Impacts of fast production of afucosylated antibodies and Fc mutants in ExpiCHO-S™ for enhancing FcγRIIIa binding and NK cell activation

This study has employed mammalian transient expression systems to generate afucosylated antibodies and antibody Fc mutants for rapid candidate screening in discovery and early development. While chemical treatment with the fucose analogue 2-fluoro-peracetyl-fucose during transient expression only partially produced antibodies with afucosylated N-glycans, the genetic inactivation of the FUT8 gene in ExpiCHO-S™ by CRISPR/Cas9 enabled the transient production of fully afucosylated antibodies. Human IgG₁ and murine IgG_2a generated by the ExpiCHOfut8KO cell line possessed a 8-to-11-fold enhanced FcγRIIIa binding activity in comparison with those produced by ExpiCHO-S™. The Fc mutant S239D/S298A/I332E produced by ExpiCHO-S™ had an approximate 2-fold higher FcγRIIIa affinity than that of the afucosylated wildtype molecule, although it displayed significantly lower thermal-stability. When the Fc mutant was produced in the ExpiCHOfut8KO cell line, the resulting afucosylated Fc mutant antibody had an additional approximate 6-fold increase in FcγRIIIa binding affinity. This synergistic effect between afucosylation and the Fc mutations was further verified by a natural killer (NK) cell activation assay. Together, these results have not only established an efficient large-scale transient CHO system for rapid production of afucosylated antibodies, but also confirmed a cooperative impact between afucosylation and Fc mutations on FcγRIIIa binding and NK cell activation.

Comparing leukocyte-rich platelet-rich plasma injection with surgical intervention for the management of refractory tennis elbow. A prospective randomised trial

BACKGROUND

Patients with ongoing symptoms after non-operative treatment of lateral epicondylosis are usually treated with surgical release. Platelet-rich plasma injection is an alternative treatment option. This study aims to determine whether there is a difference in outcome from platelet-rich plasma injection or surgical release for refractory tennis elbow.

METHOD

Eighty-one patients with a diagnosis of tennis elbow for a minimum of six months, treated with previous steroid injection and a minimum visual analogue scale pain score of 50/100 were randomised to open surgery release (41 patients) or leucocyte rich platelet-rich plasma (L-PRP) (40 patients). Patients completed the Patient-Rated Tennis Elbow Evaluation and Disability of the Arm Shoulder and Hand at baseline, 1.5, 3, 6 and 12 months post-intervention. The primary endpoint was change in Patient-Rated Tennis Elbow Evaluation pain score at 12 months.

RESULTS

Fifty-two patients completed final follow-up. Functional and pain scores improved in both groups. No differences in functional improvements were found but greater improvements in Patient-Rated Tennis Elbow Evaluation pain scores were seen after surgery. Thirteen patients crossed over from platelet-rich plasma to surgery within 12 months, and one surgical patient underwent a platelet-rich plasma injection.

CONCLUSION

L-PRP and surgery produce equivalent functional outcome but surgery may result in lower pain scores at 12 months. Seventy per cent of patients treated with platelet-rich plasma avoided surgical intervention.

Double-lumen tracheal tubes and bougies: a bench study to investigate factors that influence the risk of shearing

Tracheal intubation with a double-lumen tube can be more challenging than with a single-lumen tube. A bougie can be used to facilitate intubation. Case reports have described fragment shearing from bougies when they are removed from the tube after intubation. These fragments have the potential to cause harm. It has even been suggested that bougies and double-lumen tubes should not be used together. We conducted a benchtop trial to investigate factors that influence the risk of shearing. We investigated three brands of double-lumen tube (each in three sizes and both lateralities) and four brands of bougie. We simulated one intubation and 29 further insertions/removals of bougie with every bougie-double-lumen tube combination. We inspected the inside of the tube for evidence of shearing after first, tenth and thirtieth removals. We found that brand of bougie, brand of double-lumen tube and size of double-lumen tube (but not its laterality) all influenced the degree of shearing. Certain bougie-double-lumen tube combinations produced a particularly high degree of shearing, so these should be avoided.

Early migration of a partially cemented fluted glenoid component inserted using a cannulated preparation system

Aims

Radiostereometric analysis (RSA) allows an extremely accurate measurement of early micromotion of components following arthroplasty.

Patients and Methods

In this study, RSA was used to measure the migration of 11 partially cemented fluted pegged glenoid components in patients with osteoarthritis who underwent total shoulder arthroplasty using an improved surgical technique (seven men, four women, mean age 68). Patients were evaluated clinically using the American Shoulder and Elbow Surgeons (ASES) and Constant-Murley scores and by CT scans two years post-operatively.

Results

There were two patterns of migration, the first showing little, if any, migration and the second showing rotation by > 6° as early as three months post-operatively. At two years, these two groups could be confirmed on CT scans, one with osseointegration around the central peg, and the second with cystic changes. Patients with osteolysis around the central peg were those with early migration and those with osseointegration had minimal early migration. Both groups,however,had similar clinical results.

