doi.org
Defining the molecular interaction between influenza hemagglutinin and MHC-II
The hemagglutinin (HA) of some influenza viruses can interact with major histocompatibility complex class II (MHC-II), but how these proteins interact is unclear. Here we demonstrate that diverse H5 HAs can use MHC-II to enter cells, with avian MHC-II enabling more efficient entry than human MHC-II for most H5 HAs. To define the molecular interface, we use pseudovirus deep mutational scanning to measure how mutations to H5 HA affect its interaction with tufted duck MHC-II, and identify mutations that restrict HA to exclusively MHC-II or sialic acid receptors. We leverage identification of H5 HA mutations that increase binding to tufted duck MHC-II to determine a 4.8 Å cryo-EM model of the complex. To support the structural model, we measure how all mutations to tufted duck MHC-II affect its interaction with H5 HA, and find the alpha chain is the dominant determinant but beta chain sites near the peptide-binding groove also contribute. To generalize these findings, we use deep mutational scanning to show that a H7 HA interacts with MHC-II similarly to H5 HA. Finally, we show that H1, H2, H3, and H9 HAs interact with avian or human MHC-II, although interactions vary among strains that evolved in different hosts. ### Competing Interest Statement J.D.B. and B.D. are inventors on Fred Hutch licensed patents related to the pseudovirus deep mutational scanning and a provisional patent on MHC-II binding deficient HA vaccine antigens. J.D.B consults for Apriori Bio, GSK, Merck, and Pfizer. J.D.B. holds stock options in the Vaccine Company. N.P.K. is a paid consultant of AstraZeneca. National Institute of Allergy and Infectious Diseases, 75N93021C00015, U19AI181881 National Cancer Institute, P30CA015704 Washington Research Foundation, https://ror.org/00hasdx88, postdoctoral fellowship to Sara Sunshine Howard Hughes Medical Institute, https://ror.org/006w34k90
