Infection of peripheral blood mononuclear cells and cell lines by cell-free human T-cell lymphoma/leukemia virus type I

Abstract

Previous studies of in vitro infection by human T-cell lymphoma/leukemia virus type I (HTLV-I) have required cocultivation of target cells with HTLV-I cell lines or vesicular stomatitis virus pseudotypes containing HTLV-I envelope proteins. We report here the development of a cell-free infection assay for HTLV-I. Target cells were incubated with purified, DNase-treated HTLV-I virions for 4 h at 37°C. Target cell DNA was then analyzed for the presence of newly synthesized HTLV-I proviral DNA by the highly sensitive polymerase chain reaction. Using this assay system, we have been able to consistently detect in vitro infection of a variety of cellular targets by different HTLV-I isolates. Optimal infection required the presence of 10 ,ug of DEAEdextran per ml. The assay was dose dependent with respect to virus input. In general, the amount of proviral DNA detected correlated with the level of HTLV-I receptors present on the surface of the target cells, as measured by fluorochrome-labelled HTLV-I binding. Finally, the specificity of the assay was confirmed by demonstrating that the cell line, Llq, a somatic cell hybrid containing human chromosome 17q, to which the gene for the HTLV-I receptor has been mapped, was susceptible to infection by HTLV-I, while the parental mouse cell line from which it was derived, LMTK-, which lacks human chromosome 17q, was not.

Detection of neutralizing antibodies against human T‐cell leukemia virus type 1 using a cell‐free infection system and polymerase chain reaction

“…These findings indicated that c77 cells produced highly transmissible HTLV-1 and the infectivity of the c77 cell supernatant was estimated to be more than 3,000 times higher than that of the culture supernatant derived from MT-2, C91 /PL or HOS/PL cells. Fan et al (1992) have detected HTLV-I-specific bands when indicator cells are infected with highly concentrated HTLV-I produced by MT-2 cells. This method has not apparently been used for titrating neutralizing antibodies.…”

Cell‐free Entry of Human T‐Cell Leukemia Virus Type 1 to Mouse Cells

“…7) Furthermore, the somatic-cell hybrid cell line L1q, which contains human chromosome 17q, could be infected with HTLV-1, but the parental mouse fibroblast cell line, LMTK−, could not. 25) Thus, the receptor gene for HTLV-1 has been assigned to human chromosome 17q. 7,26,27) However, Sutton and Littman reported that HIV (HTLV-1) pseudotype virus could infect mouse fibroblast LMTK− cells at 4.5% efficiency and four other LMTK− cell lines which contained at least human chromosome 17q at 0.015-2.0% efficiency as compared to a human osteosarcoma cell line, HOS cells.…”

“…The possibilities include differences in the virus preparations, the target mouse cell lines and/or the sensitivity and specificity of the assay systems. The cell-free HTLV-1 used in earlier studies was mostly from MT-2 cells, 25,29,30) C91/PL cells 30) or HOS/PL cells. 31) The filtered virus in the culture fluids of C91/PL cells could infect human lymphocytes from cord blood and peripheral blood, and that of MT-2 cells could infect human lymphocytes from cord blood only, while that of C10/MJ could infect neither of them.…”

“…Mouse cell lines used previously are mostly fibroblasts, LMTK− and LMTK− derived mouse/human hybrid cells. 7,25) Cell adhesion molecules were considered to be co-receptors for HTLV-1 transmis-sion, based on syncytium formation assay. 37) We used various kinds of cells of mouse origin to show that the receptor or co-receptor of HTLV-1 is widely distributed in mouse cells.…”

Cell‐free Human T‐cell Leukemia Virus Type 1 Binds to, and Efficiently Enters Mouse Cells

“…Although Fan et al developed a sensitive HTLV-1 infection assay with cell-free HTLV-1 pro-duced from MT-2 cells, only low levels of viral DNA have been detected. 20) Haraguchi et al reported that the cell-free HTLV-1 produced from a feline kidney cell line, c77, is highly transmissible to human cells. The transmission of cell-free HTLV-1 produced from c77 cells was estimated to be more than 3000 times higher than that of HTLV-1 derived from MT-2, C91/PL or HOS/PL cells by PCR assay.…”