Establishment and evaluation of receptor binding domain (RBD)-based ELISA for Middle East re-spiratory syndrome coronavirus (MERS-CoV) antibody detection / 中华微生物学和免疫学杂志

ABSTRACT

Objective To establish an indirect enzyme-linked immunosorbent assay (ELISA)and to compare the efficiency of receptor binding domain (RBD) proteins in different forms for Middle East re-spiratory syndrome coronavirus (MERS-CoV) antibody detection. Methods The monomeric and trimeric forms of MERS-CoV RBD were expressed in Bac-insect cells, 293T cells and ExpiCHO-STM expression sys-tem and then purified. The purified RBD proteins were identified with native gel electrophoresis and Western blot. Then, an equal amount of each RBD protein was used as coating antigen to establish an ELISA for de-tecting MERS-CoV IgG titer. For comparison, the newly developed ELISA and the commercial MERS-CoV IgG antibody detection kit (Euroimmune with S1 as the coating antigen) were used to measure the MERS-CoV antibody reference panel supplied by World Health Organization (WHO). Results The purified mon-omeric and trimeric MERS-CoV RBD were successfully prepared using 293T cells and ExpiCHO-STM system. RBD antigens of different forms and from different systems could recognize MERS-CoV specific antibody without having any cross reaction with the sera from healthy adults. The in-house RBD-based ELISA had good detection consistency with the Euroimmune commercial kit. The positive samples showed higher and more concentrated values based on the RBD trimer than the monomer. Conclusions Novel indirect ELISA methods based on the monomeric and trimeric forms of RBD protein were established. The trimetric form-based ELISA achieved higher detection efficiency than the one using the monomer antigen, suggesting that it could be uses as a competent alternative to the commercial kit.