Exposure to acidic pH causes irreversible conformational changes in the measles virus hemagglutinin.

Temporary exposure to acidic pH caused the hemagglutinin (H) protein of measles virus to lose hemagglutinating activity and undergo antigenic changes. The antigenic changes, detected as alterations in reactivity of several anti-H protein monoclonal antibodies, were characterised by ELISA and radioimmune precipitation assay. The possible biological instances of such conformational changes within the paramyxovirus H protein are discussed.