Abstract： Aim To prepare the mucosal adjuvants of Chi-CpG NP,and subsequently immunize mice with recombinant Neisseria meningitides serogroup B 0315 protein(rNMB0315)by using Chi-CpG NP before the observation of immunostimulatory effects.Methods The physicochemical characteristics and safety of Chi-CpG NP were assessed by incorporating immunopotentia-tors(CpG-ODN)into Chitosan nanoparticles(Chi NP).Female BALB/c mice were immunized intranasally with various mucosal immune adjuvants containing the rNMB0315 protein.On days 42 days after immunization,the humoral(IgG,IgG1,IgG2a,sIgA),cellular(interleukin 4,interferon-γ,interleukin 17A)immunologic responses,as well as the serum bactericidal assay and immune protective effect,were evaluated in the PBS,rNMB0315,rNMB0315+CpG,rNMB0315+Chi NP,and rNMB0315+Chi-CpG NP groups.Results The Chi-CpG nanoparticles demonstrated favorable adsorption and safety properties and exhibited a spherical morphology.On days 42 days after immunization,the levels of humoral and cellular immunity in the rNMB0315+Chi NP group and rNMB0315+Chi-CpG NP group were higher than those in the rNMB0315 group(P＜O.05).Moreover,the rNMB0315+Chi-CpG NP group elicited a higher level of humoral and cellular immunity than the rNMB0315+CpG,or the rNMB0315+Chi-NP group(P＜0.05).After a lethal dose of Neiseria meningitids serogroup B infection,the survival rate of mice in the rNMB0315+Chi-CpG NP group was the highest,with serum bactericidal titers of 1∶4 against this strain.Conclusion Chi-CpG NP has been successfully prepared.Chi-CpG NP can enhance the immune effects of rNMB0315 protein and improve the survival rate of mice.