Evaluating the frequency of positive paraneoplastic antibodies and associated malignancy risk

OBJECTIVE

To evaluate the association between malignancy and frequently positive paraneoplastic antibodies.

METHODS

A retrospective cohort study was carried out for all patients who received paraneoplastic antibody testing in 2013-2014 at a tertiary referral center. Available medical records on included patients were reviewed through July 2020. Patients were divided into antibody positive and negative subgroups. Focused analysis was performed on the subgroup of patients who received testing via a commonly used antibody panel.

RESULTS

A total of 1860 patients (the full cohort) received 19,323 antibody testing via panel or individual antibody testing, and were followed-up for a mean period of 36.2 months (range 0-83 months). Altogether 229 antibodies in 196 patients were positive, and 9 (3.9%) in 7 patients were against onconeuronal antigens. The remaining 220 (96.1%) were positive for mostly antibodies against cell surface or synaptic antigens. A total of 1161 patients received Mayo Clinic paraneoplastic antibody panel tests (the panel cohort), and 14.9% (173) of these patients possessed one or more positive antibodies. For the panel cohort, no difference was found between antibody positive and negative groups with respect to the prevalence of previously existing malignancy (15.6% versus 16.6%, p = 0.745) or incidence of new malignancy (4.0% vs. 3.7%, p = 0.848) during the follow-up period. No difference was observed in the incidence of new malignancy during follow-up between the antibody positive and negative groups for the 7 most frequently positive antibodies.

CONCLUSIONS

The presence of frequently positive antibodies, mostly to cell surface or synaptic antigens, is not clearly associated with the development of malignancy in the subsequent three years.

A one-step NIST traceable HPLC method for quantitation of vitamin B6 and 4-pyridoxic acid in human plasma

Objectives

Vitamin B6 deficiency is associated with a wide spectrum of clinical syndromes. While vitamin B6 status is primarily assessed by measuring the biologically active form of the vitamin, pyridoxal 5-phosphate (PLP), concurrent measurement of the final metabolite 4-pyridoxic acid (PA) can provide additional information regarding supplement intake and hypophosphatasia. The aim of this study is to develop a simple method traceable to the NIST standard reference material 3950 for simultaneous detection of PLP and PA.

Design & methods

A one-step reverse phase HPLC method with fluorescence detection was developed by evaluating different derivatization conditions, the use of an internal standard and different calibration strategies. The assay analytical performance was evaluated.

Results

Pre-column derivatization with semicarbazide showed the best overall performance in terms of signal to noise ratio, retention time and peak shape when compared to pre- or post-column derivatization with chlorite, pre-column or in-mobile phase derivatization using sodium bisulfite. The final method provided an analytical measurement range from 7.8 to 350 ​nmol/L for PLP and 3.3–339 ​nmol/L for PA, total imprecision <15% and <5% for PLP and PA respectively. Calibration against the NIST standard produced measured values within 3% of NIST assigned PLP values. The use of 4-deoxypyridoxine as internal standard did not improve precision or accuracy when compared to calibration using 5-level external standards.

Conclusions

This method combines derivatization and protein precipitation in one step and is traceable to NIST standard reference material 3950. It is simple and reliable for routine evaluation of vitamin B6 nutrition status.

Assessment of Patient Medication Adherence, Medical Record Accuracy, and Medication Blood Concentrations for Prescription and Over-the-Counter Medications

IMPORTANCE

Inaccurate medication records and poor medication adherence result in incomplete knowledge of therapy for patients.

OBJECTIVE

To study accuracy of medical records and patient adherence by measuring blood concentrations of medications.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study validated a serum-based liquid chromatography-tandem mass spectrometry assay to simultaneously quantify 263 medications used for acute and chronic conditions. The assay panel was applied to 3 clinical patient cohorts: residual serum from 1000 randomly selected samples sent for routine clinical chemistry testing between April 8 and October 6, 2015 (residuals cohort), 50 prospectively enrolled patients in a gastroenterology clinic between March 1 and March 15, 2016, who were prescribed more than 5 medications (gastroenterology care cohort), and a convenience cohort of 296 patients with hypertension who sought care in an emergency department (ED care cohort) between July 1, 2012, and April 25, 2013. Integrated data analysis of the cohorts was performed from August 22 to November 29, 2017.

MAIN OUTCOMES AND MEASURES

Medication serum concentrations, electronic health record medication lists, and predicted drug interactions.

RESULTS

Of the 1346 total samples, 1000 came from the residuals cohort (640 women and 360 men; median age, 60 years [interquartile range (IQR), 44-71 years]), 50 from the gastroenterology care cohort (30 women and 20 men; median age, 66 years [IQR, 62-70 years]), and 296 from the ED care cohort (160 women and 136 men; median age, 59 years [IQR, 52-66 years]). Median medication adherence, defined as the subset of detected medications from the prescription record, was 83% (IQR, 50%-100%) in the residuals cohort, 100% (IQR, 84%-100%) in the gastroenterology care cohort, and 78% (IQR, 57%-100%) in the ED care cohort. Patients adherent to 1 medication were more often adherent to other medications. Among patients prescribed 3 medications or more, there were no significant associations between medication adherence and sex or number of prescribed medications, and there was a modest association between adherence and age. By comparing detected vs prescribed medications, we detected a median of 0 (IQR, 0-2) medications per patient that were not listed in the electronic health record in the residuals cohort, 1 (IQR, 0-2) medication per patient that was not listed in the electronic health record in the gastroenterology care cohort, and 1 (IQR, 0-2) medication per patient that was not listed in the electronic health record in the ED care cohort. A total of 435 patients (43.5%) in the residuals cohort had no discrepancy between the electronic health record and detected medication lists, 22 patients (44.0%) in the gastroenterology care cohort had no discrepancy between the electronic health record and detected medication lists, and 41 patients (13.9%) in the ED care cohort had no discrepancy between the electronic health record and detected medication lists. Half of adverse drug reaction alerts occurred among medications detected without prescription.

CONCLUSIONS AND RELEVANCE

Comprehensive medication monitoring offers promise to improve adherence, the accuracy of medical records, and the safety for patients with polypharmacy.

Medication Exposure in Highly Adherent Psychiatry Patients

Medication exposure is dependent upon many factors, the single most important being if the patient took the prescribed medication as indicated. To assess medication exposure for psychotropic and other medication classes, we enrolled 115 highly adherent psychiatry patients prescribed five or more medications. In these patients, we measured 21 psychotropic and 38 nonpsychotropic medications comprising a 59 medication multiplex assay panel. Strict enrollment criteria and reconciliation of the electronic health record medication list prior to study initiation produced a patient cohort that was adherent with 91% of their prescribed medications as determined by comparing medications detected empirically in blood to the electronic health record medication list. In addition, 13% of detected medications were not in the electronic health record medication list. We found that only 53% of detected medications were within the literature-derived reference range with 41% below and 6% above the reference range specific to each medication. When psychotropic medications were analyzed near trough-level, only sertraline was found to be within the literature-derived reference range for all patients tested. Concentrations of the remaining medications indicated extensive exposure below the reference range. This is the first study to empirically and comprehensively assess medication exposure obtained in comorbid polypharmacy patients, minimizing the important behavioral factor of adherence in the study of medication exposure. These data indicate that low medication exposure is extensive and must be considered when therapeutic issues arise, including the lack of response to medication therapy.

Medication adherence, medical record accuracy, and medication exposure in real-world patients using comprehensive medication monitoring

Background

Poor adherence to medication regimens and medical record inconsistencies result in incomplete knowledge of medication therapy in polypharmacy patients. By quantitatively identifying medications in the blood of patients and reconciling detected medications with the medical record, we have defined the severity of this knowledge gap and created a path toward optimizing medication therapy.

