利用MHC-Ⅰ人源化小鼠与转基因疟原虫建立恶性疟原虫环子孢子蛋白疫苗评价模型:抗体应答有效而CD8+T细胞应答受限OA

Objective To investigate whether the MHC-Ⅰ humanized mouse model(AAD mice)combined with the Plasmodium berghei transgenic strain expressing Plasmodium falciparum circumsporozoite protein(PfCSP,Pb-PfCSP)can be used to establish an evaluation model for PfCSP-based vaccines.Methods AAD mice and C57BL/6J mice(6 to 8 weeks old,body weight 20 to 35 g,4 mice per group)were challenged with graded doses(200,500,and 1 000)of Pb-PfCSP sporozoites and wild-type P.berghei(Pb)sporozoites via tail vein injection.The susceptibility of the 2 mouse strains to Pb and Pb-PfCSP infection was compared by monitoring the onset time of erythrocytic-stage parasitemia and the dynamic changes in parasitemia levels.Flow cytometry was performed to analyze the frequency and absolute number of major hepatic immune cell subsets in the 2 mouse strains,so as to preliminarily explore the potential mechanisms underlying the differential susceptibility to malaria parasites.For vaccine efficacy evaluation,4 AAD mice per group were immunized with either CI-679-attenuated Pb-PfCSP sporozoite vaccine or LNP-encapsulated mRNA vaccine encoding PfCSP(PfCSP@LNP),with unimmunized AAD mice as the control group.After immunization,all mice were challenged with Pb-PfCSP sporozoites,and the protective efficacy was evaluated.The frequency and number of CSP-specific tissue-resident memory T cells(Trm)in the liver were detected by flow cytometry,and CSP-specific antibody titers in serum were measured by enzyme-linked immunosorbent assay(ELISA).Results Pb-PfCSP sporozoites at all tested doses successfully infected both AAD and C57BL/6J mice.Compared with C57BL/6J mice,AAD mice exhibited higher susceptibility to both Pb and Pb-PfCSP infection,as evidenced by earlier onset of erythrocytic-stage parasitemia and significantly higher parasitemia levels in the mid-stage of infection(P<0.05).Regardless of infection status,the frequency and absolute number of hepatic natural killer T(NKT)cells in AAD mice were significantly lower than those in C57BL/6J mice(P<0.05),which might be one of the reasons for the increased susceptibility of AAD mice to malaria parasite infection.After challenge with Pb-PfCSP sporozoites,PfCSP@LNP-immunized AAD mice exhibited delayed erythrocytic-stage parasitemia onset compared with the control group,and detectable titers of CSP-specific antibodies were observed in their serum;however,PfCSP-specific Trm cells were not detected in the liver.Similarly,AAD mice immunized with the nitroquine-attenuated Pb-PfCSP sporozoite vaccine only achieved a protective efficacy of 16.6%,and PfCSP-specific Trm cells were not detected either.Conclusion The Pb-PfCSP-infected AAD mouse model can be used for evaluating the efficacy of PfCSP-based vaccines in inducing CSP-specific antibody responses.However,this model requires further optimization for assessing PfCSP-specific CD8+T cell response induction.