Defective innate antibacterial host responses during murine Klebsiella pneumoniae bacteremia: tumor necrosis factor (TNF) receptor 1 deficiency versus therapy with anti-TNF-alpha

Low-frequency ultrasound alleviates pulmonary inflammation induced by Klebsiella pneumoniae in mice by inhibiting the TNFR1/NF-κB pathway

BACKGROUND

Therapeutic ultrasound has been found to promote tissue healing and reduce inflammation in non-infectious diseases, but its efficacy in infectious inflammation remains unclear. Here, we employ the mice pneumonia model to explore the anti-inflammatory effects of low-frequency ultrasound (LFU) and elucidate its potential molecular mechanisms.

METHODS

Pneumonia in mice was induced by intratracheal instillation of 100 μL of a 4.5 × 108 CFU/mL Klebsiella pneumoniae (Kp) bacterial suspension. A single LFU treatment (29.36 kHz, 270 mW/cm2, 10 min) was applied to the chest of mice at 6 or 48 h after infection. Biological samples were collected for gene, protein, and cellular experiments.

RESULTS

LFU demonstrated good anti-inflammatory effects in mice during the recovery phase of Kp infection (48 h after infection). Although LFU alone had no bactericidal effects, it slightly reduced the pathological score of lung injury and significantly decreased the infiltration of CD45+ leukocytes. Additionally, the protein levels of TNF-α, GM-CSF and COX-2 in the bronchoalveolar lavage fluid were significantly reduced. Bulk RNA-sequencing results showed that the TNF receptor (TNFR)/NF-κB pathway was up-regulated after Kp infection, which was suppressed after LFU treatment. Western blot and immunofluorescence revealed LFU significantly reduced the protein levels of TNFR1, p-p65, and nuclear p65. The anti-inflammatory effect of LFU was comparable to a 20 mg/kg NF-κB inhibitor and superior to a 15 mg/kg TNFR antagonist.

CONCLUSION

LFU exerts anti-inflammatory effects by inhibiting the TNFR1/NF-κB pathway during the recovery period of Kp infection, reducing inflammatory transcription and thereby decreasing the release of inflammatory factors.

CRISPR/Cas9-mediated knockout of tnf-α1 in zebrafish reduces disease resistance after Edwardsiella piscicida bacterial infection

Tumor necrosis factor (TNF) is an important cytokine involved in immune responses to bacterial infections in vertebrates, including fish. Although Tnf-α is a well-studied cytokine, there are contradictory findings about Tnf-α function following bacterial infection. In this study, we analyzed the expression and function of the Tnf-α-type I isoform (Tnf-α1) in zebrafish by knockout experiments using the CRISPR/Cas9 gene-editing tool. The open reading frame of tnf-α1 encodes a 25.82 kDa protein with 234 amino acids (aa). The expression of tnf-α1 in the early stages of zebrafish was observed from the 2-cell stage. Adult zebrafish spleens showed the highest expression of tnf-α1. To evaluate the function of Tnf-α1, an 8 bp deletion in the target region, resulting in a short truncated protein of 55 aa, was used to create the tnf-α1 knockout mutant. The pattern of downstream gene expression in 7-day larvae in wild-type (WT) and tnf-α1 knockout fish was examined. We also verified the fish mortality rate after Edwardsiella piscicida challenge and found that it was much higher in tnf-α1 knockout fish than in WT fish. Additionally, downstream gene expression analyses after E. piscicida exposure revealed a distinct expression pattern in tnf-α1 knockout fish compared to that in WT fish. Overall, our study using tnf-α1 deletion in zebrafish confirmed that Tnf-α1 is critical for immune regulation during bacterial infection.

Oral Administration of Lacticaseibacillus rhamnosus CRL1505 Modulates Lung Innate Immune Response against Klebsiella pneumoniae ST25

