By Emily Leclerc
BU News Service
BOSTON — Scientists have embarked on the hunt for a universal flu vaccine, but it is proving to be a more difficult task than anticipated. While the idea is noble, the influenza virus is complicated in ways that other viruses are not.
“The universal vaccine idea has been around for quite some time,” said Dr. Seema Lakdawala, an assistant professor at the University of Pittsburgh department of microbiology and molecular genetics. “The idea is that a universal flu vaccine will allow for immunity against a lot of different strains.”
The flu virus is remarkably unstable in comparison to viruses for which we have lifelong vaccines. It has a high mutation rate that is rooted in how the virus copies its genetic material.
“In the flu, in particular, the machinery that copies the genome is not faithful. It makes a lot of mistakes which causes the high rate of mutation,” said Dr. Marta Gaglia, a professor of molecular biology and microbiology at Tufts University.
The constant accumulation of mutations causes the flu strains genetic composition to shift from year to year. That shift in genetic makeup causes the variety of different flu strains, which makes it difficult to create a universal vaccine.
Some may wonder how scientists can create a long-lasting vaccine for a virus that is ever-changing, but there is an approach currently being investigated by the National Institutes of Health that involves the two proteins used to classify the flu virus.
“Flu viruses are classified by two proteins on the outer surface of the virus: hemagglutinin (H) and neuraminidase (N),” according to the NIH. This is where the names for the different strains come from, like H1N1, for example. The letters are the two different proteins and the number indicates which subtype the protein is. The key is that every single strain of the flu contains a variation of the H and N protein.
The NIH is looking to create a universal flu vaccine by targeting what is called the stem region of the hemagglutinin (H) protein.
“So this H protein, I like to tell my students, is like a lollipop,” Lakdawala said. “You’ve got Dum Dums and you’ve got blow pops and you’ve got tootsie pops and other kinds of lollipops. There are ranges of what the head of the lollipop looks like, but the stick looks exactly the same. So, the idea is to target that stick.”
This approach holds promise in providing protection to a broad range of flu strains because every virus, regardless of mutations, has the same stem. Even so, this idea presents problems, Lakdawala suggested.
“It’s not easy to make an antibody against the stick because it’s so easy to see the head of the lollipop. Our immune system does see the stick though because it’s there when we get infected with the flu so it does elicit some immunity,” Lakdawala said.
The issue is that the amount of antibodies needed against the stick to neutralize the virus is more than the amount needed against the head, she said.
To be able to create a long-lasting flu vaccine using this method, scientists need to figure out how to effectively target the stem of the H protein in a way that will elicit a large enough immune response to provide adequate long-lasting protection, Lakdawala explained.
This research is still in its infancy. There is a lot left to unravel before a universal flu vaccine is introduced to the market, but there are strides being made.
“The NIH has recently been pushing research initiatives to improve the vaccine,” Gaglia said. The NIH is hoping to revamp current vaccines while funding research into a universal one.
Even so, the final product of a universal flu shot probably won’t be what most people imagine.
“A universal vaccine likely won’t mean you get it once and that’s it,” Gaglia said. “It would most likely look more like a shot you get every three years instead of every year.”
