Pseudomonas immunotherapy: a historical overview

Exploiting immunopotential PAPI-1 encoded type IVb major pilin targeting Pseudomonas aeruginosa

Pseudomonas aeruginosa (P. aeruginosa) significantly contributes to nosocomial infections and necessitates research into novel treatment methods. For the first time, this research evaluated the immunoprotective potential of recombinant PAPI-1 encoded type IV pili targeting P. aeruginosa in BALB/C mice. The target sequence was identified, and a PilS2-encoding vector was constructed. The vector was then expressed and purified in E. coli BL21 (DE3). The PilS2 protein was inoculated into BALB/C mice in four groups, with or without alum, to measure total IgG, its subclasses, and cytokines. MTT and opsonophagocytosis tests were used to examine the immunological response. PilS2, especially when paired with alum, boosts the humoral immune response by enhancing IgG and IL-4 levels. However, PilS2 did not affect IL-17 or IFN-γ and only increased lymphocyte proliferation. Antibodies targeting PilS2 increased phagocytic cell death of P. aeruginosa by over 95 %, indicating possible therapies for P. aeruginosa infections. Our study on the immunopotentiation of P. aeruginosa PilS2 paves the way for pilin-based vaccines and immunotherapy targeting this pathogen.

A chimeric vaccine targeting Pseudomonas aeruginosa virulence factors protects mice against lethal infection

Pseudomonas aeruginosa is an important and hazardous nosocomial pathogen in respiratory tract infections and rapidly achieves antibiotic resistance, so it is necessary to develop an effective vaccine to combat the infection. The Type III secretion system (T3SS) protein P. aeruginosa V-antigen (PcrV), outer membrane protein F (OprF), and two kinds of flagellins (FlaA and FlaB) all play important roles in the pathogenesis of P. aeruginosa lung infection and its spread into deeper tissues. In a mouse acute pneumonia model, the protective effects of a chimer vaccine including PcrV, FlaA, FlaB, and OprF (PABF) protein were investigated. PABF immunization prompted robust opsonophagocytic titer of IgG antibodies and decreased bacterial burden, and improved survival afterward intranasal challenge with ten times 50% lethal doses (LD50) of P. aeruginosa strains, indicating its broad-spectrum immunity. Moreover, these findings showed a promise chimeric vaccine candidate to treat and control P. aeruginosa infections.

Bioinformatics analyses for the designation of a hybrid protein against urinary tract infections caused by Pseudomonas aeruginosa and investigation of the presence of pre-existing antibodies in infected humans

Pseudomonas aeruginosa is an important pathogen causing urinary tract infections (UTIs) and resistance to antibiotics has increased the need for a vaccine against this bacterium. P. aeruginosa V-antigen (PcrV), which is a component of the type III secretion system, delivers exoenzymes such as exoenzyme S (ExoS) into the host cells. In the present study, we aimed to design and express a hybrid protein composed of PcrV and ExoS from P. aeruginosa using bioinformatics. Finally, pre-existing antibodies were evaluated in sera collected from patients with UTI. The prediction results showed that the hybrid protein ExoS.PcrV had a C-score of -0.85 and Z-score of -5.55 versus C-score of -2.93 and Z-score of -2.65 for PcrV.ExoS. Based on BepiPred and ABCpred, 15 and 14 linear B-cell epitopes, as well as five conformational epitopes were identified in ExoS.PcrV. The interaction between the protein and immune receptor was validated in silico. Molecular docking indicated that the hybrid protein interacted strongly with Toll-like receptor 2. ExoS.PcrV was expressed in pET28a-BL21 and purified with a size of 57 kD by Nickel resins. The protein reacted with all sera collected from humans infected with P. aeruginosa following Western blot. The infected patients produced significantly higher IgG levels against the protein compared to the control as indicated by ELISA. The protein ExoS.PcrV was determined as a promising candidate against UTI caused by P. aeruginosa and the presence of pre-existing antibodies indicated the advantage of the hybrid protein. Evaluation of the efficacy of hybrid protein is ongoing in mice model. Communicated by Ramaswamy H. Sarma.

Immunization against Pseudomonas aeruginosa using Alg-PLGA nano-vaccine

OBJECTIVES

Pseudomonas aeruginosa is the bacterium that causes of pulmonary infection among chronically hospitalized patients. Alginate is a common surface antigen of P. aeruginosa with a constant structure that which makes it an appropriate target for vaccines. In this study, P. aeruginosa alginate was conjugated with to PLGA nanoparticles, and its immunogenicity was characterized as a vaccine.

MATERIALS AND METHODS

Alginate was isolated from a mucoid strain of P. aeruginosa and conjugated with to PLGA with˝ N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride ˝= ˝EDAC˝ and N-Hydroxysuccinimide (NHS). Chemical characterization of prepared nano-vaccine was performed using FTIR Spectroscopy, Zetasizer, and Atomic Force Microscopy (AFM). The immunogenicity of this nano-vaccine was evaluated through intramuscular injection into BALB/c mice. Four groups of mice were subjected to the injection of alginate-PLGA, and two weeks after the last administration step, opsonophagocytosis assay, IgG detection, challenge, and cytokine determination via ELISA were carried out.

