Cellular prion protein (PrPC) is a glycoprotein. It has several biological functions in the body, among which are cell adhesion, intracellular signaling, maintenance of ion homeostasis, and protection of neurons. It is also associated with the development of neurodegenerative diseases. PrPC is shed by the ADAM 10 protease, which result in the formation of shed PrP that lack GPI-anchor. It floats freely in body fluids and binds to PrPSc aggregates, preventing them from multiplying. The problem, however, arises when PrPSc aggregates bind PrPC and convert them into PrPSc, which is then released from the membrane by ADAM 10 protease. This can lead to the development of neurodegenerative diseases. Because of this role, we focus on detecting shed PrP in the blood, with focus on PrP226*, which is an outstanding biomarker for the diagnosis of prion diseases. The aim of this work was to develop a reliable ELISA screening to determine the presence of shed PrP (PrP226*) in blood donor plasma samples using mAb V5B2 as a primary antibody and using mAb E12/2 as a detection antibody. The sensitivity of the test was determined, and then 484 blood donor plasma samples were tested. After screening, we came to the conclusion that due to the presence of heterophile antibodies (HA) we received false positive test results. The presence of HA in the sample was confirmed using commercially available antibodies. We then tried to extract HA from the sample using various methods.
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