Human T-cell lymphotropic virus type I (HTLV-I) is an etiological agent of
T-cell leukemia and HTLV-I-associated myelopathy/tropical spastic parapares
is. The virus is known to target: and transform preferentially CD4(+) cells
. The aim of this work was to investigate a transforming activity of HTLV-I
in non-lymphoid cell line permissive for its replication as well as to est
ablish a convenient model for studying the antiretroviral substances. For t
his purpose monolayer human osteosarcoma HOS cells were infected with HTLV-
I by co-cultivation with HTLV-I-producing rabbit: lymphoid Ra-1 cells. Cyto
genetic analysis of HTLV-I-infected NOS cell culture (RaHOS) confirmed the
human karyotype identical to that of the initial HOS cells. Integration of
HTLV-I provirus was detected by polymerase chain reaction (PCR) for HTLV-I
gag, env, fax and LTR sequences. Expression of viral antigens and HTLV-I re
plication in RaHOS cells were confirmed by immunofluorescence assay, RT-PCR
and syncytia inhibition assay. The features characteristic of malignant tr
ansformation of RaHOS cells developed in the following order: increasing pr
oliferative activity (after 18 passages), colony-forming ability (after 30
passages), appearance of the Focuses of multilayer cell growth (after 60 pa
ssages). All these features increased progressively throughout passage hist
ory of the cells. At the same time the initial NOS cells did not form colon
ies in soft agar and focuses of multilayer cell growth. Thus, RaHOS cells i
s the first characterized monolayer cell culture expressing HTLV-I in which
HTLV-I transforming activity is observed. This cell line could be a suitab
le model for studying the changes in expression of different cell genes upo
n HTLV-I infection as well as the effects of various anti-retroviral compou
nds.