Predictors of long-term survival in 5,680 patients admitted to a UK major trauma centre with thoracic injuries

INTRODUCTION

The long-term outcomes of chest trauma are largely unknown. We sought to determine the predictors of in-hospital and long-term survival in patients admitted to a major trauma centre (MTC) with chest injuries and to evaluate spatial patterns of injury in our network area.

METHODS

Retrospective analysis of data collected on the National Trauma Audit Research Network (TARN) database using multivariate analysis and Cox regression analysis. Spatial analysis was performed using ArcGis 10.7.1.

RESULTS

Some 5,680 patients were admitted with chest trauma between December 1999 and December 2019. Median patient age was 45 years and the median Injury Severity Score (ISS) was 20. The proportion of patients who had an operation was 39.8%. Age, blood transfusion, head injury, shock, emergency thoracotomy and heart disease were predictors of hospital mortality (p < 0.05). However, having an operation on concomitant injuries was protective. ISS and Glasgow Coma Score were discriminators of in-hospital mortality (C-indices 0.76 and 0.80, respectively). The 10-year survival values for patients who survived to discharge from hospital and who were aged <40, 50, 60, 70, 80 and >80 years were 99%, 93%, 95%, 87%, 75% and 43%, respectively. Preadmission lung disease and alcohol/drug misuse were poor predictors of long-term survival (p < 0.05). Hotspot analysis revealed the areas with the highest incidents were all close to the MTC.

CONCLUSIONS

The MTC is geographically central to areas with high numbers of trauma incidents. Although emergency thoracotomy was a predictor of poor in-hospital outcomes, having surgery for concomitant injuries improved outcomes. Patients surviving to discharge have good long-term survivals.

Management of thoracic trauma

Managing major thoracic trauma begins with identifying and anticipating injuries associated with the mechanism of injury. The key aims are to reduce early mortality and the impact of associated complications to expedite recovery and restore the patient to their pre-injury state. While imaging is imperative to identify the extent of thoracic trauma, some pathology may require immediate treatment. The majority can be managed with adequate pleural drainage, but respiratory failure and poor gas exchange may require either non-invasive or invasive ventilation. Ventilation strategies to protect from complications such as barotrauma, volutrauma and ventilator-induced lung injury are important to consider. The management of pain is vital in reducing respiratory complications. A multimodal strategy using local, regional and systemic analgesia may mitigate respiratory side effects of opioid use. With optimal pain management, physiotherapy can be fully utilised to reduce respiratory complications and enhance early recovery. Thoracic surgeons should be consulted early for consideration of surgical management of specific injuries. With a greater understanding of the mechanisms of injury and the appropriate use of available resources, favourable outcomes can be reached in this cohort of patients. Overall, a multidisciplinary and holistic approach results in the best patient outcomes.

OA42 Evaluating the effects on a clinical service of introducing ultrasound for diagnosis of giant cell arteritis using Lean methodology

Background/Aims

In our trust, patients with suspected giant cell arteritis (GCA) were promptly started on high-dose prednisolone. However, until 2019, patients were waiting on average 28.5 days (median) for confirmation of diagnostic decision, which was mostly due to the time taken for temporal artery biopsy (TAB) to be performed and reported. We have made two major changes to our pathway: firstly (Jan 2019) adding temporal artery ultrasound (TAUS), and secondly (Mar 2020), routing GP referrals through our Primary Care Access Line (PCAL) to an allocated rheumatology registrar based at the same site as the TAUS. We used Lean methodology to pre-specify metrics to evaluate our pathway.

Aim and Purpose: To assess changes over time across our five prespecified domains: delivery, quality, service, morale and cost.

Methods

We defined lead time as median time between entry to pathway and diagnostic confirmation. This was our delivery domain. We defined treatment for GCA as clinical diagnosis plus at least 6 months of treatment with “GCA-dose” steroids. Quality was measured for patients treated as GCA as the percentage with a positive confirmatory test; and for patients not treated as GCA as the cumulative prednisolone dose received for suspected GCA. Service and morale were assessed from patient and staff feedback, respectively. Cost was assessed via the patient-level costings team using standard NHS tariffs. We plotted a run chart by month and significant shift in delivery or quality was defined as six consecutive monthly values below the baseline median.

