POS1377 LUNG INVOLVEMENT IN VEXAS SYNDROME

Background

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome is a recently identified disorder caused by somatic mutations in the UBA1 gene of myeloid cells. Various manifestations of pulmonary involvement have been reported, but a detailed description of lung involvement and radiologic findings is lacking.

Objectives

To describe lung involvement in VEXAS syndrome.

Methods

A retrospective cohort study was conducted of all patients identified at the Mayo Clinic with VEXAS syndrome since October 2020. Clinical records and chest high resolution computed tomography (HRCT) scans were reviewed.

Results

Our cohort comprised 22 white men with a median age of 69 years (IQR 62-74, range 57-84). Hematologic disorders including multiple myeloma, myelodysplastic syndrome and pancytopenia were present in 10 patients (45%), rheumatologic diseases including granulomatosis with polyangiitis, IgG4-related disease, polyarteritis nodosa, relapsing polychondritis, and rheumatoid arthritis were found in 10 patients (45%), and 4 patients had dermatologic presentations including Sweet syndrome, Schnitzer-like syndrome or drug rash with eosinophilia skin syndrome (DRESS). VEXAS syndrome-related features included fever (18, 82%), skin lesions (20, 91%), lung infiltrates (12, 55%), chondritis (10, 45%), venous thromboembolism (12, 55%), macrocytic anemia (21, 96%), and bone marrow vacuoles (21, 96%). Other manifestations observed were arthritis, scleritis, hoarseness and hearing loss. Median erythrocyte sedimentation rate (ESR) was 69 mm/1st hour (IQR 34.3-118.8) and median C-reactive protein (CRP) of 55.5 mg/dL (IQR 11.4-98.8). The somatic mutations affecting methionine-41 (p.Met41) in UBA1 gene were: 11 (50%) p.Met41Thr, 7 (32%) p.Met41Val, 2 (9%) p.Met41Leu, and 2 (9%) in the splice site. All patients received glucocorticoids (GC) (median duration of treatment was 2.6 years); 21 (96%) received conventional immunosuppressive agents (methotrexate, azathioprine, mycophenolate, leflunomide, cyclosporin, hydroxychloroquine, tofacitinib, ruxolitinib) and 9 (41%) received biologic agents (rituximab, tocilizumab, infliximab, etanercept, adalimumab, golimumab, abatacept). Respiratory symptoms included dyspnea and cough present in 21 (95%) and 12 (55%), respectively, and were documented prior to VEXAS diagnosis. Most of the patients were non-smokers (14, 64%) and obstructive sleep apnea (OSA) was present in 11 patients (50%). Seven patients (32%) used non-invasive ventilation, 6 used C-PAP, and 1 used Bi-PAP. Bronchoalveolar lavage (BAL) was available in 4 patients, and the findings were compatible with neutrophilic alveolitis in 3. Two patients had lung biopsies (2 transbronchial and 1 surgical) that showed ATTR amyloidosis and organizing pneumonia with lymphoid interstitial pneumonia, respectively. Pulmonary function tests were available in 9 (41%) patients and showed normal results in 5; 3 patients had isolated reduction in DLCO and 1 with mild restriction. On chest HRCT, 16 patients (73%) had parenchymal changes including ground-glass opacities in 9, septal thickening in 4, and nodules in 3; pleural effusions were present in 3 patients, air-trapping in 3 patients and tracheomalacia in 1 patient. Follow-up chest HRCT was available for 8 patients (36%), the ground-glass opacities resolved in 5 patients, 3 patients manifested new or increased ground-glass opacities, and 1 patient had increased interlobular septal thickening. After 1 year of follow-up, 4 patients (17%) had died; 3 due to pneumonia (2 COVID-19,1 bacterial) and 1 due to heart failure. VEXAS flares occurred in 18 patients (82%), the maximum number of relapses was 7, and they were mainly managed with GC and with changes in the immunosuppressive regimen.

Conclusion

Pulmonary involvement was documented by chest HRCT in most patients with VEXAS syndrome. Respiratory symptoms occurred in over one half of patients and about 20% had PFT abnormalities. The pulmonary manifestations of VEXAS are nonspecific and characterized predominantly by inflammatory parenchymal involvement.

Disclosure of Interests

None declared

Continuous high-frequency pesticide monitoring to observe the unexpected and the overlooked

Synthetic Plant Protection Products (PPPs) are a key element for a large part of today's global food systems. However, the transport of PPPs and their transformation products (TPs) to water bodies has serious negative effects on aquatic ecosystems. Small streams in agricultural catchments may experience pronounced concentration peaks given the proximity to fields and poor dilution capacity. Traditional sampling approaches often prevent a comprehensive understanding of PPPs and TPs concentration patterns being limited by trade-offs between temporal resolution and duration of the observation period. These limitations result in a knowledge gap for accurate ecotoxicological risk assessment and the achievement of optimal monitoring strategies for risk mitigation. We present here high-frequency PPPs and TPs concentration time-series measured with the autonomous MS²Field platform that combines continuous sampling and on-site measurements with a high-resolution mass spectrometer, which allows for overcoming temporal trade-offs. In a small agricultural catchment, we continuously measured 60 compounds at 20 minutes resolution for 41 days during the growing season. This observation period included 8 large and 15 small rain events and provided 2560 concentration values per compound. To identify similarities and differences among the compound-specific concentration time-series, we analysed the entire dataset with positive matrix factorisation. Six factors sufficiently captured the overall complexity in concentration dynamics. While one factor reflected dilution during rainfall, five factors identified PPPs groups that seemed to share a common history of recent applications. The investigation per event of the concentration time-series revealed a surprising complexity of dynamic patterns; physico-chemical properties of the compounds did not influence the (dis)similarity of chemographs. Some PPPs concentration peaks led while others lagged by several hours the water level peaks during large events. During small events, water level peaks always preceded concentration peaks, which were generally only observed when the water levels had almost receded to pre-event levels. Thus, monitoring schemes relying on rainfall or water level as proxies for triggering sampling may lead to systematic biases. The high temporal resolution revealed that the Swiss national monitoring integrating over 3.5 days underestimated critical concentration peaks by a factor of eight to more than 32, captured 3 out of 11 exceedances of legal acute quality standards (the relevant values in the Swiss Water Protection Law) and recorded 1 out of 9 exceedances of regulatory acceptable concentrations (the relevant values for the PPPs registration process). MS²Field allowed for observing unexpected and overlooked pesticide dynamics with consequences for further research but also for monitoring. The large variability in timing of concentration peaks relative to water level calls for more in-depth analyses regarding the respective transport mechanisms. To perform these analyses, spatially distributed sampling and time-series of geo-referenced PPPs application data are needed.

