Gerald J. Gleich

The eosinophil and bronchial asthma: Current understanding

Article synthese au sujet des effets physiologiques et pathologiques des eosinophiles dans les asthmes bronchiques. des proteines majeures basiques (MBP) dont la concentration est elevee dans les lavages bronchoalveolaires des patients, ont ete etudiees

The eosinophil and the pathophysiology of asthma

Eosinophilia of lung and blood associated with injury to the mucociliary escalator and excessive shedding of bronchial epithelium are hallmarks of both allergic and nonallergic asthma. In vitro, the eosinophil granule major basic protein (MBP) is toxic to helminths and to mammalian cells, including human respiratory epithelium. The MBP-mediated damage to the respiratory epithelium consists of desquamation and frank destruction of ciliated cells. Increased sputum MBP concentration is a good marker for asthma, and patients treated for acute asthma have high levels of MBP in their sputa, which decrease after treatment. Peak sputum MBP levels approximate concentrations toxic to respiratory epithelium in vitro. In the lungs of patients who had died of asthma, MBP has been localized outside of the eosinophil in association with damage to the epithelium. Overall, these and other findings suggest the hypothesis that the eosinophil mediates damage to the respiratory epithelium and is the prime effector cell in the pathophysiology of asthma.

Catapult-like release of mitochondrial DNA by eosinophils contributes to antibacterial defense

Although eosinophils are considered useful in defense mechanisms against parasites, their exact function in innate immunity remains unclear. The aim of this study is to better understand the role of eosinophils within the gastrointestinal immune system. We show here that lipopolysaccharide from Gram-negative bacteria activates interleukin-5 (IL-5)- or interferon-γ–primed eosinophils to release mitochondrial DNA in a reactive oxygen species–dependent manner, but independent of eosinophil death. Notably, the process of DNA release occurs rapidly in a catapult-like manner—in less than one second. In the extracellular space, the mitochondrial DNA and the granule proteins form extracellular structures able to bind and kill bacteria both in vitro and under inflammatory conditions in vivo. Moreover, after cecal ligation and puncture, Il5-transgenic but not wild-type mice show intestinal eosinophil infiltration and extracellular DNA deposition in association with protection against microbial sepsis. These data suggest a previously undescribed mechanism of eosinophil-mediated innate immune responses that might be crucial for maintaining the intestinal barrier function after inflammation-associated epithelial cell damage, preventing the host from uncontrolled invasion of bacteria.

Treatment of Patients with the Hypereosinophilic Syndrome with Mepolizumab

BACKGROUNDnThe hypereosinophilic syndrome is a group of diseases characterized by persistent blood eosinophilia, defined as more than 1500 cells per microliter with end-organ involvement and no recognized secondary cause. Although most patients have a response to corticosteroids, side effects are common and can lead to considerable morbidity.nnnMETHODSnWe conducted an international, randomized, double-blind, placebo-controlled trial evaluating the safety and efficacy of an anti-interleukin-5 monoclonal antibody, mepolizumab, in patients with the hypereosinophilic syndrome. Patients were negative for the FIP1L1-PDGFRA fusion gene and required prednisone monotherapy, 20 to 60 mg per day, to maintain a stable clinical status and a blood eosinophil count of less than 1000 per microliter. Patients received either intravenous mepolizumab or placebo while the prednisone dose was tapered. The primary end point was the reduction of the prednisone dose to 10 mg or less per day for 8 or more consecutive weeks.nnnRESULTSnThe primary end point was reached in 84% of patients in the mepolizumab group, as compared with 43% of patients in the placebo group (hazard ratio, 2.90; 95% confidence interval [CI], 1.59 to 5.26; P<0.001) with no increase in clinical activity of the hypereosinophilic syndrome. A blood eosinophil count of less than 600 per microliter for 8 or more consecutive weeks was achieved in 95% of patients receiving mepolizumab, as compared with 45% of patients receiving placebo (hazard ratio, 3.53; 95% CI, 1.94 to 6.45; P<0.001). Serious adverse events occurred in seven patients receiving mepolizumab (14 events, including one death; mean [+/-SD] duration of exposure, 6.7+/-1.9 months) and in five patients receiving placebo (7 events; mean duration of exposure, 4.3+/-2.6 months).nnnCONCLUSIONSnOur study shows that treatment with mepolizumab, an agent designed to target eosinophils, can result in corticosteroid-sparing for patients negative for FIP1L1-PDGFRA who have the hypereosinophilic syndrome. (ClinicalTrials.gov number, NCT00086658 [ClinicalTrials.gov].).

