Inhibition of vesicular stomatitis virus replication by adenosine

Attenuation of vesicular stomatitis virus infection of brain using antiviral drugs and an adeno-associated virus-interferon vector

Vesicular stomatitis virus (VSV) shows promise as a vaccine-vector and oncolytic virus. However, reports of neurotoxicity of VSV remain a concern. We compared 12 antiviral compounds to control infection of VSV-CT9-M51 and VSV-rp30 using murine and human brain cultures, and in vivo mouse models. Inhibition of replication, cytotoxicity and infectivity was strongest with ribavirin and IFN-α and to some extent with mycophenolic acid, chloroquine, and adenine 9-β-d-arabinofuranoside. To generate continuous IFN exposure, we made an adeno-associated virus vector expressing murine IFN; AAV-mIFN-β protected mouse brain cells from VSV, as did a combination of IFN, ribavirin and chloroquine. Intracranial AAV-mIFN-β protected the brain against VSV-CT9-M51. In SCID mice bearing human glioblastoma, AAV-mIFN-β moderately enhanced survival. VSV-CT9-M51 doubled median survival when administered after AAV-mIFN-β; some surviving mice showed complete tumor destruction. Together, these data suggest that AAV-IFN or IFN with ribavirin and chloroquine provide an optimal anti-virus combination against VSV in the brain.

Ultrastructural localization of L and NS enzyme subunits on vesicular stomatitis virus RNPs using gold sphere-staphylococcal protein A-monospecific IgG conjugates

Colloidal gold spheres were coated with staphylococcal protein A and were used to determine the location of NS and L proteins on vesicular stomatitis virus (VSV) ribonucleoprotein (RNP) complexes using monospecific anti-NS and anti-L IgG preparations. Conjugates using either anti-NS or anti-L demonstrated that these enzyme subunits were uniformly distributed along the entire length of the RNP complex. Under saturating conditions of IgG concentrations, it was observed that there were at least 60-70 molecules of NS protein and 30-35 molecules of L protein labeled per RNP complex.

The requirement of protein synthesis for VSV inhibition of host cell RNA synthesis

Published ultraviolet (uv) inactivation data and in vitro transcription studies have suggested that vesicular stomatitis virus (VSV) leader RNA was solely responsible for the inhibition of host cell RNA synthesis by this virus. Since no protein product is encoded in leader RNA, this conclusion implied that no protein synthesis should be required for this effect. Therefore, the inhibitory activity of VSV was examined in the presence of the protein synthesis inhibitors, cycloheximide, pactamycin, and emetine. Protein synthesis inhibitors are known not to interfere with VSV primary transcription, but in their presence viral replication and amplification of transcription do not take place. Although at 39 degrees the VSV mutant tsG22 could undergo only primary transcription, maximum inhibition of host cell RNA synthesis took place. However, in the presence of the protein synthesis inhibitors the VSV mutant was no longer able to interfere with host cell RNA synthesis. These results could not be explained by a change in the concentration of intracellular leader RNA which remained unaltered by the drugs. Similar results were also obtained with wild-type VSV in the presence of cycloheximide. Upon removal of the drug, inhibition of host cell RNA synthesis was reestablished in parallel with the restoration of protein synthesis. It is concluded that protein synthesis is required for the inhibitory activity of VSV, presumably because the active inhibitory complex is a nucleoprotein containing leader RNA and either a cellular protein or the viral N protein. The cellular protein would have to be in limiting supply since de novo protein synthesis was required for the inhibition to take place.

Activity of AMP against experimental herpes simplex virus type 1 infections in mice

Administration of AMP soon after inoculation of mice with herpes simplex virus type 1 inhibited development of virus-induced lesions and appeared to prevent establishment of virus latency. These effects were dependent on both the AMP dose and the time of AMP administration. Regression of herpes simplex virus type 1-induced lesions was also accelerated significantly by AMP treatment in a time- and dose-dependent manner.

Effect of intracellular vesicular stomatitis virus mRNA concentration on the inhibition of host cell protein synthesis

Inhibition of host cellular protein synthesis by vesicular stomatitis virus (VSV) has been suggested to be primarily the result of competition for ribosomes between cellular and viral mRNAs (H. F. Lodish and M. Porter, J. Virol., 36:719-733, 1980; Lodish and Porter, J. Virol. 38:504-517, 1981). This hypothesis was investigated by regulating the extent of VSV mRNA synthesis through the use of defective interfering particles. Although intracellular VSV mRNA concentrations decreased by as much as a factor of 14 at high multiplicities of infection of defective interfering particles, the inhibition of host cell protein synthesis by VSV decreased by a maximum of only 10%. The data also indicated that under these conditions the protein-synthesizing capacity of the cells was not exhausted. We concluded that competition for cellular ribosomes could not have been the major factor in the inhibition of host cell protein synthesis by VSV. This conclusion was further supported by inhibition data obtained with VSV mutants. The ts G22 mutant, defective in replication but not in primary transcription, inhibited host protein synthesis at the nonpermissive temperature (39 degrees C) to the same extent as did wild-type virus, even though it generated only 30 to 50% of the amount of viral mRNA as did wild-type virus. Conversely, in infections with the R1 mutant, which did not inhibit host cell protein synthesis, the amount of total and polysome-bound viral mRNA was indistinguishable from that obtained in infections by wild-type virus.

In vitro and in vivo inhibition of primary transcription of vesicular stomatitis virus by a defective interfering particle

A unique defective interfering (DI) particle, generated by a heat-resistant (HR) mutant of Indiana serotype vesicular stomatitis virus, was capable of inhibiting primary transcription by heterologous New Jersey serotype virions. The correlation between this phenomenon and the lowering of viral yields from doubly infected cells was investigated by the construction of chimeric DI particles containing the HR DI particle genome with a thermolabile polymerase. At the nonpermissive temperature, these DI particles were unable to self-transcribe, inhibit virion primary transcription, or reduce virion yield, but were able to be replicated. These results suggested that self-transcription of the HR DI particle genome was a prerequisite for heterotypic interference, but not for its own replication. Inhibition of virion primary transcription by HR DI ribonucleocapsids was also observed in vitro. At low HR DI to virion ribonucleocapsid ratios, the extent of inhibition was concentration dependent, whereas at high ratios, the amount of inhibition was concentration independent, approaching a limiting maximum value. A speculative mathematical model, which quantitatively accounts for these data, is presented. According to this model, the higher affinity for polymerase molecules by the HR DI ribonucleocapsids is explained in terms of dissociation events during transcription, which are more frequent in the longer virion ribonucleocapsids.

Effects of adenosine monophosphate on the reactivation of latent herpes simplex virus type 1 infections of mice

Adenosine monophosphate pretreatment of mice with latent herpes simplex virus type 1 infections significantly reduced the rate of reactivation of latent virus. Adenosine monophosphate pretreatment did not, however, eradicate latent virus.