Retrovirus-induced murine acquired immunodeficiency syndrome: natural history of infection and differing susceptibility of inbred mouse strains.

C57BL mice (Fv-1b) develop a severe immunodeficiency disease following inoculation as adults with LP-BM5 murine leukemia virus (MuLV), a derivative of Duplan-Laterjet virus which contains B-tropic ecotropic and mink cell focus-inducing MuLVs and a putative defective genome which may be the proximal cause of disease. The stages of development of this disease were defined for C57BL mice on the basis of lymphadenopathy and splenomegaly; histopathological changes consistent with B-cell activation; and alterations in expression of cell surface antigens affected by proliferation of T cells, B cells, and macrophages. By using this disease profile as a standard, the response of adult mice of various inbred strains and selected F1 hybrids was compared. We show that although the strains which are highly sensitive are of the Fv-1b genotype (i.e., permissive for B-tropic MuLVs), certain Fv-1b strains, e.g., BALB/c and A/J, are resistant to murine acquired immunodeficiency syndrome, whereas certain Fv-1n strains (permissive for N-tropic MuLVs but restrictive for B-tropic MuLVs), notably P/N, BDP, and AKR, show moderate sensitivity and (C57BL/6 x CBA/N)F1 mice (Fv-1n/b and thus dually restrictive) are of relatively high susceptibility. The results of virus recovery tests suggest that apparently anomalous sensitivity, based on predicted Fv-1 restriction, may reflect MuLV induction and/or mutation to provide a helper virus for which the host is permissive.