Higher incorporation of heterologous chicken immunoglobulin Y compared with homologous quail immunoglobulin Y into egg yolks of Japanese quail (Coturnix japonica)

FcRY is a key molecule controlling maternal blood IgY transfer to yolks during egg development in avian species

Maternal immunoglobulin transfer plays a key role in conferring passive immunity to neonates. Maternal blood immunoglobulin Y (IgY) in avian species is transported to newly-hatched chicks in two steps: 1) IgY is transported from the maternal circulation to the yolk of maturing oocytes, 2) the IgY deposited in yolk is transported to the circulation of the embryo via the yolk sac membrane. An IgY-Fc receptor, FcRY, is involved in the second step, but the mechanism of the first step is still unclear. We determined whether FcRY was also the basis for maternal blood IgY transfer to the yolk in the first step during egg development. Immunohistochemistry revealed that FcRY was expressed in the capillary endothelial cells in the internal theca layer of the ovarian follicle. Substitution of the amino acid residue in Fc region of IgY substantially changed the transport efficiency of IgY into egg yolks when intravenously-injected into laying quail; the G365A mutant had a high transport efficiency, but the Y363A mutant lacked transport ability. Binding analyses of IgY mutants to FcRY indicated that the mutant with a high transport efficiency (G365A) had a strong binding activity to FcRY; the mutants with a low transport efficiency (G365D, N408A) had a weak binding activity to FcRY. One exception, the Y363A mutant had a remarkably strong binding affinity to FcRY, with a small dissociation rate. The injection of neutralizing FcRY antibodies in laying quail markedly reduced IgY uptake into egg yolks. The neutralization also showed that FcRY was engaged in prolongation of half-life of IgY in the blood; FcRY is therefore a multifunctional receptor that controls avian immunity. The pattern of the transport of the IgY mutants from the maternal blood to the egg yolk was found to be identical to that from the fertilized egg yolk to the newly-hatched chick blood circulation, via the yolk sac membrane. FcRY is therefore a critical IgY receptor that regulates the IgY uptake from the maternal blood circulation into the yolk of avian species, further indicating that the two steps of maternal-newly-hatched IgY transfer are controlled by a single receptor.

Neutralization of "Chaco eagle" (Buteogallus coronatus) serum on some activities of Bothrops spp. venoms

Several species of reptiles and mammals have components in their sera that can neutralize toxic components present in snake venoms. In this manuscript, we studied the neutralizing capacity of Chaco eagle's (Buteogallus coronatus) serum. This South American bird of prey eats snakes as a regular part of its diet and has anatomical features that protect from snakes' bites. The neutralizing potency of the Chaco eagle's serum was tested on lethal, hemorrhagic, procoagulant, and phospholipase activities of the venom of "yarará grande" (Bothrops alternatus) and on phospholipase activity of "yarará ñata" (Bothrops ammodytoides) venom; both snakes are known to be the prey of Chaco eagle. Sera of crested caracara (Caracara plancus-a scavenger, omnivorous pan-American bird of prey), secretary bird (Saggitarius serpentarius-an omnivorous bird of prey from Africa that can include venomous snakes in its diet), common hen (Gallus gallus), rat (Rattus norvegicus), mouse (Mus musculus), horse (Equus caballus), and dog (Canis lupus familiaris) were also tested to compare the inhibitory capacity of neutralization. To test isologous and xenologous neutralization, sera from Bothrops alternatus and white-eared opossum (Didelphis albiventris), respectively, were used due to their known inhibitory activity on Bothrops venoms. As a control for the neutralization activity, antibothropic antivenom was used. Chaco eagle's serum neutralized hemorrhagic and phospholipasic activity and slightly neutralized the coagulation and the lethal activity of Bothrops spp. venom. The neutralizing capacity was present in the non-immunoglobulin fraction of the serum, which showed components of acidic characteristics and lower molecular weight than IgY, in correspondence with the characteristics of PLA₂s and SVMPs inhibitors described in sera from some snakes and mammals. These studies showed that Chaco eagle's serum neutralizes all toxic activities tested at a higher level than sera from animal species in which inhibitors of snake venoms have not been described (p < 0.05), while it is lower or similar in neutralizing capacity to white-eared opossum and B. alternatus sera.

