Studies on Deimmunization of Antileukaemic L-Asparaginase to have Reduced Clinical Immunogenicity--An in silico Approach.

Protein therapeutics, particularly of heterologous origin are shown to elicit immunogenic responses which result in adverse allergic reactions in spite of their promising clinical benefit. L-Asparaginase is one such well known chemotherapeutic agent that has enhanced the survival rates to 90 % in the treatment of acute lymphoblastic leukaemia for past 30 years. But the use of this enzyme is accompanied by hypersensitive reactions ranging from allergy to anaphylactic shock which have a drastic influence in treatment outcomes. Numerous attempts have been made to minimize the problems of immunogenicity, which remained as a major bottleneck in the treatment protocols. Conjugating the enzyme L- Asparaginase with PEG was successful as it has reduced the complications in therapy and frequency of injections (dosages), and thus became prominent in reducing the immunogenicity up to a certain extent. Keeping the bottlenecks in consideration during the development of therapeutics, the present study concentrates on engineering of protein as an alternative to the PEGylated enzyme, having reduced immunogenicity as an inbuilt character of protein by using in silico approaches. L-Asparaginase from Escherichia coli and Pectobacterium carotovorum were selected for the present study. The methodology consists of (i) locating the B and CD4+ T cell epitopes of enzyme by in silico tools (ii) generating point mutations of these epitopes to alter or reduce the immunogenicity of protein (iii) generating enzyme models by molecular modelling (iv) assessing the binding affinity of the substrate with L-Asparaginase variants by in silico docking methods using Autodock 4.2 and (v) validating the mutated model for stability by molecular dynamics simulation studies using Gromacs.