Galen J E, Gomez-Duarte O G, Losonsky G A, Halpern J L, Lauderbaugh C S, Kaintuck S, Reymann M K, Levine M M
Department of Medicine, University of Maryland School of Medicine, Baltimore 21201-1509, USA.
Vaccine. 1997 Apr-May;15(6-7):700-8. doi: 10.1016/s0264-410x(96)00227-7.
The lack of a practical small animal model to study the immunogenicity of Salmonella typhi-based live vector vaccines expressing foreign antigens has seriously impeded the vaccine development process. For some foreign antigens, stimulation of serum IgG antibody is the desired, protective immune response. We administered to mice, by orogastric or intranasal (i.n.) routes, attenuated delta aroC delta aroD S. typhi CVD 908 carrying a plasmid encoding fragment C (fragC) of tetanus toxin fused to the eukaryotic cell receptor binding domain of diphtheria toxin (fragC-bDt), and monitored serum antibody. While orogastric inoculation of three doses was not immunogenic, i.n. immunization elicited high titers of serum IgG tetanus antitoxin, generating peak ELISA geometric mean titers (GMT) of 27024 and 35658 with 10(8) and 10(9) c.f.u. dosages, respectively; 10(9) c.f.u. i.n. of an delta aroA S. typhimurium live vector stimulated a peak antitoxin GMT of 376 405. Mice immunized with the S. typhi live vector were 100% protected against challenge with 100 50% lethal doses of tetanus toxin that rapidly killed all control mice. Intranasal immunization with two doses of S. typhi expressing unfused fragment C under control of an anaerobically-activated promoter derived from nirB stimulated significantly higher titers of serum neutralizing antitoxin than fused fragC-bDt controlled by the same promoter (GMT 0.10 AU ml-1 vs 0.01 AU ml-1, P = 0.0095). Two i.n. doses of S typhi encoding fragC under control of powerful constitutive promoter 1pp led to significantly higher peak serum neutralizing antitoxin titers than the otherwise identical construct utilizing the nirB promoter (peak GMT 0.72 AU ml-1 vs 0.10 AU ml-1, P = 0.022). The i.n. route of inoculation of mice may constitute a practical breakthrough that could expedite the development of some S. typhi-based live vector vaccines by allowing, for the first time, quantitative measurement of serum antibody responses to candidate constructs following i.n. mucosal immunization.
缺乏用于研究表达外源抗原的伤寒沙门氏菌活载体疫苗免疫原性的实用小动物模型，严重阻碍了疫苗的研发进程。对于某些外源抗原而言，刺激血清IgG抗体是理想的保护性免疫反应。我们通过灌胃或鼻内（i.n.）途径给小鼠接种携带编码破伤风毒素片段C（fragC）与白喉毒素真核细胞受体结合域融合体（fragC-bDt）的质粒的减毒ΔaroCΔaroD伤寒沙门氏菌CVD 908，并监测血清抗体。虽然灌胃接种三剂没有免疫原性，但鼻内免疫引发了高滴度的血清IgG破伤风抗毒素，10⁸和10⁹cfu剂量分别产生ELISA几何平均滴度（GMT）峰值27024和35658；10⁹cfu的鼠伤寒沙门氏菌ΔaroA活载体鼻内接种刺激抗毒素GMT峰值为376405。用伤寒沙门氏菌活载体免疫的小鼠对100个50%致死剂量的破伤风毒素攻击有100%的保护作用，这些毒素能迅速杀死所有对照小鼠。在源自nirB的厌氧激活启动子控制下，用两剂表达未融合片段C的伤寒沙门氏菌进行鼻内免疫，刺激产生的血清中和抗毒素滴度显著高于相同启动子控制下的融合fragC-bDt（GMT 0.10 AU ml⁻¹对0.01 AU ml⁻¹，P = 0.0095）。在强大的组成型启动子1pp控制下，两剂鼻内接种编码fragC的伤寒沙门氏菌导致血清中和抗毒素峰值滴度显著高于使用nirB启动子的相同构建体（峰值GMT 0.72 AU ml⁻¹对0.10 AU ml⁻¹，P = 0.022）。小鼠鼻内接种途径可能构成一项实用的突破，通过首次允许在鼻内黏膜免疫后对候选构建体的血清抗体反应进行定量测量，从而加速一些基于伤寒沙门氏菌的活载体疫苗的研发。
