A consortium of researchers in the European Union have developed what they claim is the first vaccine against influenza strain H7N1, another bird flu that may be able jump the species barrier between poultry and humans. The vaccine is due to start clinical testing in the spring of 2006.

Most companies and research groups developing vaccines against a potential pandemic flu strain have focused on H5N1, a strain currently circulating in poultry and wild birds and tipped to be the most likely to undergo a mutation that would allow human-to-human transmission and cause a pandemic. But it is encouraging to see preliminary work on other flu viruses that could also pose a pandemic risk. Several companies such as Chiron, Sanofi-Aventis and GlaxoSmithKline are currently working on an H5N1 vaccine.

The researchers, funded by the European Commission under a project entitled Preparing for an influenza pandemic (FLUPAN) say that the H7N1 strain is highly pathogenic although the risk of it emerging as a pandemic strain is lower than the risk for H5N1. The FLUPAN project selected H7N1 because it was thought to be the most likely pandemic flu candidate when the project got underway in 2001.

H7N1 caused lethal outbreaks in Italian poultry in 1999 and was subsequently shown to be related to the 2003 H7N7 poultry virus in the Netherlands, which was responsible for over 80 human infections and one death.

Rapid production

However, the technology behind its production does have broader applications, according to the team.

They used a technique known as reverse genetics that does away with the need to produce vaccine antigens in fertilised chicken eggs – a cumbersome and lengthy process that is the primary reason why it can take several months to develop a flu vaccine after a circulating strain has been identified.

The technique involves taking isolated DNA from a flu strain and engineering it in the lab to make a virus particle that is non-pathogenic and – more importantly – make it amenable to being grown in cell culture. This could slash the time it takes to develop and make flu vaccine batches.

The team has also produced a serological test with that can be used to detect antibodies to H5 and H7 flu viruses, which will be useful in vaccine evaluation and surveillance testing to provide early warning of a pandemic.