Recycling immunoaffinity chromatography for multiple analyte analysis in biological samples

Early changes in pro-inflammatory cytokine levels in neonates with encephalopathy are associated with remote epilepsy

BACKGROUND

Neonatal seizures are associated with adverse neurologic sequelae including epilepsy in childhood. Here we aim to determine whether levels of cytokines in neonates with brain injury are associated with acute symptomatic seizures or remote epilepsy.

METHODS

This is a cohort study of term newborns with encephalopathy at UCSF between 10/1993 and 1/2000 who had dried blood spots. Maternal, perinatal/postnatal, neuroimaging, and epilepsy variables were abstracted by chart review. Logistic regression was used to compare levels of cytokines with acute seizures and the development of epilepsy.

RESULTS

In a cohort of 26 newborns with neonatal encephalopathy at risk for hypoxic ischemic encephalopathy with blood spots for analysis, diffuse alterations in both pro- and anti-inflammatory cytokine levels were observed between those with (11/28, 39%) and without acute symptomatic seizures. Seventeen of the 26 (63%) patients had >2 years of follow-up and 4/17 (24%) developed epilepsy. Higher levels of pro-inflammatory cytokines IL-6 and TNF-α within the IL-1β pathway were significantly associated with epilepsy.

CONCLUSIONS

Elevations in pro-inflammatory cytokines in the IL-1β pathway were associated with later onset of epilepsy. Larger cohort studies are needed to confirm the predictive value of these circulating biomarkers.

Allergies and childhood leukemia

A majority of studies to date have reported an inversed association between allergies and childhood leukemia. However, this association is likely an indirect one and may represent some shared underlying immune mechanisms that have been explained in the context of the "hygiene hypothesis", which has been thought to play an important role in the development of both allergies and childhood leukemia. This review focuses on what we know so far about the role of various immune cells (Th1, Th2, T regulatory and Th17 cells) in the development of allergies and how they may potentially be related to the etiology of childhood leukemia. In addition, the utilities of genetic and molecular studies to disentangle the association between allergies and childhood leukemia and to elucidate the biological mechanisms are also discussed.

Elevated neuroimmune biomarkers in sweat patches and plasma of premenopausal women with major depressive disorder in remission: the POWER study

BACKGROUND

Major depressive disorder (MDD) is inconsistently associated with elevations in proinflammatory cytokines and neuropeptides. We used a skin sweat patch, recently validated in healthy control subjects, and recycling immunoaffinity chromatography to measure neuroimmune biomarkers in patients with MDD mostly in remission.

METHODS

We collected blood at 8:00 am and applied skin sweat patches for 24 hours in 21- to 45-year-old premenopausal women (n = 19) with MDD (17/19 in remission) and age-matched healthy controls (n = 17) participating in the POWER (Premenopausal, Osteopenia/Osteoporosis, Women, Alendronate, Depression) Study.

RESULTS

Proinflammatory cytokines, neuropeptide Y, substance P, and calcitonin-gene-related peptide were significantly higher and vasoactive intestinal peptide, a marker of parasympathetic activity, was significantly lower in patients compared to controls, and depressive symptomatology strongly correlated with biomarker levels. All analytes were strongly correlated in the skin sweat patch and plasma in patients (r = .73 to .99; p < .0004).

CONCLUSIONS

The skin sweat patch allows detection of disrupted patterns of proinflammatory cytokines and neuropeptides in women with MDD in clinical remission, which could predispose to medical consequences such as cardiovascular disease, osteoporosis, and diabetes. This method permits measurement of cytokines in ambulatory settings where blood collection is not feasible.

Immunoaffinity capillary electrophoresis as a powerful strategy for the quantification of low-abundance biomarkers, drugs, and metabolites in biological matrices

In the last few years, there has been a greater appreciation by the scientific community of how separation science has contributed to the advancement of biomedical research. Despite past contributions in facilitating several biomedical breakthroughs, separation sciences still urgently need the development of improved methods for the separation and detection of biological and chemical substances. In particular, the challenging task of quantifying small molecules and biomolecules, found in low abundance in complex matrices (e.g., serum), is a particular area in need of new high-efficiency techniques. The tandem or on-line coupling of highly selective antibody capture agents with the high-resolving power of CE is being recognized as a powerful analytical tool for the enrichment and quantification of ultra-low abundance analytes in complex matrices. This development will have a significant impact on the identification and characterization of many putative biomarkers and on biomedical research in general. Immunoaffinity CE (IACE) technology is rapidly emerging as the most promising method for the analysis of low-abundance biomarkers; its power comes from a three-step procedure: (i) bioselective adsorption and (ii) subsequent recovery of compounds from an immobilized affinity ligand followed by (iii) separation of the enriched compounds. This technology is highly suited to automation and can be engineered to as a multiplex instrument capable of routinely performing hundreds of assays per day. Furthermore, a significant enhancement in sensitivity can be achieved for the purified and enriched affinity targeted analytes. Thus, a compound that exists in a complex biological matrix at a concentration far below its LOD is easily brought to well within its range of quantification. The present review summarizes several applications of IACE, as well as a chronological description of the improvements made in the fabrication of the analyte concentrator-microreactor device leading to the development of a multidimensional biomarker analyzer.

Microfluidic immunoaffinity separations for bioanalysis

Microfluidic devices often rely on antibody-antigen interactions as a means of separating analytes of interest from sample matrices. Immunoassays and immunoaffinity separations performed in miniaturized formats offer selective target isolation with minimal reagent consumption and reduced analysis times. The introduction of biological fluids and other complicated matrices often requires sample pretreatment or system modifications for compatibility with small-scale devices. Miniaturization of external equipment facilitates the potential for portable use such as in patient point-of-care settings. Microfluidic immunoaffinity systems including capillary and chip platforms have been assembled from basic instrument components for fluid control, sample introduction, and detection. The current review focuses on the use of immunoaffinity separations in microfluidic devices with an emphasis on pump-based flow and biological sample analysis.

Applications of silica supports in affinity chromatography

The combined use of silica-based chromatographic supports with immobilized affinity ligands can be used in many preparative and analytical applications. One example is the use of silica-based affinity columns in HPLC, giving rise to a method known as high-performance affinity chromatography (HPAC). This review discusses the role that silica has played in the development of affinity chromatography and HPAC and the applications of silica in these methods. This includes a discussion of the types of ligands that have been employed with silica and the methods by which these ligands have been immobilized. Various formats have also been presented for the use of silica in affinity chromatographic methods, including assays involving direct or indirect analyte detection, on-line or off-line affinity extraction, and chiral separations. The use of silica-based affinity columns in studies of biological systems based on zonal elution and frontal analysis methods will also be considered.

Measurement of cytokines in sweat patches and plasma in healthy women: validation in a controlled study

Cytokines have been detected by ELISA in a variety of body fluids. Recycling immunoaffinity chromatography (RIC) coupled with laser-induced fluorescence detection is a highly sensitive and specific method, which allows simultaneous measurements of many analytes in small volumes of biological fluids. This method has been applied to plasma, cervical secretions and other body fluids, but has not previously been applied to sweat. The aim of this study was to validate the RIC methodology in sweat for measurements of IL-1alpha, IL-1beta, IL-6, TNF-alpha, IL-8 and TGF-beta. Two sweat patches were applied for 24 h on the torso, and blood was collected at one time point during this period in nine healthy women. Cytokines were measured in paired samples of plasma and sweat. Cytokines were detected in sweat in similar concentrations to plasma. Linear regression analysis confirmed that sweat levels of these cytokines accounted for a large percentages of variance in plasma levels: IL-1alpha (R2 = 0.70, p = 0.005), IL-1beta (R2 = 0.79, p = 0.003), IL-6 (R2 = 0.52, p = 0.03), TNF-alpha (R2 = 0.95, p < 0.0001), IL-8 (R2 = 0.81, p = 0.001) and TGF-beta (R2 = 0.94, p = 0.0003). These findings indicate that cytokine levels measured in sweat are informative of circulating levels and that sweat patches combined with RIC represents a viable non-invasive method to measure cytokines in ambulatory settings over time. This method is unobtrusive and requires minimal active compliance on the part of the subjects being studied, without pain or stress. This approach can open a new generation of studies to address the effects of environmental factors on immune responses in a wide range of different settings.

