β, BCL-2, Vimentin and β-catenin, but increased the levels of PTEN, BAD, BAX and E-cadherin in HeLa cells. Importantly, PTEN siRNA induced the activity of p-AKT, while PA-MSHA partly inhibited this induction, indicating that PA-MSHA may reduce the cell proliferation and invasion potential by activating PTEN and thus inhibiting the AKT pathway in vitro. These data suggest the potential application of PA-MSHA to the treatment of human cervical cancer.

Immunization with outer membrane proteins (OprF and OprI) and flagellin B protects mice from pulmonary infection with mucoid and nonmucoid Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium, which considered as a common cause of nosocomial infection and life-threatening complications in immunocompromized and cystic fibrosis patients. Here, we evaluate the protective effect of recombinant vaccines composed of outer membrane proteins OprF and OprI alone or in combination with flagellin B against mucoid and nonmucoid pseudomonas infection.

METHODS

BALB/C mice were immunized subcutaneous using OprF and OprI with or without flagellin B and antibody titers were determined. Serum bactericidal and opsonophagocytosis activities of immunized and control sera were estimated against mucoid and nonmucoid pseudomonas strains. Lung tissue sections from immunized and nonimmunized mice were analyzed and the levels of peripheral neutrophils infiltration into the lung and tissue inflammation were scored.

RESULTS

Subcutaneous immunization using OprF and OprI with or without flagellin B elicited higher antibody titers against OprF, OprI, and flagellin B. The produced antibodies successfully opsonized both mucoid and nonmucoid strains with subsequent activation of the terminal pathway of complement that enhances killing of nonmucoid strains via complement-mediated lysis. Furthermore, opsonized mucoid and nonmucoid strains showed enhanced opsonophagocytosis via human peripheral neutrophils, a mechanism that kills P. aeruginosa when complement mediated lysis is not effective especially with mucoid strains. Immunized mice also showed a significant prolonged survival time, lower bacteremia, and reduced lung damage when compared with control nonimmunized mice.

CONCLUSION

Our data showed that mice immunized with OprF/OprI or OprF/OprI and flagellin B are significantly protected from infection caused by mucoid and nonmucoid strains of P. aeruginosa.

Pseudomonas aeruginosa-mannose-sensitive hemagglutinin inhibits epidermal growth factor receptor signaling pathway activation and induces apoptosis in bladder cancer cells in vitro and in vivo

OBJECTIVES

Pseudomonas aeruginosa-mannose-sensitive hemagglutinin (PA-MSHA), a peritrichous P. aeruginosa strain with MSHA fimbriae, has been shown to be a valuable anticancer drug in many kinds of cancers. However, the effect of PA-MSHA on bladder cancer has not been elucidated. In this study, we focused on the antitumor activities and related mechanisms of PA-MSHA on bladder cancer in vitro and in vivo.

MATERIALS AND METHODS

SV-40-immortalized normal uroepithelial cells (SV-HUC-1) and human bladder cancer cell lines (T24, 5637, and HT-1376) were treated with PA-MSHA or PA (heat-killed P. aeruginosa). At first, the effect of PA-MSHA on cancer cell proliferation was measured using Cell Counting Assay Kit-8 (CCK-8), whereas the changes of cell morphology were observed by transmission electron microscopy. The early apoptosis induced by PA-MSHA was evaluated by flow cytometry, and the expression level of apoptosis-related molecules was detected using Western blot assay. We then investigated the activation of the epidermal growth factor receptor signaling pathway stimulated by PA-MSHA; the expression and phosphorylation of several key regulators involved in the EGFR signaling pathway were detected. At last, xenograft tumor in nude mice was used to further investigate the antitumor effect of PA-MSHA in vivo.

RESULTS

Our results showed that PA-MSHA could efficiently inhibit proliferation and induce apoptosis in human bladder cancer cell lines. Furthermore, cells stimulated with PA-MSHA exhibited an inactivation of EGFR signaling. In vivo, PA-MSHA treatment significantly suppressed tumor growth and induced apoptosis in xenografts tumor in nude mice.

CONCLUSIONS

PA-MSHA could efficiently inhibit proliferation and induce apoptosis in human bladder cancer cells in vitro and in vivo, which is associated with the inactivation of EGFR signaling pathway, and it might be used as a potential therapeutic agent for bladder cancer.

Recent developments for Pseudomonas vaccines

Infections with Pseudomonas aeruginosa are a major health problem for immune-compromised patients and individuals with cystic fibrosis. A vaccine against: P. aeruginosa has long been sought after, but is so far not available. Several vaccine candidates have been assessed in experimental animals and humans, which include sub-cellular fractions, capsule components, purified and recombinant proteins. Unique characteristics of the host and the pathogen have complicated the vaccine development. This review summarizes the current state of vaccine development for this ubiquitous pathogen, in particular to provide mucosal immunity against infections of the respiratory tract in susceptible individuals with cystic fibrosis.

