DNA Vaccination in Chickens
Robust and sustainable development of poultry industry requires prevention of deadly infectious diseases. Vigorous vaccination of the birds is a routine practice; however, the live and inactivated vaccines that are used have inherent disadvantages. New-ge
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Introduction Proper health management of birds is very crucial for successful development of the poultry sector. A number of infectious diseases affect birds and cause a potential threat to the industry in the form of huge economic losses. Vaccination of the birds against the infectious diseases is widely followed; however, conventional vaccines have certain disadvantages [1]. With the advancement in the recombinant DNA technology, new-generation vaccines have emerged as a safer replacement to the conventional vaccines. DNA vaccines, which contain gene(s) encoding for one or more than one antigenic proteins, offer many advantages over conventional vaccines. In DNA vaccine, the expression of antigens in the target host resembles native pathogen epitopes more closely, and thus preserves the protein structure and antigenicity than the conventional vaccines [2–4]. Further, DNA vaccines are able to efficiently stimulate both humoral and cellular immune responses to protein antigens, and thus effective against a wide range of pathogens [5]. However, success of DNA vaccination in birds depends on many factors apart from their efficacy. They have to be relatively less expensive, easy to administer, and stable under field conditions. Moreover, as poultry are food animals as well, it is undesirable to have vaccine residues in the relevant tissues. This has been avoided by the use of subcutaneous or intradermal routes instead of intramuscular route [6]. The plasmid vectors are easy to construct and can be produced in large quantities quickly and affordably than conventional vaccines. In addition, only a small quantity (micrograms) of plasmid vector can deliver several antigens in a single shot, which provide immunity against many pathogens at once. All these factors significantly
Sunil Thomas (ed.), Vaccine Design: Methods and Protocols, Volume 2: Vaccines for Veterinary Diseases, Methods in Molecular Biology, vol. 1404, DOI 10.1007/978-1-4939-3389-1_11, © Springer Science+Business Media New York 2016
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reduce the expenses incurred by vaccination [7, 8]. The effectiveness of DNA vaccines can be further enhanced by the inclusion of the molecular adjuvants such as TLR (Toll-like receptor) ligands and cytokines. Notable examples of TLR ligands include CpG (TLR21) and flagellin (TLR5) and cytokines such as IL-12 and IFN-γ. A number of studies have reported upregulation of the immune response when TLR ligands and cytokines were given along with a DNA vaccine [3, 9–13]. 1.1 Advantages of DNA Vaccines
1. The production of DNA vaccine is easy, rapid, and economical as compared to conventional vaccines. 2. The DNA vaccine is more thermostable than traditional vaccines; hence, maintenance of a cold chain is not required. 3. It eliminates the risk of reversion of pathogenic phenotypes. 4. DNA vaccines present antigen to both MHC-I and MHC-II molecules. 5. The immune response elicited by DNA vaccine is directed against only the antigen of interest. 6. Cost-effectiveness and ease of development.
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