Treatment of hypereosinophilic syndrome with imatinib mesilate

Patients with hypereosinophilic syndrome show persistent eosinophilia without recognised cause. We treated five such patients with 100 mg imatinib mesilate (formerly STI-571) daily; four male patients with normal serum interleukin 5 showed complete haematological responses; a female patient who did not respond had raised serum interleukin-5 concentrations. One patient developed leucopenia after 4 days of treatment; counts returned to normal when treatment was stopped. After 1 month, eosinophilia recurred; with further treatment for 2 days, eosinophil counts again became normal. All patients who responded stopped other treatments and reduced imatinib mesilate to 200 mg per week. This drug effectively controls eosinophilia in patients with hypereosinophilic syndrome and normal interleukin-5 concentrations.

Episodic Angioedema Associated with Eosinophilia

We studied four patients with recurrent attacks of angioedema, urticaria, and fever. During attacks, body weights increased up to 18 per cent, and leukocyte counts reached 108,000 per microliter (88 per cent eosinophils). The disease did not appear to threaten the function of vital organs. The two children received prednisone intermittently; the adults did not require treatment or were given alternate-day prednisone. Glucocorticoid therapy caused defervescence and diuresis and decreased total leukocyte and eosinophil counts. No patient had evidence of cardiac involvement (follow-up, 2 to 17 years). One patient remained in spontaneous remission for 20 years before symptoms recurred. Histologic studies showed that eosinophils localized and degranulated in the dermis, and they appeared to induce edema. Although this syndrome might be classified as a variant of the hypereosinophilic syndrome, we believe it is a separate entity because of its distinctive characteristics and its benign course.

Hypereosinophilic syndrome: A multicenter, retrospective analysis of clinical characteristics and response to therapy

BACKGROUNDnHypereosinophilic syndrome (HES) is a heterogeneous group of rare disorders defined by persistent blood eosinophilia > or =1.5 x 10(9)/L, absence of a secondary cause, and evidence of eosinophil-associated pathology. With the exception of a recent multicenter trial of mepolizumab (anti-IL-5 mAb), published therapeutic experience has been restricted to case reports and small case series.nnnOBJECTIVEnThe purpose of the study was to collect and summarize baseline demographic, clinical, and laboratory characteristics in a large, diverse cohort of patients with HES and to review responses to treatment with conventional and novel therapies.nnnMETHODSnClinical and laboratory data from 188 patients with HES, seen between January 2001 and December 2006 at 11 institutions in the United States and Europe, were collected retrospectively by chart review.nnnRESULTSnEighteen of 161 patients (11%) tested were Fip1-like 1-platelet-derived growth factor receptor alpha (FIP1L1-PDGFRA) mutation-positive, and 29 of 168 patients tested (17%) had a demonstrable aberrant or clonal T-cell population. Corticosteroid monotherapy induced complete or partial responses at 1 month in 85% (120/141) of patients with most remaining on maintenance doses (median, 10 mg prednisone equivalent daily for 2 months to 20 years). Hydroxyurea and IFN-alpha (used in 64 and 46 patients, respectively) were also effective, but their use was limited by toxicity. Imatinib (used in 68 patients) was more effective in patients with the FIP1L1-PDGFRA mutation (88%) than in those without (23%; P < .001).nnnCONCLUSIONnThis study, the largest clinical analysis of patients with HES to date, not only provides useful information for clinicians but also should stimulate prospective trials to optimize treatment of HES.

Refining the definition of hypereosinophilic syndrome

Because of advances in our understanding of the hypereosinophilic syndrome (HES) and the availability of novel therapeutic agents, the original criteria defining these disorders are becoming increasingly problematic. Here, we discuss shortcomings with the current definition of HES and recent developments in the classification of these disorders. Despite significant progress in our understanding of the pathogenesis of some forms of HES, the current state of knowledge is still insufficient to formulate a new comprehensive etiologic definition of HESs. Nevertheless, we suggest a new working definition that overcomes some of the most obvious limitations with the original definition.

