Imugene soars on vaccine trial result

Shares in Sydney animal-health biopharma Imugene Limited (ASX:IMU) soared yesterday on news that animal trials have confirmed the efficacy of the company's new vaccine for controlling one of the international pig industry's most costly diseases.

Imugene has developed a vaccine against porcine reproductive and respiratory syndrome (PRSS), using its patented, CSIRO-developed adenoviral delivery vector system.

Imugene's ASX annoucement yesterday said a preliminary estimate was that an effective PRSS vaccine could achieve international revenues of US$100 million (AUD$137 million) a year. Those revenues could double or triple if the vaccine were used in a global campaign to eradicate PRSS from the pig industry.

The CSIRO spin-off's share price hit 28c yesterday, up from 21c, before settling back to 26c late in the day. Up to 3 million shares were traded, about 10 times the normal volume.

The Imugene vaccine has yet to be approved by international regulatory agencies such as the US Department of Agriculture, and special regulatory provisions will apply because the modified adenovirus, like others developed with Imugene's patented technology, is classified as a genetically modified organism (GMO).

However, the vaccine is inherently safe because it does not employ the intact virus -- only a single, isolated gene from the pathogen. The Australian company has stolen a march on rivals in the world's major pig-producing nations to develop a fully protective vaccine against PRSS.

According to Imugene, commercial vaccine developers in major pig-producing nations have been working intensively since the 1990s to develop an effective vaccine, but have had major problems using existing vaccine technologies.

Imugene MD Dr Warwick Lamb said the key protective antigen from the PRSS virus had been known for some time. It took Imugene only six months to develop a candidate vaccine using its adenovirus vector system, then another six months to conduct a series of four trials to prove its efficacy in pigs.

Imugene's patented adenoviral vector delivery system uses a harmless, non-infectious adenovirus as a 'plug-and-play' system to express genes coding for protective antigens that have been isolated from the target viruses.

The company recently announced it is working with AAHL researchers to develop an adenovirus-vectored vaccine to protect poultry against the deadly H5N1 strain of influenza -- the so-called bird flu that recently ravaged Asian poultry farms.

Once identified, the gene for the protective antigen is spliced into the adenovirus' genetic blueprint. The virus expresses the antigen, eliciting a protective response from the animal's immune system.

Lamb said that while Australian veterinary health authorities supported preventative vaccination for PRSS, there is currently no Australian market for the new vaccine because the disease does not occur in Australia.

For this reason, development and testing of the vaccine in pigs is to be carried out entirely under maximum-containment conditions at CSIRO's high-security Australian Animal Health Laboratory in Geelong.

Currently available vaccines for PRSS offer only limited protection, and the incidence of the disease is increasing. Its causes production losses estimated at between $US500 million and $US1 billion.

Although 'mystery swine disease' was first recognised in the US in the mid-1980s, virologists did not succeed in isolating and characterising the virus until 1991. It causes substantial economic losses in piggeries by rendering sows infertile, and increasing pre-weaning deaths and pneumonia in young, growing piglets. It also makes infected pigs more vulnerable to subsequent bacterial and viral respiratory infections, resulting in even greater losses.