Safety and immunogenicity of Px563L, a recombinant anthrax vaccine candidate, in a two-dose regimen for post-exposure prophylaxis in healthy adults

Serological correlates of protection and long-term efficacy of a novel recombinant protective antigen-based anthrax vaccine in a rabbit model

The novel anthrax vaccine candidate GC1109, composed of recombinant protective antigen, has shown robust antibody responses and safety in preclinical and clinical studies. However, the assessment of GC1109 vaccine efficacy was limited in a rodent model and could not be applied in clinical studies due to ethical issues. In this study, we aim to provide predictive insights for human applications of GC1109 by examining the correlation between anthrax toxin-neutralizing antibodies (TNAs) and protection against Bacillus anthracis infection in rabbit. The threshold level of TNAs necessary for protection was assessed following subcutaneous (s.c) challenge with lethal B. anthracis spores. In addition, the longevity of immunity in GC1109-vaccinated rabbits was investigated. A positive correlation between TNA levels and survival was observed, indicating their potential as a predictor of protection in humans. The 50 % neutralization factor (NF50) value of 0.5 was associated with a 70 % probability of survival, establishing this value as a surrogate marker for protective efficacy. Long-term protection was confirmed, with the GC1109-vaccinated group exhibiting significantly higher survival rates (91.7 %) than the control group (8.3 %) at 12 months post-vaccination. These findings highlight the protective efficacy and durability of GC1109-induced immunity against lethal B. anthracis challenge. The study supports the continued development of GC1109 as a viable anthrax vaccine candidate and underscores its potential for emergency preparedness in Korea.

Anthrax: A narrative review

Bacillus anthracis is a zoonotic bacterium, majorly responsible for causing human anthrax and the possibility of the outbreak spreading globally. Herbivorous animals serve as the inherent reservoir for the disease, whereas all endothermic species are vulnerable. Humans contract the disease inadvertently by contact with diseased animals or animal products or through the consumption or handling of infected flesh. There is no such reported data indicating the transmission of anthrax from human to human, which further does not guarantee the bacterium's mutations and new transmission route. Nevertheless, it can lead to various infections, including endophthalmitis, bacteremia, cutaneous infection, central nervous system infection, and pneumonia. Therefore, it is crucial to examine the present epidemiological situation of human anthrax in densely populated nations, including the altered symptoms, indications in people, and the method of transmission. This article highlights the current diagnostic methods for human anthrax, further examines the available therapy options and future perspectives in treatment protocol. This narrative review resulted from a simple search strategy on "PubMed", "ScienceDirect", "ClinicalTrials.gov" and web reports using "AND" as Boolean operator with search keywords, i.e., "Anthrax" AND "Infection", "Anthrax" AND "Pandemic", "Anthrax" AND "Infectious disease", "Anthrax" AND "Vaccine", "Anthrax" AND "Diagnosis" shows minimal narrative literature in between 2024 and 2005. Furthermore, this narrative review highlights the potential approaches for detecting anthrax infection, establishing suitable protocols for prevention, and focusing on the current epidemiology and available therapeutics, vaccine and its future developmental strategies for the prevention of infectious disorder.

Recent Advancements and Novel Approaches Contributing to the Present Arsenal of Prophylaxis and Treatment Strategies Against Category A Bacterial Biothreat Agents

Bacterial pathogens have always been a part of the ecosystem in which we thrive. Some pathogens have caused deadly outbreaks in the past and have been exploited as an agent of threat. Natural hotspots for these biological pathogens are widely distributed throughout the world and hence they remain clinically important. Technological advancement and change in general lifestyle has driven the evolution of these pathogens into more virulent and resistant variants. There has been a growing concern over the development of multidrug-resistant bacterial strains that could be used as bioweapons. This rapid change in pathogens also propels the field of science to develop and innovate new strategies and methodologies which are superior and safer to the existing ones. Some bacterial agents like-Bacillus anthracis, Yersinia pestis, Francisella tularensis and toxins produced by strains of Clostridium botulinum, have been segregated as Category A substances as they pose imminent threat to public health with a history of life threatening and catastrophic disease. This review highlights some encouraging developments and value additions in the current plan of action for protection against these select biothreat bacterial pathogens.