Current state-of-the-art and gaps in platform trials: 10 things you should know, insights from EU-PEARL

Platform trials bring the promise of making clinical research more efficient and more patient centric. While their use has become more widespread, including their prominent role during the COVID-19 pandemic response, broader adoption of platform trials has been limited by the lack of experience and tools to navigate the critical upfront planning required to launch such collaborative studies. The European Union-Patient-cEntric clinicAl tRial pLatform (EU-PEARL) initiative has produced new methodologies to expand the use of platform trials with an overarching infrastructure and services embedded into Integrated Research Platforms (IRPs), in collaboration with patient representatives and through consultation with U.S. Food and Drug Administration and European Medicines Agency stakeholders. In this narrative review, we discuss the outlook for platform trials in Europe, including challenges related to infrastructure, design, adaptations, data sharing and regulation. Documents derived from the EU-PEARL project, alongside a literature search including PubMed and relevant grey literature (e.g., guidance from regulatory agencies and health technology agencies) were used as sources for a multi-stage collaborative process through which the 10 more important points based on lessons drawn from the EU-PEARL project were developed and summarised as guidance for the setup of platform trials. We conclude that early involvement of critical stakeholder such as regulatory agencies or patients are critical steps in the implementation and later acceptance of platform trials. Addressing these gaps will be critical for attaining the full potential of platform trials for patients.

Funding

Innovative Medicines Initiative 2 Joint Undertaking with support from the European Union's Horizon 2020 research and innovation programme and EFPIA.

Mobilizing the clinical trial ecosystem to drive adoption of master protocols

Master protocol studies typically use an overarching protocol to answer several questions by guiding a variety of sub-studies. These sub-studies can incorporate multiple diseases, therapies, or both. Although this innovative approach offers many benefits, including the ability to deliver clinical research that is more patient-centric and efficient, several common barriers curtail widespread adoption. The Clinical Trials Transformation Initiative (CTTI) convened industry representatives, regulatory agencies, patient groups, and academic institutions to identify emerging best practices and develop resources designed to help sponsors and other stakeholders overcome these challenges. We first identify some broad changes needed in the clinical trials ecosystem to facilitate mainstream adoption of master protocol studies, and we subsequently summarize CTTI's resources designed to support this effort.

Comparison of the platelet activation status of single-donor platelets obtained with two different cell separator technologies

BACKGROUND

The microparticle content (MP%) of apheresis platelets-a marker of platelet activation-is influenced by donor factors and by external stressors during collection and storage. This study assessed the impact of apheresis technology and other factors on the activation status (MP%) of single-donor apheresis platelets.

STUDY DESIGN AND METHODS

Data from six US hospitals that screened platelets by measuring MP% through dynamic light scattering (ThromboLUX) were retrospectively analyzed. Relative risks (RRs) were derived from univariate and multivariable regression models, with activation rate (MP% ≥15% for plasma-stored platelets; ≥10% for platelet additive solution [PAS]-stored platelets) and MP% as outcomes. Apheresis platform (Trima Accel vs Amicus), storage medium (plasma vs PAS), pathogen reduction, storage time, and testing location were used as predictors.

RESULTS

Data were obtained from 7511 platelet units collected using Trima (from 16 suppliers, all stored in plasma, 20.0% were pathogen-reduced) and 2456 collected using Amicus (from four different collection facilities of one supplier, 65.0% plasma-stored, 35.0% PAS-stored, none pathogen-reduced). Overall, 30.0% of Trima platelets were activated compared to 45.6% of Amicus platelets (P < .0001). Multivariable analysis identified apheresis platform as significantly associated with platelet activation, with a lower activation rate for Trima than Amicus (RR: 0.641, 95% confidence interval [CI]: 0.578; 0.711, P < .0001) and a 6.901% (95% CI: 5.926; 7.876, P < .0001) absolute reduction in MP%, when adjusting for the other variables.

CONCLUSION

Trima-collected platelets were significantly less likely to be activated than Amicus-collected platelets, irrespective of the storage medium, the use of pathogen reduction, storage time, and testing site.

Screening of red blood cells for extracellular vesicle content as a product quality indicator

BACKGROUND

The controversy around the quality and clinical impact of stored and differentially manufactured red cell concentrates (RCCs) from different donor groups is ongoing. Current studies are limited by the lack of quality measures suitable for routine screening of RCCs. As extracellular vesicles (EVs) are markers of cellular activation or degradation, this study investigated the utility of EV screening to characterize the effects of RBCs production methods and storage.

