A study conducted by researchers at the University of Zurich has uncovered a second mechanism by which certain influenza viruses can enter human and animal cells. This discovery could have significant implications for understanding cross-species transmission and the potential for future pandemics.

Led by Professor Silke Stertz from the Institute of Medical Virology, the international research team found that in addition to the well-known method of entry via sialic acid binding, some human and avian influenza viruses can also infect cells through MHC class II protein complexes.

“Human influenza A viruses of subtype H2N2 and related H2N2 avian influenza viruses can enter cells through a second receptor, using an alternative entry pathway,” Stertz said.

The researchers found that hemagglutinin also binds to MHC class II protein complexes. These complexes on the surface of certain immune and respiratory cells are responsible for differentiating between the body’s own cells and foreign cells.

The study revealed that this dual infection capability was present in various species, including humans, pigs, ducks, swans, and chickens, but notably absent in bats. The researchers observed this phenomenon in both lab-grown cell lines and human airway cultures.

The risk that avian, swine and other animal influenza viruses could trigger a flu pandemic in humans may thus be greater than previously assumed. The ability to use MHC class II proteins for cell entry could have been one of the reasons why H2N2 influenza viruses emerged as a pandemic virus in Asia back in 1957. 

(With ANI inputs)