Pseudomonas aeruginosa exoenzyme S induces proliferation of human T lymphocytes

Abnormal functional lymphoid tolerance and enhanced myeloid exocytosis are characteristics of resting and stimulated PBMCs in cystic fibrosis patients

Introduction

Cystic Fibrosis (CF) is the commonest genetically inherited disease (1 in 4,500 newborns) and 70% of people with CF (pwCF) harbour the F508Del mutation, resulting in misfolding and incorrect addressing of the channel CFTR to the epithelial membrane and subsequent dysregulation of fluid homeostasis. Although studies have underscored the importance and over-activation of myeloid cells, and in particular neutrophils in the lungs of people with CF (pwCF), relatively less emphasis has been put on the potential immunological bias in CF blood cells, at homeostasis or following stimulation/infection.

Methods

Here, we revisited, in an exhaustive fashion, in pwCF with mild disease (median age of 15, median % FEV1 predicted = 87), whether their PBMCs, unprimed or primed with a 'non specific' stimulus (PMA+ionomycin mix) and a 'specific' one (live P.a =PAO1 strain), were differentially activated, compared to healthy controls (HC) PBMCs.

Results

1) we analysed the lymphocytic and myeloid populations present in CF and Control PBMCs (T cells, NKT, Tgd, ILCs) and their production of the signature cytokines IFN-g, IL-13, IL-17, IL-22. 2) By q-PCR, ELISA and Luminex analysis we showed that CF PBMCs have increased background cytokines and mediators production and a partial functional tolerance phenotype, when restimulated. 3) we showed that CF PBMCs low-density neutrophils release higher levels of granule components (S100A8/A9, lactoferrin, MMP-3, MMP-7, MMP-8, MMP-9, NE), demonstrating enhanced exocytosis of potentially harmful mediators.

Discussion

In conclusion, we demonstrated that functional lymphoid tolerance and enhanced myeloid protease activity are key features of cystic fibrosis PBMCs.

Recipient Age Impacts Long-Term Survival in Adult Subjects with Cystic Fibrosis after Lung Transplantation

Rationale: Lung transplant is an effective treatment option providing survival benefit in patients with cystic fibrosis (CF). Several studies have suggested survival benefit in adults compared with pediatric patients with CF undergoing lung transplant. However, it remains unclear whether this age-related disparity persists in adult subjects with CF.Objectives: We investigated the impact of age at transplant on post-transplant outcomes in adult patients with CF.Methods: The United Network of Organ Sharing Registry was queried for all adult patients with CF who underwent lung transplantation between 1992 and 2016. Pertinent baseline characteristics, demographics, clinical parameters, and outcomes were recorded. The patients were divided into two groups based on age at transplant (18-29 yr old and 30 yr or older). The primary endpoint was survival time. Assessment of post-transplant survival was performed using Kaplan-Meier tests and log-rank tests with multivariable Cox proportional hazards analysis to adjust for confounding variables.Results: A total of 3,881 patients with CF underwent lung transplantation between 1992 and 2016; mean age was 31.0 (± 9.3) years. The 18-29-year-old at transplant cohort consisted of 2,002 subjects and the 30 years or older cohort had 1,879 subjects. Survival analysis demonstrated significantly higher survival in subjects in the 30 years or older cohort (9.47 yr; 95% confidence interval [CI], 8.7-10.2) compared with the 18-29-year-old cohort (5.21 yr; 95% CI, 4.6-5.8). After adjusting for confounders, survival remained higher in recipients aged 30 years or older (hazard ratio, 0.44; 95% CI, 0.2-0.9). Mortality due to allograft failure was significantly lower in patients with CF aged 30 years or older (28% vs. 36.5%; odds ratio [OR], 0.7; 95% CI, 0.6-0.8), whereas the incidence of malignancy was higher in the 30 years or older cohort (8% vs. 2.9%; OR, 3.0; 95% CI, 1.9-4.6).Conclusions: Age at transplant influences lung transplant outcomes in recipients with CF. Subjects with CF aged 30 years or older at transplant have superior survival compared with adult subjects with CF transplanted between the ages 18 and 29 years.