Simultaneous Measurement of 25 Inflammatory Markers and Neurotrophins in Neonatal Dried Blood Spots by Immunoassay with xMAP Technology

Background: Inflammatory reactions and other events in early life may be part of the etiology of late-onset diseases, including cerebral palsy, autism, and type 1 diabetes. Most neonatal screening programs for congenital disorders are based on analysis of dried blood spot samples (DBSS), and stored residual DBSS constitute a valuable resource for research into the etiology of these diseases. The small amount of blood available, however, limits the number of analytes that can be determined by traditional immunoassay methodologies.

Methods: We used new multiplexed sandwich immunoassays based on flowmetric Luminex® xMAP technology to measure inflammatory markers and neutrophins in DBSS.

Results: The high-capacity 25-plex multianalyte method measured 23 inflammatory and trophic cytokines, triggering receptor expressed on myeloid cells-1 (TREM-1), and C-reactive protein in two 3.2-mm punches from DBSS. It also measured 26 cytokines and TREM-1 in serum. Standards Recovery in the 25-plex method were 90%–161% (mean, 105%). The low end of the working range for all 25 analytes covered concentrations found in DBSS from healthy newborns. Mean recovery of exogenous analytes added at physiologic concentrations in DBSS models was 174%, mean intra- and interassay CVs were 6.2% and 16%, respectively, and the mean correlation between added and measured analytes was r2 = 0.91. In DBSS routinely collected on days 5–7 from 8 newborns with documented inflammatory reactions at birth, the method detected significantly changed concentrations of inflammatory cytokines. Measurements on DBSS stored at −24 °C for &gt;20 years showed that most cytokines are detectable in equal concentrations over time.

Conclusions: The method can reliably measure 25 inflammatory markers and growth factors in DBSS. It has a large potential for high-capacity analysis of DBSS in epidemiologic case–control studies and, with further refinements, in neonatal screening.

Beyond human papillomavirus: the cervix, exogenous secondary factors, and the development of cervical precancer and cancer

Human papillomavirus (HPV) is the necessary but probably not sufficient cause of cervical precancer and cancer. Secondary exogenous and endogenous factors, HPV cofactors, may contribute to the probability of a cancer-associated (oncogenic) HPV infection progressing to cervical precancer and cancer. For these cofactors to influence the natural history of HPV infection, they must act on cervical tissue to promote viral persistence, progression to precancer or cancer given viral persistence, or both. The aim of this review was to examine briefly the impact these factors may have on carcinogenesis of the cervix. Specifically, the roles of the cervical transformation zone, cervical immunity, inflammation and coinfection, and exposure to the main HPV cofactors (smoking, oral contraceptive use, and multiparity) are discussed.

Development of a High-Throughput Format for Solid-Phase Extraction of Enantiomers Using an Immunosorbent in 384-Well Plates

An antibody-based solid-phase extraction method for filtered 384-well plates was developed for a medical drug candidate having two enantiomeric forms in order to demonstrate the potential of the use of recombinant antibody fragments as specific and efficient immunosorbents. An immobilization method using a six-histidine tag of the antibody fragment and mild oxidation was applied in order to immobilize antibody fragments in an oriented and kinetically stable way that ensured high capacity of the antibody support. Phosphate buffer or plasma spiked with enantiomers were used as samples. Selective solid-phase extraction was followed by liquid chromatography-mass spectrometry analysis. Average recoveries for buffer and plasma samples ranged from 79 to 122% and 80 to 108%, respectively. Good linearity was observed in the concentration range of 30-3000 ng/mL of the enantiomer.

Neonatal encephalopathy: association of cytokines with MR spectroscopy and outcome

