Abstract

Membrane Lipid Affinity Chromatography: A Novel Technique to Isolate Exosomes and Other Vesicular Sub-populations for Plasma Biomarker Discovery

Sai Kiang Lim, Research Director, A*STAR Institute of Medical Biology

Intercellular communication via secreted lipid membrane vesicles or extracellular vesicles (EVs) is an emerging research area. The best characterized EV to date is the 100 nm exosome. We recently discovered that beside exosome, cells also secrete many different 100 nm EV types. These EVs can be uniquely differentiated and isolated by their high affinity for different lipid-binding proteins such as cholera toxin B chain (CTB) that binds GM1 ganglioside, AnnexinV (AV) that binds phosphatidylserine and Shiga toxin B chain (STB) that binds globotriasosylceramide. As in cell secretions, CTB and AV also bind unique EV types from the plasma. Hence plasma biomarkers can now be analyzed in three permutations: plasma, plasma CTB-EVs and plasma AV-EVs. The distribution of some plasma proteins in these three permutations is disease specific and therefore diagnostic. I will illustrate the utility of these three permutations in developing highly sensitive and specific plasma biomarkers for predicting pre eclampsia (PE). Three biomarkers, A, B and C whose levels in plasma, plasma CTB-EV and plasma AV-EV in 28-32 weeks pregnant women were significantly different between those who did not develop PE from those who subsequently developed PE at an average of seven weeks later. This study was done using a prospective biobank of 843 low risk patients with a 2.1% PE risk. At 100% sensitivity, the three biomarkers have a combined AUC of 0.96, 78.6% specificity and a PPV of 9.9%.