Failure to detect HTLV-I by in situ hybridization in the biopsied muscles of viral carriers with polymyositis.

Direct infection of muscle fibers by human T-lymphotropic virus type I (HTLV-I) has recently been reported in a patient with polymyositis infected with both HTLV-I and human immunodeficiency virus (HIV). Coinfections of these viruses are frequently found in the United States. In Kagoshima, Japan, patients with polymyositis have a significantly increased incidence of seropositivity to HTLV-I alone, when compared with the general population of Kagoshima. In this study, we examined muscle tissue from 6 HTLV-I-positive patients with polymyositis from Kagoshima. To detect HTLV-I products, sensitive immunohistochemistry and in situ hybridization analysis were performed. These were compared with muscle fibers from a well-characterized transgenic mouse model which expressed HTLV-I tax. No specific signals were detected in the biopsied muscles of patients with polymyositis infected with HTLV-I alone. HIV co-infection may, therefore, augment HTLV-I expression through either immunosuppression or direct viral interactions.