STUDY DESIGN AND METHODS

RCCs were prepared by whole blood filtration or red blood cell (RBC) filtration methods, centrifuged to prepare a supernatant, and tested for EV content (dynamic light scattering or tunable resistive pulse-sensing techniques), hemolysis, ATP, and RBC deformability on Days 7, 21, and 42 of storage. To simulate nondestructive quality control (QC) testing, 1 RBC unit was tested in parallel with six 10-mL aliquots that were stored in small-volume containers.

RESULTS

EV content showed a linear increase with storage time (p < 0.001) and correlated with supernatant hemoglobin and inversely with ATP or RBC deformability. The method of component manufacturing influenced the characteristics of the EVs during storage. A strong correlation between both EV testing methods' measure of total EV was observed. EV content in the six aliquots were consistent at each time point but statistically higher than in the original RCCs on and after 21 days of storage.

CONCLUSIONS

EV content correlates with measures of hemolysis and other RBC quality indicators and could be implemented as a routine screening tool for nondestructive QC testing of RCCs.

Factor VIIa administration in traumatic brain injury: an AAST-MITC propensity score analysis

BACKGROUND

Recombinant factor VIIa (rFVIIa) has been used off-label as an adjunct in the reversal of warfarin therapy and management of hemorrhage after trauma. Only a handful of these reports are rigorous studies, from which results regarding safety and effectiveness have been mixed. There remains no clear consensus as to the role of rFVIIa in traumatic brain injury (TBI).

METHODS

Eleven level 1 trauma centers provided clinical data and head CT scans of patients with a Glasgow Coma Scale (GCS) score of ≤13 and radiographic evidence of TBI. A propensity score (PS) to receive rFVIIa in those surviving ≥2 days was calculated for each patient based on patient demographics, comorbidities, physiology, Injury Severity Score, admission GCS score, and treatment center. Patients receiving rFVIIa within 24 hours of admission were matched to patients who did not receive rFVIIa for outcomes assessment. Subgroup analysis evaluated patients with primary head injury with PS matching.

RESULTS

There were 4284 patient observations; 129 received rFVIIa. Groups were comparable after matching. No differences in mortality or morbidity were found. Improvement in GCS score from admission to discharge was less among those receiving rFVIIa (5.5 vs. 2.4; P value 0.001); however, there was no difference in average GCS score at discharge. No significant differences in outcomes were identified in patients with isolated TBI receiving rFVIIa.

DISCUSSION

rFVIIa in early management of TBI is not associated with a decreased risk of mortality or morbidity, and may negatively impact recovery and functional status at discharge in the severely injured patient with polytrauma.

LEVEL OF EVIDENCE

Level III.

STUDY TYPE

Therapeutic/care management.

Routine Screening Method for Microparticles in Platelet Transfusions

Platelet inventory management based on screening microparticle content in platelet concentrates is a new quality improvement initiative for hospital blood banks. Cells fragment off microparticles (MP) when they are stressed. Blood and blood components may contain cellular fragments from a variety of cells, most notably from activated platelets. When performing their roles as innate immune cells and major players in coagulation and hemostasis, platelets change shape and generate microparticles. With dynamic light scattering (DLS)-based microparticle detection, it is possible to differentiate activated (high microparticle) from non-activated (low microparticle) platelets in transfusions, and optimize the use of this scarce blood product. Previous research suggests that providing non-activated platelets for prophylactic use in hematology-oncology patients could reduce their risk of becoming refractory and improve patient care. The goal of this screening method is to routinely differentiate activated from non-activated platelets. The method described here outlines the steps to be performed for routine platelet inventory management in a hospital blood bank: obtaining a sample from a platelet transfusion, loading the sample into the capillary for DLS measurement, performing the DLS test to identify microparticles, and using the reported microparticle content to identify activated platelets.