Orally administered Lacticaseibacillus rhamnosus CRL1505 enhances respiratory immunity, providing protection against respiratory viruses and Streptococcus pneumoniae. However, the capacity of the CRL1505 strain to improve respiratory immunity against Gram-negative bacterial infections has not been evaluated before. The aim of this work was to evaluate whether the Lcb. rhamnosus CRL1505 was able to beneficially regulate the respiratory innate immune response and enhance the resistance to hypermucoviscous KPC-2-producing Klebsiella pneumoniae of the sequence type 25 (ST25). BALB/c mice were treated with the CRL1505 strain via the oral route and then nasally challenged with K. pneumoniae ST25 strains LABACER 01 or LABACER 27. Bacterial cell counts, lung injuries and the respiratory and systemic innate immune responses were evaluated after the bacterial infection. The results showed that K. pneumoniae ST25 strains increased the levels of TNF-α, IL-1β, IL-6, IFN-γ, IL-17, KC and MPC-1 in the respiratory tract and blood, as well as the numbers of BAL neutrophils and macrophages. Mice treated with Lcb. rhamnosus CRL1505 had significantly lower K. pneumoniae counts in their lungs, as well as reduced levels of inflammatory cells, cytokines and chemokines in the respiratory tract and blood when compared to infected controls. Furthermore, higher levels of the regulatory cytokines IL-10 and IL-27 were found in the respiratory tract and blood of CRL1505-treated mice than controls. These results suggest that the ability of Lcb. rhamnosus CRL1505 to help with the control of detrimental inflammation in lungs during K. pneumoniae infection would be a key feature to improve the resistance to this pathogen. Although further mechanistic studies are necessary, Lcb. rhamnosus CRL1505 can be proposed as a candidate to improve patients' protection against hypermucoviscous KPC-2-producing strains belonging to the ST25, which is endemic in the hospitals of our region.

Host Immune Response to Clinical Hypervirulent Klebsiella pneumoniae Pulmonary Infections via Transcriptome Analysis

Klebsiella pneumoniae (K. pneumoniae), especially those with hypervirulence, is becoming a global concern and posing great threat to human health. Studies on individual immune cells or cytokines have partially revealed the function of the host immune defense against K. pneumoniae pulmonary infection. However, systematic immune response against K. pneumoniae has not been fully elucidated. Herein, we report a transcriptome analysis of the lungs from a mouse pneumonia model infected with a newly isolated K. pneumoniae clinical strain YBQ. Total RNA was isolated from the lungs of mice 48 hours post infection to assess transcriptional alteration of genes. Transcriptome data were analyzed with KEGG, GO, and ICEPOP. Results indicated that upregulated transcription level of numerous cytokines and chemokines was coordinated with remarkably activated ribosome and several critical immune signaling pathways, including IL-17 and TNF signaling pathways. Notably, transcription of cysteine cathepsin inhibitor (stfa1, stfa2, and stfa3) and potential cysteine-type endopeptidase inhibitor (cstdc4, cstdc5, and cstdc6) were upregulated. Results of ICEPOP showed neutrophils functions as the most essential cell type against K. pneumoniae infection. Critical gene alterations were further validated by rt-PCR. Our findings provided a global transcriptional perspective on the mechanisms of host defense against K. pneumoniae infection and revealed some unique responding genes.

Hypoxia-Inducible Factor-1α in Macrophages, but Not in Neutrophils, Is Important for Host Defense during Klebsiella pneumoniae-Induced Pneumosepsis

Hypoxia-inducible factor- (HIF-) 1α has been implicated in the ability of cells to adapt to alterations in oxygen levels. Bacterial stimuli can induce HIF1α in immune cells, including those of myeloid origin. We here determined the role of myeloid cell HIF1α in the host response during pneumonia and sepsis caused by the common human pathogen Klebsiella pneumoniae. To this end, we generated mice deficient for HIF1α in myeloid cells (LysM-cre × Hif1α^fl/fl) or neutrophils (Mrp8-cre × Hif1α^fl/fl) and infected these with Klebsiella pneumoniae via the airways. Myeloid, but not neutrophil, HIF1α-deficient mice had increased bacterial loads in the lungs and distant organs after infection as compared to control mice, pointing at a role for HIF1α in macrophages. Myeloid HIF1α-deficient mice did not show increased bacterial growth after intravenous infection, suggesting that their phenotype during pneumonia was mediated by lung macrophages. Alveolar and lung interstitial macrophages from LysM-cre × Hif1α^fl/fl mice produced lower amounts of the immune enhancing cytokine tumor necrosis factor upon stimulation with Klebsiella, while their capacity to phagocytose or to produce reactive oxygen species was unaltered. Alveolar macrophages did not upregulate glycolysis in response to lipopolysaccharide, irrespective of HIF1α presence. These data suggest a role for HIF1α expressed in lung macrophages in protective innate immunity during pneumonia caused by a common bacterial pathogen.

