Expression of infectious murine leukemia viruses by RAW264.7 cells, a potential complication for studies with a widely used mouse macrophage cell line

Abstract

The mouse macrophage-like cell line RAW264.7, the most commonly used mouse macrophage cell line in medical research, was originally reported to be free of replication-competent murine leukemia virus (MuLV) despite its origin in a tumor induced by Abelson MuLV containing Moloney MuLV as helper virus. As currently available, however, we find that it produces significant levels of ecotropic MuLV with the biologic features of the Moloney isolate and also MuLV of the polytropic or MCF class. Newborn mice developed lymphoma following inoculation with the MuLV mixture expressed by these cells. These findings should be considered in interpretation of increasingly widespread use of these cells for propagation of other viruses, studies of biological responses to virus infection and use in RNA interference and cell signalling studies.

Figure 1

MuLV p30 expressed by RAW264.7 cells in a formalin-fixed, paraffin-embedded cell pellet. (Avidin biotin IHC, ×1000).

Figure 2

MuLV p30 expression in spleen 8 weeks post injection of 264.7-MuLV, SC-1 prior to lymphoma development (IHC, hematoxylin, ×100).

Figure 3

MuLV p30 in splenic follicular B-cells and megakaryocytes in a mouse injected with 264.7-MuLV and that developed thymic lymphoma at 119 days (IHC, hematoxylin, ×200).

Figure 4

Thymic lymphoma induced by 264.7-MuLV, 164 days post injection. Note large spleen.

Figure 5

Thymic lymphoma in 264.7-MuLV infected mouse showing CD3⁺ lymphoma cells in lung metastases (IHC, hematoxylin, ×200).

Figure 6

PAX5 expression in bone marrow metastases of a B-cell lymphoma induced by RAW 264.7-MuLV (IHC, hematoxylin, ×100).