Subunit vaccines with a saponin-based adjuvant boost humoral and cellular immunity to MERS coronavirus
Chi-Chieh Chang, Abdullah Algaissi, Chia-Chun Lai, Chun-Kai Chang, Jr‐Shiuan Lin, Yi‐Shiang Wang, Bo-Hau Chang, Yu-Chiuan Chang, Wei‐Ting Chen, Yong-Qing Fan, Bi‐Hung Peng, Chih-Yu Chao, Shiou‐Ru Tzeng, Pi‐Hui Liang, Wang‐Chou Sung, Alan Yung-Chih Hu, Shin C. Chang, Ming‐Fu Chang
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) outbreaks have constituted a public health issue with drastic mortality higher than 34%, necessitating the development of an effective vaccine. During MERS-CoV infection, the trimeric spike protein on the viral envelope is primarily responsible for attachment to host cellular receptor, dipeptidyl peptidase 4 (DPP4). With the goal of generating a protein-based prophylactic, we designed a subunit vaccine comprising the recombinant S1 protein with a trimerization motif (S1-Fd) and examined its immunogenicity and protective immune responses in combination with various adjuvants. We found that sera from immunized wild-type and human DPP4 transgenic mice contained S1-specific antibodies that can neutralize MERS-CoV infection in susceptible cells. Vaccination with S1-Fd protein in combination with a saponin-based QS-21 adjuvant provided long-term humoral as well as cellular immunity in mice. Our findings highlight the significance of the trimeric S1 protein in the development of MERS-CoV vaccines and offer a suitable adjuvant, QS-21, to induce robust and prolonged memory T cell response.