POS0799 THE EFFICACY AND SAFETY OF TOCILIZUMAB IN PATIENTS WITH GIANT CELL ARTERITIS: A SYSTEMATIC REVIEW AND META-ANALYSIS

Background:

Tocilizumab (TCZ) has been proven to be safe and effective for the treatment of giant cell arteritis (GCA) in 2 randomized controlled trials; however, data from additional types of studies provide valuable information related to the treatment of GCA with TCZ.

Objectives:

To review and analyze efficacy and safety data for TCZ in GCA based on peer-reviewed publications to date.

Methods:

A systematic literature review was conducted according to the PRISMA guidelines. Publications were retrieved from the MEDLINE, Embase, Cochrane, Scopus and Web of Science databases. Publications of clinical trials and retrospective or prospective observational studies (April 11, 2005-October 8, 2019) including patients with GCA (classified based on ACR criteria and/or positive biopsy vs imaging) treated with TCZ and reporting a measure of efficacy were eligible for inclusion. Extracted data included year of publication, year(s) when the study was conducted, number of patients with GCA, method of GCA diagnosis, age and sex, TCZ treatment details (dose, route of administration, frequency, duration), clinical outcome (remission, relapse), serious adverse events (SAEs) following treatment with TCZ, corticosteroid dose before and following TCZ initiation and imaging data following TCZ treatment. Results are presented for the studies (unweighted) and as the weighted population mean. Unweighted mean proportions were calculated as the average of the proportions reported from each study; unweighted means were calculated by computing the mean of individual reported study means. The weighted population proportion was estimated by calculating the total number of patients achieving an outcome and dividing by the total number of patients in all of the studies. The weighted population mean was equivalent to the sum of the individual patient’s outcome values divided by the total number of patients in all of the studies.

Results:

The search retrieved 664 references; 55 full-text articles were reviewed for eligibility, and 36 studies were included in the meta-analysis (Figure 1); the once-weekly and every-2-weeks subcutaneous (SC) TCZ arms of the GiACTA trial were counted as separate studies. A total of 519 patients were included. The median (IQR) duration of treatment with intravenous and SC TCZ was 26.0 (20.0-37.3) and 52.0 (26.0-52.0) weeks, respectively, across all studies in the unweighted analysis and 25.8 (20.8-41.9) and 38.9 (32.4-45.5) weeks in the weighted analysis. The mean (SE) proportion of patients achieving investigator-defined remission at the end of the study was 86.3% (4.3%) and 79.3% (6.0%) in the unweighted and weighted analyses, respectively (Table 1). The mean (SE) proportion of patients who relapsed while receiving TCZ was 2.6% (1.3%) and 12.0% (4.5%) in the unweighted and weighted analyses, respectively. The median prednisone dose at the end of the study was < 5 mg/day, and the mean proportion of patients with SAEs after TCZ initiation was ≈ 14.0%.

Conclusion:

A high proportion of patients with GCA treated with TCZ were in investigator-defined remission at the end of the study across all studies analyzed. These meta-analysis findings add to the evidence of the efficacy and safety of TCZ in GCA.

Table 1.

Summary of Remission, Relapse and Adverse Events

Mean (SE) [95% CI]Across GCA Studies; Unweighted(n = 36 studies)Weighted Population Mean(n = 519 patients)Percentage of patients in investigator-defined remission at the end of the studyn=35n=41186.3 (4.3)79.3 (6.0)[77.6 to 94.9][67.2 to 91.4]Percentage of patients who relapsed while receiving TCZn=31n=392.6 (1.3)12.0 (4.5)[−0.18 to 5.3][2.8 to 21.2]Percentage of patients who relapsed after TCZ discontinuationn=20n=4126.4 (7.8)14.8 (5.8)[10.1 to 42.7][2.7 to 26.9]Percentage of patients receiving no steroids at the end of follow-upn=31n=17041.8 (6.8)49.4 (8.1)[27.8 to 55.8][32.8 to 66.0)Percentage of patients with SAEs after TCZ initiationn=35n=7214.0 (4.1)14.3 (1.3)[5.5 to 22.4][11.7 to 17.0]

Acknowledgements:

This study was sponsored by Genentech, Inc. Support for third-party writing assistance, furnished by Health Interactions, Inc., was provided by Genentech, Inc.

Disclosure of Interests:

Matthew Koster: None declared, Kenneth J Warrington Grant/research support from: Lilly and Kiniksa.(clinical trial support), Jian Han Shareholder of: Genentech, Inc., Employee of: Genentech, Inc., Shalini Mohan Shareholder of: Genentech, Inc., Employee of: Genentech, Inc.

POS0800 VISUAL ISCHEMIA DURING RELAPSE AND FOLLOW-UP OF GIANT CELL ARTERITIS: A SYSTEMATIC REVIEW

Background:

Visual ischemia (VI) is one of the most feared complications in giant cell arteritis (GCA). While the frequencies of VI development at or near diagnosis are better studied, limited information is available regarding the frequency of VI during relapse.

Objectives:

The purpose of this study was to characterize the frequency of visual ischemia (VI) as a manifestation of relapse or during follow-up in patients with GCA through performance of a systematic literature review.

Methods:

Potentially eligible studies were identified from Medline and EMBASE databases from inception to November 31, 2019 using a search strategy that comprised of terms for “giant cell arteritis,” “temporal arteritis,” or “Horton’s disease,” with “relapse,” “recurrence,” “flare,” “outcome,” “follow-up,” or “prognosis.” VI was defined as transient or permanent, full or partial, monocular or binocular visual field loss. VI occurring within 4 wks of GCA diagnosis was considered due to active disease and not included as a relapse event. Inclusion criteria used: (1) original research reported in English, (2) GCA definition provided, (3) VI outcome described as one of the following: (a) relapse rate/frequency denoting the presence or absence of VI, or (b) absolute number of VI events (> 4 weeks after GCA diagnosis) even if total cohort relapse rate/frequency was not provided. In order to reduce bias from under-reporting of negative results, studies that reported relapse rates/frequencies with accompanying relapse characteristics but did not provide initial detail regarding the presence/absence of VI were also identified. In such circumstances, the primary authors were directly contacted for patient-level data regarding VI and these studies were included in the final analysis if such data were available and provided.

Results:

A total of 913 unique articles were identified and underwent screening. Among these, 148 articles underwent independent full-text review by two physicians (K.B. and M.J.K). 33 articles met full inclusion criteria and an additional 21 articles included data on relapse but did not report VI patient data in the publication. Responses were received from authors of 11 of these 21 studies allowing for inclusion. 44 studies accounting for 3,649 patients with GCA were identified. Average percentage of baseline VI was 19% (range 0-66%). The average length of follow-up was 3.4 years (range 0.4 to 8.7). VI developing > 4 weeks after GCA diagnosis was recorded in a total of 53 patients (1.5%).

