A new study published in Microorganisms (August 2025) by researchers from the University of Michigan, the U.S. Food and Drug Administration, and VLP Biotech, Inc., reports the successful development of a next-generation anthrax vaccine candidate designed to be more effective, stable, and easier to stockpile than current options.
The vaccine, a virus-like particle (VLP) platform displaying a key protective antigen epitope known as the loop-neutralizing determinant (LND), demonstrated strong immune responses in animal models after only one or two doses. Importantly, the candidate can be lyophilized (freeze-dried) and reconstituted without losing potency, addressing one of the most significant logistical challenges in biodefense vaccine preparedness—cold-chain storage and periodic stockpile replacement.
Why Anthrax Remains a Critical Threat
Although nearly 25 years have passed since anthrax spores were deliberately sent through the U.S. postal system, resulting in five deaths, inhalation anthrax remains a serious bioterrorism concern. Producing weapons-grade spores is relatively simple, and infection is highly lethal without prompt treatment. Current vaccines, such as BioThrax®, require multiple doses over 18 months plus annual boosters, often leading to compliance challenges. Moreover, these vaccines demand refrigerated storage and are prone to potency loss, necessitating costly replenishment of national stockpiles.
A New Vaccine Design: Epitope-Focused Nanoparticles
The new approach focuses on a cryptic neutralizing epitope (the LND) within Bacillus anthracis protective antigen. Unlike existing vaccines, which do not elicit antibodies to this region, the nanoparticle vaccine consistently produced highly protective antibody levels in rabbits and mice.
The LND-VLP vaccine uses the Woodchuck hepatitis core antigen capsid (WHcAg) to create a nanoparticle displaying 240 copies of the LND epitope. This structure mimics viral geometry, making it highly immunogenic but non-infectious. Key findings include:
- Rapid immune protection: Two doses, and in some cases a single dose, produced protective immunity.
- Cross-species validation: Rabbit antisera transferred into mice provided full protection from lethal aerosol anthrax spore challenge.
- Lyophilization advantage: Freeze-dried formulations retained structural integrity and immunogenicity, crucial for long-term, room-temperature stockpiling.
- Optimized delivery: A combination of subcutaneous and intramuscular administration improved immune responses.
Implications for National and Global Health Security
For the general public, anthrax may seem like a distant or unlikely danger. However, its potential as a bioweapon places anthrax preparedness squarely within the realm of national security and public health. A more potent, stable vaccine—one that does not require cold storage or frequent boosting—would significantly enhance readiness against deliberate release scenarios. Reduced logistical burdens mean faster deployment during crises and lower long-term costs for governments maintaining stockpiles.
Toward the Next Generation of Anthrax Countermeasures
While further testing in non-human primates and eventual human trials will be required, the study suggests that this LND-VLP vaccine could serve both as a standalone prophylactic and as a complement to existing protective antigen–based vaccines. The dual benefits of dose sparing and elimination of cold-chain dependence position it as a promising candidate for future inclusion in the U.S. Strategic National Stockpile and potentially in international biodefense arsenals.
As anthrax remains a “low-probability, high-consequence” threat, advances such as this provide a critical step toward ensuring societies are better prepared to respond to biological emergencies.
Oscherwitz J., Cease K., Milich D., et al. A Lyophilizable Nanoparticle Anthrax Vaccine Targeting the Loop-Neutralizing Determinant in Protective Antigen from Bacillus anthracis. Microorganisms, 12 August 2025.