Ulcer disease prophylaxis in koi carp by bath immersion with chicken egg yolk containing anti-Aeromonas salmonicida IgY

Development of a filter device for the prevention of aquatic bacterial disease using a single-chain variable fragment (scFv)-conjugated affinity silk

Infectious disease is one of the most serious problems in the aquaculture industry for ornamental or edible fish. This study attempted to develop a new device for preventing an aquatic bacterial disease, ulcer disease, caused by Aeromonas salmonicida (As), using “affinity silk”. Affinity silk is a silk protein-containing fibroin L-chain (FibL) fused to the single-chain variable fragment (scFv). It can be easily processed into different formats such as fibers, gels, sponges, or films. A transgenic silkworm that could express a cDNA construct containing FibL fused to an scFv derived from a monoclonal antibody (MAb) against As was successfully generated. An enzyme-linked immunosorbent assay was used to detect As by employing 96-well plates coated with scFv-conjugated affinity silk. As could be captured efficiently by glass wool coated with affinity silk in the column. Furthermore, the air-lift water filter equipped with the affinity silk-coated wool could considerably reduce the concentration of As in water and was estimated to have sufficient ability to trap a lethal dose of As. These findings show that the “affinity silk filter” is a potential device for the prophylaxis of aquatic animal diseases.

Immunoglobulin Y for Potential Diagnostic and Therapeutic Applications in Infectious Diseases

Antiviral, antibacterial, and antiparasitic drugs and vaccines are essential to maintaining the health of humans and animals. Yet, their production can be slow and expensive, and efficacy lost once pathogens mount resistance. Chicken immunoglobulin Y (IgY) is a highly conserved homolog of human immunoglobulin G (IgG) that has shown benefits and a favorable safety profile, primarily in animal models of human infectious diseases. IgY is fast-acting, easy to produce, and low cost. IgY antibodies can readily be generated in large quantities with minimal environmental harm or infrastructure investment by using egg-laying hens. We summarize a variety of IgY uses, focusing on their potential for the detection, prevention, and treatment of human and animal infections.

Oral administration of microencapsulated egg yolk immunoglobulin (IgY) in turbot (Scophthalmus maximus) to combat against Edwardsiella tarda 2CDM001 infections

Edwardsiellosis, an extremely harmful disease can be caused by Edwardsiella tarda, severely restricts the development of turbot (Scophthalmus maximus) farming worldwide, especially in China. This study aimed to establish an effective and feasible prophylaxis by feeding chitosan-alginate coated egg yolk immunoglobulin (IgY) against E. tarda 2CDM001 infections in the process of turbot farming. Enzyme-linked immunosorbent assays proved that the obtained specific IgY could specifically target E. tarda 2CDM001 and five other E. tarda isolates (1a5p, Hz-s, 1a1s, fs-a1 and 58p8). In-vitro, the bacteriostatic effects of specific IgY showed dose dependencies at concentrations ranging from 1 to 10 mg/mL. Moreover, E. tarda 2CDM001 incubated with 10 mg/mL specific IgY could induce the destruction of cell wall structures and significantly decrease the bacterial surface hydrophobicity (p < 0.05). In this study, turbots were challenged with 10⁷ CFU E. tarda 2CDM001 after seven days of continuous feeding with basal diets containing microencapsulated IgYs. Survival rates of the 5%, 3% and 1% microencapsulated specific IgY groups were 63.3%, 56.7% and 20% on the tenth day post infection, respectively, while the turbots in the positive control and non-specific IgY groups all died within ten days. Oral administration of basal diets containing 5% microencapsulated specific IgY significantly reduced IL-1β, IL-8, TNF-α and C3 transcript levels in the head kidney and spleen of turbots compared with the positive and non-specific IgY groups at 24 h after E. tarda 2CDM001 challenging (p < 0.05). Pathological increase of leukocytes in the specific IgY group was significantly lower than that in the positive control and non-specific IgY groups (p < 0.05), decreasing slowly after 24 h of infection and showing a recovery trend. Erythrocyte counts and hemoglobin concentrations of turbots in positive and non-specific IgY groups showed a marked decrease compared with the negative and specific groups at 96 h after E. tarda 2CDM001 infection (p < 0.05). These results suggest that passive immunity via feeding microencapsulated specific IgY could be used as a valuable preventative in turbot against E. tarda 2CDM001 infections.

