Preparation And Activity Research Of Egg Yolk Antibody (IgY) Specific For Dairy Cow Mastitis

Egg yolk immunoglobulin, also called IgY, is one of three principal classes immunoglobulins in avian sera. IgY can bind to specific antigens such as bacteria, viruses, carcinogens and toxins and can neutralize the harmful effects of the antigens. It is known that the major serum antibody in chickens (IgG) is transferred across the follicular epithelium of the ovary and accumulated in the yolk during oogenesis in a manner similar to the placental transfer of IgG in mammals.Dairy cow mastitis is one of the principal causes of economic losses in the dairy industry. In particular, Staphylococcus aureus and Escherichia coli are the two most common pathogenic microorganisms. Generation of antibodies against pathogenic bacteria may represent an ideal alternative to the subtherapeutic use of antibiotics. The use of chickens for specific immunoglobulin production is more convenient. Because the antibodies are easily delivered in an egg and consequently no invasive techniques are necessary to harvest them.The objective of the present study was to produce IgY antibodies specifically against S.aureus and E.coli, the two principal bacteria causing mastitis in dairy cattle. The main results are as follows:Compared to the IgY harvest from the laying hens immunized with either S.aureus or E.coli, the titer was significantly higher (1:51200) when hens were simultaneously immunized with both bacterium.Salt Precipitation method was engaged as the first step of isolation in our research due to its high recovery and ability to sustain IgY activity. Sequencing gel-filtration indicated that the IgY can be up to 90% pure. This level purity and activity may have considerable application in the large scale production of IgY for therapertic purposes.The data from the inhibition in vitro studies demonstrated that the growth of both S.aureus and E.coli can be inhibited either in solid or liquid culture. There was no significantly difference (P<0.05) in the degree to which IgY antibodies inhibited S.aureus or E.coli. The Minimal Inhibitory Concentration (MIC) of IgY was detecteced as 35 mg/ml.In conclusion, inactivated S.aureus coupled with E.coli can be used as the complex antigen that fully caused hens immunoreaction and induce large amount of the specific antibody. Passive protection could be the next step in generating IgY antibodies that could be used for the effective control of mastitis in dairy cattle. Further work could be done based on our research, and now we are still studying on the mechanism of IgY passive protection in dairy cow mastitis.