Immunotherapy: Open Access
Open Access

Abstract

The Effect of Adjuvants and Immune Routes on the Immunodominance of Epitopes and Protection Efficacy of SARS-CoV-2 RBD Antigen

Sisi Li, Lianli Duan, Xiaoli Zhang, Rui Yang, Longlong Chen, Zhifu Chen, Qiang Gou, Wenxin Bao, Yue Yuan, Haiming Jing, Yi Zhang, Ping Cheng, Ping Luo, Li Ni*, Wanneng Wang* and Zhuo Zhao*

Previous studies have revealed that the Receptor-Binding Domain (RBD) of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) spike protein is immunogenic in both mice and healthy volunteers, and humoral immune response plays a key role in RBD-mediated protection. In this study, we investigated the immunogenicity and protective efficacy of immunization with RBD plus three different adjuvants (Al(OH)₃, ASO₃, and AddaVax) against SARS-CoV-2 pseudo virus through two different routes (intramuscular or intranasal immunization) in mice. The results showed that the immunogenicity and titer of neutralizing antibodies changed in response to different adjuvants and immune routes. Furthermore, six B-cell immunodominant epitopes (RBD_1-18, RBD_49-66, RBD_61-78, RBD_97-114, RBD_139-156, and RBD_145-162) in RBD were identified using antisera from a different immunized group, which may explain the differences in protection observed in each immunized group. Through sequence alignment, we found that six B-cell epitopes are highly conserved among different SARS-COV-2 variants (including Alpha-, Beta-, Gamma- and Omicron-Variant). This study indicated that the immunodominance of epitopes and protection efficacy of RBD antigen are different by different adjuvants and immune routes, which may further guide adjuvant screening for vaccine development and optimization.

Published Date: 2023-01-10; Received Date: 2022-12-05