Identification of plasma biomarkers for the (early) diagnosis of coronary artery disease using autoantibody profiling

The leading cause of cardiovascular death worldwide is coronary artery disease (CAD), which is a
chronic inflammatory disease characterised by a lipid plaque formation in the coronary artery wall
thereby causing obstruction of blood flow. Up to now coronary angiography, an invasive cardiac
catheterization method, remains the gold standard to diagnose these lesions and coronary disease.
Therefore, this study aimed to identify novel (auto-)antibody biomarkers for early diagnosis of CAD
from minimally invasive liquid biopsies.
In the first project phase, IgG samples, purified from plasma of healthy, sclerotic and stenotic patients,
were tested on a high-density microarray presenting 15,456 recombinant human proteins expressed
from E.coli cDNA clones. The thereby identified 242 candidate protein markers were expressed and
purified from the cDNA clones and tested in a side-by-side marker confirmation on a planar targeted
microarray and a bead-based multiplexed Luminex assay. The multivariate prediction models based
on 17-20 promising protein biomarkers for each group identified via pairwise class comparison of the
three sample groups (healthy, sclerosis, stenosis) in the microarray data set showed highest AUC
values of 0.731 and 0.748, while the Luminex data showed less predictive power and only minor
overlap in identified features with the microarray data. Additionally, antibody signatures against
microbial pathogens were investigated on a microarray, harbouring crude protein lysates obtained
from 253 bacterial and 7 fungal strains. This study identified elevated IgG reactivity specific for
multiple Klebsiella pneumoniae strains exclusively in the stenosis group.
In conclusion, several promising (auto-)antibody biomarkers have been identified, which might
improve future minimally-invasive diagnosis and risk stratification in CAD patients.