Conclusion

Rapid early migration associated with focal lucency and absence of osseointegration was observed in three of 11 glenoid components, suggesting that lack of initial stability leads to early movement and failure of osseointegration. Cite this article: Bone Joint J 2017;99-B:674–9.

Medium-term outcomes of the Universal-2 total wrist arthroplasty in patients with rheumatoid arthritis

AIMS

The aims of this study were to evaluate the clinical and radiological outcomes of the Universal-2 total wrist arthroplasty (TWA) in patients with rheumatoid arthritis.

PATIENTS AND METHODS

This was a retrospective review of all 95 Universal-2 TWAs which were performed in our institution between 2003 to 2012 in patients with rheumatoid arthritis. A total of six patients were lost to follow-up and two died of unrelated causes. A total of ten patients had bilateral procedures. Accordingly, 75 patients (85 TWAs) were included in the study. There were 59 women and 16 men with a mean age of 59 years (26 to 86). The mean follow-up was 53 months (24 to 120). Clinical assessment involved recording pain on a visual analogue score, range of movement, grip strength, the Quick Disabilities of the Arm, Shoulder and Hand (DASH) and Wrightington wrist scores. Any adverse effects were documented with particular emphasis on residual pain, limitation of movement, infection, dislocation and the need for revision surgery. Radiographic assessment was performed pre-operatively and at three, six and 12 months post-operatively, and annually thereafter. Arthroplasties were assessed for distal row intercarpal fusion and loosening. Radiolucent zones around the components were documented according to a system developed at our institution.

RESULTS

The mean worst pain was 8.1 (3 to 10) pre-operatively and 5.4 (0 to 10) at latest follow-up (p < 0.001). Movements were preserved with mean dorsiflexion of 29^o (0 ^o to 70 ^o) and palmar flexion of 21^o (0^o to 50^o). The mean grip strength was 4.8 kg (1.7 to 11.5) pre-operatively and 10 kg (0 to 28) at final follow-up (p < 0.001). The mean QuickDASH and Wrightington wrist scores improved from 61 (16 to 91) to 46 (0 to 89) and 7.9 (1.8 to 10) to 5.7 (0 to 7.8) (p < 0.001). A total of six patients (7%) had major complications; three required revision arthroplasty and three an arthrodesis. The Kaplan-Meier probability of survival using removal of the components as the endpoint was 91% at 7.8 years (95% confidence interval 84 to 91).

CONCLUSION

The Universal-2 TWA is recommended for use in patients with rheumatoid arthritis. Cite this article: Bone Joint J 2016;98-B:1642-7.

MatOrtho proximal interphalangeal joint arthroplasty: minimum 2-year follow-up

The MatOrtho proximal interphalangeal replacement is a cementless cobalt-chromium metal-on-polyethylene mobile-bearing surface replacement arthroplasty. The aim of this study is to report the outcome and complications of this implant at a minimum of 2 years follow-up from a single institution. A retrospective case review was performed on all MatOrtho proximal interphalangeal joint replacements performed with a minimum of 2 years follow-up. Patient demographics, diagnosis, implant revision and other surgical interventions were recorded. Subjective and objective outcomes were evaluated at latest follow-up, including pain scores, range of motion, function and radiographic assessment. A total of 109 implants were inserted in 56 patients. Nine implants (six patients) were lost to follow-up. Of the remaining 100 implants, 75 had been undertaken in females. The mean age at time of surgery was 64 years and the principal diagnosis was osteoarthritis in 74%. The mean follow-up was 47 months (range 24-77). Within the group there was a statistically significant diminution in pain. There was also an improvement in functional scores post-operatively. Improvement in range of motion was seen in those joints with a pre-operative range of motion greater than 20°. Radiologically there was no evidence of loosening or of implant subsidence at final follow-up. The revision rate was 13%. Nine joints were revised to the NeuFlex (silicone rubber) prosthesis, three were converted to an arthrodesis and one had exchange of the MatOrtho prosthesis. The survival of the MatOrtho proximal interphalangeal joint arthroplasty was 85% at a minimum of 2-years follow-up. Patients can be advised that the procedure achieves good pain relief, improvement in functional scores and may improve range of motion. We would, however, caution against this implant's use in joints that are either stiff or have significant deformity and/or instability pre-operatively.

Muscle regeneration following repair of the rotator cuff

Aims

The aim of this study was to analyse human muscle tissue before and after rotator cuff repair to look for evidence of regeneration, and to characterise the changes seen in the type of muscle fibre.

Patients and Methods

Patients were assessed pre-operatively and one year post-operatively using the Oxford Shoulder Score (OSS) and MRI. The cross-sectional area and distribution of the type of muscle fibre were assessed on biopsies, which were taken at surgery and one year post-operatively. Paired samples from eight patients were analysed. There were three men and five women with a mean age of 63 years (50 to 73).

Results

All but one patient showed improvement in OSS (p = 0.004). The mean increase in the cross-sectional area of the muscle was 1220 μm2 (-801 to 3712; p = 0.03). There was a reduction of type 2a fibres (p = 0.02). A clear relationship could not be seen between the MRI findings and the histological appearances.

Conclusion

This is the first study to provide evidence that atrophy of the supraspinatus muscle is reversible. Changes in the types of fibre are discussed. MRI assessment of muscle atrophy may not be fully representative of myofibre atrophy. Cite this article: Bone Joint J 2016;98-B:1389–94.

Distributed expertise: qualitative study of a British network of multidisciplinary teams supporting parents of children with chronic kidney disease

BACKGROUND

Long-term childhood conditions are often managed by hospital-based multidisciplinary teams (MDTs) of professionals with discipline specific expertise of a condition, in partnership with parents. However, little evidence exists on professional-parent interactions in this context. An exploration of professionals' accounts of the way they individually and collectively teach parents to manage their child's clinical care at home is, therefore, important for meeting parents' needs, informing policy and educating novice professionals. Using chronic kidney disease as an exemplar this paper reports on one aspect of a study of interactions between professionals and parents in a network of 12 children's kidney units in Britain.

METHODS

We conducted semi-structured, qualitative interviews with a convenience sample of 112 professionals (clinical-psychologists, dietitians, doctors, nurses, pharmacists, play-workers, therapists and social workers), exploring accounts of their parent-educative activity. We analysed data using framework and the concept of distributed expertise.

RESULTS

Four themes emerged that related to the way expertise was distributed within and across teams: (i) recognizing each other's' expertise, (ii) sharing expertise within the MDT, (iii) language interpretation, and (iv) acting as brokers. Two different professional identifications were also seen to co-exist within MDTs, with participants using the term 'we' both as the intra-professional 'we' (relating to the professional identity) when describing expertise within a disciplinary group (for example: 'As dietitians we aim to give tailored advice to optimize children's growth'), and the inter-professional 'we' (a 'team-identification'), when discussing expertise within the team (for example: 'We work as a team and make sure we're all happy with every aspect of their training before they go home').

CONCLUSIONS

This study highlights the dual identifications implicit in 'being professional' in this context (to the team and to one's profession) as well as the unique role that each member of a team contributes to children's care. Our methodology and results have the potential to be transferred to teams managing other conditions.

Radiostereographic analysis of a shoulder surface replacement: does hydroxyapatite have a place?

Resurfacing of the humeral head is commonly used within the UK to treat osteoarthritis (OA) of the shoulder. We present the results of a small prospective randomised study of this procedure using the Global CAP prosthesis with two different coatings, Porocoat and DuoFix hydroxyapatite (HA). We followed two groups of ten patients with OA of the shoulder for two years after insertion of the prosthesis with tantalum marker beads, recording pain, Constant-Murley and American Shoulder and Elbow Surgeons (ASES) outcome scores, and using radiostereometric analysis to assess migration. The outcomes were similar to those of other series, with significant reductions in pain (p = 0.003) and an improvement in the Constant (p = 0.001) and ASES scores (p = 0.006). The mean migration of the prosthesis three months post-operatively was 0.78 mm (0.51 to 1.69) and 0.72 mm (0.33 to 1.45) for the Porocoat and DuoFix groups, respectively. Analysis of variance indicated that the rate of migration reached a plateau after three months post-operatively in both groups. At follow-up of two years the mean migration was 1 mm (sd 1 (0.25 to 3.32)); in the Porocoat group and 0.8 mm (sd 0.4 (0.27 to 1.45)) in the DuoFix HA group. Significant migration of the prosthesis was seen in one patient who had received an anterior humeral bone graft. This prosthesis was later revised after 2.7 years. The addition of a coating of HA to the sintered surface does not improve fixation of this prosthesis.

Boosting enrolment in clinical trials: validation of a regional network model

BACKGROUND

Clinical trials of stroke therapy have been hampered by slow rates of enrolment.

PURPOSE

Our purpose is to validate a previously developed model for accelerating enrolment in clinical trials by replicating it at new locations. The model employs coordinators who travel from a host institution to enrol participants from a network of participating hospitals. Active surveillance assures identification of all eligible patients.

METHODS

Among 70 U.S. investigators participating in National Institutes of Health-funded trial of stroke prevention, five investigators were invited to develop local identification and outreach networks (LIONs). Each LION comprised a LION coordinating centre servicing multiple hospitals. Hospitals provided names of patients with stroke or transient ischaemic attack to researchers at the LION coordinating centre who initiated contact; patients were offered home visits for consent and randomization. Outcomes were feasibility, enrolment, data quality, and cost.

RESULTS

Five LIONs varied in size from two to eight hospitals. All 24 hospitals we approached agreed to participate. The average monthly rate of enrolment at the research sites increased from 1.4 participants to 3.5 after expanding from a single institution model to the LION format (mean change = 2.1, range 0.9-3.7). Monthly performance improved over time. Data quality was similar for LIONs and non-LION sites, except for drug adherence which was lower at LIONs. The average cost to randomize and follow one participant during the study interval was 2.4 times the cost under the per-patient, cost-reimbursement strategy at non-LION sites. The cost ratio declined from 3.4 in year one to 1.8 in year two.

LIMITATIONS

The LION strategy requires unprecedented collaboration and trust among institutions. Applicability beyond stroke requires confirmation.

CONCLUSION

LIONs are a practical, reproducible method to increase enrolment in trial research. Twelve months were required for the average site to reach its potential. The per-participant cost at LIONs was higher than conventional sites but declined over time.

The outcome of wrist surgery: what factors are important and how should they be reported?

A prospective longitudinal study was carried out on a cohort of 86 patients who had undergone surgery for diverse wrist conditions. Disabilities of Arm Shoulder and Hand questionnaire, a pain assessment, a wrist functional score, range of movement and grip strength measures were completed. The Mayo Clinic wrist score was also calculated. The World Health Organization International Classification of Function was used as a framework for analysis. The responsiveness of each outcome measure was calculated in terms of distribution- and anchor-based methods. Pain was the most important factor in determining outcome. Changes in objective measures were less important. The responsiveness of the various measures was similar except for the Mayo Clinic wrist score, which was less responsive than the others. Patient-completed measures currently in use are multidimensional. Classifying the content according to the International Classification of Function would clarify the effects of wrist surgery on the different aspects of health.

Early results of the Acclaim elbow replacement

The Acclaim total elbow replacement is a modular system which allows implantation in both unlinked and linked modes. The results of the use of this implant in primary total elbow replacement in 36 patients, operated on between July 2000 and August 2002, are presented at a mean follow-up of 36 months (24 to 49). Only one patient did not have good relief of pain, but all had improved movement and function.

No implant showed clinical or radiological loosening, although one had a lucent area in three of seven humeral zones. The short-term results of the Acclaim total elbow replacement are encouraging. However, 11 patients (30.5%) suffered an intra-operative fracture of the humeral condyle. This did not affect the outcome, or the requirement for further surgery, except in one case where the fracture failed to unite. This problem has hopefully been addressed by redesigning the humeral resection guide. Other complications included three cases of ulnar neuropathy (8.3%) and one of deep infection (2.8%).

The results of arthroplasty in osteoarthritis of the shoulder

We have undertaken a prospective clinical and radiological analysis of 124 shoulder arthroplasties (113 patients) carried out for osteoarthritis. The clinical results showed improvement in the absolute Constant score and the American Shoulder and Elbow Surgeons score of 22 and 43, respectively. Both were statistically significant (p < 0.001). There was no significant difference in the scores after hemiarthroplasty and total arthroplasty in those patients with an intact rotator cuff. When revision was used as the end-point for survival at ten years, survival of 86%, or 90% if glenoid components made of Hylamer sterilised in air were omitted, was obtained in primary osteoarthritis. The most common cause for revision in the hemiarthroplasty group was glenoid pain at a mean of 1.5 years; in the total arthroplasty group it was loosening of the glenoid at a mean of 4.5 years. Analysis of pre-operative factors showed that the risk of gross loosening of the glenoid increased threefold when there was evidence of erosion of the glenoid at operation. Shoulder arthroplasty should not be delayed once symptomatic osteoarthritis has been established and should be undertaken before failure of the cuff or erosion of the glenoid are present.

Non-invasive assessment of intracranial compliance using a new 2-D "transit time" vs "frequency centroid" map

The objective of this research was to develop a new static two dimensional graphic display indicating changes to intracranial compliance using non invasive ultrasonic Doppler measurements of the Middle Cerebral Artery (MCA) velocity and Arterial Blood Pressure (ABP). ABP and MCA velocity were measured in a volunteer patient study and the results for hypo-, normo- and hyper-capnia, conditions were recorded. Cross-correlation analysis between ABP and MCA velocity predicted a change in "transit time" between the two parameters and a Fourier Transform analysis of the MCA velocity data predicted a change in "frequency centroid" over the 0 to 10 Hz range indicating change with intracranial compliance. The results for the hyper-capnia condition were: "Transit Time"--0 ms, "Frequency Centroid"--1.9 Hz, for the normo-capnia condition: "Transit Time"--18 ms, "Frequency Centroid"--2.5 Hz, for the hypo-capnia condition: "Transit Time"--38 ms, "Frequency Centroid"--3.1 Hz. Plotting the results on a graph with "Frequency Centroid" as the vertical axis and "Transit Time" as the horizontal axis yields a locus possibly indicating a change to intracranial compliance.

Nitrous oxide analgesia during intra-articular injection for juvenile idiopathic arthritis

AIMS

To evaluate the efficacy and safety of nitrous oxide-oxygen for children with juvenile idiopathic arthritis (JIA) undergoing intra-articular corticosteroid injection.

METHODS

A total of 55 consecutive patients with JIA undergoing intra-articular corticosteroid injection, using self administered nitrous oxide-oxygen for analgesia were studied. Patient, nurse, and parent pain scores were compared using a 0-10 cm visual analogue scale (VAS) immediately after the procedure.

RESULTS

A total of 70 joints were injected in 55 patients (median age 13.54 years). The median pain score for patient, nurse, and parent was 1 (0-10 cm VAS). The mean rank patient score was 2.12, which was greater than the nurse score (1.97), which was greater than the parent score (1.91). These differences were significant. There were no serious adverse events in any patient.

CONCLUSIONS

Nitrous oxide-oxygen provides safe and effective analgesia for intra-articular injection in children. In some cases, nurses and parents underestimated pain related to the procedure compared to the child.

Doppler sonography for the assessment of central mandibular blood flow

In this study we evaluated the role of Doppler sonography in the assessment of central mandibular blood flow. We assessed the characteristics of blood flow in the mental artery, the larger terminal branch of the inferior alveolar artery, in 30 healthy volunteers equally distributed in the age groups 20-39, 40-59 and over 60 years. We used a DWL Multi-Dop X4(R) Doppler sonography machine (DWL GmbH) with an 8 MHz probe applied intraorally. The variables analysed were patency, time averaged maximum velocity (TAMV), pulsatility index (PI), discomfort and the duration of the procedure. All the arteries analysed were patent. The TAMV and PI decreased as age increased and there were significant differences between the age groups: TAMV (P = 0.01), PI (P = 0.006). Pair-wise comparisons also showed significant differences (P< 0.05) between the 20-39 and the over 60 age group, 40-59 and the over 60 age group for TAMV, and between the 20-39 and over 60 age group for PI. The difference in measurements between the right and left sides in individual patients was not significant. The assessment took about 20 minutes and caused little discomfort. The technique is simple and could potentially be used to influence clinical decisions.

Cloning, sequencing, expression, and insertional inactivation of the gene for the large subunit of the coenzyme B12-dependent isobutyryl-CoA mutase from Streptomyces cinnamonensis

Purification of the coenzyme B12-dependent isobutyryl-CoA mutase (ICM) from Streptomyces cinnamonensis gave a protein of approximately 65 kDa by SDS-polyacrylamide gel electrophoresis, whose gene icmA was cloned using sequences derived from tryptic peptide fragments. The gene encodes a protein of 566 residues (62, 487 Da), with 43-44% sequence identity to the large subunit of methylmalonyl-CoA mutase (MCM) from S. cinnamonensis and Propionibacterium shermanii. Targeted disruption of the icmA gene yielded an S. cinnamonensis mutant devoid of ICM activity. The IcmA protein is approximately 160 residues shorter than the large subunit of the bacterial MCMs, corresponding to a loss of the entire C-terminal coenzyme B12 binding domain. The sequence of the (beta/alpha)8-barrel comprising residues A1-A400 in P. shermanii MCM is highly conserved in IcmA. The protein was produced in Streptomyces lividans and Escherichia coli with an N-terminal His6 tag (His6-IcmA), but after purification His6-IcmA showed no ICM activity. In the presence of coenzyme B12, protein from S. lividans and S. cinnamonensis of approximately 17 kDa by SDS-polyacrylamide gel electrophoresis could be selectively eluted with His6-IcmA from a Ni2+ affinity column. After purification, this small subunit showed no ICM activity but gave active enzyme when recombined with coenzyme B12 and IcmA or His6-IcmA.

Neutralizing epitopes on the extracellular interferon gamma receptor (IFNgammaR) alpha-chain characterized by homolog scanning mutagenesis and X-ray crystal structure of the A6 fab-IFNgammaR1-108 complex

The extracellular interferon gamma receptor alpha-chain comprises two immunoglobulin-like domains, each with fibronectin type-III topology, which are responsible for binding interferon gamma at the cell surface. The epitopes on the human receptor recognized by three neutralizing antibodies, A6, gammaR38 and gammaR99, have been mapped by homolog scanning mutagenesis. In this way, a loop connecting beta-strands C and C' in the N-terminal domain was identified as a key component of the epitopes bound by A6 and gammaR38, whereas gammaR99 binds to the C-terminal domain in a region including strands A and B and part of the large C'E loop. The epitope for A6 was confirmed in a crystal structure of a complex between a recombinant N-terminal receptor domain and the Fab fragment from A6, determined by X-ray diffraction to 2.8 A resolution. The antibody-antigen interface buries 1662 A2 of protein surface, including 22 antibody residues from five complementarity determining regions, primarily through interactions with the CC' surface loop of the receptor. The floor of the antigen binding cavity is formed mainly by residues from CDR L3 and CDR H3 while a surrounding ridge is formed by residues from all other CDRs except L2. Many potential polar interactions, as well as 13 aromatic side-chains, four in VL, six in VH and three in the receptor, are situated at the interface. The surface of the receptor contacted by A6 overlaps to a large extent with that contacted by interferon-gamma, in the ligand-receptor complex. However, the conformation of this epitope is very different in the two complexes, demonstrating that conformational mobility in a surface loop on this cytokine receptor permits steric and electrostatic complementarity to two quite differently shaped binding sites.

Cloning, sequencing, overexpression in Escherichia coli, and inactivation of the valine dehydrogenase gene in the polyether antibiotic producer Streptomyces cinnamonensis

The catabolism of branched chain amino acids, especially valine, appears to play an important role in furnishing building blocks for macrolide antibiotic biosynthesis. To determine for the first time the importance of valine dehydrogenase (vdh) in polyether antibiotic biosynthesis, the vdh gene from Streptomyces cinnamonensis has been cloned and sequenced. The enzyme (M(r)37,718 Da) has been produced in large amounts in an active form in the E. coli cytoplasm using a T7 RNA-polymerase expression system. Upon inactivation of the gene in S. cinnamonensis by a double-crossover mechanism, a hyg::vdh mutant was isolated that was devoid of vdh activity. Upon growth in chemically defined media, as well as a complex medium optimised for monensin production, the mutant and wild-type grew equally well and reached the same levels of monensin production. In both strains a valine transaminase activity could be detected that provides an alternative route for converting valine into 2-oxoisovaleric acid. The results show that vdh is not essential for normal growth of S. cinnamonensis, and its inactivation does not significantly affect normal levels of monensin production in this strain.

Production and characterization of anti-human interferon gamma receptor antibody fragments that inhibit cytokine binding to the receptor

Three single-chain antibody fragments that recognize the extracellular human interferon gamma receptor alpha-chain (IFN gamma R), and inhibit the binding of human IFN gamma, have been produced in Escherichia coli. These fragments are derived from murine anti-receptor monoclonal antibodies, and comprise the variable heavy (VH) domain linked to the variable light (VL) chain through a 15 amino acid linker [(GGGGS)3]. Using surface plasmon resonance technology (BIAcore), the soluble proteins were shown to retain a high affinity for recombinant IFN gamma R, and by radioimmunoassay to possess a high inhibitory activity towards IFN gamma-binding to human Raji cells. The antibody fragments most likely recognize epitopes that overlap the cytokine binding site on the receptor surface. Attempts to dissect further the antibodies to isolated VH- and VL-chains and to synthetic linear and cyclic peptides derived from the individual complementarity determining regions failed to afford fragments with significant IFN gamma R binding affinity. Nevertheless, these native-like variable region fragments and petidomimetics derived from them are of interest in the design of novel IFN gamma R antagonists.

Variable region cDNA sequences and characterization of murine anti-human interferon gamma receptor monoclonal antibodies that inhibit receptor binding by interferon gamma

Murine monoclonal antibodies (mAbs) are described that recognize the extracellular human interferon gamma receptor alpha-chain (IFN gamma R) and inhibit the binding to it of interferon gamma. The inhibitory activities (IC50s) of these mAbs, quantified by radioimmunoassay using native receptor on human Raji cells, lie in the range 0.5-24 nM, whereas their relative affinities for the immobilised recombinant extracellular receptor, determined using surface plasmon resonance technology, are in the range 0.6-40.9 nM. Nine mAbs derived from one immunization, were shown by variable region cDNA sequencing to be clonally related, with mAb A6 from this group showing the highest affinity for the receptor. Another two mAbs, gamma R38 and gamma R99, derived from a separate immunization, are clonally unrelated to each other and to those in the A6 family. From the V-region sequences, the L-chains of mAbs A6, gamma R38 and gamma R99 were shown to belong to the V kappa 34C, V kappa 34C and V kappa 1 families, whereas the H-chains belong to the 3069, J606 and J558 families, respectively. The mAbs A6 and gamma R38 recognize overlapping epitopes on the N-terminal Ig-like domain of the IFN gamma R, whereas the gamma R99 epitope is located largely in the membrane proximal Ig-like domain. Sequence comparisons with Ig structures solved by X-ray diffraction allowed deductions concerning likely CDR canonical conformations. These studies provide essential information for crystallographic and mutagenesis experiments aimed at understanding the molecular basis of the interactions of these mAbs with the extracellular IFN gamma R.

Mutagenesis of immunoglobulin-like domains from the extracellular human interferon-gamma receptor alpha chain and their recognition by neutralizing antibodies monitored by surface plasmon resonance technology

The extracellular portion of the human interferon-gamma receptor (IFN-gamma R) is predicted to adopt two Ig-like domains each with Ig superfamily type C2 topology. Surface plasmon resonance technology has been used here to compare the equilibrium and kinetic constants for binding reactions between these and several mutant domains, and neutralising anti-IFN-gamma R monoclonal antibodies. The biosensor measurements provide a sensitive method for monitoring the effects of mutations on the functional epitopes recognized by the neutralising antibodies. Thus, using recombinant native-like proteins made in E. coli, the ten N-terminal residues of the receptor were found not to be essential for domain folding, nor for recognition by the antibodies A6, D2 and gamma R38. In a similar way, residues in the interdomain region were found to play an important functional role in the epitope recognized by the antibody gamma R99.

Dissection of the extracellular human interferon gamma receptor alpha-chain into two immunoglobulin-like domains. Production in an Escherichia coli thioredoxin gene fusion expression system and recognition by neutralizing antibodies

The extracellular interferon gamma receptor alpha-chain (IFN gamma R) is believed to comprise two discrete approximately 110 amino acid immunoglobulin-like domains, perhaps similar to those seen in the crystal structure of the extracellular human growth hormone receptor [De Vos, A. M., Ultsch, M., & Kossiakoff, A. (1992) Science 255, 306-312], a distant relative in the cytokine receptor superfamily. In accord with this idea, we show that these IFN gamma R immunoglobulin-like domains can be produced separately in a soluble form with a native-like fold. The N-terminal domain (residues 1-108), with a Cys105 to Ser105 mutation, was produced at a high level, in a soluble form, as a thioredoxin-interferon gamma receptor fragment fusion protein in the cytoplasm of Escherichia coli. Upon extraction, the receptor Cys60-Cys68 disulfide bond formed spontaneously, to generate a native-like structure directly without the need for refolding. Cleavage of the fusion protein by enterokinase released the receptor fragment (approximately 12 kDa), which was recognized by several neutralizing antibodies with affinities, measured using surface plasmon resonance technology, that were essentially indistinguishable from those seen with the full length extracellular IFN gamma R produced in eukaryotic cells. Circular dichroism and 1D 1H nuclear magnetic resonance spectra indicated that the receptor fragment adopts a folded state, with mainly beta-sheet and reverse turn secondary structure. The second membrane-proximal Ig-like domain of the IFN gamma R (residues 90-229) was produced, albeit less efficiently, and characterized in a similar way. The production of these two independently folded proteins provides experimental support for the two domain organization of the IFN gamma R and opens new avenues for structural studies on these Ig-like molecules by NMR and crystallographic methods.

Cloning, sequencing, and expression of the gene encoding methylmalonyl-coenzyme A mutase from Streptomyces cinnamonensis

In streptomycetes, the conversion of succinyl-coenzyme A (CoA) into methylmalonyl-CoA, catalyzed by methylmalonyl-CoA mutase, most likely represents an important source of building blocks for polyketide antibiotic biosynthesis. In this work, the structural gene for methylmalonyl-CoA mutase from Streptomyces cinnamonensis was cloned by using a heterologous gene probe encoding the mutase from Propionibacterium shermanii. A 5,732-bp fragment was sequenced, within which four open reading frames were identified on one DNA strand. The two largest (mutA and mutB) overlap by 1 nucleotide and encode proteins of 616 and 733 residues showing high amino acid sequence similarities to each other and to methylmalonyl-CoA mutases from P. shermanii and mammalian sources. The transcriptional start of the mutA-mutB message, determined by S1 mapping, coincides with the first nucleotide of the translational start codon. Evidence that these two open reading frames encode a functional mutase in S. cinnamonensis was obtained by subcloning and expression in Streptomyces lividans TK64. The mutA and mutB gene products were detected in Western blots (immunoblots) with mutase-specific antibodies and by direct detection of mutase activity with a newly developed assay method. The methylmalonyl-CoA mutase was unable to catalyze the conversion of isobutyryl-CoA into n-butyryl-CoA, another closely related adenosylcobalamin-dependent rearrangement known to occur in S. cinnamonensis.

Characterisation of actI-homologous DNA encoding polyketide synthase genes from the monensin producer Streptomyces cinnamonensis

Cloned DNA encoding polyketide synthase (PKS) genes from one Streptomyces species was previously shown to serve as a useful hybridisation probe for the isolation of other PKS gene clusters from the same or different species. In this work, the actI and actIII genes, encoding components of the actinorhodin PKS of Streptomyces coelicolor, were used to identify and clone a region of homologous DNA from the monensin-producing organism S. cinnamonensis. A 4799 bp fragment containing the S. cinnamonensis act-homologous DNA was sequenced. Five open reading frames (ORFs 1-5) were identified on one strand of this DNA. The five ORFs show high sequence similarities to ORFs that were previously identified in the granaticin, actinorhodin, tetracenomycin and whiE PKS gene clusters. This allowed the assignment of the following putative functions to these five ORFS: a heterodimeric beta-ketoacyl synthase (ORF1 and ORF2), an acyl carrier protein (ORF3), a beta-ketoacyl reductase (ORF5), and a bifunctional cyclase/dehydrase (ORF4). The ORFs are encoded in the order ORF1-ORF2-ORF3-ORF5-ORF4, and ORFs-1 and -2 show evidence for translational coupling. This act-homologous region therefore appears to encode a PKS gene cluster. A gene disruption experiment using the vector pGM160, and other evidence, suggests that this cluster is not essential for monensin biosynthesis but rather is involved in the biosynthesis of a cryptic aromatic polyketide in S. cinnamonensis. An efficient plasmid transformation system for S. cinnamonensis has been established, using the multicopy plasmids pWOR120 and pWOR125.

Chromosomal deletion and rearrangement in Streptomyces glaucescens

The Streptomyces glaucescens genome frequently undergoes gross genomic rearrangement events which result in the deletion of extremely large segments of chromosomal DNA. The structure and origin of the DNA forming the novel junctions arising from five of these deletion events are described. Only one junction proved to be the result of a relatively simple event; the remainder were more complex, with one involving DNA which originated from at least five distinct loci. In three of the investigated cases, DNA sequences present in the junctions appeared to have resulted from the duplication of previously unique sequences, suggesting that duplication of chromosomal segments may be an important factor in genetic instability. The nucleotide sequences surrounding these junctions and their respective wild-type termini were determined.

Extremely large chromosomal deletions are intimately involved in genetic instability and genomic rearrangements in Streptomyces glaucescens

Genetic instability in Streptomyces glaucescens characteristically involves the occurrence of gross genomic rearrangements including high-level sequence amplification and extensive deletion. We investigated the relationship of the unstable melC and strS loci and a 100 kb region of the chromosome which frequently gives rise to intense heterogeneous DNA amplification. Standard chromosome walking using a cosmid bank in conjunction with a "reverse-blot" procedure enabled us to construct a contiguous genomic BamHI map of the unstable region exceeding 900 kb. The unstable genes and the amplifiable region (AUD locus) are physically linked within a 600 kb segment of the chromosome. The previously characterized deletions which affect these loci are merely components of much larger deletions ranging from 270 to over 800 kb which are polar in nature, effecting the sequential loss of the strS and melC loci. The more extensive deletions terminate either adjacent to, or in the vicinity of DNA reiterations at the AUD locus. Additionally, a deletion junction fragment and the corresponding deletion ends were cloned and analysed at the sequence level.

Heterogeneous genomic amplification in Streptomyces glaucescens: structure, location and junction sequence analysis

Certain chromosomal markers in Streptomyces glaucescens behave unstably, being lost at high frequency as a result of extensive genomic deletion. Additionally, mutant strains possessing such deletions frequently display intense DNA amplification. With the help of a wild-type cosmid library we investigated the structure of the amplified DNA sequences (ADS) and the corresponding wild-type amplifiable units of DNA (AUD). The reiterations were heterogeneous in location, copy number and sequences involved and originated predominantly from a single 100 kb region of the chromosome called the AUD locus. All strains bearing reiterations possessed associated deletions which terminated either close to or at the ADS. The termini of four AUDs were sequenced in order to gain more knowledge about these heterogeneous amplifications. In three of the four cases investigated small, interrupted homologies were found bordering the AUDs. With the help of orthogonal-field-alternation gel electrophoresis (OFAGE) we were able to visualize a tandem reiteration of more than 1,500 kb in length.

Post-prandial changes in PH and electrolyte concentration, in the upper jejunum after truncal vagotomy and drainage in man

The changes in pH and concentration of electrolytes in the jejunal lumen after a hypertonic fluid meal have been studied after truncal vagotomy and drainage, with and without diarrhoea. The results show that, in these respects, there are no specific changes in the jejunal content associated with post-vagotomy diarrhoea, but that these measurements are markedly affected by the completeness of vagotomy, as judged by the insulin test.

Postprandial osmotic and fluid changes in the upper jejunum after truncal vagotomy and drainage in man

The changes in osmotic pressure and the degree of marked dilution in the jejunal lumen after a hypertonic meal, have been studied in patients after truncal vagotomy and drainage, with and without diarrhoea, using an intraluminal intubation technique. The results suggest that neither the emptying of a hyperosmotic load from the stomach, nor its subsequent dilution in the jejunum have an important role in post-vagotomy diarrhoea.