Functional 3'-UTR Variants Identify Regulatory Mechanisms Impacting Alcohol Use Disorder and Related Traits

Although genome-wide association studies (GWAS) have identified loci associated with alcohol consumption and alcohol use disorder (AUD), they do not identify which variants are functional. To approach this, we evaluated the impact of variants in 3' untranslated regions (3'-UTRs) of genes in loci associated with substance use and neurological disorders using a massively parallel reporter assay (MPRA) in neuroblastoma and microglia cells. Functionally impactful variants explained a higher proportion of heritability of alcohol traits than non-functional variants. We identified genes whose 3'UTR activities are associated with AUD and alcohol consumption by combining variant effects from MPRA with GWAS results. We examined their effects by evaluating gene expression after CRISPR inhibition of neuronal cells and stratifying brain tissue samples by MPRA-derived 3'-UTR activity. A pathway analysis of differentially expressed genes identified inflammation response pathways. These analyses suggest that variation in response to inflammation contributes to the propensity to increase alcohol consumption.

Definitive Radiotherapy for Oligometastatic and Oligoprogressive Thyroid Cancer

PURPOSE/OBJECTIVE(S)

Local consolidative radiotherapy (LCT) for oligometastatic disease is a promising paradigm improving outcomes for various malignancies but has been underexplored for metastatic thyroid cancer. We hypothesize that LCT to distant sites with definitive RT doses can yield favorable outcomes and defer systemic therapy escalation for these patients.

MATERIALS/METHODS

We reviewed 96 thyroid cancer patients who received 175 LCT courses from 2010-2022 to 228 metastatic sites, including: thorax (45%), bone (40%), brain (6%), head/neck (5%), and abdomen (3%). Common prescriptions were 50-55Gy/4-5fxs or 56-70Gy/8-10fxs for lung; 52.5-60Gy/15fxs for mediastinum; and 18-24Gy/1fx or 27-30Gy/3fxs for bone. RECIST v1.1 and CTCAE v5.0 were used to define progression and toxicities, respectively. Outcomes were evaluated via Kaplan-Meier and associations examined via Cox proportional hazards modeling.

RESULTS

Median age was 63 years (range: 26-92), with 62 oligometastatic cases (total 1-5 sites) and 34 oligoprogressive (with 1-5 growing sites). Primary disease was controlled in all patients, with 39% receiving post-op RT and 66% prior RAI. Histologies included papillary (40%), anaplastic (25%), follicular (12%), medullary (9%), Hurthle (7%), and poorly-differentiated (7%). Median time from initial diagnosis to LCT was 3 yrs (IQR 1-8), and median follow-up from 1st LCT was 21 mos (IQR 9-51). Patients received an average 2 LCT courses (range 1-8) treating 1-4 sites. Median survival (OS) from 1st LCT was 9 yrs (95% CI = 5-14). On multivariable analysis (MVA), worse OS was associated with anaplastic histology (HR 4.6, p<.01), but longer OS was associated with prior RAI (HR 0.33, p = .02) and oligometastatic disease (HR 0.3, p = .01). For anaplastic histology, median OS was 1.2 years vs. 9.3 years for non-anaplastic; 3-yr OS was 36% vs. 88% (log-rank, p<.01). Five-year OS for oligometastatic cases was 75% vs 53% for oligoprogressive (log-rank, p = .04). Median progression free survival (PFS) from 1st LCT was 15.5 mos (95% C I = 11-20). On MVA for all LCT courses, time to any progression (TTP) was negatively associated with anaplastic histology (HR 1.7, p = .02) and 2nd or higher LCT course (HR 1.45, p = .05), but favorably associated with thoracic site (HR 0.49, p<.01). Following later LCT courses, median TTP was 11 mos vs 17 mos for initial LCT course (log-rank, p = .03). After LCT to lung/chest, TTP was 18.6 mos vs 9.5 mos for non-thoracic sites (log-rank, p<.01). Only 6% of failures occurred at previously treated lesions. Most LCT courses (67%) were without ongoing chemotherapy, while 25% entailed continuing the same regimen and 9% had planned treatment post-RT. There were 2 Grade 3 toxicities (pneumonitis and esophagitis) and no Grade 4-5 events.

CONCLUSION

With high local control rates and minimal toxicity, LCT can be a feasible strategy to defer systemic therapy escalation for oligometastatic and oligoprogressive thyroid cancer.

Comorbidities and Their Impact on Treatment Tolerance and Outcome in Elderly NSCLC Patients Treated with Concurrent Chemoradiation Using Proton or Photon Followed by Immunotherapy

PURPOSE/OBJECTIVE(S)

To investigate comorbidities and their impact on treatment tolerance and survival for elderly NSCLC patients treated with concurrent chemoradiation using proton beam therapy (PBT) or intensity modulated radiation therapy (IMRT) followed by immunotherapy (IO).

MATERIALS/METHODS

This is a retrospective study in senior patients (≥ 65 years) with inoperable locally advanced- NSCLC (LA-NSCLC) who received concurrent chemoradiation (CRT) therapy followed by adjuvant IO. Comorbidities are listed in table 1 and scored according to hazard ratios (HRs) of death. Treatment tolerance and comorbidities were compared between modalities using Fisher's exact test. Association between comorbidities and treatment tolerance was analyzed using logistic regression; association between comorbidities and survival was analyzed by Cox proportional hazards regression.

RESULTS

Total 218 patients were included with median age of 72 (range 65-86) years. Fifty-three (24.3%) were PBT and 165 (75.7%) were IMRT. Majority patients were white ethnics, had stage III adenocarcinoma disease and good performance score, and received RT dose 60-66 Gy. The median follow-up time for the whole group was 23 months. A 97% of patients had ≥1, and 62% had ≥4 comorbidities. The combined comorbidity scores ranged from 0 to 25. No significant difference in comorbidities between modalities except IMRT had more patients with COPD (36% vs. 51%, p = 0.047). Rates of hospitalization and ER visit during CRT+IO were 28% and 5%, respectively. Rates of IO discontinuation and interruption were 55% and 8%, respectively. Patients received >6 months IO had significantly lower risk of death (HR: 0.25, p<0.001). No significant difference in treatment tolerance between modalities. In multivariable analysis, atrial fibrillation, pulmonary disease, and depression were the comorbidities associated with hospitalization during CRT+IO (p<0.05); dementia was the comorbidity associated with IO interruption (p = 0.042); heart failure, COPD, asthma, osteoporosis and HIV were the comorbidities associated with poor OS (p<0.05). Combined comorbidity score was associated with OS with HR of 1.13 (p<0.001) with adjustment of race, GTV and induction chemotherapy.

CONCLUSION

Comorbidities were associated with hospitalization and IO interruption during the whole course of CRT and IO therapy, with increased IO discontinuation which negatively impacted survival. Evaluating and scoring comorbidities at diagnosis could be a useful method to predict risk of death before treatment start.

