Vical Incorporated today announced conclusions from anthrax DNA vaccine studies in non-human primates reflecting data.
* DNA vaccines encoding protective antigen (PA) elicited protective immunity against lethal anthrax spore challenge that could not be predicted by post-vaccination antibody immune responses.
* Anthrax spore challenge resulted in more rapid and significantly higher anti-PA antibody responses and anthrax lethal toxin neutralizing antibody responses in DNA-vaccinated animals than in control animals.
* "Pseudochallenge" with anthrax antigen (recombinant PA vaccine) also resulted in more rapid and measurably higher anti-PA antibody responses and anthrax lethal toxin neutralizing antibody responses in DNA-vaccinated animals than in control animals.
Traditional immunoassays following DNA vaccination may not be sufficient to predict vaccine protective efficacy. The results of these studies suggest that the protective efficacy of DNA vaccines may be evaluable by measuring immune responses after a pseudochallenge with the same antigen that was encoded in the DNA vaccine rather than a challenge with the pathogen itself. This method may present a new pathway to evaluation of DNA vaccine efficacy. Financial support for the anthrax vaccine studies was provided under previously-announced grants from the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH). The recombinant PA vaccine was provided by VaxGen Inc.