Insights into acinetobacter war-wound infections, biofilms, and control

OBJECTIVE

Multidrug-resistant Acinetobacter baumannii is associated with a wide spectrum of infectious diseases ranging from nosocomial, community-acquired infections to those acquired following war or natural disaster. Especially to military personnel with war wounds, Acinetobacter infection is a formidable threat. The treatment has become exceedingly difficult, not only because the bacterium can develop extensive antimicrobial resistance but because it also forms biofilms that are resistant to host defense and antimicrobial treatment. Such causative factors as biofilm formation and resistance are highly likely to lead to nonhealing wounds. This review, although focused on A baumannii infections, aims to summarize what is known about immunization protection against wound biofilm infections and to apply such understanding in exploring the unknown area of war-wound infection protection.

DATA SOURCES AND STUDY SELECTION

Publications were searched and selected through http://www.pubmed.gov by using the key words Acinetobacter baumannii, bacteria, war wounds, burn wounds, wound infections, biofilms, vaccines, and immunization. The literature selected was categorized according to the subheadings within this article.

CONCLUSIONS

It is imperative to develop such effective measures as active and passive immunization to control multidrug-resistant and tenacious A baumannii infections and to prevent nonhealing wounds. The authors' understanding in immunization against burn wound-related infections by the model bacteria will facilitate research progress in the poorly explored area of immunization against war-wound biofilm infections.

PA-MSHA inhibits proliferation and induces apoptosis through the up-regulation and activation of caspases in the human breast cancer cell lines

To investigate the effects of PA-MSHA (Pseudomonas aeruginosa-mannose sensitive hemagglutinin) on inhibiting proliferation of breast cancer cell lines and to explore its mechanisms of action in human breast cancer cells. MCF-10A, MCF-7, MDA-MB-468, and MDA-MB-231HM cells were treated with PA-MSHA or PA (Heat-killed P. aeruginosa) at different concentrations and different times. Changes of cell super-microstructure were observed by transmission electron microscopy. Cell cycle distribution and apoptosis induced by PA-MSHA were measured by flow cytometry (FCM) with PI staining, ANNEXIN V-FITC staining and Hoechst33258 staining under fluorescence microscopy. Western blot was used to evaluate the expression level of apoptosis-related molecules. A time-dependent and concentration-dependent cytotoxic effect of PA-MSHA was observed in MDA-MB-468 and MDA-MB-231HM cells but not in MCF-10A or MCF-7 cells. The advent of PA-MSHA changed cell morphology, that is to say, increases in autophagosomes, and vacuoles in the cytoplasm could also be observed. FCM with PI staining, ANNEXIN V-FITC and Hoechst33258 staining showed that the different concentrations of PA-MSHA could all induce the apoptosis and G(0)-G(1) cell cycle arrest of breast cancer cells. Cleaved caspase 3, 8, 9, and Fas protein expression levels were strongly associated with an increase in apoptosis of the breast cancer cells. There was a direct relationship with increased concentrations of PA-MSHA but not of PA. Completely different from PA, PA-MSHA may impart antiproliferative effects against breast cancer cells by inducing apoptosis mediated by at least a death receptor-related cell apoptosis signal pathway, and affecting the cell cycle regulation machinery.

Protection against Pseudomonas aeruginosa lung infection in mice by recombinant OprF-pulsed dendritic cell immunization

BACKGROUND

The Pseudomonas aeruginosa major constitutive outer membrane porin protein F (OprF) has been shown to be a protective antigen and was previously used to activate an immunological response in a mouse model of lung pneumonia. The purpose of our study was to demonstrate the ability of mouse dendritic cells pulsed with purified or recombinant OprF to protect mice against P. aeruginosa infection and inflammation.Both native (n-OprF), isolated and purified from PAO1 bacterial strain, and recombinant (histidin-conjugated) OprF (His-OprF), obtained by cloning of the oprF gene into the pET28a expression vector, were used to stimulate dendritic cells in vitro before adoptive transfer into prospective recipient mice with P. aeruginosa pulmonary infection.

RESULTS

Similar to n-OprF, His-OprF activated dendritic cells in vitro, inducing the costimulatory molecule expression as well as cytokine production. Upon adoptive transfer in vivo, porin-pulsed dendritic cells (DCs) induced Th1-mediated resistance to infection and associated inflammatory pathology caused by either the PAO1 strain or a clinically-isolated mucoid strain.

CONCLUSIONS

This study highlights the pivotal contribution of DCs to vaccine-induced protection against P. aeruginosa infection and associated inflammation.