Myeloid Liver Kinase B1 depletion is associated with a reduction in alveolar macrophage numbers and an impaired host defense during gram-negative pneumonia

BACKGROUND

Liver kinase B1 (LKB1) has been studied extensively as a tumor suppressor gene (Stk11) in the context of cancer. We hypothesized that myeloid LKB1 plays a role in innate immunity during pneumonia.

METHODS

Mice deficient for LKB1 in myeloid cells (LysM-cre x Stk11fl/fl ) or neutrophils (Mrp8-cre x Stk11fl/fl) were infected with Klebsiellapneumoniae via the airways. LysM-cre x Stk11fl/fl mice were also intranasally challenged with lipopolysaccharide (LPS).

RESULTS

Myeloid, but not neutrophil LKB1 deficient mice had increased bacterial loads in lungs from 6 to 40 hours after infection as compared to control mice, pointing at a role for LKB1 in macrophages. Myeloid LKB1 deficiency was associated with reduced cytokine release into the airways upon local LPS instillation. The number of classical (SiglecFhighCD11bneg) alveolar macrophages (AMs) was reduced by approximately 50% in the lungs of myeloid LKB1 deficient mice, which was not caused by increased cell death or reduced proliferation. Instead, myeloid LKB1 deficient mice had AMs with a 'non-classical' (SiglecFlowCD11bpos) phenotype. AMs did not upregulate glycolysis in response to LPS, irrespective of LKB1 presence.

CONCLUSION

Myeloid LKB1 is important for local host defense during Klebsiella pneumonia by maintaining adequate AM numbers in the lung.

Predicting Human Infection Risk: Do Rodent Host Resistance Models Add Value?

Use of genetically engineered rodents is often considered a valuable exercise to assess potential safety concerns associated with the inhibition of a target pathway. When there are potential immunomodulatory risks associated with the target, these genetically modified animals are often challenged with various pathogens in an acute setting to determine the risk to humans. However, the applicability of the results from infection models is seldom assessed when significant retrospective human data become available. Thus, the purpose of the current review is to compare the outcomes of infectious pathogen challenge in mice with genetic deficiencies in TNF-α, IL17, IL23, or Janus kinase pathways with infectious outcomes caused by inhibitors of these pathways in humans. In general, mouse infection challenge models had modest utility for hazard identification and were generally only able to predict overall trends in infection risk. These models did not demonstrate significant value in evaluating specific types of pathogens that are either prevalent (ie rhinoviruses) or of significant concern (ie herpes zoster). Similarly, outcomes in mouse models tended to overestimate the severity of infection risk in human patients. Thus, there is an emerging need for more human-relevant models that have better predictive value. Large meta-analyses of multiple clinical trials or post-marketing evaluations remains the gold-standard for characterizing the true infection risk to patients.

Klebsiella pneumoniae infection biology: living to counteract host defences

Klebsiella species cause a wide range of diseases including pneumonia, urinary tract infections (UTIs), bloodstream infections and sepsis. These infections are particularly a problem among neonates, elderly and immunocompromised individuals. Klebsiella is also responsible for a significant number of community-acquired infections. A defining feature of these infections is their morbidity and mortality, and the Klebsiella strains associated with them are considered hypervirulent. The increasing isolation of multidrug-resistant strains has significantly narrowed, or in some settings completely removed, the therapeutic options for the treatment of Klebsiella infections. Not surprisingly, this pathogen has then been singled out as an 'urgent threat to human health' by several organisations. This review summarises the tremendous progress that has been made to uncover the sophisticated immune evasion strategies of K. pneumoniae. The co-evolution of Klebsiella in response to the challenge of an activated immune has made Klebsiella a formidable pathogen exploiting stealth strategies and actively suppressing innate immune defences to overcome host responses to survive in the tissues. A better understanding of Klebsiella immune evasion strategies in the context of the host-pathogen interactions is pivotal to develop new therapeutics, which can be based on antagonising the anti-immune strategies of this pathogen.

Effect of spironolactone on the risks of mortality and hospitalization for heart failure in pre-dialysis advanced chronic kidney disease: A nationwide population-based study

BACKGROUND

Spironolactone has been shown to reduce cardiovascular death in patients with mild-to-moderate chronic kidney disease (CKD), but its risks and benefits in advanced CKD remain unsettled. We aimed to assess whether spironolactone reduces cardiovascular mortality and morbidity in pre-dialysis stage 5 CKD patients.

