Evaluation of spatial epitope computational tools based on experimentally-confirmed dataset for protein antigens

Antibody molecules interact with antigen proteins through the epitope area, where the epitope residues are found to be discontinuous or spatial or conformational rather than linear on the protein surface. There are various computational algorithms to predict the spatial epitopes, and each of them have an outstanding performance based on their individual testing dataset. In this work, an independent dataset was created through collection of the epitope residual sites which have been confirmed by experiments. Based on this dataset, 6 popular web-servers developed for B-cell structural epitope prediction, including SEPPA, CEP, DiscoTope, ElliPro, PEPOP and BEpro, were evaluated and compared according to sensitivity, the positive predictive value, the successful pick-up rate and the area under the curve of the receiver operator characteristic (AUC). The results showed that the general performance of spatial epitope prediction tools did obtain substantial advancement, and SEPPA gave the best performance among the 6 tools. However, the current prediction accuracy was still far from satisfaction. Moreover, our comparison elucidated that the performance of the web-servers was significantly affected by their training datasets and the algorithms adopted. In this sense, the results of our research may improve the design of B-cell epitope prediction tools and provide additional clues when the users utilize these tools in their related research.