RESULTS

Alginate-PLGA conjugation was corroborated by FTIR, Zetasizer, and AFM. The ELISA consequence showed that alginate was prospering in the instigation of the humoral immunity.The immunogenicity enhanced against the alginate-PLGA. Remarkably diminished bacterial titer in the spleen of the immunized mice posterior to challenge with PAO1 strain in comparison with the alginate alone and control groups.

CONCLUSION

The bacterial burden in the spleen significantly decreased after the challenge (P<0.05). The opsonic activity was significantly increased in the alginate- PLGA group (P<0.05).

Immunopotentiation of the engineered low-molecular-weight pilin targeting Pseudomonas aeruginosa: A combination of immunoinformatics investigation and active immunization

Several vaccine candidates have been introduced for immunization against Pseudomonas aeruginosa strains. Despite extensive efforts in recent decades, there is no accurate immunogenic candidate against this pathogen in the market yet. Due to the rapid increase in several drug-resistant strains, P. aeruginosa has caused various health concerns worldwide. It encodes many specific virulence features, which can be used as an appropriate vaccine candidate. The primary stage of the pathogenesis of P. aeruginosa is the expression of many dynamic adhesive molecules, such as type IV pili (T4P), which acts as a principal colonization factor. It has been confirmed that three different subtypes of T4P, including type IVa (T4aP), type IVb (T4bP) and tight adherence (Tad) pili are expressed by P. aeruginosa. The IVa fimbriae type is almost the main cause of challenges to design an effective pili based-immunotherapy method. Nevertheless, in terms of heterogeneity, variability and hidden conserved binding site of T4aP, this attitude has been remained controversial and there is no permitted human study based on IVa pilin commercially. The engineered synthetic peptide-based vaccines are highly talented to mimic the target. In this research, for the first time, some dominant immunogenic features of the Flp protein, such as both B- and T-cell-associated epitopes, presence of IgE-associated epitopes, solvent-accessible surface area were evaluated by analytical immunoinformatics methods. In addition, we designed the engineered Flp pilin as an effective immunogenic substance against several clinically important P. aeruginosa strains. Moreover, by practical active immunization approaches, the humoral and cellular immune response against the extremely conserved region of the engineered synthetic Flp (EFlp) formulated in Montanide ISA 266 compared to the control group. The results of active immunization against EFlp significantly signified that EFlp-Montanide ISA 266 (EFLP-M) strongly could induce both humoral and cellular immune responses. We concluded that Flp pilin has therapeutic potential against numerous clinically significant P. aeruginosa strains and can be served as a novel immunogen for further investigations for development of effective immunotherapy methods against P. aeruginosa as a dexterous pathogen.

Inhibitory effects of Cinnamaldehyde, Carvacrol, and honey on the expression of exoS and ampC genes in multidrug-resistant Pseudomonas aeruginosa isolated from burn wound infections

This study aimed to evaluate the effects of Cinnamaldehyde, Carvacrol, and honey either alone or in combinations on the expression of exoS and ampC genes in multidrug-resistant (MDR) P. aeruginosa isolates. Thirty-five P. aeruginosa isolates were recovered from burn wound infections of patients admitted to the burn ward of Besat hospital of Hamadan, Iran, during 2018. Antibiotic susceptibility testing was performed using the Kirby-Bauer disk diffusion method to identify MDR isolates. The antibacterial effects of Cinnamaldehyde, Carvacrol, and honey either alone or in combinations with each other were compared to Imipenem (as the control group) using the broth dilution method. The expressions of exoS and ampC genes were determined in bacteria treated with sub-minimum inhibitory concentration (MIC) of the ternary combination of Cinnamaldehyde, Carvacrol, and honey by Real-Time-PCR. The data were analyzed using SPSS software applying student t-test, Kruskal-Wallis, and Mann-Whitney U tests. The P-value less than 0.05 was considered as statistically significant. The average MICs of Cinnamaldehyde, Carvacrol, and honey were 0.82-0.01, 0.01-0.6, and 62.5-250 μg/mL, respectively. The average MIC of the mentioned compounds was 430 times lower than that of Imipenem. A synergistic effect was detected between these drugs against 70% of the isolates. At sub-MIC concentration, the triple combination of Cinnamaldehyde, Carvacrol, and honey reduced the expressions of exoS and ampC genes by 6.12 and 2.85 folds, respectively. The combination of Cinnamaldehyde, Carvacrol, and honey showed a higher antibacterial effect than Imipenem. However, it needs confirmation with more isolates.

