The TARC/sICAM5 Ratio in Patient Plasma is a Candidate Biomarker for Drug Resistant Epilepsy

Abstract

Epilepsy is a common affliction that involves inflammatory processes. There are currently no definitive chemical diagnostic biomarkers in the blood, so diagnosis is based on a sometimes expensive synthesis of clinical observation, radiology, neuro-psychological testing, and interictal and ictal EEG studies. Soluble ICAM5 (sICAM5), also known as telencephalin, is an anti-inflammatory protein of strictly central nervous system tissue origin that is also found in blood. Here we have tested the hypothesis that plasma concentrations of select inflammatory cytokines, including sICAM5, might serve as biomarkers for epilepsy diagnosis. To test this hypothesis, we developed a highly sensitive and accurate electrochemiluminescent ELISA assay to measure sICAM5 levels, and measured levels of sICAM5 and 18 other inflammatory mediators in epilepsy patient plasma and controls. Patient samples were drawn from in-patients undergoing video-EEG monitoring, without regard to timing of seizures. Differences were defined by t-test, and Receiver Operating Condition (ROC) curves determined the ability of these tests to distinguish between the two populations. In epilepsy patient plasmas, we found that concentrations of anti-inflammatory sICAM5 are reduced (p = 0.002) and pro-inflammatory IL-1β, IL-2, and IL-8 are elevated. TARC (thymus and activation regulated chemokine, CCL17) concentrations trend high. In contrast, levels of BDNF and a variety of other pro-inflammatory mediators are not altered. Based on p-value and ROC analysis, we find that the ratio of TARC/sICAM5 discriminates accurately between patients and controls, with an ROC Area Under the Curve (AUC) of 1.0 (p = 0.034). In conclusion, we find that the ratio of TARC to sICAM5 accurately distinguishes between the two populations and provides a statistically and mechanistically compelling candidate blood biomarker for drug resistant epilepsy.

Proinflammatory and anti-inflammatory cytokines in febrile seizures and epilepsy: systematic review and meta-analysis

“…Some abstracts seemed to be related, but full-text was not available to make sure if they met the inclusion criteria or not (Ling et al, 1993;Kawakami et al, 1999b;Haspolat et al, 2002;Ganor et al, 2005;Makis et al, 2005;Lehtimäki et al, 2010;Lukaszewicz et al, 2010;Majoie et al, 2010;Mine et al, 2013). Further hand searching of references was performed and 17 related articles met the inclusion criteria and involved TNF-α, interferon (IFN)-γ, IL-1β, IL-1Ra, IL-2, IL-6, IL-8, and IL-10 (Lahat et al, 1997;Peltola et al, 1998Peltola et al, , 2000Kawakami et al, 1999a;Jain et al, 2000;Hulkkonen et al, 2004;Lehtimaki et al, 2004Lehtimaki et al, , 2011Lehtimäki et al, 2007;Tomoum et al, 2007;Carmeli et al, 2009;Haginoya et al, 2009;Liimatainen et al, 2009;Choi et al, 2011;Nowak et al, 2011;Behmanesh et al, 2012;Pollard et al, 2012). Eventually, with regard to the number of studies (a minimum of three studies for each cytokine), we performed meta-analyses for 14 studies: IL-1β in patients with FS versus patients with febrile illness without seizure (FWS): four studies (Lahat et al, 1997;Tomoum et al, 2007;Choi et al, 2011;Behmanesh et al, 2012), IL-1β in epileptic patients versus controls: five studies (Peltola et al, 2000;Hulkkonen et al, 2004;Lehtimäki et al, 2007;Nowak et al, 2011;…”

“…Further hand searching of references was performed and 17 related articles met the inclusion criteria and involved TNF-α, interferon (IFN)-γ, IL-1β, IL-1Ra, IL-2, IL-6, IL-8, and IL-10 (Lahat et al, 1997;Peltola et al, 1998Peltola et al, , 2000Kawakami et al, 1999a;Jain et al, 2000;Hulkkonen et al, 2004;Lehtimaki et al, 2004Lehtimaki et al, , 2011Lehtimäki et al, 2007;Tomoum et al, 2007;Carmeli et al, 2009;Haginoya et al, 2009;Liimatainen et al, 2009;Choi et al, 2011;Nowak et al, 2011;Behmanesh et al, 2012;Pollard et al, 2012). Eventually, with regard to the number of studies (a minimum of three studies for each cytokine), we performed meta-analyses for 14 studies: IL-1β in patients with FS versus patients with febrile illness without seizure (FWS): four studies (Lahat et al, 1997;Tomoum et al, 2007;Choi et al, 2011;Behmanesh et al, 2012), IL-1β in epileptic patients versus controls: five studies (Peltola et al, 2000;Hulkkonen et al, 2004;Lehtimäki et al, 2007;Nowak et al, 2011;Pollard et al, 2012), IL-1Ra in epileptic patients versus controls: four studies (Peltola et al, 2000;Hulkkonen et al, 2004;Lehtimäki et al, 2007;Liimatainen et al, 2009), IL-6 in epileptic patients vs. controls: 10 studies (Peltola et al, 1998(Peltola et al, , 2000Hulkkonen et al, 2004;Lehtimaki et al, 2...…”

“…Experimental studies demonstrate that inflammation and inflammatory mediators form the main causers and propagators of both febrile and epileptic seizures (Dubé et al, 2007;Vezzani et al, 2008Vezzani et al, , 2010. Accordingly, several case-control studies have investigated the concentration of cytokines in serum or cerebrospinal fluid (CSF) samples of seizure patients compared to controls without seizures (Lahat et al, 1997;Peltola et al, 1998Peltola et al, , 2000Kawakami et al, 1999a;Jain et al, 2000;Hulkkonen et al, 2004;Lehtimaki et al, 2004Lehtimaki et al, , 2011Lehtimäki et al, 2007;Tomoum et al, 2007;Carmeli et al, 2009;Haginoya et al, 2009;Liimatainen et al, 2009;Choi et al, 2011;Nowak et al, 2011;Behmanesh et al, 2012;Pollard et al, 2012). The fact that genetics have a leading role in the pathogenesis of FS (Waruiru and Appleton, 2004;Dubé et al, 2007;Heida et al, 2009;Wendorff and Zeman, 2011) has been proven by conducting various genetic studies including twin studies (Tsuboi, 1987;Corey et al, 1991;Berkovic et al, 1998;Miller et al, 1998Miller et al, , 1999Kjeldsen et al, 2002Kjeldsen et al, , 2005, familial studies (Nelson and Ellenberg, 1978;Knudsen, 1985;Annegers et al, 1987Annegers et al, , 1990…”

Realizing the Promise of Reverse Phase Protein Arrays for Clinical, Translational, and Basic Research: A Workshop Report

“…For single analytes, the approaches are routine. However, multiple analytes, of individually marginal significance, can potentially be combined to generate much better signals using simple ratios or more complex pathway analysis (98). This is especially true for ratios if one signal is elevated and the other is reduced.…”

“…In all cases, receiver operating condition curves, an absolute requirement in the pharmaceutical industry for validation of an assay, can unambiguously identify problems with false negative and false positive signals (71,98).…”