An intravascular immune response to Borrelia burgdorferi involves Kupffer cells and iNKT cells.

Here we investigate the dynamics of the hepatic intravascular immune response to a pathogen relevant to invariant natural killer T cells (iNKT cells). Immobilized Kupffer cells with highly ramified extended processes into multiple sinusoids could effectively capture blood-borne, disseminating Borrelia burgdorferi, creating a highly efficient surveillance and filtering system. After ingesting B. burgdorferi, Kupffer cells induced chemokine receptor CXCR3-dependent clustering of iNKT cells. Kupffer cells and iNKT cells formed stable contacts via the antigen-presenting molecule CD1d, which led to iNKT cell activation. An absence of iNKT cells caused B. burgdorferi to leave the blood and enter the joints more effectively. B. burgdorferi that escaped Kupffer cells entered the liver parenchyma and survived despite Ito cell responses. Kupffer cell-iNKT cell interactions induced a key intravascular immune response that diminished the dissemination of B. burgdorferi.

Systemic Fibrocyte Levels and Keloid Expression of the Chemoattractant CXCL12 Are Upregulated Compared With Patients With Normal Scar.

BACKGROUND: Fibrocytes are bone marrow mesenchymal precursors with a surface phenotype compatible with leukocytes, fibroblasts, and hematopoietic progenitors that have been shown to traffic to wound healing sites in response to described chemokine pathways. Keloids are focal fibrotic responses to cutaneous trauma characterized by disordered collagen, which may be associated with elevated systemic fibrocyte levels and/or wound bed chemokine expression. METHODS: Blood specimens from patients with longstanding keloids and those who form grossly normal scars were assayed by fluorescence activated cell sorting analysis for fibrocytes (CD45+, Col I+). The expression of the fibrocyte chemotactic cell surface marker CXCR4, intracellular markers of fibroblast differentiation (pSMAD2/3), and plasma levels of the CXCR4 cognate CXCL12 were compared. Keloid specimens and grossly normal scars were excised, and local expression of CXCL12 was assayed. RESULTS: Keloid-forming patients demonstrated a significantly greater number of circulating fibrocytes (17.4 × 105 cells/mL) than control patients (1.01 × 105 cells/mL, P = 0.004). The absolute number of fibrocytes expressing CXCR4 was significantly greater (P = 0.012) in keloid-forming patients. Systemic CXCL12 levels were insignificantly greater in keloid-forming patients than controls. Keloid specimens had significantly greater CXCL12 expression (529.3 pg/mL) than normal scar (undetectable). CONCLUSIONS: Systemic fibrocyte levels and the CXCR4/CXCL12 biologic axis responsible for fibrocyte trafficking to areas of regional fibrosis were both upregulated in patients who form keloids compared with controls. Keloids persistently expressed CXLC12, which serves both as the main chemoattractant for fibrocytes and a downstream mediator for local inflammation, suggesting a role for this biologic axis in keloid formation and possibly recurrence.

Increased type 2 inflammation post rhinovirus infection in patients with moderate asthma.

Rhinovirus (RV) infections are a major cause of exacerbations in patients with asthma. Experimental RV challenges can provide insight into the pathophysiology of viral exacerbations. Previous reports, investigating mild or moderate asthma patients, have shown an upregulation in type 2 inflammation post RV infection, however, studies specifically involving asthma patients taking inhaled corticosteroids have concentrated on symptoms and lung function, rather than the inflammatory response. Eleven moderate asthma patients were inoculated with RV. Cold symptoms and asthma control were assessed at baseline and post infection. Nasal epithelial lining fluid and bronchial alveolar lavage (BAL) fluid were collected at baseline and 4 days post infection for assessment of inflammatory proteins. Patients suffered increased cold symptoms and decreased asthma control within 7 days of infection. Antiviral mechanisms were induced following inoculation, with increases in interferon -α, ß, γ and λ, as well as CXCL10 and CXCL11. Type 2 inflammatory cytokines were also significantly elevated post RV infection in both nasal and bronchial samples. In BAL, epithelial derived IL-25 and IL-33 levels strongly correlated with Th2 cytokines, IL-4, IL-5 and IL-13. We show how experimental rhinovirus challenge regulates lung and nasal biomarkers in asthma patients taking inhaled corticosteroids. These biomarkers could be used to evaluate the effects of novel drugs for asthma.