Anti-PcrV IgY antibodies protect against Pseudomonas aeruginosa infection in both acute pneumonia and burn wound models

Pseudomonas aeruginosa is a common nosocomial pathogen in burn patients, and rapidly acquires antibiotic resistance; thus, developing an effective therapeutic approach is the most promising strategy for combating infection. Type III secretion system (T3SS) translocates bacterial toxins into the cytosol of the targeted eukaryotic cells, which plays important roles in the virulence of P. aeruginosa infections in both acute pneumonia and burn wound models. The PcrV protein, a T3SS translocating protein, is required for T3SS function and is a well-validated target in animal models of immunoprophylactic strategies targeting P. aeruginosa. In the present study, we evaluated the protective efficacy of chicken egg yolk antibodies (IgY) raised against recombinant PcrV (r-PcrV) in both acute pneumonia and burn wound models. R-PcrV protein was generated by expressing the pcrV gene (cloned in pET-28a vector) in E. coli BL-21. Anti-PcrV IgY was obtained by immunization of hen. Anti-PcrV IgY induced greater protection in P. aeruginosamurine acute pneumonia and burn wound models than control IgY (C-IgY) and PBS groups. Anti-PcrV IgY improved opsonophagocytic killing and inhibition of bacterial invasion of host cells. Taken together, our data provide evidence that anti-PcrV IgY can be a promising therapeutic candidate for combating P. aeruginosa infections.

A trivalent vaccine consisting of "flagellin A+B and pilin" protects against Pseudomonas aeruginosa infection in a murine burn model

Pseudomonas aeruginosa is a common nosocomial pathogen in burn patients, and rapidly achieves antibiotic resistance, and thus, developing an effective vaccine is critically important for combating P. aeruginosa infection. Flagella and pili play important roles in colonization of P. aeruginosa at the burn wound site and its subsequent dissemination to deeper tissue and organs. In the present study, we evaluated protective efficacy of a trivalent vaccine containing flagellins A and B (FlaA + FlaB) + pilin (PilA) in a murine burn model of infection. "FlaA + FlaB + PilA" induced greater protection in P. aeruginosa murine burn model than the single components alone, and it showed broad immune protection against P. aeruginosa strains. Immunization with "FlaA + FlaB + PilA" induced strong opsonophagocytic antibodies and resulted in reduced bacterial loads, systemic IL-12/IL-10 cytokine expression, and increased survival after challenge with three times lethal dose fifty (LD50) of P. eruginosa strains. Moreover, the protective efficacy of "FlaA + FlaB + PilA" vaccination was largely attributed to specific antibodies. Taken together, these data further confirm that the protective effects of "FlaA + FlaB + PilA" vaccine significantly enhance efficacy compared with antibodies against either mono or divalent antigen, and that the former broadens the coverage against P. eruginosa strains that express two of the three antigens.

A metal free mild and green approach for tandem opening of 4,6-O-benzylidene acetals to their corresponding 6-O-acetyl derivatives: Application in the synthesis of a trisaccharide using one-pot glycosylation reactions

An efficient and high yielding reaction for tandem opening of 4,6-O-benzylidene derivatives (gluco, galacto, manno, 2-phthalimido-2-deoxy glucosides) to their corresponding 6-O-acetyl derivatives has been established under metal free condition using 60% solution of aqueous acetic acid (v/v). The reaction is equally pertinent for large scale synthesis and also for disaccharide glycosides. Its application for the construction of a building block towards synthesis of a trisaccharide part related to Pseudomonas aeruginosa utilizing one-pot glycosylation reactions has also been described.

Genome-Based Approach Delivers Vaccine Candidates Against Pseudomonas aeruginosa

High incidence, severity and increasing antibiotic resistance characterize Pseudomonas aeruginosa infections, highlighting the need for new therapeutic options. Vaccination strategies to prevent or limit P. aeruginosa infections represent a rational approach to positively impact the clinical outcome of risk patients; nevertheless this bacterium remains a challenging vaccine target. To identify novel vaccine candidates, we started from the genome sequence analysis of the P. aeruginosa reference strain PAO1 exploring the reverse vaccinology approach integrated with additional bioinformatic tools. The bioinformatic approaches resulted in the selection of 52 potential antigens. These vaccine candidates were conserved in P. aeruginosa genomes from different origin and among strains isolated longitudinally from cystic fibrosis patients. To assess the immune-protection of single or antigens combination against P. aeruginosa infection, a vaccination protocol was established in murine model of acute respiratory infection. Combinations of selected candidates, rather than single antigens, effectively controlled P. aeruginosa infection in the in vivo model of murine pneumonia. Five combinations were capable of significantly increase survival rate among challenged mice and all included PA5340, a hypothetical protein exclusively present in P. aeruginosa. PA5340 combined with PA3526-MotY gave the maximum protection. Both proteins were surface exposed by immunofluorescence and triggered a specific immune response. Combination of these two protein antigens could represent a potential vaccine to prevent P. aeruginosa infection.

The study of formulated Zoush ointment against wound infection and gene expression of virulence factors Pseudomonas aeruginosa

BACKGROUND

The outbreak of MDR and XDR strains of Pseudomonas aeruginosa and increased resistance to infection in burn patients recommend the issue of infection control. In this research, we study ZOUSH herbal ointment for gene silencing of Pseudomonas aeruginosa.

