Volume 43, Issue 12

Serum protein profiling by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) appears to be an important diagnostic tool for a whole range of diseases. Sensitivities and specificities obtained with this new technology often seem superior to those obtained with current biomarkers. However, reproducibility and standardization are still problematic. The present review gives an overview of the diagnostic value of protein profiles obtained with SELDI in studies on prostate and ovarian cancer. To identify aspects important for protein profiling, we compare and discuss differences in pre- and post-analytical conditions presented in the literature supplemented with some of our own data. Further progress in protein profiling as a diagnostic tool requires a more comprehensive description of technical details in all future studies.

Classical methods of protein analysis such as electrophoresis, ELISA and liquid chromatography are generally time-consuming, labor-intensive and lack high-throughput capacity. In addition, all existing methods used to measure proteins necessitate multiple division of the original sample and individual tests carried out for each substance, with an associated cost for each test. The chip system allows several tests to be performed simultaneously without dividing the original patient sample. This system facilitates the development of multiplexed assays that simultaneously measure many different analytes in a small sample volume. These emerging technologies fall into two categories: 1) spotted array-based tools, and 2) microfluidic-based tools. Miniaturized and multiplexed immunoassays allow a great deal of information to be obtained from a single sample. These analytical systems are referred to as “lab-on-a-chip” devices. This article presents current trends and advances in miniaturized multiplexed immunoassay technologies, reviewing different systems from research to point-of-care assays. We focus on a subset of chip-based assays that may be used in a clinical laboratory and are directly applicable for biomedical diagnosis. Recent advances in biochip assays combine the power of miniaturization, microfluidics, micro- to nanoparticles, and quantification. A number of applications are just beginning to be explored. The power of biochip assays offers great promise for point-of-care clinical testing and monitoring of many important analytes.

Background: Proteomics' requirement for simultaneous measurement of multiple markers is now possible with biochip array technology. Many laboratories utilise in-house, manual procedures for biochip fabrication and sample testing. Reproducibility and standardisation of biochip processes is vital to ensure quality of results and offer the best tool for elucidation of complex relationships between multiple proteins in diseased conditions. Methods: Various novel control checks have been implemented in biochip fabrication, reagent manufacture, automation and imaging processes for the Evidence analyser. Reference spots enable location of discrete test regions on the surface of the biochip and simultaneous quantification of multiple markers. Performance and standardisation methods are presented. Results: Formulation of dispense solution for discrete test regions had a direct effect on their shape, stability and integrity on the biochip surface. Assays for fertility hormones and drugs of abuse demonstrated excellent precision, stability and comparison with other commercial methods. Conclusion: Control processes employed in the manufacture and analysis of Evidence components ensure reproducibility of assays for a range of routine and novel markers.

The detection, diagnosis, and management of breast cancer rely on an integrated approach using clinical history, physical examination, imaging, and histopathology. The discovery and validation of novel biomarkers will aid the physician in more effectively achieving this integration. This review discusses efforts in surface-enhanced laser desorption/ionization (SELDI)-based proteomics to address various clinical questions surrounding breast cancer, including diagnosis, monitoring, and stratification for treatment. Emphasis is placed on examining how study design and execution influence the discovery and validation process, which is critical to the proper development of potential clinical tests.

In the emerging field of Functional Proteomics , protein microarrays are considered to be one of the most promising tools for the simultaneous analysis of the a) abundance, b) function, and c) interaction of proteins on a system-wide scale. Resting on the technological grounds of widely used DNA biochips, the great power of microarray-based miniature solid-phase immunoassays lies in their potential to investigate in parallel large numbers of analyte pairs in a variety of biological samples. Consequently, this has fuelled aspirations that protein microarrays may serve as tools for the high-throughput functional investigation of complete proteomes and, moreover, that they will develop into promising candidates for innovative in-vitro diagnostic (IVD) applications. To date, published examples of protein microarrays for IVD purposes have included tests for allergy, autoimmune and infectious diseases. Here, we discuss recent advancements in the development of protein microarrays for the profiling of IgE antibodies in the diagnosis of Type 1-related allergic diseases.

The ProteomeLab™ PF2D protein fractionation system is a rapid, semi-automated, 2 D-HPLC instrument that uses two different methods to separate plasma serum proteins: ion-exchange chromatography using a wide pH range in the first dimension, and non-porous reverse-phase chromatography in the second dimension. Because this methodology has only very recently been introduced in proteomic laboratories, little is known about the characteristics of PF2D fractionation of human serum proteins. To evaluate the system's application in a clinical laboratory setting, the characteristics of the ion-exchange chromatography-based separation were analyzed. Following fractionation of human serum proteins on a linear pH gradient (ranging from 8.0 to 4.0), each fraction was collected in a cool module of the instrument. Different fractions obtained from the first dimension were then pooled together and loaded on classic 2D gel electrophoresis instrumentation. The different spots obtained were then checked against the Swiss-Prot Data-base. A total of 36 human serum proteins were identified in different PF2D-generated fractions. Some important features of the separation system were observed. Different eluted fractions contained different proteins, thus demonstrating the reliability of the fractionation system. The proteins were also fractionated according to the theoretical isoelectric point (pI). This was consistent with the evidence that the vast majority of immunoglobulins, characterized by an alkaline pI, were not retained by the column and were eluted in the unbound fraction. This outcome also underlines a practical advantage: fractions eluted from pH8 to pH4 contained virtually immunoglobulin-depleted serum proteins. This finding supports an immediate use of the PF2D system in a clinical setting, where abundant proteins should be clearly identified to enable evaluation of other less abundant, but potentially relevant, species.

The genotypes of alcohol dehydrogenase-1B ( ADH1B ) and aldehyde dehydrogenase-2 ( ALDH2 ) are related to alcohol dependence and some human disorders. Rapid, accurate genotyping methodologies for specific polymorphisms of these two genes are needed for molecular screening and testing of alcohol-related problems in populations. A polymerase chain reaction (PCR) composed of two separate amplicons was designed to generate sequences containing the polymorphic site of interest in the ADH1B and ALDH2 genes. The PCR amplicons for each sample were subjected to denaturing high-performance liquid chromatography (DHPLC), analysis performed under partially denaturing conditions as determined by profiling the mixture of a unique homozygous control and a tested sample amplicon. A total of 150 genomic DNA samples were tested to validate this assay by blind analysis. Direct DNA sequencing was performed on samples randomly selected from each of the genotype groups detected by DHPLC profiling. The results indicate 100% concordance between the sequencing analysis and the DHPLC detection. The method we present provides a reliable and fast genotyping procedure for molecular screening of alcohol-related problems.

Background: Apolipoprotein A-I gene ( APOA1 ) polymorphisms have been associated with variations in serum low-density lipoprotein (LDL)- and high-density lipoprotein (HDL)-cholesterol. We have investigated whether APOA1 common variants are also associated with variations in basal triglyceride serum concentrations and response to atorvastatin in individuals with hypercholesterolemia. Methods: APOA1 G–75A and C83T polymorphisms and variations in serum lipids were evaluated in 150 hypercholesterolemic (HC) and 93 normolipidemic (NL) unrelated European-derived Brazilians treated with atorvastatin (10mg/day for 4weeks). Genomic DNA was extracted from blood leukocytes using a salting-out method and APOA1 polymorphisms were analyzed by polymerase chain reaction and restriction fragment length polymorphism. Results: G–75A polymorphism was associated with differences in serum concentrations of triglyceride and very low-density lipoprotein (VLDL)-cholesterol (p=0.026) in HC men. After atorvastatin treatment, women carrying the GG / CC haplotype had lower serum triglyceride and VLDL-cholesterol (p=0.020) than non-carriers. In men, the reduction in serum triglyceride in response to atorvastatin was found to be slightly lower in GG / CC haplotype carriers (p=0.051). Conclusion: Our data suggest that APOA1 polymorphisms are associated with variations of baseline serum concentrations of triglyceride and VLDL-cholesterol and in response to atorvastatin in a gender-specific manner.

Background: The enzyme catalase is the main regulator of hydrogen peroxide metabolism. Deficiency of catalase may cause high concentrations of hydrogen peroxide and increase the risk of the development of pathologies for which oxidative stress is a contributing factor, for example, type 2 diabetes mellitus. Catalase deficiency has been reported to be associated with increased frequency of diabetes mellitus in a cohort of patients in Hungary. In this cohort, the majority of mutations in the catalase gene occur in exon 2. Methods: Type 2 diabetic patients (n=308) were evaluated for mutations in intron 1 (81bp), exon 2 (172bp) and intron 2 (13bp) of the catalase gene. Screening for mutations utilized PCR single-strand conformational polymorphism (SSCP) and PCR heteroduplex methods. Verification of detected mutations was by nucleotide sequence analysis. Results: A total of 11 catalase gene mutations were detected in the 308 subjects (3.57%, p<0.001). Five of the 11 were at two previously reported mutation sites: exon 2 (79) G insertion and (138) GA insertion. Six of the 11 were at five previously unreported catalase mutation sites: intron 1 (60) G→T; intron 2 (7) G→A and (5) G→C; exon 2 (96) T→A; and exon 2 (135) T→A. The novel missense mutations on exon 2 (96 and 135) are associated with 59% and 48% decreased catalase activity, respectively; the novel G→C mutation on intron 2 (5) is associated with a 62% decrease in catalase activity. Mutations detected on intron 1 (60) and intron 2 (7) showed no change in catalase activity. The G→C mutation on intron 2 (5) might be a splicing mutation. The two missense mutations on exon 2 (96) and (135) cause substitutions of amino acids 53 (Asp→Glu) and 66 (Glu→Cys) of the catalase protein. These are close to amino acids that are important for the binding of heme to catalase, 44 (Val) and 72–75 (Arg, Val, Val, His). Changes in heme binding may be responsible for the activity losses. Conclusion: Mutations that cause decreased catalase activity may contribute to susceptibility to inherited type 2 diabetes mellitus. Exon 2 and neighboring introns of the catalase gene may be minor hot spots for type 2 diabetes mellitus susceptibility mutations.

The diagnosis of myocardial damage is preferably based on measurement of the cardiac-specific troponins. However, there is an emerging need for early, specific cardiac markers. One potential candidate is the glycogen phosphorylase BB isoenzyme (GPBB). We investigated the use of a new, commercially available GPBB ELISA assay in 61 patients presenting with an acute coronary syndrome (37 acute myocardial infarction, 24 unstable angina pectoris) in comparison to established cardiac markers such as troponin T, creatine kinase isoenzyme MB (CKMB) mass, and myoglobin. Blood samples were obtained on arrival, as well as 1, 2, 3, 4, 8, 12 and 24h later. GPBB plasma concentrations were elevated in 90.9% of patients 1h after onset of chest pain and increased to 100% at 4–5h. Within the first 6h, GPBB showed the highest sensitivity (95.5–100%) and high specificity (94–96%) compared to myoglobin (85–95% sensitivity) and CKMB mass (71.4–91.3% sensitivity). As expected, troponin T showed high specificity (100%) and sensitivity >95% later in the time course (≥3h). In un-stable angina pectoris patients, a very high rate of elevated GPBB was observed (93.9% at 3h) compared to myoglobin (66.7%). Cardiac troponin T and CKMB were only elevated in 33.8% and 55.0% of these patients, respectively. In conclusion, GPBB is a promising marker for the early diagnosis of acute coronary syndromes and could probably act as a marker of ischemia. However, further studies on specificity and development of a fast, automated assay are necessary before GPBB can be recommended as a routine diagnostic tool.

The role of leptin during the progression of osteoporosis was investigated in ovariectomized rats by correlation of serum leptin levels with N-telopeptide of collagen type I (NTx) and osteocalcin levels before ovariectomy and 20, 40 and 60days after the operation. Furthermore, peripheral quantitative computed tomography was used to confirm the development of severe osteoporosis in rats on day 60. The levels of NTx and osteocalcin were significantly increased on day 20 [61.9±5.4nM BCE (bone collagen equivalents) and 215.6±53.3ng/mL, respectively] in comparison to those before ovariectomy (41.3±1.7nM BCE and 60.4±10.9ng/mL). Accordingly, leptin was significantly elevated on day 20 (3033±661 vs. 606±346 pg/mL before ovariectomy). Bone markers and leptin levels remained constant up to day 40, while a slight, but not statistically significant, decrease was noted for osteocalcin and leptin on day 60. Although leptin and bone markers did not correlate before ovariectomy (r=0.09 for NTx and r=−0.05 for osteocalcin), strong correlation was observed at all time points after ovariectomy. The data obtained suggest that the alterations in serum leptin levels during the progression of osteoporosis in ovariectomized rats follow the alterations in bone markers.

