The production and use of monoclonal antibodies to measure apolipoprotein B by a competitive enzyme-linked immunoassay

The relationship of serum total sialic acid with serum acute phase proteins and lipoprotein (a) in patients with severe hypertriglyceridaemia

Total serum sialic acid (TSA), recently shown to be a cardiovascular risk factor, was measured in 15 patients with severe hypertriglyceridaemia (fasting triglyceride > 2.3 mmol l-1) and 15 age and sex matched normal control subjects. To test the hypothesis that serum TSA is related in some way to serum acute phase proteins we also measured five acute phase proteins, namely alpha-1-antichymotrypsin (ACT), alpha-1-acid-glycoprotein (AGP), alpha-2-macroglobulin (AMG), C-reactive protein (CRP) and haptoglobin (HAP) in both groups. Of note was the significantly elevated serum TSA in the severely hypertriglyceridaemic group as compared to normal subjects. Serum TSA being 71.9 +/- 11.7 mg dl-1 and 59.6 +/- 10.2 mg dl-1 respectively (P < 0.01 Mann-Whitney test). Serum CRP was significantly elevated in the type IV patients as compared to controls (6.4 +/- 4.5 mg l-1 vs. 3.3 +/- 1.9 mg l-1 P < 0.05 Mann Whitney test) as was serum AMG (2.1 +/- 0.89 g l-1 vs. 1.5 +/- 0.53 g l-1 P < 0.05 Mann Whitney test). There was no correlation between serum TSA and lipoprotein (a) in either the normal or severely hypertriglyceridaemic subjects. We suggest that serum TSA could in part be related to hypertriglyceridaemia and serum acute phase proteins but that its property as a cardiovascular risk factor is not related to serum lipoprotein (a) concentrations.

Monoclonal antibodies to human A-I apolipoprotein and characterisation of cyanogen bromide fragments of apoA-I

Several monoclonal antibodies to human A-I apolipoprotein were produced after immunising mice with pure delipidated apoA-I. These monoclonal antibodies were characterised for their ability to react with whole lipoproteins, apolipoproteins and fragments of apoA-I generated by cleavage with cyanogen bromide. The data suggest that production of monoclonal antibodies using apoA-I as antigen was influenced by two major epitopes subsequently localised to cyanogen bromide fragments 1 and 3, and have been designated antibodies 1----5 A-IB and 6----10 A-IB, respectively. Cyanogen bromide fragments were first purified to homogeneity before screening by competitive displacement or immunoblotting procedures. Definitive characterisation of one antibody series (1----5 A-IB) depended ultimately on Western blotting following isoelectric focusing of purified apoA-I fragments. This technique identified the epitope for these antibodies to fragment 1, an identification not fully concluded from competitive displacement studies. These studies have also revealed the presence of microheterogeneity in fragment 1 (as well as in fragment 4) of apoA-I, suggesting that structural variations in several regions may account for the polymorphism observed in this apolipoprotein.