Methods and findings

We validated a liquid chromatography-tandem mass spectrometry assay to detect and/or quantify 38 medications across a broad range of chronic diseases to obtain a comprehensive survey of patient adherence, medical record accuracy, and exposure variability in two patient populations. In a retrospectively tested 821-patient cohort representing U.S. adults, we found that 46% of medications assessed were detected in patients as prescribed in the medical record. Of the remaining medications, 23% were detected, but not listed in the medical record while 30% were prescribed to patients, but not detected in blood. To determine how often each detected medication fell within literature-derived reference ranges when taken as prescribed, we prospectively enrolled a cohort of 151 treatment-regimen adherent patients. In this cohort, we found that 53% of medications that were taken as prescribed, as determined using patient self-reporting, were not within the blood reference range. Of the medications not in range, 83% were below and 17% above the lower and upper range limits, respectively. Only 32% of out-of-range medications could be attributed to short oral half-lives, leaving extensive exposure variability to result from patient behavior, undefined drug interactions, genetics, and other characteristics that can affect medication exposure.

Conclusions

This is the first study to assess compliance, medical record accuracy, and exposure as determinants of real-world treatment and response. Variation in medication detection and exposure is greater than previously demonstrated, illustrating the scope of current therapy issues and opening avenues that warrant further investigation to optimize medication therapy.

Neer Award 2015: Analysis of cytokine profiles in the diagnosis of periprosthetic joint infections of the shoulder

BACKGROUND

Periprosthetic joint infection (PJI) after shoulder arthroplasty can present a diagnostic and therapeutic challenge. This study evaluated the diagnostic utility of broader synovial fluid cytokine analysis for identifying PJI in patients undergoing revision shoulder arthroplasty.

METHODS

Synovial fluid levels of 9 cytokines (interleukin [IL] 6, granulocyte-macrophage colony-stimulating factor, IL-1β, IL-12, IL-2, IL-8, interferon-γ, IL-10, and tumor necrosis factor-α) were measured in 75 cases of revision shoulder arthroplasty with a multiplex immunoassay. Cases were classified into infection categories and groups based on objective perioperative findings. Differences in cytokine levels among infection groups were evaluated. Receiver operating characteristic curves were used to assess the diagnostic utility of the individual synovial fluid cytokines and combinations of cytokines in determining infection status.

RESULTS

Synovial IL-6, granulocyte-macrophage colony-stimulating factor, interferon-γ, IL-1β, IL-2, IL-8, and IL-10 were significantly elevated in cases of revision shoulder arthroplasty classified as infected. Individually, IL-6, IL-1β, IL-8, and IL-10 showed the best combination of sensitivity and specificity for predicting infection, and a combined cytokine model consisting of IL-6, tumor necrosis factor-α, and IL-2 showed better diagnostic test characteristics than any cytokine alone, with sensitivity of 0.80, specificity of 0.93,, positive and negative predictive values of 0.87 and 0.89, and positive and negative likelihood ratios of 12.0 and 0.21.

CONCLUSIONS

Individual and combined synovial fluid cytokine analysis were both more effective than routine perioperative testing, such as serum erythrocyte sedimentation rate and C-reactive protein, in the diagnosis of PJI of the shoulder. Once validated, combined synovial fluid cytokine analysis could be used as a predictive tool to determine the probability of PJI in patients undergoing revision shoulder arthroplasty and better guide treatment.

Characterization of a Plasmodium falciparum Orthologue of the Yeast Ubiquinone-Binding Protein, Coq10p

Coenzyme Q (CoQ, ubiquinone) is a central electron carrier in mitochondrial respiration. CoQ is synthesized through multiple steps involving a number of different enzymes. The prevailing view that the CoQ used in respiration exists as a free pool that diffuses throughout the mitochondrial inner membrane bilayer has recently been challenged. In the yeast Saccharomyces cerevisiae, deletion of the gene encoding Coq10p results in respiration deficiency without inhibiting the synthesis of CoQ, suggesting that the Coq10 protein is critical for the delivery of CoQ to the site(s) of respiration. The precise mechanism by which this is achieved remains unknown at present. We have identified a Plasmodium orthologue of Coq10 (PfCoq10), which is predominantly expressed in trophozoite-stage parasites, and localizes to the parasite mitochondrion. Expression of PfCoq10 in the S. cerevisiae coq10 deletion strain restored the capability of the yeast to grow on respiratory substrates, suggesting a remarkable functional conservation of this protein over a vast evolutionary distance, and despite a relatively low level of amino acid sequence identity. As the antimalarial drug atovaquone acts as a competitive inhibitor of CoQ, we assessed whether over-expression of PfCoq10 altered the atovaquone sensitivity in parasites and in yeast mitochondria, but found no alteration of its activity.

Trends and Patterns in Reporting of Patient Safety Situations in Transplantation

Analysis and dissemination of transplant patient safety data are essential to understanding key issues facing the transplant community and fostering a "culture of safety." The Organ Procurement and Transplantation Network's (OPTN) Operations and Safety Committee de-identified safety situations reported through several mechanisms, including the OPTN's online patient safety portal, through which the number of reported cases has risen sharply. From 2012 to 2013, 438 events were received through either the online portal or other reporting pathways, and about half were self-reports. Communication breakdowns (22.8%) and testing issues (16.0%) were the most common types. Events included preventable errors that led to organ discard as well as near misses. Among events reported by Organ Procurement Organization (OPOs), half came from just 10 of the 58 institutions, while half of events reported by transplant centers came from just 21 of 250 institutions. Thirteen (23%) OPOs and 155 (62%) transplant centers reported no events, suggesting substantial underreporting of safety-related errors to the national database. This is the first comprehensive, published report of the OPTN's safety efforts. Our goals are to raise awareness of safety data recently reported to the OPTN, encourage additional reporting, and spur systems improvements to mitigate future risk.

14-3-3 in Thoracic Aortic Aneurysms: Identification of a Novel Autoantigen in Large Vessel Vasculitis

OBJECTIVE

Large vessel vasculitides (LVV) are a group of autoimmune diseases characterized by injury to and anatomic modifications of large vessels, including the aorta and its branch vessels. Disease etiology is unknown. This study was undertaken to identify antigen targets within affected vessel walls in aortic root, ascending aorta, and aortic arch surgical specimens from patients with LVV, including giant cell arteritis, Takayasu arteritis, and isolated focal aortitis.

METHODS

Thoracic aortic aneurysm specimens and autologous blood were acquired from consenting patients who underwent aorta reconstruction procedures. Aorta proteins were extracted from both patients with LVV and age-, race-, and sex-matched disease controls with noninflammatory aneurysms. A total of 108 serum samples from patients with LVV, matched controls, and controls with antinuclear antibodies, different forms of vasculitis, or sepsis were tested.

RESULTS

Evaluation of 108 serum samples and 22 aortic tissue specimens showed that 78% of patients with LVV produced antibodies to 14-3-3 proteins in the aortic wall (93.7% specificity), whereas controls were less likely to do so (6.7% produced antibodies). LVV patient sera contained autoantibody sufficient to immunoprecipitate 14-3-3 protein(s) from aortic lysates. Three of 7 isoforms of 14-3-3 were found to be up-regulated in aorta specimens from patients with LVV, and 2 isoforms (ε and ζ) were found to be antigenic in LVV.

CONCLUSION

This is the first study to use sterile, snap-frozen thoracic aorta biopsy specimens to identify autoantigens in LVV. Our findings indicate that 78% of patients with LVV have antibody reactivity to 14-3-3 protein(s). The precise role of these antibodies and 14-3-3 proteins in LVV pathogenesis deserves further study.

