Studies On Subunit Vaccine Of Swine Escherichia Coli

The heat-labile enterotoxin and pili of pathogenic swine Escherichia coli in Beijing,which were obtained and purified, were used to prepare fimbriae vaccines. The immunity of the vaccine was tested in laboratory and field.The k99 pili of Escherichia coli was obtained through shaker cultures on improved minca culture and purified by a modified procedure. After thenno-separating from the bacterial cells, the pili were concentrated by precipitation with ammonium sulfate, dialyzed. and solubilized in buffer containing deoxycholate. the pili was purified further by Sephadex G-100 column chromatography and identified by MRHA. Some rabbits were vaccinated with the fimbriae vaccines 3 times every 14 days, the titre of the antibodies to the pili was 1:16.The heat-labile enterotoxin of porcine E.coli isolates were assayed by ligation of rabbit ileum (LR1), plate immune heimolysis assay (P1HA) and blue spot in rabbit skin (BSRS). the positive resuh rate by PIHA and LRI was more higher than by BSRS. The heat-labile enterotoxin-producted E. coli was cultivated in cultivation box, the bacteria was harvested by centrifuged. supernatant was taken by the bacteria solution centrifuged, the heat-labile enterotoxin was concentrated by precipitation with ammonium sulfate, dialyzed, and solubilized in buffer containing deoxycholate. The heat-labile enterotoxin was purified futher by Sephadex G-100 column chromatography and identified by PIHA. After dialyzed against water, the sediment was analyzed by SDS-PAGE and the molecular weight of the protein were 12.5KD and 25KD.The k99 pili and the heat-labile enterotoxin,which were inactived and emulsified with mineral oil. were used to prepare subunit vaccines. The mouse vaccinated twice.then challenged with kgg E.coli isolate. The results was that the mouse can efficiently resist attack of homologous E.coli.The subunit vaccine was bacteria free and safe, the vaccine can be conserved at 4℃ for 1 year.The immunity test in field was randomly processed at 2 hogpen, the first group ,which consist of sow,were vaccinated with the subunit vaccine twice on 5 weeks and 2 weeks before giving birth, the second group,which consist of sow and piglets, were vaccinated on 2 weeks before giving birth and 10 days-old piglets, the third group, which consist of sow and piglets, was not vaccinated. The experiment showed that the vaccine was safe and protective.