Immunization with Pseudomonas aeruginosa vaccines and adjuvant can modulate the type of inflammatory response subsequent to infection

The comparative effects of erythromycin and amikacin on acute respiratory Pseudomonas aeruginosa infection

BACKGROUND

One of the most common causes of pneumonia is Pseudomonas aeruginosa (P. aeruginosa). As with other microbial pathogens, this bacterium tends to develop resistance to various antibiotics. Amikacin and erythromycin, which are from the aminoglycoside and macrolide antibiotic families, are used to treat respiratory infections caused by P. aeruginosa.

OBJECTIVES

This study explored whether amikacin, erythromycin or a combination of both works better against P. aeruginosa acute lung infection.

METHODS

For this study, 32 rats were used. The trachea of rats was exposed aseptically and their lung was infected with P. aeruginosa through trachea. Then, according to the group, they received amikacin, erythromycin or a combination of both for 1 week. Finally, they were euthanised on the 3rd and 7th days post-infection. The macroscopic and microscopic evaluations of the lungs, kidney and liver were performed. The right lung was collected for in vivo bacteriological analysis.

RESULTS

The amikacin group (A group) had a statistically significantly lower macroscopic and microscopic scores than the other groups (p < 0.05). In vivo bacteriological test revealed that the A group had significantly lower lung bacterial load (p < 0.05).

CONCLUSIONS

In summary, it was concluded that amikacin could help alleviate the respiratory infection caused by P. aeruginosa solely, and it was more effective than erythromycin.

Inhibition of Quorum Sensing-Controlled Virulence Factors and Biofilm Formation in Pseudomonas aeruginosa by Culture Extract from Novel Bacterial Species of Paenibacillus Using a Rat Model of Chronic Lung Infection

Quorum sensing (QS) is a key regulator of virulence factors and biofilm formation in Gram-negative bacteria such as Pseudomonas aeruginosa. Microorganisms that inhabit soil are of strategic importance in the discovery of compounds with anti-QS properties. The objective of the study was to test the culture extract of a taxonomically novel species of Paenibacillus strain 139SI for its inhibitory effects on the QS-controlled virulence factors and biofilm formation of Pseudomonas aeruginosa both in vitro and in vivo. The Paenibacillus sp. culture extract was used to test its anti-QS effects on the LasA protease, LasB elastase, pyoverdin production, and biofilm formation of P. aeruginosa as well as evaluate its therapeutic effects on lung bacteriology, pathology, hematological profile, and serum antibody responses of experimental animals in a rat model of chronic lung infection. Results showed significant decrease in the activities of QS-controlled LasA protease, LasB elastase pyoverdin, and biofilm formation of P. aeruginosa caused by the culture extract. Moreover, the extract significantly prolonged the survival times of rats and facilitated the clearance of biofilm infections from infected lungs. In conclusion, the antiquorum sensing effects of culture extract from a novel species of Paenibacillus provide new insights to combat biofilm-associated infections.

Protective effect of DNA vaccine encoding pseudomonas exotoxin A and PcrV against acute pulmonary P. aeruginosa Infection

Infections with Pseudomonas aeruginosa have been a long-standing challenge for clinical therapy because of complex pathogenesis and resistance to antibiotics, thus attaching importance to explore effective vaccines for prevention and treatment. In the present study, we constructed a novel DNA vaccine by inserting mutated gene toxAm encoding Pseudomonas Exotoxin A and gene pcrV encoding tip protein of the type III secretion system into respective sites of a eukaryotic plasmid pIRES, named pIRES-toxAm-pcrV, and next evaluated the efficacy of the vaccine in murine acute Pseudomonas pneumonia models. Compared to DNA vaccines encoding single antigen, mice vaccinated with pIRES-toxAm-pcrV elicited higher levels of antigen-specific serum immunoglobulin G (IgG), enhanced splenic cell proliferation and cytokine secretion in response to Pseudomonas aeruginosa antigens, additionally PAO1 challenge in mice airway resulted in reduced bacteria burden and milder pathologic changes in lungs. Besides, it was observed that immunogenicity and protection could be promoted by the CpG ODN 1826 adjuvant. Taken together, it's revealed that recombinant DNA vaccine pIRES-toxAm-pcrV was a potential candidate for immunotherapy of Pseudomonas aeruginosa infection and the CpG ODN 1826 a potent stimulatory adjuvant for DNA vaccination.

