The Minimisation of Cardiovascular Disease Screening for Kidney Transplant Candidates

Background: There is increasing evidence that cardiac screening prior to kidney transplantation does not improve its outcomes. However, risk aversion to perioperative events means that, in practice, testing remains common, limiting the availability of 'real-world' data to support any change. Our objective was to assess perioperative and 1-year post-transplant cardiovascular events in a kidney transplant candidate cohort who received minimal cardiovascular screening. Methods: The retrospective cohort study included all adult kidney-only transplant recipients in a single UK region between January 2015 and December 2021. Kidney transplant recipients asymptomatic of cardiac disease, even those with established risk factors, did not receive cardiac stress testing. The perioperative and 1-year post-transplant cardiovascular event incidences were examined. Logistic regression was used to identify variables of statistical significance that predicted cardiovascular or cerebrovascular events. Results: A total of 895 recipients fulfilled the inclusion criteria. Prior to transplantation, 209 (23%) recipients had an established cardiac diagnosis, and 193 (22%) individuals had a diagnosis of diabetes. A total of 18 (2%) patients had a perioperative event, and there was a 5.7% incidence of cardiovascular events 1 year post-transplantation. The cardiovascular mortality rate was 0.0% perioperatively, 0.2% at 3 months post-transplant, and 0.2% at 1 year post-transplant. Conclusions: This study demonstrates comparable rates of cardiovascular events despite reduced screening in asymptomatic recipients. It included higher risk individuals who may, on the basis of screening results, have been excluded from transplantation in other programmes. It provides further evidence that extensive cardiac screening prior to kidney transplantation is unlikely to be offset by reduced rates of cardiovascular events.

Management of an aneurysmal arteriovenous fistula in kidney transplant recipients

Aneurysms remain the most common complication of an arteriovenous fistula created for dialysis access. The management of an aneurysmal arteriovenous fistula (AAVF) in kidney transplant recipients remains contentious with a lack of clear clinical guidelines. Recipients of a functioning graft do not require the fistula for dialysis access, however risk of graft failure and needing the access at a future date must be considered. In this review we outline the current evidence in the assessment and management of a transplant recipient with an AAVF. We will describe our recommended five-step approach to assessing an AAVF in transplant patients; 1.) Define AAVF 2.) Risk assess AAVF 3.) Assess transplant graft function and future graft failure risk 4.) Consider future renal replacement therapy options 5.) Vascular mapping to assess future vascular access options. Then we will describe the current therapeutic options and when they would most appropriately be employed.

Proteomic analysis investigating kidney transplantation outcomes- a scoping review

BACKGROUND

Kidney transplantation is the optimal treatment option for most patients with end-stage kidney disease given the significantly lower morbidity and mortality rates compared to remaining on dialysis. Rejection and graft failure remain common in transplant recipients with limited improvement in long-term transplant outcomes despite therapeutic advances. There is an unmet need in the development of non-invasive biomarkers that specifically monitor graft function and predict transplant pathologies that affect outcomes. Despite the potential of proteomic investigatory approaches, up to now, no candidate biomarkers of sufficient sensitivity or specificity have translated into clinical use. The aim of this review was to collate and summarise protein findings and protein pathways implicated in the literature to date, and potentially flag putative biomarkers worth validating in independent patient cohorts.

METHODS

This review followed the Joanna Briggs' Institute Methodology for a scoping review. MedlineALL, Embase, Web of Science Core Collection, Scopus and Google Scholar databases were searched from inception until December 2022. Abstract and full text review were undertaken independently by two reviewers. Data was collated using a pre-designed data extraction tool.

RESULTS

One hundred one articles met the inclusion criteria. The majority were single-centre retrospective studies of small sample size. Mass spectrometry was the most used technique to evaluate differentially expressed proteins between diagnostic groups and studies identified various candidate biomarkers such as immune or structural proteins.

DISCUSSION

Putative immune or structural protein candidate biomarkers have been identified using proteomic techniques in multiple sample types including urine, serum and fluid used to perfuse donor kidneys. The most consistent findings implicated proteins associated with tubular dysfunction and immunological regulatory pathways such as leukocyte trafficking. However, clinical translation and adoption of candidate biomarkers is limited, and these will require comprehensive evaluation in larger prospective, multicentre trials.

Patient education interventions for adolescent and young adult kidney transplant recipients- a scoping review

BACKGROUND

Adolescence and young adulthood are high risk periods for kidney transplant recipients. The reasons for this are complex; but are predominantly thought to be due to poor adherence to immunosuppressive medications. Patient education can help support young recipients to reduce their risk of behaviour-related transplant loss. The aim of this review was to understand what is known about education interventions targeted at adolescent and young adult kidney transplant recipients.

METHODS

Systematic scoping review methodology was utilised. Six online databases were searched for suitable articles. Articles were selected for full text review following title and abstract screening. Articles deemed eligible to be included in the review had data extracted, which were qualitatively analysed using thematic analysis. Findings were validated through a consultation exercise with both young recipients and healthcare professionals.

RESULTS

29 studies were eligible for inclusion in the review. There was a high level of heterogeneity in the content, mode, design, and measurement of efficacy of interventions in the selected studies. Traditional face-to-face education and transition clinics were the most common educational interventions. Using technology to enhance patient education was also a major theme identified. Few studies reported using educational theory or involving patients in intervention design.

DISCUSSION

Four key research gaps were identified. 1.) Lack of educational theory in intervention design 2.) Lack of patient/ stakeholder involvement 3.) Identifying best way to measure efficacy 4.) identifying novel future research questions within already well established paediatric and educational frameworks. Addressing these gaps in future research will help inform best-practice in this vulnerable population.

A Service Reconfiguration Bundle for Expanding Access to Peritoneal Dialysis Including for Older Frailer Patients

INTRODUCTION

Rates of peritoneal dialysis (PD) have been traditionally low in Northern Ireland. With rising numbers of patients reaching end-stage kidney disease, PD is a more cost-effective treatment than haemodialysis and aligns with international goals to increase home-based dialysis options. The aim of our study was to highlight how a service reconfiguration bundle expanded access to PD in Northern Ireland.

METHODS

The service reconfiguration bundle consisted of the appointment of a surgical lead, a dedicated interventional radiologist for fluoroscopically guided PD catheter insertion, and a nephrology-led ultrasound-guided PD catheter insertion service in an area of particular need. All patients in Northern Ireland who had a PD catheter inserted in the year following service reconfigurations were included and prospectively followed up for one-year. Patient demographics, PD catheter insertion technique, setting of procedure, and outcome data were summarised.