Egg yolk antibodies (IgY) and their applications in human and veterinary health: A review

Egg yolk constitutes a relevant alternative source of antibodies. It presents some advantages over mammalian serum immunoglobulins regarding productivity, animal welfare and specificity. The main immunoglobulin present in avian blood (IgY) is transmitted to their offspring and accumulates in egg yolks, which enables the non-invasive harvesting of high amounts of antibodies. Moreover, due to structural differences and phylogenetic distance, IgY is more suitable for diagnostic purposes than mammalian antibodies, since it does not react with certain components of the human immune system and displays greater avidity for mammalian conserved proteins. IgY has been extensively used in health researches, as both therapeutic and diagnostic tool. This article aims to review its applications in both human and veterinary health.

Features of chicken egg yolk immunoglobulin (IgY) against the infection of red-spotted grouper nervous necrosis virus

Red-spotted grouper nervous necrosis virus (RGNNV) is one of the most important viruses which mainly infects the larva of marine and freshwater fish with high mortality and affects the fishery industry worldwide. Currently, there are no effective vaccines available for the fish larva infected with NNV. Immunoglobulin yolk (IgY) origin of oviparous animals is passed from the blood serum and concentrated in the egg yolk. With the advantages of high yield, cost-effectiveness, and high stability, IgY can be widely used in passive immunization, especially in young animals in which adaptive immunity is not fully developed. In this study, we have cloned and expressed the recombinant capsid protein of RGNNV in Escherichia coli and used as an immunogen for generating specific anti-RGNNV IgY antibody in laying hens. Water-soluble fractions (WSF) of the specific IgY were isolated from egg yolk and purified by two-step precipitation with saturated ammonium sulfate salting. By Enzyme linked immunosorbent assay (ELISA), the titer of the IgY reached a peak at the 6th week post of immunization and had a strong stability at a wide range of temperature, pH, and pepsin enzyme digestion. The purified IgY was competent to neutralize and completely inhibited the RGNNV replication in the grouper fin cell line (GF-1), indicating that it was highly specific and effectively recognized RGNNV. The results will pave a new way for the prevention of RGNNV infection.

Probiotic Lactobacillus johnsonii BS15 Improves Blood Parameters Related to Immunity in Broilers Experimentally Infected with Subclinical Necrotic Enteritis

The probiotic strain Lactobacillus johnsonii BS15 could exert beneficial effects on growth performance, lipid metabolism, and intestinal microflora in healthy broilers and those afflicted with subclinical necrotic enteritis (SNE). In particular, BS15 prevents SNE by enhancing intestinal immunity. To further understand the immune regulatory mechanism of BS15, we evaluated its effects on the overall immunity of broilers by determining blood parameters in healthy and SNE broilers. In this study, two experiments were conducted. Experiment 1 involved a 42-day experimental period and used 450 1-day-old male chicks. The chicks were randomly divided into three groups and fed with a basal diet with or without 1 × 10⁵ or 10⁶ colony-forming units (cfu) BS15/g as feed. Experiment 2 involved a 28-day experimental period and used 180 1-day-old male chicks. The chicks were randomly allotted into three groups and given with or without 1 × 10⁶ cfu BS15/g BS15 as feed. SNE infection was treated in all broilers, except in those in the normal diet group. Antioxidant abilities, immunoglobulins, and cytokines in the serum were assessed. T-lymphocyte subsets in peripheral blood were also determined. The first experiment demonstrated that BS15 enhanced the antioxidant abilities; the serum levels of immunoglobulins, interleukin-2, and interferon-gamma; and CD3⁺CD4⁺ T-lymphocyte percentage in peripheral blood on day 21. However, limited significant changes were observed on day 42. The second experiment revealed that BS15 supplementation positively influenced the antioxidant abilities and increased the serum levels of immunoglobulins and cytokines that were affected by SNE. BS15 also positively affected T-lymphocyte subsets in peripheral blood during SNE infection. These findings suggest that BS15 supplementation may prevent SNE in broilers by improving blood parameters related to immunity and enhancing intestinal immunity. Furthermore, BS15 supplementation can improve blood parameters in healthy broilers, especially at the starter phase.

