RNA tumor virus in human thymomas and thymus hyperplasias

Abstract

Human thymomas and thymus hyperplasias were examined for retroviruses. Most of these patients were complicated by systemic immunological diseases such as myasthenia gravis and pure red cell aplasia. The thymus cells were co-cultured with allogenic B cells or peripheral blood lymphocytes (PBL) pretreated with mitomycin C. Retrovirus-like particles were demonstrated in cultured thymus cells in all cases of thymomas and thymus hyperplasias examined by electron microscopy. In most cases, these particles were detected in thymus epithelial cells. Reverse transcriptase activity sedimenting at a density of 1.15-1.17 gm/cm3 in sucrose density gradients was eluted in the culture fluids. Retrovirus-like particles were demonstrated in human T cells infected with these particles. Antibodies to virus-infected T cells were detected in sera of the patients with thymoma and thymus hyperplasia. These results suggest that in thymomas and thymus hyperplasias, retroviruses that can be induced, following a proliferative stimulus, may be involved in the genesis of thymic disorders and in the pathogenesis of systemic immunological diseases.

Viral infection in thymoma and thymic tumors with autoimmune diseases

“…According to Ono et al, retrovirus‐like particles were detected in cultured thymus cells of all thymoma tissues using electron microscopy and reverse transcriptase activity assay. Thus, the putative lytic infection of retroviruses may have engaged in the occurrence of thymic disorder like thymoma in humans 28 . Furthermore, there have been studies demonstrating the presence of West nile virus (WNV), human polyomavirus 7 (HPyV7) and human parvovirus B19 (B19V) in thymoma or thymic hyperplasia 29–31 .…”

“…Thus, the putative lytic infection of retroviruses may have engaged in the occurrence of thymic disorder like thymoma in humans. 28 Furthermore, there have been studies demonstrating the presence of West nile virus (WNV), human polyomavirus 7 (HPyV7) and human parvovirus B19 (B19V) in thymoma or thymic hyperplasia. 29 , 30 , 31 The association of viruses with thymic epithelial tumors by these findings raises the possibility of the involvement of viruses in the development of thymoma.…”

Human thymus retrovirus. Is human thymus retrovirus a pathogenic virus for human autoimmune diseases?

“…The methods for the recovery of retrovirus particles were described elsewhere 30,31. Briefly, freshly isolated thymus cells-32 were cultured for 7 days together with B cells Most of retroviruses are considered to be endogenous, since they are induced in normal cells and since molecular hybridization studies have shown that their proviruses are integrated into the cell genome.…”