Infectious Triggers of Chronic Lung Allograft Dysfunction

Survival after lung transplantation is limited in large part due to the high incidence of chronic rejection, known as chronic lung allograft dysfunction (CLAD). Pulmonary infections are a frequent complication in lung transplant recipients, due both to immunosuppressive medications and constant exposure of the lung allograft to the external environment via the airways. Infection is a recognized risk factor for the development of CLAD, and both acute infection and chronic lung allograft colonization with microorganisms increase the risk for CLAD. Acute infection by community acquired respiratory viruses, and the bacteria Pseudomonas aeruginosa and Staphylococcus aureus are increasingly recognized as important risk factors for CLAD. Colonization by the fungus Aspergillus may also augment the risk of CLAD. Fostering this transition from healthy lung to CLAD in each of these infectious episodes is the persistence of an inflammatory lung allograft environment.

Pre-transplant Panel Reactive Antibody and Survival in Adult Cystic Fibrosis Patients After Lung Transplantation

BACKGROUND

Survival implications of pre-transplant antibodies to human leukocyte antigens prior to lung transplantation (LTx) in adult cystic fibrosis (CF) patients are unknown.

METHODS

Data from the United Network for Organ Sharing Registry (1987-2013) were used to compare survival differences in adult CF patients with pre-transplant class I and II panel reactive antibody (PRA) levels ≤10 versus >10 %.

RESULTS

Of 3149 CF LTx recipients, 1526 and 1399 were included in univariate survival analyses of class I and II PRA, respectively, while 1106 and 1001 were included in multivariate Cox analyses for class I and class II, respectively. Kaplan-Meier survival functions failed to demonstrate significant differences in survival with PRA >10 % for class I (Log-rank test: χ (2) (df = 1): 1.11, p = 0.293) or class II (Log-rank test: χ (2) (df = 1): 0.99, p = 0.320). Adjusting for covariates, multivariate Cox models demonstrated that class II PRA >10 % was associated with a significant increase in mortality hazard (HR 1.918; 95 % CI 1.128, 3.261; p = 0.016), whereas class I PRA >10 % was uncorrelated with this outcome.

CONCLUSIONS

Pre-transplant PRA class II >10 % in adult CF patients is associated with elevated mortality hazard after LTx.

Human leukocyte antigen mismatching and survival after lung transplantation in adult and pediatric patients with cystic fibrosis

INTRODUCTION

The influence of human leukocyte antigen (HLA) mismatching on survival in adult and pediatric patients with cystic fibrosis (CF) after lung transplantation (LTx) is unknown.

METHODS

The United Network for Organ Sharing database was queried from 1987 to 2013 to determine the influence of HLA mismatching on survival in adult and pediatric CF LTx recipients by assessing the association of HLA mismatching with survival in first-time adult (aged ≥ 18 years) and pediatric (aged <18 years) recipients.

RESULTS

Of 3149 adult and 489 pediatric patients with CF, 3145 and 489 were used for univariate Cox analysis, 2687 and 363 for Kaplan-Meier survival analysis, and 2073 and 257 for multivariate Cox analysis, respectively. Univariate analyses in adult and pediatric patients with CF demonstrated conflicting associations between HLA mismatching and survival (adult hazard ratio [HR], 1.0; 95% confidence interval [CI], 0.97-1.1; P = .45 vs pediatric HR, 0.87; 95% CI, 0.77-0.99; P = .032). Multivariate Cox models including both pediatric and adult patients confirmed that HLA mismatching had an initially protective effect at young ages (HR, 0.85; 95% CI, 0.73-0.99; P = .044) and that this protective effect diminished at older ages and was no longer associated with survival at P < .05 beyond age 10 years.

CONCLUSIONS

HLA mismatching has significantly different implications for survival after LTx in adult compared with pediatric patients with CF.