Co-prescription trends in a large cohort of subjects predict substantial drug-drug interactions

Pharmaceutical prescribing and drug-drug interaction data underlie recommendations on drug combinations that should be avoided or closely monitored by prescribers. Because the number of patients taking multiple medications is increasing, a comprehensive view of prescribing patterns in patients is important to better assess real world pharmaceutical response and evaluate the potential for multi-drug interactions. We obtained self-reported prescription data from NHANES surveys between 1999 and 2010, and confirm the previously reported finding of increasing drug use in the elderly. We studied co-prescription drug trends by focusing on the 2009-2010 survey, which contains prescription data on 690 drugs used by 10,537 subjects. We found that medication profiles were unique for individuals aged 65 years or more, with ≥98 unique drug regimens encountered per 100 subjects taking 3 or more medications. When drugs were viewed by therapeutic class, it was found that the most commonly prescribed drugs were not the most commonly co-prescribed drugs for any of the 16 drug classes investigated. We cross-referenced these medication lists with drug interaction data from Drugs.com to evaluate the potential for drug interactions. The number of drug alerts rose proportionally with the number of co-prescribed medications, rising from 3.3 alerts for individuals prescribed 5 medications to 11.7 alerts for individuals prescribed 10 medications. We found 22% of elderly subjects taking both a substrate and inhibitor of a given cytochrome P450 enzyme, and 4% taking multiple inhibitors of the same enzyme simultaneously. By examining drug pairs prescribed in 0.1% of the population or more, we found low agreement between co-prescription rate and co-discussion in the literature. These data show that prescribing trends in treatment could drive a large extent of individual variability in drug response, and that current pairwise approaches to assessing drug-drug interactions may be inadequate for predicting real world outcomes.

Synovial fluid interleukin-6 as a predictor of periprosthetic shoulder infection

BACKGROUND

Diagnosis of periprosthetic joint infection (PJI) in patients undergoing revision shoulder arthroplasty is challenging because of the low virulence of the most common infecting organisms. The goal of this study was to evaluate the diagnostic utility of measuring synovial fluid interleukin-6 (IL-6) levels for identifying PJI of the shoulder.

METHODS

Thirty-two consecutive patients evaluated for pain at the site of a shoulder arthroplasty were prospectively enrolled from November 2012 to September 2013 and underwent revision surgery (thirty-five procedures during which samples were obtained for synovial fluid IL-6 analysis). Cases were categorized into infection (n = 15) and no-infection (n = 20) groups on the basis of objective preoperative and intraoperative findings. Twenty patients treated with arthroscopic rotator cuff repair were also enrolled to serve as a non-infected control group. Synovial fluid was obtained through aspiration intraoperatively for all patients, as well as preoperatively for some. Synovial fluid IL-6 levels were measured with use of a cytokine immunoassay that utilizes electrochemiluminescent detection. A receiver operating characteristic curve was used to determine the diagnostic utility of synovial fluid IL-6 analysis.

RESULTS

Based on receiver operating characteristic curve analysis, synovial fluid IL-6 measurement had an area under the curve of 0.891 with an ideal cutoff value of 359.3 pg/mL. The sensitivity, specificity, and positive and negative likelihood ratios were 87%, 90%, 8.45, and 0.15, respectively. Seven patients who underwent a single-stage revision had negative results on standard perioperative testing, including the erythrocyte sedimentation rate and C-reactive protein levels, but multiple positive intraoperative tissue cultures. The level of synovial fluid IL-6 was elevated in five of these seven patients, with a median value of 1400 pg/mL. Intraoperative synovial fluid IL-6 values correlated well with preoperative IL-6 synovial fluid values (correlation = 0.61; p = 0.025) and frozen-section histologic findings (p < 0.001). Synovial fluid IL-6 levels were also significantly elevated in patients with Propionibacterium acnes infection (p = 0.01).

CONCLUSIONS

Measurement of synovial fluid IL-6 levels is more sensitive and specific than current preoperative testing for predicting positive cultures for patients undergoing revision shoulder arthroplasty. This diagnostic accuracy can lead to improved decision-making in the management of PJI.

Pyrazoleamide compounds are potent antimalarials that target Na+ homeostasis in intraerythrocytic Plasmodium falciparum

The quest for new antimalarial drugs, especially those with novel modes of action, is essential in the face of emerging drug-resistant parasites. Here we describe a new chemical class of molecules, pyrazoleamides, with potent activity against human malaria parasites and showing remarkably rapid parasite clearance in an in vivo model. Investigations involving pyrazoleamide-resistant parasites, whole-genome sequencing and gene transfers reveal that mutations in two proteins, a calcium-dependent protein kinase (PfCDPK5) and a P-type cation-ATPase (PfATP4), are necessary to impart full resistance to these compounds. A pyrazoleamide compound causes a rapid disruption of Na⁺ regulation in blood-stage Plasmodium falciparum parasites. Similar effect on Na⁺ homeostasis was recently reported for spiroindolones, which are antimalarials of a chemical class quite distinct from pyrazoleamides. Our results reveal that disruption of Na⁺ homeostasis in malaria parasites is a promising mode of antimalarial action mediated by at least two distinct chemical classes.

Novel antimalarial drugs are urgently needed to combat parasite drug resistance. Here, Vaidya et al. describe a new chemical class of potent antimalarial compounds that act by disrupting the parasite's sodium homeostasis.

Limited utilization of serologic testing in patients undergoing duodenal biopsy for celiac disease

Background

Clinical algorithms for the workup of celiac disease often recommend the use of serologic assays for initial screening, followed by duodenal biopsy for histologic confirmation. However, the majority of duodenal biopsies submitted to pathology for “rule out celiac” are negative. The objective of this study was to determine the underlying causes for this low diagnostic yield.

Methods

We performed a retrospective review of pathology reports from 1432 consecutive duodenal biopsies submitted for pathologic assessment to “rule out celiac” and correlated biopsy results with results for concurrent serologic testing for celiac autoantibodies.

Results

The majority of patients had no record of serologic testing prior to biopsy, and evidence of positive serology results was found in only 5% of patients. Most duodenal biopsies were submitted as part of a multi-site GI sampling strategy that included biopsies from other locations. In this context, serologic results correlated with the likelihood of significant duodenal and non-duodenal findings, and were also helpful in evaluating patients with indeterminate duodenal histology.

Conclusions

The presence of a positive screening test for celiac autoantibodies does not appear to be a major driver in the decision to submit duodenal biopsies for evaluation of celiac disease, which accounts for the low incidence of findings in these samples. In patients where celiac serology testing was performed, the results were a good predictor of the likelihood of findings on biopsy.

Impact of analytical variability on clinical interpretation of multiplex pneumococcal serology assays

The response to pneumococcal vaccination can be used to assess a patient's humoral immune response to polysaccharide antigens. Multiplex assays measuring serotype-specific levels of pneumococcal antibodies are often used for this purpose, and clinical algorithms have been published to assist in the definition of an adequate immune response. We evaluated whether interlaboratory variability in multiplex pneumococcal serology assays would affect the clinical classification of the immune response. Specimens from 57 patients were analyzed at three reference laboratories with different multiplex assays to measure pneumococcal serology. Analytical correlation and clinical agreement in the classification of a patient's vaccination status by the three methods were compared. Although substantial variation in the quantitative antibody levels measured by different laboratories was seen, the qualitative classification of individual serologic results showed a high degree of agreement between labs and the ultimate classification of a patient as "protected" or "nonprotected" was the same for most patients. The majority of discordant classifications were driven by a systematic bias in results from one of the assays rather than by random error. These data suggest that the use of integrated assessments based on multiple serotypes can compensate for much of the analytical variability seen between laboratories. Knowledge of the analytical performance characteristics of a particular assay is most important when evaluating patients with results near clinical cut points.