Prosthesis infections after orthopedic joint replacement: the possible role of bacterial biofilms

Prosthesis-related infection is a serious complication for patients after orthopedic joint replacement, which is currently difficult to treat with antibiotic therapy. Consequently, in most cases, removal of the infected prosthesis is the only solution to cure the infection. It is, therefore, important to understand the comprehensive interaction between the microbiological situation and the host immune responses that lead to prosthesis infections. Evidence indicates that prosthesis infections are actually biofilm-correlated infections that are highly resistant to antibiotic treatment and the host immune responses. The authors reviewed the related literature in the context of their clinical experience, and discussed the possible etiology and mechanism leading to the infections, especially problems related to bacterial biofilm, and prophylaxis and treatment of infection, including both microbiological and surgical measures. Recent progress in research into bacterial biofilm and possible future treatment options of prosthesis-related infections are discussed.

Cloning, expression and characterization of recombinant exotoxin A-flagellin fusion protein as a new vaccine candidate against Pseudomonas aeruginosa infections

BACKGROUND

Infections due to Pseudomonas aeruginosa are among the leading causes of morbidity and mortality in patients who suffer from impaired immune responses and chronic diseases such as cystic fibrosis. At present, aggressive antibiotic therapy is the only choice for management of P. aeruginosa infections, but emergence of highly resistant strains necessitated the development of novel alternative therapeutics including an effective vaccine. Several P. aeruginosa antigens have been tested for vaccine development, including lipopolysaccharide alone, polysaccharides alginate, extracellular proteins, exotoxin A (exo A) and killed whole cell. However, none of them are currently available clinically.

METHODS

In this research, recombinant exoA-flagellin (fliC) fusion protein as a cocktail antigen was expressed and purified and its antigenic characteristics were evaluated.

RESULTS

Expression of recombinant fusion protein by E. coli using pET22b vector resulted in production of exoA-fliC fusion protein in high concentration. Based on Western-blotting results, recombinant fusion protein showed a good antigenic interaction with sera from patients with various P. aeruginosa infections.

CONCLUSION

These results suggested that recombinant exoA-fliC fusion protein can be produced in the laboratory, and tested as a candidate vaccine in P. aeruginosa infections.

Panax ginseng has anti-infective activity against opportunistic pathogen Pseudomonas aeruginosa by inhibiting quorum sensing, a bacterial communication process critical for establishing infection

Virulent factors produced by pathogens play an important role in the infectious process, which is regulated by a cell-to-cell communication mechanism called quorum sensing (QS). Pseudomonas aeruginosa is an important opportunistic human pathogen, which causes infections in patients with compromised immune systems and cystic fibrosis. The QS systems of P. aeruginosa use N-acylated homoserine lactone (AHL) as signal molecules. Previously we have demonstrated that Panax ginseng treatment allowed the animals with P. aeruginosa pneumonia to effectively clear the bacterial infection. We postulated that the ability to impact the outcome of infections is partly due to ginseng having direct effect on the production of P. aeruginosa virulence factors. The study explores the effect of ginseng on alginate, protease and AHL production. The effect of ginseng extracts on growth and expression of QS-controlled virulence factors on the prototypic P. aeruginosa PAO1 and its isogenic mucoid variant (PAOmucA22) was determined. Ginseng did not inhibit the growth of the bacteria, enhanced the extracellular protein production and stimulated the production of alginate. However, ginseng suppressed the production of LasA and LasB and down-regulated the synthesis of the AHL molecules. Ginseng has a negative effect on the QS system of P. aeruginosa, may explain the ginseng-dependent bacterial clearance from the animal lungs in vivo in our previous animal study. It is possible that enhancing and repressing activities of ginseng are mutually exclusive as it is a complex mixture, as shown with the HPLC analysis of the hot water extract. Though ginseng is a promising natural synergetic remedy, it is important to isolate and evaluate the ginseng compounds associated with the anti-QS activity.

Administration of nonviral gene vector encoding rat beta-defensin-2 ameliorates chronic Pseudomonas aeruginosa lung infection in rats

BACKGROUND

Beta-defensin-2 (BD-2) plays an important role in host defense against pathogenic microbe challenge by its direct antimicrobial activity and immunomodulatory functions. The present study aimed to determine whether genetic up-regulation of rat BD-2 (rBD-2) could ameliorate chronic Pseudomonas aeruginosa lung infection in rats.

METHODS

Plasmid-encoding rBD-2 was delivered to lungs in vivo using linear polyethylenimine at 48 h before challenging with seaweed alginate beads containing P. aeruginosa. Macroscopic and histopathological changes of the lungs, bacterial loads, inflammatory infiltration, and the levels of cytokines/chemokines [interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, kertinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2)] were measured at 3 and 7 days post-infection (p.i.).

RESULTS

The overexpression of rBD-2 resulted in a significant increase in animal survival rate (at 3 days p.i.), a significant decrease in bacterial loads in the lungs (at 3 and 7 days p.i.), and significantly milder lung pathology. In addition, the overexpression of rBD-2 led to increased infiltration of polymorphonuclear neutrophils (PMN), and elevated protein expression of cytokines/chemokines (IL-1beta, TNF-alpha, KC and MIP-2) at the early stage of infection (at 3 days p.i.), at the same time as being dramatically decreased at the later stage of infection (at 7 days p.i.).

CONCLUSIONS

Genetic up-regulation of rBD-2 increased animal survival rate, and reduced bacterial loads in lungs after bacterial infection. The overexpression of rBD-2 also modulated the production of several cytokines/chemokines and increased PMN recruitment at the early stage of infection. Our findings indicate that the enhancement of BD-2 may be an efficacious intervention for chronic P. aeruginosa lung infection.

Assessing the emergence of resistance: the absence of biological cost in vivo may compromise fosfomycin treatments for P. aeruginosa infections

BACKGROUND

Fosfomycin is a cell wall inhibitor used efficiently to treat uncomplicated urinary tract and gastrointestinal infections. A very convenient feature of fosfomycin, among others, is that although the expected frequency of resistant mutants is high, the biological cost associated with mutation impedes an effective growth rate, and bacteria cannot offset the obstacles posed by host defenses or compete with sensitive bacteria. Due to the current scarcity of new antibiotics, fosfomycin has been proposed as an alternative treatment for other infections caused by a wide variety of bacteria, particularly Pseudomonas aeruginosa. However, whether fosfomycin resistance in P. aeruginosa provides a fitness cost still remains unknown.

PRINCIPAL FINDINGS

We herein present experimental evidence to show that fosfomycin resistance cannot only emerge easily during treatment, but that it is also cost-free for P. aeruginosa. We also tested if, as has been reported for other species such as Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis, fosfomycin resistant strains are somewhat compromised in their virulence. As concerns colonization, persistence, lung damage, and lethality, we found no differences between the fosfomycin resistant mutant and its sensitive parental strain. The probability of acquisition in vitro of resistance to the combination of fosfomycin with other antibiotics (tobramycin and imipenem) has also been studied. While the combination of fosfomycin with tobramycin makes improbable the emergence of resistance to both antibiotics when administered together, the combination of fosfomycin plus imipenem does not avoid the appearance of mutants resistant to both antibiotics.

CONCLUSIONS

We have reached the conclusion that the use of fosfomycin for P. aeruginosa infections, even in combined therapy, might not be as promising as expected. This study should encourage the scientific community to assess the in vivo cost of resistance for specific antibiotic-bacterial species combinations, and therefore avoid reaching universal conclusions from single model organisms.

Inactivation of the hmgA gene of Pseudomonas aeruginosa leads to pyomelanin hyperproduction, stress resistance and increased persistence in chronic lung infection

Clinical isolates of Pseudomonas aeruginosa that hyperproduce a dark-brown pigment are quite often found in the lungs of chronically infected patients, suggesting that they may have an adaptive advantage in chronic infections. We have screened a library of random transposon insertions in P. aeruginosa. Transposon insertions resulting in the hyperproduction of a dark-brown pigment were found to be located in the hmgA gene, which putatively encodes the enzyme homogentisate-1,2-dioxygenase. Complementation studies indicate that hmgA disruption is responsible for the hyperproduction of pyomelanin in both laboratory and clinical isolates. A relationship between hmgA disruption and adaptation to chronic infection was explored and our results show that the inactivation of hmgA produces a slight reduction of killing ability in an acute murine model of lung infection. On the other hand, it also confers decreased clearance and increased persistence in chronic lung infections. Whether pyomelanin production is the cause of the increased adaptation to chronicity or just a side effect of hmgA inactivation is a question to be studied in future; however, this adaptation is consistent with the higher resistance to oxidative stress conferred in vitro by the pyomelanin pigment. Our results clearly demonstrate that hmgA inactivation leads to a better adaptation to chronic infection, and strongly suggest that this mechanism may be exploited in naturally occurring P. aeruginosa strains.

In vitro and in vivo antimicrobial activities of seeds of Caesalpinia bonduc (Lin.) Roxb

AIM OF THE STUDY

Caesalpinia bonduc (Lin.) Roxb. is a known drug in Ayurveda to treat various diseases specifically tumors, cysts and cystic fibrosis (CF). The aim of this study was to assess in vitro as well as in vivo antimicrobial activity of Caesalpinia bonduc seeds.

MATERIALS AND METHODS

The in vitro antimicrobial activities of seed coat and seed kernel extracts were investigated by microbroth dilution assay. In vivo activities of hydro-alcoholic extracts were investigated in rat models of chronic Pseudomonas aeruginosa pneumonia mimicking that in patients with cystic fibrosis.