Background: Hemoglobin A1c (HbA 1c ) is a proxy measure for glycemic control in diabetes. We investigated the trend for glycemic control in patients from three Danish counties using HbA 1c measurements. Methods: We studied 2454 patients from a population of 807,000 inhabitants for whom routine monitoring of diabetes using HbA 1c-DCCT aligned was initiated in 2001. We estimated the incidence of monitored patients in the population. The progress in patients with originally diabetic HbA 1c levels was investigated by cumulative probability plots, and the individual trend in clinical outcome was investigated by a modified difference plot. Results: The age-standardized incidence of monitored patients was <0.5% in all regions. Patients with diabetic first HbA 1c concentrations (≥6.62% HbA 1c ) showed on average 15% improved glycemic control in the first year. Further improvement was limited. The overall percentage above the treatment target (≥6.62% HbA 1c ) was 51% in 2003 compared to 59% in 2001, and the percentage with poor glycemic control (≥10.0% HbA 1c ) was reduced from 19% to 4%. Of patients with originally diabetic HbA 1c levels, 15% showed progress in glycemic control, and 28% reached treatment targets. In patients with originally normal HbA 1c , 75% showed an upward trend in HbA 1c levels, which reached diabetic concentrations in 17%. Conclusion: Patients with diabetic first HbA 1c concentrations (≥6.62% HbA 1c ) showed on average 15% improved glycemic control in the first year. Further improvement was limited. In individual patients, 75% with originally diabetic HbA 1c levels showed improved glycemic control after 3years, while 78% withoriginally normal concentrations showed an upwardtrend in HbA 1c levels.

Hyperhomocysteinemia is regarded as an independent risk factor for vascular diseases, and homocysteine is supposed to contribute to oxidative stress and endothelial damage. Statin therapy is an established intervention to reduce the risk of acute events in patients suffering from cardiovascular diseases. Apart from their lipid-lowering capacity, statins also exert anti-inflammatory and antioxidant effects. As cellular immune activation and oxidative stress play a major role in the pathogenesis of cardiovascular diseases, the anti-inflammatory capacity of statins could partly be responsible for the beneficial effects observed in patients. Earlier we reported that stimulated peripheral blood mononuclear cells (PBMCs) release homocysteine. Here we studied the influence of atorvastatin on homocysteine production in stimulated PBMCs and compared changes in cysteine concentrations and in neopterin production, which is a sensitive indicator of cellular immune activation. Stimulation of human PBMCs with the mitogens concanavalin A and phytohemagglutinin induced significant homocysteine and neopterin production compared to unstimulated cells, whereas cysteine concentrations remained unchanged. Treatment of PBMCs with increasing doses of atorvastatin (10–100μM) suppressed both biochemical pathways in a dose-dependent manner, and cell proliferation was inhibited in parallel. Again, cysteine levels were not influenced by any treatment. The down-regulating effect of atorvastatin on homocysteine formation in vitro indicates that statins may prevent homocysteine accumulation in the blood via immunosuppression.

Buprenorphine is a narcotic analgesic used in the treatment of moderate-to-severe pain. In Italy, buprenorphine is now being used as an alternative in the therapeutic treatment of heroin abusers. Even if confirmation methods are needed for identification and quantitation, a rapid and sensitive test, such as an immunoassay, is essential for screening. We evaluated the Buprenorphine One-step ELISA test (designed for serum specimens) for the qualitative determination of buprenorphine in other matrices, such as urine, saliva and hair.

