Detection of lymphocytes producing a human retrovirus associated with adult T-cell leukemia by syncytia induction assay.

Abstract

Recently 10 T-cell lines were established from patients with adult T-cell leukemia (ATL). During establishment of these cell lines, it was found that when T-cell lines expressing the ATL-associated retroviral antigen were cocultivated with 8C cat cells, multinucleated syncytia were formed. Retroviral antigen-negative T-cell lines did not induce syncytia. Peripheral blood lymphocytes obtained from ATL patients did not express the retroviral antigen before cultivation in vitro but became positive for the retroviral antigen after cultivation for a short period; these retroviral antigen-positive lymphocytes, but not retroviral antigen-negative lymphocytes, induced syncytia upon cocultivation with 8C cells. Peripheral blood lymphocytes isolated from patients with chronic lymphocytic leukemia of T-cell origin or Skzary syndrome or from normal adults and lymph node cells from a patient with immunoblastic lymphadenopathy-like T-cell lymphoma did not express the retroviral antigen even after cultivation in vitro and did not induce syncytia upon cocultivation with SC cells. Thus, there was complete agreement between the presence of the retroviral antigen in established T-cell lines or freshly isolated peripheral blood lymphocytes and their ability to induce syncytia. Syncytia formation was enhanced 5-to 20-fold by the presence of Polybrene and inhibited by addition of plasma of ATL patients to the cocultures. Syncytia were detected within 4 hr on cocultivation of 8C cells with the retroviral antigen-positive T-cells, indicating that most syncytia were formed by early polykaryocytosis. After cocultivation, a clone of 8C cells that harbored the AU virus genome and had syncytia-inducing activity was isolated. These findings indicate that the retrovirus associated with AU has syncytiainducing activity. Syncytia induction assay using 8C cells will be useful for detection and characterization of human retrovirus associated with T-cell malignancies.

Protein isoforms encoded by the pX region of human T-cell leukemia/lymphotropic virus type I.

“…In ATL, it appears that the majority of the leukemic cells do not express viral antigens (32,33) and viral mRNA (34). More recently, using the RT/PCR technique, we (20) and others (29) have shown that viral expression can be detected in the PBMCs of most ATL patients, although this particular technique does not allow discrimination between viral expression occurring in leukemic cells versus the infected circulating normal T cells.…”

HTLV-1 tropism and envelope receptor

“…(ii) Cell-to-cell fusion mediated by HTLV-1 Env. Fusion is generally measured by the formation of multinucleated giant syncytial cells (Hoshino et al, 1983;Hildreth et al, 1997;Tajima et al, 1997), or by an adaptation of an HIV Tat-based assay (Rocancourt et al, 1990) in which Env-receptor interactions are revealed by the transfer of HIV Tat molecules to indicator cells harboring a Tat-dependent marker gene (Denesvre et al, 1995). The latter appears more suited to directly evaluate receptor function, since several cell lines that are fully susceptible to HTLV-1 Env-mediated viral entry are resistant to syncytia formation (Kim et al, 2003).…”

Infection of human endothelial cells by human T-cell leukemia virus type I.

“…Moreover, viral pseudotypes bearing HTLV-I or HTLV-II envelope glycoproteins can penetrate a variety of mammalian cell lines (24). In several of these susceptible cells, syncytia were induced by cocultivation with HTLV-I-producing cells (25,26) and in a single human osteosarcoma cell line stable HTLV-I replication could be demonstrated (27).…”