Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
PLoS One. 2012;7(2):e31172. doi: 10.1371/journal.pone.0031172. Epub 2012 Feb 15.
Vaccination is a proven strategy to mitigate morbidity and mortality of infectious diseases. The methodology of identifying and testing new vaccine candidates could be improved with rational design and in vitro testing prior to animal experimentation. The tularemia vaccine, Francisella tularensis live vaccine strain (LVS), does not elicit complete protection against lethal challenge with a virulent type A Francisella strain. One factor that may contribute to this poor performance is limited stimulation of antigen-presenting cells. In this study, we examined whether the interaction of genetically modified LVS strains with human antigen-presenting cells correlated with effectiveness as tularemia vaccine candidates. Human dendritic cells infected with wild-type LVS secrete low levels of proinflammatory cytokines, fail to upregulate costimulatory molecules, and activate human T cells poorly in vitro. One LVS mutant, strain 13B47, stimulated higher levels of proinflammatory cytokines from dendritic cells and macrophages and increased costimulatory molecule expression on dendritic cells compared to wild type. Additionally, 13B47-infected dendritic cells activated T cells more efficiently than LVS-infected cells. A deletion allele of the same gene in LVS displayed similar in vitro characteristics, but vaccination with this strain did not improve survival after challenge with a virulent Francisella strain. In vivo, this mutant was attenuated for growth and did not stimulate T cell responses in the lung comparable to wild type. Therefore, stimulation of antigen-presenting cells in vitro was improved by genetic modification of LVS, but did not correlate with efficacy against challenge in vivo within this model system.
疫苗接种是减轻传染病发病率和死亡率的一种经过验证的策略。在进行动物实验之前，可以通过合理设计和体外测试来改进鉴定和测试新疫苗候选物的方法。土拉热疫苗，即弗氏耶尔森菌活疫苗株（LVS），不能完全抵御强毒 A 型弗氏耶尔森菌的致死性攻击。导致这种保护效果不佳的一个因素可能是抗原呈递细胞的刺激有限。在这项研究中，我们研究了基因改造的 LVS 菌株与人类抗原呈递细胞的相互作用是否与作为土拉热疫苗候选物的有效性相关。感染野生型 LVS 的人树突状细胞分泌低水平的促炎细胞因子，不能上调共刺激分子，并且在体外激活人 T 细胞的能力也较差。LVS 的一种突变株，菌株 13B47，可刺激树突状细胞和巨噬细胞中更高水平的促炎细胞因子，并增加树突状细胞上的共刺激分子表达，与野生型相比。此外，13B47 感染的树突状细胞比 LVS 感染的细胞更有效地激活 T 细胞。LVS 中同一基因的缺失等位基因具有类似的体外特征，但用该菌株接种并不能提高对强毒弗朗西斯菌菌株攻击的存活率。在体内，这种突变株的生长受到抑制，并且不能刺激与野生型相当的肺部 T 细胞反应。因此，LVS 的基因改造可改善抗原呈递细胞的体外刺激，但与该模型系统中体内攻毒的功效不相关。
