EXPRESSION OF MUCIN-TYPE GLYCOPROTEIN K88 RECEPTORS STRONGLY CORRELATES WITH PIGLET SUSCEPTIBILITY TO K88(-COLI, BUT ADHESION OF THIS BACTERIUM TO BRUSH-BORDERS DOES NOT() ENTEROTOXIGENIC ESCHERICHIA)

Three antigenic variants of the K88 fimbrial adhesin exist in nature, K88ab, K88ac, and K88ad, Enterotoxigenic Escherichia coli (ETEC) strai ns that produce these fimbriae cause life-threatening diarrhea in some brat not all young pigs, The susceptibility of pigs to these organism s has been correlated with the adherence of bacteria to isolated enter ocyte brush borders. Whether that correlation holds for multiple K88 v ariants and over a broad genetic base of pigs is unknown and was the i mpetus for this study. We also desired to examine the correlation of t he expression of a porcine intestinal brush border mucin-type glycopro tein (IMTGP) which binds K88ab and K88ac with the susceptibility of pi glets to K88(+) ETEC. Of 31 neonatal gnotobiotic pigs inoculated with K88ab(+) or K88ac(+) ETEC, 13 developed severe diarrhea, became dehydr ated, and died or became mori-bund. Another pig became severely lethar gic but not dehydrated, In vitro brush border adherence analysis was m ot possible for 10 of the severely ill pigs due to colonization by cha llenge strains. However, of the 17 pigs that did not become severely i ll, 8 (47%) had brush borders that supported the adherence of K88ab(+) and K88ac(+) bacteria in vitro, suggesting a poor correlation between in vitro brush border adherence and piglet susceptibility to K88(+) E TEC. By contrast, the expression of IMTGP was highly correlated with s usceptibility to K88+ ETEC, Of the 12 pigs that produced IMTGP, 11 dev eloped severe diarrhea. The other pig that produced IMTGP became letha rgic but not severely diarrheic. Only 2 of 18 pigs that did not produc e IMTGP became severely diarrheic, Colonizing bacteria were observed i ts histologic sections of intestines from all pigs that expressed IMTG P except for the one that did not develop severe diarrhea, However, co lonizing bacteria were observed in histologic sections from only one p ig that did not produce IMTGP. The bacterial concentration in the jeju na and ilea of pigs expressing IMTGP was significantly greater (P < 0. 005) than that in pigs not expressing IMTGP. These observations sugges t the IR IMTGP is a biologically relevant receptor for K88ab(+) and K8 8ac(+) E. coli or a correlate for expression for such a receptor.