In term neonatal encephalopathy, little is known about the relationship between early inflammatory markers, neonatal brain injury, and long-term neurodevelopmental outcome. Our goal was to determine whether neonatal serum cytokine levels are associated with cerebral metabolism assessed by proton magnetic resonance spectroscopy (MRS), with magnetic resonance imaging (MRI) abnormalities, and with neurodevelopmental outcome at 30 mo of age. Levels of seven cytokines [IL-1 beta, IL-6, IL-8, IL-9, IL-12, IL-13, and tumor necrosis factor (TNF)-alpha] were measured in dried neonatal blood by immunoaffinity chromatography in a prospective cohort of 62 term newborns at risk of neonatal encephalopathy. MR images (n = 61) were scored and lactate/choline and N-acetyl-aspartate (NAA)/choline were measured by MRS (n = 42) on median day of life 6 in the deep gray nuclei (DGN) and in the watershed/cortical zone (WS). Neurodevelopmental outcome (n = 54) was considered abnormal if the infant died or if cognitive delay and/or functional motor deficit were detected at 30 mo. IL-1 beta, IL-6, IL-8 and TNF-alpha were significantly associated with lactate/choline in the DGN (p = 0.03, 0.02, 0.03, and 0.01 respectively), but not in the WS (all p > 0.1). Cytokines were not associated with NAA/choline in any region or with MRI scores. Children with abnormal neurodevelopmental outcome had higher neonatal levels of IL-1 beta, IL-6, IL-8, and lower levels of IL-12 (p = 0.04, 0.03, 0.01, 0.03 respectively). Elevated inflammatory cytokines were associated with impaired cerebral oxidative metabolism, but not with detectable MRI changes in the neonatal period. Understanding the link between elevated cytokines and outcome would inform novel strategies of cerebral protection.

Immunoaffinity solid-phase extraction for pharmaceutical and biomedical trace-analysis—coupling with HPLC and CE—perspectives

Immunoaffinity solid-phase extraction (SPE) technique is based upon a molecular recognition mechanism. The high affinity and the high selectivity of the antigen-antibody interactions allow the specific extraction and the concentration of the analytes of interest in one step. In pharmaceutical and biological fields, where most often matrices are complex and analytes at trace-levels, this approach constitutes a unique tool for fast and solvent-free sample preparation. This review presents a general description of this extraction technique and gives numerous examples of its applications in pharmaceutical and biomedical fields. It emphasizes the on-line coupling with chromatographic and electrophoretic separation techniques and introduces new developments. The future directions, especially with regards to the current development of analytical microsystems, are discussed.

Neonatal cytokines and cerebral palsy in very preterm infants

To examine the relationship of cytokines in blood of very preterm neonates with later diagnosis of spastic cerebral palsy (CP) compared with infants of similar gestational age without CP, we measured concentrations of inflammatory cytokines and other substances in archived neonatal blood by recycling immunoaffinity chromatography. Subjects were surviving children born before 32 wk gestational age (GA) to women without preeclampsia, 64 with later diagnoses of CP and 107 control children. The initial analyses were augmented by measurement of 11 cytokines by a bead-based flow analytic system (Luminex) in an additional 37 children with CP and 34 control children from the same cohort. Concentrations of examined substances did not differ by presence of indicators of infection in mother, infant, or placenta. On ANOVA, concentrations of a number of cytokines were significantly related to neonatal ultrasound abnormalities (periventricular leukomalacia, ventricular enlargement, or moderate or severe germinal matrix hemorrhage). None of the substances measured either by immunoaffinity chromatography or flow analytic methods, including IL-1, -6, and -8 and tumor necrosis factor-alpha, was related to later diagnosis of CP or its subtypes. Inflammatory cytokines in neonatal blood of very premature infants did not distinguish those with later diagnoses of CP from control children.

Changes in astroglial GLT-1 expression after neural transplantation or stab wounds

Uncontrolled release of glutamate from damaged brain initiates events that result in excitotoxic neuronal death. Glutamate uptake by specialized astroglial transporters is essential for control of extracellular glutamate levels. Many studies have demonstrated a reduction in astrocytic GLT-1 expression after different forms of injury. Because extensive neuronal death does not occur after direct cortical stab wounds and viable developing neurons populate fetal CNS grafts, we hypothesized that reactive astroglia associated with these procedures might maintain or up-regulate GLT-1. We examined the temporal and spatial distribution of GLT-1, GFAP and nestin proteins by confocal double-label immunohistochemistry combined with a new methodology in which precise brain areas are microdissected and analyzed for protein content by immunoaffinity chromatography. In stab wounds, GLT-1 protein content did not change compared to normal cortex, as determined by direct protein measurements; GLT-1 colocalized with nestin- and GFAP(+) astroglia adjacent to the lesion. In contrast, host reactive astroglia adjacent to grafts significantly upregulated GLT-1 by 3 days postoperative. The GFAP protein analysis suggests that increased GLT-1 is not the result of greater numbers of activated astroglia around grafts, but that developing graft tissue influences adjacent host astroglia to upregulate GLT-1. GLT-1 protein within grafts was rapidly accelerated to mature levels by just three days, and was expressed by the nestin(+) cell population. These data, which demonstrate immunoexpression of GLT-1 protein combined with a new method for protein measurement in situ indicate that, in contrast to other injury models, astroglial GLT-1 is upregulated or maintained following invasive CNS procedures. (c)2002 Elsevier Science (USA).

