Immunization of the female genital tract with a DNA-based vaccine

Vaccines are being sought for contraception and the prevention of sexually transmitted diseases. However, progress is slow in this area largely because of lack of information on induction of protective immune responses in genital tract mucosa. In this study, we investigated whether in vivo transfection with a model DNA-based antigen delivered by gene gun technology would induce an antibody response detectable in vaginal secretions. Female rats were immunized with plasmids encoding human growth hormone (HGH) under the control of a cytomegalovirus promoter (pCMV/HGH) via vaginal mucosa (V), Peyer's patch (PP), and/or abdominal skin (S) routes. Localization of HGH in the target tissues demonstrated that all three sites can be transfected in vivo with pCMV/HGH. Vaginal tissues expressed roughly the same level of plasmid as skin. Antibodies to HGH were detectable in serum and vaginal secretions in rats immunized with pCMV/HGH. In the rats primed and boosted vaginally, vaginal immunoglobulin A (IgA) and IgG antibody titers to HGH were sustained for at least 14 weeks, whereas rats immunized via other routes and protocols (S/V, S/S, PP/PP, or PP/V) did not consistently sustain significant vaginal antibody titers beyond week 6. DNA-based immunizations administered by the gene gun may be an effective method of inducing local immunity in the female genital tract.