A Study of the Pseudotypes of Vesicular Stomatitis Virus and Murine Leukemia Viruses

Abstract

<p>Superinfection of murine leukemia virus infected cells with VSV produces a certain proportion of pseudotype particles which have the genome of VSV and envelope antigen characteristics of murine leukemia virus, i.e. these particles cannot be neutralized by anti-VSV antiserum. Pseudotypes of VSV and Friend murine leukemia virus have been neutralized by anti-FLV antiserum. These particles do not form plaques on the cells which are already infected with any of Friend-, Moloney-, Rauscher- or Gross murine leukemia viruses. This shows that this interference effect is an envelope mediated phenomenon which is common to all four of these murine leukemia viruses.</p> <p>At a high MOI of VSV infection the yield of VSV(FLV) pseudotype particles is reduced suggesting that this is due to direct inhibitory effect of VSV on FLV protein synthesis as well as on the host cell protein synthesis.</p> <p>Pseudotype particles have been shown to possess the same density and probably the same sedimentation coefficient values as normal VSV, but they have a tendency to form aggregates with non-pseudotype material more readily than do VSV(VSV) particles.</p> <p>In the studies of intracellular events involved in the synthesis of FLV specific glycoproteins, it has been shown that FLV glycoprotein is available for pseudotype production some 9 hours after FLV infection. The input FLV genome does not appear to act as a m-RNA for the glycoprotein in these experiments. Addition of actinomycin D after VSV superinfection does not reduce the yield of VSV (FLV) pseudotype synthesis significantly showing that concurrent DNA-dependent transcription is not needed for pseudotype formation. Effect of actinomycin D on pseudotype production in chronically infected FN-3T3 cells has shown that either the m-RNA or the glycoprotein itself is stable during 6 hour time prior to VSV infection.</p> <p>Experiments with glucosamine have shown that the majority of the FLV glycoprotein necessary for pseudotype production in chronically infected cells is synthesized after VSV infection.</p> <p>An interesting possibility that unintegrated "proviral" DNA may be capable of being transcribed and giving rise to FLV glycoprotein is suggested by experiments with ethidium bromide.</p>