RESULTS

Various extracts of plant seeds exhibited in vitro antimicrobial activities in a range of 22-350 microg/ml. The extracts also showed activity against methicillin resistant (MR) Staphylococcus aureus and ampicillin resistant (AR) Pseudomonas aeruginosa as in the sensitive strains. In rat model of chronic Pseudomonas aeruginosa pneumonia, hydro-alcoholic extracts of Caesalpinia bonduc seed kernel (CBSK) and Caesalpinia bonduc seed coat (CBSC) were injected subcutaneously in the test groups of animals. The control groups were treated with cortisone and saline. Two weeks after challenge with Pseudomonas aeruginosa, the CBSK treated animals showed a significant bacterial clearance from the lungs (P<0.04) and less severe incidence of lung abscess (P<0.05).

CONCLUSION

Results showed that Caesalpinia bonduc may have the potential to be promising natural medicine, with other forms of treatments, for CF patients with chronic Pseudomonas aeruginosa lung infections.

Antiviral activity of Nrf2 in a murine model of respiratory syncytial virus disease

RATIONALE

Respiratory syncytial virus (RSV) is the most frequent cause of significant lower respiratory illness in infants and young children, but its pathogenesis is not fully understood. The transcription factor Nrf2 protects lungs from oxidative injury and inflammation via antioxidant response element (ARE)-mediated gene induction.

OBJECTIVES

The current study was designed to determine the role of Nrf2-mediated cytoprotective mechanisms in murine airway RSV disease.

METHODS

Nrf2-deficient (Nrf2(-/-)) and wild-type (Nrf2(+/+)) mice were intranasally instilled with RSV or vehicle. In a separate study, Nrf2(+/+) and Nrf2(-/-) mice were treated orally with sulforaphane (an Nrf2-ARE inducer) or phosphate-buffered saline before RSV infection.

MEASUREMENTS AND MAIN RESULTS

RSV-induced bronchopulmonary inflammation, epithelial injury, and mucus cell metaplasia as well as nasal epithelial injury were significantly greater in Nrf2(-/-) mice than in Nrf2(+/+) mice. Compared with Nrf2(+/+) mice, significantly attenuated viral clearance and IFN-gamma, body weight loss, heightened protein/lipid oxidation, and AP-1/NF-kappaB activity along with suppressed antioxidant induction was found in Nrf2(-/-) mice in response to RSV. Sulforaphane pretreatment significantly limited lung RSV replication and virus-induced inflammation in Nrf2(+/+) but not in Nrf2(-/-) mice.

CONCLUSIONS

The results of this study support an association of oxidant stress with RSV pathogenesis and a key role for the Nrf2-ARE pathway in host defense against RSV.

Pseudomonas aeruginosa RsmA plays an important role during murine infection by influencing colonization, virulence, persistence, and pulmonary inflammation

The ability of Pseudomonas aeruginosa to cause a broad range of infections in humans is due, at least in part, to its adaptability and its capacity to regulate the expression of key virulence genes in response to specific environmental conditions. Multiple two-component response regulators have been shown to facilitate rapid responses to these environmental conditions, including the coordinated expression of specific virulence determinants. RsmA is a posttranscriptional regulatory protein which controls the expression of a number of virulence-related genes with relevance for acute and chronic infections. Many membrane-bound sensors, including RetS, LadS, and GacS, are responsible for the reciprocal regulation of genes associated with acute infection and chronic persistence. In P. aeruginosa this is due to sensors influencing the expression of the regulatory RNA RsmZ, with subsequent effects on the level of free RsmA. While interactions between an rsmA mutant and human airway epithelial cells have been examined in vitro, the role of RsmA during infection in vivo has not been determined yet. Here the function of RsmA in both acute and chronic models of infection was examined. The results demonstrate that RsmA is involved in initial colonization and dissemination in a mouse model of acute pneumonia. Furthermore, while loss of RsmA results in reduced colonization during the initial stages of acute infection, the data show that mutation of rsmA ultimately favors chronic persistence and results in increased inflammation in the lungs of infected mice.

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.

The effects of recurrent Pseudomonas aeruginosa infection on pulmonary parenchyma and vasculature in rats fed on a cholesterol-rich diet

It has been demonstrated that both hypercholesterolemia and infectious agents are contributing factors in atherosclerosis but their combined effect on the pulmonary vascular bed is not known. To answer this question, the authors tried to demonstrate the effects of recurrent infection on pulmonary parenchyma and vascular system in cholesterol-fed rats. Sixty-six rats were randomly divided into 4 groups: Groups I (control), II (cholesterol-rich diet), III (recurrent pulmonary Pseudomonas aeruginosa infection), IV (cholesterol-rich diet + recurrent infection). After 6 months serum cholesterol levels didn't increase in any of the groups. Central pulmonary artery wall thickness was increased in group IV (P < .0001). Although not significant, peripheral pulmonary artery wall thickness was increased in group IV. In rats fed on a cholesterol-rich diet, recurrent infection caused a significant increase in atherosclerosis, although serum cholesterol levels didn't increase. Infection and cholesterol-rich diet have a synergistic effect on atherosclerosis in the pulmonary vascular system in rats even in the absence of hypercholesterolemia.