RESULTS

The number of patients receiving PD catheter insertion doubled to 66 in the year following service reconfigurations. The range of approaches to PD catheter insertion (laparoscopic n = 41, percutaneous n = 24 and open n = 1) allowed a wide range of patients to benefit from PD. Six patients had emergency PD catheter insertion, with four receiving urgent or early start PD. Nearly half (48%, 29/60) of the PD catheters inserted electively were in smaller elective hubs rather than the regional unit. A total of 97% of patients successfully started PD. Patients who experienced percutaneous PD catheter insertion were older [median age 76 (range 37-88) vs. 56 (range 18-84), p < 0.0001] and had less previous abdominal surgery than patients who experienced laparoscopic PD catheter insertion (25%, 6/24 vs. 54%, 22/41, p = 0.05).

DISCUSSION

Through a service reconfiguration bundle, we were able to double our annual incident PD population. This study highlights how flexible models of service delivery introduced as a bundle can quickly deliver expanded access to PD and home therapy.

A decade of arteriovenous fistula creations in the ⩾75 years population: Equal opportunity or sub-optimal use of resources

BACKGROUND

The optimal vascular access in the elderly remains contentious in the context of increasingly limited resources and anticipated survival on hemodialysis. Research focus has shifted to include the impact of vascular access on quality of life. This study explored clinical outcomes in individuals aged ⩾75 years who had an arteriovenous fistula (AVF) created in a single center over a 10-year period.

MATERIALS AND METHODS

Demographic and clinical data concerning AVFs created January 2009-December 2019 were identified from a prospective database for retrospective analysis. Outcome measures were AVF patency and failure to mature rates plus overall patient and vascular access survival. The Vascular Access Specific Quality of life measure (VASQoL) was completed in a contemporary cohort aged ⩾75 years established on HD in October 2021.

RESULTS

AVF outcomes were available for 272 patients (93%). The failure to mature (FTM) rate was 36% with the significant predictors of AVF FTM being the creation of a radiocephalic AVF (OR 8.13, 95% CI 8.02-8.52, p < 0.01), female gender (OR 4.84, 95% CI 4.70-5.41, p < 0.01), and a history of peripheral vascular disease (OR 5.25, 95% CI 5.22-6.00, p value = 0.02). Functional patency was associated with a median 12-month survival benefit compared to those whose fistula FTM (p < 0.01). The median patency duration for a functionally patent AVF was 3 years. Elderly patients with a fistula reported a lower quality of life in VASQoL scoring than those with central venous catheters.

CONCLUSIONS

In this cohort, AVF creation in individuals aged ⩾75 years AVFs was associated with comparable AVF patency rates to younger patients. AVF functional patency was associated with superior patient survival compared to those with AVF FTM. A multi-disciplinary surveillance program may help reduce AVF loss. Further work on how vascular access choice impacts quality of life in elderly patients is required.

Identifying classification systems regarding vascular access for haemodialysis: protocol for a scoping review

INTRODUCTION

Classifications are important clinical tools that enable data arrangement, patient categorisation and comparative research. The care of patients with end-stage renal disease who have vascular access requires collaboration of several specialists. In such a field, where several different specialties overlap, strong evidence and well-grounded recommendations for good practice are essential. In this protocol, we aim to search the literature to identify classification systems regarding vascular access for haemodialysis. This protocol serves as a pragmatic tool for setting a systematic approach using scoping review methodology. It also aims to make the study transparent and avoid potential duplication.

METHODS AND ANALYSIS

We will follow the Joanna Briggs Institute methodology for the conduct of scoping reviews during the course of the proposed review. Scopus, Web of Science, PubMed, Google Scholar and the ClinicalTrials.gov registry will be searched by two researchers. Titles and abstracts will be screened and articles featuring classifications regarding vascular access for haemodialysis will be eligible for full-text analysis. There will be no age, sex or race limitation for the study populations. The title and abstract (if abstract available) must be in English but there will be no language restrictions for full-text review. Databases will be searched from inception to the date of search. All patients indicated for creation or placement of vascular access will be eligible, as well as patients with already existing vascular access. Classifications regarding preprocedural assessment, vascular access insertion or creation, complications and their management will be included in the study. Classifications regarding peritoneal dialysis will not be eligible. A comprehensive summary of the available evidence will be presented.

ETHICS AND DISSEMINATION

The protocol and the review are exempt from ethical approval as there is no direct patient involvement and the review will summarise data from already published literature. The final article will be submitted to a peer-reviewed scientific journal.

The psychosocial needs of adolescent and young adult kidney transplant recipients, and associated interventions: a scoping review

Background

Renal transplantation is considered the gold standard treatment for end-stage kidney disease. Adolescent and young adult kidney transplant recipients have the highest rate of graft loss amongst transplanted patients. It is largely accepted this is due to psychosocial and behavioural difficulties, which impact adherence to prescribed therapies. This phenomenon is not isolated to a particular healthcare system having been observed in multiple countries across different continents. It is a global issue of concern. We sought to review the psychosocial needs of these patients, and the interventions designed to meet these needs.

Methods

A scoping review was conducted based on Arksey and O’Malley’s six-stage framework. Eligibility criteria included primary studies of any type that investigated the psychosocial needs of adolescent and/or young adult renal transplant recipients or studies which examined interventions designed to address these needs. Search strategies were developed and conducted on PsycINFO, PubMed, Embase, and CINAHL. Articles meeting the inclusion criteria were critically reviewed using a descriptive-analytical narrative method.

Results

Thirty-nine studies met our inclusion criteria, 30 of which related to psychosocial needs, and the remainder examined psychosocial interventions. Four main themes were derived from our analysis of psychosocial needs literature, as follows: the need for (1) emotional support, (2) acceptance, (3) direction, (4) equality in healthcare. 2 main themes emerged from analysis of psychosocial intervention literature, namely: psychosocial (1) capability, (2) assessment. Despite the evidence that graft health is strongly associated with psychosocial wellbeing, findings revealed a significant lack of literature investigating how best to meet psychosocial needs. Trends were observed amongst intervention studies, namely interventions of novel and non-evidenced based design, with the aim of improving medication adherence through organisational strategies and education. However, literature regarding psychosocial needs showed non-adherence to therapies was not simply a result of disorganisation or lack of understanding, but rather, was founded on a recipient’s idiosyncratic relationship with their prescribed therapies e.g., psychological, social or financial reasons for non-adherence.

Conclusions

Future research should be directed at investigating the efficacy of evidence-based interventions that empower the individual patient to overcome their specific barrier to an optimal relationship with their therapies.

Seroprevalence of SARS-CoV-2 antibodies in children: a prospective multicentre cohort study

BACKGROUND

Studies based on molecular testing of oral/nasal swabs underestimate SARS-CoV-2 infection due to issues with test sensitivity, test timing and selection bias. The objective of this study was to report the presence of SARS-CoV-2 antibodies, consistent with previous infection.

