Stimulation of IgY responses in gene gun immunized laying hens by combined administration of vector DNA coding for the target antigen Botulinum toxin A1 and for avian cytokine adjuvants

Preparation of Anti-Rabies Virus N Protein IgYs by DNA Immunization of Hens Using Different Types of Adjuvants

DNA immunization has been used to study vaccination methods and for production of specific antibodies. The present study aimed to apply DNA immunization to prepare specific IgYs, which react against rabies virus N protein (RV-N) and can be used to research and diagnose rabies virus. The DNA sequence of RV-N was ligated into a pcDNA 3.1 plasmid for constructing pcDNA-N. Eight hens were divided into four groups. Group 1 comprised the control group (non-immunized). In Groups 2, 3, and 4, hens were injected intramuscularly with pcDNA-N (400 µg/hen). Eight injections were administered every other week. From the 4th week, an adjuvant was injected in addition to pcDNA-N. Freund's complete adjuvant (FCA) and λ-carrageenan were administered to Groups 3 and 4, respectively. Eggs were collected daily, and the specific antibody activities of egg yolks were measured by ELISA. IgYs were purified from pooled egg yolks at 16–19 weeks post-administration in each group. The detection sensitivities of the RV-N were compared using purified IgY as the primary antibody for ELISA, dot blotting, and western blotting. Egg yolks from one of the two hens in Group 2 (pcDNA-N alone) and all hens in Groups 3 (pcDNA-N + FCA) and 4 (pcDNA-N + λCarra) had increased ELISA values. The combined use of λ-carrageen in DNA immunization resulted in an adjuvant effect comparable to that of FCA. Each purified specific IgY detected RV-N in the ELISA, western blotting, and dot blotting; however, the detection sensitivity differed. Higher detection sensitivity of the +λCarra IgY was observed by ELISA, whereas there was higher detection sensitivity of +FCA IgY in western blotting and dot blotting. In summary, anti-rabies virus N protein IgY was prepared through DNA immunization of hens using FCA or λ-carrageenan as adjuvants and can be used as a primary antibody to detect rabies viruses.

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.

Stable Recombinant-Gene Expression from a Ligilactobacillus Live Bacterial Vector via Chromosomal Integration

Disease control in animal production systems requires constant vigilance. Historically, the application of in-feed antibiotics to control bacteria and improve performance has been a much-used approach to maintain animal health and welfare. However, the widespread use of in-feed antibiotics is thought to increase the risk of antibiotic resistance developing. Alternative methods to control disease and maintain productivity need to be developed. Live vaccination is useful in preventing colonization of mucosa-dwelling pathogens by inducing a mucosal immune response. Native poultry isolate Ligilactobacillus agilis La3 (previously Lactobacillus agilis) has been identified as a candidate for use as a live vector to deliver therapeutic proteins such as bacteriocins, phage endolysins, or vaccine antigens to the gastrointestinal tract of chickens. In this study, the complete genome sequence of L. agilis La3 was determined and transcriptome analysis was undertaken to identify highly expressed genes. Predicted promoter regions and ribosomal binding sites from constitutively expressed genes were used to construct recombinant protein expression cassettes. A series of double-crossover shuttle plasmids were constructed to facilitate rapid selectable integration of expression cassettes into the L agilis La3 chromosome via homologous recombination. Inserts showed 100% stable integration over 100 generations without selection. A positive relationship was found between protein expression levels and the predicted strength of the promoters. Using this system, stable chromosomal expression of a Clostridium perfringens antigen, rNetB, was demonstrated without selection. Finally, two recombinant strains, L agilis La3::P _eft -rnetB and L agilis La3::P _cwah -rnetB, were constructed and characterized, and they showed potential for future application as live vaccines in chickens.IMPORTANCE Therapeutic proteins such as antigens can be used to prevent infectious diseases in poultry. However, traditional vaccine delivery by intramuscular or subcutaneous injection generally has not proven effective for mucosa-dwelling microorganisms that live within the gastrointestinal tract. Utilizing live bacteria to deliver vaccine antigens directly to the gut immune system can overcome some of the limitations of conventional vaccination. In this work, Ligilactobacillus agilis La3, an especially effective gut colonizer, has been analyzed and engineered with modular and stable expression systems to produce recombinant proteins. To demonstrate the effectiveness of the system, expression of a vaccine antigen from poultry pathogen Clostridium perfringens was monitored over 100 generations without selection and found to be completely stable. This study demonstrates the development of genetic tools and novel constitutive expression systems and further development of L. agilis La3 as a live delivery vehicle for recombinant proteins.