Induction of Endogenous Mammary Tumor Virus in Lymphocytes Infected with Murine Acquired Immunodeficiency Syndrome Virus

Mice infected with murine acquired immunodeficiency syndrome (MAIDS) virus developed lymphoadenopathy and profound immunodeficiency. Concomitantly the expression of endogenous mammary tumor virus (MTV) mRNA increased significantly, especially for the 1.7-kb 3′ open reading frame (ORF) mRNA encoding MTV superantigen. B cell lines that are established from MAIDS mice and exhibit superantigen activity also express a high level of 1.7-kb endogenous MTV and mRNA. Infection of a B cell tumor linein vitrowith retrovirus containing the cloned MAIDS virus gene induced superantigen activity and this cell line also expressed the 1.7-kb superantigen coding MTV 3′ ORF mRNA. These results strongly suggest a link between MAIDS virus infection and the induction of endogenous superantigen activity. This may play an important role in the pathogenesis of the MAIDS virus.