Results

TAUS was performed a median of 2.5 days from referral. Agreement between TAB and TAUS results was good. The run chart showed a significant shift in our delivery. Lead time fell from 28.7 days to 19.2 days after introduction of ultrasound, and further down to 7.7 days after the utilisation of PCAL. A significant shift was also seen in quality metrics. Proportion of GCA with positive TAB/TAUS increased from 29% to 56.3% following the introduction of TAUS, and further to 75% on the utilisation of PCAL. The total mean prednisolone dose for patient without GCA fell from 1.335g to 0.439g after introducing TAUS, and down to 0.139g after introduction of PCAL. Within costs, average per-patient costs of TAB/TAUS declined from £1004/patient to £718/patient to £378/patient. However, total GCA pathway referrals increased from 6/month to 10/month to 24/month, increasing overall costs.

Staff and patient feedback (service, morale) were overall positive, but revealed the need for further improvements to manage the additional complexity and volume.

Conclusion

Lean methodology identified multiple metrics for evaluating the impact of TAUS and PCAL on our service. We have seen an improvement in delivery and quality. Measuring costs, morale and service helped identify unintended consequences and target further improvement.

Disclosure

T. Rajeswaran: None. A. Barr: None. V. Bassi: None. A. Chakrabarty: None. A. Cracknell: None. R. Darwood: None. S. Dass: None. S. Farrell: None. J. Hunter: None. T. Mitchell: None. J. Parvin: None. B. Sarker: None. I. Simmons: None. K. Sinclair: None. K. Smith: None. A. Sweeting: None. R. Tue: None. M. Troxler: None. R. Wakefield: None. S.L. Mackie: Consultancies; consultancy for Roche, Sanofi, AstraZeneca, Abbvie on behalf of her institution. Other; support from Roche to attend EULAR2019.

SP5.2.5 A 4-year single-centre cohort study assessing outcomes in vascular surgery patients undergoing calf fasciotomies

Aims

Acute compartment syndrome (ACS) is a surgical emergency. Delayed diagnosis and fasciotomy can result in irreversible muscle necrosis causing permanent disability and major amputation. This study compared patient outcomes following calf fasciotomies to prevent ACS (prophylactic) versus treat ACS (therapeutic) and early (within 6 hours of ACS diagnosis) versus delayed fasciotomies (beyond 6 hours) at a single vascular centre.

Methods

All patients undergoing calf fasciotomies between 1st January 2017 and 31st December 2020 were identified from a prospectively collected departmental database. Caldecott-approved data collection was conducted. The primary outcomes were wound infection, foot drop, muscle debridement, split-skin graft (SSG) requirement, vacuum dressing, 30-day amputation and death rates. Statistical analysis was performed using Fisher’s exact test.

Results

73 patients (51 men, 22 women; median age 67, IQR 56-75 years) underwent calf fasciotomies (44 therapeutic and 29 prophylactic) mainly following acute thromboembolic ischaemia. Higher complication rates occurred among delayed (15) versus early (29) fasciotomy patients: wound infection (13.3% vs 3.4%), foot drop (20.0% vs 3.4%), muscle debridement (40.0% vs 24.1%), loss of anterior compartment (13.3%, 3.4%) need for SSG (29.5% vs 17.2%), vacuum dressing (46.7% vs 20.7%) and 30-day amputation rate (20.0% vs 13.8%) but lower 30-day death rate 13.3% vs 17.2%). None of these results were statistically significant. 34.1% of delayed fasciotomies were due to awaiting emergency theatre availability.

Conclusion

ACS patients undergoing calf fasciotomies are at high risk of complications including amputation and death. Ongoing education on mortality risk and early communication with emergency theatres are critical in their management.

TP5.2.1 Duplex ultrasound should be interpreted with caution in vascular access

Aims

Dysfunctional vascular access in haemodialysis has varied clinical presentations, including prolonged bleeding, pain, loss of thrill, difficulties needling and ineffective dialysis. We aimed to establish whether specific presentations correlate with a higher frequency of adverse imaging findings and intervention.

Methods

Duplex ultrasound scans (DUS) of surgical AV fistulae and grafts performed in a teaching hospital trust between 01/07/2019 and 31/01/2020 were analysed. Referral reasons, diagnostic findings, onward imaging and interventions to salvage fistulae and grafts were cross-referenced from electronic patient databases.

