A Francisella tularensis Live Vaccine Strain (LVS) Mutant with a Deletion in capB, Encoding a Putative Capsular Biosynthesis Protein, Is Significantly More Attenuated than LVS yet Induces Potent Protective Immunity in Mice against F. tularensis Challenge
A Francisella tularensis Live Vaccine Strain (LVS) Mutant with a Deletion in capB, Encoding a Putative Capsular Biosynthesis Protein, Is Significantly More Attenuated than LVS yet Induces Potent Protective Immunity in Mice against F. tularensis Challenge
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DOI：
10.1128/iai.00192-10
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发表时间：
2010-10-01
影响因子：
3.1
通讯作者：
Horwitz, Marcus A.
中科院分区：
文献类型：
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作者：
Jia, Qingmei;Lee, Bai-Yu;Horwitz, Marcus A.
土拉热弗朗西斯菌是土拉菌病的病原体，属于生物恐怖主义潜在病原体的顶级类别（A类）。食品药品管理土拉热活疫苗株（LVS）是目前唯一可用于预防土拉菌病的疫苗;然而，这种未经许可的疫苗毒性相对较大，并且对雾化的F.土拉热是最危险的传播方式因此，需要一种更安全、更有效的疫苗。作为解决这一需求的第一步，我们构建并表征了LVS的减毒版本，LVS Delta capB，既作为更安全的疫苗，又作为表达重组F.土拉菌蛋白。LVS Delta capB在推定的胶囊合成基因（capB）中具有靶向缺失，不含抗生素抗性标记。LVS Delta capB保留免疫保护性O抗原，具有血清抗性，并且在竞争测定中在人巨噬细胞样THP-1细胞中生长超过亲本LVS。LVS Delta capB在小鼠中显著减弱;鼻内（i. n.）是LVS的10，000倍以上。将CapB反式提供给LVS Delta capB部分地恢复了其在小鼠中的毒力。用LVS Delta capB i.n.或皮内（i.d.）产生了与用LVS免疫的小鼠相当的体液和细胞免疫应答，并且当在4或8周后用致死剂量的LVS i. n.攻击时，与假免疫小鼠相比，它们100%免于生病和死亡，并且在肺、肝和脾中具有显著较低水平（3至5log）的LVS。最重要的是，用LVS Delta capB i.或I.D.然后在6周后用10倍于高毒力A型F的LD 50的气雾剂攻击。土拉热菌菌株SchuS 4显著保护（i. n.免疫）。这些结果表明，LVS Delta capB比LVS安全得多，而且还提供了针对强毒F.土拉菌SchuS 4攻毒。
Francisella tularensis, the causative agent of tularemia, is in the top category (category A) of potential agents of bioterrorism. The F. tularensis live vaccine strain (LVS) is the only vaccine currently available to protect against tularemia; however, this unlicensed vaccine is relatively toxic and provides incomplete protection against aerosolized F. tularensis, the most dangerous mode of transmission. Hence, a safer and more potent vaccine is needed. As a first step toward addressing this need, we have constructed and characterized an attenuated version of LVS, LVS Delta capB, both as a safer vaccine and as a vector for the expression of recombinant F. tularensis proteins. LVS Delta capB, with a targeted deletion in a putative capsule synthesis gene (capB), is antibiotic resistance marker free. LVS Delta capB retains the immunoprotective O antigen, is serum resistant, and is outgrown by parental LVS in human macrophage-like THP-1 cells in a competition assay. LVS Delta capB is significantly attenuated in mice; the 50% lethal dose (LD50) intranasally (i.n.) is > 10,000-fold that of LVS. Providing CapB in trans to LVS Delta capB partially restores its virulence in mice. Mice immunized with LVS Delta capB i.n. or intradermally (i.d.) developed humoral and cellular immune responses comparable to those of mice immunized with LVS, and when challenged 4 or 8 weeks later with a lethal dose of LVS i.n., they were 100% protected from illness and death and had significantly lower levels (3 to 5 logs) of LVS in the lung, liver, and spleen than sham-immunized mice. Most importantly, mice immunized with LVS Delta capB i.n. or i.d. and then challenged 6 weeks later by aerosol with 10x the LD50 of the highly virulent type A F. tularensis strain SchuS4 were significantly protected (100% survival after i.n. immunization). These results show that LVS Delta capB is significantly safer than LVS and yet provides potent protective immunity against virulent F. tularensis SchuS4 challenge.