Development and application of an ELISA for the detection of duck antibodies against Riemerella anatipestifer antigens in egg yolk of vaccinees and in serum of their offspring

Veterinary Autogenous Vaccines for Poultry in Europe-Many Ways to Crack an Egg

In the past decade, European animal farming has increasingly used autogenous vaccines for the prevention of nonnotifiable diseases. In Europe, these vaccines are exclusively inactivated bacterial and viral vaccines, with a set of specific regulations that differentiate them from conventional vaccines. The highest number of applications most likely occurs in poultry, as these animal species are farmed in the highest numbers compared with other types of food-producing animals. In 2019, autogenous vaccines came within the scope of harmonized European regulation for the first time, although many important aspects are still missing and need to be further developed. Consequently, several important legal provisions remain in national legislations and can vary tremendously between different member states of the European Union. The inclusion of autogenous vaccines in the management of certain diseases of poultry is justified by the nonavailability of licensed vaccines and the evolution and diversity of antigens in the field that are not covered by licensed vaccines. In addition, these vaccines aid in reducing the use of antibiotics. The methods for isolating and typing pathogenic isolates to obtain relevant antigens are pathogen specific and require a careful approach based on clinical evidence. Manufacturing processes are optimized according to regulatory standards, and they represent the most critical factor influencing the quality of autogenous vaccines and their placement on the market. This review presents the important requirements for manufacturing autogenous vaccines for poultry in addition to the relevant regulatory considerations. The results from a survey of several European Union member states regarding specific provisions within their national legislations are also presented.

Immunogenicity of live phoP gene deletion strain of Riemerella anatipestifer serotype 1

Duck infectious serositis is an acute and infectious disease caused by Riemerella anatipestifer (R. anatipestifer) that leads to perihepatitis, pericarditis, meningitis, and airbag inflammation in ducks, which causes serious economic losses to the global duck industry. The phoP/phoR is a novel 2-component signal transduction system first reported in gram-negative bacteria, of which phoP acts as a global regulator and virulence factor. In this study, the phoP gene from the R. anatipestifer YM strain was knocked out using homologous recombination technology and replaced with the spectinomycin resistance gene (Spec). The virulence of the R. anatipestifer YMΔphoP strain was reduced by approximately 47,000 times compared to that of the wild-type R. anatipestifer YM strain. Ducks were immunized with live R. anatipestifer YMΔphoP strain by subcutaneous inoculation at a dose of 10⁶ to 10⁷ CFU (0.2 mL per duck) and challenged with the wild-type R. anatipestifer YM strain 14 days later. The protection rate in the immunized group was 100%. The growth characteristics of ducks in the immunized and negative control groups were normal, and the research demonstrated R. anatipestifer YMΔphoP strain have suitable immunogenicity and protective effects. Thus, the study findings suggest that the novel R. anatipestifer YMΔphoP strain may provide a candidate for the development of a gene deletion activated vaccine against duck infectious serositis.

Development of a colloidal gold immunochromatographic strip for rapid detection of Riemerella anatipestifer in ducks

Riemerella anatipestifer is one of the major bacterial pathogens of ducks and causes significant economic losses in poultry agriculture. Usually, methods for detecting R. anatipestifer infection need specialized equipment and highly skilled personnel. In this study, a novel colloidal gold immunochromatographic strip was developed for rapid detection of R. anatipestifer in ducks. The monoclonal antibodies 2D5 and 2A6 against R. anatipestifer were used as colloidal gold-labeled protein and capture protein, respectively, to recognize the bacteria in tryptic soy broth medium culture and in hearts of infected ducks. The goat anti-mouse IgG antibody was labeled on nitrocellulose membrane as a control for C line. The labeling pH was optimized as 10.0, and the concentration of 2D5 labeled to colloidal gold particles was optimized as 18 μg/mL. The strip specifically detected serotypes 1, 2, and 10 R. anatipestifer strains and showed no cross-reaction with Escherichia coli, Salmonella enterica, and Pasteurella multocida strains. The sensitivity of the strip for detecting R. anatipestifer was 1.0 × 10⁶ colony forming unit. The strips remained stable for up to 8 mo at 4°C, and the detection can be completed within 15 min. The strip can detect R. anatipestifer in hearts of the ducks experimentally infected with R. anatipestifer but not infected with E. coli, which were also confirmed with bacterial isolation followed by multiplex polymerase chain reaction. These results suggested that the strips are reliable methods for identification of R. anatipestifer in laboratories and in duck farms.