Results

359 scans of AV fistulae were performed in the period studied, of which, 220 were performed on men. Median age was 63 years (IQR 49-72). The most common referral reasons were loss of thrill and difficulty needling (n = 46, both). 185/359 (52%) scans lead to subtraction angiography and 46/359 (13%) to open surgical intervention. Median time from DUS to angiography was 21 days and 21% (39/185) of DUS did not match with angiographic results. When assessing outcomes based on presentation, 16/19 (85%, p &lt; 0.01) patients who had high venous pressures on dialysis and 23/31 (74%, p &lt; 0.01) of those with dialysis recirculation required endovascular intervention. Pain on dialysis correlated poorly with future intervention (6/30).

Conclusions

A substantial proportion of DUS of dysfunctional vascular access do not correlate with subtraction angiography. Referral for DUS prior to angiography may delay intervention. Patients with objective signs of dialysis dysfunction (recirculation and high venous pressure) are highly likely to need intervention. Such cases may benefit from proceeding directly to angiography and on-table intervention.

Systematic review of interventions to increase the use of arteriovenous fistulae and grafts in incident haemodialysis patients

Background:

Patients who commence haemodialysis (HD) through arteriovenous fistulae and grafts (AVF/G) have improved survival compared to those who do so by venous lines.

Objectives:

This systematic review aims to assimilate the evidence for any strategy which increases the proportion of HD patients starting dialysis through AVF/G.

Data sources:

Medline, Embase, Cochrane Central and Scopus.

Study eligibility, participants and interventions:

English language studies comparing any educational, clinical or service organisation intervention for adult patients with end stage renal failure and reporting incident AVF/G use.

Study appraisal and synthesis:

Two reviewers assessed studies for eligibility independently. Outcome data was extracted and reported as relative risk. Reporting was performed with reference to the PRISMA statement.

Results:

Of 1272 studies, 6 were eligible for inclusion. Studies varied in design and intervention. Formal meta-analysis was not appropriate. One randomised controlled trial and two cohort studies assessed the role of a renal access coordinator. Two cohort studies assessed the implementation of qualitive initiative programmes and one cohort study assessed a national, structured education programme. Results between studies were contradictory with some reporting improvements in incident AVF/G use and some no significant difference. Quality was generally low.

Conclusions:

It is not possible to reach firm conclusions nor make strategic recommendations. A comprehensive package of care which educates and identifies patients approaching dialysis in a timely manner may improve incident AVF/G use. An unbiased, robust comparison of different strategies for timing AVF/G referral is required.

AB1174 TRACKING THE EFFECTS ON A CLINICAL SERVICE OF INTRODUCING ULTRASOUND FOR DIAGNOSIS OF GIANT CELL ARTERITIS: DESIGN OF A SERVICE EVALUATION USING LEAN METHODOLOGY

Background:

In our large, multi-site hospital, patients with suspected GCA are started promptly on high-dose prednisolone but until 2019, patients waited for temporal artery biopsy (TAB) until the GCA diagnosis could be confirmed (“GCA”) or refuted (“not-GCA”). Reports of the impact of introducing temporal and axillary artery ultrasound (TAUS) have mainly come from smaller hospitals. Agreement between TAUS and TAB has been reported by others with a Cohen’s kappa of 0.35 [1] and 0.40 [2]. We used Lean methodology to identify metrics across 5 key domains: delivery, quality, service, morale and cost.

Objectives:

To design metrics for a service evaluation to measure impact of introducing TAUS, and to test their feasibility of measurement within routine care.

Methods:

Our primary driver was time from presenting to our service to diagnostic confirmation (lead time). Pathway mapping, value stream mapping and a driver diagram identified key ideas for improvement.

We chose to measure: Delivery (mean lead time for each month), Quality (proportion of patients with GCA and positive TAB/TAUS; total (cumulative) prednisolone dose in patients with not-GCA, Service (patient feedback), Morale (staff feedback) and Cost (number of patients; cost of tests per patient; overall costs). We plotted these by month on run charts and defined a significant shift as 6 consecutive monthly values below baseline median. Cohen’s kappa was calculated using GraphPad QuickCalcs.

