Immunovaccine Inc. and Pfenex Inc. this week announced positive results from anthrax challenge studies in rabbits using Pfenex’s mutant recombinant Protective Antigen (mrPA) formulated with Immunovaccine’s DepoVax delivery system. The studies showed that animals administered a vaccine containing mrPA formulated in DepoVax were protected against a lethal anthrax challenge at a range of antigen doses.
The data demonstrated 100% protection against a lethal anthrax challenge in animals after vaccination with as little as 0.33 microgram of mutant recombinant Protective Antigen. Four out of five animals vaccinated with mrPA – DepoVax containing one tenth of a microgram of antigen were also protected.
A dose response was observed in the first 28 days following vaccination with higher amounts of mrPA formulated in DepoVax producing higher levels of neutralizing antibodies during this period. In rabbits immunized with a DepoVax vaccine, antibody titers generally plateaued within 28 days and persisted until at least day 70 when animals were exposed to the disease agent. The neutralizing titers measured on day 28 suggest that animals may be protected within one month of a single immunization.
Further studies will be designed to continue to evaluate the potential of DepoVax-based vaccines to offer rapid protection with a single dose.
“The positive data from this latest study highlight the potential for the DepoVax platform to enable rapid response vaccines to combat bioterrorism,” stated Dr. Marc Mansour, chief operating officer of Immunovaccine. “The ability to decrease the antigen content and still produce lasting protective antibody titers that protect from anthrax challenge following one vaccination potentially demonstrates the immune enhancing characteristics of DepoVax.”
“Pfenex is excited to be collaborating with Immunovaccine in pursuit of a stable, fast acting, dose sparing and antigen sparing vaccine candidate that will meet the needs of the US Federal Government,” stated Dr. Bert Liang, chief executive officer of Pfenex.
Previously reported rabbit and non-human primate studies suggested that DepoVax may enable a single dose rPA anthrax vaccine. It is now confirmed that a single dose of mrPA formulated in DepoVax is protective in the rabbit model. These studies, conducted under the National Institute of Allergy and Infectious Diseases’ (NIAID’s) preclinical services program (HHSN272201000022I/HHSN27200001), are intended to evaluate Immunovaccine’s DepoVax adjuvanting technology and advance the development of next generation bio-defense vaccines.