Inefficient measles virus budding in murine L.CD46 fibroblasts

Infection of mouse L.CD46 fibroblasts with measles virus resulted in a poor virus yield, although no defects in the steps of virus binding, entry or f usion, were detected. Two days post-infection, the level of expression of t he viral F protein was found to be similar on the surface of infected L.CD4 6 and HeLa cells using a virus multiplicity enabling an equal number of cel ls to be infected. After immunofluorescence labelling and confocal microsco py, L.CD46 cells also displayed a significant increase in the co-localisati on of the N protein with the cell surface H and F proteins, Immunogold labe lling and transmission electron microscopy demonstrated the accumulation of numerous nucleocapsids near the plasma membrane of L.CD46 cells with littl e virus budding, in contrast to infected HeLa cells which displayed fewer c ortical nucleocapsids and more enveloped viral particles. Purified virus pa rticles from infected L.CD46 contained a reduced amount of H, F and M prote in. Altogether, these data indicate that, in L.CD46 cells, the late stage o f measles virus assembly is defective. This cellular model will be helpful for the identification of cellular factors controlling measles virus matura tion. (C) 1999 Academic Press.