Modulating specific priming of immune effector functions by DNA-based vaccination strategies

We have used the hepatitis B virus system in mice to investigate under which conditions the different DNA delivery techniques used in DNA vaccination introduce a T2 or T1 bias into the responses they elicit. Priming mice by an intramuscular injection of 100 microg plasmid DNA stimulated long-lasting T1 immune responses that included specific activation of potent MHC-1-restricted CTL responses. In contrast, priming mice with an intradermal injection of a low dose of plasmid DNA (0.1-1 microg/mouse) stimulated long-lasting T2 immune responses but no CTL responses. This polarization (spectrum of immune effector specificities) of immune responses elicited by plasmid DNA vaccines is determined by different factors, e.g. (i) the vaccination technique used; (ii) the age of the immunized animal; (iii) the condition of the local tissue environment to which DNA is delivered; (iv) the co delivery of immune-modulating factors; and (v) the type of antigen encoded by the plasmid DNA vaccine. DNA vaccination offers the possibility of constructing endogenous, chimaeric antigens with enhanced, hsp-facilitated expression, enhanced immunogenicity for B cells, and alternative, TAP-independent processing for MHC-1 restricted peptide presentation.