Our aims were: 1) to analyze the effect of the methodology used to derive clinically feasible cut-off values for thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), which exhibit highly skewed distributions; and 2) to describe the influence of thyroid antibodies on thyroid stimulating hormone (TSH) and free thyroxine (FT 4 ) reference intervals among thyroid disease-free aged subjects. The reference population consisted of 1086 individuals with a mean age of 73years. The impacts of TPOAb and/or TgAb positivity on the reference intervals of TSH and FT 4 were evaluated by both including and excluding subjects with elevated thyroid antibodies. The exclusion of subjects with elevated thyroid antibodies had no effect on the FT 4 reference interval in either gender or on the TSH reference interval in men. Among women, the exclusion of 196 (34%) thyroid antibody-positive subjects resulted in lowering of the upper reference limit of TSH from 7.2 to 5.8mIU/L. When the more stringent “mode-method” by summing mode+(mode–2.5th percentile) was used, 334 women (58%) were excluded and the upper reference limit of TSH remained essentially identical. Regardless of the statistical methodology used to derive cut-off values, the effect of antibody positivity was found to be less than expected.

Tissue factor, the main initiator of blood coagulation, is shed into plasma by blood cells and endothelium. While studying such circulating plasma tissue factor with a commercially available immunoassay, we found unsatisfactory results and therefore developed a new and highly sensitive enzyme-linked immunosorbent assay (ELISA). High-affinity monoclonal antibodies raised against recombinant soluble tissue factor were used and the new assay had a detection limit of 40fmol/L, approximately six-fold lower than existing assays. Normal ranges in 20 healthy donors were established in serum and in citrated EDTA and heparinized plasma. Tissue factor was also measured in three successive plasma samples from 43 patients with type 2 diabetes mellitus. In citrated plasma from healthy donors, tissue factor concentrations were 2.5 (1.0–9.3) pmol/L (median with range) and were not significantly different in diabetics. With a commercially available immunoassay, seven plasma samples were below the detection limit. Use of the new assay reduced intra-individual variation in diabetics from 49% to 14% and we conclude that high-affinity antibodies may markedly improve immunoassay performance.

Matrix metalloproteinases are a family of zinc-dependent proteinases which are involved in the breakdown and remodeling of extracellular matrix. As children grow and adolescents reach pubescence, their bodies undergo changes that require age-related morphogenesis of the extracellular matrix, possibly requiring unique patterns of matrix metalloproteinase (MMP) expression during periods of rapid tissue growth (i.e., childhood) or accelerated tissue remodeling and expansion (i.e., adolescence). Therefore, we have characterized age-specific and gender-specific differences in circulating concentrations of MMPs (specifically MMP-1, -2, -3, -8 and -9) in 189 serum samples obtained from healthy subjects, aged 2–18 years. MMP concentrations were measured using Fluorokine ® MultiAnalyte Profiling kits and a Luminex ® Bioanalyzer, as well as by commercial ELISA. Serum levels of MMP-1, -2, -3, -8, and -9 in healthy pediatric subjects represent log-normal distributions. MMP-2 was significantly negatively correlated with age (r=−0.29; p<0.001), while MMP-3 was significantly positively correlated with age (r=0.38; p<0.001). Although plasma, not serum, is considered the appropriate blood sample for measurement of MMP-8 and -9, serum levels of MMP-8 and -9 were also found to be highly positively correlated with each other (r=0.76; p<0.01). MMP results obtained by Fluorokine ® MultiAnalyte Profiling methods correlated well with conventional ELISA methods and use of this technology provided several advantages over ELISA.

We developed sensitive assay methods for autoantibodies recognizing the citrullinated synthetic peptides derived from type I and type II collagens in patients with rheumatoid arthritis (RA). These peptides were tested with the chemiluminescence method (Nichols Advantage ® System). In 44 RA patients out of 120, the sera showed increased binding of citrullinated synthetic C-telopeptide derived from the α1 chain of type I collagen (p=0.003 compared to controls). For a corresponding C-telopeptide pair from the α1 chain of type II collagen, 35 patient sera bound the citrullinated peptide more strongly than the arginine peptide, but the difference compared to the controls was not significant (p=0.074). Correlation between the two carboxy-telopeptides was r=0.473 (p<0.001). The anti-CCP assay (antibodies against citrullinated filaggrin sequence-derived peptides) was positive in 59% of our RA patients. There was no relationship between the anti-CCP results and the antibodies against collagen C-telopeptides, but both are increased in RA patients. We demonstrated autoantibodies in RA patients that bound citrullinated C-telopeptides derived from type I and type II collagen antigens. The peptide sequences detected (-YYXA and -YMXA) were different from that based on the cyclic filaggrin antigen (-STXG-, where X represents citrulline).