Different domains of Pseudomonas aeruginosa exoenzyme S activate distinct TLRs

Some bacterial products possess multiple immunomodulatory effects and thereby complex mechanisms of action. Exogenous administration of an important Pseudomonas aeruginosa virulence factor, exoenzyme S (ExoS) induces potent monocyte activation leading to the production of numerous proinflammatory cytokines and chemokines. However, ExoS is also injected directly into target cells, inducing cell death through its multiple effects on signaling pathways. This study addresses the mechanisms used by ExoS to induce monocyte activation. Exogenous administration resulted in specific internalization of ExoS via an actin-dependent mechanism. However, ExoS-mediated cellular activation was not inhibited if internalization was blocked, suggesting an alternate mechanism of activation. ExoS bound a saturable and specific receptor on the surface of monocytic cells. ExoS, LPS, and peptidoglycan were all able to induce tolerance and cross-tolerance to each other suggesting the involvement of a TLR in ExoS-recognition. ExoS activated monocytic cells via a myeloid differentiation Ag-88 pathway, using both TLR2 and the TLR4/MD-2/CD14 complex for cellular activation. Interestingly, the TLR2 activity was localized to the C-terminal domain of ExoS while the TLR4 activity was localized to the N-terminal domain. This study provides the first example of how different domains of the same molecule activate two TLRs, and also highlights the possible overlapping pathophysiological processes possessed by microbial toxins.

Increased resistance in BALB/c mice to reinfection with Candida albicans is due to immunoneutralization of a virulence-associated immunomodulatory protein

Here, it is shown that immunoneutralization of p43, a virulence-associated immunomodulatory protein secreted by Candida albicans, is responsible for immunoprotection against candidiasis after spontaneous healing of mice inoculated with 10(6) C. albicans blastoconidia. p43 is produced by the pathogenic Candida blastoconidia, and neither immunoprotection nor immunoneutralization can be elicited by priming the mice with attenuated or heat-killed C. albicans blastoconidia. The immunoprotection against systemic candidiasis was positively correlated with (i). serum levels of antibodies against p43 and (ii). a high ratio between antibodies against p43 and antibodies against C. albicans structural antigens. Immunoprotection against candidiasis can be induced in mice primed with heat-killed C. albicans, after treatment of the animals with anti-p43 antibodies. The data described here provide a biological explanation for active immunoprotection achieved after spontaneous healing of infectious diseases, namely in candidiasis.

Characterization of T cell clones derived from lymph nodes and lungs of Pseudomonas aeruginosa-susceptible and resistant mice following immunization with heat-killed bacteria

Pseudomonas aeruginosa-resistant BALB/c and susceptible C57Bl/6 (B6) mice were immunized with heat-killed Pseudomonas either in the foot pad or via the trachea, and panels of Pseudomonas-specific T cell clones were developed from lymph nodes and lungs. All clones from either strain, whether of lymph node or lung origin, were CD3+CD4+CD8-TCRalphabeta+. The efficacy of cloning from lymph node cells was comparable between BALB/c and B6 mice. All lymph node BALB/c clones proliferated in response to Pseudomonas antigen in a dose-dependent manner, and this response was MHC class II-restricted. Vigorous proliferation by a considerable proportion of B6 T cell clones occurred in the absence of specific antigen. Lymph node clones from either strain could be categorized as either Th1 or Th0 on the basis of interferon-gamma (IFN-gamma)/IL-4 production. In either mouse strain the efficacy of cloning from lung tissue was substantially lower than from lymph nodes, but the efficacy of cloning from BALB/c compared with B6 lungs was higher. Four lung T cell clones from BALB/c and two from B6 mice were expanded for further analyses, and an interstrain difference was observed in cytokine production. Both B6 lung T cell clones were Th1-like and produced IFN-gamma but not IL-4 and IL-10, whereas four BALB/c lung T cell clones were Th2-like and produced IL-4 and IL-10 but not IFN-gamma. These observations suggest that differences in the CD4+ Th response in the lung may contribute to differences among inbred mouse strains in the level of resistance to bronchopulmonary Pseudomonas infection.

