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BackgroundIgY antibodies are serum immunoglobulin in birds, reptiles and amphibians, and are transferred from serum to egg yolk to confer passive immunity to their embryos and offspring. Currently, the oral passive immunization using chicken IgY has been focused as an alternative to antibiotics for the treatment and control of diarrhea in animals and humans. This systematic review was focused to determine the effect of IgY in controlling and preventing diarrhea in domesticated animals including Piglets, Mice, Poultry and Calves.Methods and ResultsPrevious research reports focused on treatment effect of Chicken IgY against diarrhea were retrieved from different electronic data bases (MEDLINE, EMBASE, SPRINGER-LINK, WILEY, AGRICOLA, MEDWELL Journals, Scientific Publish, Chinese articles from Core periodicals in 2012). A total of 61 studies in 4 different animal classes met the inclusion criteria. Data on study characteristics and outcome measures were extracted. The pooled relative risk (RR) of 49 studies of different animals [Piglets – 22; Mice – 14; Poultry – 7 and Calves – 6] in meta-analyses revealed that, IgY significantly reduced the risk of diarrhea in treatment group when compare to the placebo. However, the 95% confidence intervals of the majority of studies in animal class piglets and calves embrace RR of one. The same results were obtained in sub group analyses (treatment regiment – prophylactic or therapeutic; pathogen type – bacterial or viral). Perhaps, this inconsistency in the effect of IgY at the individual study level and overall effect measures could be influenced by the methodological heterogeneity.ConclusionThe present systematic review (SR) and meta-analysis demonstrated the beneficial effect of IgY. This supports the opinion that IgY is useful for prophylaxis and treatment. However, more intensive studies using the gold standard animal experiments with the focus to use IgY alone or in combination with other alternative strategies are indispensable.

The biomedical applications of antibodies as prophylactics, therapeutics and diagnostics are developing rapidly. Neonatal Fc receptor (FcRn) is a major IgG Fc receptor capable of facilitating the translocation of IgG. FcRn can protect IgG from intracellular catabolism, thereby increasing its half-life. In recent decade, the interaction between FcRn and the Fc region has been reported with the focuses on either prolonging the plasma half-life of therapeutic IgG or shortening the half-life of pathogenic IgG. The FcRn-IgG interaction can be altered by modifying the Fc region to change their affinity (increase or decrease), and/or by reducing the Fc fragments of IgG to enhance its penetration into tissues or cells. By over expression of FcRn, the exogenous catabolism can be reduced, meanwhile the circulating IgG level could be enhanced. It has been confirmed in different FcRn over-expressed transgenic mice models, substantial humoral responses against antigens with weak immunogenicity can be mounted. In addition, designing inhibitors for FcRn-IgG interaction is another application prospect for treating IgG-mediated autoimmune diseases. Recent research advancements strengthen the understanding that FcRn is a key and promising drugable target in IgG intervention in the field of antibody engineering.

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Egg yolk has been considered a promising source of antibodies. Our study was designed to compare six principal IgY extraction methods (water dilution, polyethylene glycol [PEG] precipitation, caprylic acid extraction, chloroform extraction, phenol extraction, and carrageenan extraction), and to assess their relative extraction efficiencies and the purity of the resulting antibodies. The results showed that the organic solvents (chloroform or phenol) minimised the lipid ratio in the egg yolk. The water dilution, PEG precipitation and caprylic acid extraction methods resulted in high yields, and antibodies purified with PEG and carrageenan exhibited high purity. Our results indicate that phenol extraction would be more suitable for preparing high concentrations of IgY for non-therapeutic usage, while the water dilution and carrageenan extraction methods would be more appropriate for use in the preparation of IgY for oral administration.