Novel nonantibiotic therapies for pneumonia: cytokines and host defense

Predictors of mortality for nursing home-acquired pneumonia: a systematic review

Background. Current risk stratification tools, primarily used for CAP, are suboptimal in predicting nursing home acquired pneumonia (NHAP) outcome and mortality. We conducted a systematic review to evaluate current evidence on the usefulness of proposed predictors of NHAP mortality. Methods. PubMed (MEDLINE), EMBASE, and CINAHL databases were searched for articles published in English between January 1978 and January 2014. The literature search elicited a total of 666 references; 580 were excluded and 20 articles met the inclusion criteria for the final analysis. Results. More studies supported the Pneumonia Severity Index (PSI) as a superior predictor of NHAP severity. Fewer studies suggested CURB-65 and SOAR (especially for the need of ICU care) as useful predictors for NHAP mortality. There is weak evidence for biomarkers like C-reactive protein and copeptin as prognostic tools. Conclusion. The evidence supports the use of PSI as the best available indicator while CURB-65 may be an alternative prognostic indicator for NHAP mortality. Overall, due to the paucity of information, biomarkers may not be as effective in this role. Larger prospective studies are needed to establish the most effective predictor(s) or combination scheme to help clinicians in decision-making related to NHAP mortality.

Inhaled corticosteroids and systemic inflammatory response in community-acquired pneumonia: a prospective clinical study

BACKGROUND AND OBJECTIVE

The previous use of inhaled corticosteroids (ICS) may reduce the inflammatory response and mortality in patients with community-acquired pneumonia (CAP).

METHODS

We measured serum levels of several inflammatory biomarkers, as well as mortality at various time-points, in 663 consecutive patients hospitalized for CAP; 128 (19%) were receiving chronic outpatient treatment with ICS. Patients on previous oral corticosteroids were excluded from the analysis.

RESULTS

On admission, patients treated with ICS were older; had been diagnosed with chronic obstructive pulmonary disease (COPD), asthma and pneumonia in the previous year more often; and had higher CAP severity risk classes and lower tumour necrosis factor (TNF)-alpha (P < 0.001) and interleukin (IL)-6 (P = 0.015) serum levels. After adjusting for potential confounders, this association persisted for TNF-alpha (P < 0.001), but not for IL-6. Mortality at 30 and 90 days tended to be lower in patients treated with ICS (P = 0.062 and 0.050, respectively), but mortality was similar after 1 year in both groups (16, 13% vs 81, 15% for patients treated and not treated with ICS, respectively). Hospital readmission rate after 1 year was higher in patients treated with ICS (49, 38% vs 109, 20%, P < 0.001). The association of ICS treatment with a previous diagnosis of pneumonia, lower levels of TNF-alpha and IL-6 on admission and higher readmission rates during follow up persisted in the subpopulation of 210 patients with COPD.

CONCLUSIONS

Previous use of ICS in patients hospitalized for CAP is associated with a reduced systemic inflammatory response without any impact on long-term mortality.

Intrapulmonary G-CSF rescues neutrophil recruitment to the lung and neutrophil release to blood in Gram-negative bacterial infection in MCP-1-/- mice

We previously demonstrated that MCP-1 is important for E. coli-induced neutrophil migration to the lungs. However, E. coli neither disseminates nor induces death in mice. Furthermore, the cell types and the host defense mechanisms that contribute to MCP-1-dependent neutrophil trafficking have not been defined. In this study, we sought to explore the cell types and the mechanisms associated with Klebsiella pneumoniae-mediated MCP-1-dependent neutrophil influx. MCP-1(-/-) mice are more susceptible to pulmonary K. pneumoniae infection and show higher bacterial burden in the lungs and dissemination. MCP-1(-/-) mice also display attenuated neutrophil influx, cytokine/chemokine production, and activation of NF-κB and MAPKs following intratracheal K. pneumoniae infection. rMCP-1 treatment in MCP-1(-/-) mice following K. pneumoniae infection rescued impairment in survival, bacterial clearance, and neutrophil accumulation in the lung. Neutrophil numbers in the blood of MCP-1(-/-) mice were associated with G-CSF concentrations in bronchoalveolar lavage fluid and blood. Bone marrow or resident cell-derived MCP-1 contributed to bacterial clearance, neutrophil accumulation, and cytokine/chemokine production in the lungs following infection. Furthermore, exogenous MCP-1 dose dependently increased neutrophil counts and G-CSF concentrations in the blood. Intriguingly, administration of intratracheal rG-CSF to MCP-1(-/-) mice after K. pneumoniae infection rescued survival, bacterial clearance and dissemination, and neutrophil influx in MCP-1(-/-) mice. Collectively, these novel findings unveil an unrecognized role of MCP-1 in neutrophil-mediated host immunity during K. pneumoniae pneumonia and illustrate that G-CSF could be used to rescue impairment in host immunity in individuals with absent or malfunctional MCP-1.