METHODS

Using Taiwan's National Health Insurance Research Database from January 2000 to June 2009, we enrolled 27,213 pre-dialysis stage 5 CKD adult patients, in whom 1363 patients were treated with spironolactone (user) and 25,850 were not (nonuser). Outcomes were all-cause mortality, hospitalization for heart failure (HHF) and major adverse cardiac event (MACE, the composite of acute myocardial infarction and ischemic stroke). Patients were followed up till December 31, 2009.

RESULTS

Over 85,758 person-years of follow-up, spironolactone users had higher incidence for all-cause mortality (24.7/100 person-years vs. 10.6/100 person-years), infection-related death (4.4/100 person-years vs. 1.7/100 person-years) and HHF (4.0/100 person-years vs. 1.4/100 person-years). Multivariable Cox hazards model showed that spironolactone users were associated with higher risks of all-cause mortality (adjusted hazard ratio [aHR] 1.35, 95% confidence interval [CI] 1.24-1.46), infection-related death (aHR 1.42, CI 1.16-1.73) and HHF (aHR 1.35, CI 1.08-1.67) as compared to nonusers. The risks for cardiovascular mortality, MACE and hyperkalemia-associated hospitalization were similar between two groups. After matching users and nonusers (1:3 ratio) by propensity scores, the results were consistent in matched cohort and across subgroups.

CONCLUSIONS

Spironolactone may be associated with higher risks for all-cause and infection-related mortality and HHF in pre-dialysis stage 5 CKD patients. Spironolactone should be used with caution in advanced CKD patients.

Innate Lymphocyte/Ly6C(hi) Monocyte Crosstalk Promotes Klebsiella Pneumoniae Clearance

Increasing antibiotic resistance among bacterial pathogens has rendered some infections untreatable with available antibiotics. Klebsiella pneumoniae, a bacterial pathogen that has acquired high-level antibiotic resistance, is a common cause of pulmonary infections. Optimal clearance of K. pneumoniae from the host lung requires TNF and IL-17A. Herein, we demonstrate that inflammatory monocytes are rapidly recruited to the lungs of K. pneumoniae-infected mice and produce TNF, which markedly increases the frequency of IL-17-producing innate lymphoid cells. While pulmonary clearance of K. pneumoniae is preserved in neutrophil-depleted mice, monocyte depletion or TNF deficiency impairs IL-17A-dependent resolution of pneumonia. Monocyte-mediated bacterial uptake and killing is enhanced by ILC production of IL-17A, indicating that innate lymphocytes engage in a positive-feedback loop with monocytes that promotes clearance of pneumonia. Innate immune defense against a highly antibiotic-resistant bacterial pathogen depends on crosstalk between inflammatory monocytes and innate lymphocytes that is mediated by TNF and IL-17A.

Distinct Contributions of Neutrophils and CCR2+ Monocytes to Pulmonary Clearance of Different Klebsiella pneumoniae Strains

Klebsiella pneumoniae is a common respiratory pathogen, with some strains having developed broad resistance to clinically available antibiotics. Humans can become infected with many different K. pneumoniae strains that vary in genetic background, antibiotic susceptibility, capsule composition, and mucoid phenotype. Genome comparisons have revealed differences between K. pneumoniae strains, but the impact of genomic variability on immune-mediated clearance of pneumonia remains unclear. Experimental studies of pneumonia in mice have used the rodent-adapted 43816 strain of K. pneumoniae and demonstrated that neutrophils are essential for optimal host defense. It remains unclear, however, whether CCR2(+) monocytes contribute to K. pneumoniae clearance from the lung. We selectively depleted neutrophils, CCR2(+) monocytes, or both from immunocompetent mice and determined susceptibility to infection by the 43816 strain and 4 newly isolated clinical K. pneumoniae strains. The clinical K. pneumoniae strains, including one carbapenem-resistant ST258 strain, are less virulent than 43816. Optimal clearance of each of the 5 strains required either neutrophils or CCR2(+) monocytes. Selective neutrophil depletion markedly worsened infection with K. pneumoniae strain 43816 and three clinical isolates but did not increase susceptibility of mice to infection with the carbapenem-resistant K. pneumoniae ST258 strain. Depletion of CCR2(+) monocytes delayed recovery from infection with each of the 5 K. pneumoniae strains, revealing a contribution of these cells to bacterial clearance from the lung. Our findings demonstrate strain-dependent variation in the contributions of neutrophils and CCR2(+) monocytes to clearance of K. pneumoniae pulmonary infection.