DESIGN

This multicentre observational cohort study, conducted between 16 April to 3 July 2020 at 5 UK sites, recruited children of healthcare workers, aged 2-15 years. Participants provided blood samples for SARS-CoV-2 antibody testing and data were gathered regarding unwell contacts and symptoms.

RESULTS

1007 participants were enrolled, and 992 were included in the final analysis. The median age of participants was 10·1 years. There were 68 (6.9%) participants with positive SARS-CoV-2 antibody tests indicative of previous SARS-CoV-2 infection. Of these, 34/68 (50%) reported no symptoms prior to testing. The presence of antibodies and the mean antibody titre was not influenced by age. Following multivariable analysis four independent variables were identified as significantly associated with SARS-CoV-2 seropositivity: known infected household contact OR=10.9 (95% CI 6.1 to 19.6); fatigue OR=16.8 (95% CI 5.5 to 51.9); gastrointestinal symptoms OR=6.6 (95% CI 3.0 to 13.8); and changes in sense of smell or taste OR=10.0 (95% CI 2.4 to 11.4).

DISCUSSION

Children demonstrated similar antibody titres in response to SARS-CoV-2 irrespective of age. Fatigue, gastrointestinal symptoms and changes in sense of smell or taste were the symptoms most strongly associated with SARS-CoV-2 antibody positivity.

TRIAL REGISTRATION NUMBER

NCT0434740.

Loop-mediated isothermal amplification for the early diagnosis of invasive meningococcal disease in children

BACKGROUND

Rapid molecular diagnostic testing has the potential to improve the early recognition of meningococcal disease (MD). The aim of this study was to report on the diagnostic test accuracy of point-of-care loop-mediated isothermal amplification (LAMP) in the diagnosis of MD.

DESIGN

Data were collected prospectively from three UK emergency departments (ED) between November 2017 and June 2019. Consecutive children under 18 years of age attending the ED with features of MD were eligible for inclusion. The meningococcal LAMP test (index test) was performed on a dry swab of the child's oropharynx. Reference standard testing was the confirmation of invasive MD defined as positive N. meningitidis culture or PCR result from a sterile body site (blood or cerebrospinal fluid).

RESULTS

There were 260 children included in the final analysis. The median age was 2 years 11 months and 169 (65%) children were aged 5 years or younger. The LAMP test was negative in 246 children and positive in 14 children. Of the 14 children with positive LAMP tests, there were five cases of invasive MD. Of the 246 children with negative LAMP tests, there were no cases of invasive MD. The sensitivity of LAMP testing was 1.00 and the specificity was 0.97. The negative and positive predictive values were 1.00 and 0.36, respectively. The positive likelihood ratio was 28.3.

DISCUSSION

Non-invasive LAMP testing using oropharyngeal swabs provided an accurate fast and minimally invasive mechanism for predicting invasive MD in this study.

TRIAL REGISTRATION NUMBER

NCT03378258.

Seroprevalence of SARS-CoV-2 antibodies in children of United Kingdom healthcare workers: a prospective multicentre cohort study protocol

BACKGROUND

A novel coronavirus SARS-CoV-2 has been responsible for a worldwide pandemic. Children typically have very mild, or no, symptoms of infection. This makes estimations of seroprevalence in children difficult. Research is therefore required to determine the seroprevalence of SARS-CoV-2 antibodies in children. The primary objective of this study is to report the seroprevalence of SARS-CoV-2 IgM and/or IgG antibodies in healthy children at baseline, 2 months and 6 months. This is the only longitudinal UK study of seroprevalence in an exclusively paediatric population. Determining the changing seroprevalence is of vital public health importance and can help inform decisions around the lifting of paediatric specific social distancing measures such as school closures and the cancellation of routine paediatric hospital services.

METHODS AND ANALYSIS

1000 healthy children of healthcare workers aged between 2 and 15 years will be recruited from five UK sites (Belfast, Cardiff, Glasgow, London and Manchester). The children will undergo phlebotomy at baseline, 2 months and 6 months to measure IgM and/or IgG positivity to SARS-CoV-2. A sample size of 675 patients is required to detect a 5% change in seroprevalence at each time point assuming an alpha of 0.05 and a beta of 0.2. Adjusted probabilities for the presence of IgG and/or IgM antibodies and of SARS-CoV-2 infection will be reported using logistic regression models where appropriate.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the London - Chelsea Research Ethics Committee (REC Reference-20/HRA/1731) and the Belfast Health & Social Care Trust Research Governance (Reference 19147TW-SW). Results of this study will be made available as preprints and submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT0434740; Results.

Diagnostic test accuracy of point-of-care procalcitonin to diagnose serious bacterial infections in children

BACKGROUND

The National Institute for Health and Care Excellence (NICE) have called for research into the role of biomarkers, and specifically procalcitonin (PCT), for the early diagnosis of serious bacterial infections (SBI) in children. The aim of this study was to compare the diagnostic test accuracy of C-reactive protein (CRP) and PCT for the diagnosis of SBI in children.

METHODS

Data was collected prospectively from four UK emergency departments (ED) between November 2017 and June 2019. Consecutive children under 18 years of age with fever and features of possible sepsis and/or meningitis were eligible for inclusion. The index tests were PCT and CRP and the reference standard was the confirmation of SBI.

RESULTS

213 children were included in the final analysis. 116 participants (54.5%) were male, and the median age was 2 years, 9 months. Parenteral antibiotics were given to 100 (46.9%), three (1.4%) were admitted to a paediatric intensive care unit and there were no deaths. There were ten (4.7%) confirmed SBI. The area under the curve for PCT and CRP for the detection of SBI was identical at 0.70.

CONCLUSIONS

There was no difference in the performance of PCT and CRP for the recognition of SBI in this cohort.

TRIAL REGISTRATION

Registered at https://www.clinicaltrials.gov (trial registration: NCT03378258 ) on the 19th of December 2017.

Fifteen-minute consultation: Symptoms and signs of meningococcal disease

Meningococcal disease remains a leading cause of meningitis, sepsis and death in children worldwide and in the UK. Successful vaccination programmes in the UK have, however, significantly reduced the burden of disease in children. Unfortunately, despite vaccination, a significant number of children are still diagnosed with invasive meningococcal disease each year.As the prevalence of meningococcal disease falls, it is important that we maintain awareness of the symptoms and signs of meningococcal disease because the prompt recognition of this life-threatening infection improves outcomes.In this article we discuss the pathology, epidemiology and recognition of invasive meningococcal disease in children. The aim is to maintain awareness of this rare but life-threatening infection.