Opr86 is essential for viability and is a potential candidate for a protective antigen against biofilm formation by Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that is one of the most refractory to therapy when it forms biofilms in the airways of cystic fibrosis patients. To date, studies regarding the production of an immunogenic and protective antigen to inhibit biofilm formation by P. aeruginosa have been superficial. The previously uncharacterized outer membrane protein (OMP) Opr86 (PA3648) of P. aeruginosa is a member of the Omp85 family, of which homologs have been found in all gram-negative bacteria. Here we verify the availability of Opr86 as a protective antigen to inhibit biofilm formation by P. aeruginosa PAO1 and several other isolates. A mutant was constructed in which Opr86 expression could be switched on or off through a tac promoter-controlled opr86 gene. The result, consistent with previous Omp85 studies, showed that Opr86 is essential for viability and plays a role in OMP assembly. Depletion of Opr86 resulted in streptococci-like morphological changes and liberation of excess membrane vesicles. A polyclonal antibody against Opr86 which showed reactivity to PAO1 cells was obtained. The antibody inhibited biofilm formation by PAO1 and the other clinical strains tested. Closer examination of early attachment revealed that cells treated with the antibody were unable to attach to the surface. Our data suggest that Opr86 is a critical OMP and a potential candidate as a protective antigen against biofilm formation by P. aeruginosa.

Application of vaccine technology to prevention of Pseudomonas aeruginosa infections

Development of an effective vaccine against the multiple presentations of Pseudomonas aeruginosa infection, including nosocomial pneumonia, bloodstream infections, chronic lung infections in cystic fibrosis patients and potentially sight-threatening keratitis in users of contact lenses, is a high priority. As with vaccine development for any pathogen, key information about the most effective immunologic effectors of immunity and target antigens needs to be established. For P. aeruginosa, although there is a role for cell-mediated immunity in animals following active vaccination, the bulk of the data indicate that opsonically-active antibodies provide the most effective mediators of acquired immunity. Major target antigens include the lipopolysaccharide O-polysaccharides, cell-surface alginate, flagella, components of the Type III secretion apparatus and outer membrane proteins with a potentially additive effect achieved by including immune effectors to toxins and proteases. A variety of active vaccination approaches have the potential for efficacy such as vaccination with purified or recombinant antigens incorporating multiple epitopes, conjugate vaccines incorporating proteins and carbohydrate antigens, and live attenuated vaccines, including heterologous antigen delivery systems expressing immunogenic P. aeruginosa antigens. A diverse range of passive immunotherapeutic approaches are also candidates for effective immunity, with a variety of human monoclonal antibodies described over the years with good preclinical efficacy and some early Phase I and II studies in humans. Finding an effective active and/or passive vaccination strategy for P. aeruginosa infections could be realized in the next 5 to 10 years, but will require that advances are made in the understanding of antigen expression and immune effectors that work in different human tissues and clinical settings, and also require a means to validate that clinical outcomes achieved in Phase III trials represent meaningful advances in management and treatment of P. aeruginosa infections.

Effect of anti-OprF-OprI immunoglobulin on APACHE II score in a porcine two-hit model of hemorrhagic shock/resuscitation and pseudomonas aeruginosa sepsis

BACKGROUND

Up to now, randomized clinical trials of treatment of bacterial sepsis with immunoglobulins show conflicting results. This paper investigates the effect of prophylactic immunization with anti-OprF-OprI antiserum on the APACHE II score in a clinically relevant two-hit model of hemorrhagic shock/resuscitation followed by Pseudomonas aeruginosa sepsis in pigs.

METHODS

Twenty-three German Landrace-Hybrid pigs underwent chronic implantation of vascular catheters (internal and external jugular vein, carotic and pulmonary artery), hemorrhagic shock (mean blood loss 40% of estimated blood volume) for 45 min, followed by resuscitation with crystalloid, colloid, and shed blood. Randomization was to a control group (no immunization, n=6), an F-I group (50 mg/kg i.p. anti-OprF-OprI immunoglobulin, n=6), an S group (50 mg/kg i.p. unspecific porcine immunoglobulins, n=6), and a PS group (50 mg/kg i.p. immunoglobulin against the antigens of heat-killed P. aeruginosa, n=5). After at least 18 h for recovery from anesthesia, the pigs underwent a continuous intravenous infusion of P. aeruginosa for 48 h. Thereafter, the animals were monitored for another 48 h and then dissected.

RESULTS

The APACHE II score significantly increased from baseline value in all groups during bacterial challenge. However, there were no between-group differences in APACHE II score. In contrast, pigs of the F-I and PS groups showed significant lower lung concentrations of P. aeruginosa (p<0.05 vs. control group) at autopsy.