RNA alternative splicing impacts the risk for alcohol use disorder

Alcohol use disorder (AUD) is a complex genetic disorder characterized by problems arising from excessive alcohol consumption. Identifying functional genetic variations that contribute to risk for AUD is a major goal. Alternative splicing of RNA mediates the flow of genetic information from DNA to gene expression and expands proteome diversity. We asked whether alternative splicing could be a risk factor for AUD. Herein, we used a Mendelian randomization (MR)-based approach to identify skipped exons (the predominant splicing event in brain) that contribute to AUD risk. Genotypes and RNA-seq data from the CommonMind Consortium were used as the training dataset to develop predictive models linking individual genotypes to exon skipping in the prefrontal cortex. We applied these models to data from the Collaborative Studies on Genetics of Alcoholism to examine the association between the imputed cis-regulated splicing outcome and the AUD-related traits. We identified 27 exon skipping events that were predicted to affect AUD risk; six of these were replicated in the Australian Twin-family Study of Alcohol Use Disorder. Their host genes are DRC1, ELOVL7, LINC00665, NSUN4, SRRM2 and TBC1D5. The genes downstream of these splicing events are enriched in neuroimmune pathways. The MR-inferred impacts of the ELOVL7 skipped exon on AUD risk was further supported in four additional large-scale genome-wide association studies. Additionally, this exon contributed to changes of gray matter volumes in multiple brain regions, including the visual cortex known to be involved in AUD. In conclusion, this study provides strong evidence that RNA alternative splicing impacts the susceptibility to AUD and adds new information on AUD-relevant genes and pathways. Our framework is also applicable to other types of splicing events and to other complex genetic disorders.

Allele-specific expression and high-throughput reporter assay reveal functional genetic variants associated with alcohol use disorders

Genome-wide association studies (GWAS) of complex traits, such as alcohol use disorders (AUD), usually identify variants in non-coding regions and cannot by themselves distinguish whether the associated variants are functional or in linkage disequilibrium with the functional variants. Transcriptome studies can identify genes whose expression differs between alcoholics and controls. To test which variants associated with AUD may cause expression differences, we integrated data from deep RNA-seq and GWAS of four postmortem brain regions from 30 subjects with AUD and 30 controls to analyze allele-specific expression (ASE). We identified 88 genes with differential ASE in subjects with AUD compared to controls. Next, to test one potential mechanism contributing to the differential ASE, we analyzed single nucleotide polymorphisms (SNPs) in the 3' untranslated regions (3'UTR) of these genes. Of the 88 genes with differential ASE, 61 genes contained 437 SNPs in the 3'UTR with at least one heterozygote among the subjects studied. Using a modified PASSPORT-seq (parallel assessment of polymorphisms in miRNA target-sites by sequencing) assay, we identified 25 SNPs that affected RNA levels in a consistent manner in two neuroblastoma cell lines, SH-SY5Y and SK-N-BE(2). Many of these SNPs are in binding sites of miRNAs and RNA-binding proteins, indicating that these SNPs are likely causal variants of AUD-associated differential ASE. In sum, we demonstrate that a combination of computational and experimental approaches provides a powerful strategy to uncover functionally relevant variants associated with the risk for AUD.

Identification of Functional Genetic Variants Associated With Alcohol Dependence and Related Phenotypes Using a High-Throughput Assay

BACKGROUND

Genome-wide association studies (GWAS) of alcohol dependence (AD) and related phenotypes have identified multiple loci, but the functional variants underlying the loci have in most cases not been identified. Noncoding variants can influence phenotype by affecting gene expression; for example, variants in the 3' untranslated regions (3'UTR) can affect gene expression posttranscriptionally.

METHODS

We adapted a high-throughput assay known as PASSPORT-seq (parallel assessment of polymorphisms in miRNA target sites by sequencing) to identify among variants associated with AD and related phenotypes those that cause differential expression in neuronal cell lines. Based upon meta-analyses of alcohol-related traits in African American and European Americans in the Collaborative Study on the Genetics of Alcoholism, we tested 296 single nucleotide polymorphisms (SNPs with meta-analysis p values ≤ 0.001) that were located in 3'UTRs.

RESULTS

We identified 60 SNPs that affected gene expression (false discovery rate [FDR] < 0.05) in SH-SY5Y cells and 92 that affected expression in SK-N-BE(2) cells. Among these, 30 SNPs altered RNA levels in the same direction in both cell lines. Many of these SNPs reside in the binding sites of miRNAs and RNA-binding proteins and are expression quantitative trait loci of genes including KIF6,FRMD4A,CADM2,ADD2,PLK2, and GAS7.

CONCLUSION

The SNPs identified in the PASSPORT-seq assay are functional variants that might affect the risk for AD and related phenotypes. Our study provides insights into gene regulation in AD and demonstrates the value of PASSPORT-seq as a tool to screen genetic variants in GWAS loci for one potential mechanism of action.

Low Incidence of Antibodies to Recombinant Human Tissue-Type Plasminogen Activator in Treated Patients

Sera from over 1,600 patients who received recombinant human tissue plasminogen activator (rt-PA) during clinical trials were assessed for the presence of antibodies to this therapeutic agent. The rt-PA was administered by a variety of dosage regimens for several different indications. Two different forms of rt-PA were used; one was a predominantly two chain form, and the other was a predominantly one chain form. A sensitive radioimmunoprecipitation assay was used to measure antibodies to rt-PA in patients’ serum before and after treatment. Of 932 patients tested with this assay, 929 were negative for antibodies to t-PA. Three patients developed low titers after treatment. Additional serum samples were obtained from these three patients within 2 years after rt-PA therapy and were negative for antibodies to t-PA. With the limited number of positive samples, no correlation could be found with dose or type of rt-PA, dosing regimen or clinical diagnosis. The virtual absence of antibody formation was confirmed in an additional 754 patients using a novel competitive two-site ELISA. It can be concluded that a single infusion of rt-PA was virtually unassociated with antibody formation, suggesting that repeat treatments could be given when necessary without the risk of immunologic complications as are seen with streptokinase or its derivatives.

D-Phe-Pro-Arg-Chloromethylketone: Its Potential Use in Inhibiting the Formation of In Vitro Artifacts in Blood Collected During Tissue-Type Plasminogen Activator Thrombolytic Therapy

In vitro artifacts due to proteolysis may occur in blood samples containing recombinant tissue-type plasminogen activator (rt-PA) due to continued activation of plasminogen to plasmin by rt-PA. The aim of this study was to identify a rapid inhibitor of rt-PA that would not interfere in assays designed to monitor thrombolytic events.

When rt-PA was added at 5 μg/ml to whole blood and incubated at 25° C, fibrinogen decreased 50 percent, plasminogen levels decreased 90 percent and α2-antiplasmin decreased below detectable levels. If D-Phe-Pro-Arg-chloromethylketone (PPACK) or aprotinin were added before the addition of rt-PA there was no significant loss of fibrinogen. Only PPACK completely inhibited changes in fibrin degradation products, plasminogen and α2-antiplasmin. PPACK was also found to inhibit the binding of rt-PA to plasma protease inhibitors in vitro.