Number, activation, and differentiation of circulating fibrocytes correlate with asthma severity.

BACKGROUND: A biomarker that predicts poor asthma control would be clinically useful. Fibrocytes are bone marrow-derived circulating progenitor cells that have been implicated in tissue fibrosis and T(H)2 responses in asthmatic patients. OBJECTIVE: We sought to test the hypothesis that the concentration and activation state of peripheral blood fibrocytes correlates with asthma severity. METHODS: By using fluorescence-activated cell sorting analysis, fibrocytes (CD45(+) and collagen 1 [Col1](+)) were enumerated and characterized in the buffy coats of fresh peripheral blood samples from 15 control subjects and 40 asthmatic patients. RESULTS: Concentrations of peripheral blood total (CD45(+)Col1(+)), activated (the TGF-ß transducing protein phosphorylated SMAD2/3 [p-SMAD2/3](+) or phosphorylated AKT [p-AKT](+)), and differentiated (α-smooth muscle actin [α-SMA](+)) fibrocytes were increased in asthmatic patients compared with control subjects. The increase in total and CD45(+)Col1(+)CXCR4(+) fibrocytes was primarily seen in patients with severe asthma (Global Initiative for Asthma steps 4-5) as opposed to those with milder asthma (Global Initiative for Asthma steps 1-3). In addition, numbers of circulating α-SMA(+) and α-SMA(+)CXCR4(+) fibrocytes were increased in asthmatic patients experiencing an asthma exacerbation in the preceding 12 months. A significant correlation (P < .05) was observed between CD45(+)Col1(+)CXCR4(+) fibrocytes and the activation phenotypes CD45(+)Col1(+)p-SMAD2/3(+) and CD45(+)Col1(+)p-AKT(+). CONCLUSION: There was correlation between circulating fibrocyte subsets and asthma severity, and there was an increased number of activated/differentiated fibrocytes in circulating blood of asthmatic patients experiencing an exacerbation in the preceding 12 months.

Intravenous anti-IL-13 mAb QAX576 for the treatment of eosinophilic esophagitis.

BACKGROUND: Eosinophilic esophagitis (EoE) is a chronic allergic disease with limited treatment options. OBJECTIVE: We evaluated QAX576, an mAb against IL-13, in the treatment of patients with EoE. METHODS: Patients (18-50 years) with proton pump inhibitor-resistant esophageal eosinophilia received intravenous QAX576 (6 mg/kg) or placebo (2:1) at weeks 0, 4, and 8 and were followed for 6 months. The primary end point was the responder rate for a greater than 75% decrease in peak eosinophil counts at week 12. Efficacy was to be declared if the lower 90% confidence limit for the proportion of responders on QAX576 was 35% or greater. Secondary end points included changes in esophageal eosinophil counts, symptoms assessed by questionnaire scores, and quantification of a series of biomarkers. RESULTS: Twenty-three patients completed the study up to week 12, and 18 continued to the end of the study. For the proximal and distal esophageal biopsies combined, the responder rate was 12.5% (90% confidence limit, 1% to 43%) with placebo, compared to 40.0% (90% confidence limit, 22% to 61%) with QAX576. Although the primary end point was not met, the mean esophageal eosinophil count decreased by 60% with QAX576 versus an increase of 23% with placebo (P = .004), and the decrease was sustained up to 6 months. There was a trend for improved symptoms, particularly dysphagia. QAX576 improved expression of EoE-relevant esophageal transcripts, including eotaxin-3, periostin, and markers of mast cells and barrier function, for up to 6 months after treatment. QAX576 was well tolerated. CONCLUSIONS: QAX576 significantly improved intraepithelial esophageal eosinophil counts and dysregulated esophageal disease-related transcripts in adults with EoE in a sustained manner.

