Microinjection of vesicular stomatitis virus ribonucleoprotein into animal cells yields infectious virus

Microinjection of purified transcriptionally active ribonucleoprotein (RNP) complex of vesicular stomatitis virus in vero cells resulted in the production and release of virus. Compared to the release of virus by cells treated with RNP in the presence of DEAE-dextran, the microinjection technique was highly efficient. Microinjection in Xenopus oocytes also resulted in initiation of infection as shown by the synthesis of virus-specific proteins in the cell cytoplasm. It was further observed that RNP stripped of L protein but containing residual NS protein was capable of initiating virus production or protein synthesis when microinjected in vero cells or in oocytes, respectively. Since L and NS proteins are essential for in vitro transcription by RNP, these results suggest that a trace amount of L protein may remain bound to the RNP and a host factor may stimulate residual L activity in vivo.