Identifizierung klinisch relevante Epitope der E.coli-Asparaginase mit Hilfe synthetischer Peptide

The enzyme L-asparaginase is a crucial component in the treatment of acute lymphoblastic leukaemia (ALL). As all asparaginases in clinical use are derived from microorganisms (with E.coli being the most frequent one), immunological reactions are the most important adverse events associated with asparaginase treatment. They range from clinically severe allergic shocks to silent enzyme inactivation without any clinical symptoms with the latter being particularly problematic in treatment schemes. For improving therapy success it is essential to identify patients prone to theses severe problems in advance. To date there is no such test being specific and sensitive enough to fulfil the purpose. Based on the assumption that the built antibodies are specific for epitopes, a lot of research has been done to classify the localisation within the enzyme more precisely. Concordant with previous results, the method used in this experiment (SPOTs Kit, enables synthesis of peptides on a cellulose membrane) showed the dominant sequence SVFDTLA (residues 252-258) when testing with a commercially available rabbit anti-E.coli-asparaginase antiserum but not with the serum of two healthy subjects. Considering the spatial position within the molecule and accessibility parameters, this sequence is highly likely to play a decisive role for immunological reactions as it blocks the enzymatic loop and thus the activity of the whole enzyme. The results achieved confirm the direction of research and help on the way of figuring out an epitope-specific assay. For statistically significant assertions further research has to follow.