May 18 (HealthDay News) -- Vaccines made up of virus-like particles (VLPs) could provide stronger and longer-lasting protection against flu viruses than conventional vaccines, researchers say.
Even better, VLP vaccines, which can be grown in cell cultures or plants, can be developed and produced twice as quickly as conventional vaccines, according to research presented May 18 at the 109th General Meeting of the American Society for Microbiology, in Philadelphia.
In early clinical trials, VLP vaccines appear to provide complete protection against both the H5N1 avian influenza virus and the 1918 Spanish influenza virus, said Ted Ross, an assistant professor at the University of Pittsburgh's Center for Vaccine Research.
Adopting the new vaccine strategy may allow public health officials to respond more quickly to emerging influenza pandemics, according to a news release from the American Society for Microbiology.
"The sequence for the recent H1N1 'swine flu' virus was online and available to scientists long before physical samples could be delivered," Ross said in the news release. "It would have been possible to produce VLPs in quantity in as little as 12 weeks, while conventional vaccines require physical samples of the virus, and production can take approximately nine months."
Even without an actual sample of the agent, researchers can generate particles for a vaccine if the genes in the virus have been identified, Ross added.
Injectable vaccines that are currently in use to protect from the seasonal flu consist of three influenza strains that are grown in eggs and then inactivated using chemicals that break the virus up into pieces, according to background information provided in the news release. But because the pieces no longer look like the circulating virus, conventionally produced vaccines do not elicit as strong an immune response as VLPs.
"Virus-like particles look just like a live virus, but they are hollow shells without a genome inside, and they cannot reproduce," Ross said. "Because they look like the virus, they evoke a more robust immune response against the real thing."
Inhaled, mist-based flu vaccines can also elicit a strong immune response, but they are associated with an increased risk of side effects, because they are made with live, attenuated virus, the release noted.
Still, there is disagreement over who should be vaccinated and for what flu viruses, Ross said.
"There is a debate in the influenza community about priming the human population for potential pandemic strains such as H5N1 or 1918," Ross said. "Some researchers advocate adding these strains to the annual flu vaccine. They might not match the next pandemic flu strain exactly, but could provide some protection."
Others contend that it's premature and too costly to vaccinate people against a virus that may never emerge, he said.
SOURCE: American Society for Microbiology, news release, May 18, 2009