APOA1 and bacterial infectious disease: In severe bacterial infections, HDL-C levels may be reduced due to either decreased production (decreased apoA1 production [12] and decreased lecithin–cholesterol acyltransferase activity [22,23]) or increased clearance (via raised serum amyloid A [24,25], increased serum phospholipase A2 and endothelial cell lipase activity, or enhanced triglyceride incorporation through cholesteryl ester transfer protein activity [26,27]).