Study-defined relapses were reported in 36 studies. A total of 1,215 patients with at least one or more relapses were recorded among 2,592 patients under observation (47%). Among these 36 studies, VI occurred in 37 patients (3.0%) with at least one study defined relapse event.

Comparing trial design, retrospective studies (n=25) reported 27 of 2,718 (1%) patients developed VI during follow-up whereas 19 of 541 (3.5%) patients in randomized controlled trials (n=8) developed VI during the trial or post-trial follow-up.

Conclusion:

This report outlines the first systematic review evaluating VI as a manifestation of relapse and during follow-up in GCA. Overall, VI > 4 weeks after GCA diagnosis is uncommon (1.5%) but is noted in up to 3% of patients with at least one relapse event. Frequencies of reported VI were 3.5 times higher in randomized controlled trials compared to retrospective studies.

Disclosure of Interests:

Kubra Bugdayli: None declared, Patompong Ungprasert: None declared, Kenneth J Warrington Grant/research support from: Financial support for research from Kiniksa, Eli Lilly, Matthew Koster: None declared

POS1338 INCIDENCE, PREVALENCE, AND MORTALITY OF CHRONIC PERIAORTITIS: A POPULATION-BASED STUDY

Background:

Chronic periaortitis is an inflammatory condition that typically involves the infrarenal portion of the abdominal aorta. Few studies are available to outline the epidemiology of this rare condition. To date, no epidemiologic studies on periaoritis have been performed in North America.

Objectives:

To evaluate the epidemiology, presentation and outcomes of patients with chronic periaortitis from 1998 through 2018.

Methods:

An inception cohort of patients with incident chronic periaortitis from January 1, 1998 through December 31, 2018, in Olmsted County, Minnesota, USA, was identified based on comprehensive individual medical record review utilizing the Rochester Epidemiology Project medical record linkage system. Inclusion required radiographic and/or histologic confirmation of periarterial soft tissue thickening around at least part of the infra-renal abdominal aorta or the common iliac arteries. Data were collected on demographic characteristics, clinical presentation, renal and radiographic outcomes, and mortality. Incidence rates were age and sex adjusted to the 2010 United States white population.

Results:

Eleven incident cases of chronic periaortitis were identified during the study period. Mean±SD age at diagnosis was 61.8±13.4 years. The cohort included 9 men (82%) and 2 women (18%). The most common presenting symptom was pain with 55% (6/11) reporting abdominopelvic-pelvic pain, 36% (4/11) back pain, and 18% (2/11) flank pain. Obstructive uropathy was present in 73% (8/11) subjects: 3 (27%) unilateral left, 1 (9%) unilateral right, and 4 (36%) bilateral. Mean creatinine at presentation was 2.7±3.4 mg/dL. Ureteral stenting was required at diagnosis in seven patients: unilateral left in 2, unilateral right in 1 and bilateral in 4. All 11 patients received glucocorticoids with a median (IQR) dose of 40 (30, 60) mg/day. Additional non-glucocorticoid therapeutics were used in 10 patients.

Renal function stage at last follow up declined in 2 patients, remained the same in 3 patients and improved in 6 patients. Mean creatinine at last follow-up was 1.2±0.2 mg/dL. Among the seven patients requiring baseline indwelling ureteral stent placement only two required ongoing ureteral stenting at last follow up. None of the four patients without ureteral stenting at diagnosis progressed to require stenting during the follow-up period. No patient underwent ureterolysis surgery in this cohort. Periarterial soft tissue thickening at last follow up had increased in thickness in 1 (9%), was unchanged in 2 (18%), decreased in size but did not resolve in 6 (55%), and fully resolved in 18%.

Age- and sex-adjusted incidence rates per 100,000 population were 0.26 for females, 1.56 for males and 0.87 overall. Overall prevalence on January 1, 2015 was 8.98 per 100,000 population. Median (IQR) length of follow-up was 10.1 (2.5, 13.8) years. Overall mortality was similar to the expected age, sex, and calendar estimates of the Minnesota population with standardized mortality ratio (95% CI) for the entire cohort 2.07 (0.67, 4.84).

Conclusion:

This study reports the first epidemiologic data on chronic periaortitis in the United States. In this cohort of patients with chronic periaortitis, men were approximately 4 times more commonly affected than women. Mortality was not increased compared to the general population.

Disclosure of Interests:

None declared

POS0803 TRENDS IN THE INCIDENCE OF GIANT CELL ARTERITIS ACROSS SEVEN DECADES AND CHANGES IN DIAGNOSTIC MODALITIES: A POPULATION-BASED STUDY

Background:

Diagnostic methods for giant cell arteritis (GCA) have evolved over recent decades, and large vessel imaging plays an increasing role in disease detection.

Objectives:

This study aims to estimate the incidence of GCA over the past 10 years in a population and compare it to preceding incidence estimates. It also explores trends in the diagnostic modalities used to identify GCA.

Methods:

A pre-existing population-based cohort of patients diagnosed with GCA between 1950 and 2009 was extended with incident cases from 2010 to 2019. The diagnosis of GCA was confirmed by review of medical records of patients with ICD9/10 codes for GCA between 1/1/2010 and 12/31/2019. Incident cases that met either one of the following sets of inclusion criteria were added to the cohort: one, American College of Rheumatology 1990 GCA classification criteria; or two, patients aged ≥50 years with elevation of erythrocyte sedimentation rate or C-reactive protein and radiographic evidence of large vessel vasculitis attributed to GCA. Incident cases were classified into one of three groups: group 1, temporal artery biopsy (TAB) positive; group 2, TAB negative or not done with positive large-vessel imaging; or group 3, clinical diagnosis of GCA.

Results:

The study cohort included 305 patients diagnosed with GCA from 1950 until 2019. Fifty-five incident cases were diagnosed between 2010 and 2019; 37 females (67%) and 18 males (33%). The age and sex adjusted incidence rates (95% CI) per 100,000 between 2010 and 2019 for females, males, and the total population were 13.0 (8.8, 17.3), 8.6 (4.6, 12.7), and 10.8 (8.0, 13.7), respectively. The corresponding incidence rates from 2000-2009 were 28.0 (21.0, 35.1), 10.2 (5.0, 15.5), and 20.5 (15.9, 25.1), respectively. This represents a significant decline in the incidence rates in females (p<0.001) and the total group (p<0.001) between the 2000-2009 and 2010-2019 cohorts but no change in males (p=0.64). Of the 55 patients diagnosed between 2010 and 2019, there were 37 (67%) in group 1, 10 (18%) in group 2, and 8 (15%) in group 3. In contrast, of the 250 patients diagnosed between 1950 and 2009 there were 209 (84%) in group 1, 4 (2%) in group 2, and 37 (15%) in group 3. There was a significant difference between the 1950-2009 and 2010-2019 cohorts in the composition of these groups (p<0.001).