Rhesus monkeys were infused with rt-PA and blood samples were taken with either PPACK or aprotinin in the collection syringe. There was a significant increase in the recovery of immunoreactive rt-PA and consistent measures of fibrinogen, FDPs, plasminogen, and α2-antiplasmin in the PPACK group as compared to the aprotinin group which indicates that PPACK will prevent the in vitro formation of artifacts due to the presence of active rt-PA

Monitoring of Hemostasis Parameters During Coronary Thrombolysis with Recombinant Tissue-Type Plasminogen Activator

The monitoring of changes in the blood coagulation and fibrinolytic systems during thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA) may be complicated by artifacts due to in vitro activation after blood collection and to interference of other agents (e. g., heparin) in the assays. In 106 patients with early acute myocardial infarction, infused with 150 mg of rt-PA (G11044) intravenously over 5 to 8 hours, blood samples were collected into liquid citrate supplemented with the plasmin inhibitor aprotinin (200 KlU/ml plasma) or on a lyophilized mixture of acidified citrate and the synthetic t-PA inhibitor D-Phe-Pro-Arg-CH2Cl (PPACK). A good correlation between precipitable (sulphite) and functional (clotting rate) fibrinogen levels was observed in plasma collected on citrate before therapy (r = 0.76) and in samples collected after 3 hours on either aprotinin (r = 0.87) or PPACK (r = 0.82). Precipitable fibrinogen levels were approximately 10% higher than functional level, in baseline samples collected on citrate alone and approximately 20% higher in 3 hour samples collected on either PPACK or aprotinin. Fibrinogen levels measured with both assays correlated well, but were somewhat higher in samples collected on PPACK than on aprotinin. rt-PA antigen levels assayed in plasma collected in either inhibitor correlated well (r = 0.90) but were 10-20% higher in PPACK containing samples. Addition of heparin up to 9 units/ml to plasma had no effect on the functional fibrinogen assay.

Even with these precautions for assay artifact, a very poor correlation (r =-0.15) was observed between the plasma rt-PA level and the residual functional fibrinogen level, both after 3 hours and towards the end of the rt-PA infusion. A decrease of the fibrinogen level at the end of the infusion to below 1 g/l was observed in 36% of the patients and to below 0.5 g/l in 11%. Optimal monitoring of hemostasis during rt-PA infusion is achieved by fibrinogen assays with a clotting rate method on samples collected on either PPACK or aprotinin. Heparin at therapeutic levels does not interfere with this assay.

Transient modulation of calcium and parathyroid hormone stimulates bone formation

Intermittent administration of parathyroid hormone can stimulate bone formation. Parathyroid hormone is a natural hormone that responds to serum calcium levels. In this study, we examined whether a transient increase and/or decrease in the serum calcium can stimulate bone formation. Using a mathematical model previously developed, we first predicted the effects of administration of parathyroid hormone, neutralizing parathyroid hormone antibody, calcium, and EGTA (calcium chelator) on the serum concentration of parathyroid hormone and calcium. The model predicted that intermittent injection of parathyroid hormone and ethylene glycol tetraacetic acid transiently elevated the serum parathyroid hormone, while that of parathyroid hormone antibody and calcium transiently reduced parathyroid hormone in the serum. In vitro analysis revealed that parathyroid hormone's transient changes (both up and down) elevated activating transcription factor 4-mediated osteocalcin expression. In the mouse model of osteoporosis, both intermittent administration of calcium and ethylene glycol tetraacetic acid showed tendency to increase bone mineral density of the upper limb (ulna and humerus) and spine, but the effects varied in a region-specific manner. Collectively, the study herein supports a common bone response to administration of calcium and its chelator through their effects on parathyroid hormone.

High MMP-1, MMP-2, and MMP-9 protein levels in osteoarthritis

Our study examined the relationship between the expression of matrix metalloproteinases (MMP)-1, MMP-2, and MMP-9 proteins and the pathogenesis of osteoarthritis (OA). We employed rigorous inclusion and exclusion criteria in computer-based bibliographic databases to extract published studies relevant to this investigation. The STATA 12.0 software was used for the statistical analyses. A total of 1408 studies were initially searched, and 10 studies with 458 OA patients and 295 healthy controls were included in this meta-analysis. The meta-analysis results suggested that the protein levels of MMP-1, MMP-2, and MMP-9 were higher in patients with OA than those in the control group. A subgroup analysis according to ethnicity showed that the protein levels of MMP-1 and MMP-2 were higher in Asian patients with OA than in controls. Caucasians showed no statistically significant differences in protein expression of MMP-1 and MMP-2 between the OA patient group and the control group. Interestingly, the protein levels of MMP-9 in patients with OA were higher than those in the control group in both Asians and Caucasians. A sample-source analysis suggested that the serum levels of MMP-2 and MMP-9 proteins were higher in patients with OA than in controls, while MMP-1 and MMP-9 protein expressions were higher in the synovial joint fluid of patients with OA than in controls. In conclusion, our meta-analysis results suggested that the increased expression of MMP-1, MMP-2, and MMP-9 proteins might be associated with the pathogenesis of OA.

Evaluating treatment of osteoporosis using particle swarm on a bone remodelling mathematical model

Bone loss in osteoporosis, commonly observed in postmenopausal women and the elderly, is caused by an imbalance in activities of bone-forming osteoblasts and bone-resorbing osteoclasts. To treat osteoporosis and increase bone mineral density (BMD), physical activities and drugs are often recommended. Complex systems dynamics prevent an intuitive prediction of treatment strategies, and little is known about an optimal sequence for the combinatorial use of available treatments. In this study, the authors built a mathematical model of bone remodelling and developed a treatment strategy for mechanical loading and salubrinal, a synthetic chemical agent that enhances bone formation and prevents bone resorption. The model formulated a temporal BMD change of a mouse's whole skeleton in response to ovariectomy, mechanical loading and administration of salubrinal. Particle swarm optimisation was employed to maximise a performance index (a function of BMD and treatment cost) to find an ideal sequence of treatment. The best treatment was found to start with mechanical loading followed by salubrinal. As treatment costs increased, the sequence started with no treatment and usage of salubrinal became scarce. The treatment strategy will depend on individual needs and costs, and the proposed model is expected to contribute to the development of personalised treatment strategies.

ELISA for quantitation of tumor necrosis factor-alpha in serum

A sensitive and precise ELISA has been developed for the quantitation of recombinant Tumor Necrosis Factor-Alpha (rTNF-alpha) in undiluted sera. Affinity purified rabbit antibody was used as capture antibody and mouse monoclonal antibody labelled with horseradish peroxidase was used as the second antibody in a sandwich ELISA. The assay range was from 50 to 2000 pg/ml and the relative standard deviation was 8% or less for both interassay and intra-assay precision studies. Recovery of rTNF-alpha added to 10 different human and 10 different monkey sera ranged from 81 to 102% and 100 to 120% of the expected value, respectively. This ELISA has been used to measure serum rTNF-alpha levels in over 60 patients in Phase I Clinical Trials treated with rTNF-alpha. The levels in a representative, pharmacokinetic study showed low variability between 8 patients receiving intravenous bolus administration of 100 mu rTNF-alpha/m(2). The ELISA results correlated well with TNF bioassay data with a mean specific activity of 2.5 x 10(7) U/mg.

Model-based comparative prediction of transcription-factor binding motifs in anabolic responses in bone

Understanding the regulatory mechanism that controls the alteration of global gene expression patterns continues to be a challenging task in computational biology. We previously developed an ant algorithm, a biologically-inspired computational technique for microarray data, and predicted putative transcription-factor binding motifs (TFBMs) through mimicking interactive behaviors of natural ants. Here we extended the algorithm into a set of web-based software, Ant Modeler, and applied it to investigate the transcriptional mechanism underlying bone formation. Mechanical loading and administration of bone morphogenic proteins (BMPs) are two known treatments to strengthen bone. We addressed a question: Is there any TFBM that stimulates both “anabolic responses of mechanical loading” and “BMP-mediated osteogenic signaling”? Although there is no significant overlap among genes in the two responses, a comparative model-based analysis suggests that the two independent osteogenic processes employ common TFBMs, such as a stress responsive element and a motif for peroxisome proliferator-activated receptor (PPAR). The post-modeling in vitro analysis using mouse osteoblast cells supported involvements of the predicted TFBMs such as PPAR, Ikaros 3, and LMO2 in response to mechanical loading. Taken together, the results would be useful to derive a set of testable hypotheses and examine the role of specific regulators in complex transcriptional control of bone formation.