A protocol for a systematic review and meta-analysis of the diagnostic accuracy of mid-regional pro-adrenomedullin in predicting invasive bacterial infection in children

BACKGROUND

The early recognition of invasive bacterial infections (IBI) in children can be difficult. Clinically it is often challenging to differentiate between the early stages of an IBI and a benign self-limiting viral infection. These challenges mandate a cautious approach resulting in the overuse of antimicrobial drugs with resultant antimicrobial resistance. Due to these challenges, there is growing research into the role of biomarkers for the early identification of children with IBI. Earlier and more accurate diagnoses may lead to improved clinical outcomes for children and reduced antimicrobial resistance. Mid-regional pro-adrenomedullin (MR-proADM) is a biomarker that has been shown to be elevated in patients with IBI. The aim of this systematic review is to determine the diagnostic accuracy of MR-proADM at identifying children with IBI.

METHODS

To identify relevant studies we will search MEDLINE, Embase, Web of Science and Scopus from 1980 to the present day for all human clinical trials involving children that report the test accuracy of MR-proADM. We will include case-control studies, cohort studies and randomised control trials reported in any language. In addition, we will hand-search reference lists and grey literature including conference abstracts and web searches. Two reviewers will independently screen study titles and abstracts for eligibility followed by full-text assessment and data extraction including population, setting, timing and use of index test and reference standard used. Methodological quality will be assessed, by two authors, according to the revised tool for the quality assessment of diagnostic accuracy studies (QUADAS-2), any discrepancies will be resolved by a third author. The following test characteristics will be extracted into 2 × 2 tables for all included studies: true positives, false positives, true negatives and false negatives. Study-specific estimates of sensitivity and specificity with 95% confidence intervals will be displayed in forest plots.

DISCUSSION

This review will report the normal ranges for MR-proADM in health and the diagnostic accuracy of MR-proADM at identifying children with IBI. The review will help to define where in the diagnostic pathway MR-proADM could be useful including potential as a point-of-care test for children at first presentation with IBI.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018096295.

Protective effects of intermedin/adrenomedullin-2 in a cellular model of human pulmonary arterial hypertension

Proliferation of pulmonary fibroblasts (PF) and distal migration of smooth muscle cells (PSM) are hallmarks of pulmonary arterial hypertension (PAH). Intermedin/adrenomedullin-2 (IMD/AM2) belongs to the Calcitonin Gene-Related Peptide (CGRP)/Adrenomedullin (AM) superfamily. These peptides act via Calcitonin-Like Receptors (CLR) combined with one of three Receptor activity-modifying proteins (RAMPs). IMD/AM2 is a potent pulmonary vasodilator in animal studies. The aim was to describe expression of IMD/AM2, AM and receptor components in human pulmonary vascular cells and to elucidate effects of IMD/AM2 on human PSM migration and PF proliferation. Gene expression was detected by immunofluorescence, immunoblotting and qRT-PCR. Normotension and hypertension were simulated by applying pulsatile mechanical stretch (Flexcell® apparatus). Viable cell numbers were determined by dye exclusion. PSM chemotaxis was measured via Dunn chamber. IMD/AM2 protein was co-expressed with AM and their receptor components in pulmonary artery and microvascular endothelial (PAEC, PMVEC) and non-endothelial cells (PF, PSM), and localised to vesicles. IMD/AM2 was secreted under basal conditions, most abundantly from PF and PMVEC. Secretion from PF and PSM was enhanced by stretch. IMD/AM2 mRNA expression increased in response to hypertensive stretch of PSM. IMD/AM2 inhibited PDGF (10^-7 M)-mediated PSM migration maximally at 3 × 10^-10 M and PF proliferation maximally at 3 × 10^-9 M. Angiotensin II (5 × 10^-8 M), normotensive and hypertensive stretch augmented PF proliferation. IMD/AM2 (10^-9 M) abolished the proliferative effects of Angiotensin II and normotensive stretch and attenuated the proliferative effect of hypertensive stretch alone and combined with angiotensin II. These findings indicate an important counter-regulatory role for IMD/AM2 in PAH.

The Impact of Structured Incentives on the Adoption of a Serious Game for Hand Hygiene Training in a Hospital Setting

Hand hygiene is recognized by the CDC as the most effective method of preventing Hospital Acquired Infections (HAIs) which cost the US healthcare system $14 Billion. However, training and promotion of hand hygiene in healthcare settings is an on-going challenge. This paper describes a hand hygiene improvement campaign in Edinburgh Royal Infirmary (Scotland, UK) using the SureWash gesture recognition system (SureWash, IRL). The campaign consisted of two phases of three-months each; the first phase involved technology evaluation and familiarization in a variety of settings within the hospital. The second phase involved rotation between two units with specific changes to the incentives for completing the training. There were 2,010 individual training sessions with over 30% outside of office hours. Individuals completed an average of 2.72 training sessions each and 90% of staff passed the assessment. Senior staff noted a change in hand hygiene culture following the campaign and the good-natured competition between staff to demonstrate hand hygiene competence using the SureWash serious game. While the new technology did facilitate the culture change its successful implementation was dependent on a set of incentives for staff and a structured implementation plan.

The effect of gabapentin and ketorolac on allodynia and conditioned place preference in antibody-induced inflammation

BACKGROUND

Glucose-6-phosphate isomerase and collagen type II antibody-induced arthritis models (K/BxN and CAIA, respectively) have an inflammatory and a post-inflammatory phase. Both phases display robust tactile allodynia. In previous work, inflammatory phase allodynia was reversed by gabapentin and ketorolac, whereas in late phase only gabapentin was effective. Here, we sought to determine if the effects of these two drugs during the early and late phases of the two arthritis models were observed in the conditioned place preference (CPP) paradigm, indicating a differential drug effect on the aversive state.

METHODS

Male C57BL/6 mice received K/BxN serum intraperitoneally, while male BALB/c mice received collagen type II antibody cocktail intravenously. After onset of inflammation and allodynia, we assessed effects of i.p. gabapentin (100 mg/kg) or ketorolac (15 mg/kg) using a CPP paradigm: 2 days adaptation, 2 days conditioning (vehicle in morning and drug in afternoon), preference testing on day 5.

RESULTS

Consistent with the effects upon allodynia, both gabapentin and ketorolac produced a preference for the drug-paired compartment in the early phase of the K/BxN model, while gabapentin, but not ketorolac, resulted in a place preference during late phase. In the CAIA model, consistent with differential effects upon allodynia, gabapentin produced a preference in the early phase and a trend in the late phase, whereas ketorolac was ineffective at either time.

CONCLUSIONS

CPP validated the aversive state in the inflammatory and post-inflammatory phases of the K/BxN and CAIA arthritis models and correspondence between the anti-hyperpathic pharmacology as defined by thresholds and CPP.

Differences in cisplatin-induced mechanical allodynia in male and female mice

BACKGROUND

Chemotherapeutic agents, such as cisplatin, are known to induce a persistent polyneuropathy. The mechanisms underlying the development of this pain are complex, and have only been investigated rodent models using male animals, despite an equivalent presentation of neuropathy between the sexes, clinically.