Analytical and biological validation of a multiplex immunoassay for acute kidney injury biomarkers

BACKGROUND

Acute kidney injury (AKI) is a dynamic process that can involve inflammatory, hypoxic, and structural changes to the kidney. We evaluated a multiplex panel of markers representing different AKI mechanisms as a tool to provide integrated assessment of AKI status in a single assay.

METHODS

Urinary cystatin C (CysC), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1) and interleukin-18 (IL-18) were measured by multiplex electrochemiluminescence immunoassay. Analytical performance was compared to the biological and pathological variation of these markers in human samples.

RESULTS

Linearity was established over a 3- to 4-log range for all markers, which spanned the reference ranges established from healthy donors. Imprecision was below 15%, comparing favorably with the observed biological variation of these markers. Control patients fell within donor-derived reference ranges for most markers, but a subset of patients showed CysC and KIM-1 elevations in the absence of documented AKI.

CONCLUSION

The multiplex assay is reliable for simultaneous quantitation of CysC, IL-18, KIM-1 and NGAL in human urine, and performs at levels sufficient for clinical application. The observed differences in biological variability and baseline levels suggest that clinical strategies to detect AKI will need to vary depending upon the specific markers used.

Remarkable stability in patterns of blood-stage gene expression during episodes of non-lethal Plasmodium yoelii malaria

Background

Microarray studies using in vitro cultures of synchronized, blood-stage Plasmodium falciparum malaria parasites have revealed a ‘just-in-time’ cascade of gene expression with some indication that these transcriptional patterns remain stable even in the presence of external stressors. However, direct analysis of transcription in P. falciparum blood-stage parasites obtained from the blood of infected patients suggests that parasite gene expression may be modulated by factors present in the in vivo environment of the host. The aim of this study was to examine changes in gene expression of the rodent malaria parasite, Plasmodium yoelii 17X, while varying the in vivo setting of replication.

Methods

Using P. yoelii 17X parasites replicating in vivo, differential gene expression in parasites isolated from individual mice, from independent infections, during ascending, peak and descending parasitaemia and in the presence and absence of host antibody responses was examined using P. yoelii DNA microarrays. A genome-wide analysis to identify coordinated changes in groups of genes associated with specific biological pathways was a primary focus, although an analysis of the expression patterns of two multi-gene families in P. yoelii, the yir and pyst-a families, was also completed.

Results

Across experimental conditions, transcription was surprisingly stable with little evidence for distinct transcriptional states or for consistent changes in specific pathways. Differential gene expression was greatest when comparing differences due to parasite load and/or host cell availability. However, the number of differentially expressed genes was generally low. Of genes that were differentially expressed, many involved biologically diverse pathways. There was little to no differential expression of members of the yir and pyst-a multigene families that encode polymorphic proteins associated with the membrane of infected erythrocytes. However, a relatively large number of these genes were expressed during blood-stage infection regardless of experimental condition.

Conclusions

Taken together, these results indicate that 1) P. yoelii gene expression remains stable in the presence of a changing host environment, and 2) concurrent expression of a large number of the polymorphic yir and pyst-a genes, rather than differential expression in response to specific host factors, may in itself limit the effectiveness of host immune responses.

Elevated levels of the Plasmodium yoelii homologue of macrophage migration inhibitory factor attenuate blood-stage malaria

The excessive production of proinflammatory cytokines plays a significant role in the pathogenesis of severe malaria. Mammalian macrophage migration inhibitory factor (MIF) (mMIF) is an immune mediator that promotes a sustained proinflammatory response by inhibiting the glucocorticoid-mediated downregulation of inflammation. In addition, Plasmodium parasites also encode a homologue of mammalian MIF that is expressed in asexual-stage parasites. We used the Plasmodium yoelii murine model to study the potential role of parasite-encoded MIF in the pathogenesis of malaria. Antibodies raised against purified, non-epitope-tagged P. yoelii MIF (PyMIF) were used to localize expression in trophozoite- and schizont-stage parasites and demonstrate extracellular release. In vitro, recombinant PyMIF was shown to actively induce the chemotaxis of macrophages but did not induce or enhance tumor necrosis factor alpha (TNF-α) production from peritoneal macrophages. To examine the role of parasite-derived PyMIF in vivo, two transgenic parasite lines that constitutively overexpress PyMIF were generated, one in a nonlethal P. yoelii 17X background [Py17X-MIF(+)] and the other in a lethal P. yoelii 17XL background [Py17XL-MIF(+)]. Challenge studies with transgenic parasites in mice showed that the increased expression of PyMIF resulted in a reduction in disease severity. Mice infected with Py17X-MIF(+) developed lower peak parasitemia levels than controls, while malaria-associated anemia was unaltered. Infection with Py17XL-MIF(+) resulted in a prolonged course of infection and a reduction in the overall mortality rate. Combined, the data indicate that parasite-derived MIF does not contribute significantly to immunopathology but, through its chemotactic ability toward macrophages, may attenuate disease and prolong infection of highly virulent parasite isolates.

High mobility group protein HMGB2 is a critical regulator of plasmodium oocyst development

The sexual cycle of Plasmodium is required for transmission of malaria from mosquitoes to mammals, but how parasites induce the expression of genes required for the sexual stages is not known. We disrupted the Plasmodium yoelii gene encoding high mobility group nuclear factor hmgb2, which encodes a DNA-binding protein potentially implicated in transcriptional regulation of malaria gene expression. We investigated its function in vivo in the vertebrate and invertebrate hosts. Deltapyhmgb2 parasites develop into gametocytes but have drastic impairment of oocyst formation. A global transcriptome analysis of the Deltapyhmgb2 parasites identified approximately 30 genes whose expression is down-regulated in the Deltapyhmgb2 parasites. These genes are conserved in all malaria species, and more than 90% of these genes show a peak of mRNA expression at the gametocyte stage. Surprisingly, the transcripts coding for the Plasmodium berghei orthologues of those genes are stored and translated in the ookinete stage. Therefore, sexual stage protein expression appears to be both transcriptionally and translationally regulated with Plasmodium HMGB2 acting as an important regulator of malaria sexual stage gene expression.

Comprehensive assessment of metabolic enzyme and transporter genes using the Affymetrix Targeted Genotyping System

The combined effects of multiple polymorphisms in several drug-metabolizing enzyme and transporter genes can contribute to considerable interindividual variation in drug disposition and response. Therefore, it has been of increasing interest to generate scalable, flexible and cost-effective technologies for large-scale genotyping of the drug-metabolizing enzyme and transporter genes. However, the number of drug-metabolizing enzyme and transporter gene variants exceeds the capacity of current technologies to comprehensively assess multiple polymorphisms in a single, multiplexed assay. The Targeted Genotyping System (Affymetrix, CA, USA) provides a solution to this challenge, by combining molecular inversion probe technology with universal microarrays to provide a method that is capable of analyzing thousands of variants in a single reaction, while remaining relatively insensitive to cross-reactivity between reaction components. This review will focus on the Targeted Genotyping System and how this technology was adapted to enable comprehensive analysis of drug-metabolizing enzyme and transporter gene polymorphisms.

