A recombinant measles vaccine virus expressing wild-type glycoproteins: Consequences for viral spread and cell tropism

Wild-type, lymphotropic strains of measles virus (MV) and tissue culture-ad apted MV vaccine strains possess different cell tropisms. This observation has led to attempts to identify the viral receptors and to characterize the functions of the MV glycoproteins. We have functionally analyzed the inter actions of MV hemagglutinin (H) and fusion (F) proteins of vaccine (Edmonst on) and wild-type (WTF) strains in different combinations in transfected ce lls. Cell-cell fusion occurs when both Edmonston F and H proteins are expre ssed in HeLa or Vero cells. The expression of WTF glycoproteins in HeLa cel ls did not result in syncytia, yet they fused efficiently with cells of lym phocytic origin. To further investigate the role of the MV glycoproteins in virus cell entry and also the role of other viral proteins in cell tropism , we generated recombinant vaccine MVs containing one or both glycoproteins from WTF. These viruses were viable and grew similarly in lymphocytic cell s. Recombinant viruses expressing the WTFH protein showed a restricted spre ad in HeLa cells but spread efficiently in Vero cells. Parental WTF remaine d restricted in both cell types. Therefore, not only differential receptor usage but also other cell-specific factors are important in determining MV cell tropism.