Immune history shapes protection against bird flu

Highly pathogenic avian influenza H5N1 clade 2.3.4.4b, commonly called bird flu, has spilled over from birds into dairy cattle and other mammals, including cats and humans. This rapid spread has made identifying and understanding the immune factors that may confer protection increasingly urgent. A study led by Stacey Schultz-Cherry, PhD,  Department of Host-Microbe Interactions, identified short amino acid sequences within viral antigens that are recognized by T cells and trigger immune responses to bird flu (a technique called T-cell epitope mapping). They found that preexisting immunity from H1N1 (the common seasonal influenza A virus), whether it was from previous infection or vaccination, protects against lethal cow- and cat-derived H5N1 viruses. Protection was linked to cross-reactive antibodies and conserved memory T-cell responses shared across influenza strains. 

The findings were published in the Journal of Virology and suggest that immune history should be considered in future risk assessment and vaccine evaluation strategies. 

“We found that having an immune history from either prior seasonal flu infection or vaccination can provide protection against emerging highly pathogenic H5N1 viruses, even in the absence of neutralizing antibodies to the virus,” said first author Pamela Brigleb, PhD, Department of Host-Microbe Interactions. “This points to additional correlates of protection against emerging flu strains and suggests that future vaccines should be evaluated beyond generation of neutralizing antibody responses alone.”

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