A LOW ONCOGENIC VARIANT OF FRIEND MURINE LEUKEMIA-VIRUS WITH STRONG IMMUNOSUPPRESSIVE PROPERTIES

Friend leukemia complex (FLC) is known to induce immunosuppression but the use of FLC in studies of immune cells function is disadvantageous since the immunosuppression always is accompanied by an acute erythro leukemia. To obtain immunosuppressive variants of FLC with reduced leu kemogenic potential, we isolated T-helper cells from FLC infected mice , and passed lysates of the cells to recipient uninfected mice. A grou p of these mice developed a condition distinct from the disease induce d by FLC. A viral stock prepared from these mice, designated Fd-MIV fo r friend derived murine immunodefiency virus, induced a profound suppr ession of the primary antibody response without acute transformation i n adult NMRI mice. Terminally a wasting disease with weight loss, atro phy of the thymus and lymph nodes and renal disease was observed in so me mice. Analysis of viral DNA and RNA from infected NIH 3T3 cells sho wed that Fd-MIV contained at least two viral components, a 8.4 kb frie nd murine leukemia virus (F-MuLV) and a 7.4 kb mink cell focus (MCF) / xenotropic virus related genome. The 7.4 kb genome was not detected in Fd-MIV infected, immunocompromised mice indicating that the 8.4 kb ge nome might be responsible for the disease.