Synthesis and characterization of Pseudomonas aeruginosa alginate–tetanus toxoid conjugate

Chronic infection withPseudomonas aeruginosais the main proven perpetrator of lung function decline and ultimate mortality in cystic fibrosis (CF) patients. Mucoid strains of this bacterium elaborate mucoid exopolysaccharide, also referred to as alginate. Alginate-based immunization of naïve animals elicits opsonic antibodies and leads to clearance of mucoidP. aeruginosafrom the lungs. Alginate was isolated from mucoidP. aeruginosastrain 8821M by repeated ethanol precipitation, dialysis, proteinase and nuclease digestion, and chromatography. To improve immunogenicity, the purified antigen was coupled to tetanus toxoid (TT) with adipic acid dihydrazide (ADH) as a spacer and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDAC) as a linker. The reaction mixture was passed through a Sepharose CL-4B column. The resulting conjugate was composed of TT and large-size alginate polymer at a ratio of about 3 : 1; it was non-toxic and non-pyrogenic, and elicited high titres of alginate-specific IgG. Antisera raised against the conjugate had high opsonic activity against the vaccine strain. The alginate conjugate was also able to protect mice against a lethal dose of mucoidP. aeruginosa. These data indicate that an alginate-based vaccine has significant potential to protect against chronic infection with mucoidP. aeruginosain the CF host.

Effects of intratracheal administration of novispirin G10 on a rat model of mucoid Pseudomonas aeruginosa lung infection

Chronic Pseudomonas aeruginosa lung infection is a major problem for patients with cystic fibrosis (CF). The biofilm mode of growth of the pathogen makes it highly resistant to antibiotic treatment, and this is especially pronounced with mucoid strains. In this study, novispirin G10, a synthetic antimicrobial peptide patterned loosely on sheep myeloid antimicrobial peptide 29, was tested in a rat model of mucoid P. aeruginosa lung infection. P. aeruginosa NH57388A, a mucoid strain isolated from a CF patient, was mixed with the alginate produced by the bacterium itself and adjusted to a concentration of 10(10) CFU/ml. Each rat received 10(9) CFU of bacteria intratracheally in the left lung to establish lung infection. At 0 and 3 h post P. aeruginosa infection, the treated group of rats received novispirin G10 (0.1 mg/ml, 0.1 ml/rat) intratracheally, whereas the control group received vehicle treatment only. The animals were sacrificed on days 3, 5, 7, and 10 after challenge for evaluation of various parameters. On day 5, 50% of the rats in the treated group had cleared the bacteria from the lungs, whereas in the control group, none of the rats cleared the pathogen (P < 0.03). The average bacterial loads remaining in the lungs of treated rats on days 3 and 5 were more than 170- and 330-fold lower than in the control groups (P < 0.0005 and P < 0.0003). In accordance, the macroscopic and microscopic lung pathology was also significantly milder in the treated group compared to the control group (P < 0.0002). Lung cytokine responses in the treated group were significantly lower than in the control group. The results suggest that novispirin G10 might be useful in treating antibiotic-resistant P. aeruginosa lung infections.

Effects of quorum-sensing on immunoglobulin G responses in a rat model of chronic lung infection with Pseudomonas aeruginosa

Levels of serum antibodies against Pseudomonas aeruginosa were observed for 106 days in a rat model of chronic lung infection. Significantly weaker responses of serum IgG and IgG1 and a lower ratio of IgG1/IgG2a were found in the rats infected with the quorum-signal-deficient mutant, PAO1 (rhlI, lasI), compared with the wild-type PAO1. Four out of 15 rats infected with wild-type PAO1 contained bacteria in the lungs on day 106, whereas no bacteria were found in the mutant PAO1 group. The results indicate that quorum signals contribute to the persistence of the infection and influence the immune response.

