Introduction
A group of Indian scientists have developed a new vaccine
against anthrax. It is claimed to be superior over existing vaccines as it can
generate immune response to anthrax toxin as well as its spores rather than the
toxin alone.
Anthrax is a deadly human disease caused by bacterium
Bacillus anthracis that also infects animals like horses, sheep, cattle and
goats. Humans, pigs and dogs are comparatively less susceptible and only get
infected if exposed to copious amount of spores. In 2001, these spores were
used as agents of bio-terrorism when letters containing anthrax spores were
sent to some people in America, leading to widespread panic.
Spores of the bacterium that causes anthrax are present in
soil and can stay in latent form for years. However, under favourable
environmental conditions, they become active and start to infect. Often,
animals pick up spores while grazing, following which spores germinate in their
body and produce toxins.
The anti-anthrax vaccines available in market generate
immune response against a Bacillus protein-protective antigen – a protein that
helps in transport of bacillus toxins inside the cells. This means that immune
response is triggered only when spores germinate in body and start producing
bacterial proteins. Anyone vaccinated with such a vaccine would show no immune
response to bacillus spores and only perform once spores germinate and release
toxins.
Studies have, however, shown that when inactivated spores
are injected in addition to vaccine, the protection towards bacillus is
enhanced. Researchers from the Defence Research and Development Laboratory
(DRDL), Mysore and Jawaharlal Nehru University (JNU) decided to develop a
single vaccine which is effective against both the toxin and its spores so as
to provide complete protection.
For this, they stitched together portions of two genes:
protective antigen protein and protein present in outer layer of spore. The
protein thus produced was fusion of the two proteins and was injected into
mice. After few days, scientists found that injected mice had high
concentration of antibodies against fused proteins in its blood, showing immune
response against the injected protein. It was found that these antibodies were
also able to individually bind both protective antigen and spore protein
demonstrating that the vaccine can produce immune response against both spores
and the toxin.
“The ability of fused protein to generate protective immune
responses against both spores and toxin suggests it as an efficient vaccine
candidate against B. anthracis infection,” explained Joseph Kingston, a
scientist at DRDL, while speaking to India Science Wire.
While antibiotics are also available, vaccines for anthrax
are necessary as the infection can cause death within 2-3 days leaving no scope
for diagnosis and treatment.
While discussing the future directions, Rakesh Bhatnagar,
co-author of the study and a professor at JNU, said, “We intend to study
protective efficacy of this vaccine against Bacillus spores and toxins in higher
animal models.”
ACFS/ batch1
