Topical immunization onto mouse skin using a microemulsion incorporated with an anthrax protective antigen protein-encoding plasmid.

The current anthrax vaccine in the U.S., the anthrax vaccine adsorbed, has several serious drawbacks, most notably the very lengthy and complicated dosing schedule. Thus, there is a critical need to develop an alternative anthrax vaccine with a simplified immunization schedule. To address this need, we evaluated the feasibility of topically priming or boosting onto the skin using an anthrax protective antigen (PA) protein-encoding DNA vaccine. To this end, we have shown that topical immunization of mice onto their skin with a perflubron-based microemulsion incorporated with a PA63-encoding plasmid, pGPA, led to significant PA-specific antibody responses, which have anthrax lethal toxin-neutralization activity. Moreover, topical boosting of mice primed with PA protein with the pGPA-incorporated, perflubron-based microemulsion significantly enhanced the anti-PA antibody responses induced. This topical anthrax DNA vaccine has the potential to be combined with a vaccine, such as the current AVA, to produce a simplified and more convenient dosing schedule.