Results:

Routine TAUS for suspected GCA was introduced from January 2019, alongside a multidisciplinary team monthly meeting. TAUS was done a median of 2.5 days from referral. Agreement between TAB and TAUS results was good (Table 1). The run chart showed a significant shift in our Delivery (median lead time fell from 28.7 days to 21 days after introduction of ultrasound) and both Quality metrics (proportion of GCA with positive TAB/TAUS increased from 29% to 69%; total prednisolone dose for not-GCA fell from 1.335g to 0.846g).

Table 1.

Concordance between temporal and axillary artery ultrasound (TAUS) and temporal artery biopsy (TAB) in scans performed through 2019. Cohen’s weighted kappa 0.59 (including equivocal results as separate category).

TAUS positiveTAUS negativeTAUS equivocalTAB positive1411TAB negative5275TAB equivocal030

Within Costs, average per-patient costs of TAB/TAUS declined from £1004/patient to £792/patient, but total referrals for TAB/TAUS increased from 6/month to 10/month, increasing overall costs. Staff and patient feedback (Service, Morale) revealed that further improvements to the care pathway were needed to manage the additional complexity.

Conclusion:

Lean methodology identified multiple metrics for evaluating the impact of TAUS on our service. Introducing TAUS improved Delivery and Quality, but measuring Costs, Morale and Service helped identify unintended consequences. Concordance between TAUS and TAB was good. We plan to continue to improve and monitor the care pathway based on our multi-stakeholder feedback.

References:

[1]Luqmani et al., HTA 2016

[2]Mukhtyar et al., Clin Rheum 2019

Disclosure of Interests:

Sarah Mackie Grant/research support from: Roche (attendance of EULAR 2019; co-applicant on research grant), Consultant of: Sanofi, Roche/Chugai (monies paid to my institution not to me), Andrew Barr: None declared, Alison Cracknell: None declared, Shannon Farrell: None declared, Jimmy Parvin: None declared, Ajay Patil: None declared, Ian Simmons: None declared, Kate Smith Grant/research support from: Medical education grants from Sanofi and Biogen, Speakers bureau: Novartis, Andrea Sweeting: None declared, Max Troxler: None declared, Tara Webster: None declared, Richard Wakefield Speakers bureau: Novartis, Janssen, GE

The surgical application of point-of-care haemostasis and platelet function testing

Background

Disordered coagulation complicates many diseases and their treatments, often predisposing to haemorrhage. Conversely, patients with cardiovascular disease who demonstrate antiplatelet resistance may be at increased thromboembolic risk. Prompt identification of these patients facilitates optimization of haemostatic dysfunction. Point-of-care (POC) tests are performed ‘near patient’ to provide a rapid assessment of haemostasis and platelet function.

Methods

This article reviews situations in which POC tests may guide surgical practice. Their limitations and potential developments are discussed. The paper is based on a Medline and PubMed search for English language articles on POC haemostasis and platelet function testing in surgical practice.

Results

POC tests identifying perioperative bleeding tendency are already widely used in cardiovascular and hepatic surgery. They are associated with reduced blood loss and transfusion requirements. POC tests to identify thrombotic predisposition are able to determine antiplatelet resistance, predicting thromboembolic risk. So far, however, these tests remain research tools.

Conclusion

POC haemostasis testing is a growing field in surgical practice. Such testing can be correlated with improved clinical outcome.

Platelet function and antiplatelet therapy

Background

Platelets have roles other than haemostasis and many are relevant to surgical practice. This review examines both the pathophysiology of platelets in haemostasis and thrombosis, and other roles of clinical importance.

Methods

A literature review of the various functional roles of platelets was performed (Medline search, English language) including their action in inflammation (in particular in atherothrombosis), antimicrobial defence and tumour growth. Current clinical evidence for antiplatelet therapy is also reviewed.

Results and conclusion

Platelet functions are multiple, complex and not limited to haemostasis. Understanding of platelet pathophysiology continues to grow and this is relevant to many aspects of surgical practice, particularly the clinical use of antiplatelet therapy.

Ischaemic Skeletal Muscle Increases Serum Ischaemia Modified Albumin

OBJECTIVES

Ischaemia modified albumin (IMA) has been used as a marker of myocardial ischaemia but little is known about its production during ischaemia of other tissues. The clinical models of patients with intermittent claudication and major arterial surgery were used to investigate IMA production from ischaemic skeletal muscle.

DESIGN

Prospective clinical study.