Circulating fibrocytes as biomarker of prognosis in Hermansky-Pudlak syndrome.

RATIONALE: The rate of progression of most interstitial lung diseases (ILD) is unpredictable. Fibrocytes are circulating bone marrow-derived cells that have been implicated in the pathogenesis of lung fibrosis. Hermansky-Pudlak syndrome (HPS), a genetic cause of ILD in early adulthood, allows for study of biomarkers of ILD in a homogeneous population at near-certain risk of developing fibrotic lung disease. OBJECTIVES: To test the hypothesis that, in subjects with HPS, the number or phenotype of circulating fibrocytes predicts progression and outcome of ILD. METHODS: We measured circulating fibrocyte counts and chemokine levels in a cohort of subjects with HPS and healthy control subjects and correlated the results to disease outcome. MEASUREMENTS AND MAIN RESULTS: In a cross-sectional analysis, peripheral blood fibrocyte concentrations were markedly elevated in a subset of subjects with HPS who had ILD but not subjects without lung disease or normal control subjects. The blood concentration of fibrocytes expressing the chemokine receptor CXCR4 correlated significantly with the plasma concentration of the CXCR4 ligand, CXCL12. In a longitudinal study, we found marked episodic elevations in circulating fibrocyte counts over a median follow-up period of 614 days. Elevations in both maximal values and final values of peripheral blood CXCR4(+) fibrocyte concentration were strongly associated with death from ILD. CONCLUSIONS: CXCR4(+) fibrocyte concentration may be useful as a biomarker for outcome of ILD in subjects with HPS.

Adenosine A2B receptor blockade slows growth of bladder and breast tumors.

The accumulation of high levels of adenosine in tumors activates A(2A) and A(2B) receptors on immune cells and inhibits their ability to suppress tumor growth. Deletion of adenosine A(2A) receptors (A(2A)ARs) has been reported to activate antitumor T cells, stimulate dendritic cell (DC) function, and inhibit angiogenesis. In this study, we evaluated the effects of intermittent intratumor injection of a nonselective adenosine receptor antagonist, aminophylline (AMO; theophylline ethylenediamine) and, for the first time to our knowledge, a selective A(2B)AR antagonist, ATL801. AMO and ATL801 slowed the growth of MB49 bladder and 4T1 breast tumors in syngeneic mice and reduced by 85% metastasizes of breast cancer cells from mammary fat to lung. Based on experiments with A(2A)AR(-/-) or adenosine A(2B) receptor(-/-) mice, the effect of AMO injection was unexpectedly attributed to A(2B)AR and not to A(2A)AR blockade. AMO and ATL801 significantly increased tumor levels of IFN-γ and the IFN-inducible chemokine CXCL10, which is a ligand for CXCR3. This was associated with an increase in activated tumor-infiltrating CXCR3(+) T cells and a decrease in endothelial cell precursors within tumors. Tumor growth inhibition by AMO or ATL801 was eliminated in CXCR3(-/-) mice and RAG1(-/-) mice that lack mature T cells. In RAG1(-/-) mice, A(2B)AR deletion enhanced CD86 expression on CD11b(-) DCs. Bone marrow chimera experiments demonstrated that CXCR3 and A(2B)AR expression on bone marrow cells is required for the antitumor effects of AMO. The data suggest that blockade of A(2B)ARs enhances DC activation and CXCR3-dependent antitumor responses.

Identification of the bacterial protein FtsX as a unique target of chemokine-mediated antimicrobial activity against Bacillus anthracis.