Cervical concentrations of interleukin-10 and interleukin-12 do not correlate with plasma levels

Human papillomavirus (HPV) infects the transformation zone of the cervix and is the primary cause of cervical cancer. The infection is localized to the cervix and mucosal immunity is likely to be an important determinant for viral clearance. Previous studies of immunity to HPV have measured immune markers in the blood, but the relationship of systemic immunity to cervical immunity is poorly understood. In this study of 70 women enrolled in the ASCUS-LSIL Triage Study (ALTS), a clinical trial for management of low-grade cytologic abnormalities of the cervix, we collected paired plasma and cervical secretions to investigate the relationship between cervical concentrations of interleukin-10 (IL-10) and interleukin-12 (IL-12) and plasma levels. Neither IL-10 (p = 0.11), or IL-12 (p = -0.04) nor the ratio of IL-12 to IL-10 (p = 0.06) were correlated between blood and cervical secretions. Except for weak correlations of IL-10 among nonsmokers (p = 0.35. P = 0.019) and those in day 18-27 of their menstrual cycle (p = 0.51, P = 0.015), this lack of correlation persisted in all subgroups defined by genital inflammation or infection, current oral contraceptive use, heme contamination and volume of collected secretions, HPV16 seropositivity, and repeat HPV infection and/or cytologic abnormalities. The lack of correlation and high concentrations in cervical secretions indicate that the cervical IL-10 and IL-12 concentrations exceed what could be expected from blood as a principle source of IL-10 and IL-12 and suggest that cytokine concentrations in cervical secretions are predominantly the result of local cytokine production.

Multi-analyte analysis of biological fluids with a recycling immunoaffinity column array

A system for isolating and measuring up to 30 analytes in a single biological sample is described. The system is based on recycling a pre-labeled sample through an array of capillary immunoaffinity columns, each packed with glass beads, coated with a different antibody, thus enabling each column to isolate and extract a single analyte. Detection of the bound analytes is achieved by laser-induced fluorescence (LIF), using a laboratory-built scanning detector coupled to a fiber-optic spectrometer. The array can be regenerated up to 200 times, provided a suitable temperature is maintained. The individual immunoaffinity columns are able to bind between 2.9 and 3.6 ng of analyte, depending upon the individual column, with lower limits of detection (LOD) in the order of 1.6-2.8 pg/ml. The inter- and intra-assay coefficients of variation (CV) for all 30 columns in the array were less than 6.03+/-0.33 at analyte concentrations of 100 pg/ml. Comparison to standard enzyme-immunoassays demonstrated r(2) values in the range of 0.9151-0.9855 when analyzed by least-squares linear regression.

Cerebrovascular disorders in children with the factor V Leiden mutation

Since 1995, at least 128 children with a cerebrovascular disorder, cerebral palsy, or both and the factor V Leiden mutation have been reported. The majority of these strokes were in the first year of life, many of them in the perinatal period. Two thirds had an additional exogenous risk factor for thrombosis, and 42% had another recognized endogenous prothrombotic risk factor in combination with the mutation. We review the association of the factor V Leiden mutation and a cerebrovascular disorder in children younger than 16 years of age and describe the clinical features of 8 children with cerebral palsy and the Leiden mutation. This mutation should be considered in the evaluation of children with a stroke or its sequelae, including infants with perinatal stroke.

