OS042. Discovery and characterization of antibody biomarkers ofpre-eclampsia and reagents for their detection.

INTRODUCTION: The effective management of pre-eclampsia (PE), a complex condition affecting 5% of pregnancies [1], would benefit from a clear diagnostic assay. Due to this need, great interest lies in the development and validation of objective biomarkers, among which antibodies remain attractive given their amplification by the immune system, stability, and current clinical use. Although several recent studies lend support to the idea that autoantibodies against the angiotensin II AT1 receptor (AT1-AAs) could be involved in PE [1], their presence is not highly specific for PE as measured by cell-based assays for AT1 agonism [2]. Given these results, we hypothesized that additional antibody biomarkers may exist in PE, and that a small panel of such biomarkers could provide an effective diagnostic tool. Furthermore, development of a simple binding assay will facilitate AT1-AA detection for larger-scale studies, while identifying other antibody biomarker(s) would enhance understanding of the immune component to PE pathogenesis. OBJECTIVES: The primary objective of this study was to identify a panel of peptide reagents that preferentially bind PE patients' serum antibodies. In addition, we sought to measure the frequency of AT1-AAs in a new patient cohort using a simplified assay. METHODS: Plasma samples were obtained from normal-outcome pregnancies (n=28) as well as PE patients (n=25) and enriched for the antibody fraction. The seven amino acid AT1-AA epitope [1] was expressed on the surface of E. coli for reactivity analysis by flow cytometry. A bacteria-displayed linear peptide library was screened against the antibody repertoires using a unique method of fluorescence activated cell sorting (FACS) to isolate peptides that react with multiple patients and show little reactivity with normal-outcome pregnancies. FACS analysis was used to measure individual peptide reactivity, and statistical analyses included a Student's t-test and nonparametric tests to compare the means, medians, and normal scores. RESULTS: Using this simple binding assay, AT1-AAs were detected in a majority of PE patients and more rarely in normal-outcome pregnancies. Among the isolated peptide mimics, several unique peptides demonstrated significantly (p<0.03) higher reactivity with PE patients than with control samples but showed no sequence homology to the known AT1 epitope. Not only did our peptides perform well with the original set of samples used for discovery, but these peptides also reacted with antibodies from a small set of new PE (n=10) sera but not from new normal-outcome (n=10) pregnancies. CONCLUSION: Peptides distinct from the AT1 epitope and identified by library screening exhibited potential diagnostic utility for PE, suggesting that a panel of such peptides might provide a novel diagnostic test to distinguish PE from other conditions with similar symptoms. Also, this study demonstrated AT1-AA presence in an independent patient cohort with a simple binding assay, which can be easily expanded to evaluate larger cohorts.

Hemolysin-positive enteroaggregative and cell-detaching Escherichia coli strains cause oncosis of human monocyte-derived macrophages and apoptosis of murine J774 cells.

Infection of human monocyte-derived macrophages (HMDM) and J774 cells (murine macrophage cell line) with several enteroaggregative and cytodetaching Escherichia coli (EAggEC and CDEC, respectively) strains demonstrated that some strains could induce macrophage cell death accompanied by release of lactate dehydrogenase activity and interleukin 1beta (IL-1beta) into culture supernatants. The mode of cell death differed in the two types of macrophages. Damage to macrophage plasma membrane integrity without changes in nuclear morphology resulted in cytolysis of HMDM. This mechanism of cell death has been previously described for virulent Shigella infection of HMDM and is termed oncosis. In contrast, infection of J774 cells by EAggEC and CDEC strains resulted in apoptosis. The presence of alpha-hemolysin (Hly) in EAggEC and CDEC strains appears to be critical for both oncosis in HMDM and apoptosis in J774 cells. Bacteria lacking Hly, including Hly- EAggEC strains as well as enterotoxigenic, enteropathogenic, and enterohemorrhagic E. coli strains, behaved like avirulent Shigella flexneri in that the macrophage monolayers were intact, with no release of lactate dehydrogenase activity or IL-1beta into the culture supernatants.

Turbulent airflow meter for long-term monitoring in patient-ventilator circuits.

A new type of flowmeter is described which operates on the principle that pressure drop (deltaP) produced by turbulent volume flow (V) through a simple resistance chamber obeys a relation of V = K (deltaP)0.50. Data are given showing that the device follows a true power law with a single exponent for airflows ranging from 3.5 to 270 l/min. Standard instrumentation and a linearization circuit are used with the new flowmeter to provide linear steady-state and alternating airflow measurements up to peak rates of 150 l/min and frequency to 15 Hz. Data are presented comparing integrated airflow readings from the new turbulent flowmeter and a laminar-type flowmeter. The turbulent airflow meter appears to offer increased reliability for long-term patient monitoring use in patient-ventilator circuits.