Conclusion:

In this population-based cohort of patients with GCA diagnosed over a 70-year period, the incidence of GCA has declined in recent years. The total decline is driven by a decline in females but not in males. The reasons for this are unclear but should be followed over time and investigated in other population-based cohorts. There has also been a shift in the diagnostic modalities for GCA. In recent years, there are fewer TAB positive patients, and more patients diagnosed with large vessel imaging. This is the first population-based incidence cohort demonstrating a trend towards increased use of large vessel imaging for the diagnosis of GCA.

References:

[1]Chandran AK, et al. Incidence of Giant Cell Arteritis in Olmsted County, Minnesota, over a 60-year period 1950-2009. Scand J Rheumatol. 2015;44(3):215-218.

[2]Gonzalez-Gay MA, et al. Giant cell arteritis: is the clinical spectrum of the disease changing? BMC Geriatr. 2019; Jul 29;19(1):200.

[3]Rubenstein E, et al. Sensitivity of temporal artery biopsy in the diagnosis of giant cell arteritis: a systemic literature review and meta-analysis. Rheumatology (Oxford). 2020 May 1:59(5):1011-1020.

Figure 1.

Trends in the incidence of GCA in Olmsted County by sex (1950-2019).

Acknowledgements:

This study was made possible using the resources of the Rochester Epidemiology Project, which is supported by the National Institute on Aging of the National Institutes of Health (NIH) under Award Number R01 AG034676, and CTSA Grant Number UL1 TR000135 from the National Center for Advancing Translational Sciences (NCATS), a component of the NIH. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Disclosure of Interests:

Thomas Garvey: None declared, Cynthia S. Crowson: None declared, Matthew Koster: None declared, Kenneth J Warrington Grant/research support from: Clinical research support from Eli Lilly and Kiniksa

POS0805 TREATMENT OF GIANT CELL ARTERITIS WITH TOCILIZUMAB: A RETROSPECTIVE COHORT STUDY OF 119 PATIENTS

Background:

Giant cell arteritis (GCA) is an inflammatory condition of medium- and large-sized arteries. Prospective clinical trials have demonstrated the efficacy of tocilizumab (TCZ) for treatment of patients with GCA (1). However, there is a limited data on the use of TCZ in routine clinical practice.

Objectives:

To evaluate the efficacy and safety of TCZ in a retrospective cohort study of patients with GCA treated with TCZ.

Methods:

Patients with GCA treated with TCZ at 4 clinical centers of a single tertiary care institution (2000-2020) were identified. The diagnosis of GCA was confirmed by at least one of the following modalities: 1. Arterial biopsy 2. Large vessel imaging 3. Clinical diagnosis of GCA meeting ACR classification criteria and established by a rheumatologist. Patient demographics, clinical presentation, laboratory studies, treatment course and adverse events were abstracted from the medical record; only patients with at least 6 months of follow-up after TCZ initiation were included. Kaplan-Meier methods were used to estimate time to TCZ discontinuation and time to first relapse after TCZ discontinuation. Poisson regression models were used to compare relapse rates before and after TCZ initiation.

Results:

The study cohort included 119 patients [61% female; mean (SD) age at GCA diagnosis 70.3 (8.2) years]. The majority of patients (89%) had a biopsy-proven and/or imaging-based diagnosis of GCA, while 13 (11%) had a clinical diagnosis of GCA. In addition to glucocorticoids, 40 (34%) patients received other immunosuppressive agents prior to TCZ. The method of initial TCZ administration was subcutaneous (162mg/ml) weekly in 48 (41%), subcutaneous every other week in 20 (17%), monthly 4mg/kg infusions in 34 (29%), monthly 8mg/kg infusions in 14 (12%) and non-standard dosing in 3 remaining patients. The median (IQR) duration from GCA diagnosis to TCZ initiation was 4.8 (1.2-22.0) months and the median (IQR) duration of TCZ treatment was 18 (11-28) months. The mean (SD) dose of prednisone at TCZ initiation was 31 (19) mg/day and was reduced to a mean (SD) dose of 3.9 (6.7) mg/day at TCZ discontinuation/last follow-up visit. The relapse rate per year decreased 43% from 0.77 to 0.44 after the initiation of TCZ (RR=0.57; 95% CI: 0.44-0.75; p<0.001). The mean (SD) ESR and CRP decreased from 22 (20) mm/hour to 6 (9.2) mm/hour and from 19.1 (25) mg/L to 5.4 (16.6) mg/L, respectively from TCZ initiation to TCZ discontinuation/last follow-up visit. At 2 years of follow-up, 67% of patients had discontinued glucocorticoids. At last follow up, 46 patients had discontinued TCZ, only 14 of which were due to adverse events. The median time to TCZ discontinuation was 2.9 years. Only 17% (95%CI: 10-24%) had discontinued by 1 year after TCZ initiation and 38% (95% CI: 26-47%) had discontinued by 2 years. The most common adverse events were infections and cytopenias. While on TCZ, 1 patient developed new onset vision loss related to GCA and 1 patient, without history of diverticulitis, had bowel perforation. Among those discontinuing TCZ, 61% had relapsed at least once by 1 year after TCZ discontinuation.

Conclusion:

In this large single institution cohort of patients with GCA, TCZ use resulted in a significantly reduced relapse rate and reduction in glucocorticoid dosage. Overall, patients tolerated long-term use with only 12% discontinuing due to adverse events. However, over half of patients stopping TCZ had a subsequent flare; highlighting ongoing use may be required beyond two years in several patients with GCA to maintain remission.

References:

[1]Stone JH, et al. Trial of Tocilizumab in Giant-Cell Arteritis. N Engl J Med. 2017 Jul 27;377(4):317-328. doi: 10.1056/NEJMoa1613849. PMID: 28745999.

[2]Calderón-Goercke M, et al. Tocilizumab in giant cell arteritis. Observational, open-label multicenter study of 134 patients in clinical practice. Semin Arthritis Rheum. 2019 Aug;49(1):126-135. doi: 10.1016/j.semarthrit.2019.01.003. Epub 2019 Jan 5. PMID: 30655091.

