Inhibitory effects of antibodies against cell surface protein antigen PAc-glucosyltransferase fusion proteins derived from Streptococcus mutans on the induction of dental caries

变形链球菌产生的细胞表面蛋白抗原(PAC)和葡萄糖转移酶(GTF)被认为是该菌的主要定植因子，本研究构建了PACA-GB融合蛋白和PACA-SB融合蛋白，PACA-GB融合蛋白是PAC的唾液结合丙氨酸富集区(PACA)与GTF-I的葡聚糖结合(GB)结构域的融合蛋白，PACA-SB是PACA与GTE-I的蔗糖结合(SB)结构域的融合蛋白。纯化重组融合蛋白，制备兔抗融合蛋白抗体。抗PACA-GB抗体可明显抑制变形链球菌细胞结合和无细胞GTF合成水不溶性葡聚糖，而抗PACA-SB抗体对GTF-I合成总葡聚糖无明显抑制作用。当在反应混合物中加入抗PACA-GB抗体时，变形链球菌对唾液包被的羟基磷灰石微珠的蔗糖非依赖性和蔗糖依赖性的黏附被显著抑制。抗PACA-SB抗体在无蔗糖时抑制变形链球菌对珠子的黏附，但在蔗糖存在时不能抑制变形链球菌与珠子的黏附。用融合蛋白PACA-GB免疫可能有助于控制变形链球菌对牙齿的定植。

Cell surface protein antigen (PAc) and glucosyltransferases (GTFs) produced by Streptococcus mutans are considered to be major colonization factors of the organism.In this study, fusion protein PAcA-GB, a fusion of the saliva-binding alanine-rich region (PAcA) of PAc with the glucan binding (GB) domain of GTF-I, an enzyme catalyzing the synthesis of water-insoluble glucan from sucrose, and fusion protein PAcA-SB, a fusion of PAcA with the sucrose binding (SB) domain of GTE-I were constructed. The recombinant fusion proteins were purified, and rabbit antibodies against these fusion proteins were prepared. Water-insoluble glucan synthesis by cell-associated and cell- free GTF preparations from S.mutans as well as total glucan synthesis by GTF-I was markedly inhibited by anti-PAcA-GB antibodies but not by anti- PAcA-SB antibodies. Significant inhibition of the sucrose-independent and sucrose-dependent adhesion of S.mutans to saliva-coated hydroxyapatite beads was observed when anti-PAcA-GB antibodies were added to the reaction mixture. Anti-PAcA-SB antibodies inhibited the adhesion of S.mutans to the beads in the absence of sucrose but not in the presence of sucrose. immunization with the fusion protein PAcA-GB may be useful for controlling the colonization of teeth by S.mutans.