Infectious complications in patients with multiple myeloma treated with new drug combinations containing thalidomide

The literature provides scant data concerning infectious complications and their effect on the outcome of patients with multiple myeloma (MM) treated with new drug combinations. Despite no substantial myelotoxic effect, thalidomide increases the risk of severe infections in patients with MM. We studied 202 patients who received regimens containing thalidomide in order to assess the time, type, outcome, and factors affecting development of severe infections, role of antibiotic prophylaxis, and effect of severe infections on final outcome. Thirty-eight patients (19%) developed a severe infection early during induction therapy and most infections were pneumonia. Only one patient died due to septic shock during neutropenia. No significant differences were reported in terms of progression-free survival (PFS) and overall survival (OS) between patients developing a severe infection and those who did not. Multivariate analysis determined a monoclonal component >3 g/dL and platelets <130 ,000/μL as factors associated with increased risk of severe infection. Primary antibiotic prophylaxis significantly decreased the probability of severe infection only in patients having both the above risk factors. Patients with MM receiving thalidomide combinations with high tumor burden are at high risk of developing severe infections and require primary antibiotic prophylaxis, whereas in other patients it is questionable. However, patient final outcome was not affected by infection development.

Treatment failure in community-acquired pneumonia

Treatment failure (TF) is defined as a clinical condition with inadequate response to antimicrobial therapy. Clinical response should be evaluated within the first 72 h of treatment, whereas infiltrate images may take up to 6 weeks to resolve. Early failure is considered when ventilatory support and/or septic shock appear within the first 72 h. The incidence of treatment failure in community-acquired pneumonia is 10 to 15%, and the mortality is increased nearly fivefold. Resistant and unusual microorganisms and noninfectious causes are responsible for TF. Risk factors are related to the initial severity of the disease, the presence of comorbidity, the microorganism involved, and the antimicrobial treatment implemented. Characteristics of patients and factors related to inflammatory response have been associated with delayed resolution and poor prognosis. The diagnostic approach to TF depends on the degree of clinical impact, host factors, and the possible cause. Initial reevaluation should include a confirmation of the diagnosis of pneumonia, noninvasive microbiological samples, and new radiographic studies. A conservative approach of clinical monitoring and serial radiographs may be recommended in elderly patients with comorbid conditions that justify a delayed response. Invasive studies with bronchoscopy to obtain protected brush specimen and BAL are indicated in the presence of clinical deterioration or failure to stabilize. BAL processing should include the study of cell patterns to rule out other noninfectious diseases and complete microbiological studies. The diagnostic yield of imaging procedures with noninvasive and invasive samples is up to 70%. After obtaining microbiological samples, an empirical change in antibiotic therapy is required to cover a wider microbial spectrum.

Conditional expression of interferon-γ to enhance host responses to pulmonary bacterial infection

