Mapping Amino Acid Mutations on Structures using Protein Imager
tutorial
Elgin Akin 
Antigenic Sites
Influenza B Hemagglutinin (HA)
PDB: 4FQM B/Brisbane/60/2008 Influenza Hemagglutinin Starting Motif DRICT (D=residue #1 in the numbering schema)
120 loop 150 loop 160 loop 190 helix 240 loop
H1N1
Sa Sb Ca1 Ca2 Cb
H3N2
Site A Site B Site C Site D Site E
Ref: https://www.nature.com/articles/s41467-020-15102-5
Additional Reading
https://pmc.ncbi.nlm.nih.gov/articles/PMC4229193/ - Burke universal numbering schema