Robert A, Jouin H, Fournier J M
Infect Immun. 1986 Nov;54(2):365-70. doi: 10.1128/iai.54.2.365-370.1986.
The immunoprotective activity of Klebsiella pneumoniae K2 cell surface preparations and purified capsular polysaccharide was tested in mice. The 50% protective dose (PD50), expressed as capsular polysaccharide content, was 2 ng for cell surface preparations and 50 ng for purified capsular polysaccharide. Both preparations lost their immunoprotective activity after alkali treatment. Immune sera were raised in rabbits immunized with cell surface preparations. The precipitating and hemagglutinating capacity of these antisera was tested against either purified capsular polysaccharide or alkali-treated capsular polysaccharide. No difference was observed between the reactivity of the antisera against each antigen. The protective activity of these sera was tested on mice in passive transfer experiments, before and after absorption with either purified capsular polysaccharide or alkali-treated capsular polysaccharide. The sera lost their protective activity after absorption with purified capsular polysaccharide and after absorption with alkali-treated capsular polysaccharide. These experiments show that the difference in immunoprotective activity of cell surface preparations, purified capsular polysaccharide, and alkali-treated capsular polysaccharide is not due to a difference in their antigenic determinants. Cell surface preparations and purified capsular polysaccharide were fractionated by gel filtration on Sepharose 4B and by ultracentrifugation on cesium chloride density gradients. Three forms of capsular polysaccharide have been characterized. (i) A form of capsular polysaccharide with a very high protective activity (PD50 = 2 ng) that copurified with protein and lipopolysaccharide and was characterized by a low coefficient of distribution (Kd = 0.20) and a low density (1.5 to 1.6 g/cm3). (ii) A form of capsular polysaccharide with an intermediate protective activity (PD50 = 50 ng), contamined by less than 3% protein and 1% lipopolysaccharide, with a Kd of 0.35, and a density of 1.7 to 1.8 g/cm3. (iii) A nonimmunoprotective capsular polysaccharide obtained after alkali treatment of either cell surface preparations or purified capsular polysaccharide. The Kd of these fractions varied from 0.20 to 0.90 and their density from 1.7 to 1.8 g/cm3.
在小鼠中测试了肺炎克雷伯菌K2细胞表面制剂和纯化荚膜多糖的免疫保护活性。以荚膜多糖含量表示的50%保护剂量（PD50），细胞表面制剂为2 ng，纯化荚膜多糖为50 ng。两种制剂经碱处理后均失去免疫保护活性。用细胞表面制剂免疫兔制备免疫血清。测试这些抗血清对纯化荚膜多糖或碱处理荚膜多糖的沉淀和血凝能力。未观察到抗血清对每种抗原反应性的差异。在被动转移实验中，在用纯化荚膜多糖或碱处理荚膜多糖吸收之前和之后，在小鼠身上测试这些血清的保护活性。血清在用纯化荚膜多糖吸收后以及用碱处理荚膜多糖吸收后均失去保护活性。这些实验表明，细胞表面制剂、纯化荚膜多糖和碱处理荚膜多糖免疫保护活性的差异不是由于它们抗原决定簇的差异。通过Sepharose 4B凝胶过滤和氯化铯密度梯度超速离心对细胞表面制剂和纯化荚膜多糖进行分级分离。已鉴定出三种形式的荚膜多糖。（i）一种具有非常高保护活性（PD50 = 2 ng）的荚膜多糖形式，与蛋白质和脂多糖共纯化，其特征在于分布系数低（Kd = 0.20）和密度低（1.5至1.6 g/cm3）。（ii）一种具有中等保护活性（PD50 = 50 ng）的荚膜多糖形式，蛋白质污染少于3%，脂多糖污染少于1%，Kd为0.35，密度为1.7至1.8 g/cm3。（iii）细胞表面制剂或纯化荚膜多糖经碱处理后获得的无免疫保护作用的荚膜多糖。这些级分的Kd在0.20至0.90之间变化，密度在1.7至1.8 g/cm3之间。