Use of common carp (Cyprinus carpio) and Aeromonas salmonicida for detection of immunomodulatory effects of chemicals on fish

To develop a test for assessing the immunomodulatory effects of chemical pollutants on fish, we evaluated the effects of dexamethasone on the natural host-pathogen interaction between common carp (Cyprinus carpio) and Aeromonas salmonicida. Carp were exposed to 1mgL^-1 dexamethasone for the entire experimental period. One week after the exposure test started, the exposed fish, as well as unexposed fish, were bath-infected with A. salmonicida. One hundred percent mortality was observed in bacteria-infected fish exposed to dexamethasone, whereas no infection-associated mortality was observed in infected fish in the absence of dexamethasone exposure. In a separate experiment, dexamethasone exposure significantly suppressed hemolytic complement activity in bacteria-infected fish. These results clearly indicate that exposure to a high concentration of dexamethasone suppressed the carp immune system and caused subsequent mortality. Thus, this proposed test method is likely to be useful for evaluating the immunomodulatory effects of chemicals in fish.

Passive protection effect of anti-Vibrio anguillarum IgY-encapsulated feed on half-smooth tongue sole (Cynoglossus semilaevi) against V. anguillarum

Vibrio anguillarum is one of the most harmful pathogens associated with hemorrhage septicemia syndrome in the half-smooth tongue sole (C. semilaevis) due to its high virulence. In this study, we attempted to treat half-smooth tongue sole with anti-V. anguillarum egg yolk powder to elicit a passive immunity directly against V. anguillarum infection. Anti-V. anguillarum IgY was β-cyclodextrin encapsulated in egg yolk powders as feed, which could avoid antibody inactivation in the gastrointestinal tract of half-smooth tongue sole. The IgY had an inhibiting effect on the infection of V. anguillarum in vitro. The survival rate of half-smooth tongue sole fed with basal diet containing 15% anti-V. anguillarum egg yolk powder was 70% after 7 days post-V. anguillarum challenge (10(7) CFU), which was significantly higher than those fed without anti-V. anguillarum egg yolk powder. As well, the bacterial burden in blood, liver, spleen and kidney was significantly lower in half-smooth tongue sole fed with specific IgY than those fed with non-specific IgY. These results suggested that pathogen-specific IgY may provide a valuable treatment for vibriosis infection and can be a promising food additive.

Passive Immune-Protection of Litopenaeus vannamei against Vibrio harveyi and Vibrio parahaemolyticus Infections with Anti-Vibrio Egg Yolk (IgY)-Encapsulated Feed

Vibrio spp. are major causes of mortality in white shrimp (Litopenaeus vannamei) which is lacking adaptive immunity. Passive immunization with a specific egg yolk antibody (IgY) is a potential method for the protection of shrimp against vibriosis. In this study, immune effects of the specific egg yolk powders (IgY) against both V. harveyi and V. parahaemolyticus on white shrimp were evaluated. The egg yolk powders against V. harveyi and V. parahaemolyticus for passive immunization of white shrimp were prepared, while a tube agglutination assay and an indirect enzyme-linked immunosorbent assay (ELISA) were used for detection of IgY titer. Anti-Vibrio egg yolk was encapsulated by β-cyclodextrin, which could keep the activity of the antibody in the gastrointestinal tract of shrimp. The results showed that the anti-Vibrio egg powders had an inhibiting effect on V. harveyi and V. parahaemolyticus in vitro. Lower mortality of infected zoeae, mysis, and postlarva was observed in groups fed with anti-Vibrio egg powders, compared with those fed with normal egg powders. The bacterial load in postlarva fed with specific egg powders in seeding ponds was significantly lower than those fed with normal egg powders in seeding ponds. These results show that passive immunization by oral administration with specific egg yolk powders (IgY) may provide a valuable protection of vibrio infections in white shrimp.

