Guttormsen Hilde-Kari, Baker Carol J, Nahm Moon H, Paoletti Lawrence C, Zughaier Susu M, Edwards Morven S, Kasper Dennis L
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Infect Immun. 2002 Apr;70(4):1724-38. doi: 10.1128/IAI.70.4.1724-1738.2002.
Covalent linkage of a bacterial polysaccharide to a protein greatly enhances the carbohydrate's immunogenicity and its binding to solid surfaces in immunoassays. These findings have spurred the development of glycoconjugate vaccines to prevent serious bacterial infections as well as the use of glycoconjugates as coating antigens in bioassays. We evaluated sera from women immunized with unconjugated group B streptococcal (GBS) type III (GBS III) polysaccharide (IIIPS) or with IIIPS covalently linked to tetanus toxoid to assess specificity, sensitivity, and parallelism in dilution curves in two GBS III enzyme-linked immunosorbent assays (ELISAs). One assay used IIIPS mixed with methylated human serum albumin (IIIPS + mHSA) as the coating antigen, and the other used IIIPS covalently linked to HSA (III-HSA). Each coating antigen was associated with a highly specific GBS III bioassay. The sensitivity was higher in the III-HSA ELISA, in which conjugated IIIPS is bound to the plates. Parallelism in titration curves was observed in the III-HSA but not in the IIIPS + mHSA ELISA. The excellent correlation between the concentrations of GBS IIIPS-specific immunoglobulin G (IgG) and the opsonophagocytic activity of these antibodies indicated that the III-HSA assay can predict functionality of vaccine-induced IgG against GBS III disease. The structure of the repeating unit of the capsular polysaccharide of GBS III differs from that of Streptococcus pneumoniae type 14 (Pn14 PS) only by the presence on GBS III of a sialic acid residue at the end of the side chain. The majority of healthy adults responding to GBS III vaccines with a fourfold or greater increase in GBS III-specific IgG antibodies developed antibodies cross-reacting with Pn14 PS (i.e., desialylated GBS IIIPS). The proportion of GBS vaccine responders who developed IgG to the desialylated IIIPS did not depend on whether IIIPS was given in the unconjugated or conjugated form. When present, these vaccine-induced cross-reacting antibodies conferred in vitro antibody-mediated opsonophagocytosis and killing of both GBS III and Pn14, two pathogens that cause invasive disease in young infants.
将细菌多糖与蛋白质共价连接可极大地增强碳水化合物的免疫原性及其在免疫测定中与固体表面的结合能力。这些发现推动了糖缀合物疫苗的开发，以预防严重的细菌感染，同时也促进了糖缀合物在生物测定中作为包被抗原的应用。我们评估了用未结合的B族链球菌（GBS）Ⅲ型（GBS III）多糖（IIIPS）或与破伤风类毒素共价连接的IIIPS免疫的女性血清，以评估两种GBS III酶联免疫吸附测定（ELISA）中稀释曲线的特异性、敏感性和平行性。一种测定使用与甲基化人血清白蛋白混合的IIIPS（IIIPS + mHSA）作为包被抗原，另一种使用与HSA共价连接的IIIPS（III-HSA）。每种包被抗原都与一种高度特异性的GBS III生物测定相关。在III-HSA ELISA中敏感性更高，其中结合的IIIPS与板结合。在III-HSA中观察到滴定曲线的平行性，但在IIIPS + mHSA ELISA中未观察到。GBS IIIPS特异性免疫球蛋白G（IgG）浓度与这些抗体的调理吞噬活性之间的良好相关性表明，III-HSA测定可以预测疫苗诱导的IgG针对GBS III疾病的功能。GBS III荚膜多糖重复单元的结构与14型肺炎链球菌（Pn14 PS）的结构仅在GBS III侧链末端存在唾液酸残基方面有所不同。大多数对GBS III疫苗有反应且GBS III特异性IgG抗体增加四倍或更多的健康成年人产生了与Pn14 PS（即去唾液酸化GBS IIIPS）交叉反应的抗体。产生去唾液酸化IIIPS IgG的GBS疫苗应答者比例不取决于IIIPS是以未结合形式还是结合形式给予。当存在时，这些疫苗诱导的交叉反应抗体在体外赋予抗体介导的调理吞噬作用，并能杀死GBS III和Pn14这两种在幼儿中引起侵袭性疾病的病原体。
