PBMC isolation and total RNA extraction
In this study, the whole blood from 3 mice in each group mentioned above was collected in an ethylenediaminetetraacetic acid dipotassium (EDTA) anticoagulant tube three weeks after the last immunization, and then isolated peripheral blood mononuclear cells (PBMCs) with the Mouse PBMC Isolation Kit (Haoyang Biological Products Technology, Tianjin, China). Total RNA was extracted from PBMCs using TRIzol Reagent (Life Biotechnology, Shanghai, China) according to the manufacturer’s instructions.