Disclosure of Interests:

Jigisha Rakholiya: None declared, Matthew Koster: None declared, Hannah Langenfeld: None declared, Cynthia S. Crowson: None declared, Andy Abril: None declared, Pankaj Bansal: None declared, Lester Mertz: None declared, Alicia Rodriguez-Pla: None declared, Rahul Sehgal: None declared, Benjamin Wang: None declared, Kenneth J Warrington Grant/research support from: Research support: Kiniksa, Eli Lilly

SAT0277 HEAD AND NECK INVOLVEMENT OF IGA VASCULITIS: A CASE-CONTROL STUDY

Background:

IgA vasculitis (IgAV) is an immune-complex mediated, small-vessel vasculitis which predominantly involves the skin on the lower extremities. Head and neck involvement is rarely reported.

Objectives:

To describe the presentation and outcome of a series of patients with head and/or neck involvement in comparison to patients with cutaneous findings isolated to the lower extremities.

Methods:

Patients with biopsy-proven IgAV from January 1, 1997 through December 31, 2016 were retrospectively identified through direct medical chart review. IgAV was diagnosed in accordance with the American College of Rheumatology (ACR) and the European League Against Rheumatism/ Paediatric Rheumatology European Society/Paediatric Rheumatology International Trials Organisation (EULAR/PRINTO/PRES) criteria. Among this cohort, patients with documented clinical, photographic, or histologic descriptions of vasculitic skin lesions affecting the head or neck were compiled. Each patient with head/neck (H/N) involvement of IgAV (case) was matched to two age- and sex-matched control patients with IgAV for which the cutaneous features were isolated to the waistline or distal. Baseline characteristics, laboratory parameters, treatments and outcome were collected by a physician abstractor.

Results:

Thirteen patients with H/N-IgAV involvement were identified. Baseline characteristics of the cases and controls are demonstrated in Table 1. H/N involvement included facial (cheeks, forehead) [n=6], perioral/oral/lip [n=6], auricular [n=2], nasal [n=2], and neck [n=1]. All patients in both groups had evidence of purpuric skin lesions. Patients with H/N-IgAV involvement more frequently had evidence of skin ulcerations (23% vs. 0%; p=0.01) [Figure 1]. Overall baseline renal involvement and microscopic hematuria were less commonly observed in patients with H/N-IgAV. Among H/N-IgAV cases, at last follow-up all had resolution of H/N lesions but 3 of 13 had persistent skin lesions on the lower extremities despite ongoing treatment. Long-term outcome between cases and controls did not identify any significant differences in the development of end-stage renal disease, time to resolution of hematuria or proteinuria, time to complete IgAV response, or time to first IgAV relapse.

Table 1.

Baseline characteristics of patients with head and neck involvement of IgA-vasculitis compared to those with lower extremity only

Characteristic, n (%)H/N-IgAV(N=13)LE-IgAV(N=26)p-valueAge at diagnosis, years*38 (24)38 (24)1.0Male7 (54%)16 (62%)0.65Caucasian13 (100%)24 (96%)0.47Length of follow-up, years*2.6 (3.5)1.3 (2.0)0.28Body mass index, kg/m2*32 (17)28 (10)0.72Hypertension2 (15%)8 (31%)0.30Infection within 4 weeks7 (54%)11 (42%)0.50Antibiotic exposure within 4 weeks4 (31%)6 (24%)0.65Abdominal ischemic symptoms2 (15%)3 (12%)0.74Palpable purpura13 (100%)26 (100%)---Skin ulceration3 (23%)0 (0%)0.01Any renal involvement5 (38%)19 (73%)0.04Microscopic hematuria4 (31%)17 (65%)0.04Proteinuria4 (31%)15 (58%)0.11C-reactive protein, mg/L*28 (25)22 (22)0.61Erythrocyte sedimentation rate, mm/hr*20 (21)27 (25)0.80eGFR (ml/min/1.73m2)*87 (41)95 (42)0.88

*mean (±standard deviation); H/N, head and/or neck; LE, lower extremity only

Figure 1.

A) H/N involvement in IgAV (perioral, nasal, cheeks and neck). B) Severe PP in lower extremities with bullous, ulcerations and skin necrosis.

Conclusion:

This study reports the largest series of patients with head/neck involvement of IgA, a rarely reported entity. In this cohort, patients with H/N-IgAV had less frequent renal involvement compared to IgAV patients with lower extremity only skin lesions. Clinicians should be aware of atypical locations of IgAV involvement. Additional research is needed to further understand this clinical subset.

Disclosure of Interests:

Michel Villatoro Villar: None declared, David A. Wetter: None declared, Cynthia S. Crowson Grant/research support from: Pfizer research grant, Kenneth J Warrington: None declared, Matthew Koster: None declared

AB0541 IMPROVED SURVIVAL IN PATIENTS WITH GIANT CELL ARTERITIS: A POPULATION-BASED COHORT STUDY

Background:

In previous studies patients with giant cell arteritis (GCA) have had survival rates that are similar to the general population.

Objectives:

To investigate survival trends and cause-specific mortality in patients diagnosed with GCA over a 60-year period.

Methods:

We assembled a population-based incidence cohort of patients with GCA diagnosed between 1950 and 2009. All patients were included if they met the American College of Rheumatology (ACR) 1990 Criteria for the Classification of GCA. Patients diagnosed between 2000 and 2009 could also be included if they met the following criteria: age greater than or equal to 50 years, elevated inflammatory markers, and radiographic evidence of large-vessel vasculitis attributed to GCA. A non-GCA comparison cohort was assembled from the same underlying population for each patient with GCA. Patients were followed until death, last contact, or December 31st, 2018. Survival trends were analyzed by grouping patients into the following categories according to year of GCA diagnosis: Group A 1950-1979; Group B 1980-1989; Group C 1990-1999; and Group D 2000-2009. Mortality rates were estimated using the Kaplan-Meier method and were compared with expected mortality rates for persons of the same age, sex, and calendar year, as estimated by regional population life tables. Cause-specific mortality was obtained from death certificates for patients in both cohorts. The causes were grouped according to ICD-9 chapters and hazard ratios were estimated against the non-GCA comparators.

Results:

The study population included 245 incident cases of GCA: 194 (79%) women and 51 (21%) men with mean age (±SD) of 76.2 (±8.3) years and median follow-up of 10.6 years. There was no overall difference in survival between the GCA cohort and the general population. The 2-, 5-, and 10-year survival rates (95% CI) were 89% (86, 93), 76% (70, 81), and 56% (50, 63) respectively with a standardized mortality ratio of 0.99 (0.86, 1.14). The standardized mortality ratios for Groups A, B, C, and D were 0.83 (0.57, 1.17), 0.92 (0.63, 1.3), 1.21 (0.85, 1.69), 0.70 (0.50, 0.95), respectively. The overall all-cause mortality adjusted for age, sex, and calendar-year was similar between the GCA patients and their comparators with a hazard ratio of 1.03 (0.84, 1.24). Mortality due to neoplasms was significantly lower in the GCA cohort with a hazard ratio of 0.53 (0.3, 0.92). Other cause-specific mortalities were not significantly different between the groups.

