Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal, and it affects both humans and animals.
It can be prevented by vaccination, and the licensed anthrax vaccine is a toxoid vaccine. It consists of inactivated subunits of anthrax toxin and elicits an antibody response that neutralises anthrax toxin. These vaccines have been available since the 1950s.
Like many other members of the genus Bacillus, B. anthracis forms dormant endospores – often referred to as ‘spores’ for short, but not to be confused with fungal spores – that are able to survive in harsh conditions for decades or even centuries.
They can be found on all continents, even Antarctica. When they are inhaled or ingested, or when they come into contact with a skin lesion on a host, they may become reactivated and multiply rapidly.
Anthrax commonly infects wild and domesticated herbivorous mammals that ingest or inhale the spores while grazing – thought to be the most common route by which herbivores contract the disease. Carnivores living in the same environment may become infected by eating infected animals.
Diseased animals can spread anthrax to humans, either by direct contact – such as inoculation of infected blood to broken skin – or by humans eating a diseased animal’s flesh or being exposed to wool or leather.
The disease responds poorly to antibiotic treatment. Also, the early symptoms of anthrax disease are frequently non-specific and it is difficult to diagnose anthrax until it progresses to the later stages.
The fatality rate for anthrax caused by inhaling is estimated to be between 45% and 90%, even after using aggressive antibiotic treatment. Treating cutaneous and intestinal anthrax with antibiotics has a higher success rate. Vaccination after exposure is unlikely to be protective because of the delay between being exposed to the vaccine and developing immunity.
There are currently no World Health Organisation (WHO) International Standards for the diagnosis of anthrax and for anthrax vaccines. NIBSC staff drafted monograph 2188 of the European Pharmacopoeia ‘anthrax vaccine for human use (adsorbed, prepared from culture filtrates)’.
The toxins and enteric vaccines group is responsible for the batch release of anthrax vaccines for the UK. This involves reviewing batch manufacturing records to make sure the batch meets the specification of the vaccine’s marketing authorisation. As well as this, we submit each batch to a visual inspection, a safety test and an immunoassay to determine the amount of the active component – protective antigen.
This work is often carried out in collaboration with other divisions within NIBSC. We have analysed the proteome and gene transcription on a cellular level to identify relevant biological markers of intoxication in human cells exposed to anthrax toxin.
This information is used to improve our understanding of the protection generated by the immune response of experimental anthrax vaccines and by biologicals such as therapeutic monoclonal antibodies directed against subunits of the anthrax toxin.
A combination of these monoclonal antibodies with antibiotics may provide a treatment of anthrax after exposure.
Recently our R&D has been focusing on improving vaccine characterisation. We carry out experiments to: