Computer-Assisted Modeling of Antibody Variable Domains

Antibody modeling is an interesting option to gain structure–function insights and to allow rational engineering of these molecules in the absence of experimental data. Among a diversity of algorithms, software packages, and specialized Web servers, the protocol described here presents the following main features: (1) nonautomatic modeling process guided by direct application of antibody modeling principles; (2) local generation of molecular models using free software which can be used in most common operational systems; and (3) the resulting model quality is comparable to models generated by Web servers which represent the current standard of antibody modeling. Briefly, hybrid models of heavy- and light-chain variable domains are separately built by grafting segments from homologous templates (framework regions and complementarity-determining regions). Next, hybrid models are mutated to comply with the target’s sequence and associated by fitting into a template structure that closely matches the predicted packing angle for the target variable domains. After a few cycles of energy minimization the model can be submitted to CDR-H3 optimization or its quality can be directly assessed.