Researchers in the UK claim to have developed a new way of protecting against influenza that does not rely on the use of vaccines or antiviral drugs.
The team, led by Professor Nigel Dimmock at the University of Warwick, suggest that the approach could be effective regardless of the strain of flu encountered – including the bird flu strains such as H5N1 that are causing concern that a pandemic could be around the corner.
The concept relies on the use of a ‘protecting virus’ – a naturally-occurring form of the flu virus that has a broad swathe of its genetic material stripped out and is essentially dead. This deletion renders the virus harmless and prevents it from reproducing within cells. However, if an infective, ‘wild-type’ strain of influenza enters the cell, the protecting virus retains its harmless nature but subverts the missing machinery it needs from the invader in order to start reproducing rapidly.
This fast reproduction rate – spurred by the new flu infection – means that the new invading influenza is effectively crowded out, according to Dimmock.
The protecting virus provides instant protection, and completely prevents flu symptoms developing by slowing influenza infection rates to such an extent that the harmful infection becomes a vaccine against that very form of influenza. In theory, the low-grade reproduction of the invading virus could still be enough to prime the immune system against future exposure.
It can also provide protection if given early enough in the course of infection, say within the first 24 hours, he believes.
”One could give it as a preventive measure without the need to tailor it to a particular flu strain or mutation. This has obvious benefits when dealing with the sudden outbreak of a major epidemic, as one would not need to know the exact make up of the new strain before deploying the protecting virus making it much more useful than vaccines, which are effective only against particular existing strains of virus,” according to Dimmock.
Experiments so far show that a single dose of protecting virus can be given six weeks before an infection with flu virus and be effective. This could also have a substantial advantage over antiviral drugs such as Roche’s Tamiflu (oseltamivir) and GlaxoSmithKline’s Relenza (zanamivir) that give less than 24-hour protection.
A flu virus consists of eight individual segments of single stranded RNA. Dimmock’s protecting influenza virus has a huge but specific deletion of around 80% of the RNA of one of these strands. Delivery is simple, taking the form of an aqueous solution of the virus that is administered via an aerosol into the nose.
The Warwick research team has now filed a patent on the protecting virus and they are exploring ways of taking it through human clinical trials and testing on birds. The University has established a company – ViraBiotech – to commercialise the technology.
The lab experiments are virtually complete, and the next move will be to test it in humans, said Dimmock. The primary objective now is to obtain funding for the trials.