METHODS

The herbal ZOUSH ointment was formulated by alcoholic extracts of plants Satureja khuzestaniea, Zataria multiflora, Mentha Mozaffariani Jamzad, honey, and polyurethane. The MIC and disk diffusion tests were examined by single, binary, tertiary and five compounds. Three-week-old mice were considered to be second-degree infections by Pseudomonas aeruginosa. During the interval of 5 days, cultures were done from the liver, blood, and wound by four consecutive quarters and counting of Pseudomonas aeruginosa was reported in the liver. In this study, silver sulfadiazine ointments and Akbar were used as a positive control. The gene gyrA reference was used as the control. Real-time RT-PCR results were evaluated based on Livak as the comparative Ct method.

RESULTS

The In vitro results indicated that wound infection was improved by healing wound size in the treatment groups compared to control treatment group. In this research, the changes in gene expression were evaluated by molecular technique Real-time RT-PCR. The results showed downregulation exoS, lasA, and lasB after treatment with ZOUSH ointment. SPSS Analyses showed that reduction of expressions in genes exoS, lasA and lasB after treatment with ZOUSH ointment were significantly meaningful (p < 0.05).

CONCLUSION

Our study showed that ZOUSH ointment has the positive effect for gene silencing Pseudomonas aeruginosa in the mouse model with the second-degree burn. The positive effects decreased in the number of bacteria by reducing the expression of virulence bacteria genes as exoS, lasA and lasB and improvement of wound healing.

Immunization with Bivalent Flagellin Protects Mice against Fatal Pseudomonas aeruginosa Pneumonia

Pseudomonas aeruginosa lung infections present a major challenge to healthcare systems worldwide because they are commonly associated with high morbidity and mortality. Here, we demonstrate the protective efficacy of type a and b flagellins (bivalent flagellin) against acute fatal pneumonia in mice. Mice immunized intranasally with a bivalent flagellin vaccine were challenged by different flagellated strains of P. aeruginosa in an acute pneumonia model. Besides the protective effect of the vaccine, we further measured the host innate and cellular immunity responses. The immunized mice in our study were protected against both strains. Remarkably, active immunization with type a or b flagellin significantly improved survival of mice against heterologous strain compared to flagellin a or b antisera. We also showed that after an intranasal challenge by P. aeruginosa strain, neutrophils are recruited to the airways of vaccinated mice, and that the bivalent flagellin vaccine was proved to be protective by the generated CD4⁺IL-17⁺ Th17 cells. In conclusion, bivalent flagellin vaccine can confer protection against different strains of P. aeruginosa in an acute pneumonia mouse model by eliciting effective cellular and humoral immune responses, including increased IL-17 production and improved opsonophagocytic killing.

Immunogenicity of a fusion protein containing PilQ and disulphide turn region of PilA from Pseudomonas aeruginosa in mice

Interference with bacterial adhesion is a new means to prevent or treat bacterial infections. In this experimental study we evaluated the immunogenic properties of a chimeric protein composed of PilQ and disulphide turn region of PilA from Pseudomonas aeruginosa in mice as an anti-adhesion based vaccine. First of all, a chimeric bivalent protein composed of PilQ and PilA was constructed and following subcutaneous immunization with merely the purified protein or in its admixed form with alum, the immunogenicity of the chimeric antigen was assessed in BALB/c mice. Then, the characteristics of the developed antibodies were studied by ELISA. Furthermore, the immunoreactivity of the purified recombinant protein was confirmed by immunoblotting. Alum as a common adjuvant boosted immunogenicity of the construct, resulting significantly greater anti-pili IgG titre. Mice antibody response consisted of IgG1, IgG2a, IgG2b and IgG3 subtypes with predominance of IgG1 subclass. The developed antibodies were capable to inhibit motility of PAO1 strain. In conclusion, our primary results revealed that the designed recombinant protein is a protective construct and may be used as a potential candidate for prophylactic purposes against P. aeruginosa infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study we examined the potential of integrated PilQ/PilA (QA) antigen as a vaccine candidate against Pseudomonas aeruginosa. Nowadays, anti-adhesion based vaccines are considered as new means to prevent or treat bacterial infections. Our study revealed that chimeric protein PilQ and disulphide turn region of PilA triggers production of specific antibodies. This humoral immune responses augmented when QA was administered in combination with an adjuvant. The results demonstrated efficacy of the designed recombinant chimeric antigen as an effective candidate in prevention of P. aeruginosa infection.

Bioengineering a bacterial pathogen to assemble its own particulate vaccine capable of inducing cellular immunity

Many bacterial pathogens naturally form cellular inclusions. Here the immunogenicity of polyhydroxyalkanoate (PHA) inclusions and their use as particulate vaccines delivering a range of host derived antigens was assessed. Our study showed that PHA inclusions of pathogenic Pseudomonas aeruginosa are immunogenic mediating a specific cell-mediated immune response. Protein engineering of the PHA inclusion forming enzyme by translational fusion of epitopes from vaccine candidates outer membrane proteins OprI, OprF, and AlgE mediated self-assembly of PHA inclusions coated by these selected antigens. Mice vaccinated with isolated PHA inclusions produced a Th1 type immune response characterized by antigen-specific production of IFN-γ and IgG2c isotype antibodies. This cell-mediated immune response was found to be associated with the production of functional antibodies reacting with cells of various P. aeruginosa strains as well as facilitating opsonophagocytic killing. This study showed that cellular inclusions of pathogenic bacteria are immunogenic and can be engineered to display selected antigens suitable to serve as particulate subunit vaccines against infectious diseases.

