Herpes simplex virus type 2 and pseudorabies virus associated growth factors and their role in the latency in vitro

A putative herpes simplex virus type 2 (HSV-2) growth factor (HSGF-2) was detected in a crude extract from virus infected mouse embryo cells. This factor, similar to previously described pseudorabies virus (PRV) associated growth factor (PRGF) was shown to have ability to morphologically transform non-transformed cells and to repress the transformed phenotype of transformed cells. Both activities could be neutralized with two, out of seven monoclonal antibodies directed against glycoprotein B of HSV-2. Both PRGF and HSGF-2 were detected in human embryo lung cells latently infected with PRV or HSV-2 either at 41 degrees C, or in the presence of phosphonoacetic acid. Human alpha-2 interferon, when present in medium of latently infected cells enhanced the production of both HSGF and PRGF. On the contrary, when latently infected cells were treated with 5-azacytidine the synthesis of both PRGF and HSGF-2 was completely blocked and the virus reactivated from latency replicated to higher titers than in non-treated cells. The role of PRGF and HSGF-2 in the establishment, maintenance and reactivation of latency, as well as in cellular transformation is discussed.