Strategies to augment host defense against pulmonary infection run the risk of inducing excess pulmonary inflammation and tissue injury. To address this problem, we investigated conditional expression in lung tissue of the murine interferon-gamma (IFN-gamma) transgene. A recombinant adenoviral vector (AdTetIFN) was constructed by placing a murine IFN-gamma cDNA downstream of a tetracycline (Tet)-responsive promoter, inserted into a replication-defective adenoviral vector. Co-infection of target cells with AdTetIFN and a second vector encoding a reverse tetracycline controlled transactivator allowed doxycycline (Dox)-regulated IFN-gamma production. We then administered 10(8) plaque-forming units (PFU) of AdTetIFN to mice by intratracheal injection. When the mice were provided with Dox in drinking water (0.5mg/ml in 5% sucrose), there was significant release of IFN-gamma in lavage fluid by ELISA in comparison to mice on water/sucrose alone (399+/-74 pg/ml vs undetectable, p<0.01). IFN-gamma in lavage fluid was associated with upregulation of Class II Major histocompatibility complex markers on alveolar macrophages by flow cytometry, suggesting macrophage activation. We then injected AdTetIFN into mice three days prior to challenge with 10(4) CFU Klebsiella pneumoniae. Test mice were maintained on water+Dox and control mice on water+sucrose. Bacterial burden was assayed in lung tissue at serial intervals. At 24h after challenge, mice on doxycycline had significantly lower infection burden in comparison to mice on water/sucrose (0.77+/-0.05 colony forming units/lung for 10(8) PFU AdTetIFN plus Dox compared to 1.4+/-0.11 colony-forming units/lung for AdTetIFN without Dox, p<0.05). Survival of the vector treated mice given doxycycline in drinking water was also enhanced. Microscopic examination of lavaged cells showed a significant increase in pulmonary neutrophils in the AdTetIFN+Dox mice in comparison to AdTetIFN+sucrose mice (16+/-1.0 x 10(5) vs 10+0.8 cells/lung, p<0.05). We conclude that local release of IFN-gamma can be selectively activated to enhance neutrophil recruitment and host resistance to bacterial pneumonia.

Dual function of the long pentraxin PTX3 in resistance against pulmonary infection with Klebsiella pneumoniae in transgenic mice

The long pentraxin PTX3 is expressed during acute inflammation and appears to control nitric oxide (NO) and tumor necrosis factor (TNF)-alpha production. In the present study, the physiological function of PTX3 was investigated in a model of pulmonary infection caused by the Gram-negative bacterium Klebsiella pneumoniae. Transgenic mice expressing multiple copies of PTX3 under the control of its own promoter were used to assess lethality rates, bacterial counts and inflammatory indices following pulmonary infection of mice. Expression of PTX3 is enhanced during pulmonary infection in wild-type mice. In transgenic mice given a high inoculum, overt PTX3 expression was associated with faster lethality. Faster lethality correlated with enhanced nitrate in plasma, an inability of neutrophils to migrate to lung tissue and greater dissemination of bacteria to blood at 20h after infection. In contrast, transgenic PTX3 expression conferred protection to mice given lower pulmonary inocula. In the latter experiments, there was enhanced TNF-alpha production, greater neutrophil influx and phagocytosis of bacteria by migrated neutrophils. By controlling the production of TNF-alpha and NO, and depending on the intensity of the inflammatory response induced by a given inoculum, the expression of PTX3 may favor or disfavor the influx of neutrophils and the ability of the murine host to deal with pulmonary infection with K. pneumoniae. These experiments highlight the delicate balance that exists among the various mediators that control the inflammatory response and suggest that PTX3 is an essential part of the ability of a host to deal with bacterial infection.

Noncapsulated Klebsiella pneumoniae bearing mannose-containing O antigens is rapidly eradicated from mouse lung and triggers cytokine production by macrophages following opsonization with surfactant protein D

To better understand the relationship between the surface polysaccharides of pulmonary pathogens and components of the lung innate immune system, we employed selected serotypes of Klebsiella pneumoniae expressing distinct capsular polysaccharides and/or O antigen in a murine model of K. pneumoniae infection. In addition, we examined the effect of surfactant protein D (SP-D) on the cytokine response of human monocyte-derived macrophages to these serotypes in vitro. Noncapsulated mannose-containing O3 serotypes (K50/n and K55/n), which react efficiently with SP-D in vitro, triggered high levels of interleukin-1beta (IL-1beta) and IL-6 production. In vivo, they were more efficiently cleared from the lungs of mice but not from macrophage-depleted mice. They also were more efficiently internalized by alveolar macrophages in vivo. In contrast, galactose-containing O1 serotypes (K2/n and K21a/n), which interact poorly with SP-D, exhibited significantly lower cytokine production and less efficient pulmonary clearance and were ineffectively internalized by alveolar macrophages. These findings are consistent with in vitro results showing that production of IL-1beta and IL-6 mRNA and IL-6 protein by human macrophages exposed to mannose-bearing Klebsiella O serotypes is significantly increased by SP-D. Thus, survival of inhaled bacteria in the lung depends partially on the lipopolysaccharide structure of the bacteria and their interactions with innate immunity components. We speculate that an imbalance of host SP-D and therefore cytokine levels may result in high susceptibility of the host to the pathogen.