Development and validation of a phosphorylated SMAD ex vivo stimulation assay

Assessing the pharmacodynamics (PD) of a potential therapeutic through the use of a downstream biomarker is essential. This is traditionally performed in the target tissue but limited volume and invasiveness of sampling pose challenges with solid tumours. Currently, there are several small molecule receptor kinase inhibitors and large molecule therapeutic antibodies in clinical trials that interfere with TGFbeta signalling to treat various forms of cancer. With the advent of these new therapies, there is a need for a surrogate tissue that is easily accessible and indicative of tumour response. We propose the use of an ex vivo TGFbeta1 stimulation of peripheral blood mononuclear cells (PBMCs) coupled with the measurement of phosphorylated SMAD2 (Sma/Mothers Against dpp, a downstream transcriptional activator) using a sandwich ELISA. TGFbeta is involved in many different cellular responses, such as proliferation, angiogenesis, migration, invasion and immunomodulation. SMAD2 and SMAD3 are phosphorylated as a result of the canonical cascade through ligand binding and receptor kinase activation. These phosphorylated SMADs (pSMAD) associate with SMAD4, a co-SMAD, and transcriptionally activate TGFbeta-mediated genes. This paper describes the novel method for measuring the downstream effects of inhibiting canonical TGFbeta signalling using ex vivo stimulation of surrogate tissue to predict tumour response. In addition, we present the assay validation rationale and data. This novel, validated assay can be used to gain insight into clinical trials regarding TGFbeta signal modulation by multiple inhibitor platforms for both large and small molecules.

The closed MTIP-myosin A-tail complex from the malaria parasite invasion machinery

The Myosin A-tail interacting protein (MTIP) of the malaria parasite links the actomyosin motor of the host cell invasion machinery to its inner membrane complex. We report here that at neutral pH Plasmodium falciparum MTIP in complex with Myosin A adopts a compact conformation, with its two domains completely surrounding the Myosin A-tail helix, dramatically different from previously observed extended MTIP structures. Crystallographic and mutagenesis studies show that H810 and K813 of Myosin A are key players in the formation of the compact MTIP:Myosin A complex. Only the unprotonated state of Myosin A-H810 is compatible with the compact complex. Most surprisingly, every side-chain atom of Myosin A-K813 is engaged in contacts with MTIP. While this side-chain was previously considered to prevent a compact conformation of MTIP with Myosin A, it actually appears to be essential for the formation of the compact complex. The hydrophobic pockets and adaptability seen in the available series of MTIP structures bodes well for the discovery of inhibitors of cell invasion by malaria parasites.

Multiplex assay for comprehensive genotyping of genes involved in drug metabolism, excretion, and transport

BACKGROUND

Drug metabolism is a multistep process by which the body disposes of xenobiotic agents such as therapeutic drugs. Genetic variation in the enzymes involved in this process can lead to variability in a patient's response to medication.

METHODS

We used molecular-inversion probe technology to develop a multiplex genotyping assay that can simultaneously test for 1227 genetic variants in 169 genes involved in drug metabolism, excretion, and transport. Within this larger set of variants, we performed analytical validation of a clinically defined core set of 165 variants in 27 genes to assess accuracy, imprecision, and dynamic range.

RESULTS

In a test set of 91 samples, genotyping accuracy for the core set probes was 99.8% for called genotypes, with a 1.2% no-call (NC) rate. The majority of the core set probes (133 of 165) had < or = 1 genotyping failure in the test set; a subset of 12 probes was responsible for the majority of failures (mainly NC). Genotyping results were reproducible upon repeat testing with overall within- and between-run variation of 1.1% and 1.4%, respectively-again, primarily NCs in a subset of probes. The assay showed stable genotyping results over a 6-fold range of input DNA.

CONCLUSIONS

This assay generates a comprehensive assessment of a patient's metabolic genotype and is a tool that can provide a more thorough understanding of patient-to-patient variability in pharmacokinetic responses to drugs.

Structure of the MTIP-MyoA complex, a key component of the malaria parasite invasion motor

The causative agents of malaria have developed a sophisticated machinery for entering multiple cell types in the human and insect hosts. In this machinery, a critical interaction occurs between the unusual myosin motor MyoA and the MyoA-tail Interacting Protein (MTIP). Here we present one crystal structure that shows three different conformations of Plasmodium MTIP, one of these in complex with the MyoA-tail, which reveal major conformational changes in the C-terminal domain of MTIP upon binding the MyoA-tail helix, thereby creating several hydrophobic pockets in MTIP that are the recipients of key hydrophobic side chains of MyoA. Because we also show that the MyoA helix is able to block parasite growth, this provides avenues for designing antimalarials.

Alteration in host cell tropism limits the efficacy of immunization with a surface protein of malaria merozoites

Immunization with Plasmodium yoelii merozoite surface protein-8 (PyMSP-8) has been shown to protect mice against lethal P. yoelii 17XL malaria. Here we demonstrate that PyMSP-8-specific antibodies preferentially suppress P. yoelii 17XL growth in mature erythrocytes compared to growth in reticulocytes and do not suppress the growth of nonlethal P. yoelii 17X, a parasite that primarily replicates in reticulocytes. The protection against normocyte-associated P. yoelii malaria parasites is mediated by antibodies that recognize conformational epitopes of PyMSP-8 that are nonpolymorphic. We examined changes in gene expression in reticulocyte-restricted P. yoelii 17XL parasites that escaped neutralization by PyMSP-8-specific antibodies using P. yoelii DNA microarrays. Of interest, Pymsp-8 gene expression decreased, while the expression of msp-1, msp-7, and several rhoptry protein genes increased. Breakthrough parasites also exhibited increases in the expression of a subset of yir and Pyst-a genes that are predicted to encode polymorphic antigens expressed on the surface of infected erythrocytes. These data suggest that changes in the expression of parasite proteins expressed on the merozoite surface, as well as the surface of infected erythrocytes, may alter host cell tropism and contribute to the ability of malaria parasites to evade merozoite-specific, neutralizing antibodies.

Precision profiling and components of variability analysis for Affymetrix microarray assays run in a clinical context

Although gene expression profiling using microarray technology is widely used in research environments, adoption of microarray testing in clinical laboratories is currently limited. In an attempt to determine how such assays would perform in a clinical laboratory, we evaluated the analytical variability of Affymetrix microarray probesets using two generations of human Affymetrix chips (U95Av2 and U133A). The study was designed to mimic potential clinical applications by using multiple operators, machines, and reagent lots, and by performing analyses throughout a period of several months. A mixed model analysis was used to evaluate the relative contributions of multiple factors to overall variability, including operator, instrument, run, cRNA/cDNA synthesis, and changes in reagent lots. Under these conditions, the average probeset coefficient of variation (CV) was relatively low for present probesets on both generations of chips (mean coefficient of variation, 21.9% and 27.2% for U95Av2 and U133A chips, respectively). The largest contribution to overall variation was chip-to-chip (residual) variability, which was responsible for between 40 to 60% of the total variability observed. Changes in individual reagent lots and instrumentation contributed very little to the overall variability. We conclude that the approach demonstrated here could be applied to clinical validation of Affymetrix-based assays and that the analytical precision of this technique is sufficient to answer many biological questions.

Gene therapy for lysosomal storage diseases

The lysosomal storage diseases are a family of inherited disorders usually caused by a deficiency in a single lysosomal enzyme, and are characterised by progressive intralysosomal storage in multiple cell types. Although individual syndromes can be uncommon, as a whole this family of diseases affects approximately 1 in 3,000 live births. The severity of disease can be variable, ranging from minimal evidence of lysosomal storage to widespread multi-system involvement and early mortality. Although the enzymatic defects responsible for most of these diseases are known, treatment options for the majority of these disorders are limited to supportive care and genetic counselling. Knowledge of the genetic defects underlying these diseases, coupled with advances in the fields of gene transfer and expression, provide an opportunity to utilise gene therapy strategies in order to treat these disorders. Here we provide a description of the biochemical and molecular basis of gene therapy for lysosomal storage diseases, as well as an overview of some of the in vitro and in vivo studies that have been performed.