Pseudomonas aeruginosa exoenzyme S induces transcriptional expression of proinflammatory cytokines and chemokines

Pseudomonas aeruginosa infection of cystic fibrosis patients causes lung damage that is substantially orchestrated by cytokines. In this study, multi-gene probe analysis was used to characterize the ability of the P. aeruginosa mitogen, exoenzyme S, to induce proinflammatory and immunoregulatory cytokines and chemokines. Exoenzyme S strongly induced transcription of proinflammatory cytokines and chemokines (tumor necrosis factor alpha, interleukin-1alpha [IL-1alpha], IL-1beta, IL-6, IL-8, MIP-1alpha, MIP-1beta, MCP-1, RANTES, and I-309), modest transcription of immunoregulatory cytokines (IL-10 and IL-12p40), and weak transcription of Th1 cytokines (IL-2 and gamma interferon). The response occurred early and subsided without evolving over time. These data suggest that cells responding to exoenzyme S would rapidly express proinflammatory cytokines and chemokines that may contribute to pulmonary inflammation in cystic fibrosis.

Pseudomonas aeruginosa exoenzyme S stimulates murine lymphocyte proliferation in vitro

The exuberant immunoinflammatory response that is associated with Pseudomonas aeruginosa infection is the major source of the morbidity and mortality in cystic fibrosis (CF) patients. Previous studies have established that an exoproduct of P. aeruginosa (exoenzyme S) is a mitogen for human T lymphocytes and activates a larger percentage of T cells than most superantigens, which may contribute to the immunoinflammatory response. An animal model would facilitate studies of the pathophysiologic consequences of this activation. As a first step toward developing an animal model, the murine lymphocyte response to exoenzyme S was examined. When stimulated with exoenzyme S, splenocytes isolated from naive mice entered S phase and proliferated. The optimum response occurred after 2 to 3 days in culture, at 4 x 10(5) cells per well and 5.0 micrograms of exoenzyme S per ml. The response was not due to lipopolysaccharide, since Rhodobacter sphaeroides lipid A antagonist did not block the response. Other preparations of exoenzyme S stimulated lymphocyte proliferation, since the response to recombinant exoenzyme S (rHisExo S) cloned from strain 388 was similar to the response to exoenzyme S from strain DG1. There was evidence that genetic variability influenced the response, since A/J, CBA/J, and C57BL/6 mice were high responders and BALB/cJ mice were low responders following stimulation with exoenzyme S. Both splenic T and B lymphocytes entered the cell cycle in response to exoenzyme S. Thus, murine lymphocytes, like human lymphocytes, respond to P. aeruginosa exoenzyme S, which supports the development of a murine model that may facilitate our understanding of the role that exoenzyme S plays in the pathogenesis of P. aeruginosa infections in CF patients.

RecombinantPseudomonasexoenzyme S and exoenzyme S fromPseudomonas aeruginosaDG1 share the ability to stimulate T lymphocyte proliferation

Exoenzyme S from P. aeruginosa DG1 and recombinant exoenzyme S derived from strain 388 have distinct characteristics, which has led to a controversy about their homology and their pathophysiologic consequences. We have been investigating the ability of exoenzyme S to activate T lymphocytes, and therefore performed studies to determine whether exoenzyme S from P. aeruginosa DG1 and recombinant exoenzyme S derived from strain 388 and expressed in Pseudomonas aeruginosa PA103 or in E. coli BL21(DE3), could induce T lymphocyte activation and proliferation. Both preparations were able to activate T cells and induce lymphocyte proliferation at similar levels as measured by flow cytometry of surface-activation markers and DNA synthesis, respectively. Further, a monoclonal antibody raised against exoenzyme S from strain DG1 partially neutralized T cell activation induced by recombinant exoenzyme S and bound to it in an immunoblot suggesting that the epitope responsible for T cell activation is shared by exoenzyme S from strain DG1 and recombinant exoenzyme S. These data suggest that the two different preparations of exoenzyme S, despite biochemical differences, share the characteristic that is responsible for T lymphocyte activation.Key words: exoenzyme S, Pseudomonas aeruginosa, T lymphocyte, cystic fibrosis.