Differential induction of human beta-defensin expression by periodontal commensals and pathogens in periodontal pocket epithelial cells

BACKGROUND

To investigate the possible role of beta-defensins in gingival health and periodontal disease, we examined the effect of several stimuli on the expression of interleukin-8 (IL-8), human beta-defensin-1, -2, -3, and -4 (hBD) in primary human diseased gingival epithelial (HGE) cell cultures from periodontitis patients by quantitative TaqMan reverse transcription polymerase chain reaction (RT-PCR).

METHODS

Several strains of the periodontopathogens Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were added to the cells, as well as the oral commensal bacteria Fusobacterium nucleatum and Escherichia coli. The induction by the proinflammatory stimuli phorbol 12-myristate 13-acetate (PMA) and tumor necrosis factor-alpha (TNF-alpha) was also tested.

RESULTS

In addition to the published observations (PMA induces hBD-2 and -4; TNF-alpha induces hBD-2 and -3), it was found that PMA can upregulate hBD-1 and hBD-3, whereas TNF-alpha can induce hBD-4. The commensal bacteria were significant inducers of hBD-2, hBD-3, and IL-8. The pathogen P. gingivalis induced hBD-1 and hBD-3 at different time points than the commensals, but no induction of IL-8 and hBD-2 could be observed. These data fit with the chemokine paralysis theory. A correlation was found between the pathogenicity of different serotypes of A. actinomycetemcomitans and the induction profiles of defensins and IL-8.

CONCLUSION

The results suggest that a correlation can be found in diseased oral epithelium between the defensin profiles that are induced and the pathogenicity of the oral bacterial strains.

Inflammation--a new therapeutic target in pneumonia

Inflammation is a hallmark of pneumonia. Therefore, managing inflammation is an attractive adjunct to targeted antibiotic therapy, mainly in severe pneumonia. Recent investigations indicate that glucocorticoids given in physiological doses (from 10-fold to 100-fold less than doses administered in the past) could be of benefit. We could also manage inflammation by administering or influencing cytokines. A major concern is that drugs designed to target a single cytokine or receptor could prove ineffective due to the redundancy of signaling pathways involved. This may require selection of drugs with broad activity or the targeting of molecules common to inflammatory signaling pathways. Drugs affecting multiple molecules or key inflammatory pathway intermediates could be more effective, but their use will need to be weighed against the risk of impairing innate immunity. Indirect approaches to manage inflammation, such as neutralizing cytotoxic substances in the lung (e.g., inhibiting, neutralizing and eliminating endotoxin), could be used in combination with other approaches. Ideally, potential treatment of life-threatening bacterial pneumonia will combine immunoadjuvant and conventional antibiotic therapy, although intense clinical research with immunotherapy has not yet yielded a successful treatment adjunct. We believe that compounds capable of stimulating early host defense and microbial clearance, but not the later phases of inflammatory tissue injury associated with sepsis, may be advantageous.

Ceftriaxone pharmacokinetics in interleukin-10-treated murine pneumococcal pneumonia

OBJECTIVES

Anti-inflammatory therapy with interleukin-10 (IL-10) was previously reported to reduce pulmonary inflammation and to prevent septicaemia in murine pneumococcal pneumonia treated with ceftriaxone. In the present report, we investigated the influence of pulmonary infection and IL-10 administration on the pharmacokinetics of ceftriaxone.

METHODS

CD1 mice were infected with 10(7) cfu of Streptococcus pneumoniae. Treatments (intraperitoneal) with IL-10 (1 microg per mouse), ceftriaxone (20 mg/kg) or the combination of IL-10 + ceftriaxone were initiated 18 h after infection. Groups of mice were sacrificed at several time points from 5 min to 24 h after initiation of therapy. Ceftriaxone was quantified in blood and lungs using a microbiological assay. Additional groups of mice received a second dose of IL-10 at 36 h post-infection. Survival rates were recorded over 14 days.