Cytokine modulating effect of ginseng treatment in a mouse model of Pseudomonas aeruginosa lung infection

The major cause of morbidity and mortality in cystic fibrosis (CF) patients is chronic Pseudomonas aeruginosa lung infection. In a mouse model of P. aeruginosa lung infection mimicking that in CF patients, the effects of ginseng treatment on cytokine responses and the correlation between the changes in cytokine production and the lung pathology were studied. Mice were challenged with alginate beads containing P. aeruginosa (10(9) CFU/ml). A saline extract of ginseng was injected subcutaneously at a dosage of 250 mg/kg of body weight/day for 7 days. Saline was used as a placebo control. One week after challenge, a significantly lower mortality was found in the ginseng treated group (P < 0.005). The lung cells from the ginseng treated group produced more interferon-gamma (IFN-gamma) (P < 0.04) and tumor necrosis factor-alpha (TNF-alpha) (P < 0.03) but less interleukin-4 (IL-4) (P < 0 .02) with a higher ratio of IFN-gamma/IL-4 (P < 0.004) after 6 and/or 24 h of incubation with specific and non-specific antigens as compared to the control group. The ginseng treated splenocytes produced more TNF-alpha (P < 0.03) and IFN-gamma (P0.05) than the control spleen cells. Furthermore, a significantly milder lung pathology (P < 0.025) and a faster bacterial clearance (P < 0.038) from the lungs were also found in the ginseng treated group compared to the control group. These results indicate a Th1-like immune response in the mice with P. aeruginosa lung infection after 7 days of ginseng treatment, which is an important mechanism accounting for ginseng's favorable action. We therefore believe that Th1 response might benefit the host with P. aeruginosa lung infection and ginseng treatment might be a promising alternative measure for the treatment of chronic P. aeruginosa lung infection in CF patients.

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.

Construction and characterization of a Pseudomonas aeruginosa mucoid exopolysaccharide-alginate conjugate vaccine

Deterioration of lung function in patients with cystic fibrosis (CF) is closely associated with chronic pulmonary infection with mucoid Pseudomonas aeruginosa. The mucoid exopolysaccharide (MEP) from P. aeruginosa has been shown to induce opsonic antibodies in mice that are protective against this chronic infection. MEP-specific opsonic antibodies are also commonly found in the sera of older CF patients lacking detectable P. aeruginosa infection. When used in a human vaccine trial, however, MEP only minimally induced opsonic antibodies. To evaluate whether conjugation of MEP to a carrier protein could improve its immunogenicity, we bound thiolated MEP to keyhole limpet hemocyanin (KLH) by using succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) as a linker. In contrast to the native MEP polymer, the MEP-KLH conjugate vaccine induced high titers of MEP-specific immunoglobulin G (IgG) in C3H-HeN mice and in a rabbit. Sera from mice immunized with MEP-KLH conjugate, but not from animals immunized with comparable doses of native MEP, demonstrated opsonic killing activity. Vaccination with MEP-KLH conjugate induced opsonic antibodies broadly cross-reactive to heterologous mucoid strains of P. aeruginosa. Preexisting nonopsonic antibodies to MEP are found in normal human sera, including young CF patients, and their presence impedes the induction of opsonic antibodies. Induction of nonopsonic antibodies by either intraperitoneal injection of MEP or injection or feeding of the cross-reactive antigen, seaweed alginate, reduced the level of overall IgG elicited by follow-up immunization with the MEP-KLH conjugate. However, the opsonic activity was lower only in the sera of MEP-KLH conjugate-immunized mice with preexisting antibodies induced by MEP but not with antibodies induced by seaweed alginate. Immunization with MEP-KLH elicited a significant proportion of antibodies specific to epitopes involving O-acetate residues, and this subpopulation of antibodies mediated opsonic killing of mucoid P. aeruginosa in vitro. These results indicate that conjugation of MEP to KLH significantly enhances its immunogenicity and the elicitation of opsonic antibodies in mice and rabbits, that the conjugate induces opsonic antibodies in the presence of preexisting nonopsonic antibodies, and that opsonic antibodies to MEP are directed at epitopes that include acetate residues on the uronic acid polymer.

Gerimax ginseng regulates both humoral and cellular immunity during chronic Pseudomonas aeruginosa lung infection

BACKGROUND

Chronic lung infection among patients with cystic fibrosis (CF), diffused panbronchiolitis, and chronic obstructive bronchiecteisis is often because of Pseudomonas aeruginosa. High morbidity and mortality in patients with CF are because of P. aeuruginosa that undergoes genotypic and phenotypic changes during prolonged stay in the lung resulting in increased antibiotic resistance, necessitating a search for alternative or supplement drugs.

OBJECTIVE

In this study we compared the therapeutical effect of Gerimax (Dansk Droge A/S, Ishøj, Denmark) ginseng with placebo control by using a rat model of chronic P. aeruginosa lung infection mimicking that in patients with CF.

METHODS AND INTERVENTIONS

The animals were challenged intratracheally with the prototypic P. aeruginosa PAO1 in alginate beads (1 x 10(9) colony-forming units per milliliter [CFU/mL]) followed by subcutaneous injection of ginseng extract (150 mg/kg body weight once per day) and examined on days 7 and 21.