MATERIALS AND METHODS

IMA was measured pre-operatively, at end ischaemia, and 5 min, 4, 24, 48, 72 and 144 h post-surgery in patients undergoing (a) revascularisation for intermittent claudication (IC, n=15), (b) abdominal aortic aneurysm repair (AAA, n=12) and controls (n=16).

RESULTS

The median pre-operative IMA concentration in IC patients was significantly higher than the AAA group (88.3 versus 83.5 U/ml, p=0.036) and controls (88.3 versus 80.3 U/ml, p=0.031). IMA concentrations increased significantly during arterial clamping in both IC and AAA groups (88.3 versus 120.0 U/ml, p=0.001; 83.5 versus 118.8 U/ml, p=0.002, respectively) consistent with increased skeletal muscle ischaemia. In contrast, there was only a mild perioperative increase in the controls (80.3 versus 91.6 U/ml, p=0.012).

CONCLUSIONS

Patients with intermittent claudication have significantly elevated IMA and skeletal muscle ischaemia during arterial surgery results in significantly increased circulating IMA. When IMA is used to detect myocardial ischaemia, ischaemic skeletal muscle must be excluded.

Altered platelet reactivity in peripheral vascular disease complicated with elevated plasma homocysteine levels

Elevated plasma concentrations of the sulphur-containing amino acid homocysteine (Hcy) is associated with increased risk of atherosclerosis and arterial thrombosis. The mechanism by which Hcy exerts these effects has yet to be fully elucidated, although a variety of possible mechanisms have been proposed, including endothelial dysfunction or haemostatic abnormalities. However, the influence of Hcy on platelets, cells central to the atherothrombotic process, has never been addressed directly in patient studies. Here, the influence of mild hyperhomocysteinaemia (hHcy) on platelet function was explored in patients with peripheral occlusive arterial disease as evidence by intermittent claudication. Claudicants (n = 39) were assigned to one of two subgroups depending on their plasma Hcy concentrations. hHcy claudicants had plasma Hcy concentrations of 18.9 +/- 1.0 microM (n = 24), compared to 11.3 +/- 0.5 microM for normohomocysteinemic (nHcy) claudicants (n = 15) and 12.6 +/- 0.7 microM for age-matched controls (n=15). Platelet function was evaluated ex vivo in both groups and compared to age-matched controls. Platelet activation and sensitivity to nitric oxide-mediated inhibition was assessed by platelet fibrinogen binding and P-selectin expression. At low concentrations of adenosine diphosphate (ADP; 0.1 microM) and thrombin (0.02 U/ml), platelets from hHcy claudicants were more reactive than those from age-matched controls, but not nHcy claudicants. Agonist-induced P-selectin expression was significantly raised in hHcy claudicants compared to all other groups. Interestingly no differences were observed between nHcy claudicants and age-matched controls, indicating that claudication per se did not affect platelet function. Since platelet activity in vivo is determined by the exposure to both agonists and antagonists, we subsequently tested the sensitivity of platelets to inhibition by nitric oxide (NO), using the same platelet markers. Platelets from hHcy claudicants were significantly less sensitive to GSNO (1-100 microM)-mediated inhibition than all other groups. GSNO (1microM) induced 42.6 +/- 10 and 39 +/- 11.5% inhibition of ADP-induced fibrinogen binding for the nHcy claudicants and age-matched controls, respectively. However, in hHcy claudicants only 16.4 +/- 9.7% inhibition was observed, significantly less than the other groups (P < 0.01). Again no differences between nHCy claudicants and controls were observed. These results suggest the presence of claudication alone does not influence platelet function but if complicated with mild hyperhomocysteinemia, the sensitivity to agonists is increased, and more importantly, their sensitivity to inhibition is greatly reduced. The overall effect would be an increased propensity for platelet activation. The presence of even mildly elevated plasma Hcy could dramatically increase thrombotic risk.

Increased nitrotyrosine production in patients undergoing abdominal aortic aneurysm repair

Background

Vascular inflammation is implicated in the pathogenesis of atherosclerosis and abdominal aortic aneurysm (AAA), and is thought to involve reactive species such as the nitric oxide-derived oxidant peroxynitrite. In the present study nitrotyrosine was measured as a stable marker of peroxynitrite production in vivo.

