Abstract
Objectives: Acute coronary syndrome (ACS) is the major cause of mortality worldwide and caused mainly by atherosclerosis of coronary arteries. Apolipoprotein B100 (ApoB100) is a major component of low-density lipoprotein (LDL) and its oxidation can trigger inflammation in vascular endothelial cells leading to atherosclerosis. The association between antibodies to ApoB100-derived antigens and atherosclerotic diseases has been studied in recent years, but the findings appear to be controversial. The present study developed an ELISA in-house with ApoB100-derived peptide antigens to circulating anti-ApoB100 IgG antibodies in patients with ACS. Methods: Fifteen ApoB100-derived peptide antigens (Ag1-Ag15) were designed to develop an in-house ELISA for the detection of circulating anti-ApoB100 IgG levels in 350 patients with ACS and 201 control subjects amongst a Chinese population. Binary logistic regression was applied to examine the differences in anti-ApoB IgG levels between the patient group and the control group with adjustment for a number of confounding factors; the correlation between anti-ApoB100 IgG levels and clinical characteristics was also tested. Results: Patients with ACS had significantly higher levels of plasma IgG for Ag1 (adjusted P<0.001) and Ag10 antigens (adjusted P<0.001). There was no significant increase in the levels of IgG to the other 13 antigens in these ACS patients. In the control group, anti-Ag10 IgG levels were positively correlated with age, high-density lipoprotein (HDL), and ApoA levels (P≤0.001 for all) and negatively correlated with blood triglyceride (TG) (P=0.008); in the patient group, anti-Ag10 IgG levels were positively correlated with LDL (P=0.003), and negatively correlated with ApoA (P=0.048) and systolic blood pressure (SBP) (P=0.036). The area under ROC (receiver operator characteristic) curve (AUC) was 0.612 (95% confidence interval (CI): 0.560-0.664; P<0.001) in anti-Ag1 IgG assay and 0.621 (95% CI: 0.569-0.672; P<0.001) in anti-Ag10 IgG assay. Conclusion: Circulating IgG for ApoB100-derived peptide antigens may be a useful biomarker of ACS, although anti-ApoB IgG levels were not associated with the coronary artery plaque burden characterized by the coronary Gensini score.