RESULTS

The day 7 analyses show that ginseng treatment resulted in lowering serum immunoglobulin M (IgM) and lung interleukin-4 (IL-4) levels compared to the control group. On day 21, higher lung IgA, upregulated serum IgG2a, stronger lung responses of interferon-gamma, IL-4, and tumor necrosis factor-alpha with milder lung pathology and enhanced lung bacteriology were detected in the ginseng-treated group when compared to those of the control group.

CONCLUSION

These results suggest that the Gerimax ginseng treatment can modulate the immune system in favor of clearing the infection with P. aeruginosa in the lungs of rats. Thus, ginseng might be a promising alternative supplement for the treatment of chronic P. aeruginosa lung infection in patients with CF.

Pseudomonas aeruginosa mutations in lasI and rhlI quorum sensing systems result in milder chronic lung infection

To understand the importance of quorum sensing in chronic Pseudomonas aeruginosa lung infection, the in vivo pathogenic effects of the wild-type P. aeruginosa PAO1 and its double mutant, PAO1 lasI rhlI, in which the signal-generating parts of the quorum sensing systems are defective were compared. The rat model of P. aeruginosa lung infection was used in the present study. The rats were killed on days 3, 7, 14 and 28 after infection with the P. aeruginosa strains. The results showed that during the early stages of infection, the PAO1 double mutant induced a stronger serum antibody response, higher production of pulmonary interferon gamma, and more powerful blood polymorphonuclear leukocyte (PMN) chemiluminescence compared to its wild-type counterpart. On days 14 and 28 post-infection, significantly milder lung pathology, a reduction in the number of mast cells present in the lung foci, a reduced number of lung bacteria, and minor serum IgG and IgG1 responses but increased lung interferon gamma production were detected in the group infected with the PAO1 double mutant when compared with the PAO1-infected group. Delayed immune responses were observed in the PAO1-infected group and they might be associated with the production of virulence factors that are controlled by the quorum sensing systems. The conclusion of this study is that functional lasI and rhlI genes of P. aeruginosa PAO1 play a significant role during lung infection.

The recombinant Azotobacter vinelandii mannuronan C-5-epimerase AlgE4 epimerizes alginate by a nonrandom attack mechanism

The Ca2+-dependent mannuronan C-5-epimerase AlgE4 is a representative of a family of Azotobacter vinelandii enzymes catalyzing the polymer level epimerization of beta-D-mannuronic acid (M) to alpha-L-guluronic acid (G) in the commercially important polysaccharide alginate. The reaction product of recombinantly produced AlgE4 is predominantly characterized by an alternating sequence distribution of the M and G residues (MG blocks). AlgE4 was purified after intracellular overexpression in Escherichia coli, and the activity was shown to be optimal at pH values between 6.5 and 7.0, in the presence of 1-3 mM Ca2+, and at temperatures near 37 degrees C. Sr2+ was found to substitute reasonably well for Ca2+ in activation, whereas Zn2+ strongly inhibited the activity. During epimerization of alginate, the fraction of GMG blocks increased linearly as a function of the total fraction of G residues and comparably much faster than that of MMG blocks. These experimental data could not be accounted for by a random attack mechanism, suggesting that the enzyme either slides along the alginate chain during catalysis or recognizes a pre-existing G residue as a preferred substrate in its consecutive attacks.

Effects of ginseng treatment on neutrophil chemiluminescence and immunoglobulin G subclasses in a rat model of chronic Pseudomonas aeruginosa pneumonia

Chronic Pseudomonas aeruginosa lung infection in cystic fibrosis (CF) patients is almost impossible to eradicate with antibiotic treatment. In the present study, the effects of treatment with the Chinese herbal medicine ginseng on blood polymorphonuclear leukocyte (PMN) chemiluminescence and serum specific antibody responses were studied in a rat model of chronic P. aeruginosa pneumonia mimicking CF. An aqueous extract of ginseng was administered by subcutaneous injection at a dosage of 25 mg/kg of body weight/day for 2 weeks. Saline was used as a control. Two weeks after the start of ginseng treatment, significantly increased PMN chemiluminescence (P Collapse

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MESH Headings

• Animals
• Antibodies, Bacterial/blood
• Bronchoalveolar Lavage Fluid/cytology
• Cystic Fibrosis/complications
• Disease Models, Animal
• Female
• Immunoglobulin G/blood
• Luminescent Measurements
• Lung/pathology
• Macrophages, Alveolar/immunology
• Macrophages, Alveolar/metabolism
• Neutrophil Activation
• Neutrophils/immunology
• Panax/therapeutic use
• Phytotherapy
• Plant Extracts/therapeutic use
• Plants, Medicinal
• Pneumonia, Bacterial/drug therapy
• Pneumonia, Bacterial/immunology
• Pneumonia, Bacterial/pathology
• Pseudomonas Infections/drug therapy
• Pseudomonas Infections/immunology
• Pseudomonas Infections/pathology
• Pseudomonas aeruginosa/immunology
• Rats
• Rats, Inbred Lew
• Respiratory Burst

