Recombinant Receptor Binding Domain Protein Induces Partial Protective Immunity in Rhesus Macaques Against Middle East Respiratory Syndrome Coronavirus Challenge()

Lan, Jiaming; Yao, Yanfeng; Deng, Yao; Chen, Hong; Lu, Guangwen; Wang, Wen; Bao, Linlin; Deng, Wei; Wei, Qiang; Gao, George F.; Qin, Chuan; Tan, Wenjie

To assess the humoral immune response to the rRBD vaccine in rhesus macaques, total anti-MERS-CoV RBD IgG antibody titres were determined by ELISA. Low titres of IgG in serum samples before prime vaccination were detected, possibly due to non-specific responses. IgG titres in the high-dose group increased significantly (p b 0.05) after the first vaccination (Fig. 2a) , and achieved the highest titre of RBDspecific IgG 2 weeks after the second immunisation. Sera IgG titre in the low-dose group increased (p b 0.05) only after the second immunisation, to almost the same level as that of the high-dose group. RBD-specific IgG in the sera of immunised rhesus macaques was preserved for at least 17 weeks without obvious decline. In addition, IgG titre increased rapidly after a subsequent boost. Increased IgG titre was particularly marked in the low-dose group.