Sulforaphane epigenetically regulates innate immune responses of porcine monocyte-derived dendritic cells induced with lipopolysaccharide

Histone acetylation, regulated by histone deacetylases (HDACs) is a key epigenetic mechanism controlling gene expressions. Although dendritic cells (DCs) are playing pivotal roles in host immune responses, the effect of epigenetic modulation of DCs immune responses remains unknown. Sulforaphane (SFN) as a HDAC inhibitor has anti-inflammatory properties, which is used to investigate the epigenetic regulation of LPS-induced immune gene and HDAC family gene expressions in porcine monocyte-derived dendritic cells (moDCs). SFN was found to inhibit the lipopolysaccharide LPS induced HDAC6, HDAC10 and DNA methyltransferase (DNMT3a) gene expression, whereas up-regulated the expression of DNMT1 gene. Additionally, SFN was observed to inhibit the global HDAC activity, and suppressed moDCs differentiation from immature to mature DCs through down-regulating the CD40, CD80 and CD86 expression and led further to enhanced phagocytosis of moDCs. The SFN pre-treated of moDCs directly altered the LPS-induced TLR4 and MD2 gene expression and dynamically regulated the TLR4-induced activity of transcription factor NF-κB and TBP. SFN showed a protective role in LPS induced cell apoptosis through suppressing the IRF6 and TGF-ß1 production. SFN impaired the pro-inflammatory cytokine TNF-α and IL-1ß secretion into the cell culture supernatants that were induced in moDCs by LPS stimulation, whereas SFN increased the cellular-resident TNF-α accumulation. This study demonstrates that through the epigenetic mechanism the HDAC inhibitor SFN could modulate the LPS induced innate immune responses of porcine moDCs.

The dichotomy of inhibiting nuclear factor kappa-B in pneumonia

Activation of nuclear factor kappa-B (NF-κB) results in its translocation from the cytoplasm to the nucleus and binding to the promoters of a large number of genes, including those encoding proinflammatory cytokines and other mediators that can contribute to organ system dysfunction in severe infection. While inhibition of NF-κB activation has been proposed as a therapeutic approach in critical illness, several studies have indicated that such an approach may have deleterious effects in persistent infectious states, such as pneumonia. A new report from Devaney and colleagues shows that while inhibition of NF-κB may be useful in severe pneumonia associated with rapid progression to mortality, it leads to worsened pulmonary injury with increased bacterial numbers in the lungs in a model of prolonged pneumonia. Such data raise concerns about therapeutic approaches targeting NF-κB in critically ill patients with persistent infection.

Infections and biologic therapy in rheumatoid arthritis: our changing understanding of risk and prevention

Patients with rheumatoid arthritis are at higher risk for serious infections and death from infection than the general public. Prednisone and biologic agents increase this risk, although the risk associated with biologics can be mitigated when such agents act as prednisone-sparing therapies. Some of the important causes of infectious morbidity in this setting are preventable with screening (eg, tuberculosis) or vaccination (eg, herpes zoster).

The safety of etanercept for the treatment of plaque psoriasis

Effective treatment with etanercept results from a congregation of immunological signaling and modulating roles played by tumor necrosis factor-alpha (TNF-alpha), a pervasive member of the TNF super-family of cytokines participating in numerous immunologic and metabolic functions. Macrophages, lymphocytes and other cells produce TNF as part of the deregulated immune response resulting in psoriasis or other chronic inflammatory disorders. Tumor necrosis factor is also produced by macrophages and lymphocytes responding to foreign antigens as a primary response to potential infection. Interference with cytokine signaling by etanercept yields therapeutic response. At the same time, interference with cytokine signaling by etanercept exposes patients to potential adverse events. While the efficacy of etanercept for the treatment of psoriasis is evident, the risks of treatment continue to be defined. Of the potential serious adverse events, response to infection is the best characterized in terms of physiology, incidence, and management. Rare but serious events: activation of latent tuberculosis, multiple sclerosis, lymphoma, and others, have been observed but have questionable or yet to be defined association with therapeutic uses of etanercept. The safe use of etanercept for the treatment of psoriasis requires an appreciation of potential adverse events as well as screening and monitoring strategies designed to manage patient risk