Pseudomonas aeruginosa exoenzyme S is a mitogen but not a superantigen for human T lymphocytes

Virtually all cystic fibrosis (CF) patients become infected with Pseudomonas aeruginosa, and once the infection is established, the organism is rarely cleared. One of the P. aeruginosa virulence factors, exoenzyme S, has been shown to correlate with increased morbidity and mortality both in rat models of chronic pulmonary inflammation and in human CF patients. It has previously been shown that exoenzyme S is a potent stimulus for the proliferation of T cells in greater than 95% of adults, which could contribute to the pathogenesis of CF. The goal of this study was to determine the mechanism of T-cell stimulation by exoenzyme S in an effort to shed light on the immune response and contribute to understanding its role in P. aeruginosa pathogenesis. The current studies demonstrate that exoenzyme S stimulates naive T cells, since fetal blood lymphocytes proliferated and adult lymphocytes that expressed CD45RA proliferated. The percentage of T cells activated by exoenzyme S after a 4-h culture (as measured by CD69 surface expression) was intermediate in magnitude compared to levels induced by a panel of superantigens and mitogens. To determine the mechanism of activation, the requirement for accessory cells was investigated. The proliferative response to exoenzyme S was dependent on the presence of accessory cells but was not blocked by an anti-DR antibody. Exoenzyme S activated both CD4(+) and CD8(+) T cells, but CD4(+) T cells were preferentially activated. The Vbeta repertoire of donor T cells showed no preferential activation or preferential expansion after stimulation by exoenzyme S, suggesting that it is not a superantigen. Taken together, our data suggest that exoenzyme S is a T-cell mitogen but not a superantigen. Activation of a large percentage of T lymphocytes by exoenzyme S may produce a lymphocyte-mediated inflammatory response that should be considered in the pathogenesis of CF.

In vitro proliferative response of human peripheral blood mononuclear cells to concanavalin A

The proliferation response of human peripheral blood mononuclear cells (PBMC) to concanavalin A (con A) was tested in a medium with or without addition of fetal calf serum (FCS) or a serum substitute. The time profile of the proliferative response of PBMC to con A was different in cells cultured in a medium supplemented with or without FCS. This different pattern occurred for the con A-induced DNA-synthesis as well as for the RNA- or protein-synthesis. The peak proliferation rate and the stimulation index of proliferation of human PBMC to con A was also higher when the cells were cultured in a medium with 10% FCS compared to cells cultured in a FCS-free medium. Substitution of the fetal calf serum by a serum substitute even induced a profound inhibition of the de novo synthesis of DNA in human PBMC. The results indicate that a lymphocyte proliferation response to con A can still be obtained in a culture medium where no FCS was added, although a weaker stimulation occurred in comparison to a culture medium with FCS. However, addition of a serum substitute caused a marked inhibition of the lymphocyte proliferation rate.

Pseudomonas aeruginosa: assessment of risk from drinking water

Pseudomonas aeruginosa is an ubiquitous environmental bacterium. It can be recovered, often in high numbers, in common food, especially vegetables. Moreover, it can be recovered in low numbers in drinking water. A small percentage of clones of P. aeruginosa possesses the required number of virulence factors to cause infection. However, P. aeruginosa will not proliferate on normal tissue but requires previously organs. Further narrowing the risk to human health is that only certain specific hosts are at risk, including patients with profound neutropenia, cystic fibrosis, severe burns, and those subject to foreign device installation. Other than these very well-defined groups, the general population is refractory to infection with P. aeruginosa. Because of its ubiquitous nature, it is not only not practical to eliminate P. aeruginosa from our food and drinking water, but attempts to do so would produce disinfection byproducts more hazardous than the species itself. Moreover, because there is no readily available sensitive and specific means to detect and identify P. aeruginosa available in the field, any potential regulation governing its control would not have a defined laboratory test measure of outcome. Accordingly, attempts to regulate P. aeruginosa in drinking water would not yield public health protection benefits and could, in fact, be counterproductive in this regard.

