Takabatake Noriyuki, Okamura Masashi, Yokoyama Naoaki, Okubo Kazuhiro, Ikehara Yuzuru, Igarashi Ikuo
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan.
J Vet Med Sci. 2007 Oct;69(10):999-1004. doi: 10.1292/jvms.69.999.
Host sialic acid (SA) has recently been suggested to play an important role in erythrocyte (RBC) infection by Babesia spp. The present study attempted to further determine the specific type of SAs important in the RBC invasion. Bovine RBC was found to bear abundant alpha2-3-linked SA residues but not alpha2-6-linked SA in nature, confirmed by flow cytometric analysis of the neuraminidase (Nm)-treated RBCs. Lectin-blot analyses revealed the removal of alpha2-3-linked SAs from the 97-, 33-, and 31-kDa bands by the Nm treatment. Addition of the Nm-treated RBCs into an in vitro culture of B. bovis resulted in a decreased population of the parasitized RBCs. The thin smear samples from the cultures were then observed under a confocal laser scanning microscope after staining with the alpha2-3-linked SA-specific lectin: a selective invasion of B. bovis was found only in the intact RBCs bearing the SAs, but not in the desialylated RBCs. Furthermore, a significant reduction of the parasitized RBCs was also observed in the culture supplemented with exogenous 3'-sialyllactose containing the alpha2-3-linked SAs. However, the complete inhibition of parasite proliferation was not achieved in the culture. These findings indicate that while the alpha2-3-linked SA-dependent pathway is needed for highly efficient invasion of host RBCs by B. bovis, there might also be other potential alternative pathways.
最近有研究表明，宿主唾液酸（SA）在巴贝斯虫属对红细胞（RBC）的感染中起重要作用。本研究试图进一步确定在红细胞入侵过程中起重要作用的SA的具体类型。通过对经神经氨酸酶（Nm）处理的红细胞进行流式细胞术分析证实，牛红细胞在自然状态下含有丰富的α2-3连接的SA残基，但不含有α2-6连接的SA。凝集素印迹分析显示，经Nm处理后，97 kDa、33 kDa和31 kDa条带中的α2-3连接的SA被去除。将经Nm处理的红细胞添加到牛巴贝斯虫的体外培养物中，导致被寄生红细胞群体减少。在用α2-3连接的SA特异性凝集素染色后，在共聚焦激光扫描显微镜下观察培养物的薄涂片样本：仅在含有SA的完整红细胞中发现牛巴贝斯虫有选择性入侵，而在去唾液酸化的红细胞中未发现。此外，在添加了含有α2-3连接的SA的外源性3'-唾液乳糖的培养物中，也观察到被寄生红细胞显著减少。然而，在培养物中并未完全抑制寄生虫增殖。这些发现表明，虽然α2-3连接的SA依赖性途径是牛巴贝斯虫高效入侵宿主红细胞所必需的，但可能还存在其他潜在的替代途径。