Gigantic jets between a thundercloud and the ionosphere

Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.

Identification of multiple sources of charge heterogeneity in a recombinant antibody

Seven forms of a therapeutic recombinant antibody that binds to the her2/neu gene product were resolved by cation-exchange chromatography. Structural differences were assigned by peptide mapping and HIC after papain digestion. Deamidation of light chain asparagine 30 to aspartate in one or both light chains is responsible for two acidic forms. A low potency form is due to isomerization of heavy chain aspartate 102; the Asp102 succinimide is also present in a basic peak fraction. Forms with both Asn30 deamidation and Asp102 isomerization modifications were isolated. Deamidation of heavy chain Asn55 to isoaspartate was also detected. Isoelectric focusing in a polyacrylamide gel was used to verify the assignments. All modifications were found in complementarity determining regions.

Use of acidic and basic pH and calcium ion addition in the capillary zone electrophoretic characterization of recombinant human deoxyribonuclease, a complex phosphoglycoprotein

This paper describes the analysis of recombinant human deoxyribonuclease (rhDNAse), an acidic and complex phosphoglycoprotein, by capillary zone electrophoresis (CZE). Separation performance was found to be dramatically improved by the addition of calcium ions to the CZE running buffer, due to the influence of calcium binding on the charge and the electrophoretic behavior of rhDNAse. The pH dependent calcium binding effects on the electrophoretic separation were demonstrated at both acidic and basic pH, resulting in a two-dimensional (pH 4.8 and 8.0) calcium aided analysis that achieved multipeak resolution of the complex, glycosylation based, charge microheterogeneity of rhDNAse. Two-dimensional investigation of neuraminidase- and alkaline phosphatase-digested protein further demonstrated that the acidic pH resolved acidic charge heterogeneity and that the basic pH discriminated neutral heterogeneity. This work demonstrates the resolving power of CZE for the analysis of a complex microheterogeneous glycoprotein, and emphasizes the importance of employing multiple separation conditions in accordance with known structural characteristics of the protein.

Validation of a capillary isoelectric focusing method for the recombinant monoclonal antibody C2B8

A capillary isoelectric focusing (cIEF) method has been developed for the purpose of determining the identity and charge distribution of mouse/human chimeric antibody to human CD20 antigen (C2B8). The assay was validated in accordance with ICH guidelines in order to demonstrate that it is suitable for its intended purpose and so that it may be performed as a lot release test for bulk and final product. As a result of the validation process the assay was found to be linear over the concentration range of 2-356 micrograms ml-1 with recovery of 125I-labeled C2B8 at the target sample concentration of 125 micrograms ml-1 equal to 99%. The repeatability and intermediate precision relative standard deviations of the four major peaks for migration time, peak area, and peak area percent ranged from 0.9-4.4%. The specificity of the assay was demonstrated by baseline resolution of the C2B8 main peak from product excipients, and other Genentech monoclonal antibodies. The results of this validation demonstrate that the cIEF assay for the determination of identity and charge distribution of C2B8 is accurate, precise, linear, and highly specific. The assay is rapid and suitably rugged.

A non-radioactive complement-dependent cytotoxicity assay for anti-CD20 monoclonal antibody

A simple and non-radioactive complement-dependent cytotoxicity assay was developed to determine the relative potency of an anti-CD20 mAb, IDEC-C2B8. The assay measures the relative number of viable cells based on the uptake and metabolism of the redox dye, Alamar blue. A linear relationship between the relative fluorescence unit generated and the number of viable cells was demonstrated. The assay is simple, has high throughput (performed in 96-well microtiter plates), and shows reproducible dose-response curves in the concentration range of 0.02-3.3 micrograms/ml. With intra-assay variability of 5-12%, interassay variability of 6-10% and spike recoveries of 101-109%, the assay has high precision and accuracy. Specificity was demonstrated by the lack of activity of immunoglobulins that do not bind CD20, or anti-CD20 antibody isotype (gamma 4) which does not bind complement. The assay is able to detect degradative changes in the molecule caused by heat, light and proteolytic treatments, suggesting its use as a stability-indicating method. Finally, the Alamar blue method compared favorably with other more conventional methods used to assess cell viability. The assay has the desired properties for use as a potency assay for quality control testing of anti-CD20 mAb.

Capillary isoelectric focusing and sodium dodecyl sulfate-capillary gel electrophoresis of recombinant humanized monoclonal antibody HER2

Capillary isoelectric focusing (cIEF) and IEF of recombinant humanized monoclonal antibody HER2 (rhuMAbHER2) show five charged isoforms with estimated pI values ranging from 8.6-9.1. The cIEF assay demonstrated good precision with relative standard deviations (R.S.D.) 0.7-3.7% and 0.4-4.2% for intra and interassay analysis, respectively. The method was linear for the area of the main peak over the concentration range 2-250 micrograms/ml with a Pearson correlation coefficient > 0.99. The limit of detection for the main peak was determined to be 2 ppm. With both sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) and SDS-polyacrylamide gel electrophoresis, the nonreduced rhuMAbHER2 migrated as a single major peak with minor peaks in the aggregate and clip regions. After reduction, the electropherogram and the slab gel showed the expected heavy chain and light chain fragments with minor peaks in the aggregate and clip regions. The SDS-CGE assay showed good precision with R.S.D. values of 0.1-7.8% and 0.1-8.1% for intra and interassay analysis, respectively. The Pearson correlation coefficient for the area of the main peak was > 0.99 demonstrating linearity for the concentration range 0.5-500 micrograms/ml. The limit of detection for intact rhuMAbHER2 was determined to be 0.5 ppm. The data presented demonstrates the feasibility of replacing the slab gel techniques with capillary electrophoresis in a quality control environment.

Comparison of ampholytes used for slab gel and capillary isoelectric focusing of recombinant tissue-type plasminogen activator glycoforms

Four commercial ampholytes: Ampholine and Pharmalyte (Pharmacia Biotech), Bio-Lyte (Bio-Rad) and Servalyt (Serva) were evaluated for their ability to resolve recombinant tissue-type plasminogen activator (rt-PA) glycoforms by isoelectric focusing (IEF) and capillary IEF (cIEF). Each brand of ampholytes focused rt-PA into 3-4 major and 5-6 minor bands on slab gel electrophoresis. Visually, focused bands stained with Coomassie Blue appeared to be similarly resolved by all the ampholytes except for Ampholines, where the bands were closely grouped and more intensely stained. When cIEF was performed, Pharmalytes and Ampholines resolved rt-PA glycoforms consistent with the slab gels. No discernible peaks were detected during cIEF of rt-PA using Servalyts or Bio-Lytes. UV spectrophotometric scans of the components used for cIEF showed that Servalyts absorbed intensely over a range which overlapped the detector bandpass. Bio-Lytes showed absorption over a narrower UV range but still overlapped the detector bandpass, thus preventing the discernment of protein peaks. For this cIEF system the best ampholytes were Ampholines and Pharmalytes.