Potential of preventing Pseudomonas aeruginosa lung infections in cystic fibrosis patients: experimental studies in animals

In patients with cystic fibrosis (CF), respiratory tract infections caused by Staphylococcus aureus and Haemophilus influenzae are followed by Pseudomonas aeruginosa with increasing age. Chronic endobronchial lung infection with P. aeruginosa is the leading cause of morbidity and mortality. In Danish CF patients we noted that both onset of initial colonization and chronic lung infection with P. aeruginosa peaked during the winter months which is the season for respiratory virus infections. Virus may therefore pave the way for P. aeruginosa. We established a chronic P. aeruginosa lung infection in rats by embedding mucoid bacteria in seaweed alginate and installing the beads intratracheally into the lower part of the left lung. Although the rats did not suffer from CF, the antibody responses and the pathologic changes of the lungs mimicked the findings in CF patients. By using this model in normal and athymic rats we showed that the T-cell response during the "natural" course of the infection played no major role. In a model of acute P. aeruginosa pneumonia we found that the macroscopic inflammatory response of the lungs was immense and that the natural capacity to clear P. aeruginosa was very efficient and could not be improved by immunization, although high serum levels of IgM, IgG and IgA antibodies to P. aeruginosa alginate, LPS, exotoxin A and sonicate were induced. We developed a method for collecting and measuring IgA in saliva and noted that mucosal IgA antibodies were induced by vaccination; they did not significantly prevent inflammation, however. In the chronic rat model we succeeded to improve the survival significantly and to change the inflammatory response subsequent to vaccination from an acute type inflammation dominated by polymorphonuclear leukocytes (PMNs) as in CF patients to a chronic type inflammation dominated by mononuclear leukocytes. Furthermore, we found that rats immunized with an alginate containing vaccine had a significantly earlier cellular shift to a chronic type inflammation as well as a significant reduction in the severity of the macroscopic inflammation compared to two other vaccine groups and to nonimmunized controls. Similar results were obtained in rats treated with the TH1 cytokine, interferon-gamma (IFN-gamma). Several authors have shown that the lung tissue damage during chronic infection in CF patients is caused by a type III hypersensitivity reaction leading to release of elastase by PMNs surrounding the bacterial microcolonies. The cellular shift we have induced by vaccination and by IFN-gamma treatment therefore offers a possible new strategy for improving the clinical course in chronically infected CF patients.

Genetic analysis of exoenzyme S expression by Pseudomonas aeruginosa

The dissemination of Pseudomonas aeruginosa to the bloodstream increases the likelihood of developing fatal sepsis. In experimental models, the ability to disseminate is linked to expression of the exoenzyme S pathway. Genetic and biochemical analysis of the pathway has led to the identification of the two structural genes encoding exoenzyme S, exoS and exoT. A key regulator of several loci of the pathway has been identified as a DNA-binding protein with transcriptional activation properties. Preliminary evidence suggests that exoenzyme S and the Yop virulence determinants of yersiniae share homology among proteins involved in their synthesis and secretion. With the addition of exoS and exoT to the molecular arsenal, questions concerning in vivo toxicity and target specificities of exoenzyme S can be directly addressed.

Contribution of specific Pseudomonas aeruginosa virulence factors to pathogenesis of pneumonia in a neonatal mouse model of infection

We sought to identify which Pseudomonas aeruginosa products are involved initiating respiratory tract infection. Defined mutants derived from strain PAO i.e., PAOR1 (lasR),PAO-pmm (algC) (an LPS mutant), and AK1152 (which is Fla- and lacks functional pili), were significantly less virulent than PAO1 in a BALBc/ByJ neonatal mouse model of infection as measured by their abilities to cause acute pneumonia, bacteremia, and death. All three mutants were also less adherent to epithelial cells in an in vitro binding assay. PAOR1 and AK1152 were less able to elicit epithelial production of interleukin-8 than PAO1. LasR was found to be required for the optimal expression of neuraminidase under conditions of increased osmolarity, as might be present in certain pathological conditions. PAO-exsA::omega,, which lacks exoenzyme S expression, was fully virulent, causing at least as much pathology as PAO1. The expression of several P. aeruginosa virulence factors appears to be required to establish pulmonary infection in the neonatal mouse.