415 Enhanced Immunogenicity to HIV-1 Envelope Using DNA Vaccines J. F. Bower*1, J. Sodroski2, T. Ross1 1East Carolina Univ, Sch of Med, Greenville, NC and 2Dana-Farber Cancer Inst, Boston, MA
Background: Recent studies suggest that HIV-1 envelope (Env) is a trimer on the native virus particle. In addition, it has been proposed that oligomeric/trimeric envelope vaccines may elicit better neutralizing antibodies because they more closely mimic the native conformation of gp160 Env. Two soluble, trimeric envelopes (gp140), each stabilized by different trimeric motifs: one from the GNC4 transcription factor and the other from bacteriophage T4 fibritin, have been shown to mimic the native oligomeric, transmembrane-bound gp160 Env. Both sequences are codon optimized for enhanced expression and have been shown to efficiently form and secrete trimers from cells. The proteolytic cleavage site, at the gp120/gp41 junction of each molecule, has been modified to prevent cleavage of the two subunits. In addition, the sgp140FT trimers have been shown to be more stable in vitro than the previously described sgp140GNC4 trimers.
Methods: DNA vaccines expressing trimeric forms of envelope (sgp140 delta683(-/GNC4) or sgp140 delta683(-/FT), as well as sgp140 only, were used to vaccinate BALB/c mice and were assessed for enhancement of immune responses using different inoculation regimens. Mice were primed with 2 mug DNA by gene gun at weeks 0 and 4, then subsequently boosted with either 2mug DNA or 10mug purified envelope intraperiotenially at week 8. Another set of mice were inoculated with 10mug purified envelope intraperiotenially at weeks 0, 4, and 8. Sera were collected every two weeks.
Results: Each DNA vaccine efficiently expressed and was secreted envelope. Sera, collected at 10 weeks were analyzed for anti-Env specific antibodies. Similar titers of total IgG anti-Env antibodies were observed in mice vaccinated with DNA expressing any of the envelope proteins, regardless of the regimen used to inoculate the mice (one-way ANOVA). In addition, the total anti-Env IgG antibody titers were similar in mice vaccinated with DNA or purified gp120 protein.
Conclusions: The results of this study show that DNA prime/DNA boost strategies using codon-optimized DNA vaccines expressing soluble, trimerized Env elicits similar, high levels of anti-Env antibodies as a DNA prime/ protein boost and protein only inoculations.