PROTECTIVE EFFICACY OF A DENGUE-2 DNA VACCINE IN MICE AND THE EFFECT OF CPG IMMUNO-STIMULATORY MOTIFS ON ANTIBODY-RESPONSES

A recently described DNA vaccine for dengue (DEN) type 2 was shown to elicit high levels of neutralizing antibodies in mice. The vaccine can didate consists of the PreM and 92% of the envelope genes of DEN 2 New Guinea C strain. We further evaluated this DNA vaccine candidate by e xamining the effect of immune-stimulatory CpG DNA motifs on antibody r esponse and by studying the protective efficacy of the vaccine. The re sults showed that CpG motifs present in pUC 19 significantly improved the antibody response to a suboptimal dose of 3.1 mu g of the DEN DNA vaccine. In a lethal mouse intracerebral challenge model, the vaccine provided a significant level of protection. Sixty percent of the mice immunized with the DEN DNA vaccine plus pUC 19 survived the challenge compared to only 10% in the control group that received vector plus pU C These studies illustrate that nucleic acid immunization is a viable approach to developing a DEN vaccine and that immune-stimulatory CpG D NA motifs can be used to lower the minimum dose required to produce an antibody response.