Conclusion:

In this population-based cohort of patients with GCA diagnosed over a 60-year period, the survival of patients diagnosed in recent years was significantly better than that of the general population. The explanation for this novel finding is unclear, but likely to be multifactorial. In this study the number of deaths due to neoplasm in the GCA group was significantly lower.

References:

[1]Chandran AK, et al. Incidence of Giant Cell Arteritis in Olmsted County, Minnesota, over a 60-year period 1950-2009. Scand J Rheumatol. 2015;44(3):215-218.

[2]Mohammad A. et al. Rate of comorbidities in Giant Cell Arteritis: A Population-based Study. J Rheumatol. 2017;44(1):84-90.

[3]Salvarani C. et al. Reappraisal of the epidemiology of giant cell arteritis in Olmsted County, Minnesota, over a fifty-year period. Arthritis Rheum. 2004;51(2):264-8.

Acknowledgments:

This study was made possible using the resources of the Rochester Epidemiology Project, which is supported by the National Institute on Aging of the National Institutes of Health (NIH) under Award Number R01 AG034676, and CTSA Grant Number UL1 TR000135 from the National Center for Advancing Translational Sciences (NCATS), a component of the NIH. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Disclosure of Interests:

Thomas Garvey: None declared, Cynthia S. Crowson Grant/research support from: Pfizer research grant, Matthew Koster: None declared, Eric Matteson Grant/research support from: Pfizer, Consultant of: Boehringer Ingelheim, Gilead, TympoBio, Arena Pharmaceuticals, Speakers bureau: Simply Speaking, Kenneth J Warrington: None declared

Non-invasive pressure measurement of the great saphenous vein in healthy controls and patients with venous insufficiency

OBJECTIVES

Venous pressure measurement using an intravenous catheter is the sole method for the diagnosis of venous hypertension in patients with chronic venous insufficiency. A noninvasive tool to quantify increased venous pressure is essential for studying venous pathophysiology. Aim of the study was to investigate the value of controlled compression ultrasound (CCU) for noninvasive assessment of venous pressure (VP) of the great saphenous vein (GSV) in healthy persons and patients with venous insufficiency to quantify venous hypertension.

METHODS

An optimal visible part of the GSV directly above the ankle was marked on the skin and compressed under ultrasound control and pressure needed for complete compression of the vein was recorded using a pressure manometer with a translucent silicone membrane. Complete insufficiency of the GSV (Hach IV) was documented by duplex ultrasound by an independent investigator before start of the study. VP measurement was performed while normal breathing, deep inspiration and expiration and during a standardized Valsalva maneuver.

RESULTS

Twenty controls and 19 patients with complete insufficiency of the GSV were included. Valsalva maneuver induced a slight increase in VP in controls (20.1 ± 4.5 vs 25.1 ± 6.6 mbar) but a significant higher increase in patients from 26 to 37 mbar (IQR 18.5-28.0 vs 31.5-43.0; p < 0.001).

CONCLUSION

Noninvasive venous pressure measurement of the great saphenous vein using CCU is feasible and documents an increased pressure during Valsalva maneuver in Hach IV patients compared to healthy controls.

Towards an integrated community approach of overweight prevention: the experiences of practitioners and policymakers

BACKGROUND

Fighting overweight effectively asks for a community-based coherent integrated approach. The first step in improving the local prevention of overweight is to retrieve practice-based information on the interventions used and the experiences of practitioners.

OBJECTIVES

A variety of practitioners and policymakers in three different cities in The Netherlands were interviewed to investigate: what kind of interventions are used in practice today? What is helpful and what does not to implement these interventions? What is needed? How is the collaboration between the parties involved?

METHODS

Three observers classified all statements systematically according to the four categories from the implementation model by Fleuren M, Wiefferink K, Paulussen T (Determinants of innovation within health care organizations: literature review and Delphi study. Int J Qual Health Care 2004; 16: 107-123).

RESULTS

In Nijmegen, 29 interventions for the prevention or treatment of overweight were identified for the target group youth and 22 for adults. In Wijchen, these were, respectively, 22 and 13 interventions, and in Maasdriel, 24 interventions were found for youth. Most interventions addressed healthy eating and/or physical activity, a few paid attention to psychological or pedagogical aspects. Most participants were satisfied with the intervention(s) they used. For the question 'what does not work?', 61% of the answers were related to characteristics of the organization or social and political context of the intervention. Merely, all sectors expressed difficulties in involving parents.

CONCLUSIONS

Many different interventions are applied in everyday practice within each city, but in a fragmented way. Too little attention is being paid to pedagogical aspects and to involving parents in preventing overweight.

Characterization of Fluorescent Siderophore-Mediated Iron Uptake in Pseudomonas sp. Strain M114: Evidence for the Existence of an Additional Ferric Siderophore Receptor

In Pseudomonas sp. strain M114, the outer membrane receptor for ferric pseudobactin M114 was shown to transport ferric pseudobactins B10 and A225, in addition to its own. The gene encoding this receptor, which was previously cloned on pCUP3, was localized by Tn5 mutagenesis to a region comprising >1.6 kb of M114 DNA. A mutant (strain M114R1) lacking this receptor was then created by a marker exchange technique. Characterization of this mutant by using purified pseudobactin M114 in radiolabeled ferric iron uptake studies confirmed that it was completely unable to utilize this siderophore for acquisition of iron. In addition, it lacked an outer membrane protein band of 89 kDa when subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. As a result, growth of the mutant was severely restricted under low-iron conditions. However, this phenotype was reversed in the presence of another fluorescent siderophore (pseudobactin MT3A) from Pseudomonas sp. strain MT3A, suggesting the presence of a second receptor in strain M114. Furthermore, wild-type Pseudomonas sp. strain B24 was not able to utilize ferric pseudobactin MT3A, and this phenotype was not reversed upon expression of the M114 receptor encoded on pCUP3. However, a cosmid clone (pMS1047) that enabled strain B24 to utilize ferric pseudobactin MT3A was isolated from an M114 gene bank. Radiolabel transport assays with purified pseudobactin MT3A confirmed this event. Plasmid pMS1047 was shown to encode an outer membrane protein of 81 kDa in strain B24 under iron-limiting conditions; this protein corresponds to a similar protein in strain M114.

Peroxisome proliferator-activated receptor-g agonist treatment increases septation and angiogenesis and decreases airway hyperresponsiveness in a model of experimental neonatal chronic lung disease

Chronic lung disease (CLD) affects premature newborns requiring supplemental oxygen and results in impaired lung development and subsequent airway hyperreactivity. We hypothesized that the maintenance of peroxisome proliferator-activated receptor gamma (PPARgamma) signaling is important for normal lung morphogenesis and treatment with PPARgamma agonists could protect against CLD and airway hyperreactivity (AHR) following chronic hyperoxic exposure. This was tested in an established hyperoxic murine model of experimental CLD. Newborn mice and mothers were exposed to room air (RA) or moderate hyperoxia (70% oxygen) for 10 days and fed a standard diet or chow impregnated with the PPARgamma agonist rosiglitazone (ROSI) for the duration of study. Following hyperoxic exposure (HE) animals were returned to RA until postnatal day (P) 13 or P41. The accumulation of ROSI in neonatal and adult tissue was confirmed by mass spectrometry. Analyses of body weight and lung histology were performed on P13 and P41 to localize and quantitate PPARgamma expression, determine alveolar and microvessel density, proliferation and alpha-smooth muscle actin (alpha-SMA) levels as a measure of myofibroblast differentiation. Microarray analyses were conducted on P13 to examine transcriptional changes in whole lung. Pulmonary function and airway responsiveness were analyzed at P55. ROSI treatment during HE preserved septation and vascular density. Key array results revealed ontogeny groups differentially affected by hyperoxia including cell cycle, angiogenesis, matrix, and muscle differentiation/contraction. These results were further confirmed by histological evaluation of myofibroblast and collagen accumulation. Late AHR to methacholine was present in mice following HE and attenuated with ROSI treatment. These findings suggest that rosiglitazone maintains downstream PPARgamma effects and may be beneficial in the prevention of severe CLD with AHR.

Maturation of Pseudomonas aeruginosa Elastase

Elastase of Pseudomonas aeruginosa is synthesized as a preproenzyme. After propeptide-mediated folding in the periplasm, the proenzyme is autoproteolytically processed, prior to translocation of both the mature enzyme and the propeptide across the outer membrane. The formation of the two disulfide bonds present in the mature enzyme was examined by studying the expression of the wild-type enzyme and of alanine for cysteine mutant derivatives in the authentic host and in dsb mutants of Escherichia coli. It appeared that the two disulfide bonds are formed successively. First, DsbA catalyzes the formation of the disulfide bond between Cys-270 and Cys-297 within the proenzyme. This step is essential for the subsequent autoproteolytic processing to occur. The second disulfide bond between Cys-30 and Cys-57 is formed more slowly and appears to be formed after processing of the proenzyme, and its formation is catalyzed by DsbA as well. This second disulfide bond appeared to be required for the full proteolytic activity of the enzyme and contributes to its stability.

Inhibition of L-deleted foot-and-mouth disease virus replication by alpha/beta interferon involves double-stranded RNA-dependent protein kinase

We previously demonstrated that the ability of foot-and-mouth disease virus (FMDV) to form plaques in cell culture is associated with the suppression of alpha/beta interferon (IFN-alpha/beta). In the present study, we used Escherichia coli-expressed porcine and bovine IFN-alpha or -beta individually to demonstrate that each was equally effective in inhibiting FMDV replication. The block in FMDV replication appeared to be at the level of protein translation, suggesting a role for double-stranded RNA-dependent protein kinase (PKR). In support of these findings, treatment of porcine and bovine cells with 2-aminopurine, an inhibitor of PKR, increased the yield of virus 8.8- and 11.2-fold, respectively, compared to that in untreated infected cells. In addition, results of FMDV infection in mouse embryonic fibroblast cells derived from gene knockout mice lacking the gene for RNase L(-/-) or PKR(-/-) or both indicated an important role for PKR in the inhibition of FMDV replication.

Exchange of Xcp (Gsp) secretion machineries between Pseudomonas aeruginosa and Pseudomonas alcaligenes: species specificity unrelated to substrate recognition

Pseudomonas aeruginosa and Pseudomonas alcaligenes are gram-negative bacteria that secrete proteins using the type II or general secretory pathway, which requires at least 12 xcp gene products (XcpA and XcpP to -Z). Despite strong conservation of this secretion pathway, gram-negative bacteria usually cannot secrete exoproteins from other species. Based on results obtained with Erwinia, it has been proposed that the XcpP and/or XcpQ homologs determine this secretion specificity (M. Linderberg, G. P. Salmond, and A. Collmer, Mol. Microbiol. 20:175-190, 1996). In the present study, we report that XcpP and XcpQ of P. alcaligenes could not substitute for their respective P. aeruginosa counterparts. However, these complementation failures could not be correlated to species-specific recognition of exoproteins, since these bacteria could secrete exoproteins of each other. Moreover, when P. alcaligenes xcpP and xcpQ were expressed simultaneously in a P. aeruginosa xcpPQ deletion mutant, complementation was observed, albeit only on agar plates and not in liquid cultures. After growth in liquid culture the heat-stable P. alcaligenes XcpQ multimers were not detected, whereas monomers were clearly visible. Together, our results indicate that the assembly of a functional Xcp machinery requires species-specific interactions between XcpP and XcpQ and between XcpP or XcpQ and another, as yet uncharacterized component(s).

Protein secretion mechanisms in Gram-negative bacteria

Gram-negative bacteria have developed a variety of secretion pathways to secrete toxins and enzymes into the extracellular medium. These pathways are very different with respect to their functional mechanism and complexity, and each system has its own advantages and limitations, regarding the number, size, folding state and fate of their substrates. Pseudomonas aeruginosa secretes many different proteins into the extracellular medium, using at least four secretion pathways. Most of the exoproteins are secreted via the type II system, composed of the 12 Xcp proteins. The only outer membrane protein of the system, XcpQ, belongs to a large family of proteins, designated secretins, which participate in a variety of different transport processes. Other Xcp proteins, XcpT-X, show homology to the subunits of the retractile type IV pili. Further analogies between the type II system and the assembly of retractile pili suggest a mechanism for type II secretion, in which a pilus-like structure, composed of XcpT-X, facilitates the transport of exoproteins through the channel formed by the secretin XcpQ.