Incidence and nature of infectious disease in patients treated with anti-TNF agents

Tumor necrosis factor alpha (TNF-alpha) inhibitors offer a targeted therapeutic strategy that contrasts with the nonspecific immunosuppressive agents traditionally used to treat most inflammatory diseases. These biologic agents have had a significant impact in ameliorating the signs and symptoms of inflammatory rheumatoid disease and improving patient function. From the onset of clinical trials, a central concern of cytokine blockade has been a potential increase in susceptibility to infections. Not surprisingly, a variety of infections have been reported in association with the use of TNF-alpha inhibitor agents. In particular, there is evidence suggesting an increased rate of granulomatous infections in patients treated with monoclonal TNF-alpha inhibitors. This review provides the incidence and nature of infections in patients treated with TNF-alpha inhibitor agents and reminds the clinician of the required vigilance in monitoring patients.

TNF receptor 1 and 2 contribute in different ways to resistance to Legionella pneumophila-induced mortality in mice

Legionella pneumophila is one of the most important pathogens which cause community-acquired pneumonia. Although TNF-alpha is considered to play an important role in response to bacteria, the role of the TNF-alpha receptor on L. pneumophila infection remains to be elucidated. To investigate this, we infected TNF receptor deficient mice with L. pneumophila. L. pneumophila was inoculated intranasally into TNF receptor (TNFR)-1-knock-out mice or TNFR2-knock-out mice. The mortality rate, histology of the lung, bacterial growth in the lung, and bronchoalveolar lavage (BAL) fluids were investigated. The bacterial growth of L. pneumophila in the macrophages was also studied. Almost all the mice survived after an intranasal inoculation of 1x10(6)CFU/head of L. pneumophila, but more than 90% mice were killed after inoculation of 1x10(8)CFU/head of L. pneumophila. In the case of TNFR1-knock-out mice and TNFR2-knock-out mice, a high mortality rate was observed after inoculation of 1x10(7)CFU/head of L. pneumophila in comparison to wild-type mice. The lung histology from both the TNFR1-knock-out mice documented severe lung injury at day 3 after inoculation. The clearance of L. pneumophila in the lung of the TNFR1-knock-out mice was slower than those from both the TNFR2-knock-out mice and the wild-type mice. Moreover, L. pneumophila growth in the peritoneal macrophages from the TNFR1-knock-out mice was observed. Interestingly, a lack of neutrophils accumulation in the BAL fluids and a dysregulation of cytokines (IFN-gamma, interleukin-12, and TNF-alpha) were observed in the TNFR1-knock-out mice. On the contrary, large accumulation of neutrophils in BAL fluids was observed in TNFR2-knock-out mice. These data suggested that a TNFR1 deficiency led to a compromise of the innate immunity against L. pneumophila, while a TNFR2 deficiency induced an excessive inflammatory response and resulted in death. The present study confirmed that TNFR1 and TNFR2 play a crucial, but different role in the control of L. pneumophila-induced mortality.

A role for tumor necrosis factor-alpha in experimental Bacillus cereus endophthalmitis pathogenesis

PURPOSE

To determine the contribution of tumor necrosis factor-alpha (TNFalpha) in the pathogenesis of experimental Bacillus cereus endophthalmitis.

METHODS

Experimental B. cereus endophthalmitis was induced in wild-type control (B6.129F1) and age-matched homozygous TNFalpha knockout mice (TNFalpha(-/-), B6.129S6-Tnf(tm1Gk1)/J). At various times after infection, eyes were analyzed by electroretinography and were harvested for quantitation of bacteria, myeloperoxidase, proinflammatory cytokines and chemokines, and histologic analysis.

RESULTS

B. cereus replicated more rapidly in the eyes of TNFalpha(-/-) mice than in the eyes of B6.129F1 mice. Retinal function decreased more rapidly in TNFalpha(-/-) mice than in B6.129F1 mice. Retinal layers were not as structurally intact at 6 and 12 hours after infection in TNFalpha(-/-) eyes as in B6.129F1 eyes. Histologic analysis suggested less polymorphonuclear leukocyte (PMN) infiltration into the vitreous of TNFalpha(-/-) mice than of B6.129F1 mice. B6.129F1 eyes also had greater myeloperoxidase concentrations than did eyes of TNFalpha(-/-) mice. In general, concentrations of proinflammatory cytokines and chemokines (IL-1beta, KC, IL-6, and MIP-1alpha) were greater in eyes of TNFalpha(-/-) mice than of B6.129F1 mice.

