Companies working with Avian Antibodies: Amicus Biotech 

Differences and Advantages of Avian Antibodies

It is known that birds (e.g., laying hens) transfer their immunity to the yolk of their eggs and thereby to their offspring (Polson, US4,550,019). A laying hen can produce a 50-60 gm egg (more antibodies than a typical blood sample) every 24 hours. Chicken secrete all three classes of antibodies into their eggs. IgG (aka IgY) is found in high concentration in the yolk whereas IgA and IgM antibodies are present in the white portion  (US 2007/0238097 A1).

There exist substantial differences between the gamma-globulins which occur in the egg yolk of fowl eggs and mammalic *including human) gammaglobulins. First, the source materials are different. Conventional mammalic immunoglobulin preparations have been mostly recovered form blood serum. This is obtained form whole blood after removal of fibrinogen by clotting. The serum is a clear liquid containing about 6.5-7% by volumen of dissolved proteins represented by about 0.8-1% gammaglobulin, 3.5% albumin, 2.5% miscellaneous proteins. There is no caseinaceous matter in mammalic serum and little or no free lipid matter. By contrast, egg yolk contains about 25% by volume yolk granules and another 25% of caseinaceous proteins and free lipids. Second, the immunoglobulins themselves in egg yolk are chemically and physically significantly different from immunoglobulins in human or other mammalian serum. Differences exist in amino acid compositions and electrophoretic mobilities (polson, US4,550,019). 

Unlike in mammals, there are only three classes of antibodies identified in chicken, IgM, IgA and IgY. Among them, IgY is the predominant form which is continually synthesized, secreted into the blood and transferred to the egg yolk, where it accumulates to a concentration even higher than that in the blood. It has been reported that a single egg contains as much Abs as an average bleed from a rabbit (Wang, 13/956511). 

IGY Structure and Isoforms

Ducks and geese produce three kinds of serum immunoglobulins; IgM and two isoforms of IgY antibodies, a full lenght isoform (IgY(Fc) and a truncated isoform (IgY(deltaFc)) (Y-Neng, EP1371665). 

The intact IgY(Fc) antibody possessed two heavy and two light cains, with the heavy chain having one variable and four constant domains. The molecular weight of IgY(Fc) is about 180 kDa and it has a sedimentation coefficeint of 7.8 Svedberg units (S). The truncated form of IgY(Fc) lacks two Fc domains (CH3 and CH4) of the heavy chain and is similar to a F(ab’)2 fragment of an IgG antibody. IgY(deltaFc) has a molecular weight of about 120 kDa and a sedimentation coefficient of c.7. Henderson (US14/020469) 

Advantages to Using Avian Antibodidies

Avian immunogloublins isolated form egg yolk (so-called IgY) have several important advantages over conventional IgG antibodies due to their higher surface stability, lower corss-reactivity, stronger avidity and higher binding capacity (Fang, Frontiers of Pharmaceuticals and Biotechnology, 4, 2003). 

IgY Isolation: (See outline)

IgA and IgM Isolation

Fackrell (US 13/177114) discloses a method of isolating IgA and IgM antibodies from the egg white by fractionating the white of said egg by raising the volume of the egg white using water, lowering the pH, filtering out the insoluble IgM fraction. The IgA solution is then salting out with amonium sulphate, dialyzing the IgA precipitate and drying the IgA. 

Purification Schemes Following Avian Antibody Isolation

Affinity Purification: Williams (US2004/0115215) discloses using affinity columns containing recombinant toxin A protein from 6 defined intervals to isolate region specific IgY antibodies pools. The 6 intervals were slected because they spanned the entire protein and thus are part of an epitope mapping of the Toxin A gene. IgY was applied to the affinity column so as to isolate region specific antibodies specific to each of the six subregions. The columns were washed and Abs eluted. The antibodies can subsequently be tested for nuetralization ability of toxin A protein. The procedure is designed toxin A subregions that are essential for producing neutralizing antibodies. 

Larsen (US 12/299670 and WO2007/079755) also discloses obtaining Igy antibodies having specificity for secondary antigens to be tested. Accordingly to the proecdure, a library of peptide is used to immunize avian species (e.g., fowls). The antibodies can thereafter be purified using a peptide/protein or chemical which the customer wants antibodies against by coupling the peptide/protein to a resin. The antibodies which is also a library binds the antigens on the resin and antigen specific antibodies are eluted from the column. For the related concept of “epitope mapping” of antibodies see “immunology”. 

Applications

Passive immunization by oral administration of IgY: The method of Polson, A., M.B. von Wechmar and M.H. van Regenmortel, “Isolation of Viral IgY antibodies from yolks of immunized hens,” Immunological Communicaitons 9:475-493 (1980  can be used to produce a preparation of egg-yolk antibodies. In brief, laying hens are inoculated with antigen-adjuvant which causes the hens to produce anti-antigen antibodies which are passively transferred into the egg yold of eggs laid by the hens. Egg yolks or whole eggs containing the antibody can be collected and homogenized to form an emulsion which can be dried to form a powder containing the antibody. This powder can be formulated for oral administration and then adminsitered orally to a human or non-human animal subject (US2010/0233184A1). Because IgY is susceptible to degradation in the gastrointestinal tract, enteric pH sensitive coatings can be used.