Infectivity of human T-lymphotropic virus type I to human nervous tissue cells in vitro

Infectivity of human T-lymphotropic virus type I (HTLV-I) to human nervous tissue cells was explored using co-cultivation with X-irradiated, HTLV-I-producing MT2 cells. Examined cells included normal cerebellar cells, brain tumor cells (astrocytoma, medulloblastoma, meningioma, hemangioblastoma, and schwannoma), and various cell lines (astrocytoma, ependymoma, oligodendroglioma, medulloblastoma, and neuroblastoma). Successful HTLV-I infection was confirmed immunohistochemically using monoclonal antibodies to HTLV-I p19, p24, and pX product. All cell lines and primary cultures from normal cerebellar tissues and brain tumors could be infected with HTLV-I. Double immunostaining showed that glial fibrillary acidic protein-, S-100 protein- or vimentin-positive cells were susceptible to infection. Neurofilament- or neuron-specific enolase-positive cells in medulloblastoma could also be infected. Reverse-transcriptase assay revealed the productive infection in U251-MG (astrocytoma) and KG-IC (oligodendroglioma) lines. Co-cultivated U251-MG cells formed syncytial polykaryons after serial passages, and polymerase chain reaction assay detected HTLV-I genome in U251-MG syncytial polykaryons and p19+ mononuclear cells. HTLV-I viral RNA was also detected in infected U251-MG cells by in situ hybridization. These data show that HTLV-I may have a wide spectrum of infectivity in human nervous tissues.