Shigellae

病原菌的表面多糖，包括荚膜多糖（CPS）或脂多糖（LPS）的o特异性多糖（O-SP），既是必需的毒力因子，也是保护性抗原。这些糖与医学上有用的蛋白质共价结合形成偶联物，既增加了它们的免疫原性，又赋予它们t细胞依赖性，使它们成为婴儿和儿童的合适疫苗。sonnei志贺氏菌O-SP与重组无毒铜绿假单胞菌外蛋白A （rEPA）结合，在6-14%的发病率暴露的年轻人中，有效率超过70%。该结合物与S. flexneri 2a结合琥珀酰化外蛋白A （repa -suc）是安全的，可诱导1-4岁儿童产生针对同源LPS的IgG抗体。在1-4岁儿童中进行的一项随机、盲法、3期研究表明，这些疫苗是安全的，每种结合物作为另一种结合物的对照。免疫原性和疗效与年龄相关，1 ~ 2岁疗效甚微，3 ~ 4岁约70%。和以前一样，抗体水平增加了几倍，与成年人相似，但实际达到的水平要低一些。

Surface polysaccharides of pathogenic bacteria, including capsular polysaccharides (CPS) or the O-specific polysaccharide (O-SP) of lipopolysaccharides (LPS), serve both as essential virulence factors and as protective antigens. Covalent binding of these saccharides to medically-useful proteins to form conjugates both increases their immunogenicity and confers to them T-cell dependence making them suitable vaccines for infants and children. The O-SP of Shigella sonnei bound to recombinant non toxic P. aeruginosa exoprotein A (rEPA) had an efficacy of over 70% in young adults exposed to 6-14% attack rates. This conjugate and of S. flexneri 2a bound to the succinylated exoprotein A (rEPA-succ) were safe and induced IgG antibodies to the homologous LPS in 1-4 year-olds. A randomized, blinded, phase 3 study of these conjugates in 1-4 year-olds with each conjugate serving as a control for the other showed these vaccines to be safe. Immunogenicity and efficacy were age related with little efficacy in 1-2 years old, about 70% in 3-4 years old. Fold increases in antibody levels were, as before, similar to those of adults but the actual levels achieved were lower. The effect of these children's immune sera and IgG isolated from them upon Shigella invasion into epithelial intestinal cells was studied in vitro using Caco-2 and HeLa cells. The sera inhibited Shigella invasion in a type specific manner. Pretreatment of the sera or of Caco-2 cells with O-SP abrogated these effects in a type specific and dose dependent manner. To enhance the immunogenicity of these conjugates S. sonnei and S. flexneri 2a O-SPs were bound to additional carrier proteins: tetanus toxoid (TT) and recombinant protective antigen (rPA). Mice were injected twice, with the same or a different carrier the second time. For S. flexneri 2a the TT conjugate injected twice induced the highest (>4-fold) antibody levels. For S. sonnei, the TT conjugate followed by the rPA conjugate induced significantly higher levels than the other combinations. We have shown that synthetic oligosaccharides of S. dysenteriae type 1 O-SP bound by their reducing end to a carrier protein (sun configuration) induced significantly higher antibody levels than conjugates of the native O-SP bound to protein by multiple point attachments (lattice configuration). Synthesis of S. sonnei oligosaccharides was not successful. Therefore, the low molecular mass O-SP-core (O-SPC) fragments of the native O-SP were isolated and used to bind to proteins by oxime linkages between the terminal Kdo residues of the reducing end core and aminoxy linkers bound to BSA or to a non toxic diphtheria toxin mutant. The coupling reaction was done at a neutral pH, room temperature and in a short time. IgG anti S. sonnei LPS levels induced by these conjugates in young outbred mice were significantly higher than those induced by the full length O-SP conjugates. The O-SP of Plesiomonas shigelloides O17 is structurally identical to that of S. sonnei but the core structure of S. sonnei only is published. We investigated the core structure of P. shigelloides O17, including its linkage to the O-SP by NMR and mass spectroscopy. The structure was assigned.