METHODS

Male and female C57Bl/6, Tlr3(-/-) Tlr4(-/-) , Myd88(-/-) , Trif(lps2) and Myd88(-/-) /Trif(lps2) mice received 6 i.p. injections of cisplatin (2.3 mg/kg/day) every other day over the course of 2 weeks. Changes in tactile threshold were monitored during this time, continuing through day 23, using von Frey filaments.

RESULTS

Male WT mice develop a persistent tactile allodynia resulting from cisplatin administration. Female mice develop an initial allodynia, but thresholds return to baseline by day 23. Deletion of TLR3, TLR4, MyD88 and Trif/MyD88 protects animals from the development of cisplatin-induced polyneuropathy, and there are no sex differences. Trif(lps2) male mice show a persistent tactile allodynia following cisplatin administration, while female mice show a reduced allodynia, and remain higher in threshold than their male counterparts. On day 18, animals were given the analgesic gabapentin, and thresholds were tested 45 min after. Gabapentin was effective in transiently reversing mechanical allodynia in those mice with lowered thresholds.

CONCLUSIONS

It is important to continue examining both sexes in various pain models, as a mononeuropathy and polyneuropathy show sex differences in pain development and the role of TLR signalling.

Association study of genes related to bone formation and resorption and the extent of radiographic change in ankylosing spondylitis

OBJECTIVE

To identify genetic associations with severity of radiographic damage in ankylosing spondylitis (AS).

METHOD

We studied 1537 AS cases of European descent; all fulfilled the modified New York Criteria. Radiographic severity was assessed from digitised lateral radiographs of the cervical and lumbar spine using the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). A two-phase genotyping design was used. In phase 1, 498 single nucleotide polymorphisms (SNPs) were genotyped in 688 cases; these were selected to capture >90% of the common haplotypic variation in the exons, exon-intron boundaries, and 5 kb flanking DNA in the 5' and 3' UTR of 74 genes involved in anabolic or catabolic bone pathways. In phase 2, 15 SNPs exhibiting p<0.05 were genotyped in a further cohort of 830 AS cases; results were analysed both separately and in combination with the discovery phase data. Association was tested by contingency tables after separating the samples into 'mild' and 'severe' groups, defined as the bottom and top 40% by mSASSS, adjusted for gender and disease duration.

RESULTS

Experiment-wise association was observed with the SNP rs8092336 (combined OR 0.32, p=1.2×10(-5)), which lies within RANK (receptor activator of NFκB), a gene involved in osteoclastogenesis, and in the interaction between T cells and dendritic cells. Association was also found with the SNP rs1236913 in PTGS1 (prostaglandin-endoperoxide synthase 1, cyclooxygenase 1), giving an OR of 0.53 (p=2.6×10(-3)). There was no observed association between radiographic severity and HLA-B*27.

CONCLUSIONS

These findings support roles for bone resorption and prostaglandins pathways in the osteoproliferative changes in AS.

Synergistic benefit in inflammatory arthritis by targeting I kappaB kinase epsilon and interferon beta

OBJECTIVES

The I kappaB kinase (IKK)-related kinase IKKepsilon regulates type I interferon expression and responses as well as proinflammatory mediator production. We examined the role of IKKepsilon in arthritis and its ability to enhance the therapeutic response to systemic interferon (IFN) beta therapy in passive murine K/BxN arthritis.

METHODS

IKKepsilon(-/-), IFN alpha(approximately)beta R(-/-) and wild type mice were given K/BxN serum and treated with polyinosinic polycytidylic acid (poly(I:C)), IFN beta, or normal saline. Clinical response and histological scores were assessed. Gene expression in the paws was measured by quantitative PCR. Serum interleukin 1a receptor agonist (IL1Ra) and IL10 were measured by ELISA and multiplex bead array.

RESULTS

Arthritis was almost completely blocked in wild type mice if arthritogenic K/BxN serum and the Toll-like receptor (TLR)3 ligand, poly(I:C), were coadministered at the onset of the model, but not in established disease. Mice deficient in IFN alpha(approximately)beta R had an accelerated course of arthritis, and did not respond to poly(I:C). IKKepsilon null mice had a modest decrease in clinical arthritis compared with heterozygous mice. Low doses of IFN beta that were ineffective in wild type mice significantly decreased clinical arthritis in IKKepsilon null mice. Articular chemokine gene expression was reduced in the IKKepsilon(-/-) mice with arthritis and secreted IL1Ra (sIL1Ra) mRNA was significantly increased. Serum levels of IL1Ra were increased in low dose IFN beta-treated IKKepsilon(-/-) mice.

CONCLUSIONS

Subtherapeutic doses of IFN beta enhance the anti-inflammatory effects of IKKepsilon deficiency, possibly by increasing production of IL1Ra and unmasking the antichemokine effects. Combination therapy with low dose IFN beta and an IKKepsilon inhibitor might improve efficacy of either agent alone and offers a novel approach to RA.

Measurement of DKK1 and FRP in breast and prostate cancer patients with bone metastases: Impact of zoledronic acid (ZA)

19659

Background: Bone metastases produce an imbalance in osteoblast and osteoclast activity. While metastases from prostate cancer are osteoblastic, metastases from breast cancer may be osteolytic, osteoblastic or mixed. The wnt/frizzled pathway is involved in maturation of osteoblasts and in adult bone homeostasis. We explored the wnt antagonists dickkopf (DKK1) and frizzled related protein (FRP) as potential biomarkers in bone metastasis after ZA treatment. Methods: This is a pilot cohort study in bisphosphonate naive breast and prostate cancer patients with bone metastases. Cancer therapy was not specified. Patients received 2 monthly doses of ZA 4 mg IV. Pre- and post-treatment (day 60) sera were collected for measurement of FRP and DKK1, along with IL-6, calcium, creatinine and bone-specific alkaline phosphatase (BAP, a marker of osteoblast activity). Primary endpoint: mean change in FRP and DKK1; Secondary endpoints: correlation of biomarkers with each other and comparison of breast vs. prostate cancer patients. Biomarkers were measured using standard ELISA assays. Statistics: comparison of means = student t-test, correlation coefficients = Pearson. Results: Mature data from 14 patients are reported here, 9 with breast and 5 with prostate cancer. Mean age = 61 years (range 42–89). Two breast cancer patients were premenopausal. One prostate and 3 breast cancer patients received chemotherapy; all others were treated hormonally. After ZA, calcium decreased in all patients (p = 0.09). BAP decreased in all but 1 breast and 1 prostate cancer patient (mean decrease 20.0, p = 0.16). IL-6 was undetectable in most patients. FRP decreased in all but 4 patients (mean decrease 6.2, p = 0.13). There was no discernable pattern for DKK1. Pre-treatment DKK1 correlated with FRP (p = 0.01, r2 = 0.39), but there was no correlation post-treatment. Post-treatment DKK1 correlated with both serum calcium (p = 0.04, r2 = 0.49) and BAP (p = 0.005, r2 = 0.65). There was no difference between breast and prostate cancer patients. Conclusions: It is feasible to measure DKK1 and FRP in patients with malignant bone disease. Treatment with ZA has measurable effects upon these and other serum markers. Further studies with more patients are needed to evaluate their potential as biomarkers.

