IMMUNO-STIMULATORY EFFECTS OF BACTERIAL-DERIVED PLASMIDS DEPEND ON THE NATURE OF THE ANTIGEN IN INTRAMUSCULAR DNA INOCULATIONS

The CpG motifs of bacterial-derived plasmids augment antigen-specific immune responses and steer those responses towards the T helper 1 (Th1 ) type. In this study, we have addressed the immune-stimulatory effect of intramuscular co-administration of CpG motifs containing vector DN A. on the modulation of immune responses to the haemagglutinin (HA) an d the nucleoprotein (NP) proteins of influenza virus. The co-administr ation of Vector DNA with a HA-encoding plasmid DNA showed a significan t enhancement in the total IgG response, the generation of cytotoxic T lymphocyte (CTL), and the T-cell proliferative response. In the case of NP-encoding plasmid DNA inoculations, the co-administration of vect or DNA slightly decreased the total IgG response, although the IgG2a/I gG1 ratio and the CTL responses to NP were significantly increased. Th ese observations suggest that the immune-stimulatory effects of bacter ial-derived plasmids depend upon the nature of the co-administered ant igen.