Development of an in-house ELISA for detection of antibodies against Enterococcus cecorum in Pekin ducks

Enterococcus cecorum (EC) is known to cause skeletal lesions in broiler chickens and also systemic infections in Pekin ducks. Despite the importance of the pathogen, there is still a lack of serological diagnostic tools for the detection of EC infections. Here we describe the development of an in-house indirect enzyme-linked immunosorbent assay (ELISA) for the detection of EC-specific antibodies and its application by examination of 67 sera from experimentally infected Pekin ducks, 710 field samples from four Pekin duck breeder flocks previously vaccinated with inactivated vaccines, and 80 samples from commercial Pekin ducks coming from vaccinated parent flocks. All groups that had been experimentally inoculated via the air sac route were positive in the new ELISA, with significantly (P ≤ 0.05) increased mean sample/positive (S/P) ratios of 0.71-2.70 at days 7, 14 and 21 post-infection, while orally inoculated ducks and the EC-free control group remained negative with mean S/P ratios of 0.0-0.15. Antibodies were also detected in each of four vaccinated Pekin duck breeder flocks; 67.8% of the samples were antibody positive. The highest S/P ratios were found between 16 and 26 weeks (median S/P ratios from 0.15 to 1.03), but antibodies were still detected in some serum samples in weeks 61-67 post-hatch. No antibodies were detected in the commercial Pekin ducks. Antibody development in the ducks may be influenced by the composition of the inactivated vaccine. The new ELISA provides a useful tool for investigations of response to EC infections and vaccinations.

Effects of specific egg yolk immunoglobulin on pan-drug-resistant Acinetobacter baumannii

With the growing emergence of pan-drug-resistant Acinetobacter baumannii (PDR-Ab) strains in clinical, new strategies for the treatment of PDR-Ab infections are urgently needed. Egg yolk immunoglobulin (IgY) as a convenient and inexpensive antibody has been widely applied to the therapy of infectious diseases. The aim of this study was to produce IgY specific to PDR-Ab and investigate its antibacterial effects in vitro and in vivo. IgYs specific to two PDR-Ab strains were produced by immunizing hens with formaldehyde inactivated PDR-Ab cells and isolated from yolks with a purity of 90% by water dilution, salt precipitations and ultrafiltration. IgYs showed high titers when subjected to an ELISA and inhibited the growth of PDR-Ab in a dose-dependent manner in liquid medium. Scanning electron microscopy assay showed structural modification and aggregation of PDR-Ab treated with specific IgYs. Freshly cultured PDR-Ab cells were nasally inhaled in BALB/c mice to induce acute pneumonia. The infected mice were intraperitoneally injected with specific IgYs using cefoperazone/sulbactam and dexamethasone as positive controls. The IgYs specific to PDR-Ab lowered the mortality of mice with PDR-Ab-induced acute pneumonia, decreased the level of TNF-α and IL-1β in serum and reduced inflammation in lung tissue. Specific IgY has the potential to be used as a new therapeutic approach for the treatment of A. baumannii-induced infections.

Highly sensitive detection of cancer antigen human epidermal growth factor receptor 2 using novel chicken egg yolk immunoglobulin

Human epidermal growth factor receptor 2 (HER2) is an important biomarker that plays a crucial role in therapeutic decision-making for breast cancer patients. Ensuring the accuracy and reproducibility of HER2 assays by enzyme-linked immunosorbent assay (ELISA), western blot and immunohistochemistry (IHC) requires high sensitive and specific antibodies. Immunoglobulin Y (IgY) is a kind of avian antibody usually isolated from chicken egg yolks. Generation and use of IgY is of increasing interest in a wide variety of applications within the life sciences. In this study, IgY antibodies against two different truncated proteins of the extracellular domain (ECD) of human HER2 were produced, their sensitivity and specificity were evaluated. Specific IgYs were produced by hens immunized with the ECD proteins of human HER2 in long-standing immunization response and were isolated from yolks with a purity of 90% by water dilution, salt precipitations and ultrafiltration. The anti-HER2 IgYs were analytically validated for specificity by ELISA, western blot, immunocytochemistry and IHC. The IgYs bound desired targets in cells and fixed tissues and showed high affinity to HER2. The results demonstrated the viability of detection of HER2 with IgYs and showed promise for the using of IgYs in strict clinical validation.

