DNA immunization of mice with a plasmid encoding Neisseria gonorrhea PorB protein by intramuscular injection and epidermal particle bombardment.

Immunogenicity of a DNA vaccine encoding PorB from Neisseria gonorrhoeae strain FA1090 was analyzed in BALB/C mice immunized by intramuscular needle injection or epidermal gene gun bombardment. Both delivery routes generated measurable specific antibodies although the gene gun response was slower. Antibody isotypes were indicative of Th2 activation following gene gun immunization and of Th1 activation following intramuscular injection. In both immunization protocols, boosting with either renatured recombinant (rr) PorB protein or PorB expressed from Venezuelan equine encephalitis virus replicon particles (VRPs) significantly increased anti-PorB antibody levels. Boosting with rrPorB protein had little effect on antibody isotypes, while boosting with VRPs expressing PorB-enhanced a Th1 type response. Whole cell binding experiments showed that a portion of the antibodies recognized the surface of the homologous N. gonorrhoeae strain. Serum from groups with high antibody levels showed some opsonization of the homologous strain using human neutrophils. These results showed the potential of DNA vaccination for the purpose of priming an antibody response against PorB of N. gonorrhoeae. When combined with a protein or VRP boost, DNA priming resulted in high-titer and long-lasting responses. Based on different prime-boost protocols, we could polarize immune responses to predominantly Th1 or Th2, which should enable future studies of the types of immune responses that are protective in mouse models of gonorrhea.