Overestimation of HDL-cholesterol using a homogeneous "direct" assay

Direct HDL-cholesterol (HDLc) assays have several advantages over other assays that are more laborious and time-consuming. A recent College of American Pathologists (CAP) report indicates that at least 385 Beckman LX-20 analyzers use the selective detergent (homogeneous or direct) method for analyzing HDLc. There is no published evaluation of direct HDLc assays on the Beckman platform. Here we report our evaluation of a direct HDLc assay marketed by Beckman for the Beckman LX-20 analyzers. In general, the assay performed well; however, the total error was not within National Cholesterol Education Program (NCEP) guidelines. This was largely because of a significant positive bias that appeared to be due, at least in part, to triglycerides. This bias was worse at HDLc concentrations <40 mg/dL, which may make it difficult to identify a low HDLc concentration and consequently an increased risk for cardiovascular disease (CVD).

Regulation by phosphorylation of Pho81p, a cyclin-dependent kinase inhibitor in Saccharomyces cerevisiae

Cyclins, cyclin-dependent kinases (CDK) and their inhibitors play a critical role in many biological processes. In yeast, the ankyrin repeat protein Pho81p, by being an inhibitor of the Pho85p-Pho80p cyclin-dependent protein kinase complex, transcriptionally regulates the production of repressible acid phosphatase, encoded by the PHO5 gene. Recent studies in our laboratory showed that Pho81p is phosphorylated by the Pho80p-Pho85p CDK complex in vitro; and, to determine the significance of the phosphorylation, we used site-directed mutagenesis to alter the potential phosphorylation sites for this kinase complex. The resulting mutations were introduced into a yeast strain containing a deletion of PHO81 and the effect of the mutation on PHO5 expression was assayed. Results suggest that phosphorylation of particular residues within Pho81p is crucial for its activity as an inhibitor. Studies using a green fluorescent protein-Pho81p fusion and Western analysis indicate that the localization and half-life of the mutants are similar to wild-type Pho81 proteins. However, an in vivo binding assay indicates that the mutant Pho81p is deficient in binding to the Pho80p-Pho85p kinase complex. These findings support the observation that the mutant fails to inhibit kinase activity in low phosphate. These studies provide insight into the mechanism of regulation of CDK inhibitor activity.

Overview of adeno-associated viral vectors

The use of adeno-associated virus (AAV) as a gene transfer vector has been steadily increasing over the past several years. AAV vectors have been particularly useful for applications where sustained gene expression is required. Prolonged in vivo expression following AAV treatment has been seen in the liver (1,2), brain (3,4), skeletal muscle (5,6), lung (7,8), and hematopoietic stem cells (9,10) of animal models. Therapeutic benefit from AAV treatment has been shown in a number of preclinical models of disease, including animal models of coagulopathies (11,12), lysosomal storage diseases (13,14), vision defects (15,16), and amino acid disorders. Clinical trials using AAV for the treatment of hemophilia B have begun, and early reports from these trials have been promising. In this introductory chapter to AAV, we will provide a brief overview of the molecular biology of this virus, an overview of methods of vector production, and a brief summary of the use of alternate AAV serotypes. The following chapters will then focus on specific methods and techniques for AAV transduction of the organs listed previously.

Members of the merozoite surface protein 7 family with similar expression patterns differ in ability to protect against Plasmodium yoelii malaria

Previously, we described the isolation of the Plasmodium yoelii sequence-related molecules P. yoelii MSP-7 (merozoite surface protein 7) and P. yoelii MSRP-2 (MSP-7-related protein 2) by their ability to interact with the amino-terminal end of P. yoelii MSP-1 in a yeast two-hybrid system. One of these molecules was the homologue of Plasmodium falciparum MSP-7, which was biochemically isolated as part of the shed MSP-1 complex. In the present study, with antibodies directed against recombinant proteins, immunoprecipitation analyses of the rodent system demonstrated that both P. yoelii MSP-7 and P. yoelii MSRP-2 could be isolated from parasite lysates and from parasite culture supernatants. Immunofluorescence studies colocalized P. yoelii MSP-7 and P. yoelii MSRP-2 with the amino-terminal portion of MSP-1 and with each other on the surface of schizonts. Immunization with P. yoelii MSRP-2 but not P. yoelii MSP-7 protected mice against a lethal infection with P. yoelii strain 17XL. These results establish that both P. yoelii MSP-7 and P. yoelii MSRP-2 are expressed on the surface of merozoites and released from the parasite and that P. yoelii MSRP-2 may be the target of a protective immune response.

A Co-ligand Complex Anchors Plasmodium falciparum Merozoites to the Erythrocyte Invasion Receptor Band 3

In Plasmodium falciparum malaria, erythrocyte invasion by circulating merozoites may occur via two distinct pathways involving either a sialic acid-dependent or -independent mechanism. Earlier, we identified two nonglycosylated exofacial regions of erythrocyte band 3 termed 5ABC and 6A as an important host receptor in the sialic acid-independent invasion pathway. 5ABC, a major segment of this receptor, interacts with the 42-kDa processing product of merozoite surface protein 1 (MSP1(42)) through its 19-kDa C-terminal domain. Here, we show that two regions of merozoite surface protein 9 (MSP9), also known as acidic basic repeat antigen, interact directly with 5ABC during erythrocyte invasion by P. falciparum. Native MSP9 as well as recombinant polypeptides derived from two regions of MSP9 (MSP9/Delta1 and MSP9/Delta2) interacted with both 5ABC and intact erythrocytes. Soluble 5ABC added to the assay mixture drastically diminished the binding of MSP9 to erythrocytes. Recombinant MSP9/Delta1 and MSP9/Delta2 present in the culture medium blocked P. falciparum reinvasion into erythrocytes in vitro. Native MSP9 and MSP1(42), the two ligands binding to the 5ABC receptor, existed as a stable complex. Our results establish a novel concept wherein the merozoite exploits a specific complex of co-ligands on its surface to target a single erythrocyte receptor during invasion. This new paradigm poses a new challenge in the development of a vaccine for blood stage malaria.

AAV-mediated gene transfer to the liver

The liver is a frequent target of gene-transfer experiments, because of its central role in many metabolic and synthetic pathways. For applications where prolonged expression of genes in the liver is required, adeno-associated virus (AAV) has proven to be an effective tool for in vivo gene transfer. High-level, persistent hepatic expression has been achieved in a number of experimental systems following a single treatment with AAV in murine and larger animal models. This prolonged expression is particularly useful for the treatment of genetic diseases such as the inborn errors of metabolism, where lifelong expression of the deficient enzyme may be required. Therapeutic benefits using AAV vectors have been demonstrated in animal models of amino acid disorders, lysosomal storage diseases, and coagulopathies (3-5), and Phase I clinical trials are proposed for the treatment of hemophilia B (6). Gene transfer to the murine liver using AAV is achieved by intravenous (iv) injection of recombinant virus, either via a peripheral or portal vein. The liver is the primary organ transduced following intravenous injection of AAV, although other tissues such as heart and lung may also take up virus to a lesser extent when peripheral injection sites are used (7). Portal-vein injection can reduce the amount of extra-hepatic transduction, and allows a larger dose of virus to be delivered to the liver. However, this technique requires surgical expertise, and can only be performed on adult mice.

Polydrug fatality involving metaxalone

A 29-year old female with a history of depression was found dead in a hotel room. The death scene investigation found empty pill bottles and an empty liter bottle of wine. Metaxalone, a centrally acting muscle relaxant, along with citalopram, ethanol, and chlorpheniramine were identified in the postmortem samples and quantitated by gas chromatography-mass spectrometry. The concentration of metaxalone in femoral vein blood was 39 mg/L. The heart blood concentration was 54 mg/L. Femoral vein blood concentrations of citalopram and chlorpheniramine were 0.77 mg/L and 0.04 mg/L, respectively. Ethanol levels were 0.13 g/dL in vitreous and 0.08 g/dL in heart blood. Other tissue samples were also analyzed. The authors consider the metaxalone concentrations toxic and potentially fatal. The citalopram concentrations were lower than those reported in fatal cases for this drug alone. Death was ascribed to polydrug abuse/overdose with metaxalone a major contributor. This represents the first reported case to our knowledge in which a metaxalone overdose significantly contributed to death.

