The matrix (M) protein of the virus causes many of the cytopathic effects of VSV, including an inhibition of host gene expression and the induction of cell rounding.

It is thought that the activation of apoptotic pathways causes the inhibition of host gene expression and cell rounding by M protein.

[1] These proteins play a major role in assembly and budding of VSIV virions.

This inhibits interferon signaling and thus establishment of antiviral state in virus infected cells.

In turn, this induces cell-rounding, cytoskeleton disorganization and apoptosis in infected cell.