prrs vaccine trial in progress

ASX ANNOUNCEMENT
4 July 2008
Imugene’s PRRS vaccine for pigs enters further trials
USA based commercial efficacy trial commenced
4 July 2008, Sydney, Australia: Trials to evaluate Imugene’s revised and optimised
PRRS vaccine have commenced at a specialist pig trial facility in the USA.
PRRS is a highly damaging viral respiratory and reproductive disease in pigs for which there are
no effective treatments.
This trial is evaluating an optimised vaccine candidate using components selected
from previous Imugene PRRS vaccine trials. The optimised vaccine has undergone a
series of modifications and improvements aimed at increasing its effectiveness and
commercial value.
In 2007, three Imugene PRRS vaccine candidates were trialled and the best
performing candidate was selected as the base for a new improved vaccine to
proceed in the product development program. This improved vaccine candidate has
now successfully been modified and fully laboratory tested. This work was recently
completed and sufficient material exported to the USA trial site. The initial vaccination
administration of the 45 pigs has also now occurred. A second dose will be
administered prior to exposing the pigs to the PRRS virus.
The animal trial will take approximately 6 weeks with preliminary results anticipated
within 4-6 weeks following completion of the live animal phase.
Imugene managing director Dr Warwick Lamb said, “We anticipate that the
optimisation and modifications that have been made to the vaccine will deliver
commercial levels of protection. The PRRS disease is an increasing economic
problem for the major pig producers worldwide.”
The vaccine is based on Imugene’s Porcine Adenoviral Delivery Vector that delivers
selected genetic material to the pig to stimulate the immune system to protect against
the PRRS virus.
PRRS is one of the most economically damaging pig diseases worldwide causing
industry losses of up to $1 billion each year. Initially recognised in the US in 1987 the
disease spread to Europe in 1990 and subsequently across most of the rest of the
world. Australia is one of three countries considered PRRS-free.


PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME (PRRS)
Disease
PRRS also known as mystery swine disease or blue ear disease is characterised by
abortion, premature farrowing, stillborn and mummified piglets, respiratory disease
with loss by death and chronic poor performance of nursing and weaned pigs.
PRRS is recognised as the biggest problem disease in the worldwide swine industry.
For over 20 years there has been little success in economical and effective control of
this highly variable viral disease.
The virus of PRRS has a particular affinity for the macrophages particularly those
found in the lung. Macrophages are part of the body defences. They ingest and
remove invading bacteria and viruses. Those present in the lung are called alveolar
macrophages. In contrast to most other bacteria and viruses, macrophages do not
destroy the PRRS virus. Instead, the virus multiplies inside them and then kills the
macrophages. Up to 40% of the macrophages are destroyed. This removes a major
part of the body’s defence mechanism and allows bacteria and other viruses to
proliferate and cause more damage.
Imugene’s PRRS vector based vaccine
The Imugene PRRS vaccine is based on the Porcine Adenoviral Delivery Vector that
delivers selected genetic PRRS material to the pig to stimulate the immune system to
protect against the PRRS virus.
Three versions of the Imugene vaccine constructs were successfully challenge trialled
last year and since that time development has concentrated on upgrading the best
performing vaccine. Modifications were made to the vaccine based on new external
scientific information which indicated that by altering part of the existing vaccine and
adding an additional component the result may be a significant improvement in
vaccine efficacy. These changes involved genetic engineering and are ideally suited
to the vector based system of vaccine production.
Commercial proposition
PRRS is one of the most economically damaging diseases of pigs worldwide causing
estimated annual industry losses over US$1 billion. In the US alone PRRS is
estimated to cost US$550-750 million annually to pork producers. There is no effective
treatment for the viral infection. Vaccines have been developed but are either
ineffective or suffer safety issues. Farm management procedures have been
implemented but the disease persists.
Imugene has been in discussion with several large animal health companies about
licensing opportunities for the global registration, manufacture and sales of the PRRS
vaccine. Positive results from the current trial will strengthen Imugene’s position in
these licensing negotiations.