Examination of capillary zone electrophoresis, capillary isoelectric focusing and sodium dodecyl sulfate capillary electrophoresis for the analysis of recombinant tissue plasminogen activator

The microscale techniques of CZE, cIEF and SDS capillary electrophoresis have been evaluated for the analysis of a complex glycoprotein, recombinant tissue plasminogen activator (rtPA). A series of omega-amino acid buffers (pH approximately 5) was found suitable for the CZE separation of rtPA on coated capillaries. rtPA could be resolved into a series of major and minor peaks in an epsilon-aminocaproic acid buffer containing 0.01% (v/v) Tween 80. For cIEF, a two step method with pressure mobilization was utilized. Using a commercial instrument, either a polymer solution with a 50 microns I.D. capillary or narrow bore capillaries without a polymer solution (25 microns I.D.) were employed. rtPA was resolved into at least eight species within a pI range of 6.4-9.2 using Ampholine 3.5-10. Migration time precision for the major peaks ranged from 0.2% for CZE to < or = 2-3% R.S.D. for cIEF. Total recovery of rtPA from the capillary was also demonstrated for both methods. Analysis of rtPA, rtPA Type I, rtPA Type II and the desialylated forms resulted in the expected elution profiles. Finally, the potential of SDS capillary electrophoresis using a coated capillary for an rtPA Type I/Type II purity assay was shown.

Novel assays based on human growth hormone receptor as alternatives to the rat weight gain bioassay for recombinant human growth hormone

Two methods, High-Performance Receptor Binding Chromatography (HPRBC) and Cell Proliferation (CP), have been developed as alternatives to the classical hypophysectomized rat weight gain bioassay for the determination of potency for recombinant human growth hormone (rhGH). In the HPRBC assay, rhGH is combined with an excess of the soluble extracellular domain of the recombinant human growth hormone receptor (referred to as 'receptor' in the discussion of the HPRBC assay). Nondenaturing size-exclusion chromatography is used to analyzed the resulting complex, which forms in a 2:1 receptor to rhGH ratio. The 2:1 complex is assayed at a concentration near the Kd (approximately 0.4 nM), providing high specificity for rhGH and detection of rhGH variants with reduced activity. In the CP assay, a mouse myeloid leukaemia cell line (FDC-P1) transfected with the full-length receptor is exposed to varying levels of rhGH for 16-20 h. The incorporation of 3H-thymidine into DNA is used as an index of cell proliferation. The results show that the HPRBC assay provides significantly improved precision with a relative standard deviation (RSD) of < or = 5% vs. an RSD of 23% for the rat bioassay. The CP assay has RSDs of 4-16%. Analysis of rhGH variants and mutants shows that the potencies measured by both the HPRBC and CP assays are in general agreement with the rat weight gain bioassay. Both of the HPRBC and CP assays are sufficiently rugged for operating in a Good Manufacturing Practices (GMP) routine batch release testing environment. In vitro alternatives such as the HPRBC and CP assays build a foundation for replacing the hypophysectomized rat weight gain bioassay by correlating receptor dimerization, binding specificity and signal transduction with the biological activity of rhGH.

Electrophoretic separation of recombinant tissue-type plasminogen activator glycoforms: validation issues for capillary isoelectric focusing methods

Attempts were made to validate a capillary isoelectric focusing (cIEF) method for a recombinant glycoprotein as an alternative technique to slab gel isoelectric focusing methods routinely used to monitor such charge heterogeneity. The cIEF method principally separates the charged glycoforms of recombinant tissue-type plasminogen activator (rt-PA) on the basis of their sialic acid content. Nine to ten distinct peaks were consistently resolved, with the profile dependent on the class of ampholyte used. The pI of rt-PA measured with synthetic pI standards was in the range pH 6.5-7.5 with the migration of the standards affected by the presence of the protein. The method showed an acceptable recovery of > 100% and had good sensitivity where 25 ng of protein could be resolved into constituent peaks. Recovery of both major peaks and total protein measured by peak areas was linear over a wide range from 50-1000 micrograms/mL. A detailed study showed that when a capillary had been used for some time, capillary age affected peak migration times and, to a lesser extent, resolution. Peak migration times were stable over a temperature range of 15-30 degrees C, and decreased predictably with increasing voltages (400-600 V/cm) and decreasing N,N,N',N'-tetramethylethylene diamine (TEMED) concentrations (0.4-1.5% v/v). Overall the data indicated that this methodology has the potential to be used in the commercial release of protein pharmaceuticals if variability resulting from capillary age and lot were resolved. Even in its present format the method equals the performance of slab gel IEF whilst offering significant improvements in ease of operation and in time and reagent use.

Rapid one-step capillary isoelectric focusing method to monitor charged glycoforms of recombinant human tissue-type plasminogen activator

A rapid (< 10 min) one-step capillary isoelectric focusing (cIEF) method was developed to monitor charged glycoforms of recombinant human tissue-type plasminogen activator (rt-PA). Focusing takes place between the detector and the anode and the electro-osmotic flow (EOF) sweeps the separated glycoforms past the detector, towards the cathode. The separation uses a neutral coated capillary and hydroxypropylmethylcellulose (HPMC) to reduce the EOF to a constant and reproducible value. The method uses an ampholyte mix with a 50:50 ratio of pH 5-8 and pH 3-10 ampholytes in 4 M urea and 0.1% HPMC to produce maximal resolution whilst maintaining protein solubility during focusing. The electropherograms were compared to isoelectric focusing (IEF) slab gels of samples of intact rt-PA. In both cases approximately ten charged species could be detected. Data analysis indicated that the intra-assay precision was < 5% for peak migration times and < 10% for normalized peak areas. The number of charged species detected by each of the two methods was consistent for samples of intact rt-PA, rt-PA types I and II and for neuraminidase-digested rt-PA. Overall the data indicate that the automated cIEF method can be an adjunct to slab-gel IEF in the characterization and routine analysis of recombinant glycoproteins.

Difficulties in precise quantitation of CD4+ T lymphocytes for clinical trials: a review

Maintenance of CD4+ T helper lymphocyte counts has been used as a surrogate marker of efficacy for drugs in the treatment of AIDS. In a multicenter clinical trial, subtle improvement of CD4+ T cell counts may be masked and misinterpreted if care is not paid to likely sources that can contribute to the variability of measurement of CD4+ T lymphocytes. This review addresses major areas that can contribute to the variability of measurement of CD4+ T lymphocytes, with emphasis on applications to multicenter clinical trials, and proposes areas of improvement that may not be well recognized by the medical community. Whereas there are excellent guidelines for immunophenotyping, equal attention is needed in hematologic enumeration of WBC and absolute lymphocytes. In particular, allowing the margin of error acceptable to blood cell standards for HIV-infected specimens is unsatisfactory. Special attention should also be given to the stability of lymphocytes in the anticoagulant during storage, the lysing method, the quality assurance programs as well as intrasubject fluctuations which may be derived from exercise, medications and diurnal variations. Awareness of these contributing factors by physicians and technical analysts will expedite the discovery of potential therapy in the treatment of AIDS. For a multicenter clinical trial, it is advisable to select a centralized laboratory adopting a uniform protocol with regard to sample preparation and handling, using more stringent quality controls for hematologic analysers, calibration of instruments and immunophenotyping. Pending a true reference standard that can monitor the variation of the entire analytical procedure, we anticipate that future interlaboratory quality assurance programs will include absolute T lymphocyte count, an important parameter for assessing the accuracy and consistency of CD4+ T helper cell counts generated from a laboratory.

