Comparison of nucleic acid and protein immunization for induction of antibodies specific for HIV-1 gp120.

We have compared the antibody response to HIV-1 gp120 type LAI in mice immunized with either a gp120 expression plasmid or with baculovirus-derived recombinant gp120 (rgp120) formulated with Freund's complete adjuvant. TiterMax, Alum, Ribi R-700, AF-A or QuilA. DNA immunization resulted in variable levels of antibody, with endpoint titres ranging from 10(4) to 10(5), whereas mice immunized with rgp 120 mixed with Ribi R-700, AF-A or QuilA produced antibody levels with endpoint titres > 10(5). Both types of immunization failed to elicit antibodies able to recognize denatured rgp120. The V3 region was immunogenic in animals immunized with nucleic acid, whereas only a few animals immunized with recombinant protein produced antibodies specific for V3 or other linear epitopes, irrespective of the adjuvant used. These data suggest that the immunogenicity of gp120 is dependent upon the mode of antigen delivery, and that in vivo expressed gp120 following nucleic acid immunization elicits, at least with respect to V3, an antibody response which more closely reflects that seen following natural infection in man.