Characterization of VLPs carrying M RNA or M1 RNA. Cells were cotransfected with plasmids encoding N protein, L protein, M gene ORF, and antiviral-sense M RNA or M1 RNA. Intracellular proteins, intracellular RNAs, and VLPs were harvested at 3 d posttransfection and the released VLPs were purified by sucrose gradient centrifugation. (A) Intracellular proteins from mock-infected cells (lane 1), RVFV-infected cells (lane 2), cells expressing M RNA (lane 3), cells expressing M1 RNA (lane 4), purified VLPs from cells expressing M RNA (lane 5), and those from cells expressing M1 RNA (lane 6) were subjected to Western blot analysis using anti-RVFV mouse antibody. IC, intracellular samples. Gn/Gc, Gn/Gc proteins; NSs, NSs protein; and N, N protein. (B) RNA samples corresponding to the samples in A were subjected to Northern blot analysis using an RNA probe that hybridizes with viral-sense M or M1 RNA (lanes 1–6). Released VLPs carrying M RNA (lane 7) or M1 RNA (lane 8) were inoculated to cells coexpressing L and N proteins. Intracellular RNAs were extracted at 24 h postinoculation and subjected to Northern blot analysis.