licensing agreements are now almost certain considering their recent success.
"This is the first time a PRRS vaccine has been convincingly shown to be effective when administered orally to pigs. The commercial advantages for the pig production industry of a noninjectable vaccine against such an important disease are huge"
"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
Porcine Reproductive and Respiratory Syndrome (PRRS)
Introduction
The PRRS virus is viewed by many veterinarians as the most damaging disease affecting the worldwide pig industry causing losses of up to US$1 billion per annum. Initially recognised in the US in 1987, the disease spread rapidly to Europe in 1990 and subsequently across the rest of the world. Australia is one of three countries considered to be PRRS free. All the major pork producing markets throughout the world are affected with PRRS.
The disease is characterised by abortion, premature farrowing, stillborn and mummified piglets, respiratory disease. Economic losses are caused through death and chronic poor performance of nursing and weaned pigs.
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.
There is no current effective treatment or vaccine for the viral infection. Vaccines developed to date have suffered from either poor performance or safety problems. For 20 years there has been little success in economical and effective control of this highly variable viral disease.
Attempted control of PRRS on the farm using management processes have been tedious, labour intensive and have met with limited success.
There is a desperate need for an effective vaccine that is easy to administer, safe and where vaccinated pigs can be differentiated from infected pigs.
The new Imugene PRRS vaccine aims to meet these needs.
Imugene’s 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.
The vaccine has been demonstrated to protect pigs in early validation challenge trials conducted in 2004. Trials to further evaluate Imugene’s initial PRRS vaccines were completed at a specialist trial facility in the US in 2007. This latest trial tested three PAV based vaccine candidates and the best performing candidate was chosen to proceed in the product development program.
Imugene also became aware in 2007 of external scientific information which indicated that by modifying part of the existing PAV – PRRS vaccine and adding an additional component the result may be a significant improvement in vaccine efficacy. These identified changes involve genetic engineering and are ideally suited to the PAV vector based system of Imugene’s vaccine production.
The new ‘optimised’ vaccine that incorporates the chosen components from the most recent trial as well as these recently identified modifications has been developed and successfully laboratory tested. Efficacy challenge trials are now required and these are likely to be conducted in the US in 2008.
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. Imugene intends to strengthen its position in licensing negotiations by conducting the challenge trials with the recently constructed and optimized PAV PRRS vaccine.
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