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

Human T‐cell leukemia virus type 1 (HTLV‐1) is the etiologic agent for adult T‐cell leukemia and HTLV‐1‐associated myelopathy/tropical spastic paraparesis. Recently we infected newborn mice by inoculating HTLV‐1‐producing human cells, and found that T‐cells, B‐cells and granulocytes were infected in vivo. To understand the mechanism of viral‐cell interaction and the pathogenesis of HTLV‐1 using the mouse model, it is important to clarify the cellular tropism using a cell‐free HTLV‐1 transmission system. We employed a highly transmissible cell‐free HTLV‐1 produced by a feline kidney cell line, c77, and studied the susceptibility of 9 kinds of mouse cell lines, EL4, RLml, CTLL‐2, J774.1, DA‐1, Ba/F3, WEHI‐3, NIH3T3 and Bl, and two kinds of human cell lines, Molt‐4 and Hut78. HTLV‐1 proviral sequence was found by PCR in all 9 mouse cell lines as well as in 2 human cell lines and viral entry was blocked with sera from an HTLV‐1 carrier and an adult T‐cell leukemia patient. Unexpectedly, mouse cell lines EL4 and RLml and human cell lines Molt‐4 and Hut78 showed similar efficiency for viral entry. These results suggest a wide distribution of HTLV‐1 receptor in mouse cells.