Murine acquired immunodeficiency syndrome (MAIDS) induced by defective LP-BM5 murine leukemia virus is a disease which shares many similarities to human AIDS. The pathogenesis of MAIDS is currently not understood, but may involve the consequential effect of stroma infection in the bone marrow resulting in a defective hematopoietic microenvironment. To evaluate the effect of infection on the hematopoietic stroma, we generated permanent stromal cell lines for LP-BM5 infected and non-infected cell lines was confirmed by the expression of defective viral gag p12 sequence via RT-PCR and the production of viral particles. The ability of these cell lines to support in vitro hematopoiesis was studied. Results indicated that when co-cultured with either non-infected or infected nonadherent mononuclear cells, non-infected control cell lines efficiently supported the production of hematopoietic precursors, whereas viral-infected cell lines induced suppression of both non-infected and viral-infected progenitors. Expression of several cytokine genes in stromal cell lines was also determined by RT-PCR. All cell lines expressed equivalent levels of transcripts for stem cell factor, IL-3, IL-7 and TNFa. However, infection was associated with higher levels of IL-4 and TGFβ1 mRNA expression. These findings suggest that LP-BM5 infection of stromal cells leads to defective hematopoietic support function and altered cytokine expression. Further characterization of the defective cell lines should prove valuable for studies of the pathogenesis of murine AIDS.