Passive immunisation, an old idea revisited: Basic principles and application to modern animal production systems

Immunisation by administration of antibodies (immunoglobulins) has been known for more than one hundred years as a very efficient means of obtaining immediate, short-lived protection against infection and/or against the disease-causing effects of toxins from microbial pathogens and from other sources. Thus, due to its rapid action, passive immunisation is often used to treat disease caused by infection and/or toxin exposure. However immunoglobulins may also be administered prior to exposure to infection and/or toxin, although they will not provide long-lasting protection as is seen with active immunisation (vaccination) in which an immunological memory is established by controlled exposure of the host to the pathogen in question. With multi-factorial infectious diseases in production animals, especially those that have proven hard to control by vaccination, the potential of passive immunisation remains big. This review highlights a number of examples on the use of passive immunisation for the control of infectious disease in the modern production of a range of animals, including pigs, cattle, sheep, goat, poultry and fish. Special emphasis is given on the enablement of passive immunisation strategies in these production systems through low cost and ease of use as well as on the sources, composition and purity of immunoglobulin preparations used and their benefits as compared to current measures, including vaccination (also comprising maternal vaccination), antibiotics and feed additives such as spray-dried plasma. It is concluded that provided highly efficient, relatively low-price immunoglobulin products are available, passive immunisation has a clear role in the modern animal production sector as a means of controlling infectious diseases, importantly with a very low risk of causing development of bacterial resistance, thus constituting a real and widely applicable alternative to antibiotics.

Protective effects of chicken egg yolk antibody (IgY) against experimental Vibrio splendidus infection in the sea cucumber (Apostichopus japonicus)

Vibrio splendidus is one of the most harmful pathogens associated with skin ulceration syndrome in the sea cucumber (Apostichopus japonicus) due to its high virulence and frequency of appearance. The objective of this study was to determine the effectiveness of chicken egg yolk antibody (IgY) against V. splendidus infection in the sea cucumber. Whole V. splendidus cells were used as an immunogen to immunize 20 White Leghorn hens (25 weeks old). IgY was produced from egg yolks obtained from these immunized hens using water dilution, two-step salt precipitation and ultrafiltration. The purity of the IgY produced was approximately 83%. Enzyme-linked Immunosorbent Assay indicated a high specificity for IgY with a maximum antibody titer of 320,000. The growth of V. splendidus in liquid medium was significantly inhibited by IgY in a dose-dependent manner at concentrations ranging from 1 to 10 mg/mL. The protective effects of IgY were evaluated in sea cucumber by intraperitoneally injecting anti-V. splendidus IgY antibodies (10 mg/mL) or immersing the sea cucumber in aqueous IgY (1 g/L) after an intraperitoneal injection of V. splendidus. Intraperitoneal injection resulted in an 80% survival while immersion resulted in a 75% survival during the 11-day experimental period. The survival rates were significantly higher than the positive control and the non-specific IgY group (P < 0.05). As well, the bacterial burden in the respiratory tree, intestine and coelomic liquid was significantly (P < 0.05) lower in sea cucumber treated with specific IgY than those treated with non-specific IgY. The phagocytosis of coelomocytes for V. splendidus in the presence of specific IgY was significantly (P < 0.05) higher than that obtained with non-specific IgY or without IgY, suggesting that specific IgY enhanced phagocytic activity. The current work suggests that specific IgY has potential for protecting sea cucumbers against V. splendidus infection.