Do Neutrophils Play a Role in Establishing Liver Abscesses and Distant Metastases Caused by Klebsiella pneumoniae?

Serotype K1 Klebsiella pneumoniae is a major cause of liver abscesses and endophthalmitis. This study was designed to identify the role of neutrophils in the development of distant metastatic complications that were caused by serotype K1 K. pneumoniae. An in vitro cellular model was used to assess serum resistance and neutrophil-mediated killing. BALB/c mice were injected with neutrophils containing phagocytosed K. pneumoniae. Serotype K1 K. pneumoniae was significantly more resistant to serum killing, neutrophil-mediated phagocytosis and intra-cellular killing than non-K1 isolates (p<0.01). Electron microscopic examination had similar findings as in the bioassay findings. Intraperitoneal injection of neutrophils containing phagocytosed serotype K1 K. pneumoniae led to abscess formation in multiple sites including the subcutaneous tissue, lung, and liver, whereas no abscess formation was observed in mice injected with non-K1 isolates. The resistance of serotype K1 K. pneumoniae to complement- and neutrophil-mediated intracellular killing results in the dissemination of K. pneumoniae via the bloodstream. Escape from neutrophil intracellular killing may contribute to the dissemination and establishment of distant metastases. Thus, neutrophils play a role as a vehicle for helping K. pneumoniae and contributing to the establishment of liver abscess and distant metastatic complications

In-Vivo Expression Profiling of Pseudomonas aeruginosa Infections Reveals Niche-Specific and Strain-Independent Transcriptional Programs

Pseudomonas aeruginosa is a threatening, opportunistic pathogen causing disease in immunocompromised individuals. The hallmark of P. aeruginosa virulence is its multi-factorial and combinatorial nature. It renders such bacteria infectious for many organisms and it is often resistant to antibiotics. To gain insights into the physiology of P. aeruginosa during infection, we assessed the transcriptional programs of three different P. aeruginosa strains directly after isolation from burn wounds of humans. We compared the programs to those of the same strains using two infection models: a plant model, which consisted of the infection of the midrib of lettuce leaves, and a murine tumor model, which was obtained by infection of mice with an induced tumor in the abdomen. All control conditions of P. aeruginosa cells growing in suspension and as a biofilm were added to the analysis. We found that these different P. aeruginosa strains express a pool of distinct genetic traits that are activated under particular infection conditions regardless of their genetic variability. The knowledge herein generated will advance our understanding of P. aeruginosa virulence and provide valuable cues for the definition of prospective targets to develop novel intervention strategies

Immunogenicity and efficacy of oral vaccines in developing countries: lessons from a live cholera vaccine

Oral vaccines, whether living or non-living, viral or bacterial, elicit diminished immune responses or have lower efficacy in developing countries than in developed countries. Here I describe studies with a live oral cholera vaccine that include older children no longer deriving immune support from breast milk or maternal antibodies and that identify some of the factors accounting for the lower immunogenicity, as well as suggesting counter-measures that may enhance the effectiveness of oral immunization in developing countries. The fundamental breakthrough is likely to require reversing effects of the 'environmental enteropathy' that is often present in children living in fecally contaminated, impoverished environments

Cyclic-di-GMP regulates lipopolysaccharide modification and contributes to Pseudomonas aeruginosa immune evasion

Pseudomonas aeruginosa is a Gram-negative bacterial pathogen associated with acute and chronic infections. The universal c-di-GMP second messenger is instrumental in the switch from a motile lifestyle to resilient biofilm as in the cystic fibrosis lung. The SadC diguanylate cyclase is associated with this patho-adaptive transition. Here we identified an unrecognized SadC partner, WarA, which we show is a methyltransferase in complex with a putative kinase WarB. We established that WarA binds to c-di-GMP, which potentiates its methyltransferase activity. Together, WarA and WarB have structural similarities with the bi-functional Escherichia coli LPS O antigen regulator WbdD. Strikingly, WarA influences P. aeruginosa O antigen modal distribution and interacts with the LPS biogenesis machinery. LPS is known to modulate the immune response in the host, and by using a zebrafish infection model, we implicate WarA in the ability of P. aeruginosa to evade detection by the host.BBSRC & Wellcome Trus