X-ray Irradiated Vaccine Confers protection against Pneumonia caused by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a gram-negative bacterium and one of the leading causes of nosocomial infection worldwide, however, no effective vaccine is currently available in the market. Here, we demonstrate that inactivation of the bacteria by X-ray irradiation inhibits its replication capability but retained antigenic expression functionally thus allowing its use as a potential vaccine. Mice immunized by this vaccine were challenged by the parental strain, the O-antigen-homologous strain PAO-1 (O2/O5) and heterologous strain PAO-6 (O6) in an acute pneumonia model. We further measured the protective effect of the vaccine, as well as host innate and cellular immunity responses. We found immunized mice could protect against both strains. Notably, the antiserum only had significant protective role against similar bacteria, while adoptive transfer of lymphocytes significantly controlled the spread of the virulent heterologous serogroup PAO-6 infection, and the protective role could be reversed by CD4 rather than CD8 antibody. We further revealed that vaccinated mice could rapidly recruit neutrophils to the airways early after intranasal challenge by PAO-6, and the irradiated vaccine was proved to be protective by the generated CD4(+) IL-17(+) Th17 cells. In conclusion, the generation of inactivated but metabolically active microbes is a promising strategy for safely vaccinating against Pseudomonas aeruginosa.

From worms to targeting virulence factors

Rising antibiotic resistance means that alternative antibacterial strategies are sorely needed. In this issue, Zhu et al. (2015) report the use of a Caenorhabditis elegans model to validate the Pseudomonas aeruginosa virulence factor LasB as a potential therapeutic target and to identify a LasB inhibitor with in vivo efficacy.

RGD capsid modification enhances mucosal protective immunity of a non-human primate adenovirus vector expressing Pseudomonas aeruginosa OprF

Replication-deficient adenoviral (Ad) vectors of non-human serotypes can serve as Ad vaccine platforms to circumvent pre-existing anti-human Ad immunity. We found previously that, in addition to that feature, a non-human primate-based AdC7 vector expressing outer membrane protein F of P. aeruginosa (AdC7OprF) was more potent in inducing lung mucosal and protective immunity compared to a human Ad5-based vector. In this study we analysed if genetic modification of the AdC7 fibre to display an integrin-binding arginine-glycine-aspartic acid (RGD) sequence can further enhance lung mucosal immunogenicity of AdC7OprF. Intratracheal immunization of mice with either AdC7OprF.RGD or AdC7OprF induced robust serum levels of anti-OprF immunoglobulin (Ig)G up to 12 weeks that were higher compared to immunization with the human vectors Ad5OprF or Ad5OprF.RGD. OprF-specific cellular responses in lung T cells isolated from mice immunized with AdC7OprF.RGD and AdC7OprF were similar for T helper type 1 (Th1) [interferon (IFN)-γ in CD8(+) and interleukin (IL)-12 in CD4(+)], Th2 (IL-4, IL-5 and IL-13 in CD4(+)) and Th17 (IL-17 in CD4(+)). Interestingly, AdC7OprF.RGD induced more robust protective immunity against pulmonary infection with P. aeruginosa compared to AdC7OprF or the control Ad5 vectors. The enhanced protective immunity induced by AdC7OprF.RGD was maintained in the absence of alveolar macrophages (AM) or CD1d natural killer T cells. Together, the data suggest that addition of RGD to the fibre of an AdC7-based vaccine is useful to enhance its mucosal protective immunogenicity.

OBTENÇÃO E CARACTERIZAÇÃO DE IMUNÓGENO CONJUGADO DE LIPOPOLISSACARÍDEO DE PSEUDOMONAS AERUGINOSA E ALBUMINA BOVINA

RESUMO A Pseudomonas aeruginosa é agente etiológico de infecções oportunistas, principalmente em pacientes imunocomprometidos. Suas características inerentes em desenvolver resistência aos mais variados tipos de antibacterianos a torna um ponto crítico no controle de infecções. Em animais, os problemas com multirresistência ocorrem principalmente em casos de otite, cistite, úveo-conjuntivite, endometrite e mastite, não havendo vacina comercialmente disponível. No intuito de melhorar a imunogenicidade desse antígeno, foi testada a técnica de conjugação do lipopolissacarídeo (LPS) de P. aeruginosa à albumina bovina (BSA) por aminação redutiva direta utilizando .-periodato de sódio. A conjugação foi avaliada por cromatografia de gel-permeação, dosando-se açúcar e proteína totais, e tanto o LPS quanto a BSA foram identificados em proporções semelhantes. A imunização de camundongos com a vacina conjugada LPS-BSA conferiu títulos de anticorpos aglutinantes contra P. aeruginosa inferiores aos obtidos com a mistura de LPS e BSA livres. Foram 65% e 86% menores na 6ª e na 10ª semanas após o procedimento de hiperimunização, respectivamente. Isto indica que a reação de conjugação resultou em um produto imunogênico, porém, sua qualidade precisará ser melhorada.

