`Universal` vaccines could put brakes on flu evolution

Last Updated: Tuesday, February 28, 2012 - 12:03

Washington: “Universal” vaccines could allow for the effective, wide-scale prevention of flu by limiting the influenza virus` ability to spread and mutate, say researchers.

Universal, or cross-protective, vaccines — so named for their effectiveness against several flu strains — are being developed in various labs worldwide and some are already in clinical trials.

Princeton University-based researchers recently found that that the new vaccines would make a bout with influenza less severe, making it more difficult for the virus to spread.

At the same time, the vaccines would target relatively unchanging parts of the virus and hamper the virus’ notorious ability to evolve and evade immunity; current flu vaccines target the pathogen’s most adaptable components.

A computational model the team developed showed that these factors could achieve unprecedented control of the flu virus both seasonally and during outbreaks of highly contagious new strains. Cross-protective vaccines could even improve the effectiveness of current vaccines, which are designed to only fight specific flu strains, the researchers said.

Controlling the flu, which is now like “chasing a moving target,” could advance from the current reaction stage to that of real population-wide prevention, noted lead author Nimalan Arinaminpathy, a postdoctoral research associate in Princeton’s Department of Ecology and Evolutionary Biology.

“Because the flu quickly evolves to escape host immunity, current vaccines tend to be prioritized for inoculating specific high-risk groups such as asthma sufferers and the elderly every year,” Arinaminpathy said.

“So, at the moment, vaccine programs focus on clinical protection for those receiving the vaccine, but we hope to eventually graduate to being able to control the virus’ spread and even its evolution. Our model provides a strong conceptual basis as to how and why the ‘universal’ vaccines would achieve that,” he claimed.

Current flu vaccines are produced to counter the influenza strains that the World Health Organization predicts will dominate a particular flu season. Inoculation typically focuses on protecting people who are vulnerable to the virus. However, this approach does not provide long-term or widespread immunity, Arinaminpathy said. The flu virus is always evolving, and so vaccines need to be updated each year.

The reason is that these vaccines zero in on hemagglutinin (HA), proteins protruding from the virus`` surface that allow it to attach to and invade host cells. Small mutations in these highly adaptive appendages can create new versions of the virus that often are invulnerable to the vaccine designed for their former selves, a tactic known as “immune escape.”

Universal vaccines instead bypass the protruding HA surface to target more constant proteins with less evolutionary flair, Arinaminpathy said. Because HAs are still active, the virus may still infect people, but it cannot wreak the same havoc.

“We found that by putting the brakes on flu transmission, you could also put the brakes on flu evolution. Our model illustrates how we can control the flu this way, instead of simply reacting to it every few years,” Arinaminpathy said.

The study was recently published in the Proceedings of the National Academy of Sciences.

ANI



First Published: Tuesday, February 28, 2012 - 12:03

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