Capillary isoelectric focusing and affinity capillary electrophoresis approaches for the determination of binding constants for antibodies to the prion protein

For the development of specific immunological assays, the binding of a specific antibody (Ab) to the target antigen (Ag) has to be relatively strong. In this study, we have utilized affinity capillary electrophoresis (ACE), a form of capillary zone electrophoresis (CZE) to determine the binding constant (Kb) of specific Abs against bovine serum albumin (BSA) and the healthy prion protein (PrPc), in buffer solutions at fixed pHs, approximating in vivo conditions. We have also utilized capillary isoelectric focusing (cIEF) to determine the complexity and recognition of the various isoforms of PrPc Abs towards their Ag, PrPc. Only ACE and CZE have been used to derive Kb values. The selected Abs for the prion protein can recognize both healthy and diseased states of the protein and are commercially available. The Kb values of PrPc Abs appear to be as strong as the anti-BSA (Ab to BSA) and other reported Kb values for proteins of similar size to PrPc. This appears to be one of the few reports on Kb values for any PrPc Abs, and their applications for in vitro immunoassays (e.g., enzyme-linked immunosorbent assays (ELISAs)). Such assays are being used to detect the infectious agent, PrPres, in brain and related matter/tissues.