No significant financial relationships to disclose.

Classification of osteoarthritis biomarkers: a proposed approach

OBJECTIVE

Osteoarthritis (OA) biomarkers are needed by researchers and clinicians to assist in disease diagnosis and assessment of disease severity, risk of onset, and progression. As effective agents for OA are developed and tested in clinical studies, biomarkers that reliably mirror or predict the progression or amelioration of OA will also be needed.

METHODS

The NIH-funded OA Biomarkers Network is a multidisciplinary group interested in the development and validation of OA biomarkers. This review summarizes our efforts to characterize and classify OA biomarkers.

RESULTS

We propose the "BIPED" biomarker classification (which stands for Burden of Disease, Investigative, Prognostic, Efficacy of Intervention and Diagnostic), and offer suggestions on optimal study design and analytic methods for use in OA investigations.

CONCLUSION

The BIPED classification provides specific biomarker definitions with the goal of improving our ability to develop and analyze OA biomarkers, and to communicate these advances within a common framework.

Frizzled-related protein variants are risk factors for hip osteoarthritis

OBJECTIVE

To examine the association of the Arg200Trp and Arg324Gly variants of FRZB with the risk and phenotype of radiographic osteoarthritis (OA) of the hip and serum levels of Frizzled-related protein (FRP) in a prospective cohort of elderly Caucasian women.

METHODS

Radiographic hip OA status of patients was defined by the presence of severe joint space narrowing (JSN) (feature grade>or=3), a summary grade>or=3, or definite osteophytes (grade>or=2) and JSN (grade>or=2) in the same hip. Genotypes were obtained in 569 patients with radiographic OA of the hip and in 1,317 and 4,136 controls for the Arg200Trp and Arg324Gly variants, respectively. Serum FRP levels were measured by enzyme-linked immunosorbent assay. Multivariate logistic regression was performed.

RESULTS

The minor allele frequency for the Arg200Trp polymorphism was 0.12 in the control group compared with 0.14 in the group with radiographic OA of the hip (P=0.12), and the minor allele frequency for the Arg324Gly variant was 0.083 in the control group compared with 0.088 in the group with radiographic OA of the hip (P=0.63). The multilocus genotypes available in 1,886 subjects suggested that inheritance of both minor alleles was a risk factor for developing OA characterized by JSN (P<0.01). Patients with radiographic OA of the hip who were homozygous for the Arg200Trp minor allele had higher serum FRP levels than controls who were homozygous for the major allele.

CONCLUSION

Our data confirm findings of another study, that a rare haplotype with both Arg200Trp and Arg324Gly FRZB variants contributes to the genetic susceptibility to hip OA among Caucasian women, and that these polymorphisms may contribute to increased serum levels of proteins as biomarkers of OA.

Blockade of Wnt-5A/frizzled 5 signaling inhibits rheumatoid synoviocyte activation

OBJECTIVE

It is not understood why cultured fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) often display a persistently activated phenotype, despite removal from an inflammatory environment. Previously, we found that these FLS expressed high levels of both Wnt-5A and Frizzled 5 (Fz5), a receptor-ligand pair implicated in both limb bud and bone marrow stem cell development. The objective of the present experiments was to determine whether Wnt-5A/FzS signaling contributes to FLS activation.

METHODS

Wnt-5A expression in FLS was inhibited by transfection with both antisense and dominant negative (dn) vectors. Fz5 signaling was blocked with an antibody to the extracellular domain of the receptor. The effects of these treatments on the expression of the proinflammatory cytokines interleukin-6 (IL-6) and IL-15 and on the expression of receptor activator of nuclear factor kappaB ligand (RANKL) were assessed by reverse transcriptase-polymerase chain reaction and immunoblotting.

RESULTS

Both antisense Wnt-5A and dnWnt-5A vectors, but not empty vector, diminished IL-6 and IL-15 expression in RA FLS. Anti-Fz5 antibody exerted similar effects and also reduced RANKL expression.

CONCLUSION

Wnt-5A/Fz5 signaling may contribute to the activated state of FLS in RA. Receptor antagonists of Fz5 should be considered for the treatment of refractory synovitis.

The roles of MHC class II, CD40, and B7 costimulation in CTL induction by plasmid DNA

DNA-based vaccines generate potent CTL responses. The mechanism of T cell stimulation has been attributed to plasmid-transfected dendritic cells. These cells have also been shown to express plasmid-encoded proteins and to become activated by surface marker up-regulation. However, the increased surface expression of CD40 and B7 on these dendritic cells is insufficient to overcome the need for MHC class II-restricted CD4(+) T cell help in the priming of a CTL response. In this study, MHC class II(-/-) mice were unable to generate a CTL response following DNA immunization. This deficit in CTL stimulation by MHC class II-deficient mice was only modestly restored with CD40-activating Ab, suggesting that there were other elements provided by MHC class II-restricted T cell help for CTL induction. CTL activity was also augmented by coinjection with a vector encoding the costimulatory ligand B7.1, but not B7.2. These data indicate that dendritic cells in plasmid DNA-injected mice require conditioning signals from MHC class II-restricted T cells that are both CD40 dependent and independent and that there are different roles for costimulatory molecules that may be involved in inducing optimal CTL activity.

The role of CD40 ligand and tumor necrosis factor alpha signaling in the transgenic K/BxN mouse model of rheumatoid arthritis

OBJECTIVE

Spontaneous arthritis in the KRN transgenic mouse (K/BxN) model is due to the autoreactivity of the transgenic T cell receptor and subsequent induction of autoantibodies directed against glucose-6-phosphate isomerase (G6PI). This study sought to analyze the potential of anti-CD40 ligand (anti-CD40L) and anti-tumor necrosis factor alpha (anti-TNFalpha) antibodies in preventing and treating arthritis in this murine model.

METHODS

Groups of K/BxN mice were injected with anti-CD40L and anti-TNFalpha antibodies during various stages of arthritis. Disease was assessed by clinical scoring, measurements of paw swelling, and histology. The results were correlated with the levels of autoantibodies in the serum, as assessed by enzyme-linked immunosorbent assay.

