Metrics details Abstract In recent years, the use of in-feed antibiotics for growth and disease prevention in livestock production has been under severe scrutiny. The use and misuse of in-feed antibiotics has led to problems with drug residues in animal products and increased bacterial resistance. Chicken egg yolk antibodies IgY have attracted considerable attention as an alternative to antibiotics to maintain swine health and performance. Oral administration of IgY possesses many advantages over mammalian IgG such as cost-effectiveness, convenience and high yield.
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References During the past 20 years, the use of chickens instead of mammals for antibody production has increased. A major advantage of using birds is that the antibodies can be harvested from the egg yolk instead of serum, thus making blood sampling obsolete. In addition, the antibody productivity of an egg-laying hen is much greater than that of a similar sized mammal . Purification of immunoglobulin from mammalian blood is time-consuming and expensive.
Today, hens are recognized as a convenient and inexpensive source of antibodies. It has been reported that the amount of immunoglobulin that can be yielded from one egg of an immunized hen is as much as that can be obtained from ml of rabbit blood. Antibodies Antibodies are produced by the immune system of an animal in a specific response to a challenge by an immunogen.
Immunogens antigens are molecules which can induce a specific immune response and are usually foreign proteins or carbohydrates or sometimes lipids and nucleic acids. Antibodies are secreted from plasma cells which have differentiated from B lymphocytes after appropriate stimulation by the foreign immunogen. Chicken egg yolk antibody IgY has received much attention in recent years because it can be easily prepared in high concentration and is both affordable and safe .
IgY is successfully used in medical immune testing, diagnosis, hetero grafts and therapy. New vaccine technology has led to vaccines containing highly purified antigens with improved tolerability and safety profiles, but the immune response they induce is suboptimal without the help of adjuvants. Gottstein and Hemmeler  reported Chickens store high contents of IgY in the yolk and are considered to be efficient antibody producers. IgY production Immunization of the hens: Specific IgY development and production can be achieved by immunizing laying hens with the target antigen.
However, the resulting immune response of the immunized hens cannot bevery predictable. Mainly five factors influence this response: the antigen dose and molecular weight , the type of adjuvant used, the route of application, the immunization frequency, and the interval between immunizations . The dose of antigen influences significantly the immune response and the antibody titer that is evoked.
Too much or too little antigen may induce suppression, sensitization, tolerance or other unwanted immune modulation. Route of application: The most common route for antigen injection in hens for IgY production is the intramuscular route. Injection is usually performed in the breast muscle. Chicken can also be injected subcutaneously in the neck. With very young animals, it may be preferable to inject intramuscularly into the breast muscle, because subcutaneous injection is more difficult to perform and can therefore cause more distress .
Immunization frequency and interval between immunizations: The total number of immunizations required depend on the type and dose of the antigen as well as the adjuvant employed. At least two immunizations have to be given. Yolk antibody titres should be checked 14 days after the last immunization. The success of an immunization protocol depends also on the interval between the first and second and subsequent immunizations.
Often reported interval is two to four weeks . Isolation and purification methods for IgY Several methods were described in the s for purifying IgY based on the strategy of separation of proteins levitins from lipoproteins lipovitellins and the rest of the yolk lipids using extraction with organic solvents with rather low yields of antibody. However, purification methods based on organic solvents like chloroform remain in use.
Other methods are based on affinity chromatography or on dilution of the yolk followed by a freezingthawing process after which the process consists of ion exchange chromatography and salt precipitations often combining a number of salts like for e. Water dilution method found to be superior in terms of ease of use and large scale production of IgY. This is simple rapid and efficient means of purifying IgY with high activity .
Applications of IgY in biomedical research and in human and veterinary medicine Powdered whole eggs or yolks have been used as an inexpensive alternative for the IgY treatment of enteric diseases in veterinary medicine Kumaran et al. Studies using both animal models and trials in field herds have been carried out.
These studies confirmed that treatment of diarrhea in calves and piglets with specific egg yolk Abs has achieved significant prophylactic and therapeutic benefits. Another effect of IgY binding to bacterial surface antigens is a marked impairment of bacterial attachment to the intestinal mucosa Lee et al.
Thus, therapeutic IgY administration could reduce the clinical use of antibiotics, and so could lower the risk that bacteria will develop antibiotic resistance.
Production of Igy Antibodies from Egg Yolk of Immunized Chickens
Full size table Although adhesin-mediated colonization is a precondition for ETEC pathogenesis, enterotoxins are thought to be the central virulence determinants leading to diarrhea diseases and may also play a role in the colonization process [ 30 , 40 , 41 ]. Therefore, the ideal protective agent against ETEC infection should include protection against both adhesin antigens and enterotoxins [ 30 ]. In contrast with LTB and STa, enterotoxins STa and STb are poorly immunogenic because of their small size, but they can attain immunogenicity when coupled chemically or genetically to an appropriate carrier [ 42 , 43 ]. These results indicate that the recombinant STa-LTB-STb protein has the potential to serve as an effective and convenient polyvalent toxoid which can provide broad protection against ETEC-induced diarrhea. This study was conducted with mice and a piglet study should be conducted to confirm these findings. Salmonella Salmonella infection has been recognized as one of the most common foodborne diseases in humans, causing 1. This disease can occur via foodborne transmission, animal contact, or environmental spread [ 48 , 49 ], and farm animals are the most likely source of human salmonellosis [ 50 , 51 ].
Chicken Egg Yolk Antibodies, Production and Application
The fact that antibodies can also be detected in the yolk of eggs laid by immunised hens, led to the development of the yolk antibody technology as an alternative method less stressful to animals. Hens can be kept under nearly natural conditions and antibodies be isolated from the eggs. Further, the IgY-technology has the advantage that avian antibodies can be produced against several antigens which do not induce a immune response in mammals. Protocols on how to keep and immunise hens and on the extraction, isolation and use of antibodies from yolk are described in detail in this manual Medical books "Chicken Egg Yolk Antibodies, Production and Application: IgY-Technology Springer Lab Manuals ".
Chicken egg yolk antibodies, production and, application : IgY-Technology