Structural and functional studies of the measles virus hemagglutinin: Identification of a novel site required for CD46 interaction

The entry of measles virus (MV) into human cells is mediated by the initial attachment of the viral hemagglutinin (HA) to the complement regulatory pr otein CD46. Two subdomains, one each within CD46 short consensus repeats (S CRs) 1 and 2, are responsible for this interaction. However, little is know n about the regions within MV HA needed for a high-affinity CD46 interactio n. To better define the HA-CD46 interaction, we took three approaches: chim eric domain swapping, peptide scanning, and alanine scanning mutagenesis. C himeras of MV HA and the closely related rinderpest virus (RPV) HA were gen erated and tested for cell surface expression and the ability to hemadsorb CD46+ red blood cells (RBC). Exchanges with the N terminus of RPV were tole rated as MV HA could be replaced with RPV HA up to amino-acid position 154. However, both larger swaps with RPV and a small RPV HA replacement at the C terminus aborted cell-surface expression. Peptide scanning with 51 overla pping peptides derived from three MV HA regions showed one peptide, corresp onding to MV HA amino acids 468-487, blocked hemagglutination of African gr een monkey (AGM) RBCs and inhibited MV infection of Chinese hamster ovary c ells (CHO) expressing human CD46. Alanine scanning mutants mapped sites on the MV HA that were not required for trafficking to the cell surface or fun ction in hemagglutination as well as a novel site required for CD46 interac tion, amino acids 473-477. (C) 1999 Academic Press.