DNA Immunization
Research Team & Collaborators
- Project leader: Sylvia van den Hurk
- Scientists: Philip Griebel
- Technicians: Zoe Lawman
- Post-doctoral fellows: Karl Robinson
- Graduate students: Sarah Mackenzie-Dyck, Tara Donovan
- Collaborator: Lorne Babiuk
Overview:
The concept of DNA immunization has been applied to induce immunity against numerous viruses as well as several bacteria and parasites. Immunization is accomplished by uptake and expression of purified plasmid DNA in host cells, where it persists extra-chromosomally in the nuclei. Subsequent expression of protein in the host cells results in the presentation of normally processed or modified forms of the protein to the immune system. The use of pure plasmid DNA offers many advantages over other delivery vehicles, most importantly the induction of a broad spectrum of immune responses, which is crucial for protection from many diseases. Furthermore, DNA vaccines can induce long-term immunity and are easy to produce, purify and manipulate. However, it has generally been more difficult to induce immune responses in large animals than in mice, the most frequently used model, which may be related to the low transfection efficiency following needle injection. Although the mechanism involved in the development of immune responses by DNA immunization is not completely understood, large animals also appear to have a more restricted responsiveness to CpG motifs, which play a role in the efficacy of a DNA vaccine.
Our current focus for DNA vaccines is bovine viral diarrhea virus (BVDV) because this virus is one of the most serious pathogens in cattle. Acute BVDV infections, caused by type 1 strains, are very common in cattle and result in mild disease of short duration characterized by fever, increased respiratory rate, diarrhea and a reduction in white blood cells. Although animals generally recover, the effect of BVDV on the immune cells reduces the host's resistance to disease and as such BVDV is an important pathogen in bovine respiratory disease. The recently identified type 2 strains can cause acute infections in herds that are characterized by high fever, hemorrhaging, diarrhea, reduction of white blood cells and platelets, and death.
Objectives:
- Develop delivery and formulation methods for DNA-based vaccines that will lead to enhanced and/or prolonged antigen production in large animal species.
- Formulate DNA-based vaccines with chemoattractants and immune modulators to recruit and/or activate dendritic cells at the vaccination site.
- Develop DNA vaccines for BVDV and additional bovine respiratory pathogens.
Progress:
We published one of the first reports of DNA vaccine efficacy in a large outbred animal species, demonstrating that a BHV-1 DNA vaccine can induce protective immunity in cattle and thereby establishing proof of principle for this technology in cattle.
To improve the transfection efficiency of plasmid in vaccinated animals, we recently used electroporation for delivery. Electroporation is a technology that creates temporary pores in cells, which improves DNA uptake into cells and can increase antigen production 10-100-fold. We demonstrated that compared to conventional intramuscular delivery, electroporation-based delivery markedly and consistently enhanced gene expression from a plasmid encoding a reporter gene, secreted alkaline phosphatase, and improved cell-mediated and humoral immune responses to a plasmid encoding hepatitis B surface antigen in cattle. The electroporation-based procedure was well tolerated by the calves, which did not need to be anesthetized or sedated. These results were confirmed in a vaccination-challenge trial for the BVDV E2 antigen, which showed complete protection by DNA immunization in combination with electroporation.
In order to further optimize entry of the plasmid into the nucleus, we are testing nuclear targeting sequences linked to a minimalistic (MIDGE) vector. We also have identified various compounds that offer many advantages over other delivery vehicles are chemoattractive for dendritic cells and thus can be evaluated for their ability to attract dendritic cells to the site of DNA vaccination, as an approach to enhance antigen
Future Direction:
DNA vaccines have shown promise as a therapeutic to break tolerance in a number of chronic diseases. In the future we plan to test DNA immunization as an approach to break tolerance in calves persistently infected with BVDV, which would not only be a huge benefit to producers, but also serve as model for other persistent infections, for example hepatitis C, as well as chronic diseases.
Furthermore, since DNA vaccines are promising against influenza and we have established this technology for pigs as well, we plan to evaluate DNA immunization against influenza in pig models. We also intend to optimize this technology for horses, in preparation for several potential applications.
Funding Partners:
- Alberta Beef Industry
- Alberta Livestock Industry Development Fund (ALIDF)
- Alberta Livestock and Meat Agency Ltd. (ALMA)
- Agriculture and Food Council of Alberta (AFC)
- Saskatchewan Agriculture Development Fund (ADF)
- BC Cattle Industry Development Council (CIDC)
Publications
- S. van Drunen Littel-van den Hurk, A. Luxembourg, B. Ellefsen, D. Wilson, A. Ubach, D. Hannaman, and J.V. van den Hurk. Electroporation-based DNA transfer enhances gene expression and immune responses to DNA vaccines in cattle. Vaccine 26(43): 5503-5509.
- Liang, R, van den Hurk, J.V., Landi, A., Deregt, D., Townsend, H., Babiuk, L.A. and van Drunen Littel- van den Hurk, S. 2008. DNA prime - Protein Boost Strategies Protect Cattle from Bovine Viral Diarrhoea Virus Type 2 Challenge. J. Gen. Virol. 89:453-66
