Fine mapping epitope on glycoprotein Gc from Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonosis, caused by CCHF virus (CCHFV) and which there are no diagnostic or therapeutic strategies. The C-terminus of glycoprotein (Gc) encoded by the CCHFV M gene is responsible for CCHFV binding to cellular receptors and acts as a neutralizing-antibody target. In this study, a modified biosynthetic peptide technique (BSP) was used to identify fine epitopes of Gc from the CCHFV YL04057 strain using rabbit antiserum against CCHFV-Gc. Six B cell epitopes (BCEs) and one antigenic peptide (AP) were identified: E1 (⁸⁸VEDASES⁹⁴), E2 (¹¹⁷GDRQVEE¹²³), E3 (²⁴¹EIVTLH²⁴⁶), AP-4 (²⁸¹DFQVYHVGNLLRGDKV²⁹⁶), E5a (³⁷⁰GDTP QLDL³⁷⁷), E5b (³⁷³PQLDLKAR³⁸⁰), and E6 (⁴⁴³HVRSSD⁴⁴⁸). Western blotting analysis showed that each epitope interacted with the positive serum of sheep that had been naturally infected with CCHFV, and the results were consistent with that of Dot-ELISA. The multiple sequence alignment (MSA) revealed high conservation of the identified epitopes among ten CCHFV strains from different areas, except for epitopes AP-4 and E6. Furthermore, three-dimensional structural modeling showed that all identified epitopes were located on the surface of the Gc "head" domain. These mapped epitopes of the CCHFV Gc would provide a basis for further increase our understanding CCHFV glycoprotein function and the development of a CCHFV epitope-based diagnostics vaccine and detection antigen.