Cellular immunity in healthy volunteers treated with an octavalent conjugate Pseudomonas aeruginosa vaccine

Humoral immunity in response to an octavalent O-polysaccharide-toxin A conjugate Pseudomonas aeruginosa vaccine is well studied, and a phase III clinical study in cystic fibrosis (CF) patients is currently ongoing. In contrast, little is known about cellular immunity induced by this vaccine. Fifteen healthy volunteers were immunized on days 1 and 60. Parameters of cellular immunity were studied before vaccination on day 1, and on day 74. Analyses included flow cytometry of whole blood and antigen-induced proliferation of and cytokine production by lymphocyte cultures. The effects of immunization on the composition of peripheral blood lymphocytes as determined by flow cytometry were minor. In contrast, after immunization a highly significant increase of proliferation in response to stimulation with detoxified toxin A was noted: the stimulation index rose from 1·4 on day 1 to 42·2 on day 74 (restimulation with 0·4 µg/ml; P = 0·003). Immunization led to significant production of interferon (IFN)-γ and tumour necrosis factor (TNF)-α by antigen-stimulated lymphocytes. In contrast, no significant induction of interleukin (IL)-4 or IL-10 was observed. In conclusion, immunization of healthy volunteers led to activation of cellular immunity including strong antigen-specific proliferation and cytokine production. In CF patients priming of the cellular immune system towards a Th1-like pattern would be of potential advantage. Therefore, confirmatory analyses in immunized CF patients with and without chronic infection with P. aeruginosa are foreseen

Cellular immunity in healthy volunteers treated with an octavalent conjugate Pseudomonas aeruginosa vaccine

Humoral immunity in response to an octavalent O-polysaccharide-toxin A conjugate Pseudomonas aeruginosa vaccine is well studied, and a Phase III clinical study in cystic fibrosis (CF) patients is currently ongoing. In contrast, little is known about cellular immunity induced by this vaccine. Fifteen healthy volunteers were immunized on days 1 and 60. Parameters of cellular immunity were studied before vaccination on day 1, and on day 74. Analyses included flow cytometry of whole blood, and antigen-induced proliferation of and cytokine production by lymphocyte cultures. The effects of immunization on the composition of peripheral blood lymphocytes as determined by flow cytometry were minor. In contrast, after immunization a highly significant increase of proliferation in response to stimulation with detoxified toxin A was noted: the stimulation index rose from 1·4 on day 1 to 42·2 on day 74 (restimulation with 0·4 µg/ml; P = 0·003). Immunization led to significant production of interferon (IFN)-γ and tumour necrosis factor (TNF)-α by antigen-stimulated lymphocytes. In contrast, no significant induction of interleukin (IL)-4 or IL-10 was observed. In conclusion, immunization of healthy volunteers led to activation of cellular immunity including strong antigen-specific proliferation and cytokine production. In CF patients priming of the cellular immune system towards a Th1-like pattern would be of potential advantage. Therefore, confirmatory analyses in immunized CF patients with and without chronic infection with P. aeruginosa are foreseen

Escherichia coli strains isolated from pigs with edema disease produce a variant of Shiga-like toxin II

Escherichia coli O157:H7 strains 933 produces elevated levels of 2 phage-encoded, antigenically distinct cytotoxins designated Shiga-like toxin I (SLT-I) and Shiga-like toxin II (SLT-II). These toxins kill both HeLa and Vero cells. In this report, the relationship between SLTs and a cytotoxin produced by E. coli strains isolated from pigs with edema disease (ED) was examined. Culture filtrates from 72 out of 81 ED strains were cytotoxic for Vero but not HeLa cells. Cytotoxicity was neutralized by antiserum to SLT-II but not by anti-Shiga toxin. No toxin-converting phage were detected in 20 toxigenic ED strains examined. The cytotoxin of the ED-causing strains appears to be a variant of SLT-II and production of this cytotoxin is not phage-mediated. © 1987.link_to_subscribed_fulltex