Genetically engineered bird flu vaccines tested
Eggs for vaccine production may be in short supply during a pandemic |
Genetically engineered avian influenza vaccines have been successfully tested in mice and poultry by two teams of scientists in the US. The
results were published online on 2 February in The Lancet and in the February issue of the Journal
of Virology (2006;80:1959).
Current H5N1 vaccines depend on a supply of embryonated eggs to produce
inactivated sub-virion vaccines. Since availability of eggs during a
pandemic would be limited and, according to the researchers, approximately
four billion embryonated eggs would be needed to produce vaccine for
the estimated 1.2 billion people that could be affected by the virus,
researchers are developing egg-independent strategies to combat bird
flu.
Mary Hoelscher of the Centres for Disease Control and Prevention, Atlanta,
Georgia, and colleagues genetically engineered a human adenovirus to
produce a protein called haemagglutinin subtype 5 — a component
of the H5N1 virus isolated from humans in Hong Kong. One group of mice
was injected with the vaccine and the other was injected with saline.
The researchers found that immunised mice were protected from death,
weight loss and primary viral replication when infected with H5N1. They
explain that the adenovirus-vector-based vaccine generated specific T-cells
as well as antibodies, whereas current vaccines work by activating cellular
immunity alone.
The researchers said that the vaccine also has the advantage of conferring
cross-protection against continuously evolving H5N1 viruses without the
need for an adjuvant. The vaccine can be grown to high titres and would
therefore
be suitable for stockpiling, they said. “This approach is a feasible
vaccine strategy against existing and newly emerging viruses of highly
pathogenic avian influenza to prepare against a potential pandemic,” they
concluded.
The paper published in the Journal of Virology details research undertaken
by Andrea Gambotto, University of Pittsburgh School of Medicine, Pennsylvania,
and colleagues who developed a similar vaccine against haemagglutinin
protein isolated during the outbreak of avian influenza in Vietnam. The
researchers tested their vaccine in mice and then in chickens (subcutaneously
and intranasally). The vaccine administered subcutaneously completely
protected chickens from the virus, which was lethal to unvaccinated chickens
within two days.
The researchers say that they achieved vaccine production within 36 days
of acquiring the virus sequence, which would be useful if the virus were
to begin to mutate rapidly. The group is planning a small trial in humans
in the near future. |
The
Pharmaceutical Journal
Acrobat
Reader