Methods

Perioperative blood samples were obtained from patients undergoing elective open or endovascular repair of an AAA and from patients with intermittent claudication, smoking aged-matched controls, non-smoking aged-matched controls and non-smoking young healthy controls. Plasma nitrotyrosine was measured by an enzyme-linked immunosorbent assay.

Results

The median plasma nitrotyrosine concentration in patients with an AAA (0·46 nmol nitrated bovine serum albumin equivalents per mg protein) was significantly higher than that in patients with intermittent claudication (0·35 nmol; P = 0·002), smoking controls (0·36 nmol; P = 0·001), non-smoking controls (0·35 nmol; P = 0·002) and young healthy controls (0·27 nmol; P &lt; 0·001). Nitrotyrosine concentrations increased during early reperfusion in open AAA repair, but not during endovascular repair. AAA exclusion from the circulation reduced levels to control values (P = 0·001).

Conclusion

Patients with an AAA had raised levels of circulating nitrated proteins compared with patients with claudication and controls, suggesting a greater degree of ongoing inflammation that was not related to smoking.

Penetrating atherosclerotic ulcers of the aorta

BACKGROUND

Penetrating aortic ulcers burrow into the aortic wall and can have fatal consequences. Although they were first described as long ago as 1934 they have only recently been recognized as a distinct pathological entity.

METHOD

A review of the current literature was undertaken, based primarily on an English language Medline search with secondary references obtained from key articles.

RESULTS

Penetrating aortic ulcer is principally a disease of elderly hypertensive men. It may run a benign course or may produce complications such as aortic rupture, embolization and aneurysm formation. Presentation may be identical to that of classical aortic dissection, but the distinction is important because an ulcer may be more likely to cause rupture.

CONCLUSION

Open surgical repair has been the 'gold standard' of treatment but endovascular stenting is an attractive option in this group of frail patients.

Light and electron microscopic in situ hybridization: non-radioactive labeling and detection, double hybridization, and combined hybridization-immunocytochemistry

We performed light and electron microscopic in situ hybridization, according to the same protocol and without pretreatment of sections, on Lowicryl- and LR Gold-embedded cells. Digoxigenin (DIG)- or biotin-labeled riboprobes were visualized by direct or indirect immunodetection using commercially available gold-antibody conjugates with 0.8-10-nm gold grains. At the ultrastructural level, the main findings were that DIG-labeled probes gave a slightly higher labeling intensity (grains per signal) than biotin. The direct detection method produced a more compact signal, which led to better resolution at medium and high magnifications. Labeling intensities of all gold grain sizes were essentially equal. Grain sizes of 5 nm and larger were highly preferable because available enhancement methods are unsatisfactory for ultrasmall grains. The optimized immunodetection protocols are suitable for double hybridization with two different probes and for combined hybridization and immunocytochemistry.

Intracellular localization of poliovirus RNA by in situ hybridization at the ultrastructural level using single-stranded riboprobes

Polioviral RNA was localized by electron microscopic in situ hybridization on sections of poliovirus-infected HEp-2 cells. Viral plus-strand RNA was found accumulated in the close surroundings of the membrane-bound replication complex. Two different regions of the viral genome were detected with the same frequency, which indicates the predominant presence of full-length genomic RNA. Viral proteins of the P2 and the P3 genomic region were detected mainly over the core of the replication complex, whereas the hybridization signal was present rather at the peripheral parts of the complex. A more than 100-fold excess of viral plus- over minus-strand RNA was found by strand-specific hybridization to RNA extracted from isolated replication complexes. These findings support the idea of a pool of viral plus-strand RNA set free from the replication complex and accumulating in the close vicinity of the replication complex possibly before encapsidation.

Immunocytochemical localization of capsid-related particles in subcellular fractions of poliovirus-infected cells

The structural proteins of poliovirus can assemble into a series of different configurations (capsid-related particles, CRP). Only some seem to be true capsid precursors and the role of most CRP in morphogenesis is unclear. We used electron microscopic immunocytochemistry with monoclonal antibodies recognizing different CRP [protomers, pentamers, 65S empty capsids (EC), 74S-EC, and virions] to locate CRP in subcellular fractions containing virus-induced vesicles associated with the viral replication complex. We found pentamer antigenic CRP to be associated with the replication complex. The same pentamer antigenicity was exhibited by novel, "capsid-like" structures attached to the surface of the virus-induced vesicles. Upon solubilization of the vesicular fraction, mainly 65S-EC and only negligible amounts of pentamers were found by sucrose gradient analysis and by immunoprecipitation. We show that the pentamer antigenic particles are converted into 65S-EC when their membranous support is dissolved. We propose that the vesicular membrane prevents the assembly of 65S-EC and keeps the pentamer antigenic CRP in the appropriate concentration and configuration for association with the nascent progeny RNA.

