There is a need for development of an effective vaccine against Francisella tularensis, as this potential bioweapon has a high mortality rate and low infectious dose when delivered via the aerosol route. Moreover, this Tier 1 agent has a history of weaponization. We engineered targeted mutations in the Type A strain F. tularensis subspecies tularensis Schu S4 in aro genes encoding critical enzymes in aromatic amino acid biosynthesis. F. tularensis Schu S4ΔaroC, Schu S4ΔaroD, and Schu S4ΔaroCΔaroD mutant strains were attenuated for intracellular growth in vitro and for virulence in vivo and, conferred protection against pulmonary wild-type (WT) F. tularensis Schu S4 challenge in the C57BL/6 mouse model. F. tularensis Schu S4ΔaroD was identified as the most promising vaccine candidate, demonstrating protection against high-dose intranasal challenge; it protected against 1,000 CFU Schu S4, the highest level of protection tested to date. It also provided complete protection against challenge with 92 CFU of a F. tularensis subspecies holarctica strain (Type B). Mice responded to vaccination with Schu S4ΔaroD with systemic IgM and IgG2c, as well as the production of a functional T cell response as measured in the splenocyte-macrophage co-culture assay. This vaccine was further characterized for dissemination, histopathology, and cytokine/chemokine gene induction at defined time points following intranasal vaccination which confirmed its attenuation compared to WT Schu S4. Cytokine, chemokine, and antibody induction patterns compared to wild-type Schu S4 distinguish protective vs. pathogenic responses to F. tularensis and elucidate correlates of protection associated with vaccination against this agent.

中文翻译：

---

将Schu S4 aro突变体鉴定为减毒活的Tularemia候选疫苗。

需要开发一种针对图拉尼斯弗朗西斯菌的有效疫苗，因为这种潜在的生物武器通过气雾剂途径运送时具有很高的死亡率和较低的感染剂量。而且，该1级特工具有武器化的历史。我们在芳香族氨基酸生物合成中编码关键酶的aro基因中设计了A型菌株F. tularensis亚种tularensis Schu S4中的靶向突变。F. tularensis SchuS4ΔaroC，SchuS4ΔaroD和SchuS4ΔaroCΔaroD突变株的体外细胞内生长和体内毒力减弱，并赋予C57BL / 6小鼠肺部野生型（WT）F. tularensis Schu S4攻击保护性模型。F. tularensis SchuS4ΔaroD被确定为最有前途的疫苗候选物，显示出对高剂量鼻内攻击的保护；它可以抵御1,000 CFU Schu S4的冲击，这是迄今为止测试的最高防护等级。它还提供了针对92 CFU的F. tularensis亚种holarctica菌株（B型）的完全保护。小鼠对SchuS4ΔaroD的全身IgM和IgG2c疫苗接种产生了反应，并在脾细胞-巨噬细胞共培养试验中测定了功能性T细胞反应的产生。鼻内疫苗接种后的规定时间点，进一步鉴定了该疫苗的传播，组织病理学和细胞因子/趋化因子基因诱导特征，这证实了与WT Schu S4相比其减毒作用。与野生型Schu S4相比，细胞因子，趋化因子和抗体诱导方式可区分对F的保护性反应和致病性反应。