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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 3/30/2014 Publication Date: 4/28/2014 Citation: Suarez, D.L. 2014. Role of recombinant viral vectored vaccines for control of avian influenza viruses [abstract]. In: Proceedings of the 17th Annual Conference on Vaccine Research, April 28-30, 2014, Bethesda, Maryland. p. 62-63. Interpretive Summary: Technical Abstract: Both low pathogenic and highly pathogenic avian influenza viruses (AIV) can cause serious disease and disruptions of poultry markets around the world. Many different countries have used vaccination as a control tool for these diseases, but with varying affect. Vaccines when antigenically matched to the field strain and properly administered can provide good protection from clinical disease as well as reducing virus shedding in exposed birds and increasing the resistance of birds to infection(1). However, many impediments keep vaccination from being a completely effect control tool for the eradication of the virus in a region or country. Some of the main factors for suboptimal control is a poor antigenic match of the vaccine to field strain, maternal antibody suppressing the vaccine response, difficulty in properly administering the vaccine, and the presence of immunosuppressive viruses in poultry(2,3). The poultry industry has been at the forefront of developing recombinant viral vectored vaccines in an attempt to improve the immune response to vaccination. With AIV, the hemagglutinin surface glycoprotein is the key antigen for protection against infection. This allows a single gene to be transferred to viral vectors that allows protection for both viruses. The key advantages for the viral vectored viruses is the vaccines are administered as live viruses that provide both cellular and humoral immunity, and allows greater flexibility in administration of the vaccine. The safety profile of the recombinant vaccines are generally superior to traditional live attenuated vaccines(4). A key issue for poultry is the need to vaccinate chicks early because of the short production life of birds, particularly meat-type chickens which have a production life of only 6 weeks. Two of the more commonly used vaccines, the fowlpox recombinant and the herpes virus of turkey vaccines are designed to be administered at a day of age in the hatchery, which is a timely and cost effective approach for vaccination. These vaccines do provide good protection as early as three after vaccination in birds without maternal antibody. Unfortunately the vaccine response is delayed in birds with maternal antibody. The vectored vaccines do prime the immune response, and a common practice is to booster birds with a killed product at 2-3 weeks of age to greatly improve the immune response(5). Although the viral vectored vaccines have been shown to be good tools for the control of AIV, several factors have limited their effectiveness. The commercially available vectored vaccines are available with only a single hemagglutinin gene of one subtype, severely limiting how widely the vaccines can be used. Although the insert in the viral vector can be quickly changed, regulatory rules require these “new” vaccines to be separately licensed, which greatly adds to the cost of production. In addition, because these are genetically modified organisms, additional restrictions are imposed that make this class of vaccine unavailable in some countries. Regulatory changes are needed to fully benefit from this class of vaccines. |