Structural and functional characterization of the poliovirus replication complex

Two populations of membrane-bound replication complexes were isolated from poliovirus-infected HEp-2 cells by sucrose gradient centrifugation. The two fractions show similar ultrastructural features: the replication complex is enclosed in a rosettelike shell of virus-induced vesicles and contains a very tightly packed second membrane system (compact membranes). The vesicular fraction, which bands in 30% sucrose, contains replicative intermediate (RI) and 36S RNA. The fraction banding in 45% sucrose contains only minute amounts of RI and contains mainly 36S RNA, two-thirds of which is encapsidated. In vitro, the two fractions show similar RNA synthesizing capacities and produce 36S plus-strand RNA. Dissolving the membranes within and around synthetically active replication complexes with sodium deoxycholate abolishes the completion of 36S RNA but still allows elongation in the RI. Our findings suggest an architecture of the replication complex that has the nascent plus strands on the RI enclosed in the compact membranes and the replication forks wrapped additionally in protein. Plus-strand RNA can be localized by in situ hybridization with a biotinylated riboprobe between the replication complex and the rosette of the virus-induced vesicles. It was found that the progeny RNA strands are set free soon after completion from the replication complex at the sites where the compact membranes within the replication complex are in close contact with the surrounding virus-induced vesicles.

Functional heterogeneity of CD4-positive T-cell subsets: the correlation between effector functions and lymphokine secretion is limited

Several effector functions and the lymphokine secretion pattern of 30 antigen-specific CD4+ T-cell clones have been investigated. The clones were generated directly by limiting dilution cloning of nylon wool-purified T-cells obtained from KLH immunized BALB/c mice and avoiding an initial bulk culture phase. Using this approach the CD4+ T-cell clones were grouped into helper and nonhelper subsets. Among the helper subset, clones which helped B-cells for specific antibody production by either cognate or noncognate recognition were identified. Some but not all of these helper clones fitted into the Th1 and Th2 scheme, if the lymphokine secretion pattern was evaluated. Among the nonhelper subset CD4+ clones which killed activated APC in a MHC class II-restricted and antigen-specific manner were identified. In addition, one clone which suppressed B-cell antibody production mediated by helper clones was found. However, neither the suppression of antibody responses nor the inability of the nonhelper clones to help B-cells is due to the killing of B-cells. Various attempts were made to convert nonhelper into helper clones and helper into killer clones, without success. Thus, the functional properties of these clones are stable traits and not convertible by varying the experimental conditions.

In situ hybridization for light and electron microscopy: a comparison of methods for the localization of viral RNA using biotinylated DNA and RNA probes

We report procedures for in situ hybridization at the light and electron microscopic level for localization of viral RNA in poliovirus-infected, Lowicryl-embedded cells. We compare specificity and signal intensity of biotinylated, double-stranded DNA and single-stranded, strand-specific RNA probes, both corresponding to the same region of the poliovirus genome. The hybrids were detected with antibiotin antibodies or streptavidin with colloidal gold as a marker. Hybridization with the RNA probe was more sensitive and gave lower background than with DNA. Detection with immunogold proved to be by far more sensitive than with streptavidin. The hybridization and detection protocols for the DNA and the RNA probes could be applied without modification to light microscopic semi-thick sections as well as to electron microscopic ultrathin sections.