Myosin A tail domain interacting protein (MTIP) localizes to the inner membrane complex of Plasmodium sporozoites

Apicomplexan host cell invasion and gliding motility depend on the parasite's actomyosin system located beneath the plasma membrane of invasive stages. Myosin A (MyoA), a class XIV unconventional myosin, is the motor protein. A model has been proposed to explain how the actomyosin motor operates but little is known about the components, topology and connectivity of the motor complex. Using the MyoA neck and tail domain as bait in a yeast two-hybrid screen we identified MTIP, a novel 24 kDa protein that interacts with MyoA. Deletion analysis shows that the 15 amino-acid C-terminal tail domain of MyoA, rather than the neck domain, specifically interacts with MTIP. In Plasmodium sporozoites MTIP localizes to the inner membrane complex (IMC), where it is found clustered with MyoA. The data support a model for apicomplexan motility and invasion in which the MyoA motor protein is associated via its tail domain with MTIP, immobilizing it at the outer IMC membrane. The head domain of the immobilized MyoA moves actin filaments that, directly or via a bridging protein, connect to the cytoplasmic domain of a transmembrane protein of the TRAP family. The actin/TRAP complex is then redistributed by the stationary MyoA from the anterior to the posterior end of the zoite, leading to its forward movement on a substrate or to penetration of a host cell.

A multigene family that interacts with the amino terminus of plasmodium MSP-1 identified using the yeast two-hybrid system

Merozoite surface protein 1 (MSP-1) is a high-molecular-weight protein expressed on the surface of the malaria merozoite in a noncovalent complex with other protein molecules. MSP-1 undergoes a series of proteolytic processing events, but no precise biological role for the various proteolytic fragments of MSP-1 or for the additional proteins present in the complex is known. Through the use of the yeast two-hybrid system, we have isolated genes encoding proteins that interact with a region of the amino-terminal proteolytic fragment of MSP-1 from the mouse parasite Plasmodium yoelii. This analysis has led to the isolation of two sequence-related molecules, one of which is the P. yoelii homologue of MSP-7 originally described in Plasmodium falciparum. BLAST analysis of the P. falciparum database has revealed that there are six related protein molecules present in this species encoded near each other on chromosome 13. In P. falciparum, we designated these molecules MSRP-1 to -5. Analysis of the P. yoelii database indicates a similar chromosomal organization for the two genes in the mouse parasite species. The three P. falciparum sequences with the highest degree of homology to the P. yoelii sequences isolated in the two-hybrid screen have been characterized at the molecular level (MSRP-1 to -3). Expression analysis indicated that the mRNAs are expressed at various levels in the different asexual stages. Immunofluorescence studies colocalized the expression of the MSRP molecules and the amino-terminal portion of MSP-1 to the surfaces of trophozoites. In vitro binding experiments confirmed the interaction between MSRP-1, MSRP-2, and the amino-terminal region of P. falciparum MSP-1.

Adeno-associated virus-mediated gene transfer to the neonatal brain

For many metabolic diseases, early treatment is necessary to prevent irreversible developmental damage. This is particularly true for childhood diseases that affect the central nervous system (CNS). The development of effective techniques for gene transfer to the neonatal brain would provide a new set of therapeutic options for many of these disorders. Vectors based on adeno-associated virus (AAV) have shown promise as agents for neonatal CNS transduction. In preclinical animal models, a single treatment with AAV vectors at birth has been shown to produce persistent CNS expression of transduced genes into adulthood. Transduction of the neonatal brain has been accomplished by a variety of methods, including direct intraparenchymal injection, intraventricular infusion, and intravenous administration. Of these methods, intraparenchymal injection provides the highest levels of localized activity, while intraventricular infusion results in a more widespread distribution of activity when performed in the neonate. Here we describe a method for direct, intraparenchymal injection of AAV into the neonatal brain. This technique provides a method for investigators to evaluate the effects of in vivo expression of exogenous genes on the process of early brain development.

Evaluation of a no-pretreatment cyclosporin A assay on the Dade Behring dimension RxL clinical chemistry analyzer

BACKGROUND

Monitoring whole-blood concentrations of cyclosporin A (CsA) is common practice in the management of solid organ and bone marrow transplant recipients. In a multicenter study we evaluated a new, direct (no pretreatment) CsA assay on the Dade Behring Dimension RxL system and compared results with those from the Abbott TDx CsA immunoassay and a HPLC method.

METHODS

Whole-blood samples from heart (n = 111; 35 patients), liver (n = 201; 44 patients), kidney (n = 279; 65 patients), and miscellaneous organ (n = 77; 12 lung, 12 bone marrow, 5 kidney/pancreas, and 1 pancreas patient) recipients were obtained from patient populations of the participating institutions. Routine clinical monitoring of CsA was performed using either the TDx method or HPLC.

RESULTS

The minimum detectable concentration of CsA averaged 9.4 microg/L, and the lower limit of quantification was 30 microg/L. The method was linear from 30 to 500 microg/L. Cross-reactivity with seven different CsA metabolites ranged from 0.0% to 5.7% for the Dimension RxL assay compared with 0.4-15.9% for the TDx assay. Total imprecision (CV) averaged 6.2%, and within-run imprecision averaged 4.9%. Passing-Bablok linear regression analyses of all samples from two sites yielded the following: RxL = 0.81 x TDx - 16.8; and RxL = 1.12 x HPLC - 1.7.

CONCLUSIONS

The Dade Behring CsA assay for the random-access Dimension platform offers adequate performance characteristics for routine clinical use, does not require a manual pretreatment step, and demonstrates less cross-reactivity with CsA metabolites than another commonly used immunoassay.

Evaluation of a No-Pretreatment Cyclosporin A Assay on the Dade Behring Dimension RxL Clinical Chemistry Analyzer

Background: Monitoring whole-blood concentrations of cyclosporin A (CsA) is common practice in the management of solid organ and bone marrow transplant recipients. In a multicenter study we evaluated a new, direct (no pretreatment) CsA assay on the Dade Behring Dimension RxLTM system and compared results with those from the Abbott TDx CsA immunoassay and a HPLC method.

Methods: Whole-blood samples from heart (n = 111; 35 patients), liver (n = 201; 44 patients), kidney (n = 279; 65 patients), and miscellaneous organ (n = 77; 12 lung, 12 bone marrow, 5 kidney/pancreas, and 1 pancreas patient) recipients were obtained from patient populations of the participating institutions. Routine clinical monitoring of CsA was performed using either the TDx method or HPLC.

Results: The minimum detectable concentration of CsA averaged 9.4 μg/L, and the lower limit of quantification was 30 μg/L. The method was linear from 30 to 500 μg/L. Cross-reactivity with seven different CsA metabolites ranged from 0.0% to 5.7% for the Dimension RxL assay compared with 0.4–15.9% for the TDx assay. Total imprecision (CV) averaged 6.2%, and within-run imprecision averaged 4.9%. Passing–Bablok linear regression analyses of all samples from two sites yielded the following: RxL = 0.81 × TDx − 16.8; and RxL = 1.12 × HPLC − 1.7.

Conclusions: The Dade Behring CsA assay for the random-access Dimension platform offers adequate performance characteristics for routine clinical use, does not require a manual pretreatment step, and demonstrates less cross-reactivity with CsA metabolites than another commonly used immunoassay.

