Erickson A K, Billey L O, Srinivas G, Baker D R, Francis D H
Department of Veterinary Science, South Dakota State University, Brookings 57007, USA.
Adv Exp Med Biol. 1997;412:167-73. doi: 10.1007/978-1-4899-1828-4_25.
Four phenotypes of pigs distinguished by the variant(s) of K88 fimbrial adhesin (K88ab, K88ac, K88ad) that bind to their intestinal epithelial cells (I-none of the variants, II-K88ad, III-K88ab and K88ac, and IV-all three variants) have been identified. We hypothesize that the differences between the phenotypes are defined by the presence or absence of K88 adhesin receptors. We propose a three-receptor model to account for the observed phenotypes: 1) Receptor bed which binds all three variants and is found in phenotype IV, 2) Receptor be which binds K88ab and K88ac and is found in phenotype III and IV, and 3) Receptor d which binds K88ad and is found in phenotype II. We have identified the be receptor activity as a pair of mucin-type sialoglycoproteins (210 and 240 kDa). Although neither the bcd nor d receptor has been identified biochemically, their presence has been established using both blocking and receptor localization studies. Blocking studies using phenotype IV brush borders demonstrated that K88ab and K88ac fimbriae block the binding of E. coli expressing any of the K88 variants, but K88ad fimbriae block only K88ad E. coli binding. These results indicate that two receptors (bcd and bc) exist in the phenotype IV animals. Receptor localization studies on intestinal sections from phenotype IV animals showed that K88ab and K88ac adhesin binding is continuous from the crypt to the tip of the villus. The binding of the K88ad adhesin binding is multifocal in phenotype IV pigs, but continuous from crypt to tip of the villus in sections of phenotype II pigs. These studies verify the presence of two receptors (bcd and bc) in phenotype IV animals, and indicate that the K88ad receptor in phenotype IV animals (bcd) is different than in phenotype II animals (d).
根据能与肠道上皮细胞结合的K88菌毛粘附素变体（K88ab、K88ac、K88ad），已鉴定出猪的四种表型（I - 无变体，II - K88ad，III - K88ab和K88ac，IV - 所有三种变体）。我们假设表型之间的差异由K88粘附素受体的存在与否决定。我们提出了一个三受体模型来解释观察到的表型：1）能结合所有三种变体的受体床，存在于表型IV中；2）能结合K88ab和K88ac的受体be，存在于表型III和IV中；3）能结合K88ad的受体d，存在于表型II中。我们已将be受体活性鉴定为一对粘蛋白型唾液酸糖蛋白（210和240 kDa）。尽管bcd和d受体尚未通过生化方法鉴定，但已通过阻断和受体定位研究确定了它们的存在。使用表型IV刷状缘进行的阻断研究表明，K88ab和K88ac菌毛可阻断表达任何K88变体的大肠杆菌的结合，但K88ad菌毛仅阻断K88ad大肠杆菌的结合。这些结果表明表型IV动物中存在两种受体（bcd和bc）。对表型IV动物肠道切片的受体定位研究表明，K88ab和K88ac粘附素的结合从隐窝到绒毛尖端是连续的。K88ad粘附素的结合在表型IV猪中是多灶性的，但在表型II猪的切片中从隐窝到绒毛尖端是连续的。这些研究证实了表型IV动物中存在两种受体（bcd和bc），并表明表型IV动物中的K88ad受体（bcd）与表型II动物中的（d）不同。