Structural organization of poliovirus RNA replication is mediated by viral proteins of the P2 genomic region

Transcriptionally active replication complexes bound to smooth membrane vesicles were isolated from poliovirus-infected cells. In electron microscopic, negatively stained preparations, the replication complex appeared as an irregularly shaped, oblong structure attached to several virus-induced vesicles of a rosettelike arrangement. Electron microscopic immunocytochemistry of such preparations demonstrated that the poliovirus replication complex contains the proteins coded by the P2 genomic region (P2 proteins) in a membrane-associated form. In addition, the P2 proteins are also associated with viral RNA, and they can be cross-linked to viral RNA by UV irradiation. Guanidine hydrochloride prevented the P2 proteins from becoming membrane bound but did not change their association with viral RNA. The findings allow the conclusion that the protein 2C or 2C-containing precursor(s) is responsible for the attachment of the viral RNA to the vesicular membrane and for the spatial organization of the replication complex necessary for its proper functioning in viral transcription. A model for the structure of the viral replication complex and for the function of the 2C-containing P2 protein(s) and the vesicular membranes is proposed.

CD4+ T cell-mediated killing of MHC class II-positive antigen-presenting cells. I. Characterization of target cell recognition by in vivo or in vitro activated CD4+ killer T cells

Ag-specific as well as Ia-restricted killing of certain APC by CD4+ T cells was investigated. The CD4-mediated killing is not only a characteristic of in vitro long term cultured T cell lines or clones, but is also manifest after in vivo priming. Thus, CD4+ killer T cells are generated in vivo as well. CD4+ killer T cells are detected in the Th1, but not in the Th2 subset, and they do not appear to lyse Ia+ APC or bystander cells by a pathway mediated by secreted T cell factors. The latter observation is demonstrated by cold target inhibition experiments as well as by the failure of puromycin to inhibit killing, if applied in doses which completely block lymphokine secretion. Ia+ APC differ in their susceptibility to lysis. Transformed APC are usually better lysed than nontransformed APC. Unstimulated B cells are not killed, while LPS-stimulated B cell blasts are killed. The results of cold target inhibition and bystander killing experiments suggest that CD4+ killer T cells are activated by the common pathway, i.e., by Ag presented in the context of Ia, but killing requires the recognition of additional determinant(s) on APC. It is proposed that these killing-inducing determinants are continuously expressed on most transformed Ia+ cells and on nontransformed but stimulated APC.

CD4+ T cell-mediated killing of MHC class II-positive antigen-presenting cells. I. Characterization of target cell recognition by in vivo or in vitro activated CD4+ killer T cells

Ag-specific as well as Ia-restricted killing of certain APC by CD4+ T cells was investigated. The CD4-mediated killing is not only a characteristic of in vitro long term cultured T cell lines or clones, but is also manifest after in vivo priming. Thus, CD4+ killer T cells are generated in vivo as well. CD4+ killer T cells are detected in the Th1, but not in the Th2 subset, and they do not appear to lyse Ia+ APC or bystander cells by a pathway mediated by secreted T cell factors. The latter observation is demonstrated by cold target inhibition experiments as well as by the failure of puromycin to inhibit killing, if applied in doses which completely block lymphokine secretion. Ia+ APC differ in their susceptibility to lysis. Transformed APC are usually better lysed than nontransformed APC. Unstimulated B cells are not killed, while LPS-stimulated B cell blasts are killed. The results of cold target inhibition and bystander killing experiments suggest that CD4+ killer T cells are activated by the common pathway, i.e., by Ag presented in the context of Ia, but killing requires the recognition of additional determinant(s) on APC. It is proposed that these killing-inducing determinants are continuously expressed on most transformed Ia+ cells and on nontransformed but stimulated APC.

Functional characterization of T lymphocytes grown in semisolid agar

T lymphocyte colony forming cells (TL-CFC) grown in agar in the presence of PHA were assayed for their capacity to induce or suppress polyclonal PWM dependent B lymphocyte differentiation into plasma cells. This was measured by identifying cells containing intracytoplasmatic immunoglobulins by direct immunofluorescence. To validate the helper and suppressor system used in this paper, the inductive capacity of unfractionated T lymphocytes and their subpopulations bearing Fc-receptors for IgM (TM) and for IgG (TG) was measured. The unfractionated T cells and the TM fraction showed helper activity, whereas the TG cells expressed suppressor activity. The TL-CFC grown in agar in the presence of PHA manifested helper activity at low cell concentration. However, increasing the TL-CFC concentration finally caused suppression of B cell differentiation. The suppressor effect could be abolished by prior irradiation of the TL-CFC before seeding them in agar. These results indicate that T cells grown in agar have the functional capacity of T helper and T suppressor cells to induce and suppress polyclonal PWM dependent B lymphocyte differentiation into plasma cells.