RGD-containing peptides inhibit adhesion of 293 cells transfected with GpIIb/IIIa to fibrinogen: comparison to inhibition of platelet aggregation

Cyclic RGD-containing peptides caused a dose-dependent inhibition of binding of human embryonic kidney cells transfected with recombinant GpIIb/IIIa (r293 clone B) to human fibrinogen coated on to non-tissue culture plates. The inhibitory activity, IC50, of a panel of seventeen RGD-containing peptides ranged from 0.12 to 89.2 microM. These IC50 values correlated with those determined by the inhibition of platelet aggregation (r = 0.99). Even though there was a correlation, there were differences between the platelet aggregation and the bioadhesion assay. The binding of r293 clone B to fibrinogen was not increased by ADP suggesting that GpIIb/IIIa expressed on the surface of r293 clone B cells may be in the 'activated' form. Moreover, preincubation of r293 clone B cells with a monoclonal antibody (mAb) specific for GpIIIa (4B12) resulted in a dose-dependent decrease of binding to fibrinogen while a mAb specific for GPIIb (2D2) had no effect. Neither of these mAbs inhibited platelet aggregation. The binding of r293 clone B cells to fibrinogen required Ca2+ or Mg2+. This cell-based bioadhesion method can provide a tool for screening potential GpIIb/IIIa antagonists and investigating the interaction of GpIIb/IIIa and fibrinogen not possible with platelet aggregation.

Recombinant porcine prorelaxin produced in Chinese hamster ovary cells is biologically active

Although prorelaxin has a similar structure as proinsulin, the posttranslational processing of prorelaxin seems to be quite different from that of proinsulin. There are no pairs of basic residues flanking the relaxin moiety in most prorelaxins studied so far. Instead, the prorelaxins of many species contains a tetrabasic sequence (Arg-Lys-Lys-Arg) between the connecting peptide and the A-chain. This is the recognition sequence of furin. In order to study this possible processing by furin, we express the recombinant porcine prorelaxin in Chinese hamster ovary cells. The expected 19 kDa recombinant porcine prorelaxin was found to be constitutively secreted into the medium at a level of approximately 250 ng/ml. No conversion of the 19 kDa prorelaxin into the 6 kDa relaxin was observed. Unlike most prohormones which are biologically inactive, the recombinant prorelaxin was found to be biologically active in an in vitro bioassay.

An antibody capture bioassay (ACB) for DNase in human serum samples

A novel assay for antibody captured bioactivity (ACB) has been developed to quantitate deoxyribonuclease I (DNase) in human serum samples. The procedure is simple, sensitive, reproducible and has a high throughput. Serum samples are diluted a minimum of 1/4 and assayed in 96-well microtiter plates coated with polyclonal antibodies specific to DNase. The serum is removed from the wells, the plates are washed and the antibody bound DNase is incubated at 37 degrees C with a DNA-methyl green substrate. The assay is sensitive to 0.8 ng/ml with a range to 10 +/- 2 ng/ml, depending upon the time of incubation (48 +/- 2 h). The recovery of rhDNase spiked into human serum samples averaged 84.4% +/- 6.7% in sera diluted 1/4 and 97.8% +/- 7.2% at a 1/8 serum dilution. Intra-assay precision ranged from 3.0 to 7.5% coefficient of variation (% CV) and interassay precision ranged from 5.0 to 10.2% CV for spiked serum controls. Endogenous DNase concentrations in 27 normal human sera were found to range from < 2.0 to 11.4 ng/ml. Endogenous DNase-like activity was found in Cynomolgus and Rhesus monkey sera; this activity diluted linearly and did not interfere with accurate quantitation of added rh DNase. No endogenous DNase-like activity could be detected in ten Sprague-Dawley rat sera. Bovine pancreatic DNase was found to have only very low cross-reactivity in this assay system. The ACB assay format can potentially be applied to the quantitation of other enzymes in serum and other biological samples.

Quantitation of E. coli protein impurities in recombinant human interferon-gamma

A multiple antigen ELISA for E. coli proteins (ECPs) that may be present in purified recombinant human interferon-gamma (rIFN-gamma) was developed. SDS-PAGE and Western blotting analyses showed that the assay antibodies reacted with a wide spectrum of ECPs in the standard and with ECPs in a production run. In spike recovery studies, rIFN-gamma at concentrations of 0.05 mg/mL and higher augmented the immunoreactivity of the ECPs in the standard curve (1.3-40.0 ng ECPs/mL) by approx 50%. To determine ECP content in purified rIFN-gamma, 0.2 mg/mL of rIFN-gamma was added to the standard curve diluent to compensate for enhanced immunoreactivity. The assay was precise (interassay precision of ECP controls < or = 4.1 %CV) and accurate with recoveries of 111-115% of expected for ECPs (15-40 ng/mL) spiked into purified rIFN-gamma (1 mg/mL). Linearity of dilution for ECPs spiked into rIFN-gamma was obtained (r = 0.999). Moreover, linearity of dilution was obtained for ECPs in "in-process" samples, demonstrating the required condition of antibody excess for this type of multiple antigen ELISA. ECPs were not detectable in several purified lots of rIFN-gamma. Therefore, these lots contained < 1.3 ppm ECPs.

Purification and characterization of recombinant porcine prorelaxin expressed in Escherichia coli

In this report we describe the purification and characterization of recombinant porcine prorelaxin expressed in Escherichia coli. Nucleotide sequence encoding porcine prorelaxin was inserted into an E. coli expression vector, pOTS, and the recombinant plasmid was transformed into the E. coli host (AR120). Upon induction with nalidixic acid, the 19-kDa recombinant porcine prorelaxin was produced at a level of approximately 8% of the total accumulated cell protein. The recombinant prorelaxin was purified to homogeneity by CM-cellulose chromatography and reversed-phase HPLC, after refolding in the presence of reduced and oxidized glutathione and a low concentration of guanidine-HCl. The identity of the recombinant prorelaxin was confirmed by the correct size, immunoreactivity with antibodies against native porcine relaxin, and direct amino-terminal sequence analysis. Furthermore, the purified recombinant prorelaxin could be converted to the 6-kDa relaxin by limited digestion with trypsin. Trypsin was shown to cleave at the carboxyl side of Arg29 and Arg137 residues of the recombinant prorelaxin, producing the des-ArgA1-B29-relaxin, and degrade the 13-kDa connecting peptide into small peptides. Both the recombinant prorelaxin and converted relaxin were found to be biologically active in an in vitro bioassay for relaxin.

The measurement of staphylococcal protein A by ELISA in immunoglobulin preparations

Chicken antibodies were used to develop an ELISA for the quantitation of parts-per-million levels of protein A in the purification of immunoglobulins or immunoglobulin-like molecules. Quantitation of protein A in the presence of excess human or murine immunoglobulins in this assay was compared with that obtained in ELISAs developed with rabbit antibodies specific either to protein A or to other molecules. Experiments demonstrate that protein A is bound to the immunoglobulins being purified and that this binding affects subsequent recognition by the antibodies used for the assay. Because of these effects and because fragments of protein A might not be detected in assays which rely on Fc binding of protein A, chicken antibodies that bind protein A specifically are an advantage for the quantitation of this protein by ELISA. In addition, comparison of the effect of different types of immunoglobulins on the protein A standard curve suggests that alternatives to including the immunoglobulin under purification with the standards can be utilized.