Protective effect of an egg yolk-derived immunoglobulin (IgY) against Prevotella intermedia-mediated gingivitis

AIMS

To investigate the effects of an egg yolk-derived immunoglobulin (IgY) specific to Prevotella intermedia in vitro and in vivo.

METHODS AND RESULTS

An IgY specific to P. intermedia was produced by immunizing hens with formaldehyde-inactivated P. intermedia and showed high titres when subjected to an ELISA. The obtained IgY inhibited the growth of P. intermedia in a dose-dependent manner at concentrations from 1 to 20 mg ml(-1) in Center for Disease Control and Prevention liquid medium. Forty rats were challenged with P. intermedia on gingivae and then randomly divided into four groups, which were syringed respectively with phosphate-buffered saline, 1 mg ml(-1) of tinidazole, 20 mg ml(-1) of nonspecific IgY and 20 mg ml(-1) of the IgY specific to P. intermedia at a dosage of 300 μl per day. Gingival index (GI), plaque index (PI), bleeding on probing (BOP), counts of white blood cell (WBC) and histopathological slide of the gums were measured after treatment for 15 days. The gingivitis rats treated with the IgY specific to P. intermedia showed significantly decreased GI, PI, BOP and WBC (P < 0·05). Gum histopathology of the treated rats demonstrated a superior protective effect of the specific IgY on P. intermedia-mediated gingivitis.

CONCLUSIONS

A new immunoglobulin specific to P. intermedia was developed from egg yolk. This specific IgY can dose-dependently inhibit the growth of P. intermedia and protect rats from gingivitis induced by P. intermedia.

SIGNIFICANCE AND IMPACT OF THE STUDY

The new IgY has potential for the treatment of P. intermedia-mediated gingivitis.

Characterization of specific egg yolk immunoglobulin (IgY) against mastitis-causing Staphylococcus aureus

AIMS

To evaluate the in vitro activity of egg yolk immunoglobulin (IgY) against mastitis-causing Staphylococcus aureus.

METHODS AND RESULTS

Specific IgY was produced by immunizing hens with formaldehyde-killed Staph. aureus, using a bacterial strain known to cause mastitis. The IgY, of 94% purity, was obtained from yolks by water dilution, salt precipitations, ultrafiltration and gel filtration. ELISA indicated that the IgY produced was specific to the antigen and five Staph. aureus isolates obtained from mastitic cows. The growth of Staph. aureus was inhibited by specific IgY at concentrations from 1 to 10 mg ml(-1) in a dose-dependent manner. The phagocytosis of Staph. aureus by milk macrophages was enhanced in the presence of specific IgY with the highest phagocytic percentage being 30% higher than that without IgY (P < 0.05).

CONCLUSIONS

The specific IgY against mastitis-causing Staph. aureus inhibited the growth of Staph. aureus and enhanced the phagocytosis of Staph. aureus by milk macrophages.

SIGNIFICANCE AND IMPACT OF THE STUDY

Specific IgY would be a potential treatment for bovine mastitis.

A Coprological and Serological Survey for the Prevalence of Ascaridia spp. in Laying Hens

Ascaridia galli is a common nematode found in the intestine of domesticated chickens. The objectives of the study were to conduct a coprological and serological survey on the prevalence of ascaridiosis in laying hens of commercial farms. The farms recently adopted a breeding programme, where the hens have access to outdoor pens. Different amounts of Ascaridia eggs were detected in five of seven studied farms, while the other two farms were found to be free from the parasite. Serological tests revealed a seroprevalence of 21.8% (range 7.6-95%). No positive serum samples were detected in the same farms with previous negative coprological analysis. Western blot analyses confirmed the results obtained by the enzyme-linked immunosorbent assay (ELISA) test. In four experimentally infected hens, a progressive increase of the IgG antibody levels was observed, surpassing the cut-off point established for ELISA test 6 weeks post-infection. Serological tests are able to detect the infection before the eggs of the parasite appear in the faeces of infected hens, providing a useful tool to detect infections with Ascaridia spp. in avian farms.