The C-terminal domain of the Pseudomonas secretin XcpQ forms oligomeric rings with pore activity

The Pseudomonas secretin XcpQ forms an oligomeric complex, which is involved in the translocation of proteins across the outer membrane via the type II secretion pathway. Pseudomonas aeruginosa produces only small amounts of this complex, 50 to 100 copies per bacterium, and overexpression is lethal to these cells. However, overexpression of Pseudomonas alcaligenes XcpQ could be achieved in the P. alcaligenes mutant strain 537. Protease protection experiments with P. alcaligenes XcpQ showed that the C-terminal domain of XcpQ, which is conserved in all the different members of the secretin family, is largely resistant to proteinase K. This protease-resistant fragment is embedded in the membrane and remains a stable complex, indicating that this domain is involved in complex formation. Both the intact and the protease-protected XcpQ complex showed a tendency to form two-dimensional crystal-like structures. Electron microscopic analysis of these structures showed that the overall oligomeric rings of the intact and of the protease-resistant complex are highly similar. The central cavity of the intact XcpQ complex contains structured mass. Both the intact and the protease-protected XcpQ complex showed pore-forming activity in planar lipid bilayers, consistent with their role as a translocation channel. However, the single-channel conductances observed were not uniform. Together, these results demonstrate that the C-terminal secretin homology domain of XcpQ is the structural domain that forms the channel through which macromolecules are being transported.

Creatine supplementation--part II: in vivo magnetic resonance spectroscopy

PURPOSE

Our purpose was to study effects of creatine (Cr) supplementation on muscle metabolites noninvasively by means of magnetic resonance spectroscopy (MRS) before and after supplementation with Cr or placebo.

METHODS

1H-MRS was used in a comprehensive, double-blind, cross-over study in 10 volunteers to measure Cr in m. tibialis anterior and m. rectus femoris at rest. PCr/ATP was observed in m. quadriceps femoris by 31P-MRS at rest and after exercise.

RESULTS

A significant increase in total Cr was observed with Cr intake in m. tibialis anterior (+9.6 +/- 1.7%, P = 0.001) and in m. rectus femoris (+18.0 +/- 1.8%, P < 0.001). PCr/ATP showed a significant increase (+23.9 +/- 2.3%, P < 0.001) in m. quadriceps femoris at rest with Cr supplementation. Post-Cr supplementation recovery rates from exercise were significantly lower (k = 0.029 s(-1), P < 0.01) compared with postplacebo consumption (k = 0.034 s(-1)) and presupplementation (k = 0.037 s(-1)). However, higher levels of PCr/ATP at rest compensate for this reduction of the recovery rate after Cr supplementation. The increase of PCr/ATP determined by 31P-MRS correlates with the increase of Cr observed by 1H-MRS (r = 0.824, P < 0.001).

CONCLUSION

Noninvasive observation of Cr and PCr after Cr supplementation shows an increase in a muscle specific manner. Higher preexercise levels of PCr/ATP at rest compensate for significantly slower recovery rates of PCr/ATP after Cr supplementation.

Creatine supplementation--part I: performance, clinical chemistry, and muscle volume

PURPOSE

Our purpose was to study the effects and side effects of creatine (Cr) supplementation on high-intensity, short-term muscle work, on biochemical parameters related to Cr metabolism in blood and urine, and on muscle volume of the lower limb muscles.

METHODS

A cycling ergometer was used in a double-blind, cross-over study on 10 well-trained male physical education students to measure physical performance with 10 repetitive ergometer sprints (6-s duration, 30-s rest) before and after supplementation (5 d, 20 g x d(-1), washout period 61 +/- 8 d, mean +/- SEM, minimum 28 d) with Cr or placebo. Before and after supplementation, blood and urine were taken and the muscle volume of the lower limb was determined by magnetic resonance imaging (MRI).

RESULTS

A significant (P << 0.05) increase in performance (+7%) at the end [4-6 s] of the later sprints (4-7 and 8-10) was observed combined with a lower production of blood lactate (-1 mmol x L(-1)) with Cr supplementation. The concentration of Cr was increased significantly in urine (P < 0.001) and serum (P = 0.005), whereas creatinine (Crn) was increased in serum (P < 0.001). Crn in urine and Crn clearance did not change significantly with Cr intake. There were no significant changes in the analyzed blood enzyme activities. A significant gain of body weight (pre-Cr 76.5 +/- 1.7 kg to 77.9 +/- 1.7 kg post-Cr) with Cr supplementation was measured, but no accompanying increase of muscle mass in a limited volume of the lower limb was observed by MRI.

CONCLUSION

Cr supplementation is effective in improving short-term performance, and the methods used show no detrimental side effects with this supplementation protocol.

Epitope tagging analysis of the outer membrane folding of the molecular usher FaeD involved in K88 fimbriae biosynthesis in Escherichia coli

To analyse the outer membrane folding of the molecular usher FaeD, tagged derivatives were prepared and their expression, tag-localisation and functioning in K88 fimbriae biosynthesis was studied. A semi-random insertion mutagenesis approach with factor Xa cleavage sites yielded six tagged FaeD derivatives. A site-directed mutagenesis approach in which c-myc epitopes were inserted yielded twenty-one different derivatives. Four tagged FaeD constructs were not expressed in the outer membrane as full-sized proteins to levels that could be detected by using immunoblotting analyses. Two of these had an insertion in the amino-terminal part of FaeD, whereas the other two had a tag inserted in the carboxyl-terminal part. The latter ones yielded stable carboxyl-terminally shortened truncates of about 70 kDa, as did other mutations in this region. Six tagged derivatives were expressed but the location of the tag with respect to the outer membrane could not be determined, possibly due to shielding. Functional analysis showed that insertion of a tag in two regions of FaeD, a central region of approximately 200 amino acid residues (a.a. 200-400) and the carboxyl-terminal region (a.a. 600-end), resulted in a defective K88 fimbriae biosynthesis. In-frame deletions in the amino-terminal region of FaeD abolished fimbriae production. The integrity of these regions is obviously essential for fimbriae biosynthesis. Based on the results and with the aid of a computer analysis programme for the prediction of outer membrane beta-strands, a folding model with 22 membrane spanning beta-strands and two periplasmioc domains has been developed.

Inactive and active mutants of rab1b are not tightly integrated into target membranes

The rab1b GTPase is localized on the ER and cis-Golgi membranes and involved in early exocytotic membrane traffic processes. To analyze the influence of rab1b conformation on specific membrane targeting processes three point mutants simulating permanently inactive or active rab1b proteins were constructed and expressed in BHK cells. To increase the expression of the growth inhibiting rab1b S22N and rab1b N121I mutants we co-expressed the Mss4 protein and observed an elevated expression of the inactive rab1b mutants. Surprisingly, only the rab1b wild-type protein shows the correct intracellular localization, and a tight membrane association. We conclude that the targeting process of rab1b depends predominantly on GDP/GTP exchange.