Chemokines are a family of chemotactic cytokines that function in host defense by orchestrating cellular movement during infection. In addition to this function, many chemokines have also been found to mediate the direct killing of a range of pathogenic microorganisms through an as-yet-undefined mechanism. As an understanding of the molecular mechanism and microbial targets of chemokine-mediated antimicrobial activity is likely to lead to the identification of unique, broad-spectrum therapeutic targets for effectively treating infection, we sought to investigate the mechanism by which the chemokine CXCL10 mediates bactericidal activity against the Gram-positive bacterium Bacillus anthracis, the causative agent of anthrax. Here, we report that disruption of the gene ftsX, which encodes the transmembrane domain of a putative ATP-binding cassette transporter, affords resistance to CXCL10-mediated antimicrobial effects against vegetative B. anthracis bacilli. Furthermore, we demonstrate that in the absence of FtsX, CXCL10 is unable to localize to its presumed site of action at the bacterial cell membrane, suggesting that chemokines interact with specific, identifiable bacterial components to mediate direct microbial killing. These findings provide unique insight into the mechanism of CXCL10-mediated bactericidal activity and establish, to our knowledge, the first description of a bacterial component critically involved in the ability of host chemokines to target and kill a bacterial pathogen. These observations also support the notion of chemokine-mediated antimicrobial activity as an important foundation for the development of innovative therapeutic strategies for treating infections caused by pathogenic, potentially multidrug-resistant microorganisms.

Angiostatic and chemotactic activities of the CXC chemokine CXCL4L1 (platelet factor-4 variant) are mediated by CXCR3.

We investigated possible cellular receptors for the human CXC chemokine platelet factor-4 variant/CXCL4L1, a potent inhibitor of angiogenesis. We found that CXCL4L1 has lower affinity for heparin and chondroitin sulfate-E than platelet factor-4 (CXCL4) and showed that CXCL10 and CXCL4L1 could displace each other on microvascular endothelial cells. Labeled CXCL4L1 also bound to CXCR3A- and CXCR3B-transfectants and was displaced by CXCL4L1, CXCL4, and CXCL10. The CXCL4L1 anti-angiogenic activity was blocked by anti-CXCR3 antibodies (Abs) in the Matrigel and cornea micropocket assays. CXCL4L1 application in CXCR3(-/-) or in wild-type mice treated with neutralizing anti-CXCR3 Abs, resulted in reduced inhibitory activity of CXCL4L1 on tumor growth and vascularization of Lewis lung carcinoma. Furthermore, CXCL4L1 and CXCL4 chemoattracted activated T cells, human natural killer cells, and human immature dendritic cells (DCs). Migration of DCs toward CXCL4 and CXCL4L1 was desensitized by preincubation with CXCL10 and CXCL11, inhibited by pertussis toxin, and neutralized by anti-CXCR3 Abs. Chemotaxis of T cells, natural killer cells, and DCs is likely to contribute to the antitumoral action. However, the in vivo data indicate that the angiostatic property of CXCL4L1 is equally important in retarding tumor growth. Thus, both CXCR3A and CXCR3B are implicated in the chemotactic and vascular effects of CXCL4L1.

Neutrophil mobilization from the bone marrow during polymicrobial sepsis is dependent on CXCL12 signaling.

Neutrophils are essential for successful host eradication of bacterial pathogens and for survival to polymicrobial sepsis. During inflammation, the bone marrow provides a large reserve of neutrophils that are released into the peripheral circulation where they traverse to sites of infection. Although neutrophils are essential for survival, few studies have investigated the mechanisms responsible for neutrophil mobilization from the bone marrow during polymicrobial sepsis. Using a cecal ligation and puncture model of polymicrobial sepsis, we demonstrated that neutrophil mobilization from the bone marrow is not dependent on TLR4, MyD88, TRIF, IFNARα/ß, or CXCR2 pathway signaling during sepsis. In contrast, we observed that bone marrow CXCL12 mRNA abundance and specific CXCL12 levels are sharply reduced, whereas splenic CXCR4 mRNA and cell surface expression are increased during sepsis. Blocking CXCL12 activity significantly reduced blood neutrophilia by inhibiting bone marrow release of granulocytes during sepsis. However, CXCL12 inhibition had no impact on the expansion of bone marrow neutrophil precursors and hematopoietic progenitors. Bone marrow neutrophil retention by CXCL12 blockade prevented blood neutrophilia, inhibited peritoneal neutrophil accumulation, allowed significant peritoneal bacterial invasion, and increased polymicrobial sepsis mortality. We concluded that changes in the pattern of CXCL12 signaling during sepsis are essential for neutrophil bone marrow mobilization and host survival but have little impact on bone marrow granulopoiesis.

