Research and Development Center, Ezequiel Dias Foundation (Funed), Belo Horizonte, MG, Brazil.
Can J Microbiol. 2012 Sep;58(9):1055-62. doi: 10.1139/w2012-083. Epub 2012 Aug 20.
Vaccination is the most promising strategy to reduce the incidence of pneumococcal infection. Although there are vaccines available, all of them are based on polysaccharide antigens (conjugated or not). In addition to their high cost, those vaccines do not cover all serotypes. To overcome these hindrances, we evaluated the immunogenicity and the protective efficacy of the S9 ribosomal protein of Streptococcus pneumoniae with the aim of developing a protein-based vaccine in the future. The gene encoding the S9 ribosomal protein was cloned in pET21-a expression vector, and the recombinant S9 protein was used to immunize mice. Significantly higher levels of anti-S9 immunoglobulin G were achieved (with predominance of immunoglobulin G1) in comparison with the control. Antibodies elicited against S. pneumoniae protein extract in rabbit recognized the recombinant S9 protein by Western blot, thus demonstrating its immunogenicity. Moreover, mice immunized with recombinant S9 protein and challenged with a virulent strain of S. pneumoniae presented a significant reduction of bacteremia after 24 h of infection as compared with the control. However, in the S9-immunized mice the onset of death was insignificantly delayed, but all of them died by the fourth day postinfection.
疫苗接种是降低肺炎球菌感染发生率最有希望的策略。虽然有疫苗可用，但它们都是基于多糖抗原（结合或不结合）。除了成本高之外，这些疫苗并不能覆盖所有血清型。为了克服这些障碍，我们评估了肺炎链球菌 S9 核糖体蛋白的免疫原性和保护效力，以期将来开发一种基于蛋白质的疫苗。编码 S9 核糖体蛋白的基因被克隆到 pET21-a 表达载体中，并用重组 S9 蛋白免疫小鼠。与对照组相比，小鼠产生的抗 S9 免疫球蛋白 G 水平显著升高（以 IgG1 为主）。兔抗肺炎球菌蛋白提取物产生的抗体通过 Western blot 识别重组 S9 蛋白，从而证明其具有免疫原性。此外，与对照组相比，用重组 S9 蛋白免疫并感染毒力株肺炎链球菌的小鼠在感染后 24 小时内菌血症显著减少。然而，在 S9 免疫的小鼠中，死亡的开始并没有明显延迟，但所有小鼠在感染后第四天都死亡。
