A Step Toward a Universal Flu Vaccine
Researchers develop an influenza vaccine that offers protection to several flu strains in non-human primates.
Each year, we’re hit by flu season. Flu (or influenza) infections reach a peak during the winter months. Fever, runny nose, sore throat, aching muscles, coughing, we’ve all been there.
(This year has been a bit special with much fewer recorded cases. That’s because COVID-19 measures are effective against the spread of the flu as well. Social distancing, masks… All good preventative measures again respiratory viruses.)
Still, on average the flu costs between 300,000 and 650,000 lives per year, mostly in the 65+ age group.
Fortunately, we have flu vaccines.
But… we need new ones every year. Flu is a sneaky virus. It mutates rather rapidly, so the vaccines we use now, might be ‘outevolved’ by next year’s flu.
The reason for this is that flu viruses have two types of ‘spikes’ on their surface, hemagglutinin (HA) and neuraminidase (NA) proteins. Both these proteins accumulate changes over time via mutations (antigenic drift), but flu strains can also exchange these proteins (antigenic shift).
Basically, flu strains can mix-and-match their surface proteins to escape vaccines and become infectious.
These HA’s and NA’s are also used to give flu strains their name. For example, the 1977 Spanish flu is H1N1, the 2004 bird flu is H5N1, and so on.
No wonder that a universal flu vaccine is somewhat of a holy grail in infectious disease prevention.
One step closer
A new study now brings us one step closer to this holy grail.
The researchers developed a vaccine comprised out of headless hemagglutinin stabilized-stem immunogens (antigens that elicit an immune reaction) presented on ferritin nanoparticles. Together with adjuvant AF03, which boosts the efficacy of the vaccine, this elicited broadly neutralizing antibody responses in non-human primates.
Most H1 and H3 viruses could be thwarted by the antibodies produced in response to this new vaccine.
Pretty good news.
Of course, non-human primates are — obviously — not human, and the authors acknowledge this.
For example, to recognize antigens most human antibodies have a region called immunoglobulin heavy variable 1–69 (IGH1–69), which does not occur in the antibodies of other primates. These primates, though, have other gene families that could compensate for this.
This doesn’t mean that the vaccines won’t work, but it’s not yet a slam dunk. Still a great step forward, which warrants the scientists’ conclusion.
Antibodies elicited by these headless HA stabilized-stem vaccines neutralized diverse H1 and H3 influenza viruses and shared a mode of recognition analogous to human bnAbs, suggesting that these vaccines have the potential to confer broadly protective immunity against diverse viruses responsible for seasonal and pandemic influenza infections in humans.
The vaccine is now in clinical trials.