Bone marrow transplantation from Fv-4-resistant donors rescues Friend leukemia virus-infected mice from leukemia: a model of bone marrow transplantation therapy against retroviral infection.

Bone marrow transplantation experiments were conducted in mice in order to develop an experimental bone marrow transplantation therapy model, with which to investigate possible means to cure retrovirus-infected hosts with bone marrow or stem cells from virus-resistant donors. In one experiment, lethally irradiated Friend leukemia virus (FLV)-sensitive C3H/He (C3H; Fv-2s, Fv-4s, Rfv-1s, Rfv-2s Rfv-3s) mice were transplanted with (i) bone marrow cells from FLV-resistant BALB/c-Fv-4Wr (C4W; Fv-2s, Fv-4r, Rfv-1s, Rfv-2s, Rfv-3s) mice (C4W --> C3H) or (ii) a mixture of bone marrow cells from C4W and C3H mice (C4W + C3H --> C3H). They were then inoculated with FLV 3-4 months later and leukemia development was examined. The results indicated that C4W --> C3H chimeras were completely resistant to FLV-induced leukemogenesis and that C4W + C3H --> C3H mixed chimeras that contained as low as 30% C4W-derived cells, or as high as 70% C3H-derived cells, did not develop leukemias. In another experiment, bone marrow cells from C57BL/6 (B6; Fv-2r, Fv-4s, Rfv-1r, Rfv-2r, Rfv-3r) or C4W donors were grated to FLV-sensitive DBA/2 mice (DBA; Fv-2s, Fv-4s, Rfv-1s, Rfv-2s, Rfv-3s) that had been infected with FLV 6 days earlier (DBA-FLV). The results indicated that most, if not all, FLV-infected DBA mice which received bone marrow transplantation from B6 donors developed B6-derived leukemias, although the survival time of these mice was dramatically prolonged as compared to that of untreated DBA-FLV mice. In contrast, bone marrow transplantation from Fv-4r-bearing C4W donors successfully rescued FLV-infected DBA mice from leukemic deaths. Thus, the bone marrow transplantation therapy against retroviral infection of hemopoietic cells was shown to be feasible, provided that donor cells carry a resistant allele that functions via receptor blockade as in the case of Fv-4r, but less effective when the roles of the resistant alleles partially interfered with the virus replication, leukemic transformation and/or cycling of target cells as suggested for Fv-2r gene action, or to resist virus infection by immunological means as are known for Rfv-1r, Rfv-2r and Rfv-3r genes which are also carried by B6-strain mice. Implication of these findings on the somatic gene therapy against retrovirus infection diseases in man are discussed.