Comparison of non-diglyceride- and diglyceride-based assays for pancreatic lipase activity

Pancreatic lipase is produced and stored in pancreatic acinar cells, and is normally secreted into the duct system. In disorders that cause pancreatic damage, pancreatic lipase enters the circulation, and serum lipase activity becomes useful in the diagnosis and evaluation of pancreatitis. During the last decade, many lipase assays have used the Imamura method, in which a series of enzymatic reactions utilizing a diglyceride substrate leads to the formation of a colorimetrically detected product. Historically, this method has been prone to significant interference from various substances, including glycerol itself. In the light of these limitations, we evaluated an automated enzymatic rate assay that uses a non-diglyceride-based, pancreatic lipase-specific substrate. Precision, linearity, and potential interference were assessed, and when compared to the Imamura method, the non-diglyceride-based assay exhibited a slope of 0.475, y-intercept of 15.89, r-value of 0.9516, and S(y,x) of 12.96. Similar results were also observed when the two assays were compared using samples with markedly elevated creatinine levels. Between-day coefficients of variance (CVs) ranged from 5.0% to 5.5%, which compared well with the diglyceride-based method, and linearity spanned a range of 3-156 U/L. Evaluation of over 2,000 patient results collected during a 6-month period suggested that the manufacturer's upper reference limit of 51 U/L may be too conservative. No significant interference was identified with bilirubin, triglyceride, or glycerol itself, and significant interference from hemoglobin was observed only at concentrations of 116 mg/dL or greater. As a result, the non-diglyceride-based method provides an acceptable alternative for the routine laboratory measurement of lipase activity.

Interaction between two domains of the P. yoelii MSP-1 protein detected using the yeast two-hybrid system

Several model systems of plasmodia have demonstrated the potential of the merozoite surface protein, MSP-1, to induce protective immunity. However, little is known about the function of this protein or its interaction with other surface molecules that may also serve as immunological targets. To identify potentially significant inter- and intra-molecular interactions involving MSP-1, we have utilized the yeast two-hybrid system. A cDNA activation domain library was constructed from the erythrocytic stages of the murine malarial parasite Plasmodium yoelii yoelii 17XL. A 795 bp region of Py17XL MSP-1 (bait), homologous to the Plasmodium falciparum MSP1(33) fragment, was inserted into a Gal4p DNA binding domain vector and used to screen the activation domain library (target). Several randomly selected clones that demonstrated bait-target interaction were found to express overlapping regions of Py17XL MSP-1. Deletion constructs further localized the peptide fragments retaining interaction indicating that a region within the MSP-1(38) fragment interacts with the MSP-1 bait domain. Subsequent studies confirmed this interaction, as both peptides were co-precipitated from cell lysate by a peptide tag-specific antibody. It was observed that the interaction of these two fragments significantly increased the half-life of the MSP-1(38) within yeast cells. The specific interaction described here demonstrates the potential of this approach to elucidate additional inter- or intra-molecular interactions of Py17XL MSP1 and other malarial proteins.

Prevention of systemic clinical disease in MPS VII mice following AAV-mediated neonatal gene transfer

For many inborn errors of metabolism, early treatment is critical to prevent long-term developmental sequelae. We have previously shown that systemic treatment of neonatal mucopolysaccharidosis type VII (MPS VII) mice with recombinant adeno-associated virus (AAV) vectors results in relatively long-term expression of beta-glucuronidase (GUSB) in multiple tissues, and a reduction in lysosomal storage. Here, we demonstrate that therapeutic levels of enzyme persist for at least 1 year following a single intravenous injection of virus in neonatal MPS VII mice. The level and distribution of GUSB expression achieved is sufficient to prevent the development of many aspects of clinical disease over the life of the animal. Following treatment, bone lengths, weights and retinal function were maintained at nearly normal levels throughout the life of the animal. In addition, significant improvements in survival and auditory function were seen in AAV-treated MPS VII mice when compared with untreated mutant siblings. These data suggest that AAV-mediated gene transfer in the neonatal period can lead to prevention of many of the clinical symptoms associated with MPS VII in the murine model of this disease.

Intracranial injection of recombinant adeno-associated virus improves cognitive function in a murine model of mucopolysaccharidosis type VII

Mucopolysaccharidosis type VII (MPS VII) is a lysosomal storage disease caused by the lack of beta-glucuronidase (GUSB) activity. GUSB deficiency leads to the progressive accumulation of undegraded glycosaminoglycans (GAGs) in cells of most tissues, including the brain, and is associated with mental retardation. Reduction of lysosomal storage in the central nervous system and prevention of cognitive dysfunction may require intracranial delivery of a therapeutic agent during the newborn period that provides a continuous source of GUSB. Therefore, we injected recombinant adeno-associated virus encoding human GUSB into both the anterior cortex and the hippocampus of newborn MPS VII mice. Total GUSB activity in the brain approached normal levels by 18 weeks. Although GUSB activity was concentrated near the injection sites, lysosomal distension was reduced in most areas of the brain. In addition to histopathologic evidence of GAG reduction, the previously undescribed accumulation of GM2 and GM3 gangliosides in the brain was also prevented. Furthermore, GUSB expression and reduced lysosomal distension correlated with improvements in cognitive function as measured in the Morris Water Maze test. These findings indicate that localized overexpression of GUSB has positive effects on the pathology and cognitive function and does not have overt toxicity.

Novel polymorphism in the FMR1 gene resulting in a "pseudodeletion" of FMR1 in a commonly used fragile X assay

The fragile X syndrome is the most commonly inherited cause of mental retardation. Genetic diagnosis of this disease relies on the detection of triplet repeat expansion in the FMR1 gene on the X chromosome. Although the majority of disease in fragile X patients is due to mutations involving triplet repeat expansion, deletion of various portions of FMR1 has also been described in association with the fragile X syndrome. Here we describe a rare polymorphism in the noncoding region of FMR1 that mimics detection of a deletion in a commonly used assay for fragile X syndrome, which can result in misdiagnosis of the disease.

Abnormal immune function in vivo in a murine model of lysosomal storage disease

Lysosomal storage diseases are a class of inborn errors of metabolism that lead to widespread disease in multiple tissues. The murine model of mucopolysaccharidosis type VII (MPS VII) closely parallels the human syndrome and has been extensively used to investigate the natural history and therapeutic strategies for lysosomal storage diseases in general. Here we demonstrate a previously undescribed immune defect in the MPS VII mouse. Although the normal populations of cells are present in lymph nodes of these mice, MPS VII mice show a blunted T cell proliferative response and decreased antibody production after immunization with antigens. One mechanism of this defect is ineffective processing of protein antigens, as responses to peptide antigens are normal. This phenotype is presumably caused by the lysosomal disorder, as the defect can be corrected in vivo by direct enzyme replacement therapy. These findings have implications for the use of this animal model, and may have clinical significance for other, more-common lysosomal storage diseases.

Neonatal gene transfer leads to widespread correction of pathology in a murine model of lysosomal storage disease

For many inborn errors of metabolism, early treatment is critical to prevent long-term developmental sequelae. We have used a gene-therapy approach to demonstrate this concept in a murine model of mucopolysaccharidosis type VII (MPS VII). Newborn MPS VII mice received a single intravenous injection with 5.4 x 10(6) infectious units of recombinant adeno-associated virus encoding the human beta-glucuronidase (GUSB) cDNA. Therapeutic levels of GUSB expression were achieved by 1 week of age in liver, heart, lung, spleen, kidney, brain, and retina. GUSB expression persisted in most organs for the 16-week duration of the study at levels sufficient to either reduce or prevent completely lysosomal storage. Of particular significance, neurons, microglia, and meninges of the central nervous system were virtually cleared of disease. In addition, neonatal treatment of MPS VII mice provided access to the central nervous system via an intravenous route, avoiding a more invasive procedure later in life. These data suggest that gene transfer mediated by adeno-associated virus can achieve therapeutically relevant levels of enzyme very early in life and that the rapid growth and differentiation of tissues does not limit long-term expression.