Entry of the virion into the cell
Attachment of PPRV to the surface of the host cell
This is the first step. The infection starts when the viral H hemagglutinin recognizes a particular cell receptor protein. It is known under the acronym SLAM (Signalling Lymphocyte Activation Molecule), or CD150. It is expressed on the surface of lymphatic tissue lymphoid cells. This receptor appears to serve as a cellular anchor for all morbilliviruses, and explains their natural tropism for immune cells and the immunosuppression which results when these cells are destroyed en masse.
Fusion between the viral envelope and the cell membrane.
This is the second step. Once the H-SLAM link has been established, the second external viral protein (F) modifies its conformation and begins the fusion between the viral envelope and the cell membrane. The nucleocapsid is released into the cell cytoplasm where the infection cycle unfolds in two steps: transcription and replication.
Complement :
Scientists recently discovered that another protein, Nectin-4, serves as an epithelial cell receptor for morbilliviruses. Identified in upper respiratory tract epithelial cells of sheep, it explains the tissue lesions of the nose, mouth cavity, and trachea of infected animals.