Low incidence of antibodies to recombinant human tissue-type plasminogen activator in treated patients

Sera from over 1,600 patients who received recombinant human tissue plasminogen activator (rt-PA) during clinical trials were assessed for the presence of antibodies to this therapeutic agent. The rt-PA was administered by a variety of dosage regimens for several different indications. Two different forms of rt-PA were used; one was predominantly two chain form, and the other was a predominantly one chain form. A sensitive radioimmunoprecipitation assay was used to measure antibodies to rt-PA in patients' serum before and after treatment. Of 932 patients tested with this assay, 929 were negative for antibodies to t-PA. Three patients developed low titers after treatment. Additional serum samples were obtained from these three patients within 2 years after rt-PA therapy and were negative for antibodies to t-PA. With the limited number of positive samples, no correlation could be found with dose or type of rt-PA, dosing regimen or clinical diagnosis. The virtual absence of antibody formation was confirmed in an additional 754 patients using a novel competitive two-site ELISA. It can be concluded that a single infusion of rt-PA was virtually unassociated with antibody formation, suggesting that repeat treatments could be given when necessary without the risk of immunologic complications as are seen with streptokinase or its derivatives.

Cyclic AMP response to recombinant human relaxin by cultured human endometrial cells--a specific and high throughput in vitro bioassay

A specific and high throughput 96-well format bioassay for recombinant human relaxin (rhRLX) has been developed using human endometrial cells (NHE cells). rhRLX caused a time- and dose-dependent stimulation of cyclic AMP (cAMP) with 1/2 maximal activity of 3.56 +/- 0.65 ng/ml (n = 30). The range of the standard curve was 0.39 to 25 ng/ml with interplate precision of 17 and 22% CV for high and low controls respectively. The cAMP response requires forskolin and 3-isobutyl-1-methylxanthine, and is enhanced by prostaglandin E2 and F2 alpha. The NHE cells do not respond to A or B chains of rhRLX, or a whole array of hormones. Preincubation of rhRLX with specific monoclonal antibody completely abolished the cAMP response. This bioassay has been used to determine the biological activity of several manufactured lots of recombinant human relaxin.

A sensitive radioimmunoprecipitation assay for the detection and quantitation of antibodies to the envelope glycoprotein gp120 of the human immunodeficiency virus (HIV-1)

A radioimmunoprecipitation (RIP) assay was developed to detect antibodies to the envelope glycoprotein gp120 of the human immunodeficiency virus (HIV-1). The assay, which utilized recombinant gp120 (rgp120), was quantitative, reproducible, and specific for antibodies to rgp120 or antibodies to native gp120 resulting from natural infection with HIV. Polyethylene glycol-8000 (PEG), used in the assay at a final concentration of 10% to precipitate immune complexes, was demonstrated to be effective in titering sera from different animal species. Provided samples were diluted at least 1:100, antibody titers could be determined either by the classical dilution method or by interpolation from a calibration curve prepared with a positive serum. The humoral response of animals immunized with rgp120 was monitored and a positive correlation was found between titers determined in the RIP assay and the ability of the sera to neutralize. In addition, RIP titers of HIV-positive human sera correlated very well with reactivity obtained in a commercial HIV immunoblot assay. The assay has the advantage of quantitation, fast turnaround time, and versatility.

Immunization procedures for E. coli proteins

Three immunization procedures were compared for the production of antibodies to the minor components of a complex E. coli protein (ECP) mixture: a conventional protocol and two methods that allow for the selective in vitro (cascade) or in vivo (passive) depletion of highly immunogenic proteins. An indirect ELISA showed that a maximum ELISA antibody titer was obtained with all the procedures 60 d after immunization. Analysis of these antisera by two-dimensional SDS-PAGE immunoblots, however, demonstrated that antibody reactivity to minor components in the mixture was not achieved until 112 d. This analysis also showed that a marked improvement in antibody response to minor components was obtained with the cascade immunization procedure. The mean titer and spectrum of antibody reactivity was similar for each group, and suggested that, although some individual variation was noted, the improvements observed were the result of the protocol used. Thus, for these ECPs, and multiple antigen mixtures in general, the preferred immunization protocol should employ at least three hosts and utilize the cascade immunization of Thalhamer and Freund. Characterization of the resulting antisera is best performed by use of silver stained two-dimensional SDS-PAGE and immunoblotting.

An enzyme-linked immunosorbent assay to study human relaxin in human pregnancy and in pregnant rhesus monkeys

A sensitive and specific double-antibody enzyme-linked immunoassay, using a synthetic analogue of human relaxin for standard and immunogen, was developed for the measurement of human relaxin (hRLX) in serum and plasma. No cross-reactivity was observed for human insulin, human insulin-like growth factor-I, hGH, human chorionic gonadotropin, hFSH, hLH or human prolactin. The assay was used to monitor RLX concentrations in samples from men, non-pregnant and pregnant women, and in pregnant rhesus monkeys infused with hRLX. RLX was not detected in serum from men nor from non-pregnant women, while a concentration of 600 ng/l was measured in pooled sera from two pregnant women (pregnancies achieved by in-vitro fertilization). Immunoreactive RLX (1.1 micrograms/g) was found in human corpora lutea taken from ectopic pregnancies at 7 weeks. In an experiment with a pregnant rhesus monkey infused with human RLX analogue, less than 1.5% of the maternal concentration was measured in the fetal circulation. Even though preliminary, these data suggest a low level of transfer of human analogue relaxin across the placenta in a rhesus monkey. Further studies of the physiology of RLX in human pregnancy will be facilitated by the availability of this immunoassay.

Variability in the quantitation of circulating growth hormone using commercial immunoassays

The quantitation of human GH in a serum sample is not consistent among various commercially available immunoassays. We measured serum GH concentrations with four RIAs [Cambridge, Kallestad, National Hormone and Pituitary Program, and Radioassay Systems Laboratories (RSL)] and two immunoradiometric assays (IRMAs; Hybritech and Nichols). Serum GH concentrations measured by the RIAs were between 1.9 and 2.8 times higher than those determined by the Hybritech IRMA, whereas the concentrations measured by the Nichols IRMA were approximately 3.0 times higher than the Hybritech values. We evaluated the effects of differences in standards, assay diluents, and antibody specificity on GH measurement in the various assays. When GH standards from each of the assays were measured in the Hybritech IRMA, only the RSL standard was less immunoreactive than the other assay standards. Different assay diluents also resulted in varying GH values. In the RIAs, GH diluted in serum was more immunoreactive than GH diluted in phosphate-buffered saline-0.5% BSA. This enhanced immunoreactivity appeared to be due to a nonspecific effect generated by serum. The Nichols and Hybritech IRMAs provide standards diluted in horse serum. In the Nichols assay, GH diluted in human serum was more immunoreactive than GH diluted in horse serum, whereas the immunoreactivity of GH diluted in either serum was equal in the Hybritech IRMA. These IRMAs also differ in that the Nichols assay detected the 20K variant of GH, whereas the Hybritech assay did not. Considering these discrepancies, comparison of data obtained using different assays should be made carefully.