IgY technology: Methods for developing and evaluating avian immunoglobulins for the in vitro detection of biomolecules

The term “IgY technology” was introduced in the literature in the mid 1990s to describe a procedure involving immunization of avian species, mainly laying hens and consequent isolation of the polyclonal IgYs from the “immune” egg yolk (thus avoiding bleeding and animal stress). IgYs have been applied to various fields of medicine and biotechnology. The present article will deal with specific aspects of IgY technology, focusing on the currently reported methods for developing, isolating, evaluating and storing polyclonal IgYs. Other topics such as current information on isolation protocols or evaluation of IgYs from different avian species are also discussed. Specific advantages of IgY technology (e.g., novel antibody specificities that may emerge via the avian immune system) will also be discussed. Recent in vitro applications of polyclonal egg yolk-derived IgYs to the field of disease diagnosis in human and veterinary medicine through in vitro immunodetection of target biomolecules will be presented. Moreover, ethical aspects associated with animal well-being as well as new promising approaches that are relevant to the original IgY technology (e.g., development of monoclonal IgYs and IgY-like antibodies through the phage display technique or in transgenic chickens) and future prospects in the area will also be mentioned.

Evaluation of a receptor gene responsible for maternal blood IgY transfer into egg yolks using bursectomized IgY-depleted chickens

In avian species, maternal immunoglobulin Y (IgY) is transferred from the blood to the yolks of maturing oocytes; however, the mechanism underlying this transfer is unknown. To gain insight into the mechanisms of maternal IgY transfer into egg yolks, IgY-depleted chickens were generated by removing the bursa of Fabricius (bursectomy) during egg incubation, and their egg production and IgY transport ability into egg yolks were determined. After hatching, blood IgY concentrations of the bursectomized chickens decreased gradually until sexual maturity, whereas those of IgA remained low from an early stage of growth (from at least 2 wk of age). Chickens identified as depleted in IgY through screening of blood IgY and IgA concentrations were raised to sexual maturity. At 20 wk of age, both blood and egg yolk IgY concentrations in the IgY-depleted group were 600-fold lower than those of the control group, whereas egg production did not differ between the groups. Intravenously injected, digoxigenin-labeled IgY uptake into the egg yolk was approximately 2-fold higher in the IgY-depleted chickens than in the controls, suggesting that IgY depletion may enhance IgY uptake in maturing oocytes. DNA microarray analysis of the germinal disc, including the oocyte nucleus, revealed that the expression levels of 73 genes were upregulated more than 1.5-fold in the IgY-depleted group, although we could not identify a convincing candidate gene for the IgY receptor. In conclusion, we successfully raised IgY-depleted chickens presenting a marked reduction in egg yolk IgY. The enhanced uptake of injected IgY into the egg yolks of the IgY-depleted chickens supports the existence of a selective IgY transport mechanism in maturing oocytes and ovarian follicles in avian species.

Storage stability of anti-Salmonella Typhimurium immunoglobulin Y in immunized quail eggs stored at 4°C

Chicken egg yolk antibodies (IgYs) are extensively used for immunotherapy and immunodiagnostic purposes. Oral immunotherapy with specific IgYs is established as an efficient alternative to traditional antibiotic therapy in human and animals. Storing immunized eggs in refrigerator for a period of time could provide an inexpensive and convenient source of large volumes of specific antibodies. This study investigated the storage stability of anti- Salmonella Typhimurium IgYs in immunized quail egg yolks at 4°C over a period of more than 6 months. Salmonella spp.-free female Japanese quails (Coturnix coturnix japonica) were intramuscularly immunized whit Salmonella Typhimurium whole bacterial suspension (1.0×109 CFU/ml) emulsified with Freund adjuvants. During a period of 10 days after final immunization, eggs from each group were collected, randomized and stored at 4°C over a period of 200 days. Egg yolk IgY titer and specificity were determined using ELISA technique. S. Typhimurium specific IgY antibodies were detected in immunized quails and were significantly higher than the control group which confirmed the immunization procedure. Eggs from immunized quails can be collected and stored in 4°C refrigerator over a period of 2 months without any concern about the antibody degradation. After 80 days of storage at 4°C, although lower antibody titer was obtained in comparison to the first of study, anti-S. Typhimurium IgY level remained stable up to the 6 months without more significant declining. This trend will provide economical sources of polyclonal antibodies through reducing the number of immunized animals, management expenses and housing costs.

