CONSTRUCTION OF A HYBRID PLASMID CODING FOR ADHERENCE ANTIGEN K88AB AS WELL AS THE B-SUBUNIT OF ESCHERICHIA-COLI THERMO-LABILE ENTEROTOXIN AND MOUSE IMMUNE-RESPONSE TO THE ENCODED ANTIGENS

A hybrid plasmid (pUB 3744) encoding the adherence antigen K88ab and t he B subunit of Escherichia coli heat-labile enterotoxin (LT-B) was pr epared by linking plasmids pFM 205 (K88ab(+)) and pUB 1844 (LT-B+). Th e three plasmids were subsequently transferred to the porcine E, coli strain 045:K, producing variants K88ab(+), LT-B+ and K88ab(+)/LT-B+. T hese variants were orally given to distinct groups of mice on five con secutive days. The isotype-specific antibody response to K88ab, LT-B a nd to sonicated bacterial antigen was measured after a further five da ys in serum and scrapings of intestinal mucosa. Excretion of the inocu lated bacteria was monitored by culturing fecal samples. Strain LT-Bpersisted longer in the intestine and induced a local immune response to LT-B (IgA, IgG and IgM). No antibody to K88ab was found in mice ino culated with the strain producing only K88ab, but mice inoculated with strain K88ab(+)/LT-B+ showed an increase in intestinal antibody level s to K88ab. All mice inoculated with the 045:K- variants had an increa se in serum IgA levels to sonicated bacterial antigens, which were hig her in animals fed with variant K88ab(+)/LT-B+.