CONCLUSION

These experimental data suggest that under comparable clinical conditions, a prophylactic immunization with anti-OprF-OprI immunoglobulin would not have an overall benefit to patients with P. aeruginosa sepsis.

Pseudomonas aeruginosa: the potential to immunise against infection

Pseudomonas aeruginosa remains a serious pathogen for specific cohorts of patients where chronic infection is a poor prognostic indicator, such as those with cystic fibrosis, burn wounds or those who are immunocompromised. Significant disease burden is associated with a diverse spectrum of both nosocomial and community-acquired infections. To date, vaccines against P. aeruginosa have shown limited and often conflicting efficacy data, especially against heterologous strains, which are increasingly identified as co-colonisers of biofilms. While few studies have gone beyond Phase II clinical trials, a particular concern is the ability of P. aeruginosa to evade the immune system while provoking an immune response that contributes to the destructive nature of infection. Therefore, vaccine development needs to focus on preventing attachment and colonisation, as well as preventing conversion to a mucoid phenotype that is characteristic of the chronic condition that promotes pathology.

Recombinant OprF-OprI as a vaccine against Pseudomonas aeruginosa infections

A vaccine against Pseudomonas aeruginosa based on recombinant outer membranes has been developed. After intramuscularly injecting into patients with severe burns, antibodies against P. aeruginosa were induced. Vaccination was well tolerated. Intranasal application of the vaccine into volunteers, induced specific s-IgA antibodies. We conclude that the newly developed vaccine may be suitable for protection of the main risk groups of P. aeruginosa infections. In particular, for the protection of burn patients and patients with cystic fibrosis.

Pseudomonas immunotherapy: a historical overview

The historic development of vaccines to be used as immunotherapy for Pseudomonas aeruginosa infections, in various patient populations, is reviewed. Commentary is offered concerning the relevance of each approach in light of our current understanding of the pathological process of these infections.

Application of proteomics to Pseudomonas aeruginosa

The recent completion of the Pseudomonas Genome Project, in conjunction with the Pseudomonas Community Annotation Project (PseudoCAP) has fast-tracked our ability to apply the tools encompassed under the term 'proteomics' to this pathogen. Such global approaches will allow the research community to answer long-standing questions regarding the ability of Pseudomonas aeruginosa to survive diverse habitats, its high intrinsic resistance to antibiotics and its pathogenic nature towards humans. Proteomics provides an array of tools capable of confirming the expression of Open Reading Frames (ORF), the relative levels of their expression, the environmental conditions required for this expression and the sub-cellular location of the encoded gene-products. Since proteins are important cellular effectors, the biological questions we pose can be defined in terms of changes in protein expression detectable by separation to purity using two-dimensional gel electrophoresis (2-DGE) and relation to gene sequences via mass spectrometry. As such, we can compare strains with well-characterized phenotypic differences, growth under a variety of stresses, protein interactions and complexes and aid in defining proteins of unknown function. While the complete genome has only recently been finished, a number of studies have already utilized this information and examined various protein gene-products using proteomics. This review summarizes the application of proteomics to P. aeruginosa and highlights potential areas of future research, including overcoming the traditional technical limitations associated with 2-DGE. More focused approaches that target sub-cellular fractions ('sub-proteomes') prior to 2-DGE can provide further functional information. A review of current and previous proteomic projects on P. aeruginosa is presented, as well as theoretical considerations of the importance of sub-proteomic approaches to enhance these investigations.

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.

Protection against Pseudomonas aeruginosa chronic lung infection in mice by genetic immunization against outer membrane protein F (OprF) of P. aeruginosa

The Pseudomonas aeruginosa major constitutive outer membrane porin protein OprF, which has previously been shown to be a protective antigen, was targeted as a DNA vaccine candidate. The oprF gene was cloned into plasmid vector pVR1020, and the plasmid vaccines were delivered to mice by biolistic (gene gun) intradermal inoculation. Antibody titers in antisera from immunized mice were determined by enzyme-linked immunosorbent assay, and the elicited antibodies were shown to be specifically reactive to OprF by immunoblotting. The immunoglobulin G (IgG) immune response was predominantly of the IgG1 isotype. Sera from DNA vaccine-immunized mice had significantly greater opsonic activity in opsonophagocytic assays than did sera from control mice. Following the initial immunization and two consecutive boosts, each at 2-week intervals, protection was demonstrated in a mouse model of chronic pulmonary infection by P. aeruginosa. Eight days postchallenge, both lungs were removed and examined. A significant reduction in the presence of severe macroscopic lesions, as well as in the number of bacteria present in the lungs, was seen. Based on these findings, genetic immunization with oprF has potential for development as a vaccine to protect humans against infection by P. aeruginosa.