Enzyme-linked immunosorbent assays (ELISAs) for the determination of contaminants resulting from the immunoaffinity purification of recombinant proteins

Two immunoassays have been developed for the quantitation of part-per-million levels of contaminants likely to co-purify with monoclonal antibodies produced in tissue culture and purified by protein A affinity chromatography. These contaminants are bovine IgG originating from the fetal bovine serum used in cell culture, and protein A. Mouse IgG was shown not to interfere in the bovine IgG assay, where contamination levels of 0.2-0.7% bovine IgG were measured in the lots of monoclonal antibody tested. The protein A ELISA was developed with monoclonal antibody included in the standard, and in the preparations of monoclonal antibody tested, 64 parts per million (ppm) or less of protein A were demonstrated. An additional immunoassay was developed to quantitate monoclonal antibody contamination of two recombinant proteins, rHBsAg and rgp 120 from HIV, purified by affinity chromatography with such antibodies. Possible interference of monoclonal antibody quantitation by the respective antigens was examined in this ELISA, and contamination levels of less than 56 ppm of antibody were determined in the purified recombinant proteins. The three immunoassays were shown to be specific for the major protein contaminants in either monoclonal antibodies or the recombinant proteins and were necessary in demonstrating their purity.

Monitoring of hemostasis parameters during coronary thrombolysis with recombinant tissue-type plasminogen activator

The monitoring of changes in the blood coagulation and fibrinolytic systems during thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA) may be complicated by artifacts due to in vitro activation after blood collection and to interference of other agents (e.g., heparin) in the assays. In 106 patients with early acute myocardial infarction, infused with 150 mg of rt-PA (G11044) intravenously over 5 to 8 hours, blood samples were collected into liquid citrate supplemented with the plasmin inhibitor aprotinin (200 KIU/ml plasma) or on a lyophilized mixture of acidified citrate and the synthetic t-PA inhibitor D-Phe-Pro-Arg-CH2Cl (PPACK). A good correlation between precipitable (sulphite) and functional (clotting rate) fibrinogen levels was observed in plasma collected on citrate before therapy (r = 0.76) and in samples collected after 3 hours on either aprotinin (r = 0.87) or PPACK (r = 0.82). Precipitable fibrinogen levels were approximately 10% higher than functional level, in baseline samples collected on citrate alone and approximately 20% higher in 3 hour samples collected on either PPACK or aprotinin. Fibrinogen levels measured with both assays correlated well, but were somewhat higher in samples collected on PPACK than on aprotinin. rt-PA antigen levels assayed in plasma collected in either inhibitor correlated well (r = 0.90) but were 10-20% higher in PPACK containing samples. Addition of heparin up to 9 units/ml to plasma had no effect on the functional fibrinogen assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of partial tolerance to the gastrointestinal effects of high doses of recombinant tumor necrosis factor-alpha in rodents

Treatment of healthy rats and mice with a single intravenous injection of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) caused a dose-dependent gastrointestinal inflammation. Within 30 min gastric emptying was blocked and tissue edema occurred in the small and large intestine. In the cecum hemorrhage occurred after 4 h at doses greater than or equal to 250 micrograms/kg. The cecum exhibited an acute inflammatory response following rHuTNF-alpha treatment similar to that seen in tumor necrosis at the same dose. The vascular endothelium became swollen, increased numbers of neutrophils and other leukocytes attached to and penetrated the endothelium, and finally hemorrhage occurred. Treatment of rats with daily injections of rHuTNF-alpha (250 micrograms/kg per d) for 3 wk failed to produce cachexia. Within 24-48 h rats became resistant to the hemorrhagic effect of rHuTNF-alpha, however, the cytokine still caused a transitory block of gastric emptying after 10 d of treatment. Treatment at 5- or 10-d intervals produced results similar to the initial injection. These results suggest that maximum hemorrhagic response will occur when rHuTNF-alpha is administered at intervals of 5-10 d rather than daily.

D-Phe-Pro-Arg-chloromethylketone: its potential use in inhibiting the formation of in vitro artifacts in blood collected during tissue-type plasminogen activator thrombolytic therapy

In vitro artifacts due to proteolysis may occur in blood samples containing recombinant tissue-type plasminogen activator (rt-PA) due to continued activation of plasminogen to plasmin by rt-PA. The aim of this study was to identify a rapid inhibitor of rt-PA that would not interfere in assays designed to monitor thrombolytic events. When rt-PA was added at 5 micrograms/ml to whole blood and incubated at 25 degrees C, fibrinogen decreased 50 percent, plasminogen levels decreased 90 percent and alpha 2-antiplasmin decreased below detectable levels. If D-Phe-Pro-Arg-chloromethylketone (PPACK) or aprotinin were added before the addition of rt-PA there was no significant loss of fibrinogen. Only PPACK completely inhibited changes in fibrin degradation products, plasminogen and alpha 2-antiplasmin. PPACK was also found to inhibit the binding of rt-PA to plasma protease inhibitors in vitro. Rhesus monkeys were infused with rt-PA and blood samples were taken with either PPACK or aprotinin in the collection syringe. There was a significant increase in the recovery of immunoreactive rt-PA and consistent measures of fibrinogen, FDPs, plasminogen, and alpha 2-antiplasmin in the PPACK group as compared to the aprotinin group which indicates that PPACK will prevent the in vitro formation of artifacts due to the presence of active rt-PA.

Immunoassay for the detection of E. coli proteins in recombinant DNA derived human growth hormone

An enzyme-linked immunosorbent assay (ELISA) has been developed for the quantitation of part-per-million levels of the most probable E. coli polypeptide (ECP) contaminants of E. coli produced biosynthetic human growth hormone (hGH). The antibody preparation, used for both coat and conjugate in this ELISA, was demonstrated to be reactive with the reference ECPs (a collection of the most probable protein contaminants) by both affinity chromatography and immunoblot analysis. Affinity purification of this antibody preparation using immobilized reference ECPs resulted in an assay with a higher signal-to-noise ratio and also 'normalized' the antibody population to approach stoichiometric equivalence with the immobilized ECPs. Reference ECPs, size fractionated by gel filtration, were quantitated in agreement with their absorbance at 280 nm. The assay was demonstrated to be specific for ECPs obtained from the hGH purification process. Since the purification of each recombinant DNA derived protein from E. coli requires its own unique process, this means that no generic ECP assay can be developed. It is felt that the criteria established for this assay provide a comprehensive approach to the development of quantitative multiple antigen immunoassays.

A sensitive radioimmunoprecipitation assay for the detection of antibody to recombinant human gamma-interferon: comparison to a bioassay neutralization test

This report describes a specific radioimmunoprecipitation (RIP) assay for the detection of antibodies to recombinant DNA (rDNA) derived human gamma-interferon (rHuIFN-gamma). The assay was shown not to detect antibodies to rHuIFN-alpha, rHuIFN-beta, human lymphotoxin, or E. coli proteins and was reproducible with intraassay and interassay coefficients of variation of 1.6 and 3%, respectively, for the log titer of a high positive control. Comparison of this assay with a standard bioassay for detection of neutralizing antibody (abrogation of the inhibitory effect of rHuIFN-gamma on EMC virus replication in A549 cells) demonstrated that the RIP assay was more sensitive for detection of HuIFN-gamma neutralizing monoclonal antibody. Nonneutralizing monoclonal antibody was detectable in the RIP assay but not in the bioassay neutralization test. Examination of polyclonal antisera (rabbit and monkey) that contained neutralizing antibodies also demonstrated the RIP system to be a more sensitive indicator of the presence of antibodies than the bioassay neutralization test. In preliminary studies of human samples (86 patients) from clinical trials using an assay precipitation system capable of detecting antibody of the IgG, IgM, IgA, and IgE classes, no antibody to rHuIFN-gamma was observed. These patients were also found negative for neutralizing antibody to rHuIFN-gamma.