The Biodesign Institute, Center for Infectious Diseases and Vaccinology, Arizona State University, P.O. Box 875401, 1001 S. McAllister Avenue, Tempe, AZ 85287-5401, USA.
Infect Immun. 2011 Feb;79(2):937-49. doi: 10.1128/IAI.00445-10. Epub 2010 Dec 6.
Induction of strong immune responses against a vectored antigen in hosts immunized with live attenuated Salmonella vaccines is related in part to the amount of antigen delivered and the overall fitness of the Salmonella vector in relation to its ability to stimulate the host immune system. Constitutive high-level antigen synthesis causes a metabolic burden to the vaccine vector strain that can reduce the vaccine strain's ability to interact with host lymphoid tissues, resulting in a compromised immune response. A solution to this problem is the use of systems that regulate antigen gene expression, permitting high levels of antigen synthesis only after the vaccine strain has reached its target tissues. In vivo-inducible promoters (IVIPs) are often used to accomplish this. We recently developed an alternative strategy, a regulated delayed antigen synthesis (RDAS) system, in which the LacI-repressible P(trc) promoter controls antigen gene expression by adding arabinose. In this paper, we compared the RDAS system with two commonly used IVIPs, P(ssaG) and P(pagC). Three nearly identical plasmids, differing only in the promoter used to direct transcription of the pneumococcal pspA gene, P(trc), P(ssaG), or P(pagC), were constructed and introduced into isogenic Salmonella vaccine strains with or without arabinose-inducible LacI synthesis. Mice immunized with the RDAS strain developed slightly higher titers of mucosal and serum anti-PspA antibodies than P(pagC)-immunized mice, while titers in mice immunized with the P(ssaG) strain were 100-fold lower. Both the RDAS and P(pagC) strains conferred similar levels of protection against Streptococcus pneumoniae challenge, significantly greater than those for the P(ssaG) strain or controls. Thus, RDAS provides another choice for inclusion in the live vaccine design to increase immunogenicity.
在接种减毒活沙门氏菌疫苗的宿主中，针对载体抗原产生强烈免疫应答的部分原因与抗原递呈量以及沙门氏菌载体与刺激宿主免疫系统的整体适应性有关。组成型高水平抗原合成会给疫苗载体菌株带来代谢负担，从而降低疫苗菌株与宿主淋巴组织相互作用的能力，导致免疫应答受损。解决此问题的方法是使用可调节抗原基因表达的系统，仅在疫苗菌株到达目标组织后才允许高水平的抗原合成。体内诱导型启动子（IVIP）通常用于实现此目的。我们最近开发了一种替代策略，即调节延迟抗原合成（RDAS）系统，其中 LacI 可抑制的 P(trc)启动子通过添加阿拉伯糖来控制抗原基因的表达。在本文中，我们比较了 RDAS 系统与两种常用的 IVIP，P(ssaG)和 P(pagC)。构建了三个几乎相同的质粒，仅在指导肺炎球菌 pspA 基因转录的启动子上有所不同，分别为 P(trc)、P(ssaG)或 P(pagC)，并将其引入带有或不带有阿拉伯糖诱导型 LacI 合成的同源沙门氏菌疫苗菌株中。用 RDAS 菌株免疫的小鼠比用 P(pagC)免疫的小鼠产生了稍高滴度的黏膜和血清抗 PspA 抗体，而用 P(ssaG)菌株免疫的小鼠滴度则低 100 倍。RDAS 和 P(pagC)菌株均能提供针对肺炎链球菌攻击的相似水平的保护，显著优于 P(ssaG)菌株或对照。因此，RDAS 为增加免疫原性提供了另一种选择，可纳入活疫苗设计中。
