A high-throughput biotin-avidin-ELISA for studying expression of platelet membrane glycoproteins and its clinical application.

Platelet membrane glycoproteins (GPs) are critical for normal platelet adhesion, activation and aggregation. To define the abnormalities in surface GP expression on circulating platelets and provide a better biomarker of bleeding and thrombotic disorders, we have developed a accurate, time-saving and high-throughput biotin-avidin enzyme-linked immunosorbent assay (BA-ELISA) with the monoclonal antibodies (mAbs), 7E3 against the complex of GPIIb and GPIIIa (GPIIb/IIIa), SZ-51 against P-selectin, and SZ-2 against GPIb, respectively. The levels of P-selectin and GPIIb/IIIa were measured in patients with acute myocardial infarction (AMI), intracerebral hemorrhage (ICH), or diabetes mellitus (DM)) and healthy subjects. Inhibition of GP expression was evaluated with SZ-21, an inhibitory mAb against GPIIIa and aspirin, respectively. The sensitivity of BA-ELISA is high enough to detect platelet count as low as 3.13 x 10(9)/L in platelet-rich plasma (PRP). Both the inter-assay and intra-assay coefficient variation are less than 10%. Adenosine diphosphate (ADP)-induced or non-ADP-induced expression of P-selectin and GPIIb/IIIa was significantly higher in AMI, ICH or DM than that in controls (P < 0.01 for each). Either SZ-21 or aspirin can inhibit the ADP-induced expression of P-selectin and GPIIb/IIIa. Importantly, a high correlation was detected between BA-ELISA and flow cytometry methods. These observations indicate that BA-ELISA is a sensitive and high-throughput assay for evaluating platelet GP expression. The newly developed BA-ELISA can be popularized in community hospitals, because it does not require sophisticated equipments and reagents. This method is suitable for screening inhibitors of platelet activation and has a potential in use for diagnostic purposes.