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.

Polymorphisms in the Pseudomonas aeruginosa type III secretion protein, PcrV - implications for anti-PcrV immunotherapy

The type III secretion system of Pseudomonas aeruginosa, responsible for acute infection, is composed of over twenty proteins that facilitate cytotoxin injection directly into host cells. Integral to this process is production and secretion of PcrV. Administration of a recently developed, anti-PcrV immunoglobulin, either as a therapeutic or prophylactic has previously demonstrated efficacy against laboratory strains of P. aeruginosa in a murine model. To determine if this therapy is universally applicable to a variety of P. aeruginosa clinical isolates, genetic heterogeneity of pcrV was analyzed among strains collected from three geographically distinct regions; United States, France and Japan. Sequence analysis of PcrV demonstrated limited variation among the clinical isolates examined. Strains were grouped according to the presence of non-synonymous single nucleotide polymorphisms. Representative isolates from each mutant group were examined for the ability of anti-PcrV to bind the protein secreted by these strains. The protective effect of anti-PcrV IgG against each strain was determined using an epithelial cell line cytotoxicity assay. The majority of strains tested demonstrated reduced cytotoxicity in the presence of anti-PcrV IgG. This study provides insights into the natural sequence variability of PcrV and an initial indication of the amino acid residues that appear to be conserved across strains. It also demonstrates the protective effect of anti-PcrV immunotherapy against a multitude of P. aeruginosa strains from diverse global regions with a variety of mutations in PcrV.

Genome-wide study of Pseudomonas aeruginosa outer membrane protein immunogenicity using self-assembling protein microarrays

Pseudomonas aeruginosa is responsible for potentially life-threatening infections in individuals with compromised defense mechanisms and those with cystic fibrosis. P. aeruginosa infection is notable for the appearance of a humoral response to some known antigens, such as flagellin C, elastase, alkaline protease, and others. Although a number of immunogenic proteins are known, no effective vaccine has been approved yet. Here, we report a comprehensive study of all 262 outer membrane and exported P. aeruginosa PAO1 proteins by a modified protein microarray methodology called the nucleic acid-programmable protein array. From this study, it was possible to identify 12 proteins that trigger an adaptive immune response in cystic fibrosis and acutely infected patients, providing valuable information about which bacterial proteins are actually recognized by the immune system in vivo during the natural course of infection. The differential detections of these proteins in patients and controls proved to be statistically significant (P<0.01). The study provides a list of potential candidates for the improvement of serological diagnostics and the development of vaccines.

Pseudomonas aeruginosa virulence and therapy: evolving translational strategies

OBJECTIVE

Although most reviews of Pseudomonas aeruginosa therapeutics focus on antibiotics currently in use or in the pipeline, we review evolving translational strategies aimed at using virulence factor antagonists as adjunctive therapies.

DATA SOURCE

Current literature regarding P. aeruginosa virulence determinants and approaches that target them, with an emphasis on type III secretion, quorum-sensing, biofilms, and flagella.

DATA EXTRACTION AND SYNTHESIS

P. aeruginosa remains one of the most important pathogens in nosocomial infections, with high associated morbidity and mortality. Its predilection to develop resistance to antibiotics and expression of multiple virulence factors contributes to the frequent ineffectiveness of current therapies. Among the many P. aeruginosa virulence determinants that impact infections, type III secretion, quorum sensing, biofilm formation, and flagella have been the focus on much recent investigation. Here we review how increased understanding of these important bacterial structures and processes has enabled the development of novel approaches to inhibit each. These promising translational strategies may lead to the development of adjunctive therapies capable of improving outcomes.

CONCLUSIONS

Adjuvant therapies directed against virulence factors have the potential to improve outcomes in P. aeruginosa infections.

Antibiofilm activity of a diverse oroidin library generated through reductive acylation

A diverse 20-compound library of analogues based on the marine alkaloid oroidin were synthesized via a reductive acylation strategy. The final target was then assayed for inhibition and dispersion activity against common proteobacteria known to form biofilms. This methodology represents a significant improvement over the generality of known methods to acylate substrates containing 2-aminoimidazoles and has the potential to have broad application to the synthesis of more advanced oroidin family members and their corresponding analogues.

Synthesis and antibiofilm activity of a second-generation reverse-amide oroidin library: a structure-activity relationship study

A second-generation library of 2-aminoimidazole-based derivatives incorporating a "reversed amide" (RA) motif in comparison to the marine natural product oroidin were synthesized and subsequently assayed for antibiofilm activity against the medically relevant Gram-negative proteobacteria P. aeruginosa and A. baumannii. Most notably, an in-depth activity profile is reported for the most active subclass of derivatives that bear linear aliphatic chains off the amide bond. Additionally, further structural modifications of the core template, such as removal of the amide bond or substitution with a triazole isostere, resulted in the discovery of analogues with antibiofilm activities that varied with respect to their inhibition and dispersal properties of P. aeruginosa and A. baumannii biofilms.

