Study identifies different cell-entry methods for two flu strains

An accidental observation during laboratory work showed that depleting a human protein called Rab11B prevented H3N2 viruses from entering lung cells while leaving H1N1 viruses unaffected. The study, published in The Journal of Virology, originally set out to track how viral RNA segments move inside cells.

Researchers used H1N2 and H3N2 strains isolated from nasal passages of patients who tested positive in 2022.

Key laboratory findings Data showed that H3N2 viruses failed to enter cells when Rab11B levels were reduced. H1N1 viruses continued to enter cells normally under the same conditions. Reverse-genetics experiments mapped the defect and identified a previously unknown role for Rab11B specific to H3N2 entry.

Implications for treatment research The results challenge the prior assumption that all influenza A viruses enter cells by the same mechanism. "We had previously thought that all flu viruses used the same way to get into a cell, but we discovered that this is not true," the principal investigator said.

The experiments were performed in isolated cells. Researchers stated that additional work is required to test whether blocking Rab11B is safe and effective in living respiratory systems and whether the dependency applies to all H3N2 strains or only currently circulating ones.