Short-term anti-TNF therapy with surgical closure versus anti-TNF therapy in the treatment of perianal fistulas in Crohn's disease (PISA-II): a patient preference randomised trial

BACKGROUND

Guidelines on Crohn's perianal fistulas recommend anti-tumour necrosis factor (TNF) treatment and suggest considering surgical closure for patients with surgically amenable disease. However, long-term outcomes following these two strategies have not been directly compared. The aim of this study was to assess radiological healing in patients who received short-term anti-TNF treatment and surgical closure compared with those who received anti-TNF treatment alone.

METHODS

The PISA-II trial was a multicentre, patient preference study done in nine hospitals in the Netherlands and one hospital in Italy. Adult patients with Crohn's disease and an active high perianal fistula with a single internal opening were eligible for inclusion. After counselling, patients with no treatment preference were randomly assigned (1:1) using random block randomisation (block sizes of six without statification), to 4-month anti-TNF therapy and surgical closure or anti-TNF therapy for 1 year, after seton insertion. Patients with a treatment preference received their preferred therapy. The primary outcome was radiological healing assessed by MRI at 18 months, defined as a complete fibrotic tract or a MAGNIFI-CD (Magnetic Resonance Index for Fistula Imaging in Crohn's Disease) score of 0, assessed according to the intention-to-treat principle. Secondary outcomes included clinical closure, number of patients undergoing surgical reintervention and number of reinterventions, recurrences, and impact on quality of life measured by the Perianal Disease Activity Index (PDAI). Analyses were performed on an intention-to-treat basis and additionally an as-treated analysis for radiological healing and clinical closure. This study was registered at the Dutch Trial Registry, NL7625, and with EudraCT, 2018-002064-15, and is closed to accrual due to completion.

FINDINGS

Between Sept 14, 2013, and Dec 7, 2019, 94 patients were enrolled onto the trial, of whom 32 (34%) were randomly assigned and 62 (66%) chose a specific treatment. 38 (40%) patients were assigned to the surgical closure group and 56 (60%) patients to the anti-TNF group. At 18 months, radiological healing was significantly more common in the surgical closure group (12 [32%] patients) than in the anti-TNF group (five [9%] patients; p=0·005). By contrast, clinical closure was not significantly different between the two treatment groups (26 [68%] patients in the surgical closure group vs 29 [52%] patients in the anti-TNF group; p=0·076). Significantly fewer patients required a reintervention in the surgical closure group than in the anti-TNF therapy group (five [13%] patients in the surgical closure group, median one reintervention [IQR one to three] vs 24 [43%] patients in the anti-TNF group, median two reinterventions [one to two]; p=0·005). Among patients who reached clinical closure during follow-up, four (14%) of 29 in the surgical closure group and five (16%) of 31 in the anti-TNF therapy group had a recurrence, which occurred only in patients without radiological healing. PDAI was significantly lower in the surgical closure group than in the anti-TNF group after 18 months (p=0·031). Adverse events and serious adverse events were similar in both treatment groups and mostly entailed reinterventions. Ten (11%) patients had side-effects associated with anti-TNF treatment. Two serious adverse events unrelated to study treatment occurred (appendicitis and myocardial infarction). One patient died from a tongue base carcinoma, unrelated to study treatment.

INTERPRETATION

Short-term anti-TNF treatment combined with surgical closure induces long-term MRI healing more frequently than anti-TNF therapy in patients with Crohn's perianal fistulas. These data suggest that patients with Crohn's perianal fistula amenable for surgical closure should be counselled for this therapeutic approach.

FUNDING

Netherlands Organisation for Health Research and Development and Broad Medical Research Program.

Fibrosis and MAGNIFI-CD Activity Index at Magnetic Resonance Imaging to Predict Treatment Outcome in Perianal Fistulizing Crohn's Disease Patients

BACKGROUND AND AIMS

Characteristic magnetic resonance imaging [MRI] features associated with long-term perianal fistula closure are still being discussed. This study evaluated the predictive value of degree of fibrosis and disease activity (MAGNIFI-CD index) at MRI for long-term clinical closure of Crohn's perianal fistulas.

METHODS

Crohn's disease [CD] patients treated with surgical closure following anti-tumour necrosis factor [anti-TNF] induction or anti-TNF alone for high perianal fistulas as part of a patient preference randomized controlled trial [PISA-II] between 2013 and 2020 with a post-treatment MRI and long-term clinical follow-up data were retrospectively included. Two radiologists scored the degree of fibrosis and MAGNIFI-CD index at pre- and post-treatment MRI. The accuracy of post-treatment MRI findings in predicting long-term clinical closure [12 months after the MRI] was evaluated using receiver operating characteristics [ROC] analysis.

RESULTS

Fifty patients were included: 31 female, median age 33 years (interquartile range [IQR] 26-45). Fourteen patients showed a 100% fibrotic fistula at post-treatment MRI, all of which had long-term clinical closure. Median MAGNIFI-CD index at post-treatment MRI was 0 [IQR 0-5] in 25 patients with long-term clinical closure and 16 [IQR 10-20] in 25 patients without. ROC analysis showed an area under the curve of 0.90 (95% confidence interval [CI] 0.82-0.99) for degree of fibrosis and 0.95 [95% CI 0.89-1.00] for the MAGNIFI-CD index, with a Youden cut-off point of 6 [91% specificity, 87% sensitivity].

CONCLUSIONS

Degree of fibrosis and MAGNIFI-CD index at post-treatment MRI are accurate in predicting long-term clinical closure and seem valuable in follow-up of perianal CD. A completely fibrotic tract at MRI is a robust indicator for long-term fistula closure.

EUDRACT

2013-002932-25 and 2018-002064-15.

A fast and easy strategy for protein purification using "teabags"

Protein purification often involves affinity capture of proteins on stationary resin, alternatively proteins are captured on free flowing resin for subsequent separation from bulk fluid. Both methods require labour and time intensive separation of particulate matter from fluid. We present a method where affinity resin is contained within porous-walled containers, supporting clarification, product recovery, and concentration in a single step with minimal hands-on processing time, without significant investments in equipment.

Detergent organisation in crystals of monomeric outer membrane phospholipase A

The structure of the detergent in crystals of outer membrane phospholipase A (OMPLA) has been determined using neutron diffraction contrast variation. Large crystals were soaked in stabilising solutions, each containing a different H(2)O/D(2)O contrast. From the neutron diffraction at five contrasts, the 12 A resolution structure of the detergent micelle around the protein molecule was determined. The hydrophobic beta-barrel surfaces of the protein molecules are covered by rings of detergent. These detergent belts are fused to neighbouring detergent rings forming a continuous three-dimensional network throughout the crystal. The thickness of the detergent layer around the protein varies from 7-20 A. The enzyme's active site is positioned just outside the hydrophobic detergent zone and is thus in a proper location to catalyse the hydrolysis of phospholipids in a natural membrane. Although the dimerisation face of OMPLA is covered with detergent, the detergent density is weak near the exposed polar patch, suggesting that burying this patch in the enzyme's dimer interface may be energetically favourable. Furthermore, these results indicate a crucial role for detergent coalescence during crystal formation and contribute to the understanding of membrane protein crystallisation.

Structural investigations of the active-site mutant Asn156Ala of outer membrane phospholipase A: function of the Asn-His interaction in the catalytic triad

Outer membrane phospholipase A (OMPLA) from Escherichia coli is an integral-membrane enzyme with a unique His-Ser-Asn catalytic triad. In serine proteases and serine esterases usually an Asp occurs in the catalytic triad; its role has been the subject of much debate. Here the role of the uncharged asparagine in the active site of OMPLA is investigated by structural characterization of the Asn156Ala mutant. Asparagine 156 is not involved in maintaining the overall active-site configuration and does not contribute significantly to the thermal stability of OMPLA. The active-site histidine retains an active conformation in the mutant notwithstanding the loss of the hydrogen bond to the asparagine side chain. Instead, stabilization of the correct tautomeric form of the histidine can account for the observed decrease in activity of the Asn156Ala mutant.

Structural investigations of calcium binding and its role in activity and activation of outer membrane phospholipase A from Escherichia coli

Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme that catalyses the hydrolysis of phospholipids. Enzymatic activity is regulated by reversible dimerisation and calcium-binding. We have investigated the role of calcium by X-ray crystallography. In monomeric OMPLA, one calcium ion binds between two external loops (L3L4 site) at 10 A from the active site. After dimerisation, a new calcium-binding site (catalytic site) is formed at the dimer interface in the active site of each molecule at 6 A from the L3L4 calcium site. The close spacing and the difference in calcium affinity of both sites suggests that the L3L4 site may function as a storage site for a calcium ion, which relocates to the catalytic site upon dimerisation. A sequence alignment demonstrates conservation of the catalytic calcium site but evolutionary variation of the L3L4 site. The residues in the dimer interface are conserved as well, suggesting that all outer membrane phospholipases require dimerisation and calcium in the catalytic site for activity. For this family of phospholipases, we have characterised a consensus sequence motif (YTQ-X(n)-G-X(2)-H-X-SNG) that contains conserved residues involved in dimerisation and catalysis.

Bacterial phospholipase A: structure and function of an integral membrane phospholipase

Within the large family of lipolytic enzymes, phospholipases constitute a very diverse subgroup with physiological functions such as digestion and signal transduction. Most phospholipases may associate with membranes at the lipid-water interface. However, in many Gram-negative bacteria, a phospholipase is present which is located integrally in the bacterial outer membrane. This phospholipase (outer membrane phospholipase A or OMPLA) is involved in transport across the bacterial outer membrane and has been implicated in bacterial virulence. OMPLA is calcium dependent and its activity is strictly regulated by reversible dimerisation. Recently the crystal structure of this integral membrane enzyme has been elucidated. In this review, we summarise the implications of these structural data for the understanding of the function and regulation of OMPLA, and discuss a mechanism for phospholipase dependent colicin release in Escherichia coli.

Unusual catalytic triad of Escherichia coli outer membrane phospholipase A

Escherichia coli outer membrane phospholipase A (OMPLA) is an integral membrane enzyme. OMPLA is active as a homodimer and requires calcium as a cofactor. The crystal structures of the monomeric and the inhibited dimeric enzymes were recently determined [Snijder, H. J., et al. (1999) Nature 401, 717-721] and revealed that OMPLA monomers are folded into a 12-stranded antiparallel beta-barrel. The active site consists of previously identified essential residues Ser144 and His142 in an arrangement resembling the corresponding residues of a serine hydrolase catalytic triad. However, instead of an Asp or Glu that normally is present in the triad of serine hydrolases, a neutral asparagine (Asn156) was found in OMPLA. In this paper, the importance of the catalytic Asn156 is addressed by site-directed mutagenesis studies. All variants were purified at a 30 mg scale, and were shown to be properly folded using SDS-PAGE and circular dichroism spectroscopy. Using chemical cross-linking, it was shown that all variants were not affected in their calcium-dependent dimerization properties. The Asn156Asp variant exhibited a 2-fold lower activity than wild-type OMPLA at neutral pH. Interestingly, the activity of the variant is 1 order of magnitude higher than that of the wild type at pH >10. Modest residual activities (5 and 2.5%, respectively) were obtained for the Asn156Ala and Asn156Gln mutants, showing that the active site of OMPLA is more tolerant toward replacements of this third residue of the catalytic triad than other serine hydrolases, and that the serine and histidine residues are minimally required for catalysis. In the X-ray structure of dimeric OMPLA, the cofactor calcium is coordinating the putative oxyanion via two water molecules. We propose that this may lessen the importance for the asparagine in the catalytic triad of OMPLA.

Structural evidence for dimerization-regulated activation of an integral membrane phospholipase

Dimerization is a biological regulatory mechanism employed by both soluble and membrane proteins. However, there are few structural data on the factors that govern dimerization of membrane proteins. Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme which participates in secretion of colicins in Escherichia coli. In Campilobacter and Helicobacter pylori strains, OMPLA is implied in virulence. Its activity is regulated by reversible dimerization. Here we report X-ray structures of monomeric and dimeric OMPLA from E. coli. Dimer interactions occur almost exclusively in the apolar membrane-embedded parts, with two hydrogen bonds within the hydrophobic membrane area being key interactions. Dimerization results in functional oxyanion holes and substrate-binding pockets, which are absent in monomeric OMPLA. These results provide a detailed view of activation by dimerization of a membrane protein.

Quantitative 1H-NMR imaging of water in white button mushrooms (Agaricus bisporus)

MRI represents a valuable tool for studying the amount and physical status of water in plants and agricultural products, for example, mushrooms (Agaricus bisporus). Contrast in NMR images originates from the mixed influence of the fundamental NMR parameters, amongst others, spin-density, T2- and T1 relaxation processes. Maps of these parameters contain valuable anatomical and physiological information. They can, however, be severely distorted, depending on the combination of parameter settings and anatomy of the object under study. The influence of the tissue structure of mushrooms, for example, tissue density (susceptibility inhomogeneity) and cell shape on the amplitude, T2, and T1 images is analyzed. This is achieved by vacuum infiltration of the cavities in the mushroom's spongy structure with Gd-DTPA solutions and acquiring Saturation Recovery-Multispin Echo images. It is demonstrated that the intrinsic long T2 values in the cap and outer stipe tissue strongly relate to the size and geometry of the highly vacuolated cells in these spongy tissues. All observed T2 values are strongly affected by susceptibility effects. The T2 of gill tissue is shorter than T2 of the cap and outer stipe, probably because these cells are less vacuolized and smaller in size. The calculated amplitude images are not directly influenced by susceptibility inhomogeneities as long as the observed relaxation times remained sufficient long. They reflect the water distribution in mushrooms best if short echo times are applied in a multispin echo imaging sequence at low magnetic field strength.