RESULTS

Anti-CD40L antibody treatment was able to diminish significantly the arthritis development in K/BxN mice when given a week before the onset of clinically apparent disease. However, no effect on disease was seen when the antibodies were administered after clinical onset. Surprisingly, neutralizing anti-TNFalpha antibodies were unable to prevent arthritis in K/BxN mice. The success of antibody treatment in preventing disease correlated with low levels of anti-G6PI antibodies in the serum.

CONCLUSION

These results suggest that anti-CD40L treatment can prevent arthritis development in a model of immunoglobulin-mediated arthritis, but anti-TNFalpha treatment cannot. The unsuccessful treatment of established disease was possibly due to the continued presence of autoreactive antibodies in the arthritic mice.

Immunostimulatory DNA-based vaccines induce cytotoxic lymphocyte activity by a T-helper cell-independent mechanism

Immunostimulatory DNA sequences (ISS) contain unmethylated CpG dinucleotides within a defined motif. Immunization with ISS-based vaccines has been shown to induce high antigen-specific cytotoxic lymphocyte (CTL) activity and a Th1-biased immune response. We have developed a novel ISS-based vaccine composed of ovalbumin (OVA) chemically conjugated to ISS-oligodeoxynucleotide (ODN). Protein-ISS conjugate (PIC) is more potent in priming CTL activity and Th1-biased immunity than other ISS-based vaccines. Cytotoxic lymphocyte activation by ISS-ODN-based vaccines is preserved in both CD4-/- and MHC class II-/- gene-deficient animals. Furthermore, PIC provides protection against a lethal burden of OVA-expressing tumor cells in a CD8+ cell-dependent manner. These results demonstrate that PIC acts through two unique mechanisms: T-helper-independent activation of CTL and facilitation of exogenous antigen presentation on MHC class I. This technology may have clinical applications in cancer therapy and in stimulating host defense in AIDS and chronic immunosuppression.

Expression and function of wingless and frizzled homologs in rheumatoid arthritis

Rheumatoid arthritis (RA) is accompanied by synovial inflammation, proliferation, and cartilage destruction. The reasons the activation of synovial fibroblasts often persists despite antiinflammatory therapy are not known. One possibility is that the synovial membrane becomes gradually repopulated with immature mesenchymal and bone marrow cells with altered properties. To explore this hypothesis, we have investigated the expression in RA synovial tissues of various embryonic growth factors from the wingless (wnt) and frizzled (fz) families, which have been implicated in cell-fate determination in both bone marrow progenitors and limb-bud mesenchyme. Reverse transcriptase-PCR analysis revealed expression of five wnt (wnt1, 5a, 10b, 11, and 13) and three fz (fz2, 5, and 7) isoforms in RA synovial tissues. Osteoarthritis synovial tissues expressed much less wnt5a and fz5. Northern blotting confirmed the overexpression of wnt5a and fz5 in RA synovial tissues, in comparison to a panel of normal adult tissues. Compared with normal synovial fibroblasts, cultured RA fibroblast-like synoviocytes expressed higher levels of IL-6, IL-8, and IL-15. Transfection of normal fibroblasts with a wnt5a expression vector reproduced this pattern of cytokine expression and stimulated IL-15 secretion. These results suggest that the unusual phenotypic properties of RA fibroblasts may be attributable partly to their replacement with primitive fibroblast-like synoviocytes with characteristics of immature bone marrow and mesenchymal cells. Clear delineation of the signaling pathway(s) initiated by the wnt5a/fz5 ligand-receptor pair in the RA synovium may yield new targets for therapeutic intervention.

Reducing occupational stress in intensive care

Stress factors, especially if occurring frequently, can have implications for nursing practice in intensive care. A literature review is presented of the causes of occupational stress in three major categories: the physical environment, the job itself and the organisation (Jee and Reason, 1988). The stressors of noise, nursing in intensive care and bullying are expanded upon. Recommendations for strategies which could be employed to manage occupational stress are put forward.

In vivo priming by DNA injection occurs predominantly by antigen transfer

DNA vaccines can stimulate both humoral and cytolytic immune responses. Although bone marrow-derived elements present the expressed Ag, the mechanisms for acquiring immunogenic peptides have yet to be fully elucidated. APCs may become directly transfected by plasmid DNA or process extracellular proteins produced by other transfected cells. Using a transactivating plasmid system and bone marrow chimeras, we show that both mechanisms appear to be involved; however, the bulk of the immune response is dependent on expression of Ag by nonlymphoid tissues and transfer to APCs. These in vivo studies are the first to define the role of transfected nonlymphoid cells in generating Ag for presentation by bone marrow-derived APCs after needle injection with plasmid DNA.

Human rheumatoid factor production is dependent on CD40 signaling and autoantigen

High-affinity pathologic rheumatoid factor (RF) B cells occur in autoimmune diseases such as rheumatoid arthritis, but are deleted in healthy individuals. The reasons for the survival and differentiation of these autoreactive B cells in rheumatoid arthritis are not known. Previous studies in mice transgenic for a human IgM RF have shown that peripheral encounter with soluble human IgG leads to deletion of high-affinity RF B cells; however, deletion can be prevented when concomitant T cell help is provided. This study aimed to further discern the minimal factors necessary not only for the in vivo survival of RF B cells, but also for their differentiation into Ab-secreting cells. The combination of MHC class II-reactive T cells and Ag induced the production of RF in human IgM RF transgenic mice, while either stimulus alone was ineffective. Neutralizing Abs against CD40 ligand (CD40L), but not against IL-4 or IL-15, abrogated IgM-RF production. Moreover, blockade of CD40L-CD40 allowed IgG to delete the RF precursor cells. Most importantly, activating Abs to CD40 could substitute entirely for T cell help in promoting the survival of RF precursors and in stimulating RF synthesis in T cell deficient animals. The data indicate that CD40 signaling alone can prevent deletion of RF B cells by Ag and in the presence of IgG is sufficient to trigger RF synthesis. The results suggest that selective induction of apoptosis in high-affinity RF B cells may be achieved by blockade of CD40L-CD40 interaction.

Rheumatoid factor B cell tolerance via autonomous Fas/FasL-independent apoptosis

Normal individuals do not express the high-affinity autoantibodies specific for self-IgG (rheumatoid factors, RF) that are commonly seen in rheumatoid arthritis patients. Studies of transgenic mice expressing a human IgM rheumatoid factor have shown that one mechanism by which higher affinity RF B cells are tolerized to IgG is through abortive RF B cell activation followed by deletion in the absence of T cell help. We show that RF B cell deletion occurs through an intrinsic apoptotic mechanism that is independent of the Fas/FasL pathway and does not involve active killing by T cells, as it occurs in RAG-1-deficient RF transgenic mice to the same extent as in the parental RF transgenic line.

