An immunoassay has been used to assess the extent of brain damage following head injuries or concussion in sportsmen involved in contact sports.
The enzyme-linked immunosorbent assay (ELISA) measured the levels of the astrocytic protein S100B which is normally only found in the brain, but leakage into the blood indicates blood-brain barrier disruption (BBBD) which may cause an immune response associated with production of autoantibodies.
Scientists at the Cleveland Clinic (Cleveland, OH, USA) and the University of Rochester (NY, USA) enrolled 67 volunteers from three American college football teams and collected blood samples before and after matches. The serum levels of S100B and autoantibodies against S100B were measured and correlated by direct and reverse immunoassays. Computerized cognitive testing, diffusion tensor imaging, and an estimation of head hits were also carried out.
The S100B measurements were performed using an ELISA kit (Diasorin; Saluggia, Italy) and reading carried out on a multiplate fluorescent reader. Fluorescent signals were converted into ng/mL as per standard curve concentrations. Serum S100B autoantibody measurements were optimized using a monoclonal antibody (Meridian Life Science Inc.; Cincinnati, OH, USA) in an ELISA system and read on a plate reader at 490 nm.
The investigators found elevations of serum S100B indicating blood-brain barrier disruption occur in football players who experience subconcussive head hits (SHH) below the threshold for a diagnosis of concussion. They also showed that players who during a season experience the most significant repeated elevations of S100B are also those with the highest titer of serum S100B autoantibodies. Out of the 27 players who had preseason S100b blood levels measured, four showed signs of an autoimmune response to the protein. Brain tissue damage was confirmed in the players through a series of brain scans.
Damir Janigro, PhD, the senior author of the study said, "Think of the blood-brain barrier disruption as opening a door to the brain that should not be open. Proteins like S100B, which normally stay inside the brain, get out where they are not supposed to be and get attacked. In addition, the door is open for things that do not belong in the brain to get in." The blood test is a great deal less expensive at around USD 40 than other means of evaluating the extent of head trauma, such as computed axial tomography (CAT) scans. The study was published on March 6, 2013, in the journal Public Library of Science ONE (PLOS ONE).