Structural basis of efficient contagion: measles variations on a theme by parainfluenza viruses

•The β-propeller head of the wild type measles virus hemagglutinin binds exclusively two tissue-specific receptors.•The signaling lymphocytic activation molecule (SLAM) and the epithelial receptor nectin-4 bind adjacent surfaces of the hemagglutinin head.•A mutated hydrophobic groove of the vaccine strain hemagglutinin binds the ubiquitous protein CD46, a decoy receptor.•Specificity domains added to the hemagglutinin can target viral entry to designated receptors expressed on cancer cells.

A quartet of attachment proteins and a trio of fusion protein subunits play the cell entry concert of parainfluenza viruses. While many of these viruses bind sialic acid to enter cells, wild type measles binds exclusively two tissue-specific proteins, the lymphatic receptor signaling lymphocytic activation molecule (SLAM), and the epithelial receptor nectin-4. SLAM binds near the stalk-head junction of the hemagglutinin. Nectin-4 binds a hydrophobic groove located between blades 4 and 5 of the hemagglutinin β-propeller head. The mutated vaccine strain hemagglutinin binds in addition the ubiquitous protein CD46, which explains attenuation. The measles virus entry concert has four movements. Andante misterioso: the virus takes over the immune system. Allegro con brio: it rapidly spreads in the upper airway's epithelia. 'Targeting' fugue: the versatile orchestra takes off. Presto furioso: the virus exits the host with thunder. Be careful: music is contagious.