Production, purification, and evaluation of quail immunoglobulin Y against Salmonella typhimurium and Salmonella enteritidis

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Chicken egg yolk antibodies (IgYs) have been extensively used for immunotherapy and immunodiagnostic purposes.

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Production of specific IgYs against Salmonella typhimurium and Salmonella enteritidis were identified in Japanese quail.

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Formalin-inactivated Salmonella species induced higher immune responses over the heat-inactivated ones.

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Quail anti-Salmonella IgYs showed a high specificity to their corresponding immunogens.

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Quail can be considered as a valuable and inexpensive source for producing large scale of specific antibodies.

Salmonella species have been the major foodborne problems in food production systems, with Salmonella enterica serovars typhimurium (S. typhimurium) and enteritidis (S. enteritidis) being among the more common isolates. The oral administration of chicken egg yolk specific antibodies (IgYs) has been established as an efficient alternative for treatment and prevention of gastrointestinal pathogens including Salmonella. The present study was aimed to investigate the possible production of specific IgYs against Salmonella typhimurium and Salmonella enteritidis in quail egg yolks. Salmonella spp.-free female Japanese quails (Coturnix coturnix japonica) were intramuscularly immunized with formalin or heat-inactivated Salmonella immunogens (1.0 × 10⁹ CFU/mL) emulsified with Freund adjuvants. Egg yolk IgYs were purified using ammonium sulfate precipitation method. Anti-Salmonella IgYs titer and specificity were determined using enzyme-linked immunosorbent assay (ELISA) and western blot analysis. Salmonella specific IgYs detected in the immunized quails were significantly higher than those of the control group, which confirmed the immunization procedure. Specific IgYs against S. typhimurium and S. enteritidis were identified in both groups immunized with heat or formalin-inactivated immunogens. However, formalin-inactivated immunogens induced relatively higher immune responses over the heat-inactivated ones. Quail anti-Salmonella IgYs showed a high specificity to their corresponding immunogens, with moderate cross-reactivity to other members of Enterobacteriaceae family. Quail can be regarded as a valuable and inexpensive source for producing large-scale of specific antibodies that can be used for immunodiagnostic and immunotherapeutic purposes.

An ELISA for quantifying quail IgY and characterizing maternal IgY transfer to egg yolk in several quail strains

In avian species, maternal blood immunoglobulin Y (IgY) is transferred to the egg yolks of maturing oocytes, but the mechanism underlying this transfer is unknown. To gain insight into the mechanism of maternal IgY transfer in quail, we established an enzyme-linked immunosorbent assay (ELISA) for the quantitation of quail IgY. We characterized strain differences in blood and egg yolk IgY concentrations and exogenously injected IgY-Fc uptakes into egg yolks. A specific rabbit polyclonal antibody to quail IgY was raised for the ELISA. Blood and egg yolk IgY concentrations were determined in six quail strains (one inbred strain, L; four closed population strains, AWE, DB, PS, WE; one commercial strain, Commercial). The birds were also injected with digoxigenin-labeled quail IgY-Fc, and its uptakes into laid eggs were compared. The strain difference in blood and egg yolk IgY concentrations was at most 2.5-fold, between PS and AWE. The rank order of IgY concentrations was AWE, Commercial, DB, L≥WE≥PS. A significant positive correlation (|R|=0.786) between individual blood IgY and egg yolk IgY and the concentrated egg yolk IgY (1.5-2-fold) against blood IgY was observed. Interestingly, there was a significant inverse correlation (|R|=0.452) between injected IgY-Fc uptakes and the blood IgY concentration, implying competition of the injected IgY-Fc and blood IgY in the process of IgY uptake into egg yolks. In conclusion, we successfully determined blood and egg yolk IgY concentrations in various quail strains by a quail IgY-specific ELISA. The concentrated egg yolk IgY against the blood IgY and the inverse relationship of exogenous IgY-Fc uptake against the blood IgY supports the existence of a selective IgY transport mechanism in avian maturing oocytes.