Eosinophilic Esophagitis in Adults Is Associated With IgG4 and Not Mediated by IgE

BACKGROUND & AIMSnEosinophilic esophagitis is usually triggered by foods, by unclear mechanisms. We evaluated the roles of IgE and IgG4 in the development of eosinophilic esophagitis.nnnMETHODSnWe performed a prospective, randomized, double-blind, placebo-controlled trial of adults with eosinophilic esophagitis given an antibody against IgE (omalizumab, nxa0= 16) or placebo (nxa0= 14) every 2-4 weeks for 16 weeks, based on weight and serum level of IgE. Endoscopy was performed, esophageal biopsy specimens were collected, and symptoms were assessed at baseline and at 16 weeks. Maximum numbers of eosinophils/high-power field were determined. Homogenates of esophageal biopsy specimens from 11 subjects with eosinophilic esophagitis and 8 without (controls) were assessed for IgM, IgA, and IgG subclasses. In a retrospective analysis, we performed immunofluorescence analysis of IgG4 in fixed esophageal tissues from 2 patients with eosinophilic esophagitis who underwent esophagectomy and 47 consecutive autopsies (controls). We also performed immunofluorescence analysis of IgG4 in esophageal mucosal biopsy specimens from 24 subjects with eosinophilic esophagitis and 9 without (controls). Finally, sera were collected from 15 subjects with eosinophilic esophagitis and from 41 without (controls), and assayed for total and food-reactive IgG4.nnnRESULTSnOmalizumab did not alter symptoms of eosinophilic esophagitis or eosinophil counts in biopsy samples compared with placebo. Homogenates of esophageal tissues from patients with eosinophilic esophagitis had a 45-fold increase in IgG4 compared with controls (P < 3xa0× 10(-5)), but no significant increases in other IgG subclasses, IgM, or IgA. Sparse stromal deposits resembling immune complexes were found in 2 of 5 eosinophilic esophagitis biopsy specimens based on ultrastructural analysis. Esophagectomy samples from 2 patients with eosinophilic esophagitis contained 180 and 300 IgG4 plasma cells/maximal high-power field, mainly in the deep lamina propria; these levels were greater than in tissues from controls. Fibrosis essentially was exclusive to the lamina propria. Granular extracellular IgG4 was detected in biopsy specimens from 21 of 24 patients with eosinophilic esophagitis, butxa0in none of the specimens from 9 controls (Pxa0= 6xa0× 10(-6)). The total serum level of IgG4 increased only slightly in patients with eosinophilic esophagitis, compared with controls. Subjects withxa0eosinophilic esophagitis had increased serum levels of IgG4 that reacted with milk, wheat, egg, and nuts-the 4 foods thatxa0most commonly trigger this condition (P ≤ 3xa0× 10(-4) for each food).nnnCONCLUSIONSnIn a prospective trial, omalizumab did not reduce symptoms of eosinophilic esophagitis or tissue eosinophil counts compared with placebo. This finding, along with observed granular deposits of IgG4, abundant IgG4-containing plasma cells, and serum levels of IgG4 reactive to specific foods, indicate that, in adults, eosinophilic esophagitis is IgG4-associated, and not an IgE-induced allergy. ClinicalTrials.gov number: NCTxa000123630.

Long-term safety of mepolizumab for the treatment of hypereosinophilic syndromes

BACKGROUNDnHypereosinophilic syndromes (HESs) are chronic disorders that require long-term therapy to suppress eosinophilia and clinical manifestations. Corticosteroids are usually effective, yet many patients become corticosteroid refractory or develop corticosteroid toxicity. Mepolizumab, a humanized monoclonal anti-IL-5 antibody, showed corticosteroid-sparing effects in a double-blind, placebo-controlled study of FIP1L1/PDGFRA-negative, corticosteroid-responsive subjects with HESs.nnnOBJECTIVEnWe evaluated long-term safety and efficacy of mepolizumab (750 mg) in HES.nnnMETHODSnMHE100901 is an open-label extension study. The primary end point was the frequency of adverse events (AEs). Optimal dosing frequency, corticosteroid-sparing effect of mepolizumab, and development of antimepolizumab antibodies were also explored.nnnRESULTSnSeventy-eight subjects received 1 to 66 mepolizumab infusions each (including mepolizumab infusions received in the placebo-controlled trial). Mean exposure was 251 weeks (range, 4-302 weeks). The most common dosing interval was 9 to 12 weeks. The incidence of AEs was 932 events per 100 subject-years in the first year, declining to 461 events per 100 subject-years after 48 months. Serious AEs, including 1 death, were reported by the investigator as possibly due to mepolizumab in 3 subjects. The median daily prednisone dose decreased from 20.0 to 0 mg in the first 24 weeks. The median average daily dose for all subjects over the course of the study was 1.8 mg. Sixty-two percent of subjects were prednisone free without other HES medications for ≥ 12 consecutive weeks. No neutralizing antibodies were detected. Twenty-four subjects withdrew before study completion for death (n = 4), lack of efficacy (n = 6), or other reasons.nnnCONCLUSIONnMepolizumab was well tolerated and effective as a long-term corticosteroid-sparing agent in PDGFRA-negative HES.