Amino acid at position 95 of the matrix protein is a cytopathic determinant of rabies virus

The molecular mechanism involved in cytopathogenicity of rabies virus has not been fully elucidated yet. A fixed rabies virus Nishigahara strain does not induce clear cytopathic effect (CPE) in mouse neuroblastoma (NA) cells, whereas Ni-CE strain, which was established after 100 passages of Nishigahara strain in chicken embryo fibroblast cells, induces CPE that is characterized by rounding, shrinkage and detachment of the cells. In this study, to identify which viral gene is associated with the CPE of Ni-CE strain, we analyzed chimeric viruses between Nishigahara and Ni-CE strains generated by reverse genetics systems of both strains. We showed that the matrix gene of Ni-CE strain is responsible for the CPE in NA cells. It was also demonstrated by infection of Nishigahara and Ni-CE mutants with a single amino acid substitution in the matrix protein (M) that an amino acid at position 95 of M is a cytopathic determinant of the virus. We also demonstrated that the CPE is, at least partly, due to apoptosis. This is the first report of identification of an amino acid residue in a rabies virus protein that is important for the cytopathogenicity of the virus.