EFFECT OF DEFINED POINT MUTATIONS IN THE PNEUMOLYSIN GENE ON THE VIRULENCE OF STREPTOCOCCUS-PNEUMONIAE
EFFECT OF DEFINED POINT MUTATIONS IN THE PNEUMOLYSIN GENE ON THE VIRULENCE OF STREPTOCOCCUS-PNEUMONIAE
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DOI：
10.1128/iai.63.5.1969-1974.1995
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发表时间：
1995-05-01
影响因子：
3.1
通讯作者：
PATON, JC
中科院分区：
文献类型：
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作者：
BERRY, AM;ALEXANDER, JE;PATON, JC
硫醇激活毒素肺炎球菌溶血素是一种已知的肺炎球菌毒力因子，具有细胞毒性（溶血性）和补体激活特性，通过插入重复诱变将携带影响其中一种或两种特性的确定点突变的肺炎球菌溶血素基因的副本引入肺炎链球菌 D39 的染色体中，然后比较这些其他同基因菌株的毒力，两者均无显着差异受到产生野生型毒素的 D39 衍生物攻击的小鼠与表达具有 Asp-385->Asn 突变（消除补体激活特性）的肺炎球菌溶血素基因的小鼠之间的中位生存时间或总生存率。然而，用携带 His-367-->Arg 或 Trp-433-->Phe 加 Cys-428-->Gly 突变（其溶血活性分别降低至野生型水平的约 0.02 和 0.0001%）的菌株攻击的小鼠，与用表达野生型肺炎球菌溶血素基因的 D39 衍生物攻击的小鼠相比，具有显着更长的中位生存时间和总生存率，但没有进一步降低当用带有肺炎球菌溶血素基因突变的 Trp-433-->Phe、Cys-428-->Gly 和 Asp-385-->Asn，而不是 Trp-433-->Phe 和 Cys-428-->Gly 的 D39 衍生物攻击小鼠时，观察到毒力。因此，看来在腹膜内攻击模型中，肺炎球菌溶血素对毒力很大程度上归因于其溶血（细胞毒性）特性，而不是其激活补体的能力。然而有趣的是，完全毒力所需的肺炎球菌溶血素的量可能非常小，因为携带 Trp-433-->Phe 突变（将溶血活性降低至野生型水平的 0.1%）的 D39 衍生物具有中等毒力。
The thiol-activated toxin pneumolysin is a known pneumococcal virulence factor, with both cytotoxic (hemolytic) and complement activation properties, Copies of the pneumolysin gene carrying defined point mutations affecting either or both of these properties were introduced into the chromosome of Streptococcus pneumoniae D39 by insertion-duplication mutagenesis, The virulences of these otherwise isogenic strains were then compared, There was no significant difference in either the median survival time or overall survival rate between mice challenged with D39 derivatives producing the wild-type toxin and those expressing a pneumolysin gene with an Asp-385-->Asn mutation, which abolishes the complement activation property. However, mice challenged with strains carrying either His-367-->Arg or Trp-433-->Phe plus Cys-428-->Gly mutations, which reduce hemolytic activity to approximately 0.02 and 0.0001% of the wild-type level, respectively, had significantly greater median survival times and overall survival rates than mice challenged with D39 derivatives expressing a Wild-type pneumolysin gene, No additional reduction in virulence was observed when mice were challenged with a D39 derivative carrying Trp-433-->Phe, Cys-428-->Gly, and Asp-385-->Asn, rather than Trp-433-->Phe and Cys-428-->Gly, mutations in the pneumolysin gene, Thus, it appears that in the intraperitoneal challenge model, the contribution of pneumolysin to virulence is largely attributable to its hemolytic (cytotoxic) properties rather than to its capacity to activate complement. Interestingly, however, the amount of pneumolysin required for full virulence may be very small, as D39 derivatives carrying the Trp-433-->Phe mutation (which reduces hemolytic activity to 0.1% of the wild-type level) had intermediate virulence.