Design of a liposomal candidate vaccine against Pseudomonas aeruginosa and its evaluation in triggering systemic and lung mucosal immunity

PURPOSE

To design and evaluate liposomal constructs capable of inducing a potent systemic and airway humoral response to Pseudomonas aeruginosa

METHODS

Liposomes contained a peptide derived from P. aeruginosa pilin protein as B epitope, a peptide derived from Influenza hemagglutinin protein as Th epitope, the TLR agonist Pam3CAG or Pam2CAG as adjuvant, and a mannosylated lipid as dendritic cell targeting agent. These constructions were administered to mice intraperitoneally (i.p.) or intranasally (i.n.). Their immunogenicity was evaluated by measuring B epitope-specific immunoglobulins in the serum and the airways by ELISA.

RESULTS

The B epitope, in its native form or after substitution of a cysteine by a serine, induced high systemic IgG titers when formulated in the presence of Pam3CAG or Pam2CAG and administered i.p.. No IgA response was observed in the airways upon injection of candidate vaccines by i.p. route, whatever the B epitope or the adjuvant. However, i.n. vaccination resulted in a significant local production of IgA. Finally, the production of IgG was more rapid when mannose was incorporated.

CONCLUSIONS

All liposomal candidate vaccines tested induced the production of IgG and/or IgA directed against an immunogenic peptide from P. aeruginosa. Liposomal constructs could be attractive in the vaccination against P. aeruginosa.

Pseudomonas aeruginosa infections are prevented in cystic fibrosis patients by avian antibodies binding Pseudomonas aeruginosa flagellin

Pseudomonas aeruginosa (PA) is the main cause of morbidity and mortality in cystic fibrosis (CF) patients. CF patients with chronic PA infections have a more rapid deterioration of their lung function and the bacteria become impossible to eradicate from the lungs. Antibiotic resistance among PA strains in CF patients is steadily increasing. Specific chicken (IgY) antibodies against PA have been shown to have potential to prevent PA infections in CF. Anti-Pseudomonas IgY reduces PA adhesion to epithelia, but the mechanism has not been fully elucidated. To gain further insight into the prophylactic effect of these antibodies, the immunoreactivity was investigated by 2D electrophoresis of PA strains, immunoblotting and MALDI-TOF-MS. To confirm the identity of the proteins, the tryptic peptides were analyzed by MALDI-TOF-MS to accurately measure their monoisotopic masses as well as determine their amino acid sequences. In order to facilitate fragmentation of the peptides they were N-terminally or C-terminally labeled. Several strains were investigated and anti-Pseudomonas IgY was immunoreactive against all of these strains, which strengthens its potential as a prophylactic treatment against PA. Flagellin was identified as the major antigen. Flagellin is the main protein of the flagella and is crucial for establishing infections in hosts as well as being involved in PA chemotaxis, motility, adhesion and inflammation. Furthermore, secreted flagellin elicits an inflammatory response. In conclusion, anti-Pseudomonas IgY binds flagellin, which may prevent PA infections in CF patients by hindering host invasion.

Pseudomonas aeruginosa: resistance and therapeutic options at the turn of the new millennium

Pseudomonas aeruginosa is a major cause of nosocomial infections. This organism shows a remarkable capacity to resist antibiotics, either intrinsically (because of constitutive expression of beta-lactamases and efflux pumps, combined with low permeability of the outer-membrane) or following acquisition of resistance genes (e.g., genes for beta-lactamases, or enzymes inactivating aminoglycosides or modifying their target), over-expression of efflux pumps, decreased expression of porins, or mutations in quinolone targets. Worryingly, these mechanisms are often present simultaneously, thereby conferring multiresistant phenotypes. Susceptibility testing is therefore crucial in clinical practice. Empirical treatment usually involves combination therapy, selected on the basis of known local epidemiology (usually a beta-lactam plus an aminoglycoside or a fluoroquinolone). However, therapy should be simplified as soon as possible, based on susceptibility data and the patient's clinical evolution. Alternative drugs (e.g., colistin) have proven useful against multiresistant strains, but innovative therapeutic options for the future remain scarce, while attempts to develop vaccines have been unsuccessful to date. Among broad-spectrum antibiotics in development, ceftobiprole, sitafloxacin and doripenem show interesting in-vitro activity, although the first two molecules have been evaluated in clinics only against Gram-positive organisms. Doripenem has received a fast track designation from the US Food and Drug Administration for the treatment of nosocomial pneumonia. Pump inhibitors are undergoing phase I trials in cystic fibrosis patients. Therefore, selecting appropriate antibiotics and optimising their use on the basis of pharmacodynamic concepts currently remains the best way of coping with pseudomonal infections.

Multivalent DNA vaccine protects mice against pulmonary infection caused by Pseudomonas aeruginosa

For efficacious vaccine development against Pseudomonas aeruginosa (P. aeruginosa), the immunogenicity of multivalent DNA vaccine was evaluated. Three different plasmids each targeting a fusion of outer membrane proteins (OprF/OprI), a protein regulating type III secretion system (PcrV), or an appendage (PilA) were prepared and mice were immunized with single (monovalent) or a combination of these plasmids (multivalent) via intramuscular electroporation (imEPT) or gene gun. Immunization with multivalent DNA vaccine via imEPT induced the most potent protection against lethal pneumonia. Although the serum levels of IgG binding to whole bacteria cells were comparable between groups, the strongest immune protection was associated with the serum levels of Th1-dominated multivalent IgG, the bronchoalveolar levels of macrophage inflammatory protein 2 (MIP-2) and IFN-gamma, and the number of neutrophils and macrophages in the bronchoalveolar lavage following intranasal challenge. These results implied the possible clinical application of multivalent DNA vaccine against P. aeruginosa.

Role of granulocyte macrophage colony-stimulating factor during gram-negative lung infection with Pseudomonas aeruginosa

Granulocyte macrophage colony-stimulating factor (GM-CSF) stimulates survival, proliferation, differentiation, and function of myeloid cells. Recently, GM-CSF has been shown to be important for normal pulmonary homeostasis. We report that GM-CSF is induced in lung leukocytes during infection with Gram-negative bacteria. Therefore, we postulated that deficiencies in GM-CSF would increase susceptibility to Gram-negative infection in vivo. After an intratracheal inoculum with Pseudomonas aeruginosa, GM-CSF-/- mice show decreased survival compared with wild-type mice. GM-CSF-/- mice show increased lung, spleen, and blood bacterial CFU. GM-CSF-/- mice are defective in the production of cysteinyl leukotrienes, prostaglandin E2, macrophage inflammatory protein, and keratinocyte-derived chemokine in lung leukocytes postinfection. Despite these defects, inflammatory cell recruitment is not diminished at 6 or 24 h postinfection, and the functional activity of polymorphonuclear leukocytes from the lung and peritoneum against P. aeruginosa is enhanced in GM-CSF-/- mice. In contrast, alveolar macrophage (AM) phagocytosis, killing, and H2O2 production are defective in GM-CSF-/- mice. Although the absence of GM-CSF has profound effects on AMs, peritoneal macrophages seem to have normal bactericidal activities in GM-CSF-/- mice. Defects in AM function may be related to diminished levels of IFN-gamma and TNF-alpha postinfection. Thus, GM-CSF-/- mice are more susceptible to lung infection with P. aeruginosa as a result of impaired AM function.

Targeting mechanisms of Pseudomonas aeruginosa pathogenesis

Pseudomonas aeruginosa is an opportunistic pathogen responsible for ventilator-acquired pneumonia, acute lower respiratory tract infections in immunocompromised patients and chronic respiratory infections in cystic fibrosis patients. High incidence, infection severity and increasing resistance characterize P. aeruginosa infections, highlighting the need for new therapeutic options. One such option is to target the many pathogenic mechanisms conferred to P. aeruginosa by its large genome encoding many different virulence factors. This article reviews the pathogenic mechanisms and potential therapies targeting these mechanisms in P. aeruginosa respiratory infections.

Update on Pseudomonas aeruginosa and Acinetobacter baumannii infections in the healthcare setting

PURPOSE OF REVIEW

Infections with Pseudomonas aeruginosa and Acinetobacter baumannii are of great concern for hospitalized patients, especially with multidrug-resistant strains. This review focuses on recent data that may help us to understand the emergence, spread, and persistence of antibiotic resistance, and summarizes the optional treatment feasible for these resistant bacteria.

RECENT FINDINGS

Multidrug-resistant P. aeruginosa and A. baumannii are increasingly causing nosocomial infections; multidrug-resistant clones are spreading into new geographic areas, and susceptible strains are acquiring resistance genes. New extended-spectrum beta-lactamases and carbapenemases are emerging, leading to pan-resistant strains. Current studies focus on the effect of antibiotics on gene expression in P. aeruginosa biofilms and their contribution to resistance to therapy. Treatment options for multidrug-resistant P. aeruginosa and A. baumannii infections are limited in most cases to carbapenems. Sulbactam is a treatment option for pan-resistant A. baumannii, and or renewed use of an old drug, colistin, is being entertained for pan-resistant A. baumannii and P. aeruginosa. Immunotherapy is a promising new modality being explored. Prevention of emergence of resistance through combination therapy and pharmacokinetic strategies are studied.

SUMMARY

The emergence and spread of multidrug-resistant P. aeruginosa and A. baumannii and their genetic potential to carry and transfer diverse antibiotic resistance determinants pose a major threat in hospitals. The complex interplay of clonal spread, persistence, transfer of resistance elements, and cell-cell interaction contribute to the difficulty in treating infections caused by these multidrug-resistant strains. In the absence of new antibiotic agents, new modalities of treatment should be developed.