IgY antibodies for the immunoprophylaxis and therapy of respiratory infections

Abbas, Aymn Talat; El-Kafrawy, Sherif Aly; Sohrab, Sayed Sartaj; Azhar, Esam Ibraheem Ahmed

IgY antibodies have numerous advantages. 20 First, they can be naturally produced, avoiding environmental contamination because they are not synthetic drugs. In addition, they do not induce specific resistance because they are directed against multiple antigenic targets. Because IgY antibodies specifically target a particular pathogen, they do not affect the microbial population of the host. Consequently, they do not induce the unpleasant side effects that are typical of antibiotics. Finally, IgY antibodies are not deposited in meat, hence avoiding potential violations of regulations in countries that forbid the use of antibiotics for poultry and livestock. 68 IgY antibodies used for passive immunotherapy also have advantages in addition to having local, rapid activity to the pathogen, they can be given to a wide range of individuals of any age, ranging from infants to adults and including immunodeficient patients and pregnant women. 20 As natural components of eggs, the IgY antibodies tend to be nontoxic. Further, they can be stored for months in powder form at low moisture without the need for refrigeration, and they are cheaper and faster to produce than vaccines. 61 Use of IgY antibodies also has general advantages in the context of immunotherapy. Egg collection is pain-free and animal friendly, which is beneficial from the perspective of animal welfare. Further, IgY has greater binding avidity to target antigens than mammalian IgG. 69 IgY antibodies can also be produced against conserved mammalian proteins more easily and more successfully than IgG antibodies can be produced in other mammals due to evolutionary distance between mammals and birds. 70 They also need lower antigen quantities to induce an efficient immune response. 68 IgY can be stored in eggs for at least 1 year at 4°C. 71 Large quantities of IgY antibodies can be produced by one chicken (about 22 g/year), and 2% to 10% of these antibodies are target specific, 25, 72 which exceeds the annual production from four rabbits. 68 Furthermore, the production of eggs for human consumption is already carried out on an industrial scale, making low cost production of IgY in large quantities technically feasible. 36, 73 IgY structure Chicken IgA and IgM are structurally and functionally analogous to mammalian IgA and IgM, while IgY differs from mammalian IgG despite their similar function. IgY is the predominant serum antibody in birds, reptiles, amphibians, and lungfish, 16, 74 and its serum concentrations far exceed those of IgA or IgM. 33 IgYs are concentrated in the egg yolk, while IgA and IgM are found in the egg white. Although functional similarity exists between IgY and IgG, their structures are markedly different, as shown in (Figure 2 ). 25 Among the differences, the H chain of IgYs have one variable region (VH) and four constant regions (CH) regions, while mammalian IgGs have only three CH regions. Also, IgY lacks a hinge region between the CH1 and CH2 domains, making it less flexible than IgG. 75