A practical approach to the use of prone therapy in acute respiratory distress syndrome

In this article we propose a practical approach to the use of prone therapy for acute respiratory distress syndrome (ARDS). We have attempted to provide information to improve the understanding and implementation of prone therapy based on the literature available and our own experience. We review the basic physiology behind ARDS and the theoretical mechanism by which prone therapy can be of benefit. The findings of the most significant studies regarding prone therapy in ARDS as they pertain to its implementation are summarized. Also provided is a discussion of the nuances of utilizing prone therapy, including potential pitfalls, complications, and contraindications. The specific considerations of prone therapy in open abdomens and traumatic brain injuries are discussed as well. Finally, we supply suggested protocols for the implementation of prone therapy discussing criteria for initiation and cessation of therapy as well as addressing issues such as the use of neuromuscular blockade and nutritional supplementation.

Suboptimal compliance with evidence-based guidelines in patients with traumatic brain injuries

OBJECT

Evidence-based management (EBM) guidelines for severe traumatic brain injuries (TBIs) were promulgated decades ago. However, the extent of their adoption into bedside clinical practices is not known. The purpose of this study was to measure compliance with EBM guidelines for management of severe TBI and its impact on patient outcome.

METHODS

This was a retrospective study of blunt TBI (11 Level I trauma centers, study period 2008-2009, n = 2056 patients). Inclusion criteria were an admission Glasgow Coma Scale score ≤ 8 and a CT scan showing TBI, excluding patients with nonsurvivable injuries-that is, head Abbreviated Injury Scale score of 6. The authors measured compliance with 6 nonoperative EBM processes (endotracheal intubation, resuscitation, correction of coagulopathy, intracranial pressure monitoring, maintaining cerebral perfusion pressure ≥ 50 cm H2O, and discharge to rehabilitation). Compliance rates were calculated for each center using multivariate regression to adjust for patient demographics, physiology, injury severity, and TBI severity.

RESULTS

The overall compliance rate was 73%, and there was wide variation among centers. Only 3 centers achieved a compliance rate exceeding 80%. Risk-adjusted compliance was worse than average at 2 centers, better than average at 1, and the remainder were average. Multivariate analysis showed that increased adoption of EBM was associated with a reduced mortality rate (OR 0.88; 95% CI 0.81-0.96, p < 0.005).

CONCLUSIONS

Despite widespread dissemination of EBM guidelines, patients with severe TBI continue to receive inconsistent care. Barriers to adoption of EBM need to be identified and mitigated to improve patient outcomes.

Oral ivermectin for treatment of pediculosis capitis

BACKGROUND

Pediculosis capitis is a highly transmissible infestation prevalent worldwide. It is an important public health problem mainly affecting children. The emergence of drug resistance and high rates of treatment failure with several topical agents makes ivermectin, an antiparasitic drug, an attractive therapeutic option for lice control.

OBJECTIVE

To evaluate the efficacy and safety of oral ivermectin in the treatment of a pediatric population with pediculosis capitis.

METHODS

Children with pediculosis capitis from the ages of 6 to 15 years were recruited from an indigenous community in Mexico, and were treated with a single dose of oral ivermectin at 200 μg/kg. They were treated with a second dose of ivermectin 1 week later if there was evidence of persistent infestation.

RESULTS

Forty-four children (mean age, 9.8 years) with active infestation were treated. A single approximately 200-μg/kg dose of ivermectin eradicated adult lice in all children. Forty-one percent (n = 18) required a second dose because of the presence of viable nits. At the third visit, 2 weeks after commencement of treatment there was no evidence of viable nits, and there was complete resolution of excoriations in all children and minimal or no symptoms of pruritus were reported in 93% (n = 41). There were no significant adverse effects due to ivermectin administration.

CONCLUSIONS

Ivermectin demonstrates high efficacy and tolerability in the treatment of pediculosis capitis in children. A significant number of children required a second dose to ensure complete eradication.

IL-7R alpha versus CCR7 and CD45 as markers of virus-specific CD8+ T cell differentiation: contrasting pictures in blood and tonsillar lymphoid tissue

In humans, circulating CD8(+) memory T cells to a nonpersistent virus (influenza) lie within CCR7(+)CD45RA(-) central memory, whereas memory to Epstein-Barr virus (EBV) latent, EBV lytic, and cytomegalovirus (CMV) antigens are progressively larger in size and are more biased toward CCR7(-)CD45RA(-) effector memory and CCR7(-)CD45RA(+) terminally differentiated compartments. We found that these populations are also distinguished by progressively lower expression of the interleukin-7 receptor (IL-7R alpha) and by lower IL-7 responsiveness; indeed, percentage IL-7R alpha -positive values showed a tight inverse correlation with population size. However, these relationships among size, differentiation phenotype, and IL-7R alpha status in blood did not hold in tonsillar tissue. In tonsil tissue, although EBV reactivities outnumbered their CMV and influenza counterparts, the distinct CCR7/CD45 isoform signatures of the different virus-specific populations were retained. Moreover, all detectable reactivities showed high levels of IL-7R alpha expression. As a discriminator between different virus-specific populations, IL-7R alpha therefore appears to be more susceptible to tissue location than the classical CCR7/CD45 markers.

Antithrombin for respiratory distress syndrome in preterm infants

BACKGROUND

Acquired Antithrombin (AT) deficiency is a common and prognostically important finding in sick preterm infants with respiratory distress syndrome (RDS). It has been hypothesised that AT concentrate may improve clinical outcomes in preterm infants with RDS.

OBJECTIVES

To determine whether the administration of AT concentrate decreases mortality in preterm infants with RDS compared with placebo or no treatment.

SEARCH STRATEGY

An electronic literature search in the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE in August 2006 was performed. No language restriction was applied. References from identified studies were cross-checked for possible additional studies. Experts in the field and pharmaceutical companies were contacted for unpublished data. Abstracts of the American Society of Pediatric Research and European Society of Pediatric Research meetings (1983-2005) were searched and authors of relevant studies were contacted to obtain additional information.

SELECTION CRITERIA

Randomized controlled trials comparing any dose and duration of AT therapy with placebo or no treatment in preterm infants with RDS.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data from included studies regarding mortality, intraventricular hemorrhage, mechanical ventilation, and other reported events in the clinical course of the patients. Data for similar outcomes were combined where appropriate, using a fixed-effects model in MetaView 4.2 (Update Software).

MAIN RESULTS

Two trials consisting of 182 preterm infants, fulfilled the inclusion criteria. Mean gestational age of patients included was 28 weeks. In one trial, patients had to be intubated and ventilated for RDS to be eligible for the study. In the other trial, RDS was not mentioned as an inclusion criteria, however the vast majority of infants in the study received surfactant. No individual trial showed a significant difference in mortality. One of the trials was stopped early because of an increase in deaths in the AT group. The pooled analysis for mortality within the first week of life showed a typical relative risk of 2.67 (95% CI 0.72-9.83) in favour of the control group. Only the trial that was stopped early followed the infants long enough to report neonatal mortality. This trial reported 7 deaths (11.5%) in the AT group and two deaths (3.3%) in the placebo group within 28 days of life. Secondary outcomes included days of mechanical ventilation and supplemental oxygen which were only reported in 1 trial. Both outcomes were in favour of the control group and statistically significant (p < 0.05).

AUTHORS' CONCLUSIONS

Preterm infants with RDS are unlikely to benefit from AT treatment and may be harmed.

Benefits of non invasive ventilation

Mechanical ventilation of the newborn infant has increased neonatal survival. However, this increased survival has come at the expense of increased morbidity, in the form of bronchopulmonary dysplasia, and at the cost of an expensive technology. Continuous positive airway pressure (CPAP) is accepted as conferring clinical benefit in supporting the recently extubated preterm infant and in the management of apnea of prematurity. Attention is now being drawn to physiologic and clinical evidence to support CPAP use, with or without early surfactant, as a primary treatment of hyaline membrane disease. The purpose of this review is to explore these proposed benefits of non invasive ventilation and place them in the context of current clinical evidence.

Factors influencing time from presentation to treatment of colorectal and breast cancer in urban and rural areas

Stage at diagnosis and survival from cancer vary according to where people live, suggesting some may have delays in diagnosis. The aim of this study was to determine if time from presentation to treatment was longer for colorectal and breast cancer patients living further from cancer centres, and identify other important factors in delay. Data were collected on 1097 patients with breast and 1223 with colorectal cancer in north and northeast Scotland. Women with breast cancer who lived further from cancer centres were treated more quickly than those living closer to cancer centres (P=0.011). Multilevel modelling found that this was largely due to them receiving earlier treatment at hospitals other than cancer centres. Breast lump, change in skin contour, lymphadenopathy, more symptoms and signs, and increasing age predicted faster treatment. Screen detected cancers and private referrals were treated more quickly. For colorectal cancer, time to treatment was similar for people in rural and urban areas. Quicker treatment was associated with palpable rectal or abdominal masses, tenesmus, abdominal pain, frequent GP consultations, age between 50 and 74 years, tumours of the transverse colon, and iron medication at presentation. Delay was associated with past anxiety or depression. There was variation between general practices and treatment appeared quicker at practices with more female general practitioners.

Factors influencing time from presentation to treatment of colorectal and breast cancer in urban and rural areas

Stage at diagnosis and survival from cancer vary according to where people live, suggesting some may have delays in diagnosis. The aim of this study was to determine if time from presentation to treatment was longer for colorectal and breast cancer patients living further from cancer centres, and identify other important factors in delay. Data were collected on 1097 patients with breast and 1223 with colorectal cancer in north and northeast Scotland. Women with breast cancer who lived further from cancer centres were treated more quickly than those living closer to cancer centres (P=0.011). Multilevel modelling found that this was largely due to them receiving earlier treatment at hospitals other than cancer centres. Breast lump, change in skin contour, lymphadenopathy, more symptoms and signs, and increasing age predicted faster treatment. Screen detected cancers and private referrals were treated more quickly. For colorectal cancer, time to treatment was similar for people in rural and urban areas. Quicker treatment was associated with palpable rectal or abdominal masses, tenesmus, abdominal pain, frequent GP consultations, age between 50 and 74 years, tumours of the transverse colon, and iron medication at presentation. Delay was associated with past anxiety or depression. There was variation between general practices and treatment appeared quicker at practices with more female general practitioners.

Kakadumycins, novel antibiotics from Streptomyces sp NRRL 30566, an endophyte of Grevillea pteridifolia

An endophytic streptomycete (NRRL 30566) is described and partially characterized from a fern-leaved grevillea (Grevillea pteridifolia) tree growing in the Northern Territory of Australia. This endophytic streptomycete produces, in culture, novel antibiotics - the kakadumycins. Methods are outlined for the production and chemical characterization of kakadumycin A and related compounds. This antibiotic is structurally related to a quinoxaline antibiotic, echinomycin. Each contains, by virtue of their amino acid compositions, alanine, serine and an unknown amino acid. Other biological, spectral and chromatographic differences between these two compounds occur and are given. Kakadumycin A has wide spectrum antibiotic activity, especially against Gram-positive bacteria, and it generally displays better bioactivity than echinomycin. For instance, against Bacillus anthracis strains, kakadumycin A has minimum inhibitory concentrations of 0.2-0.3 microg x ml(-1) in contrast to echinomycin at 1.0-1.2 microg x ml(-1). Both echinomycin and kakadumycin A have impressive activity against the malarial parasite Plasmodium falciparum with LD(50)s in the range of 7-10 ng x ml(-1). In macromolecular synthesis assays both kakadumycin A and echinomycin have similar effects on the inhibition of RNA synthesis. It appears that the endophytic Streptomyces sp. offer some promise for the discovery of novel antibiotics with pharmacological potential.

A psychoanalytic view of Biblical myth

The author looks at some ways in which certain biblical myths tell a story, a story about loss--loss of freedom, of the homeland, of God's favour, ultimately loss of the good object--and about guilt for these losses. He describes in the post-exilic myth of the Old Testament and the Jesus myth of the New Testament a pattern in which, he argues, there is a 'retreat' from the depressive anxieties that seem to be troubling the group, with loss and guilt becoming mediated through a rigidified defensive organisation that holds out the promise that it will make this loss and guilt easier to bear. Guilt, worthlessness, badness and fallibility are split off and projected into a near foreign group blamed for loss, while within the group's own boundary there is an identification with righteousness and power. The author describes the post-exilic myth and the Jesus myth as what he terms 'hardened myths' that embody a belief in an idealized privileged identity in which exclusive group possession of the good object is asserted. The analysis of such hardened myths reveals a shared belief in the efficacy of group idealization. The author links the formation of these hardened myths with what we know about how individuals manage actual loss, and argues that (for the group as for the individual) the myths express collusion with the moral authority of an idealized and very punitive superego. The paper ends with a very brief suggestion that, analogously, hardened myths may be relevant in other cultural and social millieux, especially, perhaps, the troubled relations of some psychoanalytic groups to one another.

Educational opportunities in palliative care: what do general practitioners want?

It is important to support general practitioners (GPs) in maintaining and developing their palliative care skills as most of the final year of a patient's life is spent at home under the care of the primary health care team. The training needs and uptake of GPs have been explored, but little is known about how GP educational preferences vary. The aim of this study was to explore the current educational preferences of GPs in different geographical locations as part of an evaluation of an educational intervention. The methods used included postal questionnaires sent to 1061 GPs. Results from 640 (60%) of GPs revealed that half (51%) wanted education in symptom control for non-cancer patients. More inner-city GPs wanted education in opiate prescribing (43%), controlling nausea and vomiting (45%), and using a syringe driver (38%) than their urban and rural colleagues (26%, 29% and 21%, respectively). Increased educational preference and increased difficulty in accessing information was associated with reduced confidence in symptom control. To maximize educational uptake it will be important for educational strategies to be developed and targeted according to variations in demand, and in particular to respond to the need for palliative care education in symptom control for patients suffering from advanced non-malignant disease.

Methylation of a CpG island within the promoter region of the KAI1 metastasis suppressor gene is not responsible for down-regulation of KAI1 expression in invasive cancers or cancer cell lines

The molecular basis for downregulation of the KAI1 metastasis suppressor gene in invasive and metastatic human cancers is unknown. We have used bisulphite methylation analysis of DNA from paraffin-embedded invasive bladder tumour samples and from bladder cancer cell lines to determine if hypermethylation of a CpG island within the KAI1 promoter is responsible for this effect. Representative invasive tumour cell lines were also exposed to 5-aza-2-deoxycytidine. We found no evidence for hypermethylation of the CpG island and suggest that mechanisms other than promoter hypermethylation are responsible for reduced KAI1 expression in invasive bladder tumours and tumour cell lines.

Quality control and optimized procedure of hybridization capture-PCR for the identification of Mycobacterium avium subsp. paratuberculosis in faeces

Nucleic acid sequence capture techniques are used to improve both the sensitivity and specificity of PCR for the diagnosis of plant, animal and human diseases. Hybridization capture-PCR (HC-PCR) was first reported as a method for the detection of Mycobacterium avium subsp. paratuberculosis in 1995 and was successfully trialed on a small number of faecal samples from cattle with Johne's disease. A locally optimized HC-PCR method was evaluated on faeces from infected and non-infected animals. However, sample to sample cross contamination during the DNA purification step highlighted that the original format of the test was unsuitable for routine diagnostic use. Here, we report modifications and optimization of HC-PCR, particularly with respect to DNA purification from faeces, hybridization and capture steps. We also identified procedurally sensitive critical points in the test during capture and washing of magnetic beads. Southern blotting was omitted from the protocol to preserve specificity but this resulted in analytical sensitivity of 5000 organisms per 200 mg faecal sample. Nevertheless, HC-PCR detected M.paratuberculosis in pellets from infected sheep diluted at rates of up to 1 in 100 in normal faeces, suggesting that the technique should be evaluated further for low-cost diagnosis in flocks/herds using pooled samples.

Providing palliative care in primary care: how satisfied are GPs and district nurses with current out-of-hours arrangements?

The complex needs of palliative care patients require an informed, expert, and swift response from out-of-hours general medical services, particularly if hospital admission is to be avoided. Few general practitioners (GPs) reported routinely handing over information on their palliative care patients, particularly to GP co-operatives. District nurses and inner-city GPs were least satisfied with aspects of out-of-hours care. Most responders wanted 24-hour availability of specialist palliative care. This indicates a need to develop and evaluate out-of-hours palliative care procedures and protocols, particularly for GP co-operatives, and to improve inter-agency collaboration.

IS900 PCR to detect Mycobacterium paratuberculosis in retail supplies of whole pasteurized cows' milk in England and Wales

IS900 PCR for Mycobacterium paratuberculosis was applied to cream, whey, and pellet fractions of centrifuged whole cows' milk. The test and simultaneous control reactions gave correct results for spiked milk and for native milk samples obtained directly from M. paratuberculosis-free, subclinically infected, and clinically infected cows. The test was then applied to units of whole pasteurized cows' milk widely obtained from retail outlets throughout central and southern England from September 1991 to March 1993. With peak periods in January to March and in September to November, when up to 25% of units were affected, an overall 22 of 312 samples (7%) tested positive for M. paratuberculosis. In 18 of the 22 positive samples (81%), the PCR signal segregated to the cream or pellet fractions or both, consistent with the presence of intact mycobacteria. Nine of 18 PCR-positive milk samples (50%) and 6 of 36 PCR-negative milk samples (16%) yielded long-term liquid cultures which tested positive for M. paratuberculosis after 13 to 40 months of incubation, despite overgrowth by other organisms. Taken together with data on the prevalence of M. paratuberculosis infection in herds in the United Kingdom, the known secretion of M. paratuberculosis in milk from subclinically infected animals, and the inability of laboratory conditions simulating pasteurization to ensure the killing of all these slowly growing or unculturable organisms, there is a high risk, particularly at peak times, that residual M. paratuberculosis will be present in retail pasteurized cows' milk in England.

Engineering proteins without primary sequence tryptophan residues: mutant trp repressors with aliphatic substitutions for tryptophan side chains

Combinatorial mismatch-primer mutagenesis was used to make simultaneous changes of codons for residues Trp19 and Trp99 of the Escherichia coli trp aporepressor (TrpR protein) to codons for other residues. Among 21 different single- and double-mutant repressors obtained from this round of mutagenesis, proteins with Trp-->Leu and Trp-->Met changes at one or both positions were found to be nearly as active as the wild type (wt). Genes encoding repressors with each of the eight possible combinations of single- and double-mutant changes of Trp19 and Trp99 to Leu and Met were constructed by recombination in vitro. Whereas three of these eight mutant repressors are unstable in E. coli, all are made at similar steady-state levels in Salmonella typhimurium. Three of the eight mutant holorepressors are lethal when overproduced in S. typhimurium, because they confer an induced auxotrophy. Two different activity assays in vivo show that one of the four double-mutant repressors (Trp19-->Leu; Trp99-->Met) is similar to wt TrpR in its interactions with both Trp and DNA. These results show that more general approaches to engineering active proteins with fewer Trp residues may give rise to functional mutants without aromatic substitutions, and that aliphatic changes should be considered in cases where engineered changes of Trp to Phe or Tyr do not work.

Gestational trophoblastic disease - experience of the sheffield (United-kingdom) supraregional screening and treatment service

Abstract. The gestational trophoblastic diseases (GTD) are uncommon complications of pregnancy. The UK GTD registration scheme offers specialist facilities for screening and treatment. In Sheffield about 5% of all patients monitored require chemotherapy. The successful treatment - almost 100% cure - of these patients is a testament to the success of the registration scheme and undoubtedly this is one of the most cost efficient of all specialist medical treatments currently available.

Planned sexual behaviour of young Australian visitors to Thailand

OBJECTIVE

To research the knowledge of AIDS and other sexually transmitted diseases among young Australian tourists to Thailand, and their intended sexual behaviour.

DESIGN AND SETTING

A cross-sectional survey by anonymous, self-administered questionnaire, of persons seeking pre-travel medical advice in private clinics in five Australian cities.

PARTICIPANTS

213 consecutive patients travelling to Thailand without a spouse or partner.

RESULTS

Only 34% of the sample reported a definite intention not to have sex in Thailand. Regarding choice of potential partners: 24.5% more men than women said they would have sex with a Thai national; 13.7% of men said they would have sex with a "bar girl"; and 21.7% more women than men said they would choose a fellow Australian traveller. Eighty-two per cent of the sample reported that they would use condoms 100% of the time, and there was no significant difference between the number of men and women who expressed this intention.

CONCLUSIONS

Although not obviously "sex tourists", many young Australian travellers are likely to have sex while visiting Thailand. These data have important implications for education and prevention programs to control the spread of human immunodeficiency virus (HIV) and other sexually transmitted diseases.

Immunosuppressive properties of sera and urine dialysates from kidney-graft recipients treated with azathioprine, prednisolone, and niridazole

Niridazole, an antischistosomal agent, was given to renal transplant recipients in addition to azathioprine and prednisolone, as there is experimental evidence that this combination of drugs is highly immunosuppressive. Sera obtained from kidney-graft recipients during the first two weeks after transplantation were examined for their ability to inhibit the one-way mixed lymphocyte reaction (MLR). Sera from seven patients receiving azathioprine, prednisolone, and niridazole (triple-drug treatment), five patients receiving azathioprine and prednisolone, and two other patients treated with niridazole alone for schistosomiasis produced MLR inhibition by comparison with pretreatment (control) sera.A mean of 78% inhibition was observed with sera taken after one day's treatment with the three-drug combination, whereas this level of in-vitro immunosuppression occurred only after eight days of treatment with azathioprine and prednisolone. Niridazole alone produced an effect similar to azathioprine and prednisolone. Concentrated dialysate of urine from a patient receiving triple-drug treatment not only inhibited the MLR but also significantly prolonged the survival of heterotopic heart allografts in rats, whereas dialysate from the same patient after niridazole had been stopped gave less MLR inhibition and failed to prolong heart allograft survival.Since niridazole thus increased the in-vitro and in-vivo immunosuppressive action of azathioprine and prednisolone, we suggest that this triple-drug combination might be useful for preventing early acute kidney graft rejection.

Niridazole as an immunosuppressive agent

The immunosuppressive properties of niridazole, an antihelminthic drug, have been investigated in rats. When given orally at a dosage of 50 mg/kg it extended the median survival of cardiac allografts from 7 to 20 days. The immunosuppressive effect was not increased by giving either azathioprine or prednisolone concurrently, but when all three drugs were combined the immunosuppression was profound, and only 2 of 8 grafts were rejected. Drug combinations incorporating niridazole at a lower dosage or for a shorter period were less effective, and azathioprine and prednisolone on their own or together prolonged graft survival only marginally in this model.

Dipole moments, Kerr constants and other properties of acetoacetic ester and acetylacetone

The proportions of the keto and en01 isomers of ethyl acetoacetateand of acetylacetone incyclohexane, carbon tetrachloride and benzene have been determined by n.m.r. spectroscopy, and expressed as functions of the solute concentrations. Routine methods sufficed for all other observations, except those of electric birefringence, which needed to be examined by a pulsed-voltage technique. The dipole moments and molar Kerr constants so obtained are analysed to provide corresponding data for the separate tautomers. Possible conformations of these keto and en01 molecules can be inferred from considerations involving known bond polarities and anisotropic polarizabilities.

Prolonged allograft survival with niridazole, azathioprine, and prednisolone

The immunosuppressive properties of niridazole, an antihelminthic drug, have been investigated in rats. When given orally in a dose of 50 mg/kg, it extended the median survival of cardiac allografts from 7 to 20 days. The immunosuppressive effect was not increased by giving either azathioprine or prednisolone concurrently but when all three drugs were combined, immunosuppression was profound and only two of eight grafts were rejected. Drug combinations incorporating niridazole at a lower dosage or for a shorter period were less effective, and azathioprine and prednisolone on their own or used together prolonged graft survival only marginally in this model. It is concluded that niridazole is a powerful immunosuppressive drug in this species and a synergistic effect can be obtained by using it in combination with azathioprine and prednisolone.

Human immunity to rat antigens. II. Immune responses in dialysis patients

The immune status of 35 patients with renal failure was studied shortly after they had commenced treatment by chronic haemodialysis to see if a group with poor immunological responses could be identified. Of 27 patients who were unimmunised to start with, only two developed lymphocytoxic antibodies after a year of treatment. The routine immunological tests that were carried out on these patients failed to predict which of them would develop antibodies, and the values that were obtained for the group of cytotoxic negative patients were no different from those obtained for the two patients who became immunised and six others who had previously rejected a kidney transplant. By using a new test that measured cellular immunity to rat antigens, eight patients could be identified as "poor responders." These individuals had in addition failed to develop cytotoxic antibodies during dialysis, had serum IgG levels that were significantly lower than normal, and were uniformly unresponsive to purified protein derivative. This group of patients might be a favoruable one to transplant.

Human immunity to rat antigens

A test has been devised with the object of assaying immune responsiveness in normal and immunodepressed persons. It has been based on the graft-versus-host model of Ford et al. (Transplantation 10: 258, 1970) and employs rat antigens as the immunological stimuli. Peripheral blood lymphocytes were injected into the hind feet of young Wistar rats, and 7 days later the popliteal lymph nodes were removed and weighed. It was found that the unwanted host-versus-graft activity could be suppressed in the rats by total body irradiation. Inactivated lymphocytes were injected into the right hind foot as a control and the result was expressed as a ratio: weight of left node to weight of right node. Lymphocytes from 45 healthy individuals were examined in this way. The response was readily suppressed by administering daily injections of steroid or antilymphocyte globulin to the rats, but was not influenced by the presence or absence of antirat antibodies in these individuals.