A LiTat 1.5 variant surface glycoprotein-derived peptide with diagnostic potential for Trypanosoma brucei gambiense.

Objective: To evaluate the accuracy of a peptide, corresponding to the variant surface glycoprotein (VSG) LiTat 1.5 amino acid (AA) sequence 268-281 and identified through alignment of monoclonal antibody selected mimotopes, for diagnosis of Trypanosoma brucei gambiense sleeping sickness.

Methods: A synthetic biotinylated peptide (peptide 1.5/268-281), native VSG LiTat 1.3 and VSG LiTat 1.5 were tested in an indirect ELISA with 102 sera from patients with HAT and 102 endemic HAT-negative controls.

Results: The area under the curve (AUC) of peptide 1.5/268-281 was 0.954 (95% confidence interval 0.918-0.980), indicating diagnostic potential. The areas under the curve of VSG LiTat 1.3 and LiTat 1.5 were 1.000 (0.982-1.000) and 0.997 (0.973-1.000), respectively, and significantly higher than the AUC of peptide 1.5/268-281. On a model of VSG LiTat 1.5, peptide 1.5/268-281 was mapped near the top of the VSG.

Conclusions: A biotinylated peptide corresponding to AA 268-281 of VSG LiTat 1.5 may replace the native VSG in serodiagnostic tests, but the diagnostic accuracy is lower than for the full-length native VSG LiTat 1.3 and VSG LiTat 1.5.