RESULTS

The clearance of ceftriaxone was significantly reduced in infected mice compared with that in non-infected animals (P < 0.01), whereas AUC, mean residence time, t(1/2) and AUC(lung)/AUC(serum) were significantly enhanced (P < 0.01, 0.01, 0.05, 0.05). Co-administration of IL-10 with ceftriaxone in infected animals further retained ceftriaxone in the bloodstream and reduced its volume of distribution at steady state and the ratio of AUC(lung)/AUC(serum). IL-10 alone did not modify significantly the pharmacokinetics of ceftriaxone in blood and lungs of non-infected animals.

CONCLUSIONS

The results suggest that pulmonary infection, and therapy with IL-10, both affect the pharmacokinetics of ceftriaxone. Indeed, administration of IL-10 + ceftriaxone improved the survival rate of mice (P < 0.001 compared with therapy with ceftriaxone alone). IL-10 should be considered as an adjunctive therapy to antibiotics against severe infections.

Modulation of cytokine-induced production of IL-8 in vitro by interferons and glucocorticosteroids

Interleukin-8 (IL-8) has been implicated in the pathogenesis of inflammation and cancer. Intracellular levels of cytokine-induced IL-8 in human umbilical vein endothelial cells (HUVEC) were modulated using interferons and steroids to further elucidate their mechanism. Basal and cytokine-induced production of IL-8 was studied using a novel ELISA application, flow cytometry, and RT-PCR. The intracellular amount of IL-8 increased after 6-h stimulation with TNF-alpha (30%) or IL-1beta (55%) which was doubled when Golgi transport was disrupted using monensin. IFN-gamma decreased the intracellular amount of IL-8 by 60% in both unstimulated and TNF-alpha-stimulated cells, but only when secretion was blocked using monensin. Dexamethasone inhibited the TNF-alpha-induced production by 33%, but had no effect in unstimulated cells. Our study indicated that both, dexamethasone and IFN inhibit TNF-alpha-induced upregulation of IL-8 at the mRNA level. It could be speculated that they inhibit IL-8 production by affecting different gene regulatory mechanisms.

[Guidelines for the management of community pneumonia in adult who needs hospitalization]

Community acquired pneumonia is still an important health problem. In Spain the year incidence is 162 cases per 100,000 inhabitants with 53,000 hospital admission costing 115 millions of euros per year. In the last years there have been significant advances in the knowledge of: aetiology, diagnostic tools, treatment alternatives and antibiotic resistance. The Spanish Societies of Intensive and Critical Care (SEMICYUC), Infectious Diseases and Clinical Microbiology (SEIMC) and Pulmonology and Thoracic Surgery (SEPAR) have produced these evidence-based Guidelines for the management of community acquired pneumonia in Adults. The main objective is to help physicians to make decisions about this disease. The different points that have been developed are: aetiology, diagnosis, treatment and prevention.

Is there a place for granulocyte colony-stimulating factor in non-neutropenic critically ill patients?

Immunoparalysis, characterised by impairments in neutrophil and monocyte/macrophage function, is common in critically ill patients. The theoretical ability of granulocyte colony-stimulating factor (G-CSF) to improve the functions of both neutrophils and monocytes/macrophages provides a rationale for G-CSF therapy in non-neutropenic critically ill patients with infection or a high risk of nosocomial infection. The expression of the receptors that mediate G-CSF effects in neutrophils and monocytes/macrophages is regulated by bacterial products, cytokines and endogenous G-CSF levels, accounting for the variables effects of G-CSF on the neutrophil functions of critically ill patients. This variability should be taken into account when designing studies on the use of G-CSF in ICU-patients. Studies are still needed to identify the subset of patients who may benefit from G-CSF therapy.

Novel approaches to the treatment of pneumonia

As the prevalence of resistance to multiple antibiotics increases it is progressively more difficult to treat pneumonia in hospitalized patients. Therefore, anti-infectious agents that have new modes of action are needed urgently. Recent advances in DNA sequencing technology make it possible to elucidate the sequences of the entire genomes of pathogenic bacteria. This allows many novel, non-traditional targets for therapeutic intervention to be identified, such as those involved in disease pathogenesis, and in adaptation and growth at sites of infection. In the past few years, inhibitors of new bacterial targets have been developed, including inhibitors of genes that are required for either virulence or pathogenesis. The challenge is to optimize and develop these agents to provide novel approaches to the treatment of pneumonia in hospitalized patients.

