Universal flu vaccine targets backbone of the virus
Getting an annual flu shot is never fun, and to add insult to injury, sometimes you'll get sick anyway. That's because it's hard to fight a virus that's always mutating, but new research out of Georgia State University is closing in on a universal vaccine. The study uses nanoparticles containing proteins that are common to all influenza A viruses.
If you look at a virus under a microscope, you'll see a ball with lots of tiny "stalks" poking out of it. These are proteins on its surface, and in the influenza virus it's known as hemagglutinin (HA). The proteins help the virus cling to the host's cells, particularly in the nose, throat and lungs, where it grows and spreads.
Flu vaccines contain inactivated virus particles made with the heads of these proteins. That alerts the immune system to what it should be watching out for, helping it to quickly fight off the virus if it ever detects those proteins again. And most of the time, that's an effective strategy.
Unfortunately, it's not foolproof. These protein heads are the parts of the virus that mutate the fastest, meaning there's a lot of variation between different species of influenza and even within a species year-to-year. The World Health Organization does its best to determine which strains are the most likely to take off in a given year, then pharmaceutical companies and research institutes around the world develop vaccines to target those. Of course, they don't always get it right.
"Vaccination is the most effective way to prevent deaths from influenza virus, but the virus changes very fast and you have to receive a new vaccination each year," says Bao-Zhong Wang, co-author of the study. "We're developing a universal influenza vaccine. You wouldn't need to change the vaccine type every year because it's universal and can protect against any influenza virus."
To provide wider protection, the researchers skipped the head of the proteins and aimed for the stalks instead. These sections don't mutate as drastically nor as often, making them a more effective target for the immune system to home in on. The team manufactured nanoparticles containing almost the entire protein that induces immune responses, and enclosed them in two layers to protect their function.
"This way you're protected against different viruses because all influenza viruses share this stalk domain," says Wang. "However, this stalk domain itself isn't stable, so we used a very special way to make this vaccine construct with the stalk domain and had success. We assembled this stalk domain into a protein nanoparticle as a vaccine. Once inside, the nanoparticle can protect this antigenic protein so it won't be degraded. Our immune cells have a good ability to take in this nanoparticle, so this nanoparticle is much, much better than a soluble protein to induce immune responses."
In mice tests, the researchers gave each animal two shots then exposed them to several flu strains, including H1N1, H3N2, H5N1 and H7N9. The vaccine worked to protect the mice from all strains, even at a lethal level of the virus, and significantly reduced the virus numbers found in the animals' lungs.
This study is just one of many universal flu vaccines currently in progress. Other strategies include DNA vaccines that target the virus on a genetic level, studying how the human immune system remembers which strains it's encountered before, and others that also target the protein stalks, including one that's currently undergoing human trials.
The research was published in the journal Nature Communications.
Source: Georgia State University