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Affiliation(s)

Z Song Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
A Kharazmi
H Wu
V Faber
C Moser
H K Krogh
J Rygaard
N Hoiby

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Ginseng treatment reduces bacterial load and lung pathology in chronic Pseudomonas aeruginosa pneumonia in rats

The predominant pathogen in patients with cystic fibrosis (CF) is Pseudomonas aeruginosa, which results in a chronic lung infection associated with progressive pulmonary insufficiency. In a rat model of chronic P. aeruginosa pneumonia mimicking that in patients with CF, we studied whether the inflammation and antibody responses could be changed by treatment with the Chinese herbal medicine ginseng. An aqueous extract of ginseng was injected subcutaneously, and cortisone and saline were used as controls. Two weeks after challenge with P. aeruginosa, the ginseng-treated group showed a significantly improved bacterial clearance from the lungs (P < 0.04), less severe lung pathology (P = 0.05), lower lung abscess incidence (P < 0.01), and fewer mast cell numbers in the lung foci (P < 0.005). Furthermore, lower total immunoglobulin G (IgG) levels (P < 0.01) and higher IgG2a levels (P < 0.025) in serum against P. aeruginosa sonicate and a shift from an acute type to a chronic type of lung inflammation compared to those in the control and cortisone-treated groups were observed. These findings indicate that ginseng treatment of an experimental P. aeruginosa pneumonia in rats promotes a cellular response resembling a TH1-like response. On the basis of these results it is suggested that ginseng may have the potential to be a promising natural medicine, in conjunction with other forms of treatment, for CF patients with chronic P. aeruginosa lung infection.

Is the pretreatment effect of low dose Freund's adjuvant on adjuvant arthritis due to an activation of the nervous system?

It has been recently shown that pretreatment with a low dose of Freund's adjuvant decreases the severity of adjuvant arthritis in rats. To study the involvement of the central and peripheral nervous systems in the pretreatment effect, concentrations of substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivities (-LI) were measured in the cerebrospinal fluid, plasma and synovial fluid 2 and 24 h after a single s.c. injection of 0.05 mg Freund's adjuvant. Increased concentrations of CGRP-LI were found in the cerebrospinal fluid, plasma and synovial fluid. NPY-LI was decreased in the cerebrospinal fluid while NKA-LI was decreased in plasma. In the synovial fluid, SP-LI was increased at 24 h and NKA-LI was increased at 2 h following treatment. Our results indicate that part of pretreatment effect of low dose of subcutaneous Freund's adjuvant in the rat may be attributed to neurogenic mechanisms.

Microbial pathogenesis in cystic fibrosis: mucoid Pseudomonas aeruginosa and Burkholderia cepacia

Respiratory infections with Pseudomonas aeruginosa and Burkholderia cepacia play a major role in the pathogenesis of cystic fibrosis (CF). This review summarizes the latest advances in understanding host-pathogen interactions in CF with an emphasis on the role and control of conversion to mucoidy in P. aeruginosa, a phenomenon epitomizing the adaptation of this opportunistic pathogen to the chronic chourse of infection in CF, and on the innate resistance to antibiotics of B. cepacia, person-to-person spread, and sometimes rapidly fatal disease caused by this organism. While understanding the mechanism of conversion to mucoidy in P. aeruginosa has progressed to the point where this phenomenon has evolved into a model system for studying bacterial stress response in microbial pathogenesis, the more recent challenge with B. cepacia, which has emerged as a potent bona fide CF pathogen, is discussed in the context of clinical issues, taxonomy, transmission, and potential modes of pathogenicity.

Pulmonary immunity to Pseudomonas aeruginosa

Pseudomonas aeruginosa, an opportunistic bacterial pathogen, is a major course of morbidity and mortality in subjects with compromised respiratory function despite the significant advances in therapeutic practices. The bacteria produces an armoury of products which modify its infective niche to ensure bacterial survival. The role of antibody in protection against pulmonary infection remains poorly defined. Protection appears to be associated with opsonizing antibody whilst some other antibody responses may be deleterious and promote further lung damage. Cell mediated responses are clearly important in protection against infection. This review proposes a vaccine strategy aimed at enhancing specific T cell responses in the lung which, though T cell-derived cytokines, drive the recruitment of neutrophils to the lung and the subsequent activation of these cells results in the clearance of bacteria from the lung.