Blood-based biomarker discovery for acute ischemic stroke

Acute ischemic stroke (AIS) is a major public health problem, and its treatment is time-dependent. Most patients do not receive treatment due to a delay in diagnosis, which requires specialized clinical expertise and neuroimaging equipment. A blood test for AIS would address this unmet need by identifying patients with AIS so they can undergo prompt treatment. Previous studies have been unsuccessful in developing a blood-based biomarker test for AIS by measuring the concentration of specific circulating proteins, for several reasons. First, the use of biased proteomic analysis means that specific targets are chosen prior to testing, which limits the number of proteins assessed for a relationship to AIS. Second, 22 proteins make up >95% of circulating protein mass, so small changes in less abundant proteins in relation to AIS are hard to quantify with existing methods. Finally, because the onset of AIS is generally not known in advance, studies attempting to determine AIS- associated proteins lack a within-subject control. Instead, previous attempts measured the different concentrations of a limited set of plasma proteins after AIS has occurred, and compared them to healthy non-AIS controls, limiting the identification of proteins directly related to AIS (as opposed to those whose differences were due to between-subject variability). We seek to overcome these challenges through an innovative approach to AIS biomarker discovery. We have developed a novel method of rapid, untargeted mass spectrometry for the proteomic analysis of extracellular vesicles (EVs), which contain ~6,000 different proteins. This permits the investigation of a large set of proteins which that may not have been previously related to AIS. We will use this method to study patients undergoing elective aortic arch surgery, in which the intraoperative AIS rate is ~75%. By obtaining blood immediately prior to and after such surgery, we can measure the change in protein concentration within each patient in the pre- and post-stroke condition, determining which proteins change only in relation to the presence and extent of intraoperative AIS. The end result will be a targeted assay for a set of plasma proteins whose concentrations indicate the presence and extent of AIS, establishing a blood test for AIS diagnosis. This panel of proteins can then be prospectively tested in a future study of AIS patients and “stroke mimics” for definitive analytic and clinical validation.

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Sponsor: American Heart Association