Cytokines in patients with lung cancer

Lung cancer is one of the most common malignant diseases and is amongst the leading causes of death. Cell-mediated immune response and cytokines could play an important role in antitumour immunity. The aim of the study was to evaluate the cytokines', tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and IL-6, releasing capacity in patients with lung carcinoma and benign lung disease. A group of 41 patients were tested for the production of TNF-alpha, IL-1beta and IL-6 in bronchoalveolar lavage (BAL) and blood. The levels of cytokines in the lung cancer patients were: (1) in BAL - IL-6, 173 +/- 85 pg/ml; TNF-alpha, 170 +/- 116 pg/ml; and IL-1beta, 473 +/- 440 pg/ml; (2) in the blood - IL-6, 197 +/- 53 pg/ml; TNF-alpha, 311 +/- 202 pg/ml; and IL-1beta, 915 +/- 239 pg/ml. Alveolar macrophages of the patients with a lung cancer secreted significantly more cytokines, IL-6 (P = 0.0004) and IL-1beta (P = 0.0047), than alveolar macrophages of the patients with a nonmalignant lung cancer. However, significantly lower levels of cytokine production by the BAL cells were found in patients with small cell lung cancer. This production decreased further in phase IV of nonsmall cell lung cancer.

Carvedilol modulates in-vitro granulocyte-macrophage colony-stimulating factor-induced interleukin-10 production in U937 cells and human monocytes

Both granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-10 (IL-10) are important mediators regulating inflammatory responses. Inflammatory processes have an important role in atherogenesis. In this paper, the effects of carvedilol on GM-CSF-induced IL-10 production were examined on human monocytic cell line, U937, and purified human monocytes. First, we showed that one-time carvedilol pretreatment at concentrations 0.3-10 microM dose-dependently inhibited GM-CSF-induced IL-10 production in U937 cells. In addition, we found carvedilol to be non-cytotoxic at concentrations equal to or less than 10 microM. However, at concentrations higher than 10 microM, carvedilol induced programmed cell death in U937 cells. The inhibition of GM-CSF-induced IL-10 production by carvedilol was also observed at the expression of mRNA. Furthermore, the inhibition of IL-10 production was demonstrated in GM-CSF-activated purified human peripheral blood monocytes. Finally, long-term carvedilol pretreatment of U937 cells up to 2 months at concentrations of 1.0 microM mildly enhanced the IL-10 production. Our observations that carvedilol modulated GM-CSF-induced IL-10 production may have some implication in understanding the broad-spectrum effects of carvedilol in regulating inflammatory reactions.

How to leverage an endogenous immune defense mechanism: the example of granulocyte colony-stimulating factor

Our understanding of host defense has exploded during the past two decades. It is temping to take advantage of this knowledge by considering the modulation and control of these mechanisms as therapeutic options. In intensive care medicine, the aim is usually to block an overwhelming inflammatory response, which represents the "bad" side of the double-edged sword of host defense. The obvious danger of such treatment strategies is that impairing the inflammatory reaction means impairing host defense in patients exposed to infectious agents. The alternative approach, i.e., strengthening or supplementing favorable host defense mechanism, has so far been little explored clinically. Granulocyte colony-stimulating factor, the granulocyte colony-stimulating factor, combines the unique properties of an anti-infectious and an anti-inflammatory factor. This attractive profile has led us to various approaches to exploit these immunomodulatory activities. In a recently terminated, placebo-controlled, randomized study, we investigated if prophylactic treatment with rh granulocyte colony-stimulating factor (Filgrastim), at the time a risk can be anticipated such as before an operation, may offer protection from immunoinflammatory dyshomeostasis and thus lower the incidence of postoperative sepsis. Perioperative rh granulocyte colony-stimulating factor administration, compared with placebo treatment, resulted in the prevention of postoperative monocyte deactivation, conservation of an adequate Th1/Th2 ratio, as well as a considerable alleviation of the acute phase response. In parallel, there was a clear tendency toward lowering the rate of postoperative septic complications under the administration of Filgrastim.

