Egg yolk immunoglobulin (IgY) is the antibody in egg yolk and can be produced in egg yolk by immunizing hens with antigens. IgY is functionally equivalent to mammalian IgG. It is found in the serum of the chicken and is passed from the mother chicken to the embryo via the egg yolk, a process that results in a high concentration of IgY in the egg yolk. The objective of this study was to evaluate the efficacy of specific IgY against enterotoxigenic Escherichia coli (ETEC) K99, Salmonella Typhimurium and Salmonella Choleraesuis that cause porcine bacterial diseases. To prepare specific IgY, Hy-Line Brown chickens were vaccinated with killed vaccine complex including E. coli K99, S. Typhimurium and S. Choleraesuis. The chicken egg yolk antibodies were purified from egg yolk by ammonium sulfate precipitation and the quality of the final preparation was confirmed by sodium dodecyl sulfate polyacrylamide gel electro-phoresis (SDS-PAGE). Titres of specific IgY in final preparations were measured by an enzyme-linked immunosorbent assay (ELISA). Antibody titers peaked at 3 weeks regardless the bacterial types and the similar patterns of immune response were observed for respective pathogens. In growth inhibitor test, specific IgY showed inhibitory effect on bacterial growth. After 0, 3, 6 and 12 hour of incubation with specific IgY (100 ㎍/㎖, 250 ㎍/㎖, 500 ㎍/㎖), there was a significant decrease in the growth (A 600nm ) of E. coli K99, S. Typhimurium and S. Choleraesuis compared to nonspecific IgY and controls. In BALB/c mice, the effect of specific IgY (100 ㎎/㎏, 250 ㎎/㎏) on bacterial challenges was investigated by intramuscular injection and oral administration of bacteria. Mice treated with specific IgY showed high survival rate though there was no significant differences on blood biochemichal examinations between treated and untreated groups. These results indicate the potential of specific IgY for the treatment of porcine bacterial diseases caused by E. coli K99, S. Typhimurium and S. Choleraesuis.

The present study evaluated the potential use of immunoglobulin prepared from egg yolk of chickens immunized with Escherichia coli K88 (IgY-Ec) in the control of E. coli K88 infection in RAW 264.7 murine macrophage. The binding activity of IgY-Ec against E. coli K88 surface protein was more specific and increased than control IgY. In infection assay of E. coli in macrophage, the specific IgY-Ec to E. coli K88 remarkably inhibited the phagocytic activity comparing to nonspecific IgY (p<0.001). In adherence assay, bacterial adhesion on macrophage cells was definitely reduced by preincubation of IgY-Ec compared with nonspecific IgY (p<0.05). These findings suggested that IgY-Ec have the protective effects against pathogens and IgY-based diets may have potential benefits for preventing or treating various infections in domestic animals.