Presence of human T-lymphotropic virus type II-related genes in DNA of peripheral leukocytes from patients with autoimmune thyroid diseases

No etiologic role of human T-lymphotropic virus type II (HTLV-II) in any disease is yet known. The present study showed a high incidence of HTLV-II proviral DNA fragments in DNA of peripheral blood leukocytes from patients with autoimmune thyroid diseases. Using primers for the pol and tax regions of HTLV-II proviral DNA, amplified DNA fragments were demonstrated in 51.5% of the patients with Hashimoto's thyroiditis and in 11.8% of those with Graves' disease examined, but in only 1.9% of the disease controls and 1.0% of healthy individuals. These amplified DNA fragments hybridized with each of the inner probes. The nucleotide sequences of the DNA fragments of the pol and tax regions showed high homology with those of the prototype of HTLV-II. No antibodies for HTLV-II could, however, be detected in the patients examined. Because of the absence of its antibody, HTLV-II infection was not confirmed in these patients, but the presence of HTLV-II proviral DNA or its related DNA at high frequency suggests a relationship of HTLV-II with the development of autoimmune thyroid diseases.