Most conventional vaccines are administered parenterally (e.g., by intramuscular (IM) or intradermal (ID) injection) and induce systemic but rarely mucosal immunity. Novel vaccination strategies capable of inducing both systemic and mucosal immune responses could greatly reduce infection and morbidity. One such strategy is DNA vaccination whereby the antigen is synthesized in vivo after direct introduction of its encoding sequences. In this thesis, we show that the route of administration of plasmid DNA encoding the hepatitis B surface antigen (HBsAg) influences the strength and nature of immune responses in mice and non-human primates. Mucosal immunization using plasmid DNA in saline results in no or weak immune responses. Formulation of DNA with lipid increases levels of reporter gene expression, but apparently not sufficiently to raise immune responses against expressed antigen indicating that other factors are involved. The strong immune responses induced after parenteral administration of DNA appears to be partly due to the adjuvant effect of unmethylated immunostimulatory CpG motifs present in the DNA backbone. Synthetic oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs (CpG) are potent adjuvants for induction of Th1-like systemic immune responses against parenterally-delivered proteins. Herein, the adjuvanticity of CpG ODN relative to or in combination with cholera toxin (CT), Escherichia coli heat-labile enterotoxin (LT), the B subunit of CT (CTB) and a non-toxic derivative of LT (LTK63) was evaluated with intranasal delivery. We also evaluate the potential of administering immunostimulatory complexes (comprised of HBsAg complexed with antibodies against HBsAg) by a mucosal route and determine whether immune responses are modulated by using CT or CpG as adjuvants. We demonstrate that CpG ODN, CT and LT augment anti-HBs titers equally, and this is more than with CTB or LTK63. CpG ODN acts synergistically with CT and LT but not CTB or LTK63, however for all combinations, CpG induces a more Th1-like response. The mucosal immune response induced is not restricted to the site of application but is also present at distant mucosal surfaces. These studies may lead to the development of novel human vaccines that protect at the level of entry for mucosal pathogens and may thereby prevent many infectious diseases.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/8772 |
| Date | January 1999 |
| Creators | McCluskie, Michael J. |
| Contributors | Davis, H., |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 304 p. |
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