Specific IgG activity against diarrheagenic bacteria in bovine immune milk and effect of pH on its antigen-binding activity upon heating

摘要

Bovine colostrum and milk antibodies of calving and lactating cows immunized with a multivalent vaccine consisting of whole cells of three different species of pathogenic bacteria including four strains of enterotoxigenic Escherischia coli, five strains of enteropathogenic Esch. coli, three strains of enteroinvasive Esch. coli, two strains of Samonella typhi, and one strain each of Shigellia dysenteriae, Sh. sonnei and Sh. flexneri were generated, respectively. A significantly elevated activity and titre of specific IgG from bovine immune colostrum were seen for only 5 days after calving of immunized cows, however, the levels of specific IgG could be obtained continuously from the milk of immunized lactating cows until the 11th week of the entire experiment period. Subsequently, we observed that the high specific IgG activity in immune milk was relatively stable under pH 5.-0-7.0 at 37 ℃. Of importance, we identified that the specific IgG preserved its biological function for high antigen-binding activity at pH 5.5-6.5 for 30min of heat treatment at 70 ℃ and for 350 s at 72 ℃. Our findings suggest that the specific IgG from milk antibodies of immunized lactating cows may be used as an abundant source of hyper-immune products for prevention of multibacteria-induced diarrhea, however, the effect of pH on its antigen-binding activity upon heating should be carefully considered and designed.