Experimental flu vaccine shows protection against many strains

A research group including Frederick National Laboratory scientists has taken an early step toward a universal influenza vaccine that appears to protect against many strains, including the closely watched H5N1 bird flu. Human trials are under way. 

Conventional seasonal flu vaccines target the rapidly mutating head of the hemagglutinin (HA) protein on the virus particle, so the vaccine must be reformulated each year and made specific to the strain or strains in circulation.  

The experimental vaccine described in a recent issue of the journal Immunity targets the stem portion of the flu virus, which is relatively stable from year to year and common to many flu strains. 

The research group used two immune-provoking nanoparticles derived from the stem regions of group 1 and group 2 influenza A viruses to immunize three groups of animal models: mice, ferrets, and non-human primates. Each of the three groups was exposed to a cocktail of flu viruses. 

The experimental vaccine protected mice from multiple group 1 and group 2 viruses, and all animal models demonstrated broad immune responses overall. The scientists were particularly encouraged by the positive responses in non-human primates. Altogether, the results demonstrated a proof-of-concept for developing broadly protective flu vaccines. 

“The building block of our stem-nanoparticles is encoded by a single gene and its assembly is precise and efficient, making it a candidate for genetic vaccine delivery approaches, such as mRNA [used for COVID-19 vaccines] and recombinant viral vectors,” scientists reported. 

One limitation of the study is that it did not account for preexisting influenza immunity that is present in many people, having been exposed to multiple flu viruses over the years. But additional research is under way to shed light on this issue, including two phase 1 clinical trials to evaluate safety and immune response in human volunteers. 

The research report also noted concerns for pandemic preparedness and that even partially effective vaccines deployed early on could have a big impact on disease severity and viral transmission.  

“A vaccine that induces broad immunity against group 1 and group 2 influenza A viruses could be stockpiled and made available for deployment during the early stages of a pandemic before strain-matched vaccines can be developed and tested,” they wrote. 

Masaru Kanekiyo of the National Institute of Allergy and Infectious Diseases led the study group that included Yaroslav Tsybovsky and Tyler Stephens of the Frederick National Laboratory.