DNA vaccination against multiple myeloma

A variety of approaches to antitumor therapy are currently being explored that use both antigen-encoding DNA and noncoding nucleotides as a component of gene vaccination. Among the specific strategies reviewed are a construct that fuses a single-chain variable fragment (scFv) that incorporates both the variable-region genes necessary to encode the idiotypic determinants with fragment C (FrC) of tetanus toxin; a novel vector system using herpes simplex virus 1 (HSV-1) for in vivo gene delivery; the possibility of eliciting hyperacute xenograft response to treat human cancer; and the use of gene gun-mediated granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA-based tumor cell vaccines. The protection provided by DNA vaccination against viral diseases such as influenza suggested a role for such vaccines against cancer. However, unlike vaccines against infectious diseases, cancer vaccines are therapeutic, rather than prophylactic. With multiple myeloma, for example, it is possible that the optimal timing of administration of such a vaccine is during a remission that has been induced by traditional therapies, to eliminate residual disease. DNA cancer vaccines are designed to activate immune responses to tumor antigens to which the immune system has already been exposed. To do so, the vaccines must first overcome immune tolerance that may have already developed to the tumor. There is increasing evidence that tumor antigens, unlike viral or bacterial antigens, do not consistently activate an immune response. One major factor in determining whether a reaction occurs appears to be whether antigen presentation is accompanied by danger signals. With viral or bacterial infection, the accompanying tissue destruction and inflammation produce costimulatory signals that promote T-cell activation. However, inflammatory and tissue-destructive processes are absent during initial tumor transformation. The typical outcome may be immunologic tolerance.

Presentation of peptide antigens by mouse CD1 requires endosomal localization and protein antigen processing

Mouse CD1(mCD1) molecules have been reported to present two types of antigens: peptides or proteins and the glycolipid alpha-galactosylceramide. Here, we demonstrate that a protein antigen, chicken ovalbumin (Ova), must be processed to generate peptides presented by mCD1 to CD8(+) T cells. The processing and mCD1-mediated presentation of chicken Ova depend on endosomal localization because inhibitors of endosomal acidification and endosomal recycling pathways block T cell reactivity. Furthermore, a cytoplasmic tail mutant of mCD1, which disrupts endosomal localization, has a greatly reduced capacity to present Ova to mCD1 restricted cells. Newly synthesized mCD1 molecules, however, are not required for Ova presentation, suggesting that molecules recycling from the cell surface are needed. Because of these data showing that mCD1 trafficks to endosomes, where it can bind peptides derived from exogenous proteins, we conclude that peptide antigen presentation by mCD1 is likely to be a naturally occurring phenomenon. In competition assays, alpha-galactosylceramide did not inhibit Ova presentation, and presentation of the glycolipid was not inhibited by excess Ova or the peptide epitope derived from it. This suggests that, although both lipid and peptide presentation may occur naturally, mCD1 may interact differently with these two types of antigens.

Control of immune responses by gene immunization

The use of plasmid DNA to elicit immune responses has greatly increased our ability to skew the desired immune response to a particular antigen. DNA immunization elicits potent cell-mediated responses including humoral immunity as well as cytolytic T-lymphocyte immunity. This review will first discuss the overall immune response induced by naked DNA vaccination and will then summarize recent advances in basic research on DNA immunization, which have furthered our understanding of the role of DNA as an adjuvant as well as a carrier of genetic material. Subsequently, we will consider the possible mechanisms by which DNA immunization is able to induce such immune responses and how DNA immunization may be useful in both basic science research and also in future vaccine development in various disease processes. Finally, we will examine the advantages and disadvantages of DNA vaccines as well as safety issues. In conclusion, DNA vaccination shows promise in a number of areas including infectious diseases, allergy and cancer immunotherapies.

Induction of an antigen-specific, CD1-restricted cytotoxic T lymphocyte response In vivo

The majority of T cell responses are restricted to peptide antigens bound by polymorphic major histocompatibility complex (MHC) molecules. However, peptide antigens can be presented to T cells by murine non-MHC-encoded CD1d (mCD1) molecules, and human T cell lines specific for nonpeptide antigens presented on CD1 isoforms have been identified. It is shown here that antigen-specific, mCD1-restricted lymphocytes can be generated in vivo by immunizing mice with a combination of plasmids encoding chicken ovalbumin, murine CD1d, and costimulatory molecules. Splenocytes from immunized mice have CD1d-restricted, MHC- unrestricted, ovalbumin-specific cytolytic activity that can be inhibited by anti-CD1 antibodies as well as a competing CD1-binding peptide. These results suggest a physiologic role for murine CD1d to present exogenous protein antigens.

Costimulation provided by DNA immunization enhances antitumor immunity

The interaction of the TCR with MHC class I-bound Ag is insufficient for the priming of CTL unless secondary costimulatory signals are provided. To ascertain the minimum elements required to activate an Ag-specific CTL response in vivo, we injected mice intradermally or i.m. with plasmid DNA encoding a MHC class I-restricted peptide Ag (minigene) and different membrane-bound costimulatory ligands. The minigene-encoded epitope only primed a specific CTL response if injected in the vicinity of an ectopically expressed costimulatory ligand. Vector encoding B7-1 was repeatedly more potent at stimulating a cytolytic response than vector encoding B7-2. In contrast the B7-2-encoding plasmid preferentially enhanced Ag-specific Ab responses when injected with either protein or a cDNA expression vector. Gene vaccination with plasmids encoding OVA and B7-1, but not B7-2, prolonged survival in mice challenged with an OVA-transfected tumor. These results show that functional B7-1 transfection can be achieved in vivo and induces the selective induction of CTL. The data suggest that B7-1 plasmids should be coadministered with naked DNA vaccines that aim to induce tumor-specific cellular immunity.

Costimulation provided by DNA immunization enhances antitumor immunity

The interaction of the TCR with MHC class I-bound Ag is insufficient for the priming of CTL unless secondary costimulatory signals are provided. To ascertain the minimum elements required to activate an Ag-specific CTL response in vivo, we injected mice intradermally or i.m. with plasmid DNA encoding a MHC class I-restricted peptide Ag (minigene) and different membrane-bound costimulatory ligands. The minigene-encoded epitope only primed a specific CTL response if injected in the vicinity of an ectopically expressed costimulatory ligand. Vector encoding B7-1 was repeatedly more potent at stimulating a cytolytic response than vector encoding B7-2. In contrast the B7-2-encoding plasmid preferentially enhanced Ag-specific Ab responses when injected with either protein or a cDNA expression vector. Gene vaccination with plasmids encoding OVA and B7-1, but not B7-2, prolonged survival in mice challenged with an OVA-transfected tumor. These results show that functional B7-1 transfection can be achieved in vivo and induces the selective induction of CTL. The data suggest that B7-1 plasmids should be coadministered with naked DNA vaccines that aim to induce tumor-specific cellular immunity.