Interleukin-17 stimulates the expression of interleukin-8, growth-related oncogene-alpha, and granulocyte-colony-stimulating factor by human airway epithelial cells

Interleukin (IL)-17 is a recently discovered cytokine, which is proposed to play a role in neutrophilic airway inflammation via the release of proinflammatory cytokines and chemokines. To evaluate the role of IL-17 in inflammatory protein production from the airway epithelium, we have analyzed the effects of IL-17 on primary human bronchial epithelial cells (HBECs). Using gene arrays, changes in gene expression in response to IL-17 stimulation were investigated and only IL-8, growth-related oncogene (Gro)alpha, and granulocyte colony-stimulating factor (G-CSF) were found to be upregulated. Secretion of IL-8, Groalpha, and G-CSF in response to IL-17 was measured in HBEC cell culture supernatants by enzyme-linked immunosorbent assay. Upregulation of Groalpha, IL-8, and G-CSF was observed to be 8-, 5-, and 8-fold, respectively, after 48 h stimulation with IL-17. When tested at equivalent concentrations, IL-17 was found to be 2- to 3-fold more potent than tumor necrosis factor (TNF)-alpha in stimulating release of Groalpha and G-CSF from HBECs. In addition, IL-17 was found to synergistically enhance TNF-alpha-induced production of IL-8, Groalpha, and G-CSF. It is proposed that IL-17 may play an important role in neutrophil recruitment via stimulating the release of IL-8, Groalpha, and G-CSF from airway epithelial cells.

Aerobic Gram-negative Bacillary Pneumonia

Gram-negative bacilli (GNB) are a common cause of severe hospital-acquired pneumonia. Due to changes in the health care environment and selective antimicrobial pressure, these bacteria also are becoming a more common cause of pneumonia in venues outside of the traditional hospital setting and are increasingly resistant to antimicrobial agents. Risk factors for acquisition of GNB allow the clinician to efficiently identify patients who are likely to have pneumonia due to these pathogens. Available diagnostic techniques have a limited capacity to accurately detect GNB pulmonary infection. Yet, a pathogen specific diagnosis and knowledge of local resistance patterns are quintessential elements in formulating an effective treatment plan. This article reviews the epidemiologic characteristics, pathogenesis, and current management issues of GNB pneumonia.

Immunologic aspects of tropical lung disease

Respiratory tract infections are a major cause of morbidity and mortality in adults and children worldwide. Because of its anatomical features, which allow gaseous exchange, the respiratory tract is constantly exposed to the outer environment and to the systemic and pulmonary circulation, which may allow infectious microbes, toxins, allergens, dust, and other antigens to enter the lung. The human host is a perpetual battleground between the body's immune system and invading antigens, whether they are microorganisms, chemicals, or cancer cells. Although a vast amount of literature is accumulating on the subject of immune responses to pathogens, the mechanisms underlying specific immunity to many organisms remain unknown. Paradoxically, while the immune response has evolved to confer protection against invading antigens, much human pathology arises when the immune responses are evoked.

Requirement of interleukin 17 receptor signaling for lung CXC chemokine and granulocyte colony-stimulating factor expression, neutrophil recruitment, and host defense

Bacterial pneumonia is an increasing complication of HIV infection and inversely correlates with the CD4(+) lymphocyte count. Interleukin (IL)-17 is a cytokine produced principally by CD4(+) T cells, which induces granulopoiesis via granulocyte colony-stimulating factor (G-CSF) production and induces CXC chemokines. We hypothesized that IL-17 receptor (IL-17R) signaling is critical for G-CSF and CXC chemokine production and lung host defenses. To test this, we used a model of Klebsiella pneumoniae lung infection in mice genetically deficient in IL-17R or in mice overexpressing a soluble IL-17R. IL-17R-deficient mice were exquisitely sensitive to intranasal K. pneumoniae with 100% mortality after 48 h compared with only 40% mortality in controls. IL-17R knockout (KO) mice displayed a significant delay in neutrophil recruitment into the alveolar space, and had greater dissemination of K. pneumoniae compared with control mice. This defect was associated with a significant reduction in steady-state levels of G-CSF and macrophage inflammatory protein (MIP)-2 mRNA and protein in the lung in response to the K. pneumoniae challenge in IL-17R KO mice. Thus, IL-17R signaling is critical for optimal production of G-CSF and MIP-2 and local control of pulmonary K. pneumoniae infection. These data support impaired IL-17R signaling as a potential mechanism by which deficiency of CD4 lymphocytes predisposes to bacterial pneumonia.