Plasma CXCL12 levels as a predictor of future stroke.

BACKGROUND AND PURPOSE: The chemokine ligand CXCL12 is constitutively expressed in the bone marrow and other tissues including the brain endothelium and is responsible for regulating the trafficking of bone marrow progenitor cells. CXCL12 has been shown to play a significant role in animal models of ischemic stroke but its role in human stroke is unclear. The aim of this study was to test the hypothesis that elevated circulating baseline CXCL12 levels are associated with subsequent stroke. METHODS: We prospectively collected demographic and angiographic data from consecutive patients referred for elective coronary angiography. Before coronary angiography a peripheral blood sample was collected for subsequent measurement of CXCL12. One-year stroke risk was calculated using the Framingham Risk Profile. Clinical follow-up was performed at 6 months and 1 year. RESULTS: Of 206 subjects enrolled, 10 (4.9%) sustained an ischemic stroke over the 1 year follow-up. There were no significant differences in baseline clinical characteristics or angiographic findings. However, median CXCL12 levels were significantly higher in those who sustained an ischemic stroke compared with those who did not (10 856 pg/mL versus 2241 pg/mL, P=0.007). The time to stroke distribution between subjects with baseline CXCL12 levels≥10 421 pg/mL and those with baseline CXCL12 levels<10 421 pg/mL was significantly different (log rank P<0.001). The weighted Cox proportional hazard model demonstrated that baseline CXCL12 levels≥10 421 pg/mL were significantly associated with ischemic stroke at follow-up (hazard ratio, 15.29; 95% CI, 3.05-76.71). CONCLUSIONS: Plasma CXCL12 levels may represent a novel biomarker of future ischemic stroke.

Liver inflammation in a mouse model of Th1 hepatitis despite the absence of invariant NKT cells or the Th1 chemokine receptors CXCR3 and CCR5.

The specific mechanisms that mediate CD4(+) T-cell-mediated liver injury have not been fully elucidated. CD4(+) invariant natural killer T (iNKT) cells are required for liver damage in some mouse models of hepatitis, while the chemokine receptors CXCR3 and CCR5 are considered dominant Th1 chemokine receptors involved in Th1 trafficking in inflammatory conditions. BALB/c-Tgfb1(-/-) mice spontaneously develop Th1 hepatitis. Here, we directly test the hypotheses that iNKT cells or the Th1-cell chemokine receptors CXCR3 and CCR5 are required for development of liver disease in Tgfb1(-/-) mice. Tgfb1(-/-) mouse livers exhibited significant increases in iNKT cells and in ligands for CXCR3 or CCR5. Tgfb1(-/-) mice were rendered deficient in iNKT cells, CXCR3, CCR5, or both CXCR3 and CCR5, by cross-breeding with appropriate knockout mice. Tgfb1(-/-) mice developed severe liver injury, even in the absence of functional CD1d/iNKT cells, CXCR3, CCR5, or both CXCR3 and CCR5. Liver CD4(+) T cells accumulated to high numbers, and spleen CD4(+) T-cell numbers declined, regardless of the functionality of the CXCR3/CCR5 response pathways. Similarly, dendritic cells and macrophages accumulated in Tgfb1(-/-) livers even when CXCR3 and CCR5 were knocked out. Th1-associated cytokines (IFN-γ, TNF-α, IL-2) and chemokines (CXCL9, CXCL10) were strongly overexpressed in Tgfb1(-/-) mice despite knockouts in CD1d, CXCR3, or CCR5. These studies indicate that the cellular and biochemical basis for CD4(+) T-cell-mediated injury in liver can be complex, with myriad pathways potentially involved.

