Effect of split low dose total body irradiation on SFFV mRNA, genomic DNA and protein expression in mice infected with the Friend virus complex.

DBA/2 mice infected with lethal dosages of Friend virus complex (FVC) can be 100% cured by split-dose total body irradiation (TBI) at 150 cGy, an effect associated with the restoration of the cellular immunity which is compromised by the virus. The exact mechanism underlying the curative effect is unknown, but it may involve the interferon (IFN) system and interleukin-2 (IL-2) production. Initial studies indicated that TBI did not directly inactivate the virus, suggesting that irradiation either acted on the target cells for virus replication or on other cells mediating the effect. We have now examined the effect of this relatively low dose TBI on replication, transcription, and protein expression of the Friend virus. Northern blot analysis revealed that in FVC infected mice treated with curative low dose TBI, no spleen focus-forming virus (SFFV)-specific mRNA species were detected. Southern blot analysis revealed that a 6.0 kb SFFV fragment could be detected in infected, untreated spleen cells, but not in cells from FVC-infected mice treated with TBI, or in uninfected spleen cells. Western blot analysis revealed that the SFFV envelope glycoprotein was expressed in the spleen cells from untreated FVC infected mice, but not in the cells from TBI treated FVC infected mice. These results, consistent with our previous findings of greatly reduced spleen focus forming units in mice with FVC which had been treated with this regimen of TBI, suggest the possibility of using such treatments in other retroviral associated disorders.