Factors affecting the levels of protection transferred from mother to offspring following immune challenge

INTRODUCTION

The transfer of antibodies from mother to offspring is key to protecting young animals from disease and can have a major impact on responses to infection and offspring fitness. Such maternal effects also allow young that may be exposed to disease in early life to focus resources on growth and development at this critical period of development. Maternally transferred antibodies are therefore an important source of phenotypic variation in host phenotype as well as influencing host susceptibility and tolerance to infection across generations. It has previously been assumed the transfer of antibodies is passive and invariant and reflects the level of circulating antibody in the mother at the time of transfer. However, whether females may vary in the relative amount of protection transferred to offspring has seldom been explored.

RESULTS

Here we show that females differ widely in the relative amount of specific blood antibodies they transfer to the embryonic environment (range 9.2%-38.4% of their own circulating levels) in Chinese painted quail (Coturnix chinensis). Relative transfer levels were unrelated to the size of a female's own immune response. Furthermore, individual females were consistent in their transfer level, both across different stages of their immune response and when challenged with different vaccine types. The amount of antibody transferred was related to female condition, but baseline antibody responses of mothers were not. However, we found no evidence for any trade-offs between the relative amount of antibody transferred with other measures of reproductive investment.

CONCLUSIONS

These results suggest that the relative amount of antibodies transferred to offspring can vary significantly and consistently between females. Levels of transfer may therefore be a separate trait open to manipulation or selection with potential consequences for offspring health and fitness in both wild and domesticated populations.

Avian IgY is selectively incorporated into the egg yolks of oocytes by discriminating Fc amino acid residues located on the Cυ3/Cυ4 interface

In avian species, maternal IgY is selectively incorporated into the egg yolks of maturing oocytes, but the relevance of receptor-mediated uptake is unclear. Here we investigated the critical amino acid residues of IgY required for egg yolk transport by conducting mutational analyses of selected residues located along the Cυ3 and Cυ4 domains of chicken IgY. Recombinant wild-type IgY-Fc (WT) and its mutants were synthesized, and their uptakes into the egg yolks of quail were determined. Among the 17 amino acid residues located on the Cυ3/Cυ4 interface, the substitution of Y363 at the Cυ3 domain to alanine abolished the IgY-Fc uptake into egg yolks. The comprehensive substitution of Y363 with other amino acids revealed that the residue at 363 needs to be allocated with aromatic amino acids to maintain the high transport ability. The deglycosylation of the N-linked carbohydrate chain by substituting N407 at the Cυ3 domain with alanine also caused a marked reduction of IgY-Fc uptake. The microscopic detection of the injected WT and Y363A mutant in ovarian follicles showed that the WT was concentrically accumulated in yolk granules, whereas the Y363A mutant was hardly accumulated in yolk granules, but it had infiltrated into the granulosa cell layer, suggesting that a major hurdle disturbing the infiltration of the Y363A mutant lies on the inside of the granulosa cell layer. The identification of important amino acid residues required for efficient IgY transport enhances our understanding of the molecular mechanisms underlying IgY transport through a specific IgY receptor in ovarian follicles.

Microscopic detection of IgY-Fc binding signal in the inner layers of ovarian follicular tissue in quail

In avian species, it has been assumed that an Fc receptor in the ovarian follicles mediates immunoglobulin Y (IgY) transport into the yolk. However, no such receptor responsible for IgY has been identified to date. To examine potential IgY binding activity in the entire ovarian follicle, whole-mount sections of quail ovarian follicle were incubated with the Fc fragment of chicken IgY (cIgY). Whole-mount frozen sections of the second largest ovarian follicle were prepared, and then the sections were incubated with digoxigenin-labeled Fc or Fab fragments of cIgY. Microscopic observation revealed that incubation with the cIgY-Fc fragment produced a binding signal in the inner layer of the ovarian follicular tissues, most likely in the granulosa cell layer. However, no such signal was detected when the sections were incubated with cIgY-Fab. Coincubation of the ovarian sections with Alexa488-labeled cIgY-Fc and antiserum raised against ZP1, an envelope protein specifically localized in the perivitelline layer, demonstrated that the source of the Fc binding signals partly coincided with the perivitelline layer. In conclusion, our data suggest that potential IgY binding substances interacting with the Fc domain are present in the inner layers of ovarian follicular tissues, most likely in the granulosa cell layer and/or in the perivitelline layer.