A vaccine against anthrax that is more effective and easier to
administer than the present vaccine has proved highly effective in
tests in mice and guinea pigs, report University of Michigan Medical School
scientists in the August issue of Infection and Immunity.
The scientists were able to trigger a strong immune response
by treating the inside of the animals’ noses with a
“nanoemulsion” – a suspension of water,
soybean oil, alcohol and surfactant emulsified to create droplets of
only 200 to 300 nanometers in size. It would take about 265 of the
droplets lined up side by side to equal the width of a human hair.
The oil particles are small enough to ferry a key anthrax
protein inside the nasal membranes, allowing immune-system cells to
react to the protein and initiate a protective immune response. That
primes the immune system to promptly fight off infection when it
encounters the whole microbe.
Besides eliminating the need for needles, the nanoemulsion
anthrax vaccine has another advantage, the researchers say: It is easy
to store and use in places where refrigeration is not available.
An effective and easy-to-administer vaccine would be a
valuable tool for health authorities dealing with any future attack in
which a terrorist might spread anthrax microbes. The researchers say a
nasal nanoemulsion-based anthrax vaccine, if it proves effective in
humans, could be given easily to people even after they are exposed in
an anthrax attack, along with antibiotics. With some diseases, vaccines
given after exposure are used to boost the speed of the immune response.
“Anthrax spores can remain in the environment or
even in the lungs of exposed individuals for some time. Nasal
vaccination could be given to build up immunity after anthrax exposure
and improve the outcome of other treatments,” says Anna
Bielinska, Ph.D., the paper’s lead author and a scientist at
the Michigan Nanotechnology Institute for Medicine and Biological
Sciences at the U-M. She is also an assistant research professor in the
Allergy Division of Internal Medicine at the U-M Medical School.
In the 2001 attack in which anthrax spores were mailed to
members of Congress and reporters, some anthrax-exposed individuals
were given antibiotics but not the existing anthrax vaccine, because it
requires six injections over a period of six months and may cause
adverse reactions.
In the new study, the U-M team combined the nanoemulsion and a
recombinant protein of Bacillus anthracis to make the vaccine, which
they gave first to mice in either one or two applications. They found
the animals developed several types of effective immune response. The
vaccine produced both systemic and cellular immunity, meaning that the
body produces antibodies and primes specific cells throughout the body
to fend off anthrax infection. The vaccine also induced immunity on the
mucous membranes of the nose and lungs, where inhaled anthrax spores
enter the body and start a process that can cause illness and death.
“We saw protective immunity in the animals after
only two administrations rather than six,” says James R.
Baker, Jr., M.D., director of the Michigan Nanotechnology Institute for
Medicine and Biological Sciences and the senior author of the study. He
is the Ruth Dow Doan Professor in the Department of Internal Medicine
and chief of the Division of Allergy and Clinical Immunology in the U-M
Medical School.
After administering the vaccine, the researchers challenged
the immune systems of immunized guinea pigs with injections of 1,000
times the lethal dose of Bacillus anthracis spores. All the animals
survived, whereas none of the control animals did.
When the researchers delivered large doses of Bacillus
anthracis spores directly into the animals’ nasal tissue,
they found that 40 percent to 70 percent of the immunized animals
survived.
Because of the biosafety restrictions on the use of anthrax,
these challenge experiments were done at the Batelle Memorial Institute
and the University of Texas Medical Branch, which have labs federally
approved for handling the pathogen.
The experiments so far have shown that the vaccine had no
significant side effects and produced effective immunity for at least
six months. The Michigan Nanotechnology Institute will seek funding to
learn if the vaccine can produce immunity in primates as it does in
rodents. Safety studies in humans are also in the early planning stage.
Scientists at the U-M earlier developed the nanoemulsion
technique, which has been used to develop treatments for herpes and
toenail fungus. The Michigan Nanotechnology Institute for Medicine and
Biological Sciences was established at U-M in 2005 to develop and
market medical and biological applications of nanotechnology. Patent
applications for the nanoemulsion technology have been filed and
exclusively licensed to NanoBio Corporation, an Ann Arbor, Mich.-based
biotechnology company in which Baker has a financial interest.
Posted 17th August 2007