Elevated serum and cerebrospinal fluid levels of soluble human herpesvirus type 6 cellular receptor, membrane cofactor protein, in patients with multiple sclerosis

Membrane cofactor protein (CD46) is a member of a family of glycoproteins that are regulators of complement and prevent activation of complement on autologous cells. Recently, CD46 has been identified as the cellular receptor for human herpesvirus Type 6 (HHV-6). Elevated levels of soluble CD46 have been described in several autoimmune disorders, and may be implicated in the pathogenesis of these diseases. As several reports have supported an association of HHV-6 and multiple sclerosis, it was of interest to compare levels of soluble CD46 in the sera of multiple sclerosis patients to that of healthy controls, other neurological disease controls, and other inflammatory disease controls. Using an immunoaffinity column comprised of immobilized monoclonal antibodies to CD46, serum levels of soluble CD46 were found to be significantly elevated in multiple sclerosis patients compared with healthy and other neurological disease controls. Moreover, multiple sclerosis patients who tested positive for HHV-6 DNA in serum had significantly elevated levels of soluble CD46 in their serum compared with those who were negative for HHV-6 DNA. A significant increase in soluble CD46 was also found in the serum of other inflammatory disease controls tested compared to healthy controls. Additionally, a significant correlation was demonstrated between levels of soluble CD46 in the serum and cerebrospinal fluid of multiple sclerosis patients. Collectively, these data suggest that elevated levels of soluble CD46 may contribute to the pathogenesis of inflammatory diseases, including multiple sclerosis.

Neuropeptides and neurotrophins in neonatal blood of children with autism or mental retardation

There has been little exploration of major biologic regulators of cerebral development in autism. In archived neonatal blood of children with autistic spectrum disorders (n = 69), mental retardation without autism (n = 60), or cerebral palsy (CP, n = 63) and of control children (n = 54), we used recycling immunoaffinity chromatography to measure the neuropeptides substance P (SP), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), calcitonin gene-related peptide (CGRP), and the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4/5 (NT4/5). Neonatal concentrations of VIP, CGRP, BDNF, and NT4/5 were higher (ANOVA, all p values < 0.0001 by Scheffe test for pairwise differences) in children in the autistic spectrum and in those with mental retardation without autism than in control children. In 99% of children with autism and 97% with mental retardation, levels of at least one of these substances exceeded those of all control children. Concentrations were similar in subgroups of the autistic spectrum (core syndrome with or without mental retardation, other autistic spectrum disorders with or without mental retardation) and in the presence or absence of a history of regression. Among children with mental retardation, concentrations did not differ by severity or known cause (n = 11, including 4 with Down syndrome). Concentrations of measured substances were similar in children with CP as compared with control subjects. SP, PACAP, NGF, and NT3 were not different by diagnostic group. No measured analyte distinguished children with autism from children with mental retardation alone. In autism and in a heterogeneous group of disorders of cognitive function, overexpression of certain neuropeptides and neurotrophins was observed in peripheral blood drawn in the first days of life.

A duplexed microsphere-based fluorescent immunoassay

Microsphere-based immunoassays are described for the simultaneous measurement of the clinically important drugs digoxin and theophylline. Competitive immunoassays were performed using haptenized microspheres and antibodies labeled with horseradish peroxidase. Enzyme-catalyzed reporter deposition (CARD) resulted in immunofluorescence signal amplification. Two encoding dyes were used to differentiate analytical signals from microspheres containing assays for the two analytes. An epifluorescence microscope and a CCD camera interfaced with a computer were utilized to measure fluorescence signals of individual microspheres. The microspheres from a duplexed assay were mounted on microscope slides as well as inserted into wells etched into the distal ends of optical imaging fibers. Fluorescence images from both formats were captured. In the experiments using microscope slides, the immunoassays were successfully duplexed and only marginal interferences at high analyte concentrations were observed. Preliminary results suggest that simultaneous determination of the two analytes using a fiber-based sensor-array format is feasible, but requires further development before precise quantitative analyses are possible.

Mediators of fetal inflammation in extremely low gestational age newborns

To establish levels of mediators of inflammation in cord blood and postnatal serum from extremely low gestational age newborns (ELGANs, < or =28 weeks), we measured sixteen markers of inflammation by recycling immunoaffinity chromatography in 15 ELGANs who had serum sampled at days 2-5. Median levels of IL-1, IL-6, IL-8, IL-11, IL-13, TNF-alpha, G-CSF, M-CSF, GM-CSF, MIP-1alpha, and RANTES were considerably higher than published values of these inflammatory mediators from term newborns. In three of eight ELGANS who had serial measurements taken, levels of IL-1, IL-6, IL-8, IL-11, TNF-alpha, G-CSF, and MIP-1alpha declined from initially very high levels to reach an apparent baseline towards the end of the first postnatal week. In these same three infants, GM-CSF and TGF-beta1 levels increased continuously during the first week. In the other five ELGANs, no consistent changes were observed. We speculate, that in some ELGANs, a fetal systemic inflammatory response is characterized by an antenatal wave of pro-inflammatory cytokines, followed by a second, postnatal wave of anti-inflammatory cytokines. Large epidemiologic studies are needed to clarify relationships among inflammation markers and their expression in the fetal and neonatal circulation over time. Such studies would also add to our understanding of the possible role of inflammatory mediators in the pathophysiology of the major complications of extreme prematurity.

Immunoaffinity solid-phase extraction for the trace-analysis of low-molecular-mass analytes in complex sample matrices

Immunoaffinity solid-phase extraction (SPE) sorbents, so-called immunosorbents (ISs), are based upon molecular recognition using antibodies. Thanks to the high affinity and high selectivity of the antigen-antibody interaction, they allow a high degree of molecular selectivity and have shown to be a unique tool in the sample preparation area these last few years. Extraction and clean-up of complex biological and environmental aqueous samples are achieved in the same step and from large volumes when required. Their application to extracts from solid matrixes is solvent-free and more simple than any other clean-up procedure. Single analytes can be targeted, but since an antibody can also bind one or more analytes having structure similar to the one used for its preparation, ISs have been developed for targeting a single analyte and its metabolites. The cross-reactivity was also exploited for developing ISs that could selectively extract a whole class of structurally related compounds. This review describes the current technology used for the synthesis of the ISs, their properties and their field of application. The different parameters governing the antigen-antibody interactions and the solid-phase extraction process are discussed. Emphasis is given to the optimisation of the SPE sequence, especially to the desorption and regeneration steps. The importance of the capacity and its relationship with the analytes recovery and breakthrough volumes is highlighted for class-specific ISs. Multi-class-selective ISs are also presented. Validation studies are reviewed using various certified reference materials. Relevant examples, involving combination with chromatography in both off-line and on-line mode, illustrate the high selectivity provided in various complex matrixes. Miniaturisation is also described, since it allows high throughput of samples.

Role of the fetus in perinatal infection and neonatal brain damage

Increasing evidence supports the view that infants exposed to perinatal infection are at increased risk for brain injury. We suggest that elevated cytokines in the amniotic fluid or in the fetal circulation be viewed as a humoral expression and that inflammatory cells in chorionic plate or umbilical cord blood vessel walls be viewed as a morphologic expression of the fetal inflammatory response. We discuss the evidence supporting the hypothesis that the fetal inflammatory response contributes to neonatal brain injury and later developmental disability. Little support has been found for a maternal contribution. Intervention should be designed with the fetus in mind.

Affinity Chromatography: A Review of Clinical Applications

Affinity chromatography is a type of liquid chromatography that makes use of biological-like interactions for the separation and specific analysis of sample components. This review describes the basic principles of affinity chromatography and examines its use in the testing of clinical samples, with an emphasis on HPLC-based methods. Some traditional applications of this approach include the use of boronate, lectin, protein A or protein G, and immunoaffinity supports for the direct quantification of solutes. Newer techniques that use antibody-based columns for on- or off-line sample extraction are examined in detail, as are methods that use affinity chromatography in combination with other analytical methods, such as reversed-phase liquid chromatography, gas chromatography, and capillary electrophoresis. Indirect analyte detection methods are also described in which immunoaffinity chromatography is used to perform flow-based immunoassays. Other applications that are reviewed include affinity-based chiral separations and the use of affinity chromatography for the study of drug or hormone interactions with binding proteins. Some areas of possible future developments are then considered, such as tandem affinity methods and the use of synthetic dyes, immobilized metal ions, molecular imprints, or aptamers as affinity ligands for clinical analytes.