REGULATION OF VIRULENCE FACTORS IN BORDETELLA PERTUSSIS

我们实验室的工作一直与调节 百日咳博德特氏菌的毒力因子， 百日咳和百日咳疫苗的目标。 以前的研究 已经表明，一个遗传基因座，bvg基因座，是负责 调节B。百日咳毒力决定因子（百日咳 毒素， 丝状血凝素等;百日咳的主要成分 疫苗）对环境刺激的反应。 我们最近 开发了强大的新的物理和遗传方法，用于分析 细菌基因组 我们在过去一年中使用了这些工具， 分析百日咳毒素表达的调控， 百日咳疫苗中的保护性抗原。 虽然这种表达 基因由bvg基因座控制，这种调节不是直接的， 似乎还涉及其他因素。 我们进行了基因检测 寻找这些因素，但没有发现它们。 但 在BVG基因座中， 发现了 该类突变影响百日咳毒素的调节 而对丝状血凝素等其他毒力因子则不敏感。 我们已经检查了超过100个这些突变的回复突变体， 百日咳毒素表达。 其中一些回复突变映射回 然而，其它基因影响百日咳毒素基因本身。 在这些情况下，百日咳毒素的表达不再受控制， bvg基因座。 这些回复突变株具有几个特征 这使它们成为疫苗生产的潜在候选者： 1)在一些实施方案中，百日咳毒素基因的表达水平是 回复突变体，高于亲本菌株。 2)百日咳毒素 基因在bvg基因座关闭的条件下表达 其他毒力因子的表达，从而使得有可能 在其他有毒因素 不生产，从而可能提高疫苗的安全性以及安全性 在生产中。 3)百日咳毒素的表达， BVG轨迹的控制不受相位变化的影响， 在大规模发酵罐中是一个问题，并导致非常低的产率。

Work in our laboratory has been concerned with the regulation of virulence factors in Bordetella pertussis, the causative agent of whooping cough, and the target of pertussis vaccine. Previous studies have shown that a genetic locus, the bvg locus, is responsible for the regulation of B. pertussis virulence determinants (pertussis toxin, filamentous hemagglutinin, etc.; major components of the pertussis vaccine) in response to environmental stimuli. We have recently developed powerful new physical and genetic methods for the analysis of bacterial genomes. We have used these tools in the past year in the analysis of regulation of expression of pertussis toxin, the major protective antigen in pertussis vaccines. Although expression of this gene is governed by the bvg locus, this regulation is not direct and it appears that other factors may be involved. We have conducted a genetic search for such factors and have failed to identify them. However, a very interesting new class of mutations in the bvg locus has been discovered. Mutations in this class affect regulation of pertussis toxin but not some other virulence factors such as filamentous hemagglutinin. We have examined over 100 revertants of these mutations which restore pertussis toxin expression. Some of these reverting mutations map back to the bvg locus, however, others affect the pertussis toxin gene itself. In these cases, pertussis toxin expression is no longer under the control of the bvg locus. These revertant strains have several characteristics that make them potentially exciting candidates for vaccine production: 1) The level of expression of the pertussis toxin gene is, in some revertants, higher than in the parent strain. 2) The pertussis toxin gene is expressed under conditions where the bvg locus shuts off expression of the other virulence factors, thus making it possible to produce pertussis toxin under conditions where other toxic factors are not produced, thus potentially improving vaccine safety as well as safety in production. 3) Expression of pertussis toxin, being no longer under the control of the bvg locus, is not subject to phase-variation which can be a problem in large scale fermentors and result in a very low yields.