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Updated: Jul 2, 2026
Intranasal Immunization and Milk Collection in Studies of Maternal Immunization in New Zealand White Rabbits (Oryctolagus cuniculus)
Published on: July 31, 2021
A single immunization with a dry powder anthrax vaccine protects rabbits against lethal aerosol challenge
S D Klas1, C R Petrie, S J Warwood
1LigoCyte Pharmaceuticals, Inc., 2155 Analysis Drive, Bozeman, MT 59718, United States. sheri.klas@ligocyte.com
Abstract:
Here we confirm that intranasal (IN) dry powder anthrax vaccine formulations are able to protect rabbits against aerosol challenge 9 weeks after a single immunization. The optimum dose of rPA in our dry powder anthrax vaccine formulation in rabbits was experimentally determined to be 150microg and therefore was chosen as the target dose for all subsequent experiments. Rabbits received a single dose of either 150microg rPA, 150microg rPA+150microg of a conjugated 10-mer peptide representing the Bacillus anthracis capsule (conj), or 150microg of conj alone. All dry powder formulations contained MPL and chitosan (ChiSys). Significant anti-rPA titers and anthrax lethal toxin neutralizing antibody (TNA) levels were seen with both rPA containing vaccines, although rPA-specific IgG and TNA levels were reduced in rabbits immunized with rPA plus conj. Nine weeks after immunization, rabbits were exposed to a mean aerosol challenge dose of 278 LD50 of Ames spores. Groups immunized with rPA or with rPA+conj had significant increases in survivor proportions compared to the negative control group by Logrank test (p=0.0001 and 0.003, respectively), and survival was not statistically different for the rPA and rPA+conj immunized groups (p=0.63). These data demonstrate that a single immunization with our dry powder anthrax vaccine can protect against a lethal aerosol spore challenge 9 weeks later.
Insights
A single intranasal dose of a dry powder anthrax vaccine protects rabbits against aerosolized Ames spores nine weeks later. This novel vaccine formulation shows promise for effective anthrax immunization.
Area of Science:
- Vaccinology
- Immunology
- Microbiology
Background:
- Anthrax remains a significant biodefense concern.
- Intranasal (IN) vaccine delivery offers potential advantages over traditional methods.
- Dry powder formulations enhance vaccine stability and ease of administration.
Purpose of the Study:
- To evaluate the efficacy of a single-dose IN dry powder anthrax vaccine in rabbits.
- To determine the protective potential against aerosolized Bacillus anthracis spores.
- To assess immune responses elicited by the vaccine formulation.
Main Methods:
- Rabbits were immunized with single IN doses of recombinant protective antigen (rPA) or rPA combined with a conjugated capsule peptide, with MPL and chitosan.
- Vaccinated rabbits were challenged 9 weeks post-immunization with aerosolized Ames spores.
- Humoral immune responses, including anti-rPA titers and toxin-neutralizing antibody (TNA) levels, were measured.
Main Results:
- Both rPA-containing vaccines induced significant anti-rPA titers and TNA levels.
- A single IN immunization with rPA or rPA+conj provided significant protection against lethal aerosol challenge (p=0.0001 and p=0.003).
- Survival rates were comparable between the rPA and rPA+conj groups, indicating robust protection.
Conclusions:
- A single intranasal immunization with the dry powder anthrax vaccine formulation confers significant protection against aerosolized anthrax spore challenge.
- The vaccine's efficacy is maintained up to 9 weeks post-immunization.
- This IN dry powder formulation represents a promising strategy for anthrax prophylaxis.
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