CONCLUSIONS

TNFalpha is important to intraocular pathogen containment by PMNs during experimental B. cereus endophthalmitis. In the absence of TNFalpha, fewer PMNs migrated into the eye, facilitating faster bacterial replication and retinal function loss. Although greater concentrations of proinflammatory cytokines were synthesized in the absence of TNFalpha, the resultant inflammation was diminished, and an equally devastating course of infection occurred.

Active hexose correlated compound activates immune function to decrease bacterial load in a murine model of intramuscular infection

BACKGROUND

Infection is a serious, costly, and common complication of surgery and constitutes the principal cause of late death in patients undergoing surgery. The objective of this study was to clarify the mechanisms by which active hexose correlated compound (AHCC) increases survival in a murine model of intramuscular infection.

METHODS

Food-deprived mice receiving either AHCC or excipient were infected with bacteria. Kinetics of bacterial load, white blood cell counts, cytokine levels, and antibody levels were compared between groups.

RESULTS

AHCC-treated mice had reduced bacterial load at day 5 and cleared bacteria entirely at day 6. Levels of interleukin-12, tumor necrosis factor-alpha, and interleukin-6 peaked earlier in this group (day 3) compared with controls (day 5). Increased percentages of peripheral lymphocytes and monocytes and decreased numbers of polymorphonuclear cells were detected in the AHCC group.

CONCLUSIONS

AHCC appears to induce an early activation of the immune response, leading to an effective clearance of bacteria and rapid recovery.

TNF receptor type I-dependent activation of innate responses to reduce intestinal damage-associated mortality

BACKGROUND & AIMS

Ligation of tumor necrosis factor (TNF) receptors (TNFRs) with TNF plays a critical role in the pathogenesis of human inflammatory bowel disease (IBD). However, it remains unclear which cell types activated through TNFR-associated signaling cascades are involved in the pathogenesis of colitis.

METHODS

Recombination activating gene-1 (RAG) knockout (KO) (no T or B cells)-based TNFR double and triple KO mice were generated. Bone marrow (BM) chimera mice in which BM-derived myeloid cells, but not colonic epithelial cells (CECs), express TNFRs were also generated. Colitis was induced by administration of dextran sodium sulfate (DSS) in distilled water. Murine lines and chimeras were assessed for disease severity, histopathology, apoptotic cell rate, epithelial proliferation, and bacterial invasion rate.

RESULTS

Following DSS administration, mice lacking both RAG and TNFR1 exhibited a high mortality (>80%) rate with an impaired CEC regeneration compared with RAG KO and RAG x TNFR2 double KO (DKO) mice. Transplantation of RAG KO-derived BM cells restored CEC regeneration and rescued the majority of recipient RAG x TNFR1 DKO mice from DSS-induced mortality. After BM transplantation, RAG x TNFR1 DKO mice exhibited an increased rate of apoptosis in the colonic lamina propria macrophages in association with the activation of caspases. In addition, BM reconstitution directly or indirectly enhanced the proliferation of CECs by activating mitogen-activated protein kinase and phosphoinositide-3 kinase/Akt pathways.

CONCLUSIONS

TNFR1-signaling cascade in colonic myeloid lineage cells contributes to the suppression of acute damage-associated mortality presumably by controlling CEC homeostasis.

Risk and prevention of tuberculosis and other serious opportunistic infections associated with the inhibition of tumor necrosis factor

Tumor necrosis factor (TNF) is a proinflammatory cytokine that has a key role in the pathogenesis of a variety of autoimmune diseases-including rheumatoid arthritis-and is an important constituent of the human immune response to infection. At present, three anti-TNF agents are approved (in the US and elsewhere) to treat selected autoimmune diseases: infliximab, etanercept, and adalimumab. These biologic agents have been associated with a variety of serious and 'routine' opportunistic infections; however, differences exist in the mechanisms of action of these agents that might confer variation in their associated risks of infection. From a public-health standpoint, the development of active tuberculosis in some patients who receive anti-TNF therapy is a matter of serious concern. Tuberculosis in such patients frequently presents as extrapulmonary or disseminated disease, and clinicians should be vigilant for tuberculosis in any patient taking anti-TNF therapy who develops fever, weight loss, or cough. To prevent the reactivation of latent tuberculosis infection during anti-TNF therapy, clinicians should screen all patients for tuberculosis, and begin treatment if latent infection is found, before anti-TNF therapy is initiated. Specific tuberculosis screening and treatment strategies vary between geographical regions and are reviewed in this document. The screening strategies employed in Europe and North America have reduced the occurrence of anti-TNF-associated tuberculosis and are clearly to be recommended, but the role of screening in the prevention of other opportunistic (e.g. fungal) infections is far less certain.

Severe adenovirus pneumonia (AVP) following infliximab infusion for the treatment of Crohn's disease

We report a case of severe AVP three weeks following the administration of infliximab for the treatment of Crohn's disease (CD). Since the introduction of tumor necrosis factor-alpha (TNF-alpha) antagonists, various microbiologic agents have been reported to cause pneumonia following their administration. To our knowledge, AVP following therapy with TNF-alpha antagonists has not been reported in English literature. We present a brief review of the mechanism of action of TNF-alpha antagonists and their ability to predispose to various infections including viral pneumonia by interfering with the immune response.

Serious infections with antirheumatic therapy: are biologicals worse?

This paper reviews the current evidence for the role of antirheumatic therapy in the development of serious infections in patients with rheumatoid arthritis (RA). Prednisone is clearly associated with increased infectious risk, but no definitive data link methotrexate to infection. Emerging data suggest that biological agents also pose increase infectious risk, particularly when used in combination with corticosteroids or methotrexate. Further research is needed in this important aspect of RA treatment. In the meantime, the author recommends that physicians should remain vigilant for serious infections in their patients with RA and use appropriate vaccines and screening procedures to mitigate their risk.

Inhibition of TNFalpha does not induce viral reactivation in patients with chronic hepatitis C infection: two cases

Chronic infections, such as hepatitis C, in the setting of rheumatic disorders pose a potential hindrance to optimal management because of possible complications linked to the institution of immune suppression, as well as the high incidence of hepatotoxicity associated with many of the disease-modifying antirheumatic drugs included in the conventional therapeutic regimens. In the setting of hepatitis C, however, the effect of TNFalpha blockade may be potentially beneficial because TNFalpha appears to be involved in the pathogenesis of liver fibrosis through the stimulation of apoptotic pathways. Data related to this subject are, unfortunately, still limited and without detailed information regarding the clinical progression of the rheumatic disorder. We report the cases of two patients, one with ankylosing spondylitis and one with psoriatic arthritis, who were efficiently treated long-term with anti-TNF agents for their rheumatic disease without any evidence of reactivation or flaring of their hepatitis C infection or deterioration of their liver function. Our results indicate that TNFalpha blockade is a highly efficient and uncompromising therapy in hepatitis C-affected individuals with connective tissue disorders. However, systematic, large-scale studies addressing the issue of safety of these new efficient drugs, i.e., monoclonal antibodies targeted against TNFalpha, in patients with chronic hepatitis C will be needed to properly assess the risks and benefits of this treatment in analogous cases.

Transient hemophagocytosis with deficient cellular cytotoxicity, monoclonal immunoglobulin M gammopathy, increased T-cell numbers, and hypomorphic NEMO mutation

X-linked osteopetrosis, anhydrotic ectodermal dysplasia, and immunodeficiency (XL-O-EDA-ID) is a disorder that is caused by hypomorphic mutations in the nuclear factor kappaB essential modulator (NEMO). These mutations lead to an impaired NF-kappaB activation. In vitro analyses and studies in animal models show that inhibition of NF-kappaB leads to a decrease of cytokine production and T-cell proliferation. Patients classically display poor or delayed inflammatory response to infections. We describe a boy with XL-O-EDA-ID, 1167-1168insC NEMO mutation, and recurrent infections. In early infancy, he experienced hemophagocytosis with transient deficiency of natural killer activity. Increased immunoglobulin M levels in blood resulted from a monoclonal immunoglobulin M gammopathy. Blood T-cell numbers were constantly increased, most probably resulting from a peripheral T-cell expansion. Our observations suggest that patients with hypomorphic NEMO mutations and repeated infections may experience inflammatory dysregulation.