Interferon-inducible CXC chemokines directly contribute to host defense against inhalational anthrax in a murine model of infection.

Chemokines have been found to exert direct, defensin-like antimicrobial activity in vitro, suggesting that, in addition to orchestrating cellular accumulation and activation, chemokines may contribute directly to the innate host response against infection. No observations have been made, however, demonstrating direct chemokine-mediated promotion of host defense in vivo. Here, we show that the murine interferon-inducible CXC chemokines CXCL9, CXCL10, and CXCL11 each exert direct antimicrobial effects in vitro against Bacillus anthracis Sterne strain spores and bacilli including disruptions in spore germination and marked reductions in spore and bacilli viability as assessed using CFU determination and a fluorometric assay of metabolic activity. Similar chemokine-mediated antimicrobial activity was also observed against fully virulent Ames strain spores and encapsulated bacilli. Moreover, antibody-mediated neutralization of these CXC chemokines in vivo was found to significantly increase host susceptibility to pulmonary B. anthracis infection in a murine model of inhalational anthrax with disease progression characterized by systemic bacterial dissemination, toxemia, and host death. Neutralization of the shared chemokine receptor CXCR3, responsible for mediating cellular recruitment in response to CXCL9, CXCL10, and CXCL11, was not found to increase host susceptibility to inhalational anthrax. Taken together, our data demonstrate a novel, receptor-independent antimicrobial role for the interferon-inducible CXC chemokines in pulmonary innate immunity in vivo. These data also support an immunomodulatory approach for effectively treating and/or preventing pulmonary B. anthracis infection, as well as infections caused by pathogenic and potentially, multi-drug resistant bacteria including other spore-forming organisms.

Overexpression of CXCL5 is associated with poor survival in patients with pancreatic cancer.

Epithelial neutrophil-activating peptide-78 (CXCL5), a member of the CXC chemokine family, has been shown to be involved in angiogenesis, tumor growth, and metastasis. The objective of this study was to determine the relationship between CXCL5 expression and tumor progression in human pancreatic cancer and to elucidate the mechanism underlying CXCL5-mediated tumor angiogenesis and cancer growth. We report herein that CXCL5 is overexpressed in human pancreatic cancer compared with paired normal pancreas tissue. Overexpression of CXCL5 is significantly correlated with poorer tumor differentiation, advanced clinical stage, and shorter patient survival. Patients with pancreatic cancer and CXCL5 overexpression who underwent resection of cancer had a mean survival time 25.5 months shorter than that of patients who did not overexpress CXCL5. Blockade of CXCL5 or its receptor CXCR2 by small-interfering RNA knockdown or antibody neutralization attenuated human pancreatic cancer growth in a nude mouse model. Finally, we demonstrated that CXCL5 mediates pancreatic cancer-derived angiogenesis through activation of several signaling pathways, including protein kinase B (Akt), extracellular signal-regulated kinase (ERK), and signal transducer and activator of transcription (STAT) in human endothelial cells. These data suggest that CXCL5 is an important mediator of tumor-derived angiogenesis and that it may serve as a survival factor for pancreatic cancer. Blockade of either CXCL5 or CXCR2 may be a critical adjunct antiangiogenic therapy against pancreatic cancer.

Neutropenia enhances lung dendritic cell recruitment in response to Aspergillus via a cytokine-to-chemokine amplification loop.

Current understanding of specific defense mechanisms in the context of neutropenic infections is limited. It has previously been reported that invasive aspergillosis, a prototypic opportunistic infection in neutropenic hosts, is associated with marked accumulation of inflammatory dendritic cells (DCs) in the lungs. Given recent data indicating that neutrophils can modulate immune responses independent of their direct microbial killing, we hypothesized that neutropenia impacts the host response to Aspergillus by determining the migration and phenotype of lung DCs. Inflammatory DCs, but not other DC subsets, were found to accumulate in the lungs of neutropenic hosts challenged with killed or live-attenuated Aspergillus as compared with nonneutropenic hosts, indicating that the accumulation was independent of neutrophil microbicidal activity. The mechanism of this accumulation in neutropenic hosts was found to be augmented influx of DCs, or their precursors, from the blood to the lungs. This effect was attributable to greatly elevated lung TNF expression in neutropenic as compared with nonneutropenic animals. This resulted in greater lung expression of the chemokine ligands CCL2 and CCL20, which, in turn, mediated enhanced recruitment of TNF-producing inflammatory DCs, resulting in a positive feedback cycle. Finally, in the context of neutropenic invasive aspergillosis, depletion of DCs resulted in impaired fungal clearance, indicating that this mechanism is protective for the host. These observations identify what we believe is a novel defense mechanism in invasive aspergillosis that is the result of alterations in DC traffic and phenotype and is specific to neutropenic hosts.

Dysregulated macrophage-inflammatory protein-2 expression drives illness in bacterial superinfection of influenza.

Influenza virus infection is a leading cause of death and disability throughout the world. Influenza-infected hosts are vulnerable to secondary bacterial infection, however, and an ensuing bacterial pneumonia is actually the predominant cause of influenza-attributed deaths during pandemics. A number of mechanisms have been proposed by which influenza may predispose to superinfection with an unrelated or heterologous pathogen, but the subsequent interaction between the host, virus, and bacteria remains an understudied area. In this study, we develop and examine a novel model of heterologous pulmonary infection in which an otherwise subclinical Bordetella parapertussis infection synergizes with an influenza virus infection to yield a life-threatening secondary pneumonia. Despite a profound pulmonary inflammatory response and unaltered viral clearance, bacterial clearance was significantly impaired in heterologously infected mice. No deficits were observed in pulmonary or systemic adaptive immune responses or the viability or function of infiltrating inflammatory cells to explain this phenomenon, and we provide evidence that the onset of severe pulmonary inflammation actually precedes the increased bacterial burden, suggesting that exacerbated inflammation is independent of bacterial burden. To that end, neutralization of the ELR(+) inflammatory chemokine MIP-2 (CXCL2/GRO-beta) attenuated the inflammation, weight loss, and clinical presentation of heterologously infected mice without impacting bacterial burden. These data suggest that pulmonary inflammation, rather than pathogen burden, is the key threat during bacterial superinfection of influenza and that selective chemokine antagonists may be a novel therapeutic intervention in cases of bacterial superinfection of influenza.

Chemokines as mediators of tumor angiogenesis and neovascularization.

Chemokines are a superfamily of structurally homologous heparin-binding proteins that influence tumor growth and metastasis. Several members of the CXC and CC chemokine families are potent inducers of neovascularization, whereas a subset of the CXC chemokines are potent inhibitors. In this paper, we review the current literature regarding the role of chemokines as mediators of tumor angiogenesis and neovascularization.

V(alpha)14iNKT cells promote liver pathology during adenovirus infection by inducing CCL5 production: implications for gene therapy.

Replication-defective recombinant adenoviruses are the most widely studied replication-defective vectors for the potential treatment of inherited human diseases. However, broad clinical application of replication-defective adenoviruses in gene therapy is being hindered by the induction of vigorous innate and adaptive immune responses against the vector that cause deleterious effects in the liver. V(alpha)14 invariant natural killer T cells (V(alpha)14iNKT cells) are thymus-derived innate T cells at the interface between the two arms of the immune response and provide full engagement of host defense. The pathophysiological role of intrahepatic V(alpha)14iNKT cells during replication-defective adenovirus infection is not known and is the main focus of our study. Our data showed that intrahepatic V(alpha)14iNKT cells were activated in response to adenovirus infection to induce significant levels of hepatic chemokine (C-C motif) ligand 5 (CCL5) and subsequent liver toxicity. Moreover, intrahepatic CCL5 production was selectively reduced by V(alpha)14iNKT cell deficiency. In vivo studies utilizing CCL5-deficient mice or V(alpha)14iNKT cell-deficient mice demonstrated that CCL5 deficiency or V(alpha)14iNKT cell deficiency was associated with reduced liver pathology. Similar results were seen after blocking the biological effects of the CCL5 receptors. In conclusion, we have identified an important proinflammatory role for activated intrahepatic V(alpha)14iNKT cells in positively influencing hepatic CCL5 production to promote acute liver inflammation and injury. Therefore, our findings highlight the blockade of CCL5 interaction with a cognate receptor(s) as an important potential strategy to alleviate liver pathology associated with replication-defective adenovirus infection.

NKT cells mediate pulmonary inflammation and dysfunction in murine sickle cell disease through production of IFN-gamma and CXCR3 chemokines.

Ischemia-reperfusion injury (IRI) triggers an inflammatory cascade that is initiated by the activation of CD1d-restricted iNKT cells. In sickle cell disease (SCD), misshapen erythrocytes evoke repeated transient bouts of microvascular IRI. Compared with C57BL/6 controls, NY1DD mice have more numerous and activated (CD69(+), interferon-gamma(+) [IFN-gamma(+)]) lung, liver, and spleen iNKT cells that are hyperresponsive to hypoxia/reoxygenation. NY1DD mice have increased pulmonary levels of IFN-gamma, IFN-gamma-inducible chemokines (CXCL9, CXCL10), and elevated numbers of lymphocytes expressing the chemokine receptor CXCR3. Treating NY1DD mice with anti-CD1d antibody to inhibit iNKT cell activation reverses baseline pulmonary dysfunction manifested as elevated vascular permeability, decreased arterial oxygen saturation, and increased numbers of activated leukocytes. Anti-CD1d antibodies decrease pulmonary levels of IFN-gamma and CXCR3 chemokines. Neutralization of CXCR3 receptors ameliorates pulmonary dysfunction. Crossing NY1DD to lymphocyte-deficient Rag1(-/-) mice decreases pulmonary dysfunction. This is counteracted by the adoptive transfer of 1 million NKT cells. Like mice, people with SCD have increased numbers of activated circulating iNKT cells expressing CXCR3. Together, these data indicate that iNKT cells play a pivotal role in sustaining inflammation in SCD mice by a pathway involving IFN-gamma and production of chemotactic CXCR3 chemokines and that this mechanism may translate to human disease.

Early NK cell-derived IFN-{gamma} is essential to host defense in neutropenic invasive aspergillosis.

Invasive aspergillosis is among the most common human fungal infections and occurs in patients with severe and complex defects in immune responses. NK cells have previously been found to be important in host defense against this infection, but the mechanism of this effect is not known. We hypothesized that NK cells mediate their protective effect in invasive aspergillosis by acting as the major source of IFN-gamma during early infection. We found that, in the lungs of neutropenic mice with invasive aspergillosis, NK cells were the major population of cells capable of generating IFN-gamma during early infection. Depletion of NK cells resulted in reduced lung IFN-gamma levels and increased lung fungal load that was independent of T and B cell subsets. Depletion of NK cells and absence of IFN-gamma resulted in a similar increase in susceptibility to the infection, but depletion of NK cells in IFN-gamma-deficient hosts did not result in further increase in severity of the infection. NK cell-derived IFN-gamma caused enhanced macrophage antimicrobial effects in vitro and also resulted in greater expression of IFN-inducible chemokines in the lungs. Finally, transfer of activated NK cells from wild-type, but not IFN-gamma-deficient hosts, resulted in greater pathogen clearance from the lungs of both IFN-gamma-deficient and wild-type recipients. Taken together, these data indicate that NK cells are the main source of early IFN-gamma in the lungs in neutropenic invasive aspergillosis, and this is an important mechanism in the defense against this infection.