Analysis of the molecules involved in human T-cell leukaemia virus type 1 entry by a vesicular stomatitis virus pseudotype bearing its envelope glycoproteins

Cellular entry of human T-cell leukaemia virus type 1 (HTLV-1) was studied by a quantitative assay system using vesicular stomatitis virus (VSV) pseudotypes in which a recombinant VSV (VSVΔG*) containing the gene for green fluorescent protein instead of the VSV G protein gene was complemented with viral envelope glycoproteins in trans. Most of the cell lines tested showed susceptibility to VSVΔG* complemented with either HTLV-1 envelope glycoproteins (VSVΔG*-Env) or VSV G protein (VSVΔG*-G), but not to VSVΔG* alone, indicating that cell-free HTLV-1 could infect many cell types from several species. High concentration pronase treatment of cells reduced their susceptibility to VSVΔG*-Env, while trypsin treatment, apparently, did not. Treatment of the cells with sodium periodate, heparinase, heparitinase, phospholipase A2 or phospholipase C reduced the susceptibility of cells to VSVΔG*-Env, but not to VSVΔG* complemented with measles virus (Edmonston strain) H and F proteins (VSVΔG*-EdHF), which was used as a control. Purified phosphatidylcholine also inhibited the infectivity of VSVΔG*-Env, but not VSVΔG*-G. These findings indicated